Pole piece and manufacturing method thereof, secondary battery and electric device

Abstract

The invention discloses a pole piece and a manufacturing method thereof, a secondary battery and an electric device, the pole piece comprises a current collector, an active material layer, a conductive piece and an insulating layer, the current collector comprises a first part and a second part which are adjacently arranged along a first direction; the active material layer is arranged on the first part and comprises a first covering part and a second covering part which are sequentially arranged in the first direction, and the thickness of the second covering part is smaller than that of the first covering part in the thickness direction of the current collector; the conductive piece is connected to the second part; the insulating layer is arranged on the second part, at least part of the conductive part is away from the surface of the current collector, and at least part of the second covering part is away from the surface of the current collector. Compared with an existing pole piece, the pole piece adopting the structure can reduce the risk that the thickness of the edge of the active material layer is relatively large due to the fact that the active material layer is coated with the insulating layer in the manufacturing process, and is beneficial to improving the energy density of the secondary battery.

Description

Technical Field

[0001] The present invention relates to the field of secondary batteries, and in particular to an electrode sheet and its manufacturing method, a secondary battery, and an electrical device. Background Technology

[0002] A rechargeable battery is a device that can be repeatedly charged and discharged. It typically consists of a casing, an electrode assembly housed within the casing, and tabs connected to the electrode assembly. The tabs can be connected to electrical devices. The electrode assembly comprises electrodes of different polarities and a separator. The separator is disposed between two adjacent electrodes of different polarities. Each electrode includes a current collector and an active material layer disposed on the surface of the current collector. The current collector can be a conventional current collector or a composite current collector.

[0003] Currently, the space available for installing secondary batteries in electrical equipment is relatively limited. Within the given space, the higher the capacity of the secondary battery, the better it is for the electrical device to continue operating. Therefore, it is becoming increasingly important to improve the energy density of secondary batteries. Summary of the Invention

[0004] To address the aforementioned technical problems, embodiments of this application provide an electrode sheet, a secondary battery, and an electrical device that can improve energy density in the thickness direction.

[0005] The technical problem solved by the embodiments of this application is addressed by the following technical solution: An electrode includes a current collector, an active material layer, a conductive element, and an insulating layer. The current collector includes a first portion and a second portion disposed adjacent to each other along a first direction. The active material layer is disposed in the first portion and includes a first covering portion and a second covering portion disposed sequentially along the first direction. Along the thickness direction of the current collector, the thickness of the second covering portion is less than the thickness of the first covering portion. The conductive element is connected to the second portion. The insulating layer is disposed in the second portion, on the surface of at least a portion of the conductive element away from the current collector, and on the surface of at least a portion of the second covering portion away from the current collector. The first direction is perpendicular to the thickness direction of the current collector.

[0006] Thus, when the insulating layer covers the active material layer, the space gained by the thickness difference between the second and first covering portions of the active material layer can be utilized to reduce the thickness at the overlap between the insulating and active material layers. This reduces the risk of the insulating layer being too thick at the overlap due to coating the edge of the active material layer, which is beneficial for improving the energy density of the secondary battery. Simultaneously, the insulating layer reduces the risk of burrs on conductive components and exposed burrs in the second part, lowering the risk of short circuits caused by burrs piercing the separator in secondary batteries made with this electrode, thus improving the safety of the secondary battery.

[0007] Optionally, along the thickness direction of the current collector, the difference between the thickness of the first cover and the thickness of the second cover is t1, satisfying 10μm < t1 ≤ 50μm. When t1 < 10μm, there is a risk that the insulation layer covering the second cover will be too thick. When t1 > 50μm, it will affect the coating of the insulation layer, resulting in less support force on the conductive element, making it prone to sagging. During the manufacturing process, the area where the conductive element is located is prone to wrinkling and folding when the electrode is wound or unwound. When 10μm < t1 ≤ 50μm, the thickness of the electrode in the second cover is more suitable, reducing the risk of wrinkling and folding during the manufacturing process and reducing the risk of loss of active material leading to a decrease in the capacity of the secondary battery.

[0008] Optionally, along the first direction, the width of the second cover is d1, satisfying 1mm < d1 ≤ 2mm. Thus, the width of the second cover in the first direction is suitable. Because the area where the second cover of the electrode is located is relatively thin, a width greater than 2mm would increase the risk of poor contact due to a larger gap between the positive and negative electrodes in the thickness direction of the current collector. Simultaneously, a width greater than 1mm in the first direction reduces the risk of the insulating layer failing to cover the second cover due to deviations in the coating of active material on both sides of the electrode, thus improving the stability of the secondary battery.

[0009] Optionally, 1mm < d1 ≤ 1.5mm. This further reduces the risk of poor contact due to a large gap between the positive and negative electrodes in the secondary battery made with this electrode, and also reduces the risk that the insulating layer may fail to cover the second covering part due to deviations in the coating of active materials on both sides of the electrode.

[0010] Understandably, the area of ​​the insulating layer coating is fixed in advance. When the electrode is flipped between the front and back sides to coat the active material, it is difficult to ensure that the active material coated on the front and back sides is aligned. Therefore, it is necessary to increase the size of the second cover, that is, the size of the second cover is greater than 1 mm, in order to ensure that the second cover is coated with insulating material during processing and manufacturing.

[0011] Optionally, the insulating layer includes a first insulating portion overlapping the first covering portion. Along the first direction, the width of the first insulating portion is d2, satisfying 0.1mm < d2 ≤ 1.6mm. When d2 < 0.1mm, the insulating material forming the first insulating portion cannot be coated onto the second covering portion. When d2 > 1.6mm, the first insulating portion covers too much of the second covering portion, preventing the active material beneath the first insulating layer from functioning and affecting the capacity of the secondary battery. Therefore, when the first insulating portion d2 satisfies 0.1mm < d2 ≤ 1.6mm, the area where the first insulating portion covers the second covering portion is more suitable, reducing the risk of affecting the energy density of the secondary battery due to excessive active material coverage by the first insulating portion, and thus improving the capacity of the secondary battery.

[0012] Optionally, 0.1mm < d2 ≤ 1mm. This ensures that while the insulating material is coated with the second covering portion, the first insulating portion does not excessively cover the second covering portion.

[0013] Optionally, the insulating layer includes a first insulating portion, a second insulating portion, and a third insulating portion, which are sequentially arranged along a first direction. The first insulating portion overlaps with the first covering portion, and the third insulating portion covers the surface of the conductive element away from the current collector. Along the thickness direction of the current collector, the thickness of the second insulating portion is t2, satisfying 10μm < t2 ≤ 50μm. When t2 ≤ 10μm, the insulating layer cannot completely cover the area where the conductive element connects to the second part during electrode manufacturing, which may lead to an internal short circuit when the secondary battery is manufactured. When t2 > 50μm, the thickness of the second insulating portion is greater than the sum of the thicknesses of the first part and the active material layer, which may cause the head of the secondary battery to be excessively thick. Thus, when 10μm < t2 ≤ 50μm, the risk of excessive thickness in the area where the second part is located in the electrode is reduced, which helps to reduce the risk of edge bulging during electrode winding.

[0014] And / or, along the first direction, the width of the insulating layer is d3, satisfying 1.2mm < d3 < 5mm. When d3 is less than 1.2mm, when using this electrode to make an electrode assembly, the insulating layer cannot completely cover the size difference between the positive and negative electrode plates. The negative electrode plate may extend beyond the insulating layer and contact the tab of the positive electrode, potentially leading to an internal short circuit. When d3 is greater than 5mm, the insulating layer will affect the position of the tab welding during subsequent secondary battery fabrication, requiring an extension of the conductive component's width to accommodate tab welding, resulting in space loss and affecting energy density. Therefore, when the width d3 of the insulating layer is within 1.2mm < d3 < 5mm, it is beneficial to improve the energy density and safety of the secondary battery made using this electrode.

[0015] Optionally, the conductive component and the second part are connected by roll welding to form a weld mark. The dimension of the weld mark in the first direction is d4, satisfying 1mm < d4 < 5mm. When d4 < 1mm, the yield rate and weld strength of the roll welding process will decrease, which is not conducive to the connection between the conductive component and the second part. When d4 > 5mm, it will affect the welding position between the electrode and the conductive component when manufacturing the secondary battery, requiring an increase in the length of the conductive component to achieve the connection between the conductive component and the electrode, thus resulting in space loss. Therefore, when 1mm < d4 < 5mm, it is beneficial to improve the connection strength between the conductive component and the second part, and at the same time, it is beneficial to have a suitable welding position between the conductive component and the second part, which can improve the energy density when manufacturing the electrode of the secondary battery.

[0016] Optionally, the electrode also includes a base coating layer disposed between the first portion and the active material layer along the thickness direction of the current collector. The base coating layer can enhance the adhesion between the current collector and the active material of the active material layer, reducing the risk of the active material of the active material layer detaching from the current collector.

[0017] Optionally, the active material layer includes a first active material layer and a second active material layer, and the primer layer includes a first primer layer and a second primer layer. The current collector includes a base layer, a first conductive layer, and a second conductive layer. The first conductive layer is disposed on one surface of the base layer, and the second conductive layer is disposed on the other surface of the base layer. The first conductive layer has the first primer layer and the first active material layer sequentially disposed on its end face away from the base layer, and the second conductive layer has the second primer layer and the second active material layer sequentially disposed on its end face away from the base layer. Thus, the current collector is a composite current collector. The reduced thickness of the first and second conductive layers on both sides of the base layer helps reduce the generation of metal burrs when the current collector is subjected to mechanical damage from external impact, thereby reducing the risk of short circuits.

[0018] Optionally, the conductive element includes a first conductive element and a second conductive element, wherein the first conductive element is connected to a first conductive layer and the second conductive element is connected to a second conductive layer.

[0019] The technical solutions adopted in this application to solve its technical problems are as follows: A secondary battery comprising the aforementioned electrode plates.

[0020] The technical solutions adopted in this application to solve its technical problems are as follows: An electrical device includes the aforementioned secondary battery.

[0021] The technical solutions adopted in this application to solve its technical problems are as follows: A method for manufacturing an electrode sheet, used to prepare the aforementioned electrode sheet. The manufacturing method includes: providing a current collector and a conductive element, the current collector including a coated area and an uncoated area; coating an active material onto the coated area of ​​the current collector to form an active material layer, the active material layer including a first cover portion and a second cover portion of unequal thickness; conductively connecting the conductive element to the uncoated area of ​​the current collector; and coating an insulating material onto a second portion, at least a portion of the conductive element's surface away from the current collector, and at least a portion of the second cover portion's surface away from the current collector to form an insulating layer.

[0022] Using the above manufacturing method, the active material is first coated on the coated area of ​​the current collector, and then the conductive element is connected to the uncoated area of ​​the current collector. After that, an insulating material is coated to form an insulating layer. Compared with the previous method of manufacturing electrode sheets by simultaneously coating the insulating material and the active material layer and then connecting the conductive element to the uncoated area, the connection area between the conductive element and the uncoated area and the insulating material forming the insulating layer can overlap. This reduces the risk of damaging the insulating layer due to the conductive element being connected to the uncoated area. It also helps to reduce the thickness of the electrode sheet in the uncoated area, which is beneficial to improving the energy density.

[0023] Alternatively, the conductive element can be joined to the uncoated area of ​​the current collector by roll welding.

[0024] The beneficial effects of the embodiments of this application are as follows: The electrode provided in the embodiments of this application includes a current collector, an active material layer, a conductive element, and an insulating layer. The current collector includes a first portion and a second portion disposed adjacent to each other along a first direction. The active material layer is disposed in the first portion, and the active material layer includes a first covering portion and a second covering portion disposed sequentially along the first direction. Along the thickness direction of the current collector, the thickness of the second covering portion is less than the thickness of the first covering portion. The conductive element is connected to the second portion. The insulating layer is disposed in the second portion, on the surface of at least a portion of the conductive element away from the current collector, and on the surface of at least a portion of the second covering portion away from the current collector. Compared with existing electrode sheets, the electrode sheet using the above structure can reduce the risk of a thicker edge of the active material layer caused by the insulating layer being coated on the active material layer during the manufacturing process, which is beneficial to improving the energy density of the secondary battery. Attached Figure Description

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

[0026] Figure 1 This is a plan view of the electrode sheet according to one embodiment of this application; Figure 2 yes Figure 1 A schematic diagram after being cut by the section line AA; Figure 3 This is a cross-sectional view of the current collector; Figure 4 yes Figure 2 A schematic diagram of the middle section structure; Figure 5 This is a structural block diagram of a secondary battery according to another embodiment of this application; Figure 6 This is a cross-sectional view of the electrode assembly; Figure 7 This is another cross-sectional view of the electrode assembly; Figure 8 This is a flowchart of a method for manufacturing an electrode sheet according to another embodiment of this application; In the figure: 1. Electrode; 2. Current collector; 3. Active material layer; 4. Conductive component; 5. Insulating layer; 6. Base coating; 21. First part; 22. Second part; 31. First covering part; 32. Second covering part; 201. Base layer; 202. First conductive layer; 203. Second conductive layer; 301. First active substance layer; 302. Second active substance layer; 41. First conductive component; 42. Second conductive component; 401. Solder stamp; 51. First insulating part; 52. Second insulating part; 53. Third insulating part; 501. First insulating layer; 502. Second insulating layer; 61. First primer coating; 62. Second primer coating; 100. Secondary battery; 110. Housing; 120. Electrode assembly; 130. Tab. Detailed Implementation

[0027] To facilitate understanding of this application, a more detailed description is provided below with reference to the accompanying drawings and specific embodiments. It should be noted that when an element is described as "fixed to" another element, it can be directly on the other element, or one or more intermediate elements may exist between them. When an element is described as "connected" to another element, it can be directly connected to the other element, or one or more intermediate elements may exist between them. The terms "upper," "lower," "inner," "outer," "vertical," "horizontal," etc., used in this specification indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0028] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of the application. The term "and / or" as used in this specification includes any and all combinations of one or more of the associated listed items.

[0029] Furthermore, the technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0030] like Figure 1 As shown, in one embodiment of this application, the electrode 1 includes a current collector 2, an active material layer 3, a conductive element 4, and an insulating layer 5. The active material layer 3 is disposed on two opposite surfaces of the current collector 2, the conductive element 4 is connected to the current collector 2, and the insulating layer 5 covers the conductive element 4, part of the current collector 2, and the edge portion of the active material layer 3.

[0031] Understandably, during the manufacturing process of electrode 1, coating with insulating layer 5 can reduce the risk of burrs on the surface of conductive component 4 and burrs in areas of current collector 2 that are not covered by active material layer 3 being exposed. This reduces the risk of short circuits between electrodes 1 of different polarities due to the presence of burrs during the preparation of secondary batteries. Therefore, setting insulating layer 5 can help improve the safety performance of secondary batteries.

[0032] The inventors of this application have discovered that in the current manufacturing process of the electrode 1 of a secondary battery, the coating of active material to form an active material layer 3 and the coating of insulating material to form an insulating layer 5 are carried out simultaneously. The insulating layer 5 partially covers the active material layer 3, and the thickness of the area where the insulating layer 5 covers the active material layer 3 is relatively thicker than other areas of the electrode 1. When using this type of electrode 1 to prepare an electrode assembly, the area of ​​the electrode 1 that is relatively thick will be generally thicker than other areas of the electrode assembly, which will affect the energy density of the secondary battery.

[0033] To address the issue of excessive thickness at the junction of the insulating layer 5 and the active material layer 3 in electrode 1, the inventors of this application have discovered that the edge portion of the active material layer can be thinned to improve the excessive thickness at the electrode edge. The specific solution is as follows: like Figure 1 and Figure 2As shown, the electrode 1 provided in this embodiment includes a current collector 2, an active material layer 3, a conductive element 4, and an insulating layer 5. The current collector 2 includes a first portion 21 and a second portion 22 disposed adjacent to each other along a first direction X. The first portion 21 is used to deposit the active material layer 3, and the second portion 22 is used to connect with the conductive element 4. That is, the first portion 21 is the part of the current collector 2 that needs to be coated with the active material, and the second portion 22 is the part of the current collector 2 that does not need to be coated with the active material. Figure 2 As shown, the active material layer 3 includes a first covering portion 31 and a second covering portion 32 sequentially disposed along the first direction X. Along the thickness direction Y of the current collector 2, the thickness of the second covering portion 32 is less than the thickness of the first covering portion 31; that is, the thickness of the active material layer 3 disposed on the first portion 21 is not equal along the thickness direction Y of the current collector 2. An insulating layer 5 is disposed on the second portion, at least a portion of the conductive element on the surface away from the current collector, and at least a portion of the second covering portion on the surface away from the current collector.

[0034] Thus, when the insulating layer 5 covers the active material layer 3, the space obtained by the thickness difference between the second covering portion 32 and the first covering portion 31 in the active material layer 3 can be utilized to reduce the thickness at the overlap between the insulating layer 5 and the active material layer 3. This reduces the risk of the overlapping portion being too thick due to the insulating layer 5 being coated to the edge of the active material layer 3, which is beneficial for improving the energy density of the secondary battery. At the same time, the insulating layer 5 can reduce the risk of burrs on the conductive component 4 and the second portion 22 being exposed, reducing the risk of short circuits caused by burrs piercing the separator in the secondary battery made with this electrode 1, which is beneficial for improving the safety of the secondary battery.

[0035] In some embodiments, the current collector 2 can be made directly of a conductive metal, such as copper foil or aluminum foil, or it can be a composite current collector with a three-layer sandwich structure, depending on the specific requirements. In this embodiment, as... Figure 3 As shown, the current collector 2 adopts a composite current collector structure, that is, the current collector 2 includes a base layer 201, a first conductive layer 202 and a second conductive layer 203. The first conductive layer 202 is disposed on one surface of the base layer 201, and the second conductive layer 203 is disposed on the other surface of the base layer 201. Both the first conductive layer 202 and the second conductive layer 203 have an active material layer 3 disposed on the end face away from the base layer 201. The thickness direction Y of the current collector 2 refers to the direction in which the first conductive layer 202, the base layer 201 and the second conductive layer 203 are stacked.

[0036] The base layer 201 is made of an insulating polymer material, possessing high structural strength and low density and mass, which reduces the thickness and weight of the current collector 2. The first conductive layer 202 and the second conductive layer 203 are made of metallic materials. Compared to a conventionally made metallic current collector 2, the thickness of the first conductive layer 202 and the second conductive layer 203 disposed on both sides of the base layer 201 is reduced. When the current collector 2 is subjected to mechanical damage from external impact, this helps to reduce the generation of metal burrs, thereby reducing the risk of short circuits.

[0037] In some embodiments, the polymeric material includes one or more of polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), polyimide (PI), polyetherketone (PEK), and polyphenylene sulfide (PPS).

[0038] In some embodiments, the active material layer 3 is formed by coating an active material onto the first portion 21 of the current collector 2 and then rolling and drying it. Depending on the polarity of the electrode 1 to be prepared, the active material coated on the electrode 1 varies. For example, when the electrode 1 is a positive electrode, the active material includes lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium nickel oxide, lithium nickel cobalt manganese oxide, etc.; when the electrode 1 is a negative electrode, the active material includes graphite, lithium titanate, or carbon materials with a graphite-like structure, etc. In this embodiment, such as... Figure 2 As shown, the active material layer 3 includes a first active material layer 301 and a second active material layer 302. The first active material layer 301 is disposed on the first conductive layer 202, and the second active material layer 302 is disposed on the second conductive layer 203. Both the first active material layer 301 and the second active material layer 302 include a first covering portion 31 and a second covering portion 32. The second covering portions 32 of both the first active material layer 301 and the second active material layer 302 are located on the same side of the current collector 2.

[0039] In some embodiments, the conductive element 4 can be made of one or more materials selected from aluminum, copper, nickel, silver, gold, iron, etc., as long as it can conduct electricity; the specific material can be chosen according to needs. In this embodiment, the conductive element 4 is aluminum foil. Figure 2 As shown, the conductive element 4 includes a first conductive element 41 and a second conductive element 42. The first conductive element 41 is connected to the first conductive layer 202, and the second conductive element 42 is connected to the second conductive layer 203. Thus, the connection with the electrode 1 can be achieved by connecting the first conductive layer 202 and the second conductive layer 203 respectively.

[0040] In some embodiments, the thicknesses of the first conductive element 41 and the second conductive element 42 along the thickness direction Y of the current collector 2 range from 8 μm to 20 μm. The thicknesses of the first conductive element 41 and the second conductive element 42 may be the same or different, depending on the specific requirements.

[0041] In some embodiments, viewed along the thickness direction Y of the current collector 2, in the first direction X, the conductive element 4 extends beyond the edge of the insulating layer 5; that is, part of the conductive element 4 is connected to the current collector 2, while another part extends beyond both the insulating layer 5 and the edge of the current collector 2. This facilitates external connection to the conductive element 4 to achieve electrical connection with the current collector 2. Along the first direction X, the dimensions of the first conductive element 41 and the second conductive element 42 may be the same or different, depending on the specific requirements.

[0042] In some embodiments, such as Figure 4 As shown, along the thickness direction Y of the current collector 2, the thickness of the first covering part 31 is T1, and the thickness of the second covering part 32 is T2. The thickness T1 of the first covering part 31 is greater than the thickness T2 of the second covering part 32. The difference between the thickness T1 of the first covering part 31 and the thickness T2 of the second covering part 32 is t1μm, which satisfies 10μm<t1≤50μm.

[0043] When t1 < 10 μm, there is a risk that the insulating layer 5 will be too thick when covering the second covering portion 32. When t1 > 50 μm, it will affect the coating of the insulating layer 5. The less support force the conductive element 4 receives, the more prone the conductive element 4 is to sagging. During the manufacturing process, when the electrode is wound or unwound, the area where the conductive element 4 is located is prone to wrinkling and folding. Thus, the thickness of the electrode 1 in the second covering portion 32 is more suitable, reducing the risk of wrinkling and folding of the electrode 1 during the manufacturing process, and reducing the risk of loss of active material and reduction of secondary battery capacity.

[0044] In some embodiments, such as Figure 4 As shown, along the first direction X, the width of the second covering portion 32 is d1, satisfying 1mm < d1 ≤ 2mm. Thus, the width of the second covering portion 32 in the first direction X is suitable, reducing the risk of poor contact in the secondary battery due to a large gap between the positive and negative electrode plates 1 in the thickness direction Y of the current collector 2 caused by the thinness of the area where the second covering portion 32 of the electrode plate 1 is located. Simultaneously, the width of the second covering portion 32 in the first direction X is greater than 1mm, reducing the risk that the insulating layer 5 may fail to cover the second covering portion 32 due to deviations in the double-sided coating of active material on the electrode plate 1, thus improving the stability of the secondary battery.

[0045] In some embodiments, 1mm < d1 ≤ 1.5mm. This further reduces the risk of poor contact due to a large gap between the positive and negative electrodes in the secondary battery made using this electrode, and also reduces the risk that the insulating layer 5 may fail to cover the second cover portion 32 due to deviations in the coating of active material on both sides of the electrode 1.

[0046] Understandably, the coating range of the insulating material forming the insulating layer 5 is fixed in advance. When the electrode 1 is flipped between the front and back sides to coat the active material, it is difficult to ensure that the active material layer coated on the front side and the active material layer coated on the back side are aligned. That is, there may be a deviation between the boundary lines of the active material layers on the front and back sides of the electrode 1. Therefore, it is necessary to increase the size of the second covering part 32, that is, the size of the second covering part 32 is greater than 1 mm, in order to ensure that the insulating material forming the insulating layer 5 is coated on the second covering part 32 during processing and manufacturing.

[0047] In some embodiments, the insulating layer 5 may be made of an insulating material including inorganic ceramics, non-conductive organic polymer layers, etc. Along the first direction X, the insulating layer 5 sequentially includes a first insulating portion 51, a second insulating portion 52, and a third insulating portion 53. The first insulating portion 51 covers the first covering portion 31, the second insulating portion 52 covers a portion of the second portion 22, and the third insulating portion 53 covers a portion of the conductive element 4 and a portion of the second portion 22, such as... Figure 2 As shown, the thickness of the second insulating portion 52 is greater than the thickness of the first insulating portion 51 and the third insulating portion 53.

[0048] In some embodiments, such as Figure 2 As shown, along the first direction X, the width of the first insulating portion 51 is d2, satisfying 0.1mm < d2 ≤ 1.6mm. When d2 < 0.1mm, the first insulating portion 51 cannot be coated with the second covering portion 32. When d2 > 1.6mm, the first insulating portion 51 covers too much of the second covering portion 32, preventing the active material below the first insulating layer 51 from functioning and affecting the capacity of the secondary battery. Therefore, when the first insulating portion d2 satisfies 0.1mm < d2 ≤ 1.6mm, the area where the first insulating portion 51 covers the second covering portion 32 is more suitable, reducing the risk of affecting the energy density of the secondary battery due to the first insulating portion 51 covering too much active material, and thus improving the capacity of the secondary battery.

[0049] In some embodiments, 0.1mm < d2 ≤ 1mm. This ensures that while the insulating material is coated onto the second cover portion 32, the first insulating portion 51 does not cover too much of the second cover portion 32.

[0050] In some embodiments, such as Figure 2 As shown, along the first direction X, the width of the insulating layer 5 is d3, which satisfies 1.2mm < d3 < 5mm.

[0051] When d3 is less than 1.2 mm, when this electrode 1 is used to make the electrode assembly of a secondary battery, the insulating layer 5 cannot completely cover the size difference between the positive and negative electrodes in the electrode assembly. The negative electrode may extend beyond the insulating layer 5 and contact the tab of the positive electrode, potentially leading to an internal short circuit. When d3 is greater than 5 mm, the insulating layer 5 will affect the position of the tab welding during subsequent secondary battery fabrication, requiring an extension of the conductive component's width to accommodate the tab welding, resulting in space loss and affecting energy density. Therefore, when the width d3 of the insulating layer is between 1.2 mm and d3 < 5 mm, it is beneficial to improve the energy density and safety of the secondary battery made using this electrode.

[0052] In some embodiments, along the thickness direction Y of the current collector 2, the thickness of the insulating layer 5 is t2, which is the width of the second insulating portion 52, satisfying 10μm<t2≤50μm.

[0053] When t2 ≤ 10 μm, the insulating layer 5 cannot completely cover the area where the conductive element 4 connects to the second part 22 during electrode manufacturing, which poses a risk of internal short circuit when the secondary battery is manufactured. When t2 > 50 μm, the thickness of the second insulating part 52 is greater than the sum of the thicknesses of the first part 21 and the active material layer 3, which poses a risk of the secondary battery head being too thick. Therefore, when 10 μm < t2 ≤ 50 μm, the risk of excessive thickness in the area where the second part 22 is located in the electrode 1 is reduced, which helps to reduce the risk of edge bulging when the electrode 1 is wound up.

[0054] In some embodiments, such as Figure 2 As shown, there are two insulating layers 5: a first insulating layer 501 and a second insulating layer 502. Viewed along the thickness direction Y of the current collector 2, the first insulating layer 501 covers one side of the first conductive element 41, the second covering portion 32 of the first active material layer 301, and the second portion 22. The second insulating layer 502 covers the other side of the second conductive element 42, the second covering portion 32 of the second active material layer 302, and the second portion 22. It is understood that the thicknesses of the first insulating layer 501 and the second insulating layer 502 can be the same or different, depending on the specific requirements.

[0055] In some embodiments, such as Figure 2 As shown, the conductive component 4 and the second part 22 are connected by roll welding to form a solder mark 401. The dimension of the solder mark 401 in the first direction X is d4, which satisfies 1mm < d4 < 5mm.

[0056] When d4 < 1 mm, the yield rate and weld strength of the roll welding process will decrease, which is detrimental to the connection between the conductive component 4 and the second part 22. When d4 > 5 mm, it will affect the welding position between the electrode tab and the conductive component 4 during the fabrication of the secondary battery, requiring an increase in the length of the conductive component 4 to achieve the connection between the conductive component 4 and the electrode tab, thus resulting in space loss. Therefore, when 1 mm < d4 < 5 mm, it is beneficial to improve the connection strength between the conductive component 4 and the second part 22, and at the same time, it is beneficial to have a suitable welding position between the conductive component 4 and the second part 22, which can improve the energy density when making the electrode sheet of the secondary battery.

[0057] In some embodiments, the thickness of the solder mark 401 along the thickness direction Y of the current collector 2 ranges from 20 μm to 50 μm. This facilitates a reliable weld between the conductive element 4 and the second portion 22, reduces the risk of poor welding due to the small size of the solder mark 401, and improves the stability of the secondary battery. When the thickness of the solder mark 401 is less than 20 μm, the thickness of the conductive element 4 and the current collector 2 themselves limits the welding process, which can lead to over-welding and easy detachment of the conductive element. When the thickness of the solder mark 401 is greater than 50 μm, the sum of the thicknesses of the insulating layer 5 and the solder mark 401 may exceed the thickness of the active material layer 3 on the current collector 2, posing a risk that the secondary battery made from this electrode will have a thicker head.

[0058] In some embodiments, such as Figure 2 As shown, the electrode 1 also includes a base coating 6. Along the thickness direction Y of the current collector 2, the base coating 6 is disposed between the first portion 21 and the active material layer 3. The base coating 6 can enhance the adhesion between the current collector 2 and the active material of the active material layer 3, reducing the risk of the active material of the active material layer 3 falling off the current collector 2. In this embodiment, the base coating 6 includes a first base coating 61 and a second base coating 62. The first base coating 61 is disposed between the first conductive layer 202 and the first active material layer 301, and the second base coating 62 is disposed between the second conductive layer 203 and the second active material layer 302.

[0059] In some embodiments, along the first direction X, the distance between the first base coating 61 and the first conductive element 41 is 0~0.5mm, and the distance between the first base coating 61 and the solder mark 401 is 0~1mm. Similarly, along the first direction X, the distance between the second base coating 62 and the second conductive element 42 is 0~0.5mm, and the distance between the second base coating 62 and the solder mark 401 is 0~1mm.

[0060] The electrode 1 provided in this embodiment includes a current collector 2, an active material layer 3, a conductive element 4, and an insulating layer 5. The current collector 2 includes a first portion 21 and a second portion 22 disposed adjacent to each other along a first direction X. The active material layer 3 is disposed in the first portion 21, and the active material layer 3 includes a first covering portion 31 and a second covering portion 32 disposed sequentially along the first direction X. Along the thickness direction Y of the current collector 2, the thickness of the second covering portion 32 is less than the thickness of the first covering portion 31. The conductive element 4 is connected to the second portion 22. The insulating layer 5 covers the surface of the second portion 22, at least a portion of the conductive element 4, and at least a portion of the second covering portion 32 away from the current collector 2. Compared with the existing electrode 1, the electrode 1 with the above structure can reduce the risk of the active material layer 3 being too thick at the edge due to the insulating layer 5 being coated on the active material layer 3 during the manufacturing process, which is beneficial to improving the energy density of the secondary battery.

[0061] Table 1 below shows the experiments conducted on the negative electrode 1 in the electrode assembly of a secondary battery using the electrode 1 with the above-described structure. The experimental temperature was room temperature (45°C), and the number of experimental samples was 1000. The energy density, defect rate, and insulation coating efficiency of secondary batteries with different thickness differences and different widths of the second cover 32 between the first cover 31 and the second cover 32 were measured.

[0062] The defect rate refers to the percentage of secondary batteries with collapsed heads when subjected to drop tests at the same height. The insulation coating quality rate refers to the percentage of batteries with excellent insulation coating performance. Dimensional deviations in the insulation coating, as well as excessively thin or thick insulation layers, will affect the insulation coating quality rate.

[0063] Table 1. Effects of different thickness differences t1 and different widths d1 on secondary batteries.

[0064] In Table 1 above, the size d1=0mm of the second cover of the secondary battery in the comparative example means that the active material layer of the inner electrode of the secondary battery does not have a second cover, and the thickness difference t1=25μm means that when there is no second cover, the thickness difference t1 is the thickness of the active material layer, which is 25μm.

[0065] As can be seen from Examples 1-5 in Table 1 above, when the thickness difference t1 between the thickness T1 of the first covering part 31 and the thickness T2 of the second covering part 32 remains equal, the width d1 of the second covering part 32 along the first direction X has an impact on the energy density and cycle number of the secondary battery.

[0066] Furthermore, a comparison between Embodiment 4 and Embodiment 5 reveals that when the width d1 of the second covering portion 32 is within the range of 1mm≤d1≤2mm, the coating efficiency of the insulating layer is relatively high, which is beneficial to improving the preparation of the electrode sheet and the defect rate of the secondary battery is relatively low. This is because when the width d1 of the second covering portion 32 satisfies the above relationship, in the thickness direction of the secondary battery, when the positive electrode sheet 1 and the negative electrode sheet 1 of the secondary battery are stacked, the two types of electrode sheets 1 can be tightly attached in the area where the second covering portion 32 is located, which reduces the risk of the area where the second covering portion 32 is located in the secondary battery when it is dropped, and improves the stability of the secondary battery.

[0067] As can be seen from Examples 6-12 in Table 1 above, when the width of the second cover portion 32 is the same, and the thickness difference t1 between the thickness T1 of the first cover portion 31 and the thickness T2 of the second cover portion 32 along the thickness direction Y of the current collector 2 satisfies 10μm≤t1≤50μm, the energy density ED of the secondary battery is within a good range. This is because during the manufacturing process, the thickness of the electrode 1 in the second cover portion 32 is more suitable, reducing the risk of wrinkling or folding of the electrode 1 during winding or unwinding, and reducing the risk of capacity reduction due to loss of active material.

[0068] Table 2 below shows the effect of the width d2 of the first insulating part on the energy density of the secondary battery when different values ​​are taken, as well as the process yield during the processing. The process yield refers to the excellent rate when the electrode is coated with insulating material.

[0069] Table 2. The effect of the width d2 of the first insulating part on the secondary battery when different values ​​are taken.

[0070] As can be seen from Examples 1-7 in Table 2 above, when the width d2 of the first insulating part 51 exceeds 1 mm, the process yield gradually decreases. Furthermore, when 0.1 mm < d2 ≤ 1.6 mm, the process yield is relatively high, which is beneficial for coating insulating materials during the fabrication of secondary batteries.

[0071] like Figure 5 As shown, another embodiment of this application provides a secondary battery 100, including a housing 110, an electrode assembly 120, and tabs 130. The electrode assembly 120 is housed within the housing 110, and the tabs 130 are connected to the electrode assembly 120. The electrode assembly 120 includes a positive electrode 121, a negative electrode 122, and a separator 123. The positive electrode 121 and the negative electrode 122 have opposite polarities, and the separator 123 is disposed between the positive electrode 121 and the negative electrode 122. In this embodiment, the tabs 130 are connected to the conductive element 4 of the positive electrode 121 or the negative electrode 122.

[0072] In some embodiments, the electrode assembly 120 may be a wound structure or a stacked structure. When the electrode assembly 120 adopts a wound structure, such as Figure 6 As shown, the positive electrode 121, the separator 123, and the negative electrode 122 are stacked sequentially and then wound. When the electrode assembly 120 adopts a stacked structure, as shown... Figure 7 As shown, there are multiple positive electrode plates 121, multiple negative electrode plates 122 and multiple separators 123. The multiple positive electrode plates 121, multiple separators 123 and multiple negative electrode plates 122 are stacked in one direction, and an insulating separator 123 is provided between adjacent positive electrode plates 121 and negative electrode plates 122.

[0073] It is understandable that either the positive electrode 121 or the negative electrode 122 can adopt the structure of the electrode 1 in the above embodiment. One end of the electrode tab 130 is connected to the conductive element 4, and the other end of the electrode tab 130 can extend out of the housing 110 to be connected to external electrical equipment.

[0074] When the electrode assembly 120 of the secondary battery 100 provided in this application adopts the structure of the electrode sheet 1 in the above embodiment, the risk of the thickness of the covered area being too thick due to the insulating layer 5 covering the active material layer 3 can be reduced, which is beneficial to reduce the overall thickness of the secondary battery 100 and improve the energy density of the secondary battery 100.

[0075] like Figure 8 As shown, another embodiment of this application provides a method for manufacturing electrode 1, used to prepare electrode 1 in the above embodiment. The method for manufacturing electrode 1 includes the following steps: Step S201: Provide the current collector 2 and the conductive element 4, wherein the current collector 2 includes a coated area and an uncoated area; Step S202: Coat the coating area of ​​the current collector 2 with an active material to form an active material layer 3, wherein the active material layer 3 includes a first covering portion 31 and a second covering portion 32 with unequal thicknesses; Step S203: Connect the conductive element 4 to the uncoated area of ​​the current collector 2 in an conductive manner; The conductive component 4 can be connected to the uncoated area of ​​the current collector 2 by means of roll welding or other means, which can be set according to the needs. For example, it can be connected by riveting.

[0076] Step S204: Apply insulating material to the second part 22, at least a portion of the surface of the conductive element 4 away from the current collector 2, and at least a portion of the surface of the second cover 32 away from the current collector 2 to form an insulating layer 5.

[0077] In some embodiments, the following step is further included between step S201 and step S202: Step S205: Apply a primer to the coating area of ​​the current collector 2 to form a primer layer 6.

[0078] Compared to the previous method of preparing electrode sheets by simultaneously coating the insulating material and the active material layer before connecting the conductive element to the uncoated area, this method carries the risk of the conductive element's connection area not overlapping with the insulating material forming the insulating layer, resulting in a thicker area. Furthermore, since the conductive element is connected to the uncoated area only after the insulating material is coated, there is a risk of damaging the insulating layer during the connection process. In contrast, this application uses the above-described method to manufacture electrode sheet 1. After completing the active material coating step, the conductive element 4 is connected to the uncoated area of ​​the current collector 2. This ensures that the insulating material coating covers the area where the conductive element 4 and the current collector 2 are connected, which is beneficial for the insulating layer 5 formed by the insulating material to cover the area where the conductive element 4 and the current collector 2 are connected, reducing the risk of exposed burrs on the surface of the conductive element 4.

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

Claims

1. An electrode sheet, characterized in that, include: The current collector includes a first portion and a second portion disposed adjacent to each other along a first direction; An active material layer is disposed in the first part, and the active material layer includes a first covering part and a second covering part disposed sequentially along the first direction, wherein the thickness of the second covering part is less than the thickness of the first covering part along the thickness direction of the current collector; A conductive element, connected to the second part; An insulating layer is disposed on the surface of the second portion and at least a portion of the second cover portion away from the current collector, wherein the first direction is perpendicular to the thickness direction of the current collector.

2. The electrode sheet according to claim 1, characterized in that, Along the thickness direction of the current collector, the difference between the thickness of the first cover and the thickness of the second cover is t1, which satisfies 10μm<t1≤50μm.

3. The electrode sheet according to claim 1, characterized in that, Along the first direction, the width of the second covering part is d1, which satisfies 1mm < d1 ≤ 2mm.

4. The electrode sheet according to claim 3, characterized in that, 1mm<d1≤1.5mm.

5. The electrode sheet according to claim 1, characterized in that, The insulating layer includes a first insulating portion that overlaps with the first covering portion. Along the first direction, the width of the first insulating portion is d2, which satisfies 0.1mm < d2 ≤ 1.6mm.

6. The electrode sheet according to claim 5, characterized in that, 0.1mm < d2 ≤ 1mm.

7. The electrode sheet according to claim 1, characterized in that, The insulating layer includes a first insulating portion, a second insulating portion, and a third insulating portion. The first insulating portion, the second insulating portion, and the third insulating portion are arranged sequentially along the first direction. The first insulating portion overlaps with the first covering portion. The third insulating portion covers the surface of the conductive element away from the current collector. Along the thickness direction of the current collector, the thickness of the second insulating portion is t2, which satisfies 10μm<t2≤50μm. And / or, along the first direction, the width of the insulating layer is d3, satisfying 1.2mm < d3 < 5mm.

8. The electrode sheet according to claim 1, characterized in that, The conductive component is connected to the second part by roll welding to form a solder mark. The dimension of the solder mark in the first direction is d4, which satisfies 1mm < d4 < 5mm.

9. The electrode sheet according to claim 1, characterized in that, At least a portion of the conductive element has an insulating layer disposed on its surface away from the current collector, the insulating layer comprising an inorganic ceramic or a non-conductive organic polymer layer.

10. The electrode sheet according to any one of claims 1-9, characterized in that, It also includes a base coating layer, which is disposed between the first portion and the active material layer along the thickness direction of the current collector.

11. The electrode according to claim 10, characterized in that, The active material layer includes a first active material layer and a second active material layer, and the base coating layer includes a first base coating layer and a second base coating layer. The current collector includes a base layer, a first conductive layer, and a second conductive layer. The first conductive layer is disposed on one surface of the base layer, and the second conductive layer is disposed on the other surface of the base layer. The first conductive layer has a first base coating layer and a first active material layer disposed sequentially on one end face away from the base layer, and the second conductive layer has a second base coating layer and a second active material layer disposed sequentially on one end face away from the base layer. The base layer is a polymer layer.

12. The electrode sheet according to claim 11, characterized in that, The conductive element includes a first conductive element and a second conductive element, wherein the first conductive element is connected to the first conductive layer, and the second conductive element is connected to the second conductive layer.

13. A secondary battery, characterized in that, Includes the electrode as described in any one of claims 1-12.

14. An electrical appliance, characterized in that, Includes the secondary battery as described in claim 13.

15. A method for manufacturing an electrode sheet, used to prepare the electrode sheet as described in any one of claims 1-12, characterized in that, The manufacturing method includes: Step 1: Provide the current collector and the conductive element, wherein the current collector includes a coated area and an uncoated area; Step 2: Coat the coating area of ​​the current collector with an active material to form the active material layer, the active material layer including a first covering portion and a second covering portion with unequal thickness; Step 3: Connect the conductive component to the uncoated area of ​​the current collector; Step 4: Apply insulating material to the second part, at least a portion of the conductive element's surface away from the current collector, and at least a portion of the second cover's surface away from the current collector to form the insulating layer.

16. The method for manufacturing an electrode according to claim 15, characterized in that, The conductive element is connected to the uncoated area of ​​the current collector by roll welding.

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