Pole piece, battery, battery assembly, and electric device

Abstract

The application provides a pole piece, a battery, a battery assembly and an electric device. The pole piece comprises a current collector and a paste coating layer. The current collector comprises an empty foil area and a coating area. The empty foil area and the coating area are arranged along a first direction. The empty foil area is configured to be connected with a pole lug or to process a pole lug. The paste coating layer is arranged on at least one side of the coating area in the thickness direction. The paste coating layer comprises a first coating layer. The first coating layer comprises a first sub-coating layer and at least one second sub-coating layer. The at least one second sub-coating layer is adjacent to the side of the first sub-coating layer along the first direction, and the at least one second sub-coating layer is arranged close to the empty foil area relative to the first sub-coating layer. The electrical conductivity of the first sub-coating layer is greater than that of the second sub-coating layer. The extension size of a single second sub-coating layer along the first direction is A, and the extension size of the first sub-coating layer along the first direction is B. A and B satisfy: 0.2*(A+B / 2)≤A≤0.4*(A+B / 2). The battery made of the pole piece of the application is not prone to lithium precipitation.

Description

Technical Field

[0001] This application relates to the field of battery technology, and more particularly to an electrode, a battery, a battery assembly, and an electrical device. Background Technology

[0002] In related technologies, lithium-ion batteries include a casing and an electrode core. The electrode core includes an electrode sheet and a separator. The electrode sheet is divided into a positive electrode sheet and a negative electrode sheet. The positive electrode sheet, separator and negative electrode sheet are stacked. The electrode sheet includes a current collector and an active material layer disposed on the surface of the current collector. A tab is provided on one side of the electrode sheet. The tab is connected to the current collector, thereby facilitating the transmission of current by the electrode sheet.

[0003] However, during battery charging, the side of the electrode with tabs experiences a higher temperature rise, lower internal resistance, and higher current density, while the middle part of the electrode experiences a lower temperature rise, higher internal resistance, and lower current density. This results in an uneven distribution of current density on the electrode, which in turn makes the negative electrode prone to lithium plating, thereby reducing battery safety. Utility Model Content

[0004] Based on this, this application provides an electrode sheet, a battery, a battery assembly, and an electrical device. The electrode sheet and the separator are stacked to form an electrode core. A tab is provided on one edge of the electrode core, or tabs are provided on both opposite edges of the electrode core. By providing a first sub-coating with higher conductivity and a second sub-coating with lower conductivity, the first sub-coating is positioned away from the tabs relative to the second sub-coating, and the extension dimensions of both along the first direction satisfy: 0.2*(A+B / 2)≤A≤0.4*(A+B / 2), the internal resistance of the first sub-coating is reduced, thereby reducing the conductivity difference between the first and second sub-coatings. This, in turn, reduces the conductivity difference between the side of the electrode core with tabs and the side of the electrode core without tabs, or reduces the conductivity difference between the opposite sides of the electrode core with tabs and the middle part of the electrode core without tabs. This results in a more uniform current density when the electrode core is charged, thus solving the problem of lithium plating in batteries in related technologies.

[0005] In a first aspect, this application provides an electrode sheet, comprising:

[0006] The current collector includes an empty foil area and a coated area, which are arranged along a first direction. The empty foil area is configured to be connected to a tab or to have a tab processed into it.

[0007] The paste layer is disposed on at least one side of the coating area in the thickness direction. The paste layer includes a first coating layer, the first coating layer includes a first sub-coating layer and at least one second sub-coating layer, the at least one second sub-coating layer is adjacent to the side of the first sub-coating layer along the first direction, and the at least one second sub-coating layer is disposed close to the empty foil area relative to the first sub-coating layer.

[0008] The conductivity of the first sub-coating is greater than that of the second sub-coating, and the extension dimension of a single second sub-coating along the first direction is A;

[0009] The first sub-coating extends by a dimension B along the first direction;

[0010] A and B satisfy: 0.2*(A+B / 2)≤A≤0.4*(A+B / 2).

[0011] In one possible implementation, the specific capacity of the first sub-coating is less than that of the second sub-coating.

[0012] In one possible implementation, the first sub-coating and the second sub-coating have the same thickness.

[0013] In one possible implementation, the first sub-coating is a conductive layer, and the second sub-coating is an active layer.

[0014] In one possible implementation, the thickness D of the first sub-coating satisfies: 0.5 mm ≤ D ≤ 5 mm.

[0015] In one possible implementation, the electrode is a negative electrode, and along the first direction, the specific capacity of the second sub-coating gradually increases from the side closer to the first sub-coating to the side farther away from the first sub-coating.

[0016] In one possible implementation, the electrode is a positive electrode, and along the first direction, the specific capacity of the second sub-coating gradually decreases from the side closer to the first sub-coating to the side farther away from the first sub-coating.

[0017] In one possible implementation, two second sub-coatings are adjacent to the first sub-coating on both sides along a first direction.

[0018] In one possible implementation, the electrode further includes a second coating, with the coating area, the first coating, and the second coating stacked sequentially.

[0019] The specific capacity of the second coating is greater than that of the second sub-coating.

[0020] In one possible implementation, the second coating includes a third sub-coating and a fourth sub-coating, with the coating area, the first coating, the third sub-coating and the fourth sub-coating stacked sequentially.

[0021] The specific capacity of the fourth sub-coating is less than that of the third sub-coating.

[0022] In one possible implementation, the second coating has at least two wetting grooves on the side facing away from the current collector.

[0023] In one possible implementation, the width F of the immersion tank satisfies: 20μm≤F≤80μm.

[0024] In one possible implementation, the thickness C of the paste layer and the depth H of the impregnation tank satisfy: 0.2*C≤H≤0.45*C.

[0025] In one possible implementation, the distance G between two adjacent immersion tanks satisfies: 500μm≤G≤800μm.

[0026] Secondly, this application provides a battery, comprising:

[0027] A positive electrode and a negative electrode, wherein at least one of the positive electrode and the negative electrode is the electrode provided in the first aspect above;

[0028] The separator, positive electrode, and negative electrode are stacked together to form the electrode core.

[0029] In one possible implementation, the positive electrode plate is provided with a positive electrode tab, and the negative electrode plate is provided with a negative electrode tab;

[0030] The positive and negative tabs are located on one side of the electrode core along the first direction, or the positive and negative tabs are located on both sides of the electrode core along the first direction.

[0031] Thirdly, this application provides a battery assembly including at least one battery provided in the second aspect above.

[0032] Fourthly, this application provides an electrical device, including an electrical appliance, a battery provided in the second aspect above or a battery provided in the third aspect above, wherein the battery or battery assembly is used to supply power to the electrical appliance.

[0033] The electrode, battery, battery assembly, and electrical device provided in the embodiments of this application include an electrode comprising a current collector and a paste layer. The current collector includes an empty foil area and a coated area. The paste layer includes a first coating layer, which includes a first sub-coating layer and a second sub-coating layer. By setting an empty foil area for processing or connecting the tabs, setting a coating area for carrying the paste layer, and setting a first sub-coating with high conductivity on the side of the electrode away from the tab, the resistance on the side of the electrode away from the tab is reduced, thereby narrowing the conductivity difference between the side of the electrode near the tab and the side of the electrode away from the tab. This results in a more uniform current density on the electrode along the first direction, preventing lithium deposition on the side of the electrode near the tab. Furthermore, the extension dimensions of the first and second sub-coatings along the first direction satisfy: 0.2*(A+B / 2)≤A≤0.4*(A+B / 2). This prevents the first sub-coating from being too short, leading to excessive resistance on the side of the electrode away from the tab, which would cause lithium deposition on the side of the electrode near the tab. It also prevents the first sub-coating from being too long, resulting in insufficient lithium intercalation space provided by the second sub-coating, which would also cause lithium deposition on the side of the electrode near the tab. Therefore, the electrode provided in this embodiment is less prone to lithium deposition.

[0034] In addition to the technical problems solved by the embodiments of this application, the technical features constituting the technical solutions, and the beneficial effects brought about by the technical features of these technical solutions described above, other technical problems that can be solved by the electrode sheets, batteries, battery modules, and electrical equipment provided by this application, other technical features included in the technical solutions, and the beneficial effects brought about by these technical features will be further described in detail in the specific embodiments. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of the battery structure provided in an embodiment of this application;

[0037] Figure 2 This is yet another structural schematic diagram of the battery provided in an embodiment of this application;

[0038] Figure 3 Schematic diagram of the electrode structure provided in the embodiments of this application Figure 1 ;

[0039] Figure 4 Schematic diagram of the electrode structure provided in the embodiments of this application Figure 2 ;

[0040] Figure 5 This is a schematic diagram of the current collector structure in the electrode provided in the embodiments of this application;

[0041] Figure 6 Schematic diagram of the electrode structure provided in the embodiments of this application Figure 3 ;

[0042] Figure 7 Schematic diagram of the electrode structure provided in the embodiments of this application Figure 4 ;

[0043] Figure 8 Schematic diagram of the electrode structure provided in the embodiments of this application Figure 5 ;

[0044] Figure 9 Schematic diagram of the electrode structure provided in the embodiments of this application Figure 6 ;

[0045] Figure 10 Schematic diagram of the electrode structure provided in the embodiments of this application Figure 7 ;

[0046] Figure 11 Schematic diagram of the electrode structure provided in the embodiments of this application Figure 8 ;

[0047] Figure 12 Schematic diagram of the electrode structure provided in the embodiments of this application Figure 9 ;

[0048] Figure 13 Schematic diagram of the electrode structure provided in the embodiments of this application Figure 10 ;

[0049] Figure 14 Schematic diagram of the electrode structure provided in the embodiments of this application Figure 10 one;

[0050] Figure 15 Schematic diagram of the electrode structure provided in the embodiments of this application Figure 10 two.

[0051] Explanation of reference numerals in the attached figures:

[0052] 10 - Electrode; 10a - Positive electrode; 10b - Negative electrode;

[0053] 100 - Current collector; 110 - Empty foil area; 120 - Coated area;

[0054] 200 - Coating layer; 210 - First coating layer; 211 - First sub-coating layer; 212 - Second sub-coating layer; 220 - Second coating layer; 221 - Third sub-coating layer; 222 - Fourth sub-coating layer; 223 - Impregnation tank;

[0055] 20-Diaphragm;

[0056] X - First direction. Detailed Implementation

[0057] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar components or components having the same or similar functions throughout. The described embodiments are some, but not all, embodiments of this application. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application. The embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0058] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, an indirect connection through an intermediate medium, or the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0059] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on 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.

[0060] The terms "first," "second," and "third" (if any) in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a particular order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein.

[0061] Furthermore, the terms “comprising” and “having”, and any variations thereof, are intended to cover non-exclusive inclusion, such that a process, method, system, product, or display that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or display.

[0062] In related technologies, lithium-ion batteries include a casing and an electrode core. The electrode core includes an electrode sheet and a separator. The electrode sheet is divided into a positive electrode sheet and a negative electrode sheet. The positive electrode sheet, separator and negative electrode sheet are stacked. The electrode sheet includes a current collector and an active material layer disposed on the surface of the current collector. A tab is provided on one side of the electrode sheet. The tab is connected to the current collector, thereby facilitating the transmission of current by the electrode sheet.

[0063] However, during battery charging, the side of the electrode with tabs experiences a higher temperature rise, lower internal resistance, and higher current density, while the middle part of the electrode experiences a lower temperature rise, higher internal resistance, and lower current density. This results in an uneven distribution of current density on the electrode, which in turn makes the side of the negative electrode with tabs prone to lithium plating, thereby reducing battery safety.

[0064] Simply increasing the ratio of conductive agent and binder in the active material layer can reduce the conductivity difference between the tab side and the middle of the electrode, allowing the active material layer to undergo electrochemical reactions at the same rate. However, this will severely reduce the proportion of active material in the electrode, and the battery will still be prone to lithium plating.

[0065] In view of the above problems, this application provides an electrode, a battery, a battery assembly, and an electrical device. The current collector of the electrode includes a coated area with a paste layer and an empty foil area without a paste layer. The empty foil area can be processed into a tab, or the tab can be connected to the empty foil area. By providing a first sub-coating with higher conductivity on the side of the coated area away from the tab and a second sub-coating with lower conductivity on the side of the coated area near the tab, the internal resistance of the electrode on the side away from the tab is reduced, thereby reducing the conductivity difference between the side of the electrode near the tab and the side of the electrode away from the tab. This makes the current density of the electrode more uniform during battery charging, thereby preventing lithium deposition on the electrode. The extension dimensions of both along the first direction satisfy: 0.2*(A+B / 2)≤A≤0.4*(A+B / 2) to balance the conductivity and energy density of the first coating, thereby preventing lithium deposition on the electrode and improving battery safety.

[0066] The following detailed description, in conjunction with the accompanying drawings, illustrates the specific implementation methods of the electrode sheets, batteries, battery modules, and electrical devices provided in the embodiments of this application.

[0067] Reference Figure 1 and Figure 2 As shown, the battery provided in this application embodiment includes an electrode 10 and a separator 20. The electrode 10 may include a positive electrode 10a and a negative electrode 10b. The positive electrode 10a, the separator 20 and the negative electrode 10b are stacked and wound to form a wound electrode core. Alternatively, the positive electrode 10a, the separator 20 and the negative electrode 10b are alternately stacked to form a stacked electrode core. This application embodiment does not limit this.

[0068] Among them, the positive electrode 10a is provided with a positive electrode tab, and the negative electrode 10b is provided with a negative electrode tab, such as Figure 1 As shown, the positive and negative tabs can be located on one side of the electrode core along the first direction. This configuration can be applied to VDA (Verband der Automobilindustrie) standard batteries. Alternatively, as... Figure 2 As shown, the positive and negative tabs can be located on opposite sides of the electrode core along the first direction, and this scheme can be applied to blade batteries.

[0069] Reference Figures 2 to 7As shown, based on the above embodiments, this application also provides an electrode 10, which can be a positive electrode 10a or a negative electrode 10b. The electrode 10 includes a current collector 100 and a paste layer 200. The current collector 100 includes an empty foil region 110 and a coated region 120. The empty foil region 110 and the coated region 120 are arranged along a first direction X. The empty foil region 110 is configured to be connected to an electrode tab or to be configured to have an electrode tab processed.

[0070] The paste layer 200 is disposed on at least one side of the coating area 120 in the thickness direction. The paste layer 200 includes a first coating layer 210, which includes a first sub-coating layer 211 and at least one second sub-coating layer 212. The at least one second sub-coating layer 212 is adjacent to the side of the first sub-coating layer 211 along the first direction X, and the at least one second sub-coating layer 212 is disposed near the empty foil area 110 relative to the first sub-coating layer 211.

[0071] The conductivity of the first sub-coating 211 is greater than that of the second sub-coating 212. The extension dimension of a single second sub-coating 212 along the first direction X is A, and the extension dimension of the first sub-coating 211 along the first direction X is B. A and B satisfy: 0.2*(A+B / 2)≤A≤0.4*(A+B / 2).

[0072] In this embodiment, the current collector 100 is used to carry the paste layer 200 and to collect the current of the electrode 10. The paste layer 200 is used to undergo an electrochemical reaction with the electrolyte, thereby storing or releasing electrical energy.

[0073] Specifically, the current collector 100 may include a coating area 120 for coating a slurry to form a paste layer 200. The paste layer 200 may be disposed on one or both sides of the current collector 100 in the thickness direction. The current collector 100 may also include an empty foil area 110, which is not coated with slurry so that the empty foil area 110 can be die-cut to form an electrode tab, or the electrode tab can be connected to the empty foil area 110 to transmit the current of the current collector 100 through the electrode tab.

[0074] For a wound electrode core, the tab can be located on one side of the current collector 100 in the width direction. For a stacked electrode core, the tab can be located on one side of the current collector 100 in the length direction. Therefore, the first direction X can be either the length direction of the current collector 100 or the width direction of the current collector 100.

[0075] The coating layer 200 may include a first coating layer 210, which may include a first sub-coating layer 211 and a second sub-coating layer 212 disposed along a first direction X, wherein the first sub-coating layer 211 is disposed away from the tab and the second sub-coating layer 212 is disposed close to the tab.

[0076] Because the conductivity of the first sub-coating 211 is greater than that of the second sub-coating 212, the resistance of the first sub-coating 211 is lower, while the resistance of the second sub-coating 212 is higher. Thus, during charging, the resistance of the second sub-coating 212 decreases due to a faster temperature rise, approaching the resistance of the first sub-coating 211. This reduces the conductivity difference between the two sub-coatings, resulting in a more uniform current density when the current is transmitted along the first direction X. This prevents lithium deposition on the side of the electrode 10 closest to the tab. Furthermore, the first sub-coating 211 can be a conductive carbon layer, which enhances the liquid retention capacity of the electrode 10, thereby improving the wetting effect and preventing lithium deposition in the center of the electrode 10. The second sub-coating 212 can be an active layer to provide lithium intercalation space or to provide lithium ions.

[0077] It should be noted that if the tabs of the negative electrode 10b and the positive electrode 10a are located on the same side, the first sub-coating 211 and the second sub-coating 212 can be sequentially arranged along the first direction X, with the first sub-coating 211 located away from the tab and the second sub-coating 212 located close to the tab. This arrangement of the first sub-coating 211 improves the current transmission capability of the electrode 10 on the side away from the tab, resulting in a more uniform current density along the first direction X, thereby alleviating the lithium plating problem of the battery. When the electrode 10 is a negative electrode 10b, the specific capacity of the first sub-coating 211 is less than that of the second sub-coating 212. The arrangement of the second sub-coating 212 ensures that the portion of the negative electrode 10b corresponding to the tab has sufficient lithium intercalation space to prevent lithium plating on the negative electrode 10b. Alternatively, the arrangement of the second sub-coating 212 ensures that the portion of the positive electrode 10a corresponding to the tab can provide sufficient lithium ions to the negative electrode 10b to prevent lithium plating on the negative electrode 10b.

[0078] If the tabs of the negative electrode 10b and the positive electrode 10a are located on opposite sides, two second sub-coatings 212 can be located on either side of the first sub-coating 211 along the first direction X. That is, the second sub-coating 212, the first sub-coating 211, and the second sub-coating 212 are sequentially arranged along the first direction X, with the first sub-coating 211 located away from the tabs, one second sub-coating 212 located close to the tab of the positive electrode 10a, and the other second sub-coating 212 located close to the tab of the negative electrode 10b. In this way, the arrangement of the first sub-coating 211 can improve the current transmission capacity in the middle of the electrode 10, so that the current density of the electrode 10 along the first direction X is more uniform, thereby alleviating the lithium plating problem of the battery. When the electrode 10 is a negative electrode 10b, the specific capacity of the first sub-coating 211 is less than that of the second sub-coating 212. The arrangement of the second sub-coating 212 ensures that the part of the negative electrode 10b corresponding to the tab has sufficient lithium intercalation space to prevent lithium plating on the negative electrode 10b.

[0079] In a specific configuration, the extension dimensions of the first sub-coating 211 and the second sub-coating 212 along the first direction X can satisfy: 0.2*(A+B)≤A≤0.4*(A+B). Here, when the first coating 210 includes one first sub-coating 211 and one second sub-coating 212, A+B can be understood as the extension dimension of the first coating 210 along the first direction X. When the first coating 210 includes one first sub-coating 211 and two second sub-coatings 212, 2*A+B can be understood as the extension dimension of the first coating 210 along the first direction X, where A is the extension dimension of a single second sub-coating 212 along the first direction X, and B is the extension dimension of the first sub-coating 211 along the first direction X.

[0080] If A is less than 0.2*(A+B / 2), the second sub-coating 212 will be too short, which in turn will cause the first sub-coating 211 to be too long. When a high proportion of conductive agent is added to the first sub-coating 211, the proportion of active material in the first sub-coating 211 will inevitably be sacrificed, thereby reducing the energy density of the first coating 210 and causing the second sub-coating 212 to be too short. The second sub-coating 212 cannot provide enough lithium intercalation space, which in turn will cause lithium deposition on the side of the electrode 10 near the tab. If A is greater than 0.4*(A+B / 2), the second sub-coating 212 will be too long, which in turn will cause the first sub-coating 211 to be too short. The first sub-coating 211 cannot play the role of uniform current density, which in turn will cause lithium deposition on the side of the electrode 10 near the tab.

[0081] Therefore, in this embodiment, A is between 0.2*(A+B / 2) and 0.4*(A+B / 2) to balance the extension dimensions of the first sub-coating 211 and the second sub-coating 212 along the first direction X, which is beneficial to simultaneously improve the conductivity of the first coating 210 near the tab and the overall energy density of the electrode 10.

[0082] The electrode 10 provided in this embodiment includes a current collector 100 and a paste layer 200. The current collector 100 includes an empty foil region 110 and a coating region 120. The paste layer 200 includes a first coating layer 210, which includes a first sub-coating layer 211 and a second sub-coating layer 212. By providing the empty foil region 110 for processing or connecting electrode tabs, and by providing the coating region 120 for supporting the paste layer 200, and by providing the first sub-coating layer 211 with higher conductivity on the side of the electrode 10 away from the electrode tab, the resistance on the side of the electrode 10 away from the electrode tab is reduced. This reduces the conductivity difference between the side of the electrode 10 near the electrode tab and the side of the electrode 10 away from the electrode tab, resulting in a more uniform current density of the electrode 10 along the first direction X, thereby preventing precipitation on the side of the electrode 10 near the electrode tab. Lithium is incorporated into the electrode, and the extension dimensions of the first sub-coating 211 and the second sub-coating 212 along the first direction X satisfy: 0.2*(A+B / 2)≤A≤0.4*(A+B / 2). This prevents the first sub-coating 211 from being too short, which would result in excessive resistance on the side of the electrode 10 away from the tab, leading to lithium plating on the side of the electrode 10 near the tab. It also prevents the first sub-coating 211 from being too long, which would result in insufficient lithium intercalation space provided by the second sub-coating 212, leading to lithium plating on the side of the electrode 10 near the tab. Therefore, the electrode 10 provided in this embodiment is less prone to lithium plating.

[0083] In one possible implementation, the thickness D of the first sub-coating 211 satisfies: 0.5 mm ≤ D ≤ 5 mm.

[0084] It should be noted that if the thickness D of the first sub-coating 211 is too small, for example, less than 0.5 mm, the first sub-coating 211 cannot effectively improve the conductivity of the electrode 10. If the thickness D of the first sub-coating 211 is too large, for example, greater than 5 mm, the effect of the first sub-coating 211 in improving the conductivity of the electrode 10 will not increase with its thickness. In fact, an excessively large thickness D of the first sub-coating 211 will reduce the proportion of active material in the electrode 10.

[0085] Therefore, in this embodiment, the thickness of the first sub-coating 211 is between 0.5 mm and 5 mm to effectively improve the conductivity of the first sub-coating 211, thereby reducing the resistance on the side of the electrode 10 away from the tab, and thus uniformly distributing the current density of the electrode 10 along the first direction X, thereby preventing lithium deposition on the side of the electrode 10 closer to the tab. Furthermore, this helps to balance the conductivity and energy density of the electrode 10.

[0086] For example, the thickness of the first sub-coating 211 can be any one of 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, or 5 mm, or fall within any two of these values.

[0087] The thickness of the first sub-coating 211 is the same as that of the second sub-coating 212. The two are set to be of equal thickness so that the slurry can be applied to the surface of the first coating 210, which is conducive to forming a second coating 220 with uniform thickness.

[0088] In one possible implementation, the electrode 10 is a negative electrode 10b, and along the first direction X, the specific capacity of the second sub-coating 212 on the side closer to the first sub-coating 211 is less than the specific capacity of the second sub-coating 212 on the side farther from the first sub-coating 211.

[0089] It is understandable that when the electrode 10 is a negative electrode 10b, the part of the second sub-coating 212 that is closer to the tab is more likely to have lithium deposition due to insufficient lithium intercalation space. Therefore, the specific capacity of the second sub-coating 212 can be gradually set so that the specific capacity is higher closer to the tab, which is conducive to gradually increasing the lithium intercalation space of the negative electrode 10b and thus preventing lithium deposition on the side of the negative electrode 10b that is closer to the tab.

[0090] For the negative electrode 10b, the second sub-coating 212 may include graphite and silicon materials. The specific capacity can be increased by adding different proportions of silicon material to the second sub-coating 212; the higher the proportion of silicon material in the second sub-coating 212, the higher its specific capacity. The silicon material can be silicon-carbon, silicon-oxygen, etc., with silicon-carbon materials having a specific capacity as high as 1600 mAh / g, which can significantly improve the capacity of the negative electrode 10b.

[0091] In some embodiments, when the electrode 10 is a positive electrode 10a, along the first direction X, the specific capacity of the second sub-coating 212 gradually decreases from the side closer to the first sub-coating 211 to the side farther away from the first sub-coating 211, thereby making the positive electrode 10a closer to the tab have less lithium ion content, thereby avoiding lithium plating on the side of the negative electrode 10b close to the tab due to insufficient lithium intercalation space.

[0092] Reference Figure 6 , Figure 7 As shown, in one possible implementation, the electrode 10 further includes a second coating 220, with the coating area 120, the first coating 210, and the second coating 220 stacked sequentially. The specific capacity of the second coating 220 is greater than the specific capacity of the second sub-coating 212.

[0093] With this configuration, the first coating 210 has good conductivity, which enables the current to be transmitted uniformly along the first direction X and improves the charging and discharging rate of the electrode 10. The second coating 220 has high energy density, thereby ensuring that the electrode 10 has high capacity.

[0094] Continue to refer to Figure 6 , Figure 7As shown, in some embodiments, the second coating 220 includes a third sub-coating 221 and a fourth sub-coating 222, and the coating area 120, the first coating 210, the third sub-coating 221, and the fourth sub-coating 222 are stacked sequentially. The specific capacity of the fourth sub-coating 222 is less than that of the third sub-coating 221.

[0095] For example, for the negative electrode 10b, the fourth sub-coating 222 can use graphite as the negative electrode active material, and the third sub-coating 221 can use graphite doped with silicon as the negative electrode active material. Since the specific capacity of silicon is greater than that of graphite, the specific capacity of the third sub-coating 221 is greater than that of the fourth sub-coating 222, thereby giving the third sub-coating 221 a higher energy density, which in turn improves the energy density of the electrode 10, and avoids severe expansion and contraction of the electrode 10 due to a high silicon doping ratio.

[0096] The thickness of the fourth sub-coating 222 can be E. The thickness of the third sub-coating 221 is the thickness of the paste layer 200 C minus the thickness of the first coating layer 210 D, and then minus the thickness of the fourth sub-coating 222 E, i.e., CDE. The thicknesses of the fourth sub-coating 222 and the third sub-coating 221 can be set as needed, and this embodiment does not impose specific limitations on them.

[0097] Reference Figures 8 to 15 As shown, in one possible implementation, the second coating 220 has at least two wetting grooves 223 on the side facing away from the current collector 100.

[0098] For example, laser etching technology can be used to process the second coating 220 to form an impregnation groove 223, thereby improving the impregnation effect of the electrode 10. For the negative electrode 10b, the impregnation groove 223 can also provide a buffer space for the expansion of silicon, thereby preventing the negative electrode 10b and the positive electrode 10a from squeezing each other, which would cause the electrode 10 to shed powder, thus preventing lithium plating in the battery.

[0099] The shape of the immersion tank 223 is not limited, and can be referenced. Figure 8 , Figures 11 to 15 set up.

[0100] In some embodiments, the width F of the immersion tank 223 satisfies: 20μm≤F≤80μm.

[0101] On the one hand, if the width of the wetting tank 223 is too small, for example, less than 20 μm, the space of the wetting tank 223 will be small, making it difficult to effectively absorb the electrolyte, and thus failing to effectively improve the wetting effect of the electrode 10. On the other hand, if the width of the wetting tank 223 is too large, for example, greater than 80 μm, the space of the wetting tank 223 will be large, and too much active material will be removed by the second coating 220, thereby reducing the proportion of active material in the second coating 220 and sacrificing the energy density of the electrode 10.

[0102] In this embodiment, the width of the wetting groove 223 is set between 20μm and 80μm, which can form a sufficiently large wetting groove 223 to improve the wetting effect of the electrode 10 and prevent the energy density of the electrode 10 from being sacrificed due to the setting of the wetting groove 223.

[0103] It should be noted that when the shape of the immersion tank 223 is Figure 13 When illustrating a circular hole, the width F of the immersion groove 223 can be understood as the diameter of the circular hole.

[0104] In some embodiments, the thickness C of the paste layer 200 and the depth H of the impregnation tank 223 satisfy: 0.2*C≤H≤0.45*C.

[0105] For example, the width of the wetting tank 223 can be any value among 20μm, 35μm, 40μm, 50μm, 75μm, and 80μm, or within any two of these values. Understandably, if the depth H of the wetting tank 223 is less than 0.2*C, the space of the wetting tank 223 will be too small, making it difficult to effectively absorb the electrolyte, thus failing to effectively improve the wetting effect of the electrode 10, and also hindering the provision of buffer space for silicon expansion. If the depth H of the wetting tank 223 is greater than 0.45*C, the second coating 220 will require the removal of a significant amount of active material during the processing of the wetting tank 223, resulting in a lower proportion of active material in the second coating 220, thereby reducing the capacity of the electrode 10.

[0106] When the depth H of the immersion tank 223 is between 0.2°C and 0.45°C, the immersion tank 223 can absorb the electrolyte, thereby improving the wetting effect of the electrode 10, and helping to release the expansion stress of the silicon material, while also helping to increase the capacity of the electrode 10.

[0107] In some embodiments, the distance G between two adjacent immersion tanks 223 satisfies: 500μm≤G≤800μm.

[0108] It should be noted that if the distance between two adjacent wetting grooves 223 is less than 500 μm, the wetting grooves 223 are too dense, which reduces the proportion of active material in the second coating 220. If the distance between two adjacent wetting grooves 223 is greater than 800 μm, the wetting grooves 223 are too sparse, which is not conducive to improving the wetting effect of the electrode 10 and releasing the expansion stress of the silicon material. The distance between two adjacent wetting grooves 223 is between 500 μm and 800 μm, which is conducive to forming uniform wetting grooves 223 on the second coating 220, and thus conducive to improving the wetting effect of the electrode 10 and releasing the expansion stress of the silicon material through the wetting grooves 223.

[0109] For example, the spacing of the immersion tank 223 can be any one of 500μm, 550μm, 600μm, 620μm, 740μm, 800μm or within any two of these values.

[0110] The following describes the battery manufacturing process and related testing.

[0111] Example 1:

[0112] I. The positive electrode 10a is prepared with slurry according to the formula. The positive electrode 10a adopts the lithium supplementation scheme. The negative electrode 10b is prepared with three kinds of slurry: conductive carbon layer slurry, graphite slurry with 3% silicon carbon doping and pure graphite slurry.

[0113] 2. The positive electrode 10a is first coated with a conductive coating, then coated with a positive electrode slurry. After the coating is applied, the positive electrode 10a is baked, rolled, slit, and die-cut, and then stacked with the negative electrode 10b.

[0114] 3. The negative electrode 10b employs a segmented three-layer coating technology. The lower layer uses a conductive carbon slurry coated away from the empty foil area 110 to form the first sub-coating 211. The width of the first sub-coating 211 is B, where B = 294 mm, and the thickness is D = 2 μm. The lower layer, near the empty foil area 110, and the middle layer are coated with a 3% silicon-doped graphite slurry, thus forming the second sub-coating 212 and the third sub-coating 221. The width of the second sub-coating 212 is A = 50 mm, and the thickness of the third sub-coating 221 is CDE = 31 μm. The upper layer is coated with graphite slurry, thus forming the fourth sub-coating 222, which has a thickness E = 31 μm.

[0115] After coating, baking, rolling and slitting, the negative electrode 10b after rolling and slitting is laser-etched to form wetting grooves 223. After die cutting, it is stacked with the positive electrode 10a. The width of the wetting groove 223 is F = 20 μm, the spacing of the wetting grooves 223 is G = 500 μm, and the depth of the wetting groove 223 is H = 0.3*C.

[0116] IV. The positive electrode 10a, separator 20 and negative electrode 10b are stacked and hot-pressed to form an electrode core. After the electrode core is assembled into the casing, a dry cell is formed. The cell is then subjected to liquid injection, pre-charging, wetting, formation, liquid replenishment, charging, aging and capacity testing in sequence to prepare the finished battery.

[0117] Example 2:

[0118] Unlike Example 1, the second sub-coating 212 and the third sub-coating 221 adopt a 0.2% silicon-carbon doping scheme, while the rest is the same as Example 1.

[0119] Example 3:

[0120] Unlike Example 1, the second sub-coating 212 and the third sub-coating 221 both adopt an 8% silicon-carbon doping scheme, while the rest is the same as in Example 1.

[0121] Example 4:

[0122] The difference from Example 1 is that D = 3 μm, F = 80 μm, G = 800 μm, H = 0.45 * C, and the rest is the same as Example 1.

[0123] Example 5:

[0124] The difference from Example 4 is that D = 5 μm, otherwise it is the same as Example 4.

[0125] Example 6:

[0126] Unlike Example 1, the second coating 220 does not have an impregnation tank 223, but otherwise it is the same as Example 1.

[0127] Example 7:

[0128] The difference from Example 6 is that A = 40 mm, otherwise it is the same as Example 6.

[0129] Example 8:

[0130] The difference from Example 6 is that A = 90 mm, otherwise it is the same as Example 6.

[0131] Comparative Example 1:

[0132] The difference from Example 4 is that B = 334 mm and A = 30 mm, but the rest is the same as Example 4.

[0133] Comparative Example 2:

[0134] The difference from Example 4 is that B = 214 mm and A = 90 mm, but the rest is the same as Example 4.

[0135] Comparative Example 3:

[0136] The positive electrode 10a and the negative electrode 10b are prepared with slurry according to the formula. Graphite is used as the active material of the negative electrode 10b. The negative electrode 10b is coated with a single layer. The electrode 10 is not laser etched. Everything else is the same as in Example 1.

[0137] Batteries from different embodiments and comparative examples were subjected to continuous fast charging cycle at a constant temperature of 25±2℃, with a maximum fast charging rate of 8C. After a 30-minute rest period, the batteries were discharged to 3.0V at a rate of 0.5C. This charge-discharge cycle was repeated 800 times. The discharge capacity, expansion force, and lithium plating status of the 800th cycle were recorded. The capacity retention rate after the cycle (%) was calculated as: discharge capacity after 800 cycles / initial discharge capacity × 100%.

[0138]

[0139]

[0140] As shown in the table above, the first sub-coating 211 and the second sub-coating 212 in Examples 1 to 8 all satisfy the condition: 0.2*(A+B / 2)≤A≤0.4*(A+B / 2), resulting in high battery capacity retention and no lithium plating. However, the first sub-coating 211 and the second sub-coating 212 in Comparative Examples 1 and 2 do not satisfy the condition: 0.2*(A+B / 2)≤A≤0.4*(A+B / 2). In Comparative Example 3, the first sub-coating 211 and the second sub-coating 212 were not segmented, and lithium plating occurred in all of them.

[0141] Based on the above embodiments, this application also provides a battery assembly, which includes at least one battery. The structure and working principle of the battery have been described in detail in the foregoing embodiments and will not be repeated here.

[0142] For example, a battery assembly may include multiple batteries, which can be connected in series or in parallel via copper busbars. Alternatively, a battery assembly may include a battery and a protection board assembly, which is electrically connected to the battery and used to monitor the battery's current, voltage, etc.

[0143] Based on the above embodiments, this application also provides an electrical device, including an electrical device and a battery or battery assembly provided in the above embodiments, wherein the battery or battery assembly is used to supply power to the electrical device.

[0144] The structure and working principle of the battery and battery assembly have been described in detail in the foregoing embodiments, and will not be repeated here.

[0145] For example, the electrical equipment can be a vehicle, the electrical device can be an electric motor, and the battery or battery pack can provide electrical energy to the electric motor, thereby driving the vehicle. The vehicle can be a pure electric vehicle, a range-extended electric vehicle, a hybrid electric vehicle, etc., and can also be any vehicle with a battery; this embodiment does not limit this.

[0146] Alternatively, electrical equipment can also include ships, aircraft, electronic terminal equipment, electrical appliances, and energy storage equipment, which will not be described in detail here.

[0147] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. An electrode sheet, characterized in that, include: A current collector (100) includes an empty foil area (110) and a coating area (120), the empty foil area (110) and the coating area (120) being arranged along a first direction, the empty foil area (110) being configured to connect with a tab or to be configured to have a tab processed in it; A paste layer (200) is disposed on at least one side of the coating area (120) in the thickness direction. The paste layer (200) includes a first coating layer (210), which includes a first sub-coating layer (211) and at least one second sub-coating layer (212). At least one second sub-coating layer (212) is adjacent to the side of the first sub-coating layer (211) along the first direction, and at least one second sub-coating layer (212) is disposed close to the empty foil area (110) relative to the first sub-coating layer (211). The conductivity of the first sub-coating (211) is greater than that of the second sub-coating (212), the extension dimension of a single second sub-coating (212) along the first direction is A, and the extension dimension of the first sub-coating (211) along the first direction is B. A and B satisfy: 0.2*(A+B / 2)≤A≤0.4*(A+B / 2).

2. The electrode sheet according to claim 1, characterized in that, The specific capacity of the first sub-coating (211) is less than that of the second sub-coating (212).

3. The electrode sheet according to claim 1, characterized in that, The first sub-coating (211) and the second sub-coating (212) have the same thickness.

4. The electrode sheet according to claim 1, characterized in that, The first sub-coating (211) is a conductive layer, and the second sub-coating (212) is an active layer.

5. The electrode sheet according to claim 3, characterized in that, The thickness D of the first sub-coating (211) satisfies: 0.5 mm ≤ D ≤ 5 mm.

6. The electrode sheet according to claim 2, characterized in that, The electrode is a negative electrode, and along the first direction, the specific capacity of the second sub-coating (212) gradually increases from the side closer to the first sub-coating (211) to the side farther away from the first sub-coating (211).

7. The electrode sheet according to claim 2, characterized in that, The electrode is a positive electrode, and along the first direction, the specific capacity of the second sub-coating (212) gradually decreases from the side closer to the first sub-coating (211) to the side farther away from the first sub-coating (211).

8. The electrode sheet according to claim 1, characterized in that, Two second sub-coatings (212) are adjacent to the first sub-coating (211) on both sides along the first direction.

9. The electrode sheet according to any one of claims 1-8, characterized in that, It also includes a second coating (220), wherein the coating area (120), the first coating (210) and the second coating (220) are stacked in sequence.

10. The electrode sheet according to claim 9, characterized in that, The specific capacity of the second coating (220) is greater than that of the second sub-coating (212).

11. The electrode according to claim 10, characterized in that, The second coating (220) includes a third sub-coating (221) and a fourth sub-coating (222), wherein the coating area (120), the first coating (210), the third sub-coating (221) and the fourth sub-coating (222) are stacked sequentially; The specific capacity of the fourth sub-coating (222) is less than that of the third sub-coating (221).

12. The electrode sheet according to claim 9, characterized in that, The second coating (220) has at least two wetting grooves (223) on the side opposite to the current collector (100).

13. The electrode sheet according to claim 12, characterized in that, The width F of the immersion tank (223) satisfies: 20μm≤F≤80μm.

14. The electrode sheet according to claim 12, characterized in that, The thickness C of the coating layer (200) and the depth H of the impregnation tank (223) satisfy: 0.2*C≤H≤0.45*C.

15. The electrode sheet according to claim 12, characterized in that, The distance G between two adjacent immersion tanks (223) satisfies: 500μm≤G≤800μm.

16. A battery, characterized in that, include: A positive electrode (10a) and a negative electrode (10b), wherein at least one of the positive electrode (10a) and the negative electrode (10b) is an electrode (10) as described in any one of claims 1-15; The separator (20), the positive electrode (10a), the separator (20) and the negative electrode (10b) are stacked to form the electrode core.

17. The battery according to claim 16, characterized in that, The positive electrode plate (10a) is provided with a positive electrode tab, and the negative electrode plate (10b) is provided with a negative electrode tab; The positive electrode tab and the negative electrode tab are located on one side of the electrode core along the first direction, or the positive electrode tab and the negative electrode tab are located on both sides of the electrode core along the first direction.

18. A battery assembly, characterized in that, It includes at least one battery as described in claim 16 or 17.

19. An electrical appliance, characterized in that, It includes an electrical device, a battery as described in any one of claims 16 and 17, or a battery assembly as described in claim 18, wherein the battery or the battery assembly is used to supply power to the electrical device.

Images