An electrode sheet and a battery cell structure

Abstract

The application discloses an electrode sheet and a battery cell structure. The electrode sheet comprises a current collector, an active material layer and a support layer. The current collector has a first surface and a second surface arranged oppositely. The second surface has a coating area and a light foil area. The active material layer is arranged on the first surface and the coating area. The support layer is coated on the light foil area. The first surface is provided with the active material layer in the areas corresponding to the coating area and the light foil area. The technical problem of single-side area wrinkling of the electrode sheet affecting the safety of the battery cell during winding is solved.

Description

Technical Field

[0001] This application relates to the field of battery cell technology, and in particular to an electrode sheet and a cell structure. Background Technology

[0002] As one of the core components of a battery, the electrode sheet plays a crucial role in conducting current, and its manufacturing and forming process has a significant impact on the final cell performance. In the current mainstream wound cell structure, the negative electrode sheet typically consists of a copper foil current collector and a layer of negative electrode active material. To meet the needs of cell structure design or functional differentiation, some areas are coated with active material only on the current collector side, forming a single-sided area. During the winding and forming process of the electrode sheet, the initial section located in the inner circle has poor structural stability due to its small bending radius. When this area is a single-sided area, it is more prone to defects such as local bending and wrinkling due to insufficient thickness and rigidity.

[0003] The aforementioned structural defects not only affect the appearance quality of the battery cell but also adversely impact its electrochemical performance. Especially when wrinkling occurs on one side, the negative electrode active material layer is easily damaged or detached mechanically, resulting in direct exposure of the current collector in that area. On the one hand, this weakens the electrochemical activity of that area, reducing the effective capacity; on the other hand, it easily induces lithium dendrite formation, creating a risk of lithium plating, and in severe cases, even causing internal short circuits, threatening battery safety.

[0004] Therefore, how to suppress wrinkling on one side of the electrode sheet during the winding process has become a technical problem that urgently needs to be solved for the safety of the battery cell. Utility Model Content

[0005] One objective of this application is to provide an electrode sheet and a battery cell structure that aims to solve the technical problem of wrinkling on one side of the electrode sheet during the winding process affecting the safety of the battery cell.

[0006] To achieve the above objectives, this application provides an electrode sheet comprising a current collector having a first surface and a second surface disposed opposite to each other, the second surface having a coating area and a foil area; an active material layer disposed on the first surface and the coating area; and a support layer coated on the foil area, wherein the active material layer is disposed on the areas of the first surface corresponding to the coating area and the foil area.

[0007] Optionally, the support layer extends in a direction away from the coating area, and the length of the support layer is less than or equal to the length of the foil area.

[0008] Optionally, the width of the support layer is d1, and the width of the foil area is d2, satisfying the relationship: 0.5d2≤d1≤d2.

[0009] Optionally, the centerline of the support layer along its length is collinear with the centerline of the foil area.

[0010] Optionally, the thickness of the support layer is t1, and the thickness of the active material layer is t2, satisfying the relationship: 0.6t2≤t1≤t2.

[0011] Optionally, the support layer includes multiple support parts, and the multiple support parts are distributed at equal intervals.

[0012] Optionally, the interval between adjacent support parts is h, and the width of the foil area is d2, satisfying the relationship: 0.1d2≤h≤0.3d2.

[0013] Optionally, the foil area is located in the inner circle of the electrode sheet after winding.

[0014] Optionally, the support layer has a chamfered structure on the sidewalls near the edge of the active material layer.

[0015] To achieve the above objectives, this application provides a solution: a battery cell structure, which includes a separator and the aforementioned electrode sheet, wherein the separator is disposed on the second surface side of the electrode sheet.

[0016] The beneficial effects of this application are as follows:

[0017] Compared to existing technologies, electrode sheets in single-sided coated areas are prone to wrinkling and folding during winding due to asymmetrical thickness and insufficient rigidity, leading to problems such as active material peeling and poor forming. This application introduces a heat-pressable support layer in the foil area, providing additional thickness and rigidity compensation to this area. After heat pressing, the support layer transforms into a solid-state reinforced structure, significantly improving the bending resistance and shape retention of the foil area, thereby effectively suppressing structural defects such as local buckling and stress concentration. Attached Figure Description

[0018] 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 only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the structure of an electrode sheet provided in an embodiment of this application;

[0020] Figure 2 This is a side view of the electrode sheet provided in an embodiment of this application;

[0021] Figure 3 This is a schematic diagram of another electrode sheet structure provided in an embodiment of this application;

[0022] Figure 4This is a schematic diagram of another electrode sheet provided in an embodiment of this application.

[0023] Explanation of icon numbers:

[0024] 10. Current collector; 11. First surface; 12. Second surface; 121. Foil area; 122. Coating area; 20. Active material layer; 30. Support layer; 31. Support part; 32. Chamfer. Detailed Implementation

[0025] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0026] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationship and movement of each component in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0027] It should also be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on the other component or may be connected to an intermediary component. When a component is referred to as being "connected to" another component, it can be directly connected to the other component or indirectly connected to the other component through an intermediary component.

[0028] Please see Figure 1 and Figure 2 , Figure 1 This is a schematic diagram of the structure of an electrode sheet provided in an embodiment of this application. Figure 2 This is a side view of the electrode sheet provided in the embodiment of this application.

[0029] This application provides an electrode sheet designed to address problems such as wrinkling and folding caused by insufficient structural rigidity in a single-sided area during the winding process. The electrode sheet includes a current collector 10, an active material layer 20, and a support layer 30.

[0030] The current collector 10 in the electrode sheet is made of metal foil, preferably copper or aluminum foil, which has good conductivity and flexibility. The electrode sheet has a first surface 11 and a second surface 12 arranged opposite to each other. The second surface 12 is divided into two different functional areas: a coated area 122, which is the area with the active material layer 20; and a bare foil area 121, which is the bare foil area without active material coating. The area corresponding to the first surface 11 and the coated area 122 and the bare foil area 121 is the fully coated area, with the active material layer 20 fully coated, providing the main electrochemical reaction interface. The bare foil area 121 is usually located at the beginning or edge of the electrode sheet to meet the needs of electrode welding, conductive connection, or cell structure transition.

[0031] A support layer 30 is disposed on the foil region 121 of the second surface 12 of the electrode sheet. This support layer 30 is a thermosetting polymer coating material. During the hot pressing or heating shaping process of the electrode sheet, it undergoes a thermosetting reaction, transforming into a solid reinforced structure with rigidity and shape retention, thereby significantly improving the overall stability and bending resistance of this region. The support layer 30 is coated only on the foil region 121 to avoid affecting the electrochemical performance of the coated region 122.

[0032] In this embodiment, the present application introduces a support layer 30 into the foil region 121, thereby increasing the thickness and stiffness of this region. This results in higher compressive stability under winding tension, effectively suppressing local buckling behavior and significantly reducing the probability of wrinkling defects. Compared to traditional structures, where the active material layer 20 is only distributed on one side of the electrode sheet's single-sided coating region 122, leading to asymmetrical thickness and insufficient local rigidity, stress concentration makes it prone to wrinkling, creases, and even active material peeling. The support layer 30 forms a stable structure after hot pressing, preventing deformation of the electrode sheet due to repeated stress during subsequent winding, welding, or housing assembly, thus improving the overall molding consistency and mechanical integrity of the battery cell.

[0033] In some optimized embodiments, the support layer 30 extends along the end of the foil region 121 away from the coating region 122, and its extension length is less than or equal to the length of the entire foil region 121. Specifically, the starting end of the support layer 30 is usually close to the boundary between the foil region 121 and the coating region 122 to maintain a smooth structural transition between the two, while the terminating end of the support layer 30 ends inside the foil region 121 to avoid exceeding the tab welding area, so as not to interfere with the subsequent packaging, welding or electrical performance release process requirements of the battery cell.

[0034] In this embodiment, by confining the support layer 30 within the foil region 121 and ensuring its length does not exceed the overall length of the foil region 121, effective reinforcement of critical stress areas can be achieved, while avoiding redundant processing or unnecessary material accumulation caused by the support material extending into functionally irrelevant areas. Furthermore, limiting the length of the support layer 30 also helps improve the interface consistency of the electrode sheets. If the support layer 30 extends beyond the foil region 121 into the coating region 122, it will create abrupt thickness changes during hot pressing, inducing local indentations or interface unevenness, which is detrimental to the winding density and the uniformity of the electrode sheet arrangement.

[0035] Further, please refer to Figure 3 , Figure 3 This is a schematic diagram of another electrode sheet structure provided in an embodiment of this application. In some embodiments, the width d1 of the support layer 30 is set to between 50% and 100% of the width d2 of the foil region 121, i.e., satisfying the relationship: 0.5d2 ≤ d1 ≤ d2. Here, the width d2 of the foil region 121 refers to the entire width of the electrode sheet in the transverse direction (i.e., perpendicular to the electrode sheet extension direction); the width d1 of the support layer 30 refers to the actual coverage width of the reinforcement structure in the direction corresponding to the foil region 121.

[0036] In this embodiment, by reasonably controlling the lateral coverage of the support layer 30, the overall bending resistance and wrinkle resistance of the foil region 121 under winding stress are effectively enhanced without interfering with the structure of the active material layer 20. Specifically, when the width d1 of the support layer 30 is close to the width d2 of the foil region 121, the support layer 30 can basically cover the entire foil region 121, providing comprehensive and uniform mechanical support in the lateral direction, which is especially suitable for scenarios with large winding tension, high cell energy density, or small process tolerance. Correspondingly, when the width d1 of the support layer 30 is about 50% of d2, the support layer 30 is mainly distributed in the central area of ​​the foil region 121, and can still form a rigid reinforcement effect in the center of the structure, which is suitable for application environments with certain requirements for flexibility and cell volume utilization.

[0037] In terms of technical effectiveness, by controlling the distribution range of the support layer 30 in the lateral direction so that it covers at least half the width of the foil area 121, a sufficiently rigid deformation-resistant band can be formed, which can effectively support the inner electrode sheet in the initial stage of winding, significantly reducing the risk of local wrinkling, creases or stress concentration.

[0038] As one implementation method, in some optimized embodiments, the center line of the support layer 30 along its length direction is collinear with the center line of the foil area 121. That is, the support layer 30 is arranged along the length direction of the electrode sheet in the foil area 121, and its lateral position is in the center of the foil area 121. In other words, when viewed from the lateral (width direction) of the electrode sheet, the support layer 30 is located in the middle region of the foil area 121, and the left and right sides are symmetrically distributed about the central axis.

[0039] In traditional structures, if the support layer 30 is offset from the center line of the foil area 121, the forces on the left and right sides will differ, easily leading to an asymmetrical compression state, which in turn causes the electrode sheet to roll off-center or wrinkle. In this embodiment, the support layer 30 is centrally located within the foil area 121, ensuring uniform lateral structural stiffness. This not only achieves symmetrical stiffness in structure but also ensures consistent bending response in mechanics, significantly improving the center retention capability and arrangement stability during the winding process.

[0040] Furthermore, the centrally symmetrical layout offers excellent processing adaptability and assembly tolerance. When the support layer 30 is formed using methods such as roll coating, thermal bonding, or pre-attachment, positioning with the center line of the foil area 121 as a reference enables high-precision automatic alignment control, avoiding misalignment of the support layer 30 caused by manual offset or equipment accuracy errors. Especially in mass production of continuous electrode sheets, the symmetry of lateral positioning helps improve the consistency of finished products and reduces the probability of structural failure caused by stress concentration or sudden changes in local stiffness.

[0041] Additionally, please refer to Figure 2 , Figure 2 This is a side view of the electrode sheet provided in an embodiment of this application. In some embodiments, the thickness t1 of the support layer 30 is set to be proportional to the thickness t2 of the active material layer 20, satisfying: 0.6t2≤t1≤t2. Here, t2 is the thickness of the active material layer 20 on the electrode sheet, typically representing the main source of thickness in that region; t1 is the thickness of the support layer 30 located in the foil region 121, used to provide structural support in the uncoated region 122 to reduce the risk of winding deformation caused by thickness asymmetry.

[0042] If the thickness t1 of the support layer 30 is less than 0.6t2, although a certain degree of reinforcement can still be formed in the foil area 121, the insufficient thickness of the support layer 30 limits its local compressive and bending stiffness, making it prone to buckling, wrinkling, or uneven curling. Furthermore, when the support layer 30 is too thin, the overall thickness distribution of the electrode sheet still exhibits significant asymmetry, failing to effectively alleviate problems such as uneven winding and interlayer gap changes caused by abrupt thickness changes. Ultimately, this may lead to risks such as reduced cell winding density, electrical performance degradation, and welding position misalignment.

[0043] Secondly, if the thickness t1 of the support layer 30 is greater than the thickness t2 of the active material layer 20, although it can provide higher mechanical support strength in the foil area 121, it will also introduce new problems: the excessive thickness of the support layer 30 will cause the overall cross-section of the electrode to form a protrusion in the foil area 121, resulting in a sudden change in thickness. This will cause the area to be subjected to excessive pressure or compression during the winding process, forming uneven contact with adjacent layers. This will not only easily cause stress accumulation in the winding of the electrode, but may also cause edge warping, stress concentration, or winding deviation during hot pressing. In addition, the excessively thick support layer 30 will also affect the overall thickness control of the electrode, interfere with the electrode tab welding height, finished product stacking tolerance, and even cause poor module assembly.

[0044] Therefore, in this embodiment, a thickness range of 0.6t2≤t1≤t2 is proposed. Within this range, the support layer 30 has sufficient thickness to provide effective anti-wrinkle reinforcement, but will not be significantly thicker than the active layer to cause process interference and structural inconsistency, thereby achieving a balance between ensuring winding consistency and thickness uniformity.

[0045] In other optimized embodiments, please refer to Figure 4 , Figure 4 This is a schematic diagram of another electrode sheet structure provided in an embodiment of this application. The support layer 30 is not a continuous integral structure, but is composed of multiple independent support portions 31, which are distributed within the foil area 121, arranged at equal intervals, and extend along the length direction of the electrode sheet. The support portions 31 can be several strip-shaped, block-shaped, or dot-shaped reinforcement structures, which are respectively attached to the surface of the foil area 121, arranged along the extension direction of the electrode sheet, and symmetrically distributed in the transverse direction. Regular gaps are reserved between each support portion 31, thus forming a discrete but regularly repeating support structure.

[0046] Compared to a continuous support layer 30, firstly, although the support portions 31 do not form a continuous coverage, their uniform arrangement still provides sufficient mechanical support at key locations, thus achieving anti-wrinkle enhancement without sacrificing flexibility. This is particularly suitable for suppressing deformation of the electrode sheet under high-stress conditions such as small-radius winding and rapid tensioning. Secondly, the spaced support portions 31 help improve stress dispersion capabilities. The gaps provide buffer space for minor deformations that may occur in the foil area 121 during winding, hot pressing, or assembly, thereby reducing the risk of micro-cracks or indentations caused by winding pressure. Furthermore, from a manufacturing perspective, using equally spaced support portions 31 reduces overall material consumption and manufacturing costs.

[0047] Furthermore, based on the discrete support structure, in some embodiments, the spacing h between adjacent support portions 31 is set to be proportional to the width d2 of the foil area 121, satisfying: 0.1d2≤h≤0.3d2. Here, d2 represents the total width of the foil area 121 in the transverse direction of the electrode sheet, and h represents the spacing distance between two adjacent support portions 31 along the length of the electrode sheet.

[0048] If the interval h is less than 0.1d², the distance between adjacent support parts 31 is too close, and the structure tends to be quasi-continuous. While this provides strong overall support strength, similar to the continuous support layer 30, its flexibility is significantly reduced. It cannot provide buffer space for minor deformations during winding or hot pressing, easily leading to excessive local stiffness, thus forming stress concentration zones or indentation zones and reducing winding compliance. Furthermore, excessively high density in the support parts 31 will significantly increase material usage, which is detrimental to cost control.

[0049] If the interval h is greater than 0.3d², the distance between adjacent support parts 31 is too far, and the support coverage rate decreases significantly. This will result in a large area of ​​unsupported region within the foil area 121. Under the action of winding stress, the gap area is very prone to local buckling or wrinkling, weakening the overall resistance to deformation and failing to effectively play a structural reinforcement role.

[0050] In contrast, this embodiment proposes an interval range of 0.1d² ≤ h ≤ 0.3d². This range achieves uniformity of the supporting force field structurally, ensures repeatability of the coating process in manufacturing, and provides the foil region 121 with greater adaptability while guaranteeing structural stability. When h is approximately 0.1d², the support portions 31 are arranged more densely, suitable for winding structures requiring high rigidity; while when h is close to 0.3d², the structure has better flexible buffering capabilities, suitable for flexible process requirements.

[0051] Preferably, as one embodiment, the foil area 121 is disposed in the electrode sheet corresponding to the inner ring position of the battery cell after winding. When the electrode sheet enters the winding process, its starting end is first wound onto the core or central shaft, forming the innermost winding area of ​​the battery cell; while the foil area 121 in this embodiment, that is, the area not coated with active material, is intentionally arranged at the starting end position, and after winding, it is located near the center of the inner ring of the battery cell.

[0052] By placing the foil region 121 within the inner ring of the electrode sheet, and in conjunction with the structural reinforcement design of the support layer 30 in this application, targeted structural reinforcement can be provided in the most easily deformable area. Through measures such as adjusting the thickness, optimizing the distribution, and symmetrically arranging the support layer 30, the insufficient rigidity of the foil region 121 structure is effectively compensated, giving it better bending resistance and deformation suppression capabilities during winding. This significantly reduces the probability of defects such as instability, uneven winding, or inner layer indentation in the initial winding of the battery cell.

[0053] Furthermore, arranging the foil area 121 within the inner ring of the battery cell also provides functional area separation and process buffering. Since this area typically does not participate in the main electrochemical reaction, it can serve as a tab lead-out, soldering pre-reservation area, or insulation transition area, helping to improve the wiring clarity and thermal isolation of the overall battery cell structure. Combined with the curing characteristics of the support layer 30 after hot-pressing and shaping, it can further enhance the shape retention, thermal stability, and assembly reliability of the inner ring of the battery cell.

[0054] In some embodiments, the support layer 30 has a chamfered edge 32 structure on its sidewall near the edge of the active material layer 20. That is, in the boundary region adjacent to the support layer 30 and the active material layer 20, a gradually transitioning chamfered edge is formed by designing a certain angle or curved surface at the edge of the support layer 30. The chamfered edge 32 structure can be a linear chamfered edge 32 or a curved surface transition, and its specific angle or radius of curvature can be adjusted according to the thickness of the support layer 30.

[0055] In this embodiment, by setting a chamfered 32 structure, the edge of the support layer 30 can form a smooth transition at the interface with the active material layer 20. This reduces the geometric discontinuity caused by structural abrupt changes and improves the uniformity of stress distribution at the interface, thereby effectively alleviating the interlayer extrusion problem during hot pressing or winding and reducing the risk of cracking, chipping, or curling at the edge of the active layer. Furthermore, the chamfered 32 structure also helps improve the consistency of the pressure head contact during hot pressing of the electrode sheet. Since the support layer 30 is a thermosetting material, its hot pressing quality is affected by the uniformity of the pressure distribution of the pressure head; if the edge is a right-angle protrusion, the pressure head cannot fit well with it during hot pressing, forming a hot pressing dead angle. However, with the chamfered 32 structure, the pressure head can form continuous contact with the surface of the support layer 30, improving heat conduction efficiency and the consistency of hardening.

[0056] The embodiments of this application also provide a battery cell structure, which includes a separator and an electrode sheet with a support layer 30. The separator is disposed on the second surface 12 side of the electrode sheet, that is, on the side of the electrode sheet with the foil area 121 and the support layer 30, and plays the role of electrical isolation and interface stabilization in the winding or stacking structure.

[0057] Furthermore, the use of terms such as "first" and "second" in this application is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed in this application.

[0058] The above description is merely a preferred embodiment of this application and does not limit the patent scope of this application. Any equivalent structural transformations made based on the content of this application's specification and drawings under the concept of this application, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this application.

Claims

1. An electrode sheet, characterized in that, include: A current collector having a first surface and a second surface disposed opposite to each other, the second surface having a coating area and a foil area; An active material layer is disposed on the first surface and the coating area; A support layer is coated on the foil area, and the active material layer is disposed on the first surface in the area corresponding to both the coating area and the foil area.

2. The electrode sheet according to claim 1, characterized in that, The support layer extends in a direction away from the coating area, and the length of the support layer is less than or equal to the length of the foil area.

3. The electrode sheet according to claim 1, characterized in that, The width of the support layer is d1, and the width of the foil area is d2, satisfying the relationship: 0.5d2≤d1≤d2.

4. The electrode sheet according to claim 3, characterized in that, The centerline of the support layer along its length is collinear with the centerline of the foil area.

5. The electrode sheet according to claim 1, characterized in that, The thickness of the support layer is t1, and the thickness of the active material layer is t2, satisfying the relationship: 0.6t2≤t1≤t2.

6. The electrode sheet according to claim 2, characterized in that, The support layer includes multiple support parts, and the multiple support parts are distributed at equal intervals.

7. The electrode sheet according to claim 6, characterized in that, The interval between adjacent support portions is h, and the width of the foil area is d2, satisfying the relationship: 0.1d2≤h≤0.3d2.

8. The electrode sheet according to any one of claims 1 to 7, characterized in that, The foil area is located in the inner circle of the electrode sheet after winding.

9. The electrode sheet according to any one of claims 1 to 7, characterized in that, The support layer has a chamfered structure on its sidewalls near the edge of the active material layer.

10. A battery cell structure, characterized in that, It includes a diaphragm and an electrode sheet as described in any one of claims 1-9, wherein the diaphragm is disposed on the second surface side of the electrode sheet.

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