Lithium battery roll core

Abstract

This invention provides a lithium battery core, which is a multi-layer structure formed by winding a composite material. The composite material includes stacked electrodes and separators. The composite material is wound to form multiple curved sections, and at least some of the curved sections have cutting structures extending at least along the length direction of the composite material. The cutting structures penetrate the electrodes at the curved sections along the thickness direction of the curved sections. In the extension direction of the curved sections, the ratio of the maximum extension length of the cutting structures on the curved sections to the length of the electrodes at the curved sections is A. In the direction from the outer layer to the inner layer of the lithium battery core, multiple A values ​​show a decreasing trend. Using this solution, the cutting structures stop the propagation of cracks on the electrodes at the curved sections, preventing the cracks from continuously extending along the width direction of the composite material and causing the composite material to break. By limiting the variation of the proportion A of the cutting structures on the electrodes at different curved sections, it is beneficial to reduce the formation of ineffective cutting structures and make the crack prevention more targeted.

Description

Technical Field

[0001] This utility model relates to the field of battery technology, and more specifically, to a lithium battery core. Background Technology

[0002] Currently, lithium battery cells are typically manufactured using a winding process, which involves stacking the electrode sheets and separators and then winding them together as a whole.

[0003] During processing, cracks may form on the electrode, especially at both ends along its length. In the fabrication of wound lithium-ion battery cores, cracks on the electrode corresponding to the curved section of the winding are susceptible to extension by winding force and expansion stress, leading to tearing of the electrode and ultimately, breakage and failure of the electrode at the entire curved section.

[0004] Furthermore, due to the different stress and bending conditions of each bending section, the number and distribution of cracks extending from the corresponding electrode at each bending section due to winding force and expansion stress also differ. The closer to the outermost bending section, the higher the proportion of cracks susceptible to bending and stress extension in the total number of cracks on that bending section. Moreover, cracks susceptible to bending and stress extension usually concentrate in the same area. The closer to the outermost bending section, the more areas formed by these susceptible cracks, or the longer these areas extend along the length of the bending section; that is, the higher the proportion of these susceptible crack-formed areas along the length of the bending section. Therefore, it is necessary to design the cutting structure on the electrode at each bending section specifically to balance structural strength, processing cost, and crack propagation prevention. Utility Model Content

[0005] This invention provides a lithium battery cell that designs and cuts a structure based on the curved sections located in different layers, and solves the problem that cracks easily extend under the action of winding force and expansion stress, causing the electrode sheets at that location to break.

[0006] To address the aforementioned problems, this utility model provides a lithium battery core, which is a multi-layer structure formed by winding a composite. The composite includes stacked electrodes and separators, and the composite is wound to form multiple curved sections. At least some of the curved sections are provided with cutting structures extending at least along the length direction of the composite. The cutting structures penetrate the curved sections along the thickness direction. In the extension direction of the curved sections, the ratio of the maximum extension length of the cutting structures on the curved sections to the length of the curved sections is A. In the direction from the outer layer to the inner layer of the lithium battery core, multiple A values ​​show a decreasing trend.

[0007] Furthermore, 1 / 3 ≤ A ≤ 1.

[0008] Furthermore, in the direction from the outer layer to the inner layer of the lithium battery core, multiple A's gradually decrease; or, at least one A' is a group and the A's in the same group are the same, and multiple groups of A's are distributed sequentially and gradually decrease.

[0009] Furthermore, the central region of the cut structure at least partially overlaps with the central region of the curved section.

[0010] Furthermore, the cutting structure on any curved segment includes at least one cutting segment. In the case of multiple cutting segments, the multiple cutting segments are distributed at intervals along the length direction and / or the width direction of the curved segment.

[0011] Furthermore, when there are multiple cut segments, for any one curved segment, the projections of the multiple cut segments onto a plane perpendicular to the width direction of the curved segment are spaced apart or at least partially overlap, and the length of the projections of the multiple cut segments onto a plane perpendicular to the width direction of the curved segment is the maximum extension length of the cut structure in the extension direction of the curved segment.

[0012] Furthermore, when there are multiple cut segments, each of the multiple cut segments is different from the others or at least partially the same.

[0013] Furthermore, the cutting segment is a cut with a cutting area, and / or, the cutting segment is a slit without a cutting area.

[0014] Furthermore, the cut is a strip-shaped opening extending along the length of the composite; the width of the cut is constant; or, the width of the cut at least partially varies along the length of the curved section.

[0015] Furthermore, the slit extends in a straight line, bends, or meanders along the length of the composite; the cut extends in a straight line, bends, or meanders along the length of the composite.

[0016] Furthermore, the outermost curved section of the lithium battery core is the first curved section, the innermost curved section of the lithium battery core is the second curved section, the curved section adjacent to the first curved section of the lithium battery core is the third curved section, and the curved section adjacent to the second curved section of the lithium battery core is the fourth curved section. Cutting structures are provided on the first, second, third, and fourth curved sections.

[0017] Furthermore, the lithium battery core also includes tabs, which are disposed on the composite and located in the middle region of the lithium battery core.

[0018] The present invention provides a lithium battery core, which is a multi-layer structure formed by winding a composite. The composite includes stacked electrodes and separators. The composite is wound to form multiple curved sections. At least some of the curved sections are provided with cutting structures extending at least along the length direction of the composite. The cutting structures penetrate the electrodes at the curved sections along the thickness direction of the curved sections. In the extension direction of the curved sections, the ratio of the maximum extension length of the cutting structures on the curved sections to the length of the electrodes at the curved sections is A. In the direction from the outer layer to the inner layer of the lithium battery core, the ratios of A and A tend to decrease.

[0019] This solution, through the cutting structure, can stop the extension of cracks on the electrode sheets at the bending section. Specifically, it mainly stops the extension of cracks on the electrode sheets (including positive and negative electrode sheets) at the bending section during the winding or use of lithium battery cores due to the winding force and the expansion stress during use. This prevents the cracks from continuing to extend along the width of the composite, causing the composite to break, which in turn affects the performance of the lithium battery core or causes damage to the lithium battery core, thus ensuring the reliability and stability of the lithium battery core in use. Furthermore, by limiting the variation of the proportion A of the cut structure on the electrode at different bending sections, it is possible to avoid situations where the proportion of cracks that are easily affected by bending and stress extending in the outermost bending section is higher than the total number of cracks in that bending section, and the proportion of the area formed by such easily affected cracks in the length of the bending section is higher. In such cases, the cut structure on the electrode at the innermost bending section is more prone to ineffective areas, and the more or longer the ineffective areas are, the more processing waste occurs, affecting the functionality and structural strength of the bending section. This helps to reduce the formation of ineffective cut structures, and the blocking of cracks at different layers of bending sections is more targeted. It is also beneficial to reduce processing costs, structural strength, and ensure the performance of lithium battery cores while achieving tear protection for each bending section. Attached Figure Description

[0020] The accompanying drawings, which form part of this specification, are used to provide a further understanding of this utility model. The illustrative embodiments and descriptions of this utility model are used to explain this utility model and do not constitute an undue limitation thereof. In the drawings:

[0021] Figure 1 A schematic diagram of the structure of a lithium battery core provided in an embodiment of the present invention is shown;

[0022] Figure 2 It shows Figure 1 Front view of a lithium battery core;

[0023] Figure 3 It shows Figure 2 AA section view;

[0024] Figure 4 It shows Figure 2 BB cross-sectional view;

[0025] Figure 5 It shows Figure 1 A schematic diagram of the electrode structure of a lithium battery core.

[0026] The above figures include the following reference numerals:

[0027] 1. Complex; 01. Bending segment; 011. First bending segment; 012. Second bending segment; 013. Third bending segment; 014. Fourth bending segment;

[0028] 10. Electrode; 101. Cutting structure; 1011. Cutting segment;

[0029] 20. Diaphragm;

[0030] 30. Pole tabs. Detailed Implementation

[0031] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present utility model or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present utility model without creative effort are within the scope of protection of the present utility model.

[0032] like Figures 1 to 5 As shown, this utility model provides a lithium battery core, which is a multi-layer structure formed by winding a composite 1. The composite 1 includes stacked electrode sheets 10 and separators 20. The composite 1 is wound to form multiple curved sections 01. At least some of the curved sections 01 are provided with cutting structures 101 extending at least along the length direction of the composite 1. The cutting structures 101 penetrate the electrode sheets 10 at the curved section 01 along the thickness direction of the curved section 01. In the extension direction of the curved section 01, the ratio of the maximum extension length of the cutting structures 101 on the curved section 01 to the length of the electrode sheets 10 at the curved section 01 is A. In the direction from the outer layer to the inner layer of the lithium battery core, the multiple A values ​​show a decreasing trend.

[0033] In this embodiment, the cutting structure 101 can stop the extension of cracks on the electrode 10 at the bending section 01. Specifically, it mainly stops the extension of cracks on the electrode 10 (including positive and negative electrode sheets) at the bending section 01 due to the winding force and expansion stress during use when the lithium battery core is wound or used. This prevents the cracks from continuing to extend along the width direction of the composite 1, causing the composite 1 to break, which would affect the performance of the lithium battery core or cause damage to the lithium battery core, thus ensuring the reliability and stability of the lithium battery core. Furthermore, by limiting the variation of the proportion A of the cut structure 101 on the electrode 10 at different bending sections 01, it is possible to avoid the situation where the proportion of cracks that are easily affected by bending and stress extending on the outermost bending section 01 is higher than the total number of cracks on the bending section 01, and the proportion of the area formed by such easily affected cracks in the length of the bending section 01 is higher. In such cases, the cut structure 101 on the electrode 10 at the innermost bending section 01 is more likely to have ineffective areas, and the more or longer the ineffective areas are, the more processing waste will occur, affecting the functionality and structural strength of the bending section. This is conducive to reducing the formation of ineffective cut structures 101, and the blocking of cracks at different layers of bending sections is more targeted. It is also conducive to reducing processing costs, structural strength and ensuring the performance of lithium battery core while achieving tear protection for each bending section 01.

[0034] It is understood that the cutting structure 101 in this embodiment is designed for specific purposes. Its main design objective is to provide a cutting structure 101 of appropriate length at locations or areas prone to extending tearing to stop the extension of cracks (i.e., for any electrode 10 corresponding to any bend segment 01, a cutting structure 101 of suitable length is provided to stop each location or area prone to extending tearing). Alternatively, it can selectively cover multiple locations or areas prone to extending tearing with a cutting structure 101 of appropriate length to stop the extension of cracks (i.e., for any electrode 10 corresponding to any bend segment 01, multiple locations or areas prone to extending tearing are stopped by the same cutting structure 101 of suitable length). In some other embodiments, the length of the cutting structure 101 can be the same as the length of the electrode 10 corresponding to the bend segment 01. While this arrangement facilitates improving the processing efficiency of the cutting structure 101, it is not conducive to reducing the number of ineffective cutting structures 101.

[0035] The electrode 10 includes a current collector and an active material layer coated on both sides of the current collector. The cut segment 1011 includes a first cut segment disposed on the current collector and a second cut segment disposed on the active material layer. In this embodiment, the first cut segment and the second cut segment are opposite each other and are identical.

[0036] like Figure 5As shown, the outermost curved section 01 of the lithium battery core is the first curved section 011, the innermost curved section 01 of the lithium battery core is the second curved section 012, the curved section 01 adjacent to the first curved section 011 of the lithium battery core is the third curved section 013, and the curved section 01 adjacent to the second curved section 012 of the lithium battery core is the fourth curved section 014. Cutting structures 101 are provided on the first curved section 011, the second curved section 012, the third curved section 013, and the fourth curved section 014. In this embodiment, the cutting structures 101 at the first curved section 011 and the second curved section 012 are mainly to prevent the composite 1 from breaking due to compressive and tensile stress, while the cutting structures 101 at the third curved section 013 and the fourth curved section 014 are to prevent the composite 1 from breaking due to shear stress.

[0037] Preferably, 1 / 3 ≤ A ≤ 1. This setting avoids the situation where the cutting structure 101 on it is not effective in preventing the extension of cracks when A < 1 / 3.

[0038] Specifically, such as Figure 5 As shown, in the direction from the outer layer to the inner layer of the lithium battery core, multiple A's gradually decrease, and the A's of each adjacent pair of layers are different. Alternatively, in other embodiments not shown in the figure, at least one A' is grouped together, and the A's within the same group are the same. Multiple groups of A's are distributed sequentially and gradually decrease. In this case, adjacent pairs of layers may have the same A's, but the overall trend of the multiple groups of A's is still a gradual decrease from the outer layer of the lithium battery core towards the inner layer. This arrangement facilitates the operator in designing the required proportion of A's and the required cutting structure 101 according to the actual situation.

[0039] It is understandable that the crack in the central region of the bending segment 01 is most susceptible to propagation under stress, and the central region of the cutting structure 101 at least partially overlaps with the central region of the bending segment 01. This arrangement facilitates the processing of the cutting structure 101 while ensuring its effectiveness in preventing cracks.

[0040] Furthermore, any cutting structure 101 on the curved segment 01 includes at least one cutting segment 1011. When there are multiple cutting segments 1011, they are spaced apart along the length direction and / or width direction of the curved segment 01. This arrangement allows for tear-resistant design of the electrode 10 corresponding to different positions on the curved segment 01 using multiple cutting segments 1011. Optionally, in other embodiments not shown in the figures, the multiple cutting segments 1011 are different from each other or at least partially identical. In this embodiment, each cutting structure 101 includes two identical cutting segments 1011, which are spaced apart along the width direction of the curved segment 01, facilitating processing and improving processing convenience and efficiency.

[0041] In this embodiment, for any curved segment 01, the projections of multiple cut segments 1011 onto a plane perpendicular to the width direction of the curved segment 01 are spaced apart or at least partially overlap. The length of the projections of the multiple cut segments 1011 onto the plane perpendicular to the width direction of the curved segment 01 is the maximum extension length of the cut structure 101 in the extension direction of the curved segment 01. In this embodiment, the projections of two cut segments 1011 on the same curved segment 01 onto the plane perpendicular to the width direction of the curved segment 01 are completely overlapping. In other embodiments not shown in the figures, the projections of the multiple cut segments 1011 onto the plane perpendicular to the width direction of the curved segment 01 are partially overlapping. For example, there are four cut segments 1011, which are distributed along the length direction of the curved segment 01 and spaced apart along the width direction of the curved segment 01. In the length direction of the curved segment 01, the projections of any two adjacent cut segments 1011 onto the plane perpendicular to the width direction of the curved segment 01 are at least partially overlapping. This setup also ensures that the extension of cracks at different locations along the length of the bending segment 01 is stopped and covered. At the same time, it helps to reduce the length design of each first cutting segment and avoids the situation where the invalid cutting segment of the first cutting segment is too large.

[0042] Preferably, the cutting segment 1011 is a cut with a cutting area, and / or, the cutting segment 1011 is a slit without a cutting area. In this embodiment, the cutting segment 1011 is a slit, which is beneficial to further improve the processing efficiency of the cutting structure 101.

[0043] In this embodiment, the slit extends linearly along the length of the electrode 10, facilitating rapid processing. In other embodiments not shown, the slit may also extend in a bent or meandering manner along the length of the electrode 10 to increase the actual stopping length of the slit. Bending and meandering extensions are not entirely the same; bending emphasizes a clear bending point during the extension process, while meandering emphasizes a continuous, winding path without clear turning points, but with a relatively curved overall trajectory.

[0044] In other embodiments not shown in the figures, the cut segment 1011 can be a slit with a cut area. A slit is more effective at stopping crack propagation than a kerf, but it is more difficult to process and may have a greater impact on the structural strength or performance of the curved segment 01. Further, the slit is a strip-shaped opening extending along the length direction of the electrode 10; the width of the slit is constant; or, the width of the slit at least partially varies along the length direction of the curved segment 01. This arrangement allows operators to design slits of suitable shape and size according to actual conditions, ensuring reliable stopping of crack propagation at different locations along the length direction of the curved segment 01. The slit extending in a straight line, bending, or meandering along the length direction of the composite 1 is beneficial in balancing processing convenience and actual stopping length.

[0045] Preferably, when the cutting section 1011 is a slit, the proportional relationship between the area of ​​the slit and the area of ​​the electrode 10 at the bending section 01 can also be limited.

[0046] The lithium battery core also includes tabs 30. Preferably, the tabs 30 are disposed on the electrode sheet 10 and located in the middle region of the lithium battery core. Compared with the conventional structure where the tabs 30 are located at one end of the electrode sheet 10, the centrally positioned tabs 30 (first tab and second tab) of this embodiment reduce the battery's internal resistance. In the centrally positioned tab structure, electrons diffuse from the middle of the tabs 30 to both ends, shortening the current path and reducing the battery's internal resistance. Furthermore, with the tabs 30 centrally positioned, its rate performance is close to that of batteries using a stacked process. The performance difference is not significant at low-rate discharge, but its advantages are obvious at high-rate discharge, supporting larger charge and discharge currents, enabling fast charging and high-power discharge, meeting the needs of some high-rate electrical devices. Moreover, due to the reduced internal resistance, less heat is generated during high-rate charge and discharge, and the temperature rise is reduced, thereby improving battery safety and lifespan. On the other hand, this structure is relatively regular. When the battery is subjected to external impact, the tab 30 is located in the middle, resulting in better stress distribution. Compared to a structure where the tab 30 is located on one side, the centrally located tab 30 structure is more stable and less prone to short circuits, fires, or other problems caused by deformation or displacement, thus reducing the risk of cell bulging, combustion, or even explosion. Furthermore, the centrally located tab 30 effectively reduces the area of ​​the empty foil region at the tab 30 welding point, thereby effectively improving the battery's energy density.

[0047] In summary, this utility model provides a lithium battery core that improves the performance of the lithium battery cell through the central placement of the tabs. The cutting structure 101 prevents the extension of cracks in the electrode sheets 10 (including positive and negative electrodes) at the bending section 01, avoiding the continuous extension of cracks along the width direction of the composite 1, which could lead to fracture of the composite 1 and consequently affect the performance or damage of the lithium battery core, thus ensuring the reliability and stability of the lithium battery core. Furthermore, by limiting the variation of the proportion A of the cutting structure 101 on the electrode sheets 10 at different bending sections 01, the formation of ineffective cutting structures 101 is reduced, making the crack prevention more targeted. This helps to reduce processing costs, structural strength, and performance while achieving tear protection for each bending section 01.

[0048] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to the present invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0049] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of this invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0050] In the description of this utility model, it should be understood that the directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description. Unless otherwise stated, these directional terms 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 on the scope of protection of this utility model. The directional terms "inner" and "outer" refer to the inner and outer contours of each component itself.

[0051] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0052] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be construed as limiting the scope of protection of this utility model.

[0053] The above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A lithium battery core, wherein the lithium battery core is a multi-layer structure formed by winding a composite (1), the composite (1) comprising stacked electrode sheets (10) and separators (20), the composite (1) being wound to form a plurality of curved segments (01), characterized in that, At least a portion of the curved section (01) is provided with a cutting structure (101) extending at least along the length direction of the composite (1), the cutting structure (101) penetrating the electrode (10) at the curved section (01) along the thickness direction of the curved section (01); In the extension direction of the curved section (01), the ratio of the maximum extension length of the cut structure (101) on the curved section (01) to the length of the electrode (10) at the curved section (01) is A; In the direction from the outer layer to the inner layer of the lithium battery core, multiple A values ​​show a decreasing trend.

2. The lithium battery core according to claim 1, characterized in that, 1 / 3≤A≤1。 3. The lithium battery jelly-roll of claim 1, wherein, In the direction from the outer layer to the inner layer of the lithium battery core Multiple A's gradually decrease; Alternatively, at least one A is in a group and the A in the same group are the same, and multiple groups of A are distributed sequentially and gradually decrease in size.

4. The lithium battery jelly-roll of claim 1, wherein, The central region of the cut structure (101) at least partially overlaps with the central region of the curved segment (01).

5. The lithium battery jelly-roll of claim 1, wherein, The cutting structure (101) on any of the curved segments (01) includes at least one cutting segment (1011). If there are multiple cutting segments (1011), the multiple cutting segments (1011) are distributed at intervals along the length direction of the curved segment (01) and / or the width direction of the curved segment (01).

6. The lithium battery jelly-roll of claim 5, wherein, When there are multiple cut segments (1011), for any one of the curved segments (01), The projections of the plurality of cut segments (1011) onto a plane perpendicular to the width direction of the curved segment (01) are spaced apart or at least partially overlap, and the length of the projections of the plurality of cut segments (1011) onto a plane perpendicular to the width direction of the curved segment (01) is the maximum extension length of the cut structure (101) in the extension direction of the curved segment (01).

7. The lithium battery jelly-roll of claim 5, wherein, When there are multiple cutting segments (1011), each of the multiple cutting segments (1011) is different from the others or at least partially the same.

8. The lithium battery jelly-roll of claim 5, wherein, The cutting segment (1011) is a cut with a cutting area, and / or the cutting segment (1011) is a slit without a cutting area.

9. The lithium battery jelly-roll of claim 8, wherein, The cut is a strip-shaped opening extending along the length direction of the composite (1); The width of the cut is constant; Alternatively, the width of the cut may at least partially change along the length of the curved segment (01).

10. The lithium battery core according to claim 8, characterized in that, The cut extends in a straight line, bends, or meanders along the length of the composite (1); The cut extends in a straight line, bends, or meanders along the length of the composite (1).

11. The lithium battery jelly-roll of claim 1, wherein, The outermost curved segment (01) of the lithium battery core is the first curved segment (011), the innermost curved segment (01) of the lithium battery core is the second curved segment (012), the curved segment (01) adjacent to the first curved segment (011) of the lithium battery core is the third curved segment (013), and the curved segment (01) adjacent to the second curved segment (012) of the lithium battery core is the fourth curved segment (014). The cutting structure (101) is provided on the first curved segment (011), the second curved segment (012), the third curved segment (013), and the fourth curved segment (014).

12. The lithium battery jelly-roll of claim 1, wherein, The lithium battery core also includes a tab (30), which is disposed on the composite (1) and located in the middle region of the lithium battery core.

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