Electrode sheet and roll core battery

Abstract

An electrode sheet, comprising a current collector (1) and active coatings (2) coated on two sides of the current collector (1). An active coating (2) on at least one side of the current collector (1) is provided with a plurality of first regions (3) in a first direction, and a region gap between the adjacent first regions (3) is Dm. A plurality of grooves (31) are formed in each first region (3). The distance between the adjacent grooves (31) in a direction perpendicular to the long axis of the grooves (31) is Dt, Dt is greater than Dm, and the first direction is the length direction or the width direction of the electrode sheet.

Description

Electrode and core battery Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a pole piece, and also to a wound core battery having the pole piece. Background Art

[0002] With the development of technology, consumers have put forward higher demands for battery energy density and rate. Currently, the industry's fast charging inevitably sacrifices a certain amount of energy density, so the new generation of polymer lithium-ion batteries needs to take into account both high rate and high energy density.

[0003] During the roller-pressing process, the negative electrode active coating on the sides of the negative electrode sheet that are in direct contact with the rollers becomes denser and less porous. This in turn lengthens the electrolyte migration path within the negative electrode sheet, which in turn reduces the negative electrode sheet's rate performance. Furthermore, the potential of the negative electrode sheet's surface closest to the separator is lower, leading to uneven polarization and electrolyte concentration, resulting in low negative electrode sheet utilization and a greater risk of lithium plating.

[0004] Summary of the Invention

[0005] In view of this, the purpose of this application is to provide a pole piece and a core battery, in which a plurality of slotted first areas are provided on the pole piece, which can reduce the risk of lithium plating and improve the utilization rate of the negative pole piece.

[0006] To achieve the above objectives, this application provides the following technical solutions.

[0007] In a first aspect, a pole piece is provided, comprising a current collector and an active coating applied on both sides of the current collector, wherein:

[0008] The active coating on at least one side of the current collector is provided with a plurality of first regions along a first direction, and a regional gap Dm is set between adjacent first regions;

[0009] A plurality of grooves are provided in each first region, and a distance between adjacent grooves in a direction perpendicular to the long axis of the groove is Dt, where Dt>Dm; wherein the first direction is the length direction or the width direction of the pole piece.

[0010] Optionally, in the above-mentioned pole piece, 1.1Dm<Dt<8Dm.

[0011] Optionally, in the above-mentioned pole piece, 1.2Dm<Dt<3Dm.

[0012] Optionally, in the above-mentioned pole piece, along a second direction perpendicular to the first direction, the size of the first region is W1, the size of the pole piece is W2, and 0.85W2<W1<W2.

[0013] Optionally, in the above-mentioned pole piece, a line connecting the ends of the grooves on the same side in the first region is a straight line, and an angle between the straight line and the first direction is θ, 0°≤θ≤90°.

[0014] Optionally, in the above-mentioned pole piece, an arrangement direction of adjacent first regions is the same as an arrangement direction of the grooves in one of the first regions.

[0015] Optionally, in the above-mentioned pole piece, adjacent first regions are arranged at intervals along a second direction perpendicular to the first direction, and the multiple grooves in one first region are arranged at intervals along the first direction.

[0016] Optionally, adjacent first regions are spaced apart along the first direction, and the plurality of grooves within one first region are spaced apart along a second direction perpendicular to the first direction.

[0017] Optionally, in the above-mentioned pole piece, along a second direction perpendicular to the first direction, a distance between the groove in the first region close to the edge of the pole piece and the edge of the pole piece is Dp, and 1.1Dm≤Dp≤1.4Dm.

[0018] Optionally, in the above-mentioned pole piece, the dimension of the groove in the short axis direction is W3, 1 / 5<W3 / Dm<1 / 2.

[0019] Optionally, in the above-mentioned pole piece, along the first direction, the size of the first region is L1, 50Dm≤L1≤400Dm.

[0020] Optionally, in the above-mentioned pole piece, along a second direction perpendicular to the first direction or the first direction, the grooves in adjacent first regions are staggered.

[0021] Optionally, in the above-mentioned pole piece, along the second direction, the misalignment dimension between adjacent first regions is x, 50 μm≤x≤200 μm.

[0022] Optionally, 100 μm ≤ Dm ≤ 300 μm.

[0023] A roll core battery includes a first pole piece, a second pole piece and a diaphragm located between the first pole piece and the second pole piece, the first pole piece and / or the second pole piece are the above-mentioned pole pieces, the first pole piece, the second pole piece and the diaphragm are stacked and wound to form a roll core, and the roll core includes a bent section and a straight section.

[0024] Optionally, in the above-mentioned spiral wound battery,

[0025] In the same straight section, along the first direction, the number of regional gaps is N1,

[0026] In the same bending section, along the first direction, the number of the regional gaps is N2, N1>N2≥1.

[0027] Optionally, in the above-mentioned wound core battery, two adjacent first regions are respectively located in the straight section and the bent section, and the regional gap between the two is located in the bent section.

[0028] As can be seen from the above technical solution, the pole piece and wound core battery provided by this application, by providing a plurality of slotted first areas on the active coating of at least one side of the current collector in the length direction of the pole piece, reduces the density of the active coating on the side of the pole piece that is in direct contact with the roller during the pole piece rolling process, which is equivalent to constructing an oriented groove fast ion channel on the surface of the pole piece, solving the problem of the electrolyte migration path in the negative electrode piece becoming longer, expanding the lithium precipitation window, reducing the risk of lithium precipitation, and improving the utilization rate of the negative electrode piece. At the same time, the potential of the side of the negative electrode piece close to the diaphragm is increased, the cycle performance of the battery is improved, the electrolyte concentration is uniform, and the utilization rate and energy density of the negative electrode piece are increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0030] FIG1 is a schematic structural diagram of a winding core provided in an embodiment of the present application;

[0031] FIG2 is a cross-sectional view of a pole piece provided in an embodiment of the present application;

[0032] FIG3 is a first structural diagram of a pole piece provided in an embodiment of the present application;

[0033] FIG4 is a second structural diagram of a pole piece provided in an embodiment of the present application;

[0034] FIG5 is a third structural diagram of a pole piece provided in an embodiment of the present application;

[0035] FIG6 is a fourth structural diagram of a pole piece provided in an embodiment of the present application;

[0036] FIG7 is a fifth structural diagram of a pole piece provided in an embodiment of the present application;

[0037] FIG8 is a sixth structural diagram of the electrode provided in an embodiment of the present application.

[0038] in:

[0039] 1-current collector, 2-active coating, 3-first region, 31-groove, 41-bend section, 42-straight section,

[0040] 5- Empty foil area. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0042] In the description of this application, it should be noted that the terms "center", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "inner" and "outer" indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the product of the application is usually placed when in use. They 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, be constructed and operate in a specific orientation. Therefore, they should not be understood as limiting this application. In addition, the terms "first", "second" and "third" are used for descriptive purposes only and should not be understood as indicating or implying relative importance.

[0043] As shown in FIG. 1 to FIG. 8 , an embodiment of the present application provides a pole piece.

[0044] First, the pole piece includes a current collector 1 and an active coating 2 coated on both sides of the current collector 1 (see Figure 2 for details). The active coating 2 on at least one side of the current collector 1 is provided with a plurality of first regions 3 along a first direction, and the regional gap between adjacent first regions 3 is Dm. Each first region 3 is provided with a plurality of grooves 31, and the distance between adjacent grooves 31 in the direction perpendicular to the long axis of the groove 31 is Dt, and Dt>Dm. In this way, it is ensured that the length of the groove 31 is close to the maximum value, the area of ​​the groove 31 is maximized, and there are many lithium ion reaction sites, which can improve the battery dynamics performance. It should be noted that, as shown in Figure 3, the first direction can be, for example, the length direction (x) of the pole piece, or the width direction (y) of the pole piece.

[0045] It can be seen that the pole piece provided in the embodiment of the present application reduces the density of the active coating 2 on the side of the pole piece that is in direct contact with the pressing roller during the pole piece rolling process by providing the active coating 2 on at least one side of the current collector 1 with a plurality of grooved first areas 3 in the first direction. This is equivalent to constructing an oriented groove fast ion channel on the surface of the pole piece, solving the problem of the lengthened migration path of the electrolyte in the negative electrode pole piece, expanding the lithium plating window, reducing the risk of lithium plating, and improving the utilization rate of the negative electrode pole piece. At the same time, the potential of the side of the negative electrode pole piece close to the diaphragm is increased, the cycle performance of the battery is improved, the electrolyte concentration is uniform, and the utilization rate and energy density of the negative electrode pole piece are increased.

[0046] During specific implementation, 1.1Dm<Dt<8Dm. It should be noted that with a ratio of 1.1Dm<Dt<8Dm, the risk of lithium plating of the electrode is lower. It should be noted that the optimal ratio is 1.2Dm< Dt<3Dm. However, it is not limited to this. The ratio of Dt and Dm can be specifically designed by those skilled in the art according to actual needs. A smaller Dm can ensure that the electrode slot area is maximized, while reducing the adhesion between the electrode and the diaphragm in the bending section of the winding core, ensuring electrolyte infiltration while improving the stability of the electrode.

[0047] In a specific implementation, as shown in Figures 3 to 8 , along a second direction perpendicular to the first direction, the size of the first region 3 is W1, and the size of the electrode sheet is W2, with 0.85W2 < W1 < W2. It should be noted that, as shown in Figure 3 , the second direction is perpendicular to the first direction and can be, for example, the width (y) or length (x) direction of the electrode sheet. Along the second direction, the first region 3 approaches the process maximum, increasing the total surface area of ​​the multiple grooves 31 in the first region 3, maintaining uniform stress across the electrode sheet, and enhancing the mechanical stability of the electrode sheet. This prevents excessive expansion of certain areas during long cycling, thereby improving the battery's cycle life. Furthermore, this ensures the battery's mechanical stability, preventing stress concentration in the electrode sheet caused by a too small W1, thereby increasing material damage and fatigue risk. It also prevents excessive W1, which can reduce electrode sheet utilization and lower the battery's energy density. Therefore, matching W1 and W2 achieves superior mechanical stability. In addition, if W1 is too small, the transmission of ions in the battery will be restricted, resulting in a decrease in the battery's charge and discharge performance. When W1 is too large, it may cause uneven distribution of active materials, affecting the battery's energy density and cycle life. Matching W1 and W2 can provide more ion channels, reduce the resistance to ion transmission, improve the battery's charge and discharge efficiency and power output, and control the distribution of active materials, thereby improving the battery's performance and stability. In summary, 0.85W2<W1<W2 can achieve better mechanical stability, ion transmission efficiency and uniform distribution of active materials, thereby improving the performance and cycle life of lithium-ion batteries.

[0048] In a specific implementation, the line connecting the ends of the grooves 31 on the same side in the first region 3 is a straight line, and the angle between the straight line and the first direction is θ, where 0°≤θ≤90°. This prevents short lines in the grooves 31 during electrode routing and avoids uneven parameters in the grooves 31, which helps ensure the quality of the grooves 31 and improves electrolyte retention. It should be noted that electrode routing refers to the process by which current passes through the electrode. As ions in the electrolyte react, an oxide layer or a reduction layer gradually grows on the electrode surface. Short lines in grooves 31 refer to the phenomenon in which current bypasses the electrolyte and directly connects between the grooves 31 provided on the electrode of an electrolytic capacitor. Short lines in grooves 31 are typically caused by insufficient gaps between the grooves 31. The purpose of the grooves 31 is to increase the contact area between the electrode and the electrolyte and provide sufficient electrolyte storage to promote electrolyte transmission and reaction. However, if the gaps between the grooves 31 are too small, the current may bypass the electrolyte during passage, forming a direct current path between the grooves 31, resulting in a short circuit. The short lines in grooves 31 can cause the contact between part of the electrode surface and the electrolyte to fail, reducing the effective electrode area, thereby reducing the capacitance of the capacitor. The current bypasses the electrolyte and passes directly through the connection path between the grooves 31, weakening the transmission and reaction capabilities of the electrolyte. This may affect the charge storage and release capacity of the capacitor, resulting in performance degradation. Because the short lines in grooves 31 create additional current paths, the current will flow through the connection paths between the grooves 31, increasing the internal resistance and energy loss of the capacitor.

[0049] In specific implementation, as shown in FIG3 to FIG5 , the line connecting the ends of the grooves 31 on the same side in the first region 3 is a straight line, and the angle θ between the straight line and the length direction of the pole piece is 90 degrees.

[0050] In specific implementation, as shown in FIG6 to FIG8 , the line connecting the ends of the grooves 31 on the same side in the first region 3 is a straight line, and the angle θ between the straight line and the length direction of the pole piece is 0 degrees.

[0051] In some implementations, the arrangement direction of adjacent first regions 3 is the same as the arrangement direction of the grooves within the first regions 3 , which facilitates the electrode grooving process.

[0052] In some implementations, adjacent first regions 3 are spaced apart along the second direction of the pole piece, and the grooves within one first region 3 are spaced apart along the first direction of the pole piece; or, adjacent first regions 3 are spaced apart along the first direction of the pole piece, and the grooves within one first region 3 are spaced apart along the second direction of the pole piece. In one example, adjacent first regions 3 are spaced apart along the first direction of the pole piece, and the grooves within the first region extend along the first direction of the pole piece; in another example, adjacent first regions 3 are spaced apart along the second direction of the pole piece, and the grooves within the first region extend along the second direction of the pole piece.

[0053] In some embodiments, along a second direction perpendicular to the first direction, the distance between the groove near the edge of the electrode in the first region 3 and the edge of the electrode is Dp, and 1.1Dm≤Dp≤1.4Dm. In this way, when the empty foil area 5 is provided on both sides along the second direction (see Figures 3, 4, 6, and 7 for details), for the zebra-coated electrode, the empty foil area 5 can be prevented from being affected by the laser when the laser cutting groove is formed, causing thermal stress in the foil, thereby avoiding wrinkles in the empty foil area 5, thereby improving the process yield.

[0054] In some embodiments, as shown in Figures 4, 5 and 8, along the second direction, the distance Dp between the groove close to the edge of the pole piece in the first region 3 and the edge of the pole piece is 0, that is, the groove in the first region passes through the pole piece along the second direction.

[0055] In a specific implementation, the dimension of the groove 31 in the minor axis direction is W3 (i.e., the groove width), and 1 / 5 < W3 / Dm < 1 / 2. This is to avoid the accumulation of heat during the processing of the groove 31 caused by an excessively large groove width, which affects the overall tensile strength of the electrode, while also avoiding the problem of low electrode utilization and high lithium deposition risk caused by an excessively small groove width.

[0056] In a specific implementation, along the first direction, the size of the first region 3 is L1, 50Dm≤L1≤400Dm. This can ensure that the CB (cell balance, the margin of the negative electrode capacity exceeding the positive electrode capacity on the opposite side) value is within a certain range, so that the electrode has sufficient margin during the lithium insertion process to prevent lithium precipitation. Moreover, for thick electrode sheets, the provision of the groove 31 can improve the gram capacity of the active coating 2 close to the current collector 1. Compared with no groove 31 or a relatively small number of grooves 31, the battery energy density is improved.

[0057] In a specific implementation, along the second direction perpendicular to the first direction or the first direction, the grooves 31 of adjacent first regions 3 are staggered. The staggered arrangement can improve the efficiency of the groove 31 manufacturing process.

[0058] In a specific implementation, the offset size of adjacent first regions 3 along the second direction is x, 50 μm ≤ x ≤ 200 μm. This can improve the efficiency of the groove 31 process, but is not limited to this. Those skilled in the art can design the offset size of adjacent first regions 3 according to actual needs.

[0059] In a specific implementation, 100 μm ≤ Dm ≤ 300 μm. That is, along the first direction, the offset dimension between adjacent first regions 3 is Dm (i.e., the interval between adjacent first regions 3). This offset can improve the efficiency of the groove 31 manufacturing process, but is not limited to this. The specific value of Dm can be designed by those skilled in the art according to actual needs.

[0060] In a second aspect, embodiments of the present application provide a spiral wound battery comprising a first electrode sheet, a second electrode sheet, and a separator positioned between the first and second electrode sheets. The first electrode sheet and / or the second electrode sheet are the aforementioned electrode sheets. The first electrode sheet, the second electrode sheet, and the separator are stacked and wound to form a spiral wound battery, which comprises a curved section 41 and a straight section 42.

[0061] The spiral wound battery provided in the embodiment of the present application reduces the density of the active coating 2 on the side of the electrode sheet that is in direct contact with the roller during the electrode sheet rolling process by providing a first region 3 with multiple grooves on at least one side of the current collector 1 in the first direction. This is equivalent to constructing an oriented groove fast ion channel on the surface of the electrode sheet, solving the problem of increased migration path of the electrolyte in the negative electrode sheet, expanding the lithium plating window, reducing the risk of lithium plating, and improving the utilization rate of the negative electrode sheet. At the same time, the potential of the side of the negative electrode sheet close to the separator is increased, improving the cycle performance of the battery, uniformizing the electrolyte concentration, and increasing the utilization rate and energy density of the negative electrode sheet.

[0062] In specific implementations, gaps are formed between adjacent first regions 3. Within the same straight section 42, along the first direction (the first direction is the direction in which the electrode sheets are unwound in a wound cell), the number of gaps is N1. Within the same curved section 41, along the first direction (the first direction is the direction in which the electrode sheets are unwound in a wound cell), the number of gaps is N2, with N1 > N2 ≥ 1. Separators are provided between adjacent electrode sheets in a wound cell battery, and a small number of curved sections 41 matrices improves adhesion between the electrode sheets and the separator, ensuring stability during battery charge and discharge.

[0063] In a specific implementation, two adjacent first regions 3 are located in the straight section 42 and the bent section 41, respectively, and the regional gap between the two adjacent first regions 3 is located in the bent section 41. In this way, the grooves 31 in the first regions 3 on both sides of the regional gap can effectively relieve the stress of the electrode in the bent section 41, preventing damage or even breakage of the electrode due to excessive stress, thereby improving battery safety.

[0064] During specific implementation, the coated electrode is rolled by a pressing roller to achieve the thickness and compaction density required by the process.

[0065] In a specific implementation, the grooves 31 of the first region 3 are formed by laser. Parameters such as laser power, speed, filling spacing, and frequency are controlled to form grooves 31 with a target groove width, groove depth, and groove spacing on the pole piece. However, this is not limiting and other physical or mechanical methods may also be used to form grooves. Those skilled in the art can design specific grooves based on actual needs.

[0066] In a specific implementation, the electrode piece that has been grooved is laser cleaned to clean out the soft tab area of ​​the electrode piece. However, this is not limited to this, and those skilled in the art can design a specific method for cleaning the electrode piece according to actual needs.

[0067] In specific implementation, the cleaned electrode needs to be die-cut. During die-cutting, the non-tab area is along the lower edge of the cleaning tank. The tab width is adapted to the cleaning tank width, and the tab height can be die-cut according to the height requirements of the specific battery cell.

[0068] Finally, it should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or device comprising the element.

[0069] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0070] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present application. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A pole piece, characterized in that: It comprises a current collector (1) and an active coating (2) coated on both sides of the current collector (1), wherein: The active coating (2) on at least one side of the current collector (1) is provided with a plurality of first regions (3) along a first direction, and the region gap between adjacent first regions (3) is Dm; Each of the first regions (3) is provided with a plurality of grooves (31), and the distance between adjacent grooves (31) in a direction perpendicular to the long axis of the grooves (31) is Dt, where Dt>Dm; wherein the first direction is the length direction or the width direction of the pole piece.

2. The pole piece according to claim 1, characterized in that: 1.1Dm<Dt<8Dm.

3. The pole piece according to claim 2, characterized in that: 1.2Dm<Dt<3Dm.

4. The pole piece according to any one of claims 1 to 3, characterized in that: Along a second direction perpendicular to the first direction, the size of the first region (3) is W1, the size of the pole piece is W2, and 0.85W2<W1<W2.

5. The pole piece according to any one of claims 1 to 4, characterized in that: The angle between the line connecting the ends of the grooves (31) on the same side in the first region (3) and the first direction is θ, 0°≤θ≤90°.

6. The pole piece according to any one of claims 1 to 5, characterized in that: The arrangement direction of adjacent first regions (3) is the same as the arrangement direction of the grooves (31) within one of the first regions (3).

7. The pole piece according to any one of claims 1 to 5, characterized in that: Adjacent first regions (3) are arranged at intervals along a second direction perpendicular to the first direction, and the plurality of grooves (31) within one first region (3) are arranged at intervals along the first direction.

8. The pole piece according to any one of claims 1 to 5, characterized in that: Adjacent first regions (3) are arranged at intervals along the first direction, and the plurality of grooves (31) within one of the first regions (3) are arranged at intervals along a second direction perpendicular to the first direction.

9. The pole piece according to any one of claims 1 to 8, characterized in that: Along a second direction perpendicular to the first direction, the distance between the groove in the first region (3) close to the edge of the pole piece and the edge of the pole piece is Dp, and 1.1Dm≤Dp≤1.4Dm.

10. The pole piece according to any one of claims 1 to 9, characterized in that: The dimension of the groove (31) in the short axis direction is W3, 1 / 5<W3 / Dm<1 / 2.

11. The pole piece according to any one of claims 1 to 10, characterized in that: Along the first direction, the size of the first area (3) is L1, 50Dm≤L1≤400Dm.

12. The pole piece according to any one of claims 1 to 11, characterized in that: Along a second direction perpendicular to the first direction or the first direction, the grooves (31) of adjacent first regions (3) are arranged in a staggered manner.

13. The pole piece according to claim 12, characterized in that: Along the second direction, the misalignment dimension between adjacent first regions (3) is x, 50 μm≤x≤200 μm.

14. The pole piece according to any one of claims 1 to 13, characterized in that: 100μm≤Dm≤300μm.

15. A spiral wound battery, characterized in that: The invention comprises a first pole piece, a second pole piece and a diaphragm located between the first pole piece and the second pole piece, wherein the first pole piece and / or the second pole piece is the pole piece according to any one of claims 1 to 14, and the first pole piece, the second pole piece and the diaphragm are stacked and wound to form a winding core, and the winding core comprises a bent section (41) and a straight section (42).

16. The spiral wound battery according to claim 15, characterized in that: In the same straight section (42), along the first direction, the number of regional gaps is N1, and in the same bent section (41), along the first direction, the number of regional gaps is N2, N1>N2≥1.

17. The spiral wound battery according to claim 15 or 16, characterized in that: Two adjacent first regions (3) are respectively located in the straight section (42) and the bent section (41), and the regional gap between the two is located in the bent section (41).

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