Pole piece, roll core and battery

Abstract

The invention relates to a pole piece, a roll core and a battery, in particular to a pole piece, a roll core and a battery which are suitable for a kneading process, when the pole piece is in an unfolded state, grooves are formed in the first side of the pole piece in an array mode in the first direction, and the lengths of all the grooves in the first direction are the same; a protrusion is formed between every two adjacent grooves. In a winding state, a center hole is formed in the center of the pole piece, and the grooves are sequentially aligned in the radial direction of the pole piece to form at least one segmentation groove; the length of the shorter protrusions in the two adjacent sets of protrusions is defined as L1, the length of the longer protrusions in the two adjacent sets of protrusions is defined as L2, the thickness of the pole piece is defined as h, N is the number of the partition grooves, and L1 and L2 meet the following relation: L2-L1 = 2pih / N.

Description

Technical Field

[0001] This invention relates to an electrode, a core, and a battery, and more particularly to an electrode, a core, and a battery suitable for a flattening process. Background Technology

[0002] Traditional cylindrical battery cells (such as 18650 / 21700) have long dominated the consumer electronics and electric vehicle markets due to their high standardization and flexible assembly capabilities. However, with the increasing demands for energy density, fast charging performance, and system cost from new energy vehicles, larger battery cells (such as 4680, 4695, and 46120) have emerged. Traditional single / multi-tab designs can no longer meet the conductivity and heat dissipation requirements of large cylindrical cells, while the all-tab structure has become the optimal solution due to its low internal resistance. This design significantly improves fast charging performance and optimizes heat dissipation efficiency by increasing the current conduction area.

[0003] However, the current large cylindrical cell omnipolar structure still faces three major challenges: (1) Difficulty in removing moisture during baking: The flattening process densifies the tab structure, making it difficult to remove moisture from the core to the target requirements, especially for cells using small-particle cathode materials. Residual moisture can cause problems such as electrolyte decomposition and interfacial side reactions, significantly reducing the cycle life and storage performance of the cell.

[0004] (2) Low electrolyte injection efficiency: The dense structure of the tabs hinders the rapid penetration of electrolyte, significantly prolonging the injection time. At the same time, it reduces the wetting effect of the electrolyte on the positive and negative electrodes and the separator.

[0005] (3) Uneven electrolyte distribution: Gravity causes the electrolyte to deposit at the bottom of the cell, while the dense tab structure hinders its upward migration. During cell cycling, this "bottom-rich and top-poor" distribution will exacerbate the electrode interface impedance and accelerate cell degradation.

[0006] Chinese invention patent CN114883758B discloses an electrode structure, a current collector, a cylindrical battery cell, and a vehicle. It reduces the clamping pressure of the electrode by adding a slit at the electrode. The inventors discovered that the slit is identical to the center hole of the core, which can reduce the clamping pressure of the electrode while also solving the three major challenges mentioned above. However, if the slit is made according to the method described in the aforementioned patent, cutting chips generated during the cutting process will inevitably enter the core, creating a safety hazard.

[0007] In view of the above problems, the structure of the electrode needs to be improved. Summary of the Invention

[0008] To overcome the shortcomings of the prior art, the present invention provides an electrode sheet, a winding core comprising the electrode sheet, and a battery comprising the winding core. One of the objectives of this invention is to provide an electrode sheet having an unfolded state and a wound state; In the unfolded state, the first side of the electrode is provided with grooves arranged in an array along the first direction, and all the grooves have the same length in the first direction; a protrusion is formed between two adjacent grooves; In the wound state, a central hole is formed in the center of the electrode sheet, and the grooves are sequentially aligned in the radial direction of the electrode sheet to form at least one dividing groove; The dividing groove divides the end of the electrode sheet in the wound state into N equal parts, with each group consisting of N protrusions. The length of the shorter protrusion in two adjacent groups is defined as L1, and the length of the longer protrusion is defined as L2. The thickness of the electrode sheet is defined as h, where L1 and L2 satisfy the following relationship: L2-L1=2πh / N.

[0009] Preferably, the electrode sheet is divided into a sheet material area, a blank area and a flattening area in the second direction, wherein the flattening area extends to the blank area.

[0010] The second objective of this invention is to provide a winding core, comprising the aforementioned electrode sheet; the electrode sheet is divided into a positive electrode sheet and a negative electrode sheet, wherein the first side of the positive electrode sheet is close to the second side of the negative electrode sheet, and the second side of the positive electrode sheet is close to the first side of the negative electrode sheet.

[0011] Preferably, the height of the positive electrode sheet material area in the second direction is defined as h2, and the height of the negative electrode sheet material area in the second direction is defined as h3, wherein h3 is greater than h2, and the second side of the negative electrode sheet extends to the blank area of ​​the positive electrode sheet.

[0012] Preferably, after the flattened area of ​​the positive electrode sheet is flattened, the dividing groove forms a positive electrode tab through hole; after the flattened area of ​​the negative electrode sheet is flattened, the dividing groove forms a negative electrode tab through hole, and the positive electrode tab through hole and the negative electrode tab through hole are respectively connected to the central hole.

[0013] A third objective of the present invention is to provide a battery comprising the aforementioned winding core; A positive current collector and a negative current collector, wherein the positive current collector and the negative current collector are respectively welded to the flattened area of ​​the positive electrode sheet and the flattened area of ​​the negative electrode sheet of the core. The outer casing, the winding core, the positive current collector and the negative current collector are all placed inside the outer casing cavity; The first insulating sheet is distributed in the inner cavity of the outer shell and is used to electrically isolate the negative terminal of the winding core from the outer shell. Nut, the negative electrode post on the negative electrode current collector extends to the outer shell and is screwed into the nut; A sealing strip, which is fixed to the positive end of the winding core, is used to seal the center hole; A cover plate is provided, wherein the end of the outer casing facing the positive electrode has an opening, and the cover plate is connected to the opening; The second insulating sheet, which is attached to the outside of the housing, is used to electrically isolate the nut and the housing.

[0014] Preferably, the welding trajectories of the positive current collector, the negative current collector, and the core are located between two adjacent dividing grooves.

[0015] Preferably, an explosion-proof valve is provided on the cover plate.

[0016] The present invention has the following technical effects: (1) When the electrode sheet is unfolded, it is preferentially processed into grooves and protrusions, and the length of the protrusions in different groups is different; when it is wound, the grooves form a dividing groove, so there is no need to cut it, thereby avoiding the chips caused by cutting from entering the core and causing safety hazards.

[0017] (2) The trend of increasing length of multiple protrusions, the positive and negative ends of the wound core after winding form a cross-segmentation groove, and the positive and negative ends of the wound core after flattening form a positive electrode through hole and a negative electrode through hole; this design will not significantly reduce the flow capacity of the full electrode structure, but can fundamentally solve the problem of the density of the full electrode structure after flattening.

[0018] (3) Both the negative electrode tab and the positive electrode tab can form good pathways with the positive and negative electrode plates, and are interconnected with the center hole of the core. During the cell baking process, the moisture in the core can easily drain from the inside to the outside through the hole pathways. The electrolyte can also flow freely between the positive and negative electrode plates through the hole pathways, thereby improving the cell performance. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the electrode in its unfolded state; Figure 2 This is a schematic diagram of the core in its unfolded state; Figure 3 This is a schematic diagram of the core structure in its unflattened state; Figure 4 This is a schematic diagram of the core structure in its unflattened state; Figure 5 This is a schematic diagram of the core structure after it has been flattened. Figure 6 A schematic diagram of the structure for welding positive or negative current collectors; Figure 7 This is a schematic diagram of the exploded structure of a battery.

[0020] In the diagram, 100. Electrode sheet; 101. Groove; 102. Protrusion; 103. Center hole; 104. Dividing groove; 105. Sheet material area; 106. Blank area; 107. Flattening area; 200. Core; 201. Positive electrode sheet; 202. Negative electrode sheet; 203. Positive electrode tab through-hole; 204. Negative electrode tab through-hole; 300. Battery; 301. Positive current collector; 302. Negative current collector; 303. Outer casing; 304. First insulating sheet; 305. Nut; 306. Sealing sheet; 307. Cover plate; 308. Second insulating sheet. Detailed Implementation

[0021] The principles and features of the present invention are described below with reference to embodiments; the examples given are only for explaining the present invention and are not intended to limit the scope of the present invention. The first direction described below is the Y direction, and the second direction described below is the X direction.

[0022] Example 1 This embodiment provides an electrode sheet 100, which is mainly used for preparing battery cores. Before being made into a core, the electrode sheet 100 is in a sheet shape, which is referred to in this patent as the unfolded state; after being made into a core, the electrode sheet 100 is in a cylindrical shape, which is referred to in this patent as the wound state.

[0023] In its unfolded state, the electrode 100 is approximately rectangular. The first side of the electrode 100 is defined as... Figure 1 In the B side, the second side of electrode 100 is defined as... Figure 1 On side A of the electrode 100, grooves 101 are arranged in a spaced array on the first side, and a protrusion 102 is formed between two adjacent grooves 101. The grooves 101 have the same length in the first direction; the length of the protrusions 102 gradually increases in the first direction.

[0024] In the wound state, a central hole 103 is formed in the center of the electrode 100, and the grooves 101 are aligned in the radial direction to form at least one dividing groove 104. The smaller the width of the groove 101, the more dividing grooves 104 there are. In this embodiment, there are a total of 6 dividing grooves 104, and one end of the dividing groove 104 communicates with the central hole 103.

[0025] The number of dividing grooves 104 is defined as N. Each dividing groove 104 divides the end of the wound electrode 100 into N equal parts, i.e., N consecutive protrusions 102 and N consecutive grooves 101 are wound into a circle, with all grooves 101 having the same length. In this embodiment, six dividing grooves 104 are designed, dividing the end of the wound electrode 100 into six equal parts, i.e., six protrusions 102 and six grooves 101 are wound into a circle. Each group of six adjacent protrusions 102 forms a group, and the six protrusions 102 in the same group have the same length in the first direction, while the lengths of the protrusions 102 in different groups gradually increase. Let L1 be the length of the shorter protrusion 102 in two adjacent sets of protrusions 102, and L2 be the length of the longer protrusion 102. Let h be the thickness of the electrode 100. Let R be the diameter of the circle formed by six adjacent shorter protrusions 102 and grooves 101. Then the distance between the circle formed by the six adjacent longer protrusions 102 and grooves 101 is R+h. Let L2 be the length of the longer protrusion 102 and L1 be the length of the shorter protrusion 102. L1 and L2 are the arc lengths corresponding to the central angles. According to the arc length formula, L2-L1=2πh / N.

[0026] The electrode 100 is divided into a sheet area 105, a blank area 106, and a flattening area 107 in the second direction. The groove 101 extends from the flattening area 107 to the blank area 106. The electrode 100 is processed into a wound state, and the flattening area 107 is flattened using a flattening machine. It should be noted that a blank section should be reserved at the beginning and end of the electrode 100, as shown in the attached diagram. Figure 2 W1 and W2 are used to prevent bending at the beginning and end of the electrode sheet 100 after it is flattened. Generally, W1 and W2 are 1 to 3 times the length of the innermost circle of the core.

[0027] Example 2 This embodiment provides a core 200 composed of two electrode sheets 100, namely a positive electrode sheet 201 and a negative electrode sheet 202. The positive electrode sheet 201 and the negative electrode sheet 202 in their unfolded states are stacked together, with the first side of the positive electrode sheet 201 close to the second side of the negative electrode sheet 202, and the second side of the positive electrode sheet 201 close to the first side of the negative electrode sheet 202. The first side of either the positive electrode sheet 201 or the negative electrode sheet 202 is attached. Figure 2 On side A, the second side of either the positive electrode 201 or the negative electrode 202 is attached. Figure 2On side B of the positive electrode 201, the height of the sheet material area 105 in the second direction is defined as h3, and the height of the blank area 105 of the negative electrode 202 in the second direction is defined as h3, where h3 is greater than h2, that is, the second side of the negative electrode 202 extends to the blank area 106 of the positive electrode 201 to prevent lithium plating. After the positive electrode 201 and the negative electrode 202 are wound, a flattening device is used. After flattening, the dividing groove 104 at the positive end forms a positive electrode tab through hole, and the dividing groove 104 at the negative end forms a negative electrode tab through hole.

[0028] Example 3 This embodiment provides a battery 300, comprising a core 200, a positive current collector 301, a negative current collector 302, a casing 303, a first insulating sheet 304, a nut 305, a sealing sheet 306, a cover plate 307, and a second insulating sheet. The positive current collector 301 and the negative current collector 302 are respectively welded to the flattened areas 107 of the positive electrode sheet 201 and the negative electrode sheet 202 of the core 200. This embodiment does not limit the specific shape of the positive current collector 301 and the negative current collector 302; any existing form of positive current collector 301 and negative current collector 302 can be used. The welding paths of the positive current collector 301, the negative current collector 302, and the core 200 are located between two adjacent dividing grooves 104. The outer casing 303 is cylindrical with an opening at one end. The core 200, positive current collector 301, and negative current collector 302 are inserted into the outer casing 303 through the opening. One end of the negative electrode post is welded to the positive current collector 301, and the negative electrode post extends out of the outer casing 303 and is screwed onto the nut 305. A first insulating sheet 304 is distributed inside the outer casing 303 and attached to the negative current collector 302 to electrically isolate the negative current collector 302 from the outer casing 303. A second insulating sheet 308 is attached to the outside of the outer casing 303 to electrically isolate the nut 305 from the outer casing 303. A sealing sheet 306 is fixed to the positive end of the core 200 to seal the center hole 103. A cover plate 307 is connected to the opening to seal the outer casing 303. An explosion-proof valve is provided on the cover plate 307. When the battery malfunctions and produces gas, the explosion-proof valve opens to release the gas. The explosion-proof valve can be in the existing form, generally integrally formed with the cover plate 307, and can be separated from the cover plate 307 by adding grooves.

[0029] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An electrode sheet, characterized in that: The electrode (100) has an unfolded state and a wound state; In the unfolded state, the first side of the electrode (100) is provided with grooves (101) arranged in a first direction, and all grooves (101) have the same length in the first direction; a protrusion (102) is formed between two adjacent grooves (101). In the wound state, the electrode (100) has a central hole (103) formed in the center, and the groove (101) is aligned to form at least one dividing groove (104). The dividing groove (104) is defined to divide the end of the coiled electrode (100) into N equal parts. Each N adjacent protrusions (102) form a group. The length of the shorter protrusion (102) in two adjacent groups of protrusions (102) is defined as L1 and the length of the longer protrusion (102) is defined as L2. The thickness of the electrode (100) is defined as h, where L1 and L2 satisfy the following relationship: L2-L1=2πh / N.

2. The electrode sheet according to claim 1, characterized in that, The electrode (100) is divided into a sheet material area (105), a blank area (106) and a flattening area (107) in the second direction, and the groove (101) extends from the flattening area (107) to the blank area (106).

3. A type of winding core, characterized in that, The core (200) includes an electrode (100) as described in any one of claims 1 or 2; the electrode (100) is divided into a positive electrode (201) and a negative electrode (202), the second side of the positive electrode (201) is close to the first side of the negative electrode (202), and the first side of the positive electrode (201) is close to the second side of the negative electrode (202).

4. The winding core according to claim 3, characterized in that, The height of the sheet material area (105) of the positive electrode (201) in the second direction is defined as h2, and the height of the sheet material area (105) of the negative electrode (202) in the second direction is defined as h3, where h3 is greater than h2, and the second side of the negative electrode (202) extends to the blank area (106) of the positive electrode (201).

5. The winding core according to claim 3, characterized in that, After the flattened area (107) of the positive electrode (201) is flattened, the dividing groove (104) forms a positive electrode through hole (203); after the flattened area (107) of the negative electrode (202) is flattened, the dividing groove (104) forms a negative electrode through hole (204); the positive electrode through hole (203) and the negative electrode through hole (204) are respectively connected to the central hole (103).

6. A battery, characterized in that, The battery (300) includes: The core (200) according to any one of claims 3 to 5; Positive current collector (301) and negative current collector (302), wherein the positive current collector (301) and negative current collector (302) are respectively welded to the flattened area (107) of the positive electrode sheet (201) and the flattened area (107) of the negative electrode sheet (202) of the core (200). The outer shell (303) contains the core (200), the positive current collector (301), and the negative current collector (302), all of which are located inside the outer shell cavity. The first insulating sheet (304) is distributed in the inner cavity of the outer shell (303) to electrically isolate the negative current collector (302) from the outer shell (303); Nut (305), the negative electrode post on the negative electrode current collector (302) extends to the outer shell and is screwed to the nut (305); A sealing sheet (306) is fixed to the positive end of the core (200) and is used to seal the center hole (103). The cover plate (307) has an opening at one end of the outer shell (303) facing the positive electrode, and the cover plate (307) is connected to the opening; The second insulating sheet (308) is attached to the outside of the outer shell (303) and is used to electrically isolate the nut (305) and the outer shell (303).

7. The battery according to claim 6, characterized in that, The welding trajectories of the positive current collector (301), the negative current collector (302), and the core (200) are located between two adjacent dividing grooves (104).

8. The battery according to claim 6, characterized in that, An explosion-proof valve is provided on the cover plate (307).

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