Negative pole piece, winding battery cell and battery

Abstract

The utility model provides a negative pole piece, a winding battery cell and a battery. The negative pole piece comprises a negative current collector and a negative active material coating arranged on at least one side surface of the negative current collector, the negative active material coating comprises a first coating area and a second coating area connected to one side of the first coating area, and the second coating area is located in an edge area in the width direction of the negative current collector; the thickness of the second coating area is larger than that of the first coating area, and in the thickness direction of the negative pole piece, the part, protruding out of the first coating area, of the second coating area forms a limiting part for limiting the positive pole piece. According to the utility model, the negative pole piece forms an inverted-L-shaped pole piece or a similar inverted-L-shaped pole piece; by means of the arrangement, the negative pole piece can play a role in limiting the deviation of the positive pole piece in the winding process, and it is effectively guaranteed that the positive pole piece is wrapped by the negative pole piece in the width direction of the pole piece.

Description

Technical Field

[0001] This utility model relates to the field of wound battery cells, and more particularly to a negative electrode sheet, a wound battery cell, and a battery. Background Technology

[0002] When winding battery cells, it is generally necessary to consider the coverage of the positive electrode by the negative electrode across the width of the electrode sheet. Currently, in actual mass production, the main method to ensure qualified coverage is to rely on the equipment's correction and tension adjustment. However, the equipment adjustment has reached its limit, and the yield rate cannot be further improved. Moreover, it is impossible to guarantee the coverage in the width direction of the positive and negative electrodes. Generally, more space is reserved to accommodate process fluctuations, which results in a loss of the battery cell's energy density. The mainstream winding equipment cannot be adjusted, which often leads to spiral-shaped poor coverage in wound battery cells.

[0003] To improve the above problems, it is urgent to design a negative electrode that can effectively coat the positive electrode. Summary of the Invention

[0004] This invention provides a negative electrode sheet, a wound cell, and a battery to solve the problem of poor coverage of the positive electrode sheet by the existing negative electrode sheet in the width direction of the electrode sheet.

[0005] A negative electrode sheet includes a negative current collector and a negative active material coating disposed on at least one side surface of the negative current collector;

[0006] The negative active material coating includes a first coating area and a second coating area connected to one side of the first coating area, wherein the second coating area is located at the edge region in the width direction of the negative electrode current collector;

[0007] The thickness of the second coating area is greater than that of the first coating area. In the thickness direction of the negative electrode sheet, the portion of the second coating area protrudes from the first coating area, forming a limiting portion for limiting the positive electrode sheet.

[0008] Preferably, the second coating area includes a main body and a raised portion;

[0009] The main body is located in the region extending from the first coating area along the width direction of the negative electrode sheet;

[0010] In the thickness direction of the negative electrode sheet, the protrusion extends beyond the first coating area;

[0011] The thickness of the protrusion is greater than, equal to or less than the thickness of the main body.

[0012] Preferably, the negative active material coating is provided on both sides of the negative current collector, and the thickness of the protrusions on the negative active material coating on both sides of the negative current collector may be the same or different.

[0013] Preferably, the protrusion has an arc-shaped cross-section in the width direction of the negative electrode sheet.

[0014] A wound battery cell includes a positive electrode, a separator, and the negative electrode;

[0015] The positive electrode, the diaphragm, and the negative electrode are wound together to form the wound battery cell;

[0016] The diaphragm is located between the positive electrode and the negative electrode;

[0017] The two sides of the diaphragm in the width direction protrude from the two sides of the negative electrode sheet in the width direction, respectively; the two sides of the negative electrode sheet in the width direction protrude from the two sides of the positive electrode sheet in the width direction, respectively.

[0018] The first side of the positive electrode sheet in the width direction is directly opposite the limiting part; the positive electrode sheet and the side of the diaphragm opposite to the limiting part are abutted or spaced apart.

[0019] Preferably, the thickness of the limiting portion is 0.2 to 0.25 times the thickness of the positive electrode sheet.

[0020] Preferably, the side of the negative electrode sheet where the limiting portion is located protrudes from the positive electrode sheet by a width of a.

[0021] On the other side of the negative electrode, the width protruding from the positive electrode is b;

[0022] a < b.

[0023] Preferably, 0.1mm ≤ a < 0.6mm.

[0024] Preferably, 0.6 mm ≤ b ≤ 1.4 mm.

[0025] A battery, characterized in that it comprises the aforementioned wound cell.

[0026] The negative electrode sheet provided in this embodiment of the utility model is used in a wound battery cell. Specifically, it includes a negative current collector and a negative active material coating. The negative active material coating is disposed on at least one side of the negative current collector and is coated flatly on one side. The negative current collector is specifically made of copper foil, and the negative active material coating on the copper foil basically maintains a flat surface. The negative active material coating includes a first coating area and a second coating area connected to one side of the first coating area. The negative current collector passes through the first and second coating areas. The second coating area is located at the edge region of the negative current collector in the width direction. The thickness of the second coating area is greater than the thickness of the first coating area. In the thickness direction of the negative electrode sheet, the portion of the second coating area protruding from the first coating area forms a limiting part for limiting the positive electrode sheet, so that the negative electrode sheet forms an inverted Γ-shaped electrode sheet or a similar inverted Γ-shaped electrode sheet. With this setting, the negative electrode sheet can limit the displacement of the positive electrode sheet during the winding process, effectively ensuring that the negative electrode sheet covers the positive electrode sheet in the width direction of the electrode sheet. The thickness of the second coating area is greater than the thickness of the first coating area, which increases the overall amount of negative active material. Thus, the theoretical lithium insertion amount of the negative electrode exceeds the theoretical lithium extraction amount of the positive electrode by more (larger CB value), and the edge of the wound cell is less prone to lithium deposition. It also reduces the design allowance value in the width direction of the electrode sheet due to the covering problem, and improves the cell energy density of the wound cell. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the description of the embodiments of this utility model will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a cross-sectional view of the negative electrode sheet in the width direction of one embodiment of the present invention;

[0029] Figure 2 This is a schematic diagram of the wrapping of the negative electrode and positive electrode of the wound battery cell in one embodiment of this utility model;

[0030] Figure 3 This is a cross-sectional view of a wound battery cell in one embodiment of this utility model.

[0031] Among them, 1. negative electrode sheet; 11. negative electrode current collector; 12. negative active material coating; 121. first coating area; 122. second coating area; 1221. main body; 1222. protrusion; 2. positive electrode sheet; 21. positive electrode current collector; 22. positive active material coating; 3. diaphragm; 4. tab. Detailed Implementation

[0032] To make the technical problems solved, technical solutions, and beneficial effects of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present utility model and are not intended to limit the present utility model.

[0033] In the description of this utility model, it should be understood that the terms "longitudinal," "radial," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0034] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0035] This utility model embodiment provides a negative electrode sheet 1, referring to... Figure 1 , Figure 2 and Figure 3 The negative electrode 1 includes a negative current collector 11 and a negative active material coating 12 disposed on at least one side surface of the negative current collector 11. The negative active material coating 12 includes a first coating area 121 and a second coating area 122 connected to one side of the first coating area 121. The second coating area 122 is located at the edge region in the width direction of the negative current collector 11. The thickness of the second coating area 122 is greater than the thickness of the first coating area 121. In the thickness direction of the negative electrode 1, the second coating area 122 protrudes from the first coating area 121 to form a limiting portion for limiting the positive electrode 2.

[0036] As an example, the negative electrode 1 is used in a wound battery cell, specifically including a negative current collector 11 and a negative active material coating 12. The negative active material coating 12 is disposed on at least one side surface of the negative current collector 11, and is applied with a single-sided flat coating. The negative current collector 11 is specifically made of copper foil, and the negative active material coating 12 maintains a basically flat surface on the copper foil. The negative active material coating 12 includes a first coating area 121 and a second coating area 122 connected to one side of the first coating area 121. The negative current collector 11 passes through the first coating area 121 and the second coating area 122. The second coating area 122 is located at the edge region in the width direction of the negative current collector 11. The thickness of the second coating area 122 is greater than the thickness of the first coating area 121. In the thickness direction of the negative electrode 1, the second coating area 122 protrudes from the first coating area 121, forming a limiting part for limiting the positive electrode 2, so that the negative electrode 1 forms an inverted Γ shape. The electrode sheet or a similar inverted Γ-shaped electrode sheet is used. This configuration limits the offset of the positive electrode sheet 2 during the winding process, effectively ensuring that the negative electrode sheet 1 covers the positive electrode sheet 2 in the width direction. The thickness of the second coating area 122 is greater than that of the first coating area 121, which increases the overall amount of negative electrode active material. This results in the theoretical lithium insertion amount of the negative electrode exceeding the theoretical lithium extraction amount of the positive electrode (larger CB value), making it less prone to lithium deposition at the edge of the wound cell. This reduces the design allowance in the width direction of the electrode sheet due to coating issues, thereby improving the cell energy density of the wound cell.

[0037] In one embodiment, reference is made to Figure 1 The second coating area 122 includes a main body 1221 and a protrusion 1222; the main body 1221 is located in the extension area of ​​the first coating area 121 along the width direction of the negative electrode sheet 1; in the thickness direction of the negative electrode sheet 1, the protrusion 1222 protrudes from the first coating area 121 to form a limiting part.

[0038] As an example, the second coating area 122 includes a main body 1221 and a protrusion 1222; the main body 1221 is located in the extension area of ​​the first coating area 121 along the width direction of the negative electrode sheet 1; in the thickness direction of the negative electrode sheet 1, the protrusion 1222 protrudes from the first coating area 121 to form a limiting part, so that the negative electrode sheet 1 forms an inverted Γ-shaped electrode sheet or a similar inverted Γ-shaped electrode sheet, and the negative electrode sheet 1 can limit the displacement of the positive electrode sheet 2 during the winding process, effectively ensuring that the negative electrode sheet 1 covers the positive electrode sheet 2 in the electrode sheet width direction.

[0039] In one embodiment, reference is made to Figure 1 The negative electrode current collector 11 has a negative active material coating 12 on both sides of its surface. The thickness of the protrusions 1222 on the negative active material coating 12 on both sides of the negative electrode current collector 11 may be the same or different.

[0040] As an example, the negative electrode current collector 11 has a negative active material coating 12 on both sides of its surface. The thickness of the protrusions 1222 on the negative active material coating 12 on both sides of the negative electrode current collector 11 can be the same or different depending on the actual requirements, as long as it meets the requirement of limiting the positive electrode 2. This setting makes the negative electrode 1 form an inverted T-shaped electrode or a similar inverted T-shaped electrode. During the winding process, the negative electrode 1 can limit the offset of the positive electrode 2, effectively ensuring that the negative electrode 1 covers the positive electrode 2 in the electrode width direction.

[0041] In one embodiment, reference is made to Figure 1 The protrusion 1222 has an arc-shaped cross-section in the width direction of the negative electrode 1.

[0042] As an example, the protrusion 1222 has an arc-shaped cross-section in the width direction of the negative electrode 1. This arrangement facilitates the protrusion 1222 to contact the adjacent electrode when the negative electrode 1 is wound, thus preventing damage to the electrode.

[0043] This utility model embodiment provides a wound battery cell, see reference. Figure 1 , Figure 2 and Figure 3 It includes a positive electrode 2, a separator 3, and a negative electrode 1; the positive electrode 2, the separator 3, and the negative electrode 1 are wound to form a wound battery cell; the separator 3 is located between the positive electrode 2 and the negative electrode 1; the two sides of the separator 3 in the width direction protrude from the two sides of the negative electrode 1 in the width direction; the two sides of the negative electrode 1 in the width direction protrude from the two sides of the positive electrode 2 in the width direction; the first side of the positive electrode 2 in the width direction faces the limiting part; the positive electrode 2 and the side of the separator 3 away from the limiting part 13 are abutted or spaced apart.

[0044] As an example, a wound battery cell includes a positive electrode 2, a separator 3, and a negative electrode 1. During installation, the positive electrode 2, separator 3, and negative electrode 1 are wound to form a wound battery cell. The separator 3 is located between the positive electrode 2 and the negative electrode 1. Both sides of the separator 3 protrude from the sides of the negative electrode 1 in the width direction, physically isolating the positive and negative electrodes to prevent direct contact and short circuit, ensuring the safety of the wound battery cell. Both sides of the negative electrode 1 protrude from the sides of the positive electrode 2 in the width direction. The first side of the positive electrode 2 in the width direction faces the limiting part. The positive electrode 2 and the side of the separator 3 facing away from the limiting part 13 are either in contact or spaced apart. With this arrangement, during the winding process, the limiting part can limit the offset of the positive electrode 2, effectively ensuring that the negative electrode 1 covers the positive electrode 2 in the width direction.

[0045] As an example, refer to Figure 3The positive electrode 3 includes a positive current collector 21 and a positive active material coating 22 disposed on the surface of the positive current collector 21. The positive active material coating 22 is disposed on the surface of the positive current collector 21 and is coated on both sides. The positive current collector 21 is specifically made of aluminum foil, and the positive active material coating 22 is basically flat on the entire surface of the aluminum foil.

[0046] As an example, refer to Figure 3 The wound battery cell also includes tabs 4; depending on the performance requirements, manufacturing process and cost of the battery cell, tabs 4 include positive tabs and negative tabs. The negative tabs are set on the negative electrode plate 1, and the positive tabs are set on the positive electrode plate 3, which play the roles of connection, conduction, sealing and improving battery performance.

[0047] In this example, the negative electrode 1 includes a negative current collector 11 and a negative active material coating 12. The negative active material coating 12 is disposed on at least one side surface of the negative current collector 11 and is applied in a single-sided flat coating manner. Specifically, the negative current collector 11 is made of copper foil, and the negative active material coating 12 maintains a substantially flat surface on the copper foil. The negative active material coating 12 includes a first coating area 121 and a second coating area 122 connected to one side of the first coating area 121. The negative current collector 11 passes through the first coating area 121 and the second coating area 122. The second coating area 122 is located at the edge region in the width direction of the negative current collector 11. The thickness of the second coating area 122 is greater than the thickness of the first coating area 121. In the thickness direction of the negative electrode 1, the second coating area 122 protrudes from the first coating area 121, forming a limiting portion for limiting the positive electrode 2, so that the negative electrode 1 forms an inverted Γ shape. The electrode sheet or a similar inverted Γ-shaped electrode sheet is used. This configuration limits the offset of the positive electrode sheet 2 during the winding process, effectively ensuring that the negative electrode sheet 1 covers the positive electrode sheet 2 in the width direction. The thickness of the second coating area 122 is greater than that of the first coating area 121, which increases the overall amount of negative electrode active material. This results in the theoretical lithium insertion amount of the negative electrode exceeding the theoretical lithium extraction amount of the positive electrode (larger CB value), making it less prone to lithium deposition at the edge of the wound cell. This reduces the design allowance in the width direction of the electrode sheet due to coating issues, thereby improving the cell energy density of the wound cell.

[0048] In one embodiment, reference is made to Figure 1 The thickness of the limiting part is 0.2 to 0.25 times the thickness of the positive electrode 2.

[0049] As an example, the thickness of the limiting portion, i.e., the thickness of the protrusion 1222, is 0.2 to 0.25 times the thickness of the positive electrode 2; the sum of the thicknesses of the two protrusions 1222 in the electrode width direction is 0.4 to 0.5 times the thickness of the positive electrode 2 in the electrode width direction. The optimal setting is that the thickness of one protrusion 1222 is 0.25 times the thickness of the positive electrode 2 in the electrode width direction; for example, the thickness of the positive electrode 2 in the electrode width direction is 2.4 mm. Then the thickness of each protrusion 1222 in the electrode width direction is 0.6 mm. This setting allows the negative electrode 1 to form an inverted T-shaped electrode or a similar inverted T-shaped electrode. During the winding process, the negative electrode 1 can limit the offset of the positive electrode 2, effectively ensuring that the negative electrode 1 covers the positive electrode 2 in the electrode width direction.

[0050] In one embodiment, reference is made to Figure 3 The negative electrode 1 has a limiting portion on one side, and the width protruding from the positive electrode 2 is a; the width protruding from the positive electrode 2 on the other side of the negative electrode 1 is b; a < b.

[0051] As an example, on one side of the negative electrode plate 1 with the limiting part, the width protruding beyond the positive electrode plate 2 is 'a'; on the other side of the negative electrode plate 1, the width protruding beyond the positive electrode plate 2 is 'b'; a < b. This arrangement ensures that the negative electrode plate 1 can effectively cover the positive electrode plate 2 without changing the overall size of the cell. The lengths of the negative electrode plate 1 extending beyond the positive electrode plate 2 on both sides can be adjusted, thereby widening the electrode width and increasing the energy density of the cell. For example, during design, one side of the electrode width direction can be designed according to the minimum covering standard, while the other side can be designed normally. Specifically, 'a' is designed according to the minimum covering standard, and 'b' is designed normally. This reduces the design allowance for covering issues in the electrode width direction, thus increasing the cell's energy density. For example, in a conventional design, the width of the negative electrode 1 exceeds the width of the positive electrode 2 by 1.2mm, with an average width of 0.6mm on each side. According to the design scheme in this example, a) it can be designed with a width of 0.2mm, and b) it can be designed with a width of 0.6mm. The total coverage of the negative electrode 1 over the positive electrode 2 can be adjusted to 0.8mm. Without changing the overall size of the wound cell, the electrode can be widened by 0.4mm, which can increase the energy density of the cell by nearly 1%.

[0052] In one embodiment, reference is made to Figure 3 , 0.1mm≤a<0.6mm.

[0053] As an example, the width a protruding from the positive electrode 2 on the side of the negative electrode 1 with the limiting part is limited, and the design must satisfy 0.1mm≤a<0.6mm.

[0054] In one embodiment, reference is made to Figure 3 , 0.6 mm≤b≤1.4 mm.

[0055] As an example, the width b of the negative electrode plate 1 protruding from the positive electrode plate 2 on the other side is limited, and the design must satisfy 0.6 mm ≤ b ≤ 1.4 mm.

[0056] This utility model provides a battery, including a wound cell.

[0057] As an example, the battery includes a wound cell; the wound cell includes a positive electrode 2, a separator 3, and a negative electrode 1; during installation, the positive electrode 2, separator 3, and negative electrode 1 are wound to form a wound cell; the separator 3 is located between the positive electrode 2 and the negative electrode 1, and both sides of the separator 3 protrude from both sides of the negative electrode 1 in the width direction, physically isolating the positive and negative electrodes to prevent direct contact and short circuit, ensuring the safety of the wound cell. Both sides of the negative electrode 1 protrude from both sides of the positive electrode 2 in the width direction, and the first side of the positive electrode 2 in the width direction faces the limiting part; the positive electrode 2 and the side of the separator 3 away from the limiting part 13 are either in contact or spaced apart; with this arrangement, during the winding process, the limiting part can limit the offset of the positive electrode 2, effectively ensuring that the negative electrode 1 covers the positive electrode 2 in the width direction.

[0058] In this example, the negative electrode 1 includes a negative current collector 11 and a negative active material coating 12. The negative active material coating 12 is disposed on at least one side surface of the negative current collector 11 and is applied in a single-sided flat coating manner. Specifically, the negative current collector 11 is made of copper foil, and the negative active material coating 12 maintains a substantially flat surface on the copper foil. The negative active material coating 12 includes a first coating area 121 and a second coating area 122 connected to one side of the first coating area 121. The negative current collector 11 passes through the first coating area 121 and the second coating area 122. The second coating area 122 is located at the edge region in the width direction of the negative current collector 11. The thickness of the second coating area 122 is greater than the thickness of the first coating area 121. In the thickness direction of the negative electrode 1, the second coating area 122 protrudes from the first coating area 121, forming a limiting portion for limiting the positive electrode 2, so that the negative electrode 1 forms an inverted Γ shape. The electrode sheet or a similar inverted Γ-shaped electrode sheet is used. This configuration limits the offset of the positive electrode sheet 2 during the winding process, effectively ensuring that the negative electrode sheet 1 covers the positive electrode sheet 2 in the width direction. The thickness of the second coating area 122 is greater than that of the first coating area 121, which increases the overall amount of negative electrode active material. This results in the theoretical lithium insertion amount of the negative electrode exceeding the theoretical lithium extraction amount of the positive electrode (larger CB value), making it less prone to lithium deposition at the edge of the wound cell. This reduces the design allowance in the width direction of the electrode sheet due to coating issues, thereby improving the cell energy density of the wound cell.

[0059] The above-described embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model, and should all be included within the protection scope of this utility model.

Claims

1. A negative electrode sheet, characterized in that, It includes a negative electrode current collector and a negative active material coating disposed on at least one side surface of the negative electrode current collector; The negative active material coating includes a first coating area and a second coating area connected to one side of the first coating area, wherein the second coating area is located at the edge region in the width direction of the negative electrode current collector; The thickness of the second coating area is greater than that of the first coating area. In the thickness direction of the negative electrode sheet, the portion of the second coating area protrudes from the first coating area, forming a limiting portion for limiting the positive electrode sheet.

2. The negative electrode sheet according to claim 1, characterized in that, The second coating area includes a main body and a raised portion; The main body is located in the region extending from the first coating area along the width direction of the negative electrode sheet; In the thickness direction of the negative electrode sheet, the protrusion extends out of the first coating area, forming the limiting portion.

3. The negative electrode sheet according to claim 2, characterized in that, The negative electrode current collector has a negative active material coating on both sides, and the thickness of the protrusions on the negative active material coating on both sides of the negative electrode current collector may be the same or different.

4. The negative electrode sheet according to claim 2, characterized in that, The protrusion has an arc-shaped cross-section in the width direction of the negative electrode sheet.

5. A wound battery cell, characterized in that, Includes a positive electrode, a separator, and a negative electrode as described in any one of claims 1-4; The positive electrode, the diaphragm, and the negative electrode are wound together to form the wound battery cell; The diaphragm is located between the positive electrode and the negative electrode; The two sides of the diaphragm in the width direction protrude from the two sides of the negative electrode sheet in the width direction, respectively; the two sides of the negative electrode sheet in the width direction protrude from the two sides of the positive electrode sheet in the width direction, respectively. The first side of the positive electrode sheet in the width direction is directly opposite the limiting part; the positive electrode sheet and the side of the diaphragm opposite to the limiting part are abutted or spaced apart.

6. The wound battery cell according to claim 5, characterized in that, The thickness of the limiting portion is 0.2 to 0.25 times the thickness of the positive electrode sheet.

7. The wound battery cell according to claim 5, characterized in that, The negative electrode sheet has the limiting portion on one side, and the width of the protrusion from the positive electrode sheet is a. On the other side of the negative electrode, the width protruding from the positive electrode is b; a < b.

8. The wound battery cell according to claim 7, characterized in that, 0.1mm≤a<0.6mm.

9. The wound battery cell according to claim 7, characterized in that, 0.6 mm ≤ b ≤ 1.4 mm.

10. A battery, characterized in that, Includes the wound battery cell as described in any one of claims 5-9.

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