Negative plate and laminated battery

Abstract

The utility model provides a negative plate and a laminated battery, belonging to the technical field of laminated battery, the negative plate comprises a current collector, a first active material layer, a second active material layer and a third active material layer, the current collector is provided with at least one surface to be coated, the surface to be coated is divided into a first area, a second area and a third area from the center to the periphery, a second region and a third region; a first active material layer disposed in the first region; a second active material layer disposed in the second region; the third active material layer is disposed in the third region, a coating surface density of the second active material layer is less than a coating surface density of the first active material layer, and the coating surface density of the second active material layer is greater than a coating surface density of the third active material layer. The densities of the coating surfaces of the first active material layer, the second active material layer and the third active material layer are set to be gradually reduced, so that the lithium intercalation degree of each region corresponds to the lithium intercalation degree, and waste caused by the fact that more active materials do not participate in lithium intercalation is avoided.

Description

Technical Field

[0001] The utility model relates to the technical field of batteries, in particular to a negative electrode sheet and a laminated battery. Background Art

[0002] With the continuous pursuit of charging speed in the new energy market, power batteries generally have 2C fast charging capabilities, and some already have 4C and 6C fast charging capabilities, which has broad application prospects.

[0003] During the fast charging process of the stacked battery, lithium deposition will occur due to the negative electrode lithium embedding space and other reasons. The occurrence of lithium deposition reduces the performance of the battery. In order to reduce lithium deposition and to avoid the positive electrode sheet exceeding the negative electrode sheet due to process errors, the size of the negative electrode sheet is currently larger than that of the positive electrode sheet, and the coating surface density of the active material in each area of ​​the negative electrode sheet is consistent. However, this will result in a waste of some active materials on the negative electrode sheet. Utility Model Content

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defect in the prior art that part of the active material on the negative electrode sheet is wasted during the fast charging process of the laminated battery, thereby providing a negative electrode sheet and a laminated battery.

[0005] In order to solve the above technical problems, the utility model provides a negative electrode sheet, comprising:

[0006] A current collector having at least one surface to be coated, wherein the surface to be coated is divided from the center to the periphery into a first region, a second region and a third region which are connected in sequence around the center;

[0007] A first active material layer is disposed in the first region;

[0008] A second active material layer is disposed in the second region;

[0009] The third active material layer is arranged in the third region, the coating surface density of the second active material layer is less than the coating surface density of the first active material layer, and the coating surface density of the second active material layer is greater than the coating surface density of the third active material layer.

[0010] Optionally, the coating surface density of the first active material layer is 1.05-1.15 times the coating surface density of the second active material layer.

[0011] Optionally, the coating surface density of the third active material layer is 0.75-0.9 times the coating surface density of the second active material layer.

[0012] Optionally, the first area is a rectangular structure, and a corner area of ​​the first area is an arc structure.

[0013] Optionally, the radius R of the corner area is 1 mm-3 mm.

[0014] Optionally, a width g of the first section arranged along the length direction of the current collector in the second region is 1 mm-2 mm;

[0015] And / or, a width h of a second section of the second region arranged along the length direction of the current collector is 1 mm-2 mm;

[0016] And / or, a width f of a third section of the second region arranged along the width direction of the current collector is 1 mm-2 mm;

[0017] And / or, a width e of a fourth section of the second region arranged along the width direction of the current collector is 1 mm-2 mm.

[0018] Optionally, a width c of the fifth section arranged along the length direction of the current collector in the third region is 0.5 mm-2 mm;

[0019] And / or, a width d of a sixth section of the third region arranged along the length direction of the current collector is 0.5 mm-2 mm;

[0020] And / or, a width b of a seventh section of the third region arranged along the width direction of the current collector is 0.5 mm-2 mm;

[0021] And / or, a width a of an eighth section of the third region arranged along the width direction of the current collector is 1 mm-2 mm.

[0022] Optionally, the eighth section of the third region is suitable for connecting to a pole lug.

[0023] The utility model also provides a laminated battery, comprising a laminated positive electrode sheet and any one of the above-mentioned negative electrode sheets.

[0024] Optionally, the first active material layer and the second active material layer in the positive electrode sheet and the negative electrode sheet are arranged opposite to each other;

[0025] The positive electrode sheet has a first projection in the direction in which the positive electrode sheet and the negative electrode sheet are stacked; the third active material layer has a second projection in the direction in which the positive electrode sheet and the negative electrode sheet are stacked; wherein the first projection and the second projection at least partially do not overlap, and an outer contour of the second projection exceeds an outer contour of the first projection.

[0026] The technical solution of the utility model has the following advantages:

[0027] The negative electrode sheet provided by the utility model comprises a current collector, a first active material layer, a second active material layer and a third active material layer, the current collector has at least one surface to be coated, the surface to be coated is divided from the center to the periphery into a first region, a second region and a third region which are sequentially connected and surrounded, the first active material layer is arranged in the first region, the second active material layer is arranged in the second region, and the third active material layer is arranged in the third region, wherein the coating surface density of the second active material layer is less than the coating surface density of the first active material layer, and the coating surface density of the second active material layer is greater than the coating surface density of the third active material layer;

[0028] Since the degree of lithium insertion on the negative electrode sheet gradually decreases from the center to the periphery, the coating surface density of the first active material layer, the second active material layer and the third active material layer from the inside to the outside is set to gradually decrease, so that the coating surface density of each region corresponds to the respective degree of lithium insertion, thereby avoiding the waste of more active materials not participating in lithium insertion and improving the energy density. In the third region, only a very small amount of negative electrode participates in lithium insertion and deinsertion during the battery cell cycle. The reduction in the coating surface density in the third region helps to reduce the negative electrode active material to avoid material waste and increase the energy density. The second region is the area where the negative electrode is not fully inserted with lithium during the fast charge cycle. The actual degree of lithium insertion in this area is 70%-90%, which results in some active materials in this area not being utilized. Therefore, by reducing the coating surface density of the second region, the waste of negative electrode materials can be avoided and the energy density can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the specific implementation methods of the utility model or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 A schematic structural diagram of an implementation method of a negative electrode sheet provided in Example 1 of the utility model;

[0031] Figure 2 for Figure 1 Schematic diagram of the structure of the current collector.

[0032] Description of reference numerals:

[0033] 1. Current collector; 2. First region; 3. Second region; 4. Third region; 5. First active material layer; 6. Second active material layer; 7. Third active material layer; 8. Corner region; 9. First section; 10. Second section; 11. Third section; 12. Fourth section; 13. Fifth section; 14. Sixth section; 15. Seventh section; 16. Eighth section; 17. Ear. DETAILED DESCRIPTION

[0034] The technical solution of the utility model will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0035] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0036] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0037] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0038] Example 1

[0039] The negative electrode sheet provided in this embodiment is used in a laminated battery, which improves the lithium plating situation and avoids the waste of active materials.

[0040] like Figure 1 and Figure 2As shown, a specific implementation of the negative electrode sheet provided in this embodiment includes a current collector 1, a first active material layer 5, a second active material layer 6 and a third active material layer 7, the current collector 1 has at least one surface to be coated, and the surface to be coated is divided from the center to the periphery into a first area 2, a second area 3 and a third area 4 which are sequentially connected and surrounded; the first active material layer 5 is arranged in the first area 2; the second active material layer 6 is arranged in the second area 3; the third active material layer 7 is arranged in the third area 4, the coating surface density of the second active material layer 6 is less than the coating surface density of the first active material layer 5, and the coating surface density of the second active material layer 6 is greater than the coating surface density of the third active material layer 7.

[0041] Since the degree of lithium insertion on the negative electrode sheet gradually decreases from the center to the periphery, the coating surface density of the first active material layer 5, the second active material layer 6 and the third active material layer 7 from the inside to the outside is set to gradually decrease so that the coating surface density of each area corresponds to the respective lithium insertion degree, thereby avoiding the waste of more active materials not participating in lithium insertion and improving the energy density.

[0042] Specifically, the current collector 1 has two surfaces disposed opposite to each other. When the current collector 1 is coated on one side, one of the two surfaces is used as the surface to be coated. When the current collector 1 is coated on both sides, both surfaces are used as the surface to be coated.

[0043] Specifically, the typical but non-limiting current collector 1 can be copper foil, composite copper foil, aluminum foil, etc., which can provide good electrical conductivity and mechanical strength, and the size and thickness of the current collector 1 are not limited. The first active material layer 5, the second active material layer 6 and the third active material layer 7 are all disposed on the current collector 1 by coating, and the first active material layer 5, the second active material layer 6 and the third active material layer 7 respectively include negative electrode active materials, and the negative electrode active materials include graphite and / or silicon-containing materials, which participate in the battery reaction, and the specific material thereof is not limited.

[0044] In a specific embodiment, the coating surface density of the first active material layer 5 is 120 g / m 2 -200g / m 2 , the specific value can be selected according to the actual battery requirements.

[0045] In the negative electrode sheet provided in this embodiment, the coating surface density of the first active material layer 5 is 1.05-1.15 times the coating surface density of the second active material layer 6, for example, it can be 1.05, 1.08, 1.1, 1.12, 1.15, etc., which are typical but not limiting coating surface densities, and is preferably 1.1-1.15.

[0046] The second active material layer 6 in the second region 3 is a region where the negative electrode is not fully embedded with lithium during fast charging cycles, and its actual lithium embedding degree is 70%-90%. In traditional negative electrode sheets, part of the negative electrode active material in this region is not utilized. By setting the coating surface density of the second active material layer 6 to be smaller than the coating surface density of the first active material layer 5, waste of negative electrode materials can be avoided and energy density can be improved.

[0047] In the negative electrode sheet provided in this embodiment, the coating surface density of the third active material layer 7 is 0.75-0.9 times the coating surface density of the second active material layer 6, for example, it can be 0.75, 0.78, 0.8, 0.83, 0.85, 0.88, 0.9 and other typical but non-limiting coating surface densities, preferably 0.8-0.85.

[0048] The third region 4 is the area where the negative electrode sheet exceeds the positive electrode sheet. Only a very small amount of negative electrode participates in lithium extraction and extraction in the third region 4 during the battery cell cycle. The reduced coating surface density of the third region 4 helps to reduce the negative electrode active material to avoid material waste and improve the energy density. The coating surface density of the third region 4 cannot be too low. If it is too low, the negative electrode sheet that is shifted in position during the production process cannot embed the lithium ions extracted from the positive electrode, resulting in lithium precipitation.

[0049] like Figure 2 As shown, in the negative electrode sheet provided in this embodiment, the first region 2 is a rectangular structure, and the corner region 8 of the first region 2 is an arc-shaped structure. The setting of the corner region 8 as an arc-shaped region makes the current density distribution in the corner region more uniform, thereby reducing lithium deposition in the corner region 8.

[0050] In addition, as an alternative implementation, the first area 2 may also be circular or elliptical.

[0051] In the negative electrode sheet provided in this embodiment, the radius R of the corner area 8 is 1mm-3mm, for example, it can be 1mm, 1.5mm, 2mm, 2.5mm, 3mm and other typical but non-limiting radii, preferably 1.5mm-2.5mm, which can keep the negative electrode sheet free of lithium deposition.

[0052] Figure 1 The left and right directions are the length directions of the current collector 1. Figure 1 The up-down direction is the width direction of the current collector 1 .

[0053] In the negative electrode sheet provided in this embodiment, the width g of the first section 9 arranged along the length direction of the current collector 1 in the second region 3 is 1mm-2mm; for example, the width g can be 1mm, 1.2mm, 1.5mm, 1.7mm, 2mm and other typical but non-limiting widths, preferably 1.2mm-1.7mm.

[0054] In the negative electrode sheet provided in this embodiment, the width h of the second section 10 of the second region 3 arranged along the length direction of the current collector 1 is 1mm-2mm; for example, the width h can be 1mm, 1.2mm, 1.5mm, 1.7mm, 2mm and other typical but non-limiting widths, preferably 1.2mm-1.7mm.

[0055] In the negative electrode sheet provided in this embodiment, the width f of the third segment 11 of the second region 3 arranged along the width direction of the current collector 1 is 1 mm-2 mm; for example, the width f can be 1 mm, 1.2 mm, 1.5 mm, 1.7 mm, 2 mm and other typical but non-limiting widths, preferably 1.2 mm-1.7 mm.

[0056] In the negative electrode sheet provided in this embodiment, the width e of the fourth section 12 of the second region 3 arranged along the width direction of the current collector 1 is 1 mm-2 mm. For example, the width e can be 1 mm, 1.2 mm, 1.5 mm, 1.7 mm, 2 mm, etc., which are typical but non-limiting widths, and is preferably 1.2 mm-1.7 mm.

[0057] In the negative electrode sheet provided in this embodiment, the width c of the fifth segment 13 arranged along the length direction of the current collector 1 in the third region 4 is 0.5 mm-2 mm; for example, the width c can be typical but non-limiting widths such as 0.5 mm, 0.7 mm, 1 mm, 1.2 mm, 1.5 mm, 1.7 mm, 2 mm, etc., preferably 1 mm-1.5 mm.

[0058] In the negative electrode sheet provided in this embodiment, the width d of the sixth segment 14 of the third region 4 arranged along the length direction of the current collector 1 is 0.5 mm-2 mm; for example, the width d can be typical but non-limiting widths such as 0.5 mm, 0.7 mm, 1 mm, 1.2 mm, 1.5 mm, 1.7 mm, 2 mm, etc., preferably 1 mm-1.5 mm.

[0059] In the negative electrode sheet provided in this embodiment, the width b of the seventh segment 15 of the third region 4 arranged along the width direction of the current collector 1 is 0.5 mm-2 mm; for example, the width b can be typical but non-limiting widths such as 0.5 mm, 0.7 mm, 1 mm, 1.2 mm, 1.5 mm, 1.7 mm, 2 mm, etc., preferably 1 mm-1.5 mm.

[0060] In the negative electrode sheet provided in this embodiment, the width a of the eighth segment 16 of the third region 4 arranged along the width direction of the current collector 1 is 1 mm-2 mm. For example, the width a can be 1 mm, 1.2 mm, 1.5 mm, 1.7 mm, 2 mm, etc., which are typical but non-limiting widths, and is preferably 1.2 mm-1.7 mm.

[0061] The limitation of each size in the second region 3 and the third region 4 avoids the minimum waste of negative electrode active materials. By disassembling the negative electrode sheet in this embodiment after fast charging cycle, it is found that there is no lithium deposition in the negative electrode sheet.

[0062] In the negative electrode sheet provided in this embodiment, the eighth segment 16 of the third region 4 is suitable for connection with the pole ear 17. The current density at the connection with the pole ear 17 is relatively large during fast charging, and lithium deposition may occur. Therefore, the minimum width of the eighth segment 16 is larger than the minimum width of the other three segments in the third region 4 to avoid lithium deposition.

[0063] For the negative electrode sheet provided in this embodiment, when the battery fast charging requirement is higher, the values ​​of width g, width h, width f, width e and radius R are larger.

[0064] The preparation process of the negative electrode sheet is as follows: a whole sheet of the current collector 1 is divided into three areas according to the set size, and the first active material layer 5, the second active material layer 6 and the third active material layer 7 are coated in each area respectively, and then the current collector 1 is cut along the outer edge of the third active material layer 7 to obtain a negative electrode sheet.

[0065] Example 2

[0066] The present embodiment provides a specific implementation of a laminated battery, comprising a laminated positive electrode sheet and the negative electrode sheet described in Embodiment 1. The laminated battery has a high capacity density and energy density, and the specific shape of the laminated battery is not limited.

[0067] In the laminated battery provided in this embodiment, the first active material layer 5 and the second active material layer 6 in the positive electrode sheet and the negative electrode sheet are arranged opposite to each other, and the positive electrode sheet has a first projection in the direction in which the positive electrode sheet and the negative electrode sheet are stacked; the third active material layer 7 has a second projection in the direction in which the positive electrode sheet and the negative electrode sheet are stacked; wherein the first projection and the second projection at least partially do not overlap, and the outer contour of the second projection exceeds the outer contour of the first projection.

[0068] And "the first projection and the second projection at least partially do not overlap, and the outer contour of the second projection exceeds the outer contour of the first projection", that is, when the positive electrode sheet and the negative electrode sheet are stacked, the third active material layer 7 will partially exceed the positive electrode sheet, and, the present application sets the dimensions of each part of the third region 4, so that when the electrode sheet shifts during the production process, it can also be ensured that the third active material layer 7 will partially exceed the positive electrode sheet, thereby ensuring that lithium ions released from the positive electrode sheet due to the shift during the production process cannot be embedded, resulting in lithium deposition.

[0069] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the scope of protection of the present utility model.

Claims

1. A negative electrode sheet, characterized in that: include: A current collector (1) having at least one surface to be coated, wherein the surface to be coated is divided from the center to the periphery into a first region (2), a second region (3) and a third region (4) which are connected in sequence and surround each other; A first active material layer (5) is arranged in the first region (2); A second active material layer (6) is arranged in the second region (3); A third active material layer (7) is arranged in the third region (4), the coating surface density of the second active material layer (6) is less than the coating surface density of the first active material layer (5), and the coating surface density of the second active material layer (6) is greater than the coating surface density of the third active material layer (7).

2. The negative electrode sheet according to claim 1, characterized in that: The coating surface density of the first active material layer (5) is 1.05-1.15 times the coating surface density of the second active material layer (6).

3. The negative electrode sheet according to claim 1, characterized in that: The coating surface density of the third active material layer (7) is 0.75-0.9 times the coating surface density of the second active material layer (6).

4. The negative electrode sheet according to claim 1, characterized in that: The first area (2) is a rectangular structure, and the corner area (8) of the first area (2) is an arc-shaped structure.

5. The negative electrode sheet according to claim 4, characterized in that: The radius R of the corner area (8) is 1 mm-3 mm.

6. The negative electrode sheet according to claim 1, characterized in that: The width g of the first section (9) in the second region (3) arranged along the length direction of the current collector (1) is 1 mm to 2 mm; and / or, the width h of the second section (10) of the second region (3) arranged along the length direction of the current collector (1) is 1 mm-2 mm; and / or, the width f of the third section (11) of the second region (3) arranged along the width direction of the current collector (1) is 1 mm-2 mm; And / or, the width e of the fourth section (12) of the second region (3) arranged along the width direction of the current collector (1) is 1 mm-2 mm.

7. The negative electrode sheet according to claim 1, characterized in that: The width c of the fifth section (13) arranged along the length direction of the current collector (1) in the third region (4) is 0.5 mm to 2 mm; and / or, the width d of the sixth section (14) of the third region (4) arranged along the length direction of the current collector (1) is 0.5 mm-2 mm; and / or, the width b of the seventh section (15) of the third region (4) arranged along the width direction of the current collector (1) is 0.5 mm-2 mm; And / or, the width a of the eighth section (16) of the third region (4) arranged along the width direction of the current collector (1) is 1 mm-2 mm.

8. The negative electrode sheet according to claim 7, characterized in that: The eighth section (16) of the third region (4) is suitable for connecting to a pole lug (17).

9. A laminated battery, characterized in that: The invention comprises a stacked positive electrode sheet and a negative electrode sheet according to any one of claims 1 to 8.

10. The laminated battery according to claim 9, characterized in that: The first active material layer (5) and the second active material layer (6) in the positive electrode sheet and the negative electrode sheet are arranged opposite to each other; The positive electrode sheet has a first projection in the direction in which the positive electrode sheet and the negative electrode sheet are stacked; the third active material layer (7) has a second projection in the direction in which the positive electrode sheet and the negative electrode sheet are stacked; wherein the first projection and the second projection at least partially do not overlap, and the outer contour of the second projection exceeds the outer contour of the first projection.

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