Negative plate and battery cell

Abstract

The utility model provides a negative pole piece and cell, negative pole piece includes negative pole current collector, head conductive coating, intermediate conductive coating, tail conductive coating and negative pole active substance layer, the coating surface of negative pole current collector includes head area, intermediate area and tail area, the head conductive coating is connected to the head area, the intermediate conductive coating is connected to the tail area, and the tail conductive coating is connected to the tail area. The middle conductive coating is connected to the middle area, and the tail conductive coating is connected to the surface of the tail area; the negative active material layer covers the head conductive coating, the middle conductive coating and the tail conductive coating; the conductivity of the head conductive coating is smaller than that of the middle conductive coating, and the conductivity of the tail conductive coating is smaller than that of the middle conductive coating. According to the negative plate and the battery cell, lithium precipitation at the head part and the tail part of the negative plate can be reduced.

Description

Technical Field

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

[0002] Lithium plating is a situation that may occur during the use of lithium-ion batteries. Specifically, during the charging process of the battery, lithium ions are deintercalated from the positive electrode sheet (cathode) of the electric core and intercalated into the negative electrode sheet (anode) of the electric core. If the lithium ions deintercalated from the positive electrode sheet cannot be intercalated into the negative electrode sheet, then the lithium ions can only precipitate on the surface of the negative electrode sheet, thereby forming a gray substance. This phenomenon is called lithium plating. Lithium plating may cause the performance of the battery to decline or even lead to safety accidents.

[0003] Compared with the central region of the electric core, the head and tail of the electric core are more likely to have lithium plating. The problem of lithium plating at the head and tail of the electric core needs to be solved. Summary of the Utility Model

[0004] The utility model aims to solve at least one of the technical problems existing in the prior art. For this purpose, the utility model provides a negative electrode sheet, which is beneficial to reducing lithium plating at the head and tail of the electric core.

[0005] The utility model also provides an electric core including the above-mentioned negative electrode sheet.

[0006] The negative electrode sheet according to the first aspect embodiment of the utility model includes: a negative electrode current collector, the negative electrode current collector includes at least one coating surface, the coating surface includes a head region, a middle region and a tail region, the head region is used for connecting with a negative electrode tab, in the width direction of the negative electrode current collector, both ends of the middle region are respectively connected with the head region and the tail region, and, one side edge of the head region away from the middle region and one side edge of the tail region away from the middle region are respectively the two side edges of the negative electrode current collector; a head conductive coating, the head conductive coating is connected to the surface of the head region; a middle conductive coating, the middle conductive coating is connected to the surface of the middle region; a tail conductive coating, the tail conductive coating is connected to the surface of the tail region; a negative electrode active material layer, the surfaces of the head conductive coating, the middle conductive coating and the tail conductive coating facing away from the coating surface are all covered by the negative electrode active material layer; the conductivity of the head conductive coating is less than the conductivity of the middle conductive coating, and the conductivity of the tail conductive coating is less than the conductivity of the middle conductive coating.

[0007] The negative electrode sheet according to the first aspect embodiment of the present utility model has at least the following beneficial effects: The conductivity of the head of the negative electrode sheet is relatively low (compared with the middle part of the negative electrode sheet), and the conductivity of the tail of the negative electrode sheet is also relatively low (compared with the middle part of the negative electrode sheet). In this way, the electron migration rate and the lithium ion migration rate of the head and tail of the negative electrode sheet can be slowed down. Since the lithium ion migration rate is low, when the battery cell is charged, the number of lithium ions moving to the negative electrode sheet per unit time decreases. Even if lithium deposition occurs on the negative electrode sheet, the amount of lithium deposited on the surface of the negative electrode sheet per unit time is relatively small.

[0008] According to some embodiments of the present utility model, the conductivity of the head conductive coating at 25 °C is P 1 , 10 -7 S / cm ≤ P 1 ≤ 10 2 S / cm; the conductivity of the middle conductive coating at 25 °C is P 2 , P 2 ≥ 10 3 S / cm; the conductivity of the tail conductive coating at 25 °C is P 3 , 10 -7 S / cm ≤ P 3 ≤ 10 2 S / cm.

[0009] According to some embodiments of the present utility model, the material of the middle conductive coating is carbon black or graphite.

[0010] According to some embodiments of the present utility model, the material of the head conductive coating is a silicon-based material, and / or the material of the tail conductive coating is a silicon-based material.

[0011] According to some embodiments of the present utility model, the width of the negative electrode current collector is W 0 , the width of the middle region is W 2 , W 2 / W 0 > 0.5.

[0012] According to some embodiments of the present utility model, the width of the head conductive coating is W 1 , the width of the middle conductive coating is W 3 , W 0 = W 1 + W 2 + W 3 , 2mm ≤ W 1 ≤ 30mm, 2mm ≤ W 3 ≤ 30mm.

[0013] According to some embodiments of the present utility model, the thickness of the head conductive coating is H1 , 1 μm ≤ H 1 ≤ 20 μm; and / or, the thickness of the middle conductive coating is H 2 , 1 μm ≤ H 2 ≤ 20 μm; and / or, the thickness of the tail conductive coating is H 3 , 1 μm ≤ H 3 ≤ 20 μm.

[0014] According to some embodiments of the present invention, the conductivity of any one of the head conductive coating and the tail conductive coating is less than the conductivity of the negative active material layer.

[0015] According to some embodiments of the present invention, the negative electrode sheet includes: a negative electrode current collector, the negative electrode current collector includes at least one coating surface, the coating surface includes a head region, a middle region and a tail region, in the width direction of the negative electrode current collector, both ends of the middle region are respectively connected to the head region and the tail region; a head conductive coating, the head conductive coating is connected to the surface of the head region; a tail conductive coating, the tail conductive coating is connected to the surface of the tail region; a negative active material layer, the surface of the head conductive coating facing away from the coating surface, the middle region, and the surface of the tail conductive coating facing away from the coating surface are all covered by the negative active material layer; the conductivity of any one of the head conductive coating and the tail conductive coating is less than the conductivity of the negative active material layer.

[0016] The battery cell according to the second aspect embodiment of the present invention includes the negative electrode sheet as described in the first aspect embodiment.

[0017] The battery cell according to the second aspect embodiment of the present invention has the same beneficial effects as the negative electrode sheet of the first aspect embodiment, and will not be described repeatedly here.

[0018] The additional aspects and advantages of the present invention will be partially given in the following description, partially become apparent from the following description, or be understood through the practice of the present invention. Description of the Drawings

[0019] The following further describes the present invention in conjunction with the drawings and embodiments, where:

[0020] Figure 1 is a plan view of the negative electrode current collector in the first embodiment of the present invention;

[0021] Figure 2 is a plan view of the state of the negative electrode current collector in the first embodiment of the present invention after the conductive coating is provided;

[0022] Figure 3Cross-sectional view of the negative electrode sheet in the first embodiment of the present utility model;

[0023] Figure 4 Cross-sectional view of the negative electrode sheet in the second embodiment of the present utility model.

[0024] Reference numerals:

[0025] 100 - Negative electrode sheet, 101 - Negative electrode current collector, 102 - Head region, 103 - Intermediate region, 104 - Tail region, 105 - Coated surface, 106 - Head conductive coating, 107 - Intermediate conductive coating, 108 - Tail conductive coating, 109 - Negative electrode active material layer. Detailed description of the embodiments

[0026] The embodiments of the present utility model will be described in detail below. The examples of the embodiments are shown in the drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are only used to explain the present utility model and should not be construed as a limitation of the present utility model.

[0027] In the description of the present utility model, it should be understood that the orientation or positional relationship indicated by terms such as up, down, front, back, left, right, etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present utility model 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 thus should not be construed as a limitation of the present utility model.

[0028] In the description of the present utility model, the meaning of several is more than one, the meaning of multiple is more than two, greater than, less than, exceeding, etc. are understood as not including the present number, and above, below, within, etc. are understood as including the present number. If the first and second are described only for the purpose of distinguishing technical features, they should not be construed as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the sequence relationship of the indicated technical features.

[0029] In the description of the present utility model, unless otherwise clearly defined, words such as setting, installing, connecting, etc. should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meanings of the above words in the present utility model in combination with the specific content of the technical solution.

[0030] Figure 1 Shows the negative electrode current collector 101 of the first embodiment of the present utility model, Figure 2 Shows the state of the negative electrode current collector 101 after being provided with a conductive coating, Figure 3 Shows the hierarchical structure of the negative electrode sheet 100. The negative electrode sheet 100 of the first embodiment is applicable to a wound-type battery cell. AsFigures 1 to 3 As shown in the figure, the negative electrode sheet 100 includes a negative electrode current collector 101, a head conductive coating 106, an intermediate conductive coating 107, a tail conductive coating 108, and a negative electrode active material layer 109.

[0031] The negative electrode current collector 101 is provided as a copper foil. As Figure 1 shown in the figure, the negative electrode current collector 101 includes at least one coating surface 105. The coating surface 105 includes a head region 102, an intermediate region 103, and a tail region 104. In the width direction of the negative electrode current collector 101, both ends of the intermediate region 103 are respectively connected to the head region 102 and the tail region 104. And, one side edge of the head region 102 away from the intermediate region 103 is the front side edge of the negative electrode current collector 101, and one side edge of the tail region 104 away from the intermediate region 103 is the rear side edge of the negative electrode current collector 101. The head region 102, the intermediate region 103, and the tail region 104 are all rectangular. As Figure 3 shown in the figure, the two end faces of the negative electrode current collector 101 in its own thickness direction are respectively two coating surfaces 105, and each coating surface 105 is coated with a conductive coating. Please refer to Figures 1 to 3 , in this embodiment, the width direction of the negative electrode current collector 101 is the front-rear direction, the length direction of the negative electrode current collector 101 is the left-right direction, and the thickness direction of the negative electrode current collector 101 is the up-down direction.

[0032] Please refer to Figure 1 and Figure 2 , the head conductive coating 106 is connected to the head region 102, the intermediate conductive coating 107 is connected to the intermediate region 103, and the tail conductive coating 108 is connected to the tail region 104. As Figure 3 shown in the figure, there is one head conductive coating 106 provided on each of the upper and lower sides of the head region 102, one intermediate conductive coating 107 provided on each of the upper and lower sides of the intermediate region 103, and one tail conductive coating 108 provided on each of the upper and lower sides of the tail region 104. The conductivity of the head conductive coating 106 is less than the conductivity of the intermediate conductive coating 107, and the conductivity of the tail conductive coating 108 is less than the conductivity of the intermediate conductive coating 107.

[0033] It should be noted that the head conductive coating 106 does not necessarily need to completely cover the head region 102. The head conductive coating 106 may be provided with an ear welding groove (not shown), a part of the head region 102 is exposed in the ear welding groove, and the negative electrode ear (not shown) is welded to the exposed part of the head region 102.

[0034] As Figure 3As shown, the one-side surface of the head conductive coating 106 facing away from the negative current collector 101, the one-side surface of the middle conductive coating 107 facing away from the negative current collector 101, and the one-side surface of the tail conductive coating 108 facing away from the negative current collector 101 are all covered by the negative active material layer 109. Since the negative electrode sheet 100 is applied to a lithium-ion battery, the negative active material may include graphite, a binder, and a conductive agent.

[0035] The following explains why lithium deposition is likely to occur at the head and tail of the battery cell in the prior art. In the prior art, when the coating equipment coats the active material on the current collector, the coating effect may be uneven; when the rolling equipment rolls the electrode sheet, the pressure applied by the rolling equipment is uneven. This results in an uneven thickness of the active material layer. A common situation is: if the gap between the middle of the positive electrode sheet and the middle of the negative electrode sheet 100 is used as a reference benchmark, then the gap between the head of the positive electrode sheet and the head of the negative electrode sheet 100 is larger, and the gap between the tail of the positive electrode sheet and the tail of the negative electrode sheet 100 is smaller. At the head of the battery cell, the gap between the positive and negative electrode sheets 100 is larger, and the path for lithium ions to migrate from the head of the positive electrode sheet to the head of the negative electrode sheet 100 is longer. It is difficult for lithium ions to be embedded deep into the negative active material of the negative electrode sheet 100. Lithium ions mainly obtain electrons on the surface of the negative active material, resulting in lithium deposition at the head of the negative electrode sheet 100. At the tail of the battery cell, although the distance between the positive and negative electrode sheets 100 is smaller, if the gap between the positive and negative electrode sheets 100 is too small, it will lead to less electrolyte between the positive and negative electrode sheets 100, resulting in difficulty in fully wetting the tail of the negative electrode sheet 100 with the electrolyte, and further resulting in lithium deposition at the tail of the negative electrode sheet 100.

[0036] For the negative electrode sheet 100 of the present invention, the conductivity of the head of the negative electrode sheet 100 is relatively low (compared with the middle of the negative electrode sheet 100), and the conductivity of the tail of the negative electrode sheet 100 is also relatively low (compared with the middle of the negative electrode sheet 100). This can slow down the electron migration rate at the head and tail of the negative electrode sheet 100, thereby reducing the migration rate of lithium ions. Since the migration rate of lithium ions is low, when the battery cell is charged, the number of lithium ions moving to the negative electrode sheet 100 per unit time decreases. Even if lithium deposition occurs on the negative electrode sheet 100, the amount of lithium deposited on the surface of the negative electrode sheet 100 per unit time is also relatively small (compared with the prior art). Among them, taking Figure 3 as an example, the head of the negative electrode sheet 100 is the part of the negative electrode sheet 100 located in front of the straight line L 2 The middle of the negative electrode sheet 100 is the part of the negative electrode sheet 100 located between the straight line L 1 and the straight line L 2 The tail of the negative electrode sheet 100 is the part of the negative electrode sheet 100 located behind the straight line L 1

[0037] The conductivity of the head conductive coating 106 at room temperature is P​1 , 10 -7 S / cm ≤ P 1 ≤ 10 2 S / cm. In the present utility model, normal temperature refers to 25 °C. The conductivity of the middle conductive coating 107 at normal temperature is P 2 , P 2 ≥ 10 3 S / cm. The conductivity of the tail conductive coating 108 at normal temperature is P 3 , 10 -7 S / cm ≤ P 3 ≤ 10 2 S / cm. Among them, P 1 and P 3 can be equal or unequal. If P 1 and P 3 are equal, then the materials of the head conductive coating 106 and the tail conductive coating 108 can be the same. The above settings make there be a large gap in conductivity between the head conductive coating 106 and the middle conductive coating 107, and make there be a large gap in conductivity between the tail conductive coating 108 and the middle conductive coating 107, thereby being beneficial to reducing the risk of lithium deposition at the head and tail of the negative electrode sheet 100.

[0038] The material of the middle conductive coating 107 can be set as carbon black or graphite. Carbon black and graphite have high conductivity, and their conductivity is greater than 10 3 S / cm. Moreover, due to the low cost of carbon black and graphite, setting the material of the middle conductive coating 107 as carbon black or graphite is beneficial to reducing the cost of the negative electrode sheet 100.

[0039] In order to make the conductivity of the head conductive coating 106 less than 10 2 S / cm, the material of the head conductive coating 106 can be set as a silicon-based material, such as silicon oxide, silicon carbide, silicon boride. The material of the head conductive coating 106 can also be set as a mixture of sodium carboxymethyl cellulose and a conductive agent, and the conductive agent can be one of carbon black, carbon nanotubes, and graphene. Similarly, the material of the tail conductive coating 108 can also be set as a silicon-based material or a mixture of sodium carboxymethyl cellulose and a conductive agent. Since the theoretical specific capacity of silicon (4200 mAh / g) is relatively high, coating a silicon-based compound with low conductivity in the head region 102 and the tail region 104 can not only improve lithium deposition at the edge of the electrode sheet, but also increase the energy density of the battery.

[0040] The conductivity of any one of the head conductive coating 106 and the tail conductive coating 108 is less than the conductivity of the negative electrode active material layer 109. Such a setting can prevent the conductivity of the head conductive coating 106 and the tail conductive coating 108 from being too high.

[0041] As shown Figure 1 in the figure, the width of the negative electrode current collector 101 is W 0 (W 0 is not marked in the attached drawing), the width of the head region 102 is W 1 , the width of the middle region 103 is W 2 , and the width of the tail region 104 is W 3 , and W 0 = W 1 + W 2 + W 3 . In some embodiments, W 2 / W 0 > 0.5. The overall conductivity of the negative electrode sheet 100 is related to W 1 , W 2 and W 3 . The larger W 2 is, the larger the area of the middle conductive coating 107 is, and the better the overall conductivity of the negative electrode sheet 100 is. Therefore, W 2 / W 0 > 0.5 is beneficial to avoiding poor overall conductivity of the negative electrode sheet 100 or the battery cell. Based on the relationship between W 2 and W 0 and the width of common electrode sheets, W 1 and W 3 can satisfy: 2 mm ≤ W 1 ≤ 30 mm, 2 mm ≤ W 3 ≤ 30 mm. W 1 and W 3 can be equal or unequal.

[0042] The thickness of the head conductive coating 106 is H 1 , and H 1 satisfies: 1 μm ≤ H 1 ≤ 20 μm. H 1 not less than 1 μm enables the head conductive coating 106 to have a sufficiently large thickness, so that the head conductive coating 106 can reduce the conductivity of the head of the negative electrode sheet 100; H 1 not greater than 20 μm can prevent the thickness of the head conductive coating 106 from being too large, thereby preventing the energy density of the battery cell from being too low. Similarly, the thickness of the middle conductive coating 107 is H 2 , and H 2 satisfies: 1 μm ≤ H 2 ≤ 20 μm. Similarly, the thickness of the tail conductive coating 108 is H 3 , and H 3 satisfies: 1 μm ≤ H 3 ≤ 20 μm. H 2 and H 3The beneficial effects satisfying the above conditions can refer to the beneficial effects of 1 μm ≤ H1 ≤ 20 μm, and will not be described repeatedly here.

[0043] In addition, H 1 , H 2 and H 3 can also satisfy: H 1 = H 2 = H 3 ( Figure 3 where H 2 and H 3 are not marked in Figure 3 ). Such a setting makes the head conductive coating 106, the middle conductive coating 107 and the tail conductive coating 108 coated on the same coating surface 105 flush (as shown in

[0044] Figure 4 ), thereby facilitating the coating equipment to coat the negative active material.

[0045] FIG.

[0046] The present utility model also provides an electric cell, which includes the negative electrode sheet 100 in any of the above embodiments. The electric cell further includes a positive electrode sheet and a separator. The positive electrode sheet includes a positive electrode current collector (such as aluminum foil) and a positive electrode active material coated on the surface of the positive electrode current collector. The positive electrode active material may include lithium cobaltate. The separator is disposed between the positive electrode sheet and the negative electrode sheet 100.

[0047] The applicant has conducted a 1000 - week long - cycle test on the existing - technology electric cell (i.e., the comparative example below) and the electric cell of the present utility model, and the test results are as follows:

[0048]

[0049] Among them, the battery cells of the comparative example, Test Object 1, and Test Object 2 are of the same type of battery cell, that is, all three are wound battery cells. Moreover, the positive active material and the negative active material of these three battery cells are the same. In addition, the negative electrode sheet of the battery cell in the comparative example is not provided with a head conductive coating 106, a middle conductive coating 107, and a tail conductive coating 108. In the comparative example, the negative active material is directly in contact with the negative current collector 101. The battery cell of Test Object 1 uses the negative electrode sheet 100 in the first embodiment above, and the battery cell of Test Object 2 uses the negative electrode sheet 100 in the second embodiment above.

[0050] As can be seen from the above table, the negative electrode sheet 100 of the present invention can reduce the lithium plating at the head and tail of the negative electrode sheet 100. Moreover, the negative electrode sheet 100 of the present invention can also improve the bulging condition of the battery cell (the volume expansion of Test Object 1 and Test Object 2 is smaller than that of the comparative example).

[0051] In addition, for the size parameters of the negative electrode sheet 100 mentioned above, the applicant also conducted experiments on the battery cells using the negative electrode sheet 100, and the experimental data are as follows:

[0052]

[0053] Among them, "W 1 &W 3 " means that the values of W 1 and W 3 are equal, and "H 1 &H 3 " means that the values of H 1 and H 3 are equal. For example, for the second test object, its W 1 and W 3 are both 2 mm, and its H 1 and H 3 are both 1 μm. The "95% SOC charging speed" refers to the time required to charge the battery cell using the negative electrode sheet 100 to 95% of the battery power. The "lithium plating area after 1000 cycles" refers to the proportion of the area where lithium plating occurs on the surface of the negative electrode sheet 100 after the battery cell using the negative electrode sheet 100 has undergone 1000 cycles.

[0054] As can be seen from the above experimental data, compared with the case where both W 1 and W 3 are 0, when W 1 and W 3 are between 2 - 30 mm, the lithium plating condition of the negative electrode sheet 100 is relatively light. Compared with the case where both H 1 and H 3 are 0, when H 1 and H 3When it is between 1 and 20 μm, the lithium deposition situation of the negative electrode sheet 100 is relatively light. Among them, the lithium depositions of the 6th, 7th, 9th, and 10th experimental objects are all relatively small. Relatively speaking, when W 1 =W 3 =10 mm, and H 1 =H 3 =10 μm, the charging speed of the battery cell is relatively high. In addition, when W 1 and W 3 remain unchanged, the larger H 1 and H 3 are, the less lithium deposition there is. When H 1 and H 3 remain unchanged, the larger W 1 and W 3 are, the less lithium deposition there is.

[0055] In the description of the present utility model, the descriptions with reference to terms such as "one embodiment", "some embodiments", "schematic embodiments", "examples", "specific examples", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present utility model. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

Claims

1. A negative electrode sheet, characterized in that: include: A negative electrode current collector, the negative electrode current collector comprising at least one coated surface, the coated surface comprising a head region, a middle region and a tail region, the head region being used to connect to the negative electrode ear, and in the width direction of the negative electrode current collector, two ends of the middle region are respectively connected to the head region and the tail region, and a side edge of the head region away from the middle region and a side edge of the tail region away from the middle region are respectively two side edges of the negative electrode current collector; a head conductive coating, the head conductive coating being connected to the head region; an intermediate conductive coating connected to the intermediate region; a tail conductive coating, the tail conductive coating being connected to the tail region; A negative electrode active material layer, wherein a surface of the head conductive coating layer facing away from the coating surface, a surface of the middle conductive coating layer facing away from the coating surface, and a surface of the tail conductive coating layer facing away from the coating surface are all covered by the negative electrode active material layer; The conductivity of the head conductive coating is lower than that of the middle conductive coating, and the conductivity of the tail conductive coating is lower than that of the middle conductive coating.

2. The negative electrode sheet according to claim 1, characterized in that: The conductivity of the head conductive coating at 25°C is P1,10 -7 S / cm≤P1≤10 2 S / cm; The conductivity of the intermediate conductive coating at 25°C is P2, P2≥10 3 S / cm; The conductivity of the tail conductive coating at 25°C is P3,10 -7 S / cm≤P3≤10 2 S / cm.

3. The negative electrode sheet according to claim 1, characterized in that: The material of the intermediate conductive coating is carbon black or graphite.

4. The negative electrode sheet according to claim 1, characterized in that: The material of the head conductive coating is a silicon-based material, and / or the material of the tail conductive coating is a silicon-based material.

5. The negative electrode sheet according to claim 1, characterized in that: The width of the negative electrode current collector is W0, the width of the middle region is W2, and W2 / W0>0.

5.

6. The negative electrode sheet according to claim 5, characterized in that: The width of the head conductive coating is W1, the width of the middle conductive coating is W3, W0= W1+ W2+ W3, 2mm≤W1≤30mm, 2mm≤W3≤30mm.

7. The negative electrode sheet according to claim 1, characterized in that: The thickness of the conductive coating on the head is H1, 1 μm≤H1≤20 μm; and / or, the thickness of the intermediate conductive coating is H2, 1 μm≤H2≤20 μm; And / or, the thickness of the tail conductive coating is H3, 1 μm≤H3≤20 μm.

8. The negative electrode sheet according to claim 1, characterized in that: The conductivity of any one of the head conductive coating layer and the tail conductive coating layer is lower than the conductivity of the negative electrode active material layer.

9. A negative electrode sheet, characterized in that: include: A negative electrode current collector, the negative electrode current collector comprising at least one coating surface, the coating surface comprising a head region, a middle region and a tail region, and in the width direction of the negative electrode current collector, two ends of the middle region are connected to the head region and the tail region respectively; a head conductive coating, the head conductive coating being connected to the head region; a tail conductive coating, the tail conductive coating being connected to the tail region; A negative electrode active material layer, wherein the surface of the head conductive coating layer facing away from the coating surface, the middle region, and the surface of the tail conductive coating layer facing away from the coating surface are all covered by the negative electrode active material layer; The conductivity of any one of the head conductive coating layer and the tail conductive coating layer is lower than the conductivity of the negative electrode active material layer.

10. A battery cell, characterized in that: The invention comprises the negative electrode sheet as claimed in any one of claims 1 to 9.

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