Negative electrode sheet, battery, battery pack, and electric device

Abstract

A negative electrode sheet (100), a battery (300), a battery pack, and an electric device, which relate to the technical field of secondary batteries. The negative electrode sheet (100) comprises a current collector (110), a tab (130) connected to one side of the current collector (110), a first active material layer (150), and a second active material layer (170). The front and back surfaces of the current collector (110) are coated with the first active material layer (150), and the thickness (150) of the first active material layer is gradually increased and then gradually reduced from the tab (130) side to the side away from the tab (130). The outer side of the first active material layer (150) is coated with the second active material layer (170), and the thickness of the second active material layer (170) is gradually reduced then gradually increased from the tab (130) side to the side away from the tab (130). The negative electrode sheet (100) provided herein can alleviate the problem of lithium plating, and can improve the safety of the battery (300).

Description

Negative electrode sheets, batteries, battery packs and electrical equipment

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This disclosure claims priority to Chinese patent application number 202311506582.6, filed with the Chinese Patent Office on November 13, 2023, and entitled “Negative Electrode Sheet, Battery and Battery Pack,” the entire contents of which are incorporated by reference into this disclosure. Technical Field

[0003] The present disclosure relates to the field of secondary batteries, and in particular to a negative electrode sheet, a battery, a battery pack, and an electrical device. Background Art

[0004] Secondary batteries, also known as rechargeable batteries or storage batteries, are batteries that can be recharged after discharge to reactivate the active materials and continue to be used. By leveraging the reversibility of chemical reactions, a new battery can be constructed. That is, after a chemical reaction is converted into electrical energy, the electrical energy can be used to repair the chemical system, and then the chemical reaction can be converted back into electrical energy. Secondary batteries are widely used in new energy vehicles and energy storage devices.

[0005] With the development of fast charging technology, lithium batteries in related technologies are prone to metallic lithium deposition on the positive and negative electrode ears corresponding to the negative electrode sheet when charging at a high rate. The metallic lithium deposition will continue to form lithium dendrites, thereby increasing the risk of thermal runaway of the battery.

[0006] Summary of the Invention

[0007] The objectives of the present disclosure include, for example, providing a negative electrode sheet, a battery, a battery pack, and an electrical device, which can improve the problem of lithium plating on the negative electrode sheet.

[0008] The embodiments of the present disclosure may be implemented as follows:

[0009] In a first aspect, the present disclosure provides a negative electrode sheet, comprising:

[0010] current collector;

[0011] a tab connected to one side of the current collector;

[0012] a first active material layer, the first active material layer being coated on the front and back sides of the current collector, and the first active side material layer gradually becoming thicker and then thinner from the side of the tab toward the side away from the tab; and

[0013] The second active material layer is coated on the outer side of the first active material layer, and the thickness of the second active material layer gradually becomes thinner from the side of the electrode tab to the side away from the electrode tab, and then gradually becomes thicker.

[0014] In an optional embodiment, the first active material layer is a high specific energy active material layer, and the kinetic performance of the second active material layer is greater than the kinetic performance of the first active material layer.

[0015] In an optional embodiment, the sum of the thickness of the first active material layer and the thickness of the second active material layer at any position on the current collector is equal.

[0016] In an optional embodiment, the ratio of the thickness of the first active material layer to the thickness of the second active material layer is X, and the value range of X is 0<X≤10.

[0017] In an optional embodiment, the ratio of the thickness of the first active material layer to the thickness of the second active material layer gradually increases from one side of the electrode tab to a side away from the electrode tab, and then gradually decreases.

[0018] In an alternative embodiment, the first active material layer and the second active material layer have different areal densities.

[0019] In an optional embodiment, the first active material layer and the second active material layer are asymmetric structures in the extension direction of the electrode tab.

[0020] In an optional embodiment, the particle size distribution of the first active material layer is larger than the particle size distribution of the second active material layer.

[0021] In an optional embodiment, the main material of the first active material layer is small-particle blended graphite;

[0022] The main material of the second active material layer is a mixture of large and small particles of graphite.

[0023] In an optional embodiment, the current collector and the tab are integrally formed.

[0024] In an optional embodiment, the negative electrode sheet is symmetrically arranged with respect to the current collector in the thickness direction of the negative electrode sheet.

[0025] In an optional embodiment, the current collector is made of one of a metal foil, a composite foil and a coated foil.

[0026] In a second aspect, the present disclosure provides a battery comprising a housing, a bare cell, and an electrode, wherein the bare cell comprises a positive electrode sheet, a separator, and the negative electrode sheet described in any one of the aforementioned embodiments;

[0027] The positive electrode sheet, the separator, the negative electrode sheet and the separator are stacked in sequence;

[0028] The bare battery cell is installed in the shell, and the tab is electrically connected to the pole.

[0029] In a third aspect, the present disclosure provides a battery pack comprising a plurality of batteries described in the aforementioned embodiments, wherein the plurality of batteries are connected in parallel or in series.

[0030] In a fourth aspect, the present disclosure provides an electric device, comprising an electric device body and the battery described in the aforementioned embodiment, wherein the battery is arranged in the electric device body to supply power to the electric device body.

[0031] The beneficial effects of the negative electrode sheet, battery, battery pack, and electrical equipment provided by the embodiments of the present disclosure include, for example:

[0032] In this application, a first active material layer is applied to the front and back of the current collector, and the thickness of the first active side material layer gradually increases from the side of the tab to the side away from the tab, and then gradually decreases. A second active material layer is applied to the outside of the first active material layer, and the thickness of the second active material layer gradually decreases from the side of the tab to the side away from the tab, and then gradually increases. In this way, the high potential area between the positive and negative electrodes in the battery formed by the stacking can increase the ion diffusion rate, reduce the ion transfer impedance, and reduce the risk of lithium plating. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present disclosure and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0034] FIG1 is a schematic structural diagram of a battery provided in an embodiment of the present disclosure;

[0035] FIG2 is a schematic structural diagram of a negative electrode sheet provided in an embodiment of the present disclosure;

[0036] FIG3 is a graph showing the local voltage of the positive electrode sheet and the local voltage of the negative electrode sheet during battery charging;

[0037] FIG4 shows the effective voltage distribution between the positive electrode and the negative electrode when the battery is charging.

[0038] Icon: 100 - negative electrode sheet; 110 - current collector; 130 - tab; 150 - first active material layer; 170 - second active material layer; 300 - battery; 310 - casing; 330 - pole. DETAILED DESCRIPTION

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present disclosure more clear, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present disclosure. Obviously, the described embodiments are only some of the embodiments of the present disclosure, but not all of them. Generally, the components of the embodiments of the present disclosure described and shown in the drawings herein can be arranged and designed in various different configurations.

[0040] Therefore, the following detailed description of the embodiments of the present disclosure provided in the accompanying drawings is not intended to limit the scope of the present disclosure as claimed, but merely represents selected embodiments of the present disclosure. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present disclosure without creative effort shall fall within the scope of protection of the present disclosure.

[0041] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0042] In the description of the present disclosure, it should be noted that if the terms "upper", "lower", "inside", "outside", etc. appear, the orientation or position relationship indicated is based on the orientation or position relationship shown in the accompanying drawings, or is the orientation or position relationship in which the invented product is usually placed when used. It is only for the convenience of describing the present disclosure and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present disclosure.

[0043] In addition, the terms "first", "second", etc., if used, are merely used to distinguish and describe, and should not be understood as indicating or implying relative importance.

[0044] It should be noted that, in the absence of conflict, the features in the embodiments of the present disclosure may be combined with each other.

[0045] Referring to Figure 1 , this embodiment provides a battery pack that can serve as the power source for new energy vehicles. It can also be used in energy storage devices to store electrical energy. It can also be used to power power tools.

[0046] Typically, a battery pack consists of a housing, multiple battery cells 300, and a battery management unit (BMU). The battery cells 300 are typically connected in series or parallel to form one or more battery modules. The battery modules are mounted within the housing. The BMU is electrically connected to the batteries to monitor parameters such as voltage and temperature of each battery cell 300.

[0047] In this embodiment, the battery 300 comprises a housing 310, a bare cell, and an electrode 330. The bare cell includes a positive electrode sheet, a separator, and a negative electrode sheet 100. The positive electrode sheet, separator, negative electrode sheet 100, and separator are stacked in sequence. The bare cell is mounted within the housing 310. The positive tab of the positive electrode sheet and the tab 130 of the negative electrode sheet are both electrically connected to the electrode 330.

[0048] Generally, the electrodes 330 include a positive electrode 330 and a negative electrode 330, which are mounted opposite each other on opposite sides of the housing 310. The positive tab of the positive electrode sheet is electrically connected to the positive electrode 330. The tab 130 of the negative electrode sheet 100 is connected to the negative electrode 330.

[0049] It should be noted that the battery 300 is a battery with opposite-side tabs. For example, the positive tab of the bare cell connected to the positive electrode sheet extends out from the left side of the bare cell, while the tab 130 connected to the negative electrode sheet 100 extends from the right side. The double-sided tab method can greatly improve the safety of the battery pack 300. On the one hand, the battery cells with tabs at both ends can be monitored and controlled separately. If an abnormal situation occurs, it can be handled separately in time to reduce the risk of accidents. On the other hand, the tabs at both ends can extend the length of the battery terminal, increase the contact area between the battery and the connector, reduce the contact resistance, and thus reduce the possibility of battery heating and fire. The battery 300 can be a soft-pack battery, a square-shell battery, or a blade battery. Of course, the battery can also be a cylindrical cell. The battery 300 can be prepared by a lamination process, a winding process, or a combination of lamination and winding processes.

[0050] The inventors discovered that during the charging process of the battery 300, lithium ions escape from the positive electrode, pass through the separator, and then embed into the active material of the negative electrode 100. The main reason for the lithium deposition on the negative electrode 100 is that the current is too large, resulting in excessive local polarization and too low a negative electrode potential, reaching the deposition potential of metallic lithium, thereby depositing metallic lithium on the surface of the negative electrode. The main reason for the above-mentioned lithium deposition phenomenon is that there is a voltage drop between the positive and negative electrodes 100 of the battery 300, resulting in an uneven distribution of potential on the negative electrode 100. Therefore, at the same charge rate, the potential of the negative electrode 100 corresponding to the positive electrode tab side of the positive electrode sheet and the negative electrode tab 130 side of the negative electrode sheet is relatively large, which in turn leads to lithium deposition.

[0051] To solve the above problems, this embodiment proposes a negative electrode plate, which can improve the lithium plating problem caused by the potential difference.

[0052] 2 , in this embodiment, the negative electrode sheet 100 includes a current collector 110, a tab 130 connected to one side of the current collector 110, a first active material layer 150, and a second active material layer 170. The first active material layer 150 is applied to the front and back sides of the current collector 110, and the thickness of the first active material layer gradually increases from one side of the tab 130 to the side away from the tab 130, and then gradually decreases. The second active material layer 170 is applied to the outside of the first active material layer 150, and the thickness of the second active material layer 170 gradually decreases from one side of the tab 130 to the side away from the tab 130, and then gradually increases.

[0053] In this embodiment, a first active material layer 150 is applied to both the front and back sides of the current collector 110, with the thickness of the first active material layer gradually increasing from the side facing the tab 130 to the side away from the tab 130, and then gradually becoming thinner. A second active material layer 170 is applied to the outside of the first active material layer 150, with the thickness of the second active material layer 170 gradually decreasing from the side facing the tab 130 to the side away from the tab 130, and then gradually becoming thicker. This improves the ion diffusion rate in the high-potential region between the positive and negative electrodes 100 of the battery 300, reduces ion transfer resistance, and mitigates the risk of lithium plating.

[0054] In this embodiment, the first active material layer 150 is a high specific energy active material layer, and the kinetic performance of the second active material layer 170 is greater than that of the first active material layer 150 .

[0055] It should be noted that in lithium-ion batteries 300, the negative electrode material is where lithium ions are stored and released. Typical negative electrode materials include graphite, silicon-based materials, metal oxides, etc. Among them, graphite is one of the most widely used negative electrode materials.

[0056] High-energy-density anode active materials are those with a high specific capacity (mAh / g) and a low voltage plateau (V). Specific capacity refers to the amount of lithium ions a unit mass of anode material can store, while the voltage plateau refers to the range of lithium ion potential changes during charge and discharge. High-energy-density active materials have the advantages of increasing battery energy density, extending battery life, and reducing battery costs.

[0057] In this embodiment, the first active material layer 150 is a high specific energy active material layer relative to the second active material layer 170 , that is, the specific capacity of the active material in the first active material layer 150 is greater than that in the second active material layer 170 .

[0058] The greater kinetic performance of the second active material layer 170 than that of the first active material layer 150 indicates that the kinetics of the active material in the second active material layer 170 are superior to those of the active material in the first active material layer 150. The kinetic properties of negative electrode materials primarily include charge and discharge rates, cycle stability, and activation processes. Differences in the active material layer's microstructure, surface treatment, and synthesis method can all lead to differences in the kinetic performance of the active material layer.

[0059] When charging the battery 300, the voltage applied to the positive electrode post 330 and the negative electrode post 330 is the potential difference between the two posts 330, the positive and negative electrodes of the battery 300, and is Vapp. Without considering the resistance at the connection, this voltage corresponds to the potential difference between the tab 130 of the positive electrode sheet and the tab 130 of the negative electrode sheet. Each negative electrode sheet 100 experiences a voltage drop at the tab 130 and at locations further away from the tab 130, with the voltage drop generally increasing with distance from the tab 130.

[0060] The effective voltage (V) is the voltage between the positive and negative electrodes 100 at any specific location in the battery. In a Cartesian coordinate system, the X and Y axes are parallel to the electrodes, and the Z axis is perpendicular to the electrodes. At the point where the effective voltage is measured, the positive and negative electrodes 100 share the same X and Y coordinates, but the Z axis is different.

[0061] Figure 3 shows the local voltage curves of the positive electrode sheet and the negative electrode sheet 100 during charging. The upper portion of the horizontal axis represents the positive electrode sheet, and the lower portion represents the negative electrode sheet 100. The charging method can be one or a combination of constant voltage charging, constant current charging, pulse charging, or other charging methods. Because the current passing through the current collector 110 generates a voltage drop, the potential V1 at the tab of the positive electrode sheet gradually decreases toward the corresponding tab 130 of the negative electrode sheet 100, reaching V2 at the corresponding tab 130 of the negative electrode sheet 100, forming the local voltage curve of the positive electrode sheet. Similarly, the potential V4 at the tab 130 of the negative electrode sheet 100 gradually decreases toward the corresponding tab of the positive electrode sheet, until it drops to V3 at the corresponding tab of the positive electrode sheet. The voltage value applied to the tab of the positive electrode sheet and the tab 130 of the negative electrode sheet 100 is V4-V1. The local voltage corresponding to the same X value of the positive and negative electrode sheets 100 is the difference between the curve and the corresponding position, which is called the effective voltage Ve, that is, the curve shown in Figure 3.

[0062] As can be seen from Figure 4, the effective voltage of the positive and negative electrodes 100 is distributed differently at different positions of the electrodes. The closer to the tabs 130, the greater the effective voltage. According to the effective voltage distribution of the positive and negative electrodes 100 in the battery 300. Therefore, the effective voltage is large at the tabs 130 on both sides of the battery (the tabs of the positive electrode and the tabs 130 of the negative electrode 100), and the ion transfer rate is fast. It is necessary to set more negative electrode materials with good kinetic properties in the areas on both sides to increase the ion diffusion rate, reduce the ion transfer impedance, and reduce the risk of lithium plating. More high-specific-energy active materials can be configured at low potentials to increase the energy density of the battery cell. Thus, the overall electrical properties can take into account both high specific energy and fast charging.

[0063] It should be further explained that, in order to meet the above requirements, the second active material layer 170 is a negative electrode material with better kinetics, such as a negative electrode material with a high degree of graphitization, a large relative area, and a small polarization. The first active material layer 150 is a high specific energy negative electrode material, such as a negative electrode material with a wide particle size distribution.

[0064] 2 , in this embodiment, the particle size distribution of the first active material layer 150 is greater than that of the second active material layer 170 , thereby obtaining a first active material layer 150 with good kinetics and a second active material layer 170 with high specific energy.

[0065] Specifically, the primary material of the first active material layer 150 is small-particle blended graphite. The primary material of the second active material layer is large- and small-particle blended graphite. For example, the second active material layer 170 is prepared by mixing large- and small-particle blended graphite, a binder, a conductive agent, and a first solvent in a specific ratio to form a slurry for the second active material layer 170. The first active material layer 150 is prepared by mixing small-particle blended graphite, a binder, a conductive agent, and a second solvent in a specific ratio to form a slurry for the first active material layer 150. This results in a second active material layer 170 with improved kinetics and a first active material layer 150 with high specific energy.

[0066] Graphite, as the negative electrode material for lithium-ion batteries, exists in two forms within the battery 300: small-particle graphite, typically with a particle size of less than 10 μm. The other is large-particle graphite, typically with a particle size greater than 10 μm. Small-particle graphite, due to its small size and large surface area, facilitates contact between the electrode material of the battery 300 and the electrolyte, thereby improving the discharge rate of the battery 300. Furthermore, small-particle graphite has excellent lithium intercalation properties and can accommodate lithium ions well, thereby increasing the capacity of the battery 300. Large-particle graphite, due to its large size, can maintain structural stability within the battery 300 and increase the cycle life of the battery 300. Furthermore, large-particle graphite has higher electrical conductivity, which can improve the discharge efficiency of the battery. Of course, the first active material layer 150 and the second active material layer 170 can also be prepared using other main and auxiliary materials, as long as the first active material layer 150 has good kinetics and the second active material layer 170 has high specific energy.

[0067] The sum of the thickness of the first active material layer 150 and the thickness of the second active material layer 170 is equal at any position of the current collector 110. That is, the outer plane formed is flat, so that the distance between the positive electrode sheet and the negative electrode sheet 100 can be equal.

[0068] Referring to Figure 2 , in this embodiment, the ratio of the thickness of the first active material layer 150 to the thickness of the second active material layer 170 is X. The value of X varies along the extension direction of the tab 130. The value range of X is 0 < X ​​≤ 10. The ratio of the thickness of the first active material layer 150 to the thickness of the second active material layer 170 gradually increases from one side of the tab 130 toward the side away from the tab 130 and then gradually decreases, which can better improve the problem of lithium deposition.

[0069] For example, the value of X can vary between 0.5 and 2, first gradually increasing from 0.5 to 2, and then gradually decreasing from 2 to 0.5. The value range of X can also be 1-2, 2-3, 4-6, 1-10, 1-5, 2-8, 1-6, 2-7, 3-9, etc., or 0.5-1, 0.1-1, etc. The specific range can be determined based on parameters such as battery size.

[0070] It can be seen from FIG. 2 that the bonding surface between the first active material layer 150 and the second active material layer 170 is substantially a parabola opening downward.

[0071] In this embodiment, the first active material layer 150 and the second active material layer 170 have different areal densities.

[0072] It should be noted that the areal density ratio of the first active material layer 150 and the second active material layer 170 can be adjusted based on the performance requirements of the battery cell. If the battery 300 has high requirements for fast charging performance, the areal density ratio of the second active material layer 170 can be increased. If the battery has high requirements for energy density, the areal density ratio of the first active material layer 150 can be increased.

[0073] In this embodiment, the first active material layer 150 and the second active material layer 170 have an asymmetric structure. That is, the thickest point of the first active material layer 150 is not located at the center of the corresponding tab 130 of the negative electrode sheet 100. The specific symmetric location of the thickest point of the first active material layer 150 is determined based on the material and properties of the current collector 110, as well as the conductive properties and variations of the current collector 110.

[0074] In this embodiment, the current collector 110 and the tab 130 are integrally formed. For example, the tab 130 and the current collector 110 are die-cut together using a die-cutting process. The negative electrode sheet 100 is symmetrically arranged with respect to the current collector 110 in the thickness direction of the negative electrode sheet 100. The current collector 110 is made of one of a metal foil, a composite foil, and a coated foil, for example, copper foil.

[0075] Referencing Figure 2 and the table below, experiments show that different thickness ratios were set for the negative electrode sheet 100 at three points, L, P, and Q, extending from one side of the tab 130 toward the side away from the tab 130. As shown in the chart, Group A's ratios initially increase and then decrease from the tab side toward the other side; Group B's ratios are consistent across the upper and lower layers; and Group C's ratios are the opposite of Group A's, decreasing and then increasing from the tab 130 side toward the other side. After 1000 cycles, Group A exhibited no lithium deposition, Group B exhibited slight lithium deposition, and Group C exhibited significant lithium deposition.

[0076] Table 1: Lithium deposition test table of different thickness ratios at L, P, and Q in the three comparative test groups A, B, and C

[0077] It can be seen from the above table that the negative electrode sheet 100 provided in this embodiment can improve the problem of lithium plating in batteries.

[0078] This embodiment also provides an electrical device, comprising an electrical device body and a battery 300, as described in the above embodiment, disposed within the electrical device body. Battery 300 is used to power the electrical device body, thereby operating the electrical device body. The electrical device may be an energy storage cabinet, an electric vehicle, or a power tool.

[0079] In summary, the embodiments of the present disclosure provide a negative electrode sheet 100, a battery 300, a battery pack, and an electrical device, and the working principles and beneficial effects thereof include:

[0080] In this embodiment, the first active material layer 150 is applied to the front and back of the current collector 110, and the thickness of the first active material layer gradually increases from the side of the tab 130 to the side away from the tab 130, and then gradually decreases. The second active material layer 170 is applied to the outside of the first active material layer 150, and the thickness of the second active material layer 170 gradually decreases from the side of the tab 130 to the side away from the tab 130, and then gradually increases. This can improve the ion diffusion rate in the high potential area between the positive and negative electrode sheets 100, reduce ion transfer resistance, and reduce the risk of lithium plating.

[0081] The above are only specific embodiments of the present disclosure, but the scope of protection of the present disclosure is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this disclosure should be included in the scope of protection of the present disclosure. Therefore, the scope of protection of the present disclosure should be based on the scope of protection of the claims. Industrial Applicability

[0082] The present disclosure provides a negative electrode sheet, a battery, a battery pack and an electric device, which improve the problem of lithium plating and enhance the safety of the battery by providing an active material layer coated on the surface of the current collector of the negative electrode sheet.

Claims

1. A negative electrode sheet, characterized in that: include: Current collector(110); A pole ear (130) connected to one side of the current collector (110); A first active material layer (150), the first active material layer (150) being coated on the front and back sides of the current collector (110), and the thickness of the first active material layer (150) gradually increases from one side of the electrode tab (130) to the side away from the electrode tab (130), and then gradually decreases; as well as, A second active material layer (170), the second active material layer (170) is coated on the outer side of the first active material layer (150), and the thickness of the second active material layer (170) gradually becomes thinner from one side of the electrode ear (130) to the side away from the electrode ear (130), and then gradually becomes thicker.

2. The negative electrode sheet according to claim 1, characterized in that: The first active material layer (150) is a high specific energy active material layer, and the kinetic performance of the second active material layer (170) is greater than the kinetic performance of the first active material layer (150).

3. The negative electrode sheet according to claim 1 or 2, characterized in that: The sum of the thickness of the first active material layer (150) and the thickness of the second active material layer (170) at any position of the current collector (110) is equal.

4. The negative electrode sheet according to any one of claims 1 to 3, characterized in that: The ratio of the thickness of the first active material layer (150) to the thickness of the second active material layer (170) is X, and the value range of X is 0<X≤10.

5. The negative electrode sheet according to any one of claims 1 to 4, characterized in that: The ratio of the thickness of the first active material layer (150) to the thickness of the second active material layer (170) gradually increases from one side of the electrode tab (130) toward a side away from the electrode tab (130), and then gradually decreases.

6. The negative electrode sheet according to any one of claims 1 to 5, characterized in that: The first active material layer (150) and the second active material layer (170) have different surface densities.

7. The negative electrode sheet according to any one of claims 1 to 6, characterized in that: The first active material layer (150) and the second active material layer (170) are asymmetric structures in the extension direction of the electrode tab (130).

8. The negative electrode sheet according to any one of claims 1 to 7, characterized in that: The particle size distribution of the first active material layer (150) is greater than the particle size distribution of the second active material layer (170).

9. The negative electrode sheet according to any one of claims 1 to 8, characterized in that: The main material of the first active material layer (150) is small-particle blended graphite; The main material of the second active material layer (170) is a mixture of large and small particles of graphite.

10. The negative electrode sheet according to any one of claims 1 to 9, characterized in that: The current collector (110) and the electrode tab (130) are integrally formed.

11. The negative electrode sheet according to any one of claims 1 to 10, characterized in that: The negative electrode sheet (100) is symmetrically arranged with respect to the current collector (110) in the thickness direction of the negative electrode sheet (100).

12. The negative electrode sheet according to any one of claims 1 to 11, characterized in that: The current collector (110) is made of one of a metal foil, a composite foil and a coated foil.

13. A battery, comprising a housing (310), a bare cell and a pole (330), characterized in that: The bare battery cell comprises a positive electrode sheet, a separator and a negative electrode sheet as described in any one of claims 1 to 10; The positive electrode sheet, the separator, the negative electrode sheet and the separator are stacked in sequence; The bare battery cell is installed in the housing (310), and the pole lug (130) is electrically connected to the pole (330).

14. A battery pack, characterized in that: The invention comprises a plurality of batteries according to claim 13, wherein the plurality of batteries are connected in parallel or in series.

15. An electrical equipment, characterized in that: It comprises an electric device body and the battery as claimed in claim 13, wherein the battery is arranged on the electric device body to supply power to the electric device body.

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