Negative plate, battery cell, battery and electric equipment

Abstract

The utility model belongs to the technical field of batteries, and particularly relates to a negative pole piece, a battery cell, a battery and electric equipment, the negative pole piece is provided with a starting end and a tail end which are oppositely arranged along the length direction of the negative pole piece, the negative pole piece is wound along the length direction, the starting end is positioned on the inner ring of the negative pole piece, and the tail end is positioned on the outer ring of the negative pole piece. The starting end is located on the outer ring of the negative plate, the tail end is located on the outer ring of the negative plate, the negative plate comprises a current collector and an active substance layer, the current collector is provided with a first coating area and a second coating area, the first coating area is close to the starting end, the second coating area is close to the tail end, the active substance layer comprises a graphite material layer and a silicon-based material layer, and the graphite material layer and the silicon-based material layer are arranged on the negative plate. The first coating area is coated with the graphite material layer, the second coating area is coated with the silicon-based material layer, and the length L2 of the graphite material layer is smaller than the length L1 of the silicon-based material layer; lithium separation of the inner ring of the negative plate caused by material falling of the inner ring of the negative plate is effectively avoided, so that the performance of the battery is improved.

Description

Technical Field

[0001] The utility model belongs to the technical field of batteries, and specifically relates to a negative electrode sheet, a battery core, a battery and electrical equipment. Background Art

[0002] As a new type of secondary battery, lithium-ion battery has the advantages of high energy density and power density, high operating voltage, light weight, small size, long cycle life, good safety, and green environmental protection. It has broad application prospects in portable appliances, power tools, large-scale energy storage, electric transportation power supply, etc.

[0003] At present, silicon-based materials are added to the negative electrode materials of battery cells. During the charge and discharge process of the battery cells, the rebound expansion force of the silicon-based materials is more significant than that of the traditional graphite negative electrode, which makes it difficult to effectively release the stress of the inner ring electrode sheet of the battery cell. As a result, when the battery cell is disassembled, it is often observed that the inner ring negative electrode sheet is seriously falling off. This material falling problem directly affects the embedding process of lithium ions in the inner ring, resulting in a significant decrease in the capacity of the battery cell. At the same time, the collapse of the central hole of the battery cell will also hinder the flow channel of the electrolyte, thereby affecting the movement of the electrolyte and causing an increase in impedance. Especially in the later stages of long-cycle charge and discharge of the battery cell, these two effects may trigger the so-called "cycle diving" phenomenon, that is, the battery cell performance drops significantly in the later stages of the cycle, which greatly affects the normal performance of the battery cell. Utility Model Content

[0004] The purpose of the utility model is to provide a negative electrode sheet, a battery cell, a battery and an electrical device to address the deficiencies in the prior art, thereby solving the technical problem in the prior art that the inner ring of the battery cell is lost, which affects the embedding process of lithium ions in the inner ring, resulting in a significant decrease in the capacity of the battery cell, thereby reducing the performance of the battery.

[0005] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0006] In the first aspect, the utility model provides a negative electrode sheet, along the length direction of the negative electrode sheet, the negative electrode sheet has a starting end and an ending end relatively arranged, the negative electrode sheet is wound along the length direction, the starting end is located at the inner circle of the negative electrode sheet, and the ending end is located at the outer circle of the negative electrode sheet, the negative electrode sheet includes a current collector and an active material layer, the current collector has a first coating area and a second coating area, the first coating area is close to the starting end, and the second coating area is close to the ending end, the active material layer includes a graphite material layer and a silicon-based material layer, the graphite material layer is coated on the first coating area, the silicon-based material layer is coated on the second coating area, and the length L2 of the graphite material layer is less than the length L1 of the silicon-based material layer.

[0007] Preferably, the length L2 of the graphite material layer and the length L1 of the silicon-based material layer satisfy the relationship: L1+L2≤L3, wherein L3 is the length of the current collector.

[0008] Preferably, the length L2 of the graphite material layer and the length L1 of the silicon-based material layer satisfy the relationship: L1:L2=(4-5):1.

[0009] Preferably, the peeling force between the silicon-based material layer and the current collector is smaller than the peeling force between the graphite material layer and the current collector.

[0010] Preferably, the coating thickness T1 of the silicon-based material layer is smaller than the coating thickness T2 of the graphite material layer.

[0011] In a second aspect, the utility model provides a battery cell, comprising a first pole sheet, a second pole sheet and a diaphragm, wherein the first pole sheet, the diaphragm and the second pole sheet are stacked and wound in sequence to form the battery cell, wherein the first pole sheet or the second pole sheet is the negative pole sheet of the above-mentioned embodiment.

[0012] Preferably, the CB value of the negative electrode sheet of the battery cell in the corresponding second coating area is smaller than the CB value of the negative electrode sheet of the battery cell in the corresponding first coating area. It can be understood that the CB value of the battery cell in the outer circle of the negative electrode sheet is smaller than the CB value of the battery cell in the inner circle of the negative electrode sheet.

[0013] Preferably, the CB value of the negative electrode sheet of the battery cell corresponding to the second coating area is 1.05-1.15, and the CB value of the negative electrode sheet of the battery cell corresponding to the first coating area is 1.2-1.25. It can be understood that the CB value of the battery cell in the outer circle of the negative electrode sheet is 1.05-1.15, and the CB value of the battery cell in the inner circle of the negative electrode sheet is 1.2-1.25.

[0014] In a third aspect, the utility model provides a battery, comprising a housing and the battery cell of the above embodiment, wherein the battery cell is arranged in the housing.

[0015] In a fourth aspect, the utility model provides an electrical device, comprising the battery of the above embodiment.

[0016] Compared with the prior art, the beneficial effects achieved by the utility model are:

[0017] The negative electrode sheet of the utility model is provided with a first coating area and a second coating area on the current collector, wherein the first coating area is close to the starting end of the negative electrode sheet, and the second coating area is close to the tail end of the negative electrode sheet, and a graphite material layer is coated on the first coating area, and a silicon-based material layer is coated on the second coating area, that is, the graphite material layer is coated on the inner circle area of ​​the current collector close to the negative electrode sheet, and the silicon-based material layer is coated on the outer circle area of ​​the current collector close to the negative electrode sheet. Since the deformation expansion force of the graphite material layer is less than the deformation expansion force of the silicon-based material layer, the inner circle of the negative electrode sheet is effectively prevented from dropping and causing lithium deposition in the inner circle of the negative electrode sheet, and the collapse of the central hole area can also be avoided. Thus, the performance of the battery is effectively improved and the life of the battery is extended. By making the length L2 of the graphite material layer less than the length L1 of the silicon-based material layer, the area occupied by the silicon-based material layer in the current collector can be effectively increased, thereby increasing the usage of the silicon-based material layer and improving the energy density of the battery.

[0018] Additional aspects and advantages of the present invention will be given in part in the following description, and in part will become apparent from the following description, or will be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0020] Figure 1 It is a schematic diagram of the structure of the negative electrode sheet of the utility model.

[0021] Figure 2 It is a schematic diagram of the structure of the single-sided coating of the negative electrode sheet of the utility model.

[0022] Figure 3 It is a schematic diagram of the structure of the double-sided coating of the negative electrode sheet of the utility model.

[0023] Figure 4 The utility model is a schematic diagram of the structure of the winding negative electrode sheet.

[0024] The reference numerals are described as follows:

[0025] 100, negative electrode; 101, starting end; 102, ending end;

[0026] 10. current collector; 11. first coating area; 12. second coating area;

[0027] 20. active material layer; 21. graphite material layer; 22. silicon-based material layer;

[0028] a. The length direction of the negative electrode sheet. DETAILED DESCRIPTION

[0029] For example, certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that hardware manufacturers may use different terms to refer to the same component. This specification and claims do not use differences in names as a way to distinguish components, but use differences in the functions of components as the criteria for distinction. For example, "including" mentioned throughout the specification and claims is an open term, so it should be interpreted as "including but not limited to". "Approximately" means that within an acceptable error range, those skilled in the art can solve technical problems within a certain error range and basically achieve technical effects.

[0030] Furthermore, the terms “first”, “second”, etc. are used for descriptive purposes only and are not to be understood as indicating or implying relative importance.

[0031] In the utility model, unless otherwise clearly specified and limited, the terms "install", "connect", "connect", "fix" and the like 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 an indirect connection 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 utility model can be understood according to the specific circumstances.

[0032] The following will be combined with the attached Figures 1 to 4 The technical solutions in the embodiments of the utility model are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of them. 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.

[0033] The electrical equipment of the embodiment of the utility model includes a battery. The electrical device may be a car, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy, an electric tool, and the like. The car may be a fuel car, a gas car, or a new energy car, and the new energy car may be a pure electric car, a hybrid car, or an extended-range car, and the like; the spacecraft includes an airplane, a rocket, a space shuttle, and a spacecraft, and the like; the electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, and the like; the electric tools include metal cutting electric tools, grinding electric tools, assembly electric tools, and railway electric tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, and the like. The embodiment of the present application does not impose any special restrictions on the above-mentioned electrical devices.

[0034] The battery of the embodiment of the utility model comprises a shell and a battery cell, wherein the battery cell is arranged in the shell.

[0035] The battery cell of the embodiment of the utility model comprises a first pole piece, a second pole piece and a diaphragm, wherein the first pole piece, the diaphragm and the second pole piece are stacked and wound in sequence to form the battery cell.

[0036] Furthermore, the polarities of the first pole piece and the second pole piece are opposite, one of the first pole piece and the second pole piece is a positive pole piece, and the other of the first pole piece and the second pole piece is a negative pole piece 100 .

[0037] The inventors have found that in order to increase the energy density of the battery, silicon-based materials are usually selected as the active material of the negative electrode sheet 100. However, during the charge and discharge process of the battery, the deformation expansion force of the silicon-based material is greater than the deformation expansion force of the graphite material. In particular, in wound cells, the inner ring of the cell is subjected to a large tightening force due to the winding structure. In contrast, the stress of the outer ring of the cell is relatively small. This uneven stress distribution makes it difficult to fully release the stress of the inner ring electrode sheet. Therefore, during the disassembly of the battery cell, we often find that the negative electrode sheet 100 has serious material shedding in the area close to the inner ring.

[0038] Furthermore, since the inner ring pole piece bears the main force, the outer ring pole piece can only expand along the direction of the center hole under the constraint of the outer layer pole piece. This deformation makes the center hole area very easy to collapse, which may reduce the performance of the battery and shorten the battery life.

[0039] For this reason, see Figures 1 to 4, the negative electrode sheet 100 of the utility model embodiment, along the length direction a of the negative electrode sheet 100, the negative electrode sheet 100 has a starting end 101 and an end end 102 arranged opposite to each other, the negative electrode sheet 100 is wound along the length direction, the starting end 101 is located at the inner circle of the negative electrode sheet 100, and the end end 102 is located at the outer circle of the negative electrode sheet 100, the negative electrode sheet 100 includes a current collector 10 and an active material layer 20, the current collector 10 has a first coating area 11 and a second coating area 12, the first coating area 11 is close to the starting end 101, and the second coating area 12 is close to the end end 102, the active material layer 20 includes a graphite material layer 21 and a silicon-based material layer 22, the graphite material layer 21 is coated on the first coating area 11, and the silicon-based material layer 22 is coated on the second coating area 12.

[0040] Compared with the prior art, the negative electrode sheet 100 of the embodiment of the utility model is provided with a first coating area 11 and a second coating area 12 on the current collector 10, wherein the first coating area 11 is close to the starting end 101 of the negative electrode sheet 100, and the second coating area 12 is close to the tail end 102 of the negative electrode sheet 100, and the graphite material layer 21 is coated on the first coating area 11, and the silicon-based material layer 22 is coated on the second coating area 12, that is, the graphite material layer 21 is coated on the inner circle area of ​​the current collector 10 close to the negative electrode sheet 100, and the silicon-based material layer 22 is coated on the outer circle area of ​​the current collector 10 close to the negative electrode sheet 100. Since the deformation expansion force of the graphite material layer 21 is less than the deformation expansion force of the silicon-based material layer 22, the inner circle of the negative electrode sheet 100 is effectively prevented from dropping and causing lithium deposition in the inner circle of the negative electrode sheet 100, and the collapse of the central hole area can also be avoided. This effectively improves the performance of the battery and prolongs the life of the battery.

[0041] See also Figure 1 In some embodiments, the length L2 of the graphite material layer 21 is less than the length L1 of the silicon-based material layer 22. Because at the same volume or mass, the energy density of the silicon-based material layer 22 is greater than the energy density of the graphite material layer 21. If the length L2 of the graphite material layer 21 is too long, it will inevitably occupy more area of ​​the current collector 10, which reduces the area of ​​the current collector 10 that the silicon-based material layer 22 can occupy, which will result in the space inside the battery cell for accommodating the higher energy density silicon-based material layer 22 being limited. This not only reduces the energy density of the battery, but may also affect the output power and cycle life of the battery. Therefore, making the length L2 of the graphite material layer 21 less than the length L1 of the silicon-based material layer 22 can effectively increase the area of ​​the current collector 10 occupied by the silicon-based material layer 22, thereby increasing the usage of the silicon-based material layer 22 and improving the energy density of the battery.

[0042] Furthermore, the length L2 of the graphite material layer 21 and the length L1 of the silicon-based material layer 22 satisfy the relationship: L1:L2=(4-5):1. If the length L2 of the graphite material layer 21 is too long, it will not only reduce the energy density of the battery, but also may affect the output power and cycle life of the battery; if the length L2 of the graphite material layer 21 is too short, the effect of avoiding the inner circle of the negative electrode sheet from falling off is limited. Therefore, when L1:L2=(4-5):1, it can not only effectively improve the performance of the battery, extend the life of the battery, and increase the energy density of the battery, but also solve the problem of the inner circle of the negative electrode sheet from falling off.

[0043] Specifically, the length L2 of the graphite material layer 21 and the length L1 of the silicon-based material layer 22 satisfy the relationship: L1:L2=4:1, L1:L2=4.05:1, L1:L2=4.1:1, L1:L2=4.15:1, L1:L2=4.2:1, L1:L2=4.25:1, L1:L2=4.3:1, L1:L2=4.5:1, L1:L2=4.55:1, L1:L2=4.7:1, L1:L2=4.85:1, L1:L2=4.9:1 or L1:L2=5:1. However, the present invention is not limited to the values ​​listed above, and other values ​​within the numerical range are also applicable.

[0044] In some embodiments, the length L2 of the graphite material layer 21 and the length L1 of the silicon-based material layer 22 satisfy the relationship: L1+L2≤L3, where L3 is the length of the current collector 10. Since the graphite material layer 21 and the silicon-based material layer 22 are both coated on the current collector 10, if the sum of the length L2 of the graphite material layer 21 and the length L1 of the silicon-based material layer 22 is greater than the length L3 of the current collector 10, that is, L1+L2>L3, when the graphite material layer 21 and the silicon-based material layer 22 are coated on the current collector 10, material shedding may occur. Therefore, the sum of the length L2 of the graphite material layer 21 and the length L1 of the silicon-based material layer 22 needs to be less than or equal to the length L3 of the current collector 10, that is, L1+L2≤L3, which can effectively avoid material shedding during the coating process of the graphite material layer 21 and the silicon-based material layer 22.

[0045] Specifically, when the sum of the length L2 of the graphite material layer 21 and the length L1 of the silicon-based material layer 22 is less than the length L3 of the current collector 10, that is, L1+L2<L3, after the graphite material layer 21 and the silicon-based material layer 22 are coated on the current collector 10, there is an empty foil area in the current collector 10, and the empty foil area can be used as a pole ear for electrical connection with other components inside the battery.

[0046] When the sum of the length L2 of the graphite material layer 21 and the length L1 of the silicon-based material layer 22 is equal to the length L3 of the current collector 10, that is, L1+L2=L3, after the graphite material layer 21 and the silicon-based material layer 22 are coated on the current collector 10, the graphite material layer 21 and the silicon-based material layer 22 jointly cover the current collector 10.

[0047] In some embodiments, the peeling force between the silicon-based material layer 22 and the current collector 10 is less than the peeling force between the graphite material layer 21 and the current collector 10. If the peeling force between the graphite material layer 21 and the current collector 10 is too small, the viscosity of the graphite material layer 21 and the current collector 10 is low, so that the bonding strength between the graphite material layer 21 and the current collector 10 is low. During the battery charging and discharging process, the graphite material layer 21 is prone to material shedding, resulting in lithium deposition in the inner circle of the negative electrode sheet 100, which may reduce the performance of the battery and reduce the life of the battery. Therefore, the peeling force between the silicon-based material layer 22 and the current collector 10 is smaller than the peeling force between the graphite material layer 21 and the current collector 10, which effectively increases the viscosity of the graphite material layer 21 and the current collector 10, and improves the bonding strength between the graphite material layer 21 and the current collector 10, thereby effectively avoiding the graphite material layer 21 from easily shedding material and causing lithium deposition in the inner circle of the negative electrode sheet 10, thereby effectively improving the performance of the battery and extending the life of the battery.

[0048] Furthermore, both the silicon-based material layer 22 and the graphite material layer 21 include a binder, and the binder is PAA and SBR. Since PAA is a strong binder, by increasing the proportion of PAA in the binder, the peeling force between the silicon-based material layer 22 and the current collector 10 and the peeling force between the graphite material layer 21 and the current collector 10 can be effectively increased. In addition, compared with the CMC binder of the prior art, PAA has a better restraint force on the expansion force of the negative electrode active material layer 20, which can effectively improve the situation where the negative electrode sheet 100 falls off during the charging and discharging process of the battery.

[0049] Specifically, PAA:SBR=(0.56-0.7):(0.3-0.44). Preferably, PAA:SBR=0.6:0.4.

[0050] Further, the silicon-based material layer 22 also includes a silicon-based material, a graphite material and a conductive agent, wherein the silicon-based material is silicon oxide (SiOx), pre-lithium silicon oxide (LiSiOx) or silicon carbon material (SiCx), the graphite material is artificial graphite, and the conductive agent is conductive carbon black, conductive graphite, carbon fiber or carbon nanotube. The graphite material layer 21 also includes a graphite material and a conductive agent, wherein the graphite material is artificial graphite, and the conductive agent is conductive carbon black, conductive graphite, carbon fiber or carbon nanotube.

[0051] See also Figures 2-3In some embodiments, the coating thickness T1 of the silicon-based material layer 22 is less than the coating thickness T2 of the graphite material layer 21. By setting the coating thickness T1 of the silicon-based material layer 22 and the coating thickness T2 of the graphite material layer 21, since the deformation expansion force of the silicon-based material is greater than the deformation expansion force of the graphite material during the charging and discharging process of the battery, the thickness T1 of the silicon-based material layer 22 is less than the thickness T2 of the graphite material layer 21, which can effectively ensure the flatness of the surface of the negative electrode active material layer 20 after the silicon-based material layer 22 and the graphite material layer 21 are deformed and expanded.

[0052] Furthermore, the coating thickness T1 of the silicon-based material layer 22 and the coating thickness T2 of the graphite material layer 21 satisfy the relationship: 0.075mm≤2T1<0.83mm, 0.83mm≤2T2≤0.93mm. Among them, 2T1 is the thickness of the silicon-based material layer 22 coated on both sides of the negative electrode sheet 100, and 2T2 is the thickness of the market material layer coated on both sides of the negative electrode sheet 100. By setting 0.075mm≤2T1<0.83mm and 0.830mm≤2T2≤093mm, it can not only effectively avoid the inner circle of the negative electrode sheet 100 from falling off and causing lithium deposition in the inner circle of the negative electrode sheet 100, but also effectively ensure the flatness of the surface of the negative electrode active material layer 20 after the silicon-based material layer 22 and the graphite material layer 21 are deformed and expanded.

[0053] Specifically, the thickness 2T1 of the silicon-based material layer 22 coated on both sides of the negative electrode sheet 100 is 0.075 mm, 0.089 mm, 0.1 mm, 0.155 mm, 0.2 mm, 0.236 mm, 0.3 mm, 0.385 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.659 mm, 0.7 mm, 0.8 mm, 0.81 mm or 0.829 mm. The thickness 2T2 of the graphite material layer 21 coated on both sides of the negative electrode sheet 100 is 0.83 mm, 0.84 mm, 0.85 mm, 0.86 mm, 0.87 mm, 0.88 mm, 0.89 mm, 0.9 mm, 0.91 mm, 0.92 mm or 0.93 mm. However, it is not limited to the listed values, and other values ​​within the numerical range are also applicable.

[0054] It can be understood that the CB value is the margin of the negative electrode capacity exceeding the positive electrode capacity in the same stage and under the same conditions. It can be calculated by the ratio of the negative electrode capacity per unit area to the positive electrode capacity per unit area, that is, CB = negative electrode capacity per unit area / positive electrode capacity per unit area.

[0055] When the CB value is too low, the negative electrode capacity may not be sufficient to receive all the lithium ions released by the positive electrode, resulting in lithium ions being deposited and precipitated at the anode to form lithium dendrites, i.e., lithium deposition occurs in the negative electrode sheet 100. This may then pierce the diaphragm, causing safety issues such as battery short circuit and fire.

[0056] When the CB value is too high, since the negative electrode capacity is much larger than the positive electrode capacity, part of the negative electrode active material will not be fully utilized during the charge and discharge process of the battery, resulting in a decrease in the energy density of the battery and affecting the service life of the battery.

[0057] Therefore, in some embodiments, the CB value of the negative electrode sheet 100 of the battery cell corresponding to the second coating area 12 is less than the CB value of the negative electrode sheet 100 of the battery cell corresponding to the first coating area 11, which can be understood as the CB value of the battery cell in the outer circle of the negative electrode sheet 100 is less than the CB value of the battery cell in the inner circle of the negative electrode sheet 100. When the surface density of the positive active material layer 20 remains unchanged, by increasing the CB value of the battery cell in the inner circle of the negative electrode sheet 100, the surface density of the graphite material layer 21 can be effectively increased, so that the graphite material layer 21 can provide more lithium insertion sites, thereby improving the inner circle of the negative electrode sheet 100. The inner circle of the negative electrode sheet 100 is lithium precipitated due to the material shedding.

[0058] Further, the CB value of the negative electrode sheet 100 of the battery cell corresponding to the second coating area 12 is 1.05-1.15, and the CB value of the negative electrode sheet 100 of the battery cell corresponding to the first coating area 11 is 1.2-1.25. It can be understood that the CB value of the battery cell cannot be too high or too low. By setting the CB value of the battery cell in the outer circle of the negative electrode sheet 100 to 1.05-1.15 and the CB value of the battery cell in the inner circle of the negative electrode sheet 100 to 1.2-1.25, it can not only effectively increase the surface density of the graphite material layer 21, improve the inner circle of the negative electrode sheet 100 from dropping the material to cause lithium deposition in the inner circle of the negative electrode sheet 100, but also improve the battery energy density and extend the battery life.

[0059] Specifically, the CB value of the negative electrode sheet 100 of the battery cell corresponding to the second coating area 12 is 1.05, 1.06, 1.07, 1.08, 1.09, 1.1, 1.11, 1.12, 1.13, 1.14 or 1.15. The CB value of the negative electrode sheet 100 of the battery cell corresponding to the first coating area 11 is 1.2, 1.21, 1.215, 1.22, 1.225, 1.23, 1.235, 1.24, 1.245 or 1.25. However, it is not limited to the listed values, and other values ​​within the numerical range are also applicable.

[0060] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention.

Claims

1. A negative electrode sheet, characterized in that: Along the length direction (a) of the negative electrode sheet (100), the negative electrode sheet (100) has a starting end (101) and an ending end (102) arranged opposite to each other. The negative electrode sheet (100) is wound along its length direction (a), the starting end (101) is located at the inner circle of the negative electrode sheet (100), and the ending end (102) is located at the outer circle of the negative electrode sheet (100). The negative electrode sheet (100) comprises a current collector (10) and an active material layer (20). The current collector (10) has a first coating area (11) and an active material layer (20). The second coating area (12), the first coating area (11) is close to the starting end (101), the second coating area (12) is close to the tail end (102), the active material layer (20) comprises a graphite material layer (21) and a silicon-based material layer (22), the graphite material layer (21) is coated on the first coating area (11), the silicon-based material layer (22) is coated on the second coating area (12), and the length L2 of the graphite material layer (21) is less than the length L1 of the silicon-based material layer (22).

2. The negative electrode sheet according to claim 1, characterized in that: The length L2 of the graphite material layer (21) and the length L1 of the silicon-based material layer (22) satisfy the relationship: L1+L2≤L3, wherein L3 is the length of the current collector (10).

3. The negative electrode sheet according to claim 1, characterized in that: The length L2 of the graphite material layer (21) and the length L1 of the silicon-based material layer (22) satisfy the relationship: L1:L2=(4-5):

1.

4. The negative electrode sheet according to claim 1, characterized in that: The peeling force between the silicon-based material layer (22) and the current collector (10) is smaller than the peeling force between the graphite material layer (21) and the current collector (10).

5. The negative electrode sheet according to claim 1, characterized in that: The coating thickness T1 of the silicon-based material layer (22) is smaller than the coating thickness T2 of the graphite material layer (21).

6. A battery cell, characterized in that: The battery cell comprises a first pole sheet, a second pole sheet and a separator, wherein the first pole sheet, the separator and the second pole sheet are sequentially stacked and wound to form the battery cell, wherein the first pole sheet or the second pole sheet is the negative pole sheet according to any one of claims 1 to 5.

7. The battery cell according to claim 6, characterized in that: The CB value of the negative electrode sheet (100) of the battery cell corresponding to the second coating area (12) is smaller than the CB value of the negative electrode sheet (100) of the battery cell corresponding to the first coating area (11).

8. The battery cell according to claim 6, characterized in that: The CB value of the negative electrode sheet (100) of the battery cell corresponding to the second coating area (12) is 1.05 to 1.15, and the CB value of the negative electrode sheet (100) of the battery cell corresponding to the first coating area (11) is 1.2 to 1.

25.

9. A battery, characterized in that: The invention comprises a shell and the battery core according to any one of claims 6 to 8, wherein the battery core is arranged in the shell.

10. An electrical equipment, characterized in that: A battery comprising the battery of claim 9.

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