A negative electrode sheet, an electrode assembly, and a battery

Abstract

The application provides a negative electrode sheet, an electrode assembly and a battery. The negative electrode sheet comprises a negative electrode current collector, the negative electrode current collector has a first functional surface and a second functional surface arranged oppositely; the first functional surface has a tab area and an active layer area connected to each other, the tab area is arranged with a tab, and the active layer area is arranged with a first negative electrode active layer, the first negative electrode active layer has a bright area and a dark area away from the surface of the negative electrode current collector; the second functional surface is arranged with a second negative electrode active layer, the second negative electrode active layer comprises a first area and a second area connected to each other away from the surface of the negative electrode current collector, the first area has a bright area and a dark area, and the second area is a dark area; and the second area at least partially overlaps with the tab area in the first orthographic projection of the first functional surface. The negative electrode sheet is not easy to generate lithium in the charging and discharging process of the battery, and is helpful to improve the cycle performance of the battery.

Description

Technical Field

[0001] This invention relates to the field of new energy technology, and in particular to a negative electrode sheet, an electrode assembly, and a battery. Background Technology

[0002] The theoretical specific capacity of silicon-based anode materials is more than ten times that of graphite-based anode materials, hence their widespread use in the fabrication of lithium-ion battery anode sheets. However, silicon-based anode materials suffer from low initial efficiency. Current technologies typically incorporate a lithium replenishment layer on the surface of the silicon-based anode sheet to improve its initial efficiency. However, this lithium replenishment layer makes the anode sheet prone to lithium plating, which in turn affects the battery's cycle performance. Summary of the Invention

[0003] This invention provides a negative electrode that is less prone to lithium plating during the charging and discharging process of a battery, which helps to improve the cycle performance of the battery.

[0004] The present invention provides an electrode assembly including the aforementioned negative electrode sheet, which helps to improve the cycle performance of the battery.

[0005] The present invention provides a battery comprising the electrode assembly described above, and therefore exhibits excellent cycle performance.

[0006] The present invention provides a negative electrode sheet, wherein the negative electrode current collector has a first functional surface and a second functional surface disposed opposite to each other;

[0007] The first functional surface has an interconnected tab region and an active layer region. The tab region is provided with tabs, and the active layer region is provided with a first negative electrode active layer. The surface of the first negative electrode active layer away from the negative electrode current collector has a bright area and a dark area.

[0008] The second functional surface is provided with a second negative electrode active layer. The surface of the second negative electrode active layer away from the negative electrode current collector includes a first region and a second region that are connected to each other. The first region has a bright area and a dark area, and the second region is a dark area.

[0009] The first orthographic projection of the second region onto the first functional surface at least partially overlaps with the tab region.

[0010] In the negative electrode sheet as described above, the length L2 of the second region and the length L1 of the tab satisfy: L2 = (1.1~4.0) * L1.

[0011] In the negative electrode sheet as described above, the width W2 of the second region and the width W0 of the negative electrode current collector satisfy: W2 = (0.05~0.7)*W0.

[0012] As described above, the negative electrode sheet has a first center line extending along the first direction in the first positive projection, and the tab region has a second center line extending along the first direction.

[0013] Along the second direction, the minimum distance between the first centerline and the second centerline is ≤0.5mm, and the first direction and the second direction are perpendicular to each other; and / or,

[0014] The first orthographic projection has a third center line extending along the second direction, and the tab region has a fourth center line extending along the second direction;

[0015] Along the first length direction, the minimum distance between the third center line and the fourth center line is ≤0.5mm, and the first direction is perpendicular to the second direction.

[0016] The negative electrode sheet described above, wherein the thickness H2 of the negative electrode sheet in the second region, the thickness H1 of the negative electrode sheet in the first region, and the thickness H0 of the negative electrode current collector satisfy:

[0017] (H2-H0)=(0.55~1.0)*(H1-H0).

[0018] The present invention provides an electrode assembly, wherein the negative electrode sheet is as described above.

[0019] The electrode assembly described above further includes a positive electrode disposed opposite to the negative electrode, the positive electrode comprising a positive electrode body and an insulating layer disposed on at least one functional surface of the positive electrode body;

[0020] The second orthographic projection of the insulating layer onto the second functional surface at least partially overlaps with the second region.

[0021] In the electrode assembly described above, the edge of the second region lies within the edge of the second orthographic projection, or the edge of the second region at least partially coincides with the edge of the second orthographic projection.

[0022] In the electrode assembly described above, the tab region is formed by a recess in the first negative electrode active layer toward the negative electrode current collector, and the tab is disposed in the recess.

[0023] The present invention provides a battery comprising the electrode assembly described above.

[0024] The negative electrode of the present invention has a second region opposite to the tab region. The second region can reduce the risk of lithium plating in the tab region of the negative electrode during battery charging and discharging, thereby improving the cycle performance of the battery.

[0025] The electrode assembly of the present invention includes the aforementioned negative electrode sheet, so lithium plating is less likely to occur in the tab region of the negative electrode sheet during the charging and discharging process of the battery, which helps to improve the cycle performance of the battery.

[0026] The battery of the present invention, because it includes the electrode assembly described above, does not easily have lithium deposition in the tab region of the negative electrode during charging and discharging, and has excellent cycle performance. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the accompanying drawings used in the description of the embodiments of the present invention or related technologies are briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a side view of the negative electrode sheet in some embodiments of the present invention;

[0029] Figure 2 This is a top view of the negative electrode sheet in some embodiments of the present invention;

[0030] Figure 3 This is a side view of an electrode assembly in some embodiments of the present invention.

[0031] Explanation of reference numerals in the attached figures:

[0032] 1: Negative electrode plate;

[0033] 2: Positive electrode plate;

[0034] 11: Negative electrode current collector;

[0035] 12: First negative electrode active layer;

[0036] 13: Second negative electrode active layer;

[0037] 14: Extreme ear;

[0038] 15: Lithium replenishment layer;

[0039] 21: Insulation layer;

[0040] 111: Electrode region;

[0041] 131: Second region. Detailed Implementation

[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] In this invention, all definitions of "length" and "width" are based on the "length L direction" and "width W direction" of the negative electrode current collector. Taking a rectangular functional surface of the negative electrode current collector (the functional surface refers to the two largest and oppositely positioned surfaces in the negative electrode current collector) as an example, the length L direction of the negative electrode current collector refers to the direction of the longest side of its functional surface, denoted as the x-direction; the width W direction refers to the direction of the shortest side of its functional surface, denoted as the y-direction; and the thickness direction of the negative electrode current collector is denoted as the z-direction. For example, if the length of the second region is defined as L2, this means that the dimension of the second region is L2 along the length direction of the negative electrode current collector.

[0044] Figure 1 This is a side view of the negative electrode sheet in some embodiments of the present invention; Figure 2 This is a top view of the negative electrode sheet in some embodiments of the present invention. For example... Figure 1 and Figure 2 As shown, a first aspect of the present invention provides a negative electrode sheet, including a negative electrode current collector 11, the negative electrode current collector 11 having a first functional surface and a second functional surface disposed opposite to each other;

[0045] The first functional surface has an interconnected tab region 111 and an active layer region. The tab region 111 is provided with tabs 14, and the active layer region is provided with a first negative electrode active layer 12. The surface of the first negative electrode active layer 12 away from the negative electrode current collector 11 has a bright area and a dark area.

[0046] The second functional surface is provided with a second negative electrode active layer 13. The surface of the second negative electrode active layer 13 away from the negative electrode current collector 11 includes a first region and a second region 131 that are connected to each other. The first region has a bright area and a dark area, and the second region is a dark area.

[0047] The second region 131, when projected onto the first functional surface, at least partially overlaps with the tab region 111.

[0048] In this invention, the two surfaces with the largest area in the negative electrode current collector 11 and arranged opposite to each other are the first functional surface and the second functional surface of the negative electrode current collector 11.

[0049] The first functional surface of the present invention includes an interconnected tab region 111 and an active layer region, wherein the tab region 11 is provided with a tab 14. The present invention does not limit the arrangement of the tab 14. In the present invention, the tab region 11 can be die-cut to obtain the tab 14; or the tab 14 can be welded on the tab region 11. The active layer region is provided with a first negative electrode active layer 12.

[0050] The second functional surface of the present invention is provided with a second negative electrode active layer 13. The present invention does not particularly limit the first negative electrode active layer 12 and the second negative electrode active layer 13, and they can be negative electrode active layers commonly used in the art. The first negative electrode active layer 12 and the second negative electrode active layer 13 can be the same or different.

[0051] In this invention, the bright area refers to the region with high brightness and a length greater than 4 mm in the image obtained using a laser scanning confocal microscope at a magnification of 4x to 25x; the dark area refers to the region with low brightness in the image obtained using a laser scanning confocal microscope at a magnification of 4x to 25x. Specifically, the surface morphology image of the negative electrode sheet obtained using a laser scanning confocal microscope (Olympus, LEXTOLS3100) can be used to distinguish the bright and dark areas.

[0052] In some embodiments, a lithium replenishment layer 15 is disposed on the surface of the first negative electrode active layer away from the negative electrode current collector. After an electrochemical reaction, the negative electrode active material in the first negative electrode active layer inserts lithium and undergoes volume expansion. This area protrudes in the first negative electrode active layer, forming a lithium replenishment region, which appears as a brighter area (i.e., a bright area) in a laser scanning confocal microscope. The first negative electrode active material layer without the lithium replenishment layer is a non-lithium replenishment region, which appears as a darker area (i.e., a dark area) in a laser scanning confocal microscope. Because the lithium metal foil in the lithium replenishment layer is distributed in a stripe pattern parallel to each other on the surface of the first negative electrode active layer with a certain gap width, the bright and dark areas on the surface of the first negative electrode active layer are alternately distributed when tested with a laser scanning confocal microscope.

[0053] like Figure 2 As shown, the surface of the second negative electrode active layer 13 away from the negative electrode current collector 11 includes a first region and a second region 131 that are interconnected. The first region is provided with a lithium replenishment layer 15. Referring to the description of the lithium replenishment layer provided on the surface of the first negative electrode active layer, after electrochemical reaction, the first region has a bright area and a dark area; the second region is not provided with a lithium replenishment layer, and after electrochemical reaction, the second region is a dark area.

[0054] The first orthographic projection refers to the projection formed when incident light illuminates the second region 131 in a direction perpendicular to the first functional surface. The first orthographic projection at least partially coincides with the tab region 111, which can be understood as the first orthographic projection and the tab region 111 may completely coincide or partially coincide. The first orthographic projection at least partially coincides with the tab region 111 means that the second region 131 and the tab region 111 are at least partially opposite each other.

[0055] The negative electrode of the present invention includes a lithium replenishment layer 15, which allows for lithium replenishment during the charging and discharging process of the battery, effectively improving the initial efficiency of the negative electrode 1. Furthermore, the present invention does not provide a second region 131 on the surface of the second negative electrode active layer 13 opposite to the tab region 111, which can avoid excessive lithium replenishment in the tab region 111 and the generation of lithium plating, thereby improving the cycle performance of the battery.

[0056] During the charging and discharging process of the battery, lithium plating is prone to occur in the tab region 111, and the size of the tab 14 affects the range of lithium plating. In some embodiments of the present invention, when the length L2 of the second region 131 and the length L1 of the tab 14 satisfy: L2 = (1.1~4.0)*L1, lithium plating on the negative electrode 1 can be avoided to the greatest extent while ensuring sufficient lithium replenishment, thereby improving the cycle performance of the battery.

[0057] In some embodiments of the present invention, the width W2 of the second region 131 and the width W0 of the negative electrode current collector 11 satisfy: W2 = (0.05~0.7) * W0.

[0058] It is understood that the second functional surface is completely covered by the second negative electrode active layer 13. The surface of the second negative electrode active layer 13 away from the negative electrode current collector 11 includes a first region where a lithium replenishment layer 15 is provided and a second region 131 where no lithium replenishment layer 15 is provided. When the width of the second region 131 and the width of the negative electrode current collector 11 satisfy the above-mentioned relationship, lithium deposition on the negative electrode 1 can be avoided to the greatest extent while ensuring sufficient lithium replenishment for the negative electrode 1, thereby improving the cycle performance of the battery.

[0059] In some embodiments of the present invention, the first orthographic projection has a first center line extending along a first direction, and the tab region 111 has a second center line extending along the first direction.

[0060] Along the second direction, the minimum distance between the first centerline and the second centerline is ≤0.5mm, and the first direction and the second direction are perpendicular to each other; and / or,

[0061] The first orthographic projection has a third center line extending along the second direction, and the tab region 111 has a fourth center line extending along the second direction.

[0062] Along the first direction, the minimum distance between the third center line and the fourth center line is ≤0.5mm, and the first direction is perpendicular to the second direction.

[0063] This invention does not impose any particular limitation on the first direction and the second direction, as long as the first direction and the second direction are perpendicular to each other. In some embodiments, the first direction can be the length direction (x direction) of the negative electrode current collector, and the second direction can be the width direction (y direction) of the negative electrode current collector.

[0064] This can be understood as follows: the offset between the first orthographic projection and the center line extending in the length direction of the tab region 111 is ≤0.5mm, and / or the offset between the first orthographic projection and the center line extending in the width direction of the tab region 111 is ≤0.5mm. In other words, the second region 131 is positioned opposite the tab region 111, and the deviation between the second region 131 and the tab region 111 in the length or width direction is ≤0.5mm. Through this arrangement, the present invention can further prevent lithium plating in the tab region 111 and improve the cycle performance of the battery.

[0065] In some embodiments of the present invention, the thickness H2 of the negative electrode 1 in the second region 131, the thickness H1 of the negative electrode 1 in the first region, and the thickness H0 of the negative electrode current collector 11 satisfy the following:

[0066] (H2-H0)=(0.55~1.0)*(H1-H0).

[0067] In this invention, the negative electrode 1 in the second region 131 is thinner, while the negative electrode 1 in the first region (open area) is thicker. The thickness of the negative electrode 1 in the second region 131 refers to the average thickness of the negative electrode 1 in the second region 131 after the battery is fully charged and disassembled; the thickness of the negative electrode 1 in the lithium replenishment region refers to the average thickness of the negative electrode 1 in the first region (open area) after the battery is fully charged and disassembled. When the thickness H1 of the negative electrode 1 in the second region 131, the thickness H2 of the negative electrode 1 in the first region, and the thickness H0 of the negative current collector 11 satisfy the above relationship, the second region 131 can effectively accommodate lithium ions from the positive electrode, preventing lithium deposition on the negative electrode, and also ensuring that the thickness of the electrode assembly remains essentially consistent, preventing depressions.

[0068] Figure 3 This is a side view of an electrode assembly in some embodiments of the present invention. For example... Figure 1-3 As shown, a second aspect of the present invention provides an electrode assembly, wherein the negative electrode 1 described above is included.

[0069] It is understood that in this invention, stacking the positive electrode 2 and the negative electrode 1 can obtain a stacked electrode assembly; stacking the positive electrode 2 and the negative electrode 1 and then winding them can obtain a wound electrode assembly.

[0070] Since the electrode assembly of the present invention includes the aforementioned negative electrode 1, lithium plating is less likely to occur on the negative electrode 1 during the charging and discharging process of the battery, which helps to improve the cycle performance of the battery.

[0071] The present invention does not impose any particular limitation on the positive electrode 2, and it can be any positive electrode 2 commonly used in the art.

[0072] In some embodiments of the present invention, a positive electrode 2 is also provided opposite to the negative electrode 1. The positive electrode 2 includes a positive electrode body and an insulating layer 21 disposed on at least one functional surface of the positive electrode body.

[0073] The second orthographic projection of the insulating layer 21 onto the second functional surface and the second region 131 ( Figure 3 (The second region is not shown in the text) at least partially overlaps.

[0074] In this invention, the positive electrode body refers to a conventional positive electrode sheet, which includes a positive current collector and a positive active layer disposed on at least one functional surface of the positive current collector. The functional surface of the positive electrode body refers to the surface of the positive active layer away from the positive current collector. The insulating layer 21 of this invention is disposed on the surface of the positive active layer away from the positive current collector.

[0075] In this invention, the second orthographic projection refers to the projection formed by incident light illuminating the insulating layer 21 in a direction perpendicular to the second functional surface. The second orthographic projection may partially coincide with the second region 131 or completely coincide with it.

[0076] The positive electrode of the present invention is further provided with an insulating layer 21 opposite to the second region 131. The insulating layer 21 can prevent excessive migration of lithium ions from the positive electrode 2 to the negative electrode, thereby further preventing lithium deposition on the negative electrode 1 and improving the cycle performance of the battery.

[0077] In some embodiments of the present invention, the edge of the second region 131 is located within the edge of the second orthographic projection, or the edge of the second region 131 at least partially coincides with the edge of the second orthographic projection.

[0078] It can be understood that when the edge of the second region 131 is located within the edge of the second orthographic projection, the insulating layer 21 completely covers the second region 131 (the area of ​​the insulating layer 21 is larger than the area of ​​the second region 131), which can further prevent excessive migration of lithium ions from the positive electrode 2 to the negative electrode 1, thereby preventing lithium deposition on the negative electrode 1.

[0079] The edge of the second region 131 at least partially overlaps with the edge of the second orthographic projection, including: the edge of the second region 131 completely overlaps with the edge of the second orthographic projection, the insulating layer 21 has the same shape and area as the second region, which can better prevent excessive migration of lithium ions from the positive electrode 2 to the negative electrode 1 while saving the insulating layer 21; the edge of the second region 131 partially overlaps with the edge of the second orthographic projection, the remaining edge of the second region 131 is located within the edge of the second orthographic projection, the area of ​​the insulating layer 21 is larger than the area of ​​the second region 131, which can further prevent excessive migration of lithium ions from the positive electrode 2 to the negative electrode 1, thereby preventing lithium deposition on the negative electrode 1; the edge of the second region 131 partially overlaps with the edge of the second orthographic projection, the remaining edge of the second region 131 is located outside the edge of the second orthographic projection, the area of ​​the insulating layer 21 is smaller than the area of ​​the second region 131, which can prevent excessive migration of lithium ions from the positive electrode 2 to the negative electrode 1.

[0080] In some embodiments of the present invention, when the thickness of the insulating layer 21 is 10 to 30 μm, the flatness of the area after battery formation can be improved, and the gap between the positive and negative electrode plates at the edge of the insulating layer can be avoided, thereby improving the cycle performance of the battery.

[0081] In some embodiments of the present invention, the tab region is formed by a depression in the first negative electrode active layer toward the negative electrode current collector, and the tab is disposed in the depression.

[0082] It is understood that the first negative electrode active layer is recessed towards the negative electrode current collector to form a tab region. The present invention sets the tab in the recess formed by the first negative electrode active layer, which can avoid lithium plating on the negative electrode sheet while replenishing lithium on the negative electrode sheet, thereby improving the cycle performance of the battery.

[0083] A third aspect of the present invention provides a battery comprising the electrode assembly described above.

[0084] It is understood that by placing the above-mentioned electrode assembly in an outer packaging and injecting electrolyte into the outer packaging, the battery of the present invention can be obtained.

[0085] The battery of the present invention, having included the electrode assembly described above, has excellent cycle performance.

[0086] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0087] Example 1

[0088] The battery in this embodiment is prepared by a method including the following steps:

[0089] 1) Negative electrode sheet

[0090] like Figure 1 and Figure 2As shown, a first negative electrode active layer is formed on the first functional surface of the negative electrode current collector, a portion of the first negative electrode active layer on the first functional surface is cleaned to obtain the electrode tab region, and the electrode tab is welded in the electrode tab region.

[0091] A second negative electrode active layer is provided on the second functional surface of the negative electrode current collector, and a lithium replenishment layer (first region) is provided on the surface of the second negative electrode active layer away from the negative electrode current collector. The area on the surface of the second negative electrode active layer away from the negative electrode current collector where no lithium replenishment layer is provided is the second region. The first orthographic projection of the second region on the first functional surface coincides with the tab region.

[0092] The negative electrode current collector is made of copper foil with a thickness of 6 μm; the length of the electrode tab is 6 mm; the length of the second region is 9 mm and the width is 22 mm.

[0093] The first negative electrode active layer and the second negative electrode active layer respectively include silicon-doped graphite, binder SBR, conductive agent Super-p and dispersant CMC, and the mass ratio of silicon-doped graphite, binder, conductive agent and stabilizer is 96.4:2.9:0.25:0.45;

[0094] The lithium replenishment layer is lithium foil.

[0095] 2) Positive electrode plate

[0096] The positive electrode sheet includes a positive electrode body and an insulating layer disposed on two surfaces of the positive electrode body. The positive electrode body includes a positive electrode current collector and a positive electrode active layer disposed on two functional surfaces of the positive electrode current collector.

[0097] The positive electrode current collector is aluminum foil, and the positive electrode active layer includes lithium cobalt oxide, conductive agent acetylene black, and binder PVDF. The mass ratio of lithium cobalt oxide, conductive agent, and binder is 98.5:0.7:0.8.

[0098] The insulating layer comprises a substrate layer (PET layer) and an adhesive layer (acrylic layer) stacked together. The length L3 of the insulating layer is 12mm, the width of the insulating layer is 24mm, and the thickness of the insulating layer is 16um.

[0099] 3) Battery

[0100] The negative electrode sheet and separator from step 1) and the positive electrode sheet from step 2) are stacked and arranged so that the second orthographic projection of the insulating layer on the second functional surface coincides with the second region; then the electrode assembly is wound to obtain an electrode assembly, the electrode assembly is placed in an aluminum-plastic film, and electrolyte is injected into the aluminum-plastic film to obtain a battery.

[0101] The electrolyte is a commercially available electrolyte.

[0102] The battery in this embodiment was fully charged and disassembled. The thickness of the negative electrode sheet was measured. The thickness of the negative electrode sheet in the second region was 60 μm, and the thickness of the negative electrode sheet in the lithium replenishment region was 83 μm.

[0103] Example 2

[0104] The battery preparation method in this embodiment is basically the same as that in embodiment 1, except that in step 2), the positive electrode does not contain an insulating layer.

[0105] Example 3

[0106] The battery preparation method in this embodiment is basically the same as that in embodiment 1, except that in step 1), the length of the second region is 60 mm, the length of the tab is 6 mm, and the ratio of the length of the second region to the length of the tab is 10:1.

[0107] Example 4

[0108] The battery preparation method in this embodiment is basically the same as that in embodiment 1, except that: in step 1), the width of the second region of the negative electrode sheet is 60mm and the width of the negative electrode sheet is 60mm.

[0109] Example 5

[0110] The battery preparation method in this embodiment is basically the same as that in embodiment 1, except that in step 2), the thickness of the insulating layer is 50 μm.

[0111] Comparative Example 1

[0112] The preparation method of the battery in this comparative example is basically the same as that in Example 1, except that:

[0113] In step 1), a lithium replenishment layer (excluding the second region) is provided on the surface of the second negative electrode active layer away from the negative electrode current collector.

[0114] Comparative Example 2

[0115] The preparation method of the battery in this comparative example is basically the same as that in Comparative Example 1, except that:

[0116] In step 2), the positive electrode does not contain an insulating layer.

[0117] Performance testing

[0118] The following performance tests were performed on the batteries of the examples and comparative examples, and the results are shown in Table 1;

[0119] 1. Perform charge-discharge cycle tests on the battery at 1C / 1C to obtain the initial discharge capacity and the discharge capacity after 800 cycles, and calculate the capacity retention rate; obtain the initial thickness of the battery and the thickness after 800 cycles, and calculate the thickness expansion rate.

[0120] Obtain the battery's first discharge capacity and first charge capacity, and calculate the first efficiency: First efficiency = First discharge capacity / First charge capacity.

[0121] 2. Energy density

[0122] Energy density = Battery capacity * Platform voltage / Battery volume

[0123] Table 1

[0124] Example 1 89.4％ 12.1％ 764 91.75％ Example 2 89.1％ 12.9％ 761 91.64％ Example 3 88.7％ 13.9％ 758 89.5％ Example 4 88.1％ 13.4％ 749 89.65％ Example 5 83.1％ 14.5％ 743 91.23％ Comparative Example 1 82.1％ 16.8％ 737 87.7％ Comparative Example 2 81.9％ 17.1％ 739 88.1％

[0125] As can be seen from Table 1, the battery of the present invention has excellent cycle capacity retention and low thickness expansion rate.

[0126] The various embodiments in this specification are described in a related manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on its differences from other embodiments. The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A negative electrode sheet characterized by comprising: Includes a negative electrode current collector, wherein the negative electrode current collector has a first functional surface and a second functional surface disposed opposite to each other; The first functional surface has an interconnected tab region and an active layer region. The tab region is provided with tabs, and the active layer region is provided with a first negative electrode active layer. The surface of the first negative electrode active layer away from the negative electrode current collector includes a lithium replenishment region and a non-lithium replenishment region. The lithium replenishment region is displayed as a bright area under a laser scanning confocal microscope, and the non-lithium replenishment region is displayed as a dark area under a laser scanning confocal microscope. The second functional surface is provided with a second negative electrode active layer. The surface of the second negative electrode active layer away from the negative electrode current collector includes a first region and a second region that are connected to each other. The first region has a bright area and a dark area, and the second region is a dark area. The first orthographic projection of the second region located on the second functional surface onto the first functional surface at least partially overlaps with the tab region located on the first functional surface; The length L2 of the second region and the length LI of the tab satisfy: .

2. The negative electrode sheet according to claim 1, characterized in that, The width W2 of the second region and the width W0 of the negative electrode current collector satisfy: .

3. The negative electrode sheet according to claim 1, characterized in that, The first orthographic projection has a first centerline extending along a first direction, and the tab region has a second centerline extending along the first direction. Along the second direction, the minimum distance between the first centerline and the second centerline is ≤0.5mm, and the first direction and the second direction are perpendicular to each other; and / or, The first orthographic projection has a third center line extending along the second direction, and the tab region has a fourth center line extending along the second direction; Along the first direction, the minimum distance between the third center line and the fourth center line is ≤0.5mm; the first direction is perpendicular to the second direction.

4. The negative electrode sheet according to claim 1, characterized in that, The thickness H2 of the negative electrode in the second region, the thickness H1 of the negative electrode in the first region, and the thickness H0 of the negative current collector satisfy the following: 。 5. An electrode assembly, characterized in that, Includes the negative electrode sheet as described in any one of claims 1-4.

6. The electrode assembly according to claim 5, characterized in that, It also includes a positive electrode sheet disposed opposite to the negative electrode sheet, the positive electrode sheet including a positive electrode body and an insulating layer disposed on at least one functional surface of the positive electrode body; The second orthographic projection of the insulating layer onto the second functional surface at least partially overlaps with the second region.

7. The electrode assembly according to claim 6, characterized in that, The edge of the second region lies within the edge of the second orthographic projection, or the edge of the second region at least partially coincides with the edge of the second orthographic projection.

8. The electrode assembly according to claim 7, characterized in that, The tab region is formed by the first negative electrode active layer being recessed in the direction of the negative electrode current collector, and the tab is disposed in the recess.

9. A battery, characterized in that, Includes the electrode assembly as described in any one of claims 5-8.

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