Negative pole piece and battery

Abstract

The utility model discloses a negative pole piece and a battery, the negative pole piece comprises a current collector, a first negative active material coating arranged on at least one surface of the current collector along the thickness direction, and a resistance layer arranged on one surface of the first negative active material coating far away from the current collector, and the second negative electrode active material coating is arranged on one surface, far away from the first negative electrode active material coating, of the resistance layer. The resistive layer is additionally arranged between the first negative electrode active material coating and the second negative electrode active material coating, and the resistive layer generates heat in the charging process of the battery, so that the migration rate of lithium ions in the second negative electrode active material coating can be increased, the heat generated by the current collector can be reduced, and the service life of the battery is prolonged. The temperature distribution in the negative pole piece is more uniform, the high-temperature performance deterioration of the battery is avoided, and the quick charging capability and the safety of the battery are improved.

Description

Technical Field

[0001] This utility model relates to the field of battery technology, specifically to a negative electrode sheet and a battery. Background Technology

[0002] With the widespread use of electronic devices, the market demand for fast charging capabilities of batteries is increasing to meet user convenience. The main limitation of fast charging capability lies on the negative electrode side of the battery. This is because when using high-rate fast charging, the negative electrode cannot quickly embed all lithium ions, causing some lithium ions to precipitate on the surface of the negative electrode. Lithium deposition not only leads to rapid capacity decay of the battery, but the generated lithium dendrites may also puncture the separator, causing safety issues.

[0003] Currently, the common methods used in the industry to address these issues are to improve the kinetic performance of the electrolyte by reducing the viscosity of the electrolyte system and increasing the lithium salt concentration. However, these methods typically worsen the high-temperature performance of the battery. Utility Model Content

[0004] To address the aforementioned issues, this invention provides a negative electrode sheet and a battery. By adding a resistive layer between the first negative electrode active material coating and the second negative electrode active material coating, the resistive layer generates heat during high-rate charging of the battery. This heat generation helps to increase the migration rate of lithium ions in the second negative electrode active material coating above the resistive layer, while simultaneously reducing heat generation in the current collector. This results in a more uniform temperature distribution within the negative electrode sheet, preventing the battery's high-temperature performance from deteriorating and improving the battery's fast-charging capability and safety.

[0005] Specifically, the following technical solutions are provided:

[0006] The first aspect of this utility model provides a negative electrode sheet, comprising:

[0007] current collector,

[0008] A first negative electrode active material coating is disposed on at least one side of the current collector along the thickness direction.

[0009] A resistive layer disposed on the side of the first negative electrode active material coating away from the current collector, and

[0010] A second negative electrode active material coating is disposed on the side of the resistive layer away from the first negative electrode active material coating.

[0011] In some preferred embodiments of the utility model, the resistance of the resistance layer is greater than the resistance of the current collector, more preferably, the ratio of the resistance of the resistance layer to the resistance of the current collector is 1.5-2.5, for example, 1.5, 2.0, 2.5, etc., and the resistance ratio of the two can also be any value within the range. By setting the resistance layer with a resistance greater than that of the current collector, the resistance layer can generate sufficient heat during charging to increase the migration rate of lithium ions in the second negative active material coating above the resistance layer, while avoiding too large temperature differences in the overall pole piece, more preferably, the resistance ratio of the resistance layer to the current collector is controlled within the interval of 1.5-2.5.

[0012] In some preferred embodiments of the utility model, the thickness h0 of the resistance layer is 5-20 μm, and the thickness of the resistance layer will affect the energy density of the battery. If the resistance layer is too thick, it will significantly reduce the volume energy density and weight energy density of the battery. If it is too thin, although it will reduce the impact on the energy density of the battery, the thin resistance layer will increase the manufacturing difficulty and cost of the material. Therefore, preferably, the thickness h0 of the resistance layer is controlled within the interval of 5-20 μm, including but not limited to 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, etc.

[0013] In some preferred embodiments of the utility model, the resistance layer is provided in a mesh structure, such as a copper mesh, a nickel mesh, a stainless steel mesh, or a carbon cloth provided in a mesh structure, to reduce the impact of the resistance layer on the energy density of the battery and ion migration.

[0014] In some preferred embodiments of the utility model, the mesh structure includes first and second radial lines arranged intersectingly, wherein the first radial line has a width of 0.5-2 μm in the normal projection of the first negative active material coating in a direction perpendicular to the first negative active material coating, and the second radial line has a width of 0.5-2 μm in the normal projection of the first negative active material coating in a direction perpendicular to the first negative active material coating. If the radial line of the resistance layer mesh structure is too wide, it will affect ion transfer and cannot quickly diffuse into the first negative active material coating below the resistance layer, affecting the fast charging performance of the battery. If it is too fine, it will increase the manufacturing difficulty and cost of the resistance layer. Preferably, the width of the first and second radial lines in the resistance layer mesh structure is controlled within 0.5-2 μm, for example, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, etc., so that ions can quickly pass through the resistance layer while reducing the preparation cost.

[0015] In some preferred embodiments of the present application, the resistance layer comprises a plurality of meshes with the same or different areas, the porosity of the resistance layer is 70-98%, and the area of the mesh is 50-150mm 2 . The porosity and mesh size of the resistance layer affect ion transmission, mechanical properties of the resistance layer, manufacturing cost, etc. If the porosity and mesh area are too small, the ion transmission from the second negative active material coating to the first negative active material coating will be hindered, thereby reducing the capacity of the battery and affecting the fast charging performance of the battery. If the porosity and mesh area are too large, the mechanical properties of the resistance layer are poor, which is difficult to adapt to the large volume change of the negative electrode sheet during charging and discharging, and is prone to breakage, and the manufacturing cost is high. To reduce the influence of the resistance layer on ion transmission while ensuring the mechanical properties of the resistance layer, the porosity of the resistance layer is preferably controlled in the range of 70-98%, such as 70%, 75%, 80%, 85%, 90%, 95%, 98%, etc. The area of the mesh is controlled in the range of 50-150mm 2 , such as 50mm 2 , 60mm 2 , 70mm 2 , 80mm 2 , 90mm 2 , 100mm 2 , 110mm 2 , 120mm 2 , 130mm 2 , 140mm 2 , 150mm 2 , etc.

[0016] In some preferred embodiments of the present application, the thickness of the first negative active material coating is h1, the thickness of the second negative active material coating is h2, and 0.8≤h1 / h2≤2, such as h1 / h2=0.8, 1, 1.2, 1.4, 1.6, 1.8, 2, etc., including but not limited to the above-mentioned ratios. If the thickness ratio of the first negative active material coating to the second negative active material coating is too small, the second active material coating is thicker, the resistance layer is difficult to heat the part of the second negative active material coating far from the resistance layer during charging, and the temperature of the thin first negative active material coating between the resistance layer and the current collector is relatively high, resulting in a relatively large temperature difference in the electrode sheet, which will deteriorate the high temperature performance of the battery. If the ratio is too large, the thickness of the second negative active material layer is thin, and the resistance layer cannot effectively improve the ion migration rate of the negative active material layer as a whole, and the fast charging capacity of the electrode sheet is limited. To effectively improve the fast charging capacity of the battery while making the temperature distribution in the negative electrode sheet more uniform, the ratio of h1 / h2 is preferably controlled in the range of 0.8-2.

[0017] In some preferred embodiments of the utility model, one end of the resistance layer is provided with a first blank area in the length direction, and the other end is provided with a second blank area; one end of the current collector is provided with a first empty foil area in the length direction, and the other end is provided with a second empty foil area; wherein the first blank area and the first empty foil area are located on the same side of the negative pole piece, and the first blank area and the first empty foil area are electrically connected; the second blank area and the second empty foil area are located on the same side of the negative pole piece, and the second blank area and the second empty foil area are electrically connected; the first empty foil area or the second empty foil area constitutes a negative pole lug.

[0018] In some preferred embodiments of the utility model, one end of the current collector is electrically connected with the first lug in the length direction, and one end of the resistance layer is electrically connected with the second lug in the length direction, the first lug and the second lug are arranged on the same side of the negative pole piece, and the first lug and the second lug are electrically connected.

[0019] The above-mentioned forming electric connection mode contains but is not limited to welding.

[0020] The utility model provides a kind of battery comprising the negative pole piece of the first aspect.

[0021] Compared with prior art, the utility model has the beneficial effects that:

[0022] The utility model provides a kind of negative pole piece, by increasing resistance layer between first negative pole active material coating and second negative pole active material coating, so that resistance layer can generate heat in the process of battery large ratio charging, to improve the migration rate of lithium ion in second negative pole active material coating above resistance layer, to improve the fast charging capacity of battery as a whole;While under the shunt effect of resistance layer, the heat production of current collector can be reduced, so that the temperature distribution in the interior of negative pole piece is more uniform, thereby effectively avoiding the deterioration of battery performance caused by local temperature of negative pole piece being too high, which is conducive to improving the fast charging capacity and safety of battery. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 It is the structure schematic view of a kind of negative pole piece in the utility model embodiment 1;

[0024] Figure 2 It is the structure schematic view of the section of a kind of negative pole piece in the utility model embodiment 1;

[0025] Figure 3 It is the structure schematic view of resistance layer in the utility model embodiment 1;

[0026] Figure 4 It is the electric connection schematic view of the positive pole piece and negative pole piece in a kind of battery in the utility model embodiment 1;

[0027] Figure 5 Figure 2 is a schematic diagram of the electrical connection of the positive and negative electrode sheets in the battery of Embodiment 2 of the present application;

[0028] Reference signs in the drawings: 1, negative electrode sheet; 11, current collector; 111, first empty foil area; 112, second empty foil area; 12, first negative active material coating; 13, resistance layer; 131: first radial line; 132: second radial line; 133: mesh hole; 134: first blank area; 135: second blank area; 14: first negative active material coating; 2, positive electrode sheet; 3, negative electrode tab; 31, first electrode tab; 32, second electrode tab; 4, positive electrode tab; h0, thickness of the resistance layer; h1, thickness of the first negative active material coating; h2, thickness of the second negative active material coating. DETAILED DESCRIPTION

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this description, the terms "may" and "might" include any one or all of the possible combinations of the constituent items they describe. The terms "comprises" and "comprising" as used herein are to be construed as meaning "including, but not limited to".

[0030] The present application will be further described by examples with reference to the accompanying drawings so that those skilled in the art can better understand and implement the present application, but the examples are not intended to limit the present application.

[0031] Embodiment 1

[0032] Referring to Figures 1-4 Embodiment 1 of the present application provides a negative electrode sheet and a battery, the negative electrode sheet comprising a current collector 11, a first negative active material coating 12 disposed on one side of the current collector 11 along the thickness direction, a resistance layer 13 disposed on the side of the first negative active material coating 12 away from the current collector 11, and a second negative active material coating 14 disposed on the side of the resistance layer 13 away from the first negative active material coating 12.

[0033] In the embodiment, the resistance layer 13 is a copper mesh with a mesh structure, including first radial lines 131 and second radial lines 132 arranged in intersection, the first radial lines 131 and the second radial lines 132 have a projection width of 0.5 μm on the first negative electrode active material coating 12 in a direction perpendicular to the first negative electrode active material coating 12; and the copper mesh has a plurality of mesh holes 133 with the same area, the area of the mesh hole 133 is 70.2 mm 2 .

[0034] In the embodiment, the thickness h0 of the resistance layer 13 is 19.1 μm; the ratio of the thickness h1 of the first negative electrode active material coating 12 to the thickness h2 of the second negative electrode active material coating 14 is 1.7.

[0035] In the embodiment, one end of the resistance layer 13 in the length direction is provided with a first blank area 134, and the other end is provided with a second blank area 135; one end of the current collector 11 in the length direction is provided with a first blank foil area 111, and the other end is provided with a second blank foil area 112; wherein the first blank area 134 and the first blank foil area 111 are located on the same side of the negative electrode tab, and the first blank area 134 and the first blank foil area 111 are electrically connected by welding; the second blank area 135 and the second blank foil area 112 are located on the same side of the negative electrode tab, and the second blank area 135 and the second blank foil area 112 are electrically connected by welding; the first blank foil area 111 of the current collector 11 serves as the negative electrode tab 3.

[0036] The preparation of the negative electrode tab in the embodiment includes the following steps:

[0037] (1) The first active material artificial graphite, carboxymethyl cellulose (CMC), styrene butadiene rubber (SBR), and conductive carbon black (Super-P) are placed in a stirring kettle in a ratio of 95:1.5:2.5:1, and pure water is added and stirred uniformly to obtain a first negative electrode slurry.

[0038] The second active material artificial graphite, carboxymethyl cellulose (CMC), styrene butadiene rubber (SBR), and conductive carbon black (Super-P) are placed in a stirring kettle in a ratio of 95.5:1.5:2:1, and pure water is added and stirred uniformly to obtain a second negative electrode slurry.

[0039] (2) The first negative electrode slurry is uniformly coated on the negative electrode current collector copper foil, and after drying, a first negative electrode active material coating is obtained; the copper mesh is fixed on the first negative electrode active material coating by pre-rolling; the second negative electrode slurry is uniformly coated on the copper mesh, and after drying, a negative electrode tab is obtained.

[0040] (3) The blank areas at both ends of the copper mesh in the negative electrode tab are connected to the blank foil areas of the negative electrode current collector copper foil by welding to have electronic communication capability.

[0041] The embodiment also provides a battery comprising the negative electrode sheet, including a negative electrode sheet 1, a positive electrode sheet 2, a negative electrode tab 3, a positive electrode tab 4, a separator and an electrolyte, and the specific preparation process is as follows:

[0042] Preparation of the positive electrode sheet: lithium iron phosphate, polyvinylidene fluoride (PVDF) and conductive carbon black (Super-P) are mixed in a ratio of 97:2:1, and after stirring, a positive electrode slurry is formed. The positive electrode slurry is coated on an aluminum foil, dried in an oven, and then prepared into a positive electrode sheet by rolling and slitting. The aluminum foil at one end of the positive electrode sheet is connected to the positive electrode tab by welding.

[0043] Separator: a PE porous polymer film is used as the separator.

[0044] Preparation of the electrolyte: ethylene carbonate (EC), methyl ethyl carbonate (EMC) and diethyl carbonate (DEC) are mixed in a volume ratio of 3:5:2, and then fully dried lithium salt LiPF6 is dissolved in the mixed organic solvent in a ratio of 1.2 mol / L to prepare the electrolyte.

[0045] Battery preparation: the positive electrode sheet, the separator and the negative electrode sheet are arranged in order, a layer of isolation film is placed in the middle of each pair of positive and negative electrodes, and a bare battery cell is obtained by winding. The bare battery cell is placed in an outer packaging shell, the prepared electrolyte is injected into the dried bare battery, and the lithium ion battery is obtained after vacuum packaging, standing, formation, shaping and other processes.

[0046] Embodiment 2

[0047] Reference Figure 5 The embodiment provides a negative electrode sheet and a battery, and the difference from the embodiment 1 is that the negative electrode sheet adopts a separated tab, and specifically, one end of the current collector copper foil 11 is connected to the first tab 31 by welding, one end of the resistance layer copper mesh 13 on the same side is connected to the second tab 32 by welding, and the first tab 31 and the second tab 31 are electrically connected by welding.

[0048] Embodiment 3

[0049] The embodiment provides a negative electrode sheet and a battery, and the difference from the embodiment 1 is that:

[0050] In the embodiment, the resistance layer 13 is a copper mesh with a mesh structure, including a first radial line 131 and a second radial line 132 intersecting each other, and the positive projection width of the first radial line 131 and the second radial line 132 on the first negative active material coating 12 along the direction perpendicular to the first negative active material coating 12 is 1.7 μm; and the copper mesh has a plurality of mesh holes 133 with the same area, and the area of the mesh hole 133 is 141.6 mm2 .

[0051] In this embodiment, the thickness h0 of the resistance layer 13 is 10.3 μm; the ratio of the thickness h1 of the first negative electrode active material coating layer 12 to the thickness h2 of the second negative electrode active material coating layer 14 is 1.9.

[0052] The rest are consistent, and the corresponding negative electrode sheet and battery are prepared.

[0053] Example 4

[0054] This embodiment provides a negative electrode sheet and a battery, which are only different from the embodiment 1 in that:

[0055] In this embodiment, the resistance layer 13 is a copper mesh with a mesh structure, including first radial lines 131 and second radial lines 132 arranged intersectingly, the positive projection width of the first radial lines 131 and the second radial lines 132 on the first negative electrode active material coating layer 12 along the direction perpendicular to the first negative electrode active material coating layer 12 is 1.0 μm; and the copper mesh has a plurality of mesh holes 133 with the same area, the area of the mesh hole 133 is 59.1 mm 2 .

[0056] In this embodiment, the thickness h0 of the resistance layer 13 is 12.5 μm; the ratio of the thickness h1 of the first negative electrode active material coating layer 12 to the thickness h2 of the second negative electrode active material coating layer 14 is 1.4.

[0057] The rest are consistent, and the corresponding negative electrode sheet and battery are prepared.

[0058] Example 5

[0059] This embodiment provides a negative electrode sheet and a battery, which are only different from the embodiment 1 in that:

[0060] In this embodiment, the resistance layer 13 is a copper mesh with a mesh structure, including first radial lines 131 and second radial lines 132 arranged intersectingly, the positive projection width of the first radial lines 131 and the second radial lines 132 on the first negative electrode active material coating layer 12 along the direction perpendicular to the first negative electrode active material coating layer 12 is 1.2 μm; and the copper mesh has a plurality of mesh holes 133 with the same area, the area of the mesh hole 133 is 111.0 mm 2 .

[0061] In this embodiment, the thickness h0 of the resistance layer 13 is 18.9 μm; the ratio of the thickness h1 of the first negative electrode active material coating layer 12 to the thickness h2 of the second negative electrode active material coating layer 14 is 1.0.

[0062] The rest are consistent, and the corresponding negative electrode sheet and battery are prepared.

[0063] Example 6

[0064] The embodiment provides a negative pole piece and a battery, which are different from the embodiment 1 only in that:

[0065] In the embodiment, the resistance layer 13 is a copper mesh with a mesh structure, includes the first radial line 131 and the second radial line 132 which are arranged in intersection, the positive projection width of the first radial line 131 and the second radial line 132 on the first negative pole active material coating 12 along the direction perpendicular to the first negative pole active material coating 12 is 0.7 μm; and the copper mesh has a plurality of mesh holes 133 with the same area, the area of the mesh hole 133 is 93.8 mm 2 .

[0066] In the embodiment, the thickness h0 of the resistance layer 13 is 5.6 μm; the ratio of the thickness h1 of the first negative pole active material coating 12 to the thickness h2 of the second negative pole active material coating 14 is 0.9.

[0067] The rest are consistent, and the corresponding negative pole piece and battery are prepared.

[0068] Comparative Example 1

[0069] The comparative example provides a negative pole piece and a battery, which are different from the embodiment 1 only in that:

[0070] In the comparative example, the resistance layer 13 is a copper mesh with a mesh structure, includes the first radial line 131 and the second radial line 132 which are arranged in intersection, the positive projection width of the first radial line 131 and the second radial line 132 on the first negative pole active material coating 12 along the direction perpendicular to the first negative pole active material coating 12 is 0.9 μm; and the copper mesh has a plurality of mesh holes 133 with the same area, the area of the mesh hole 133 is 102.2 mm 2 .

[0071] In the comparative example, the thickness h0 of the resistance layer 13 is 7.0 μm; the ratio of the thickness h1 of the first negative pole active material coating 12 to the thickness h2 of the second negative pole active material coating 14 is 0.6.

[0072] The rest are consistent, and the corresponding negative pole piece and battery are prepared.

[0073] Comparative Example 2

[0074] The comparative example provides a negative pole piece and a battery, which are different from the embodiment 1 only in that:

[0075] In the present comparative example, the resistance layer 13 is a copper mesh having a mesh structure, including first radial lines 131 and second radial lines 132 arranged intersectingly, the positive projection width of the first radial lines 131 and the second radial lines 132 on the first negative electrode active material coating 12 along a direction perpendicular to the first negative electrode active material coating 12 is 1.5 μm; and the copper mesh has a plurality of mesh holes 133 of the same area, the area of the mesh hole 133 is 101.3 mm 2 .

[0076] In the present comparative example, the thickness h0 of the resistance layer 13 is 25.3 μm; the ratio of the thickness h1 of the first negative electrode active material coating 12 to the thickness h2 of the second negative electrode active material coating 14 is 1.5.

[0077] The rest are consistent, and the corresponding negative electrode sheet and battery are prepared.

[0078] Comparative Example 3

[0079] The present comparative example provides a negative electrode sheet and a battery, which are only different from the example 1 in that:

[0080] In the present comparative example, the resistance layer 13 is a copper mesh having a mesh structure, including first radial lines 131 and second radial lines 132 arranged intersectingly, the positive projection width of the first radial lines 131 and the second radial lines 132 on the first negative electrode active material coating 12 along a direction perpendicular to the first negative electrode active material coating 12 is 2.3 μm; and the copper mesh has a plurality of mesh holes 133 of the same area, the area of the mesh hole 133 is 128.1 mm 2 .

[0081] In the present comparative example, the thickness h0 of the resistance layer 13 is 16.4 μm; the ratio of the thickness h1 of the first negative electrode active material coating 12 to the thickness h2 of the second negative electrode active material coating 14 is 1.1.

[0082] The rest are consistent, and the corresponding negative electrode sheet and battery are prepared.

[0083] Comparative Example 4

[0084] The present comparative example provides a negative electrode sheet and a battery, which are only different from the example 1 in that:

[0085] In the present comparative example, the resistance layer 13 is a copper mesh having a mesh structure, including first radial lines 131 and second radial lines 132 arranged intersectingly, the positive projection width of the first radial lines 131 and the second radial lines 132 on the first negative electrode active material coating 12 along a direction perpendicular to the first negative electrode active material coating 12 is 1.2 μm; and the copper mesh has a plurality of mesh holes 133 of the same area, the area of the mesh hole 133 is 36.9 mm 2 .

[0086] In the present comparative example, the thickness h0 of the resistance layer 13 is 7.8 μm; the ratio of the thickness h1 of the first negative electrode active material coating layer 12 to the thickness h2 of the second negative electrode active material coating layer 14 is 1.7.

[0087] The rest are consistent, and the corresponding negative electrode sheet and battery are prepared.

[0088] Performance test

[0089] The batteries prepared in the above-mentioned example 1, examples 3-6 and comparative examples 1-4 are subjected to fast charging and high temperature performance tests, and the specific test process is as follows:

[0090] Fast charging performance test: the battery is charged at 0.33C rate to 3.65V in a 25℃ oven, and then discharged at 0.33C rate to 2.5V, and the above steps are repeated for three weeks, and the capacity of the last week is taken as the actual capacity C0 of the battery; then the battery is charged at 6C0 current to 3.65V in a 25℃ oven, and then discharged at 6C0 current to 2.5V, and the above charging and discharging cycle is carried out for 50 weeks, and finally the negative electrode interface is observed after full charging; the judgment standard is as follows:

[0091] Mild lithium precipitation: the lithium precipitation area is not more than 10% of the area of the sheet;

[0092] Moderate lithium precipitation: the lithium precipitation area accounts for 10% to 50% of the area of the sheet;

[0093] Severe lithium precipitation: the lithium precipitation area accounts for more than 50% of the area of the sheet.

[0094] 45℃ cycle performance test: the battery is charged at 1C rate to 3.65V in a 45℃ oven, and then discharged at 1C rate to 2.5V, and the discharge capacity at this time is recorded as the initial battery capacity; repeat the above charging and discharging cycle, and intercept the corresponding cycle number when the battery is cycled to 80% of the initial battery capacity.

[0095] The test results are shown in Table 1 below:

[0096] Table 1

[0097]

[0098] In the table, W is the positive projection width of the first diameter and the second diameter of the resistance layer on the first negative electrode active material coating layer in the direction perpendicular to the first negative electrode active material coating layer; S is the area of a single mesh of the resistance layer.

[0099] As shown in Table 1, the lithium batteries prepared in Examples 1-6 do not show lithium precipitation at the negative electrode interface after 50 cycles at a 6C rate, while the comparative example 1 with a too thick second negative active material coating and the comparative example 3 with a too large diameter of the resistance layer show slight lithium precipitation at the negative electrode interface after the same number of cycles at the same rate.

[0100] As shown in the comparative example 2, further increasing the thickness of the resistance layer does not significantly improve the cycle life of the battery at high temperature, and the volume energy density of the battery is reduced with the increase of the thickness of the resistance layer. In addition, as shown in the comparative example 4, when the mesh area of the resistance layer is too small, the migration of lithium ions from the second negative active material coating to the first negative active material coating is seriously affected, resulting in moderate lithium precipitation at the negative electrode interface, and the cycle stability at high temperature is significantly reduced.

[0101] The above examples are only preferred examples for fully illustrating the present application, and the protection scope of the present application is not limited thereto. Any equivalent substitutions or transformations made by those skilled in the art based on the present application are within the protection scope of the present application. The protection scope of the present application is subject to the claims.

Claims

1. A negative electrode sheet, characterized by, The negative electrode plate comprises: a current collector (11), a first negative electrode active material coating (12) arranged on at least one side of the current collector (11) along the thickness direction, a resistance layer (13) arranged on the side of the first negative electrode active material coating (12) away from the current collector (11), and a second negative electrode active material coating (14) arranged on the side of the resistance layer (13) away from the first negative electrode active material coating (12).

2. The negative electrode sheet according to claim 1, characterized by The resistance of the resistance layer (13) is greater than the resistance of the current collector (11).

3. The negative electrode sheet according to claim 2, characterized by The ratio of the resistance of the resistance layer (13) to the resistance of the current collector (11) is 1.5-2.

5.

4. The negative electrode sheet according to claim 1, wherein The thickness h0 of the resistance layer (13) is 5-20 μm.

5. The negative electrode sheet according to claim 1, wherein The thickness of the first negative electrode active material coating (12) is h1, and the thickness of the second negative electrode active material coating (14) is h2, satisfying 0.8 ≤ h1 / h2 ≤ 2.

6. The negative electrode sheet according to claim 1, wherein The resistance layer (13) is arranged in a mesh structure.

7. The negative electrode sheet according to claim 6, characterized by The resistance layer (13) is a copper mesh, a nickel mesh, a stainless steel mesh, or a carbon cloth arranged in a mesh structure.

8. The negative electrode sheet according to claim 6 or 7, characterized in that, The mesh structure comprises first radial lines (131) and second radial lines (132) arranged in intersection; The width of the orthographic projection of the first radial line (131) on the first negative electrode active material coating (12) along the direction perpendicular to the first negative electrode active material coating (12) is 0.5-2 μm, and the width of the orthographic projection of the second radial line (132) on the first negative electrode active material coating (12) along the direction perpendicular to the first negative electrode active material coating (12) is 0.5-2 μm.

9. The negative electrode sheet according to claim 8, characterized by, The resistance layer (13) comprises a plurality of mesh holes (133) with the same or different areas; The porosity of the resistance layer (13) is 70%-98%; The area of the mesh (133) is 50-150 mm 2 .

10. The negative electrode plate of claim 1, wherein, One end of the resistance layer (13) in the length direction is provided with a first blank area (134), and the other end is provided with a second blank area (135); one end of the current collector (11) in the length direction is provided with a first blank foil area (111), and the other end is provided with a second blank foil area (112); The first blank area (134) and the first blank foil area (111) are located on the same side of the negative electrode plate, and the first blank area (134) and the first blank foil area (111) are electrically connected; the second blank area (135) and the second blank foil area (112) are located on the same side of the negative electrode plate, and the second blank area (135) and the second blank foil area (112) are electrically connected; The first blank foil area (111) or the second blank foil area (112) constitutes a negative electrode tab (3).

11. The negative electrode sheet according to claim 1, wherein One end of the current collector (11) in the length direction is electrically connected with a first tab (31), and one end of the resistance layer (13) in the length direction is electrically connected with a second tab (32); the first tab (31) and the second tab (32) are arranged on the same side of the negative electrode plate, and the first tab (31) and the second tab (32) are electrically connected.

12. A battery, characterized by The negative electrode plate comprises the negative electrode plate according to any one of claims 1-11.

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