A negative electrode sheet and its application

Abstract

The present invention provides a negative electrode sheet and its application. The negative electrode sheet of the present invention includes a negative electrode current collector, a first functional layer disposed on a first functional surface of the negative electrode current collector, and a second functional layer disposed on a second functional surface of the negative electrode current collector. In the thickness direction of the negative electrode sheet, the first functional layer includes a first negative electrode active layer and a second negative electrode active layer stacked together, with the first negative electrode active layer being close to the first functional surface. The second functional layer includes a third negative electrode active layer. The first negative electrode active layer includes a first negative electrode active material, the second negative electrode active layer includes a second negative electrode active material, and the third negative electrode active layer includes a third negative electrode active material. The particle size of the second negative electrode active material is smaller than that of the first negative electrode active material; and / or the particle size of the second negative electrode active material is smaller than that of the third negative electrode active material. This negative electrode sheet can enable a battery to have both relatively excellent cycle expansion performance and cycle performance.

Description

Technical Field

[0001] The invention relates to a negative electrode sheet and application thereof, belonging to the field of batteries. Background Art

[0002] As various fields have increasingly higher requirements for the energy density of consumer polymer lithium-ion batteries, existing technologies usually increase the energy density of lithium-ion batteries by making the electrodes in lithium-ion batteries thicker. However, when the current is too large, the thick electrodes are not only prone to expansion, but also prone to lithium deposition, which in turn leads to deterioration of the battery's cycle performance.

[0003] Therefore, it is necessary to develop a battery electrode that can provide both excellent cycle expansion performance and cycle performance. Summary of the Invention

[0004] The present invention provides a negative electrode sheet, which can enable a battery to have both relatively excellent cycle expansion performance and cycle performance.

[0005] The present invention provides a battery comprising the above-mentioned negative electrode sheet, thereby having both relatively excellent cycle expansion performance and cycle performance.

[0006] The present invention provides a negative electrode sheet, comprising a negative electrode current collector, a first functional layer disposed on a first functional surface of the negative electrode current collector, and a second functional layer disposed on a second functional surface of the negative electrode current collector;

[0007] In the thickness direction of the negative electrode sheet, the first functional layer includes a first negative electrode active layer and a second negative electrode active layer stacked in a direction away from the negative electrode current collector; the second functional layer includes a third negative electrode active layer;

[0008] The first negative electrode active layer includes a first negative electrode active material, the second negative electrode active layer includes a second negative electrode active material, and the third negative electrode active layer includes a third negative electrode active material;

[0009] The particle size of the second negative electrode active material is smaller than that of the first negative electrode active material; and / or the particle size of the second negative electrode active material is smaller than that of the third negative electrode active material.

[0010] The negative electrode sheet as described above, wherein the particle size of the first negative electrode active material is larger than the particle size of the third negative electrode active material.

[0011] In the negative electrode sheet as described above, D501 of the first negative electrode active material and D502 of the second negative electrode active material satisfy the following relationship:

[0012] 1.5≤D501 / D502≤5.5.

[0013] The negative electrode sheet as described above, wherein D501 is 15-20 μm; and / or

[0014] D502 is 3~10μm.

[0015] The negative electrode sheet as described above, wherein the D503 of the third negative electrode active material is 10-15 μm.

[0016] The negative electrode sheet as described above, wherein the compaction density of the first negative electrode active material is greater than the compaction density of the second negative electrode active material; and / or,

[0017] The fast charging capability of the second negative electrode active material is greater than the fast charging capability of the first negative electrode active material.

[0018] The negative electrode sheet as described above, wherein the compaction density of the first negative electrode active material is greater than or equal to 1.8 g / cm 3 and / or,

[0019] The charge rate of the second negative electrode active material is greater than or equal to 3C.

[0020] The negative electrode sheet as described above, wherein the total surface density of the negative electrode sheet is greater than or equal to 12.5 mg / cm 3 .

[0021] The negative electrode sheet as described above, wherein the surface density of the first functional layer is greater than the surface density of the second functional layer.

[0022] The negative electrode sheet as described above, wherein the ratio of the areal density of the first functional layer to the areal density of the second functional layer is (1.005-1.2):1.

[0023] The present invention also provides a battery, comprising the negative electrode sheet as described above.

[0024] The negative electrode sheet of the present invention has functional layers disposed on both the first and second functional surfaces of the negative electrode current collector. The first functional layer on the first functional surface includes a second negative electrode active layer along a direction away from the negative electrode current collector, and the second functional layer on the second functional surface includes a third negative electrode active layer. The particle size of the second negative electrode active material is smaller than that of the first negative electrode active material, and / or the particle size of the second negative electrode active material is smaller than that of the third negative electrode active material. In the present invention, the particle size of the second negative electrode active material near the surface of the negative electrode sheet is smaller than that of the third negative electrode active material and the particle size of the first negative electrode active material, respectively. This facilitates rapid lithium deintercalation from the surface of the negative electrode sheet, preventing battery expansion during high-rate charging and improving the battery's cycle performance.

[0025] The battery of the present invention, because it includes the above-mentioned negative electrode sheet, has both excellent cycle expansion performance and cycle performance, and is suitable for wide application and promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the following briefly introduces the drawings required for use in the embodiments of the present invention or related technologies. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0027] Figure 1 Schematic diagram of the structure of the negative electrode sheet in some embodiments of the present invention.

[0028] Description of reference numerals:

[0029] 1: first negative electrode active layer;

[0030] 2: second negative electrode active layer;

[0031] 3: third negative electrode active layer;

[0032] 4: Negative electrode current collector. DETAILED DESCRIPTION

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0034] Figure 1 Schematic diagram of the structure of the negative electrode sheet of some embodiments of the present invention. Figure 1 As shown, the present invention provides a negative electrode sheet, which includes a negative electrode current collector 4, a first functional layer provided on a first functional surface of the negative electrode current collector 4, and a second functional layer provided on a second functional surface of the negative electrode current collector 4;

[0035] In the thickness direction of the negative electrode sheet, the first functional layer includes a first negative electrode active layer 1 and a second negative electrode active layer 2 stacked in a direction away from the negative electrode current collector, and the first negative electrode active layer 1 is close to the first functional surface; the second functional layer includes a third negative electrode active layer 3;

[0036] The first negative electrode active layer 1 includes a first negative electrode active material, the second negative electrode active layer 2 includes a second negative electrode active material, and the third negative electrode active layer 3 includes a third negative electrode active material;

[0037] The particle size of the second negative electrode active material is smaller than that of the first negative electrode active material; and / or the particle size of the second negative electrode active material is smaller than that of the third negative electrode active material.

[0038] In the present invention, the two surfaces of the negative electrode current collector 4 that have the largest area and are arranged opposite to each other are respectively the first functional surface and the second functional surface of the negative electrode current collector 4 .

[0039] The present invention does not impose any particular limitation on the negative electrode current collector 4; any commonly used negative electrode current collector 4 in the art may be selected. For example, the negative electrode current collector 4 may be copper foil. In some embodiments, a carbon layer may be provided on both surfaces of the copper foil to form the negative electrode current collector 4, with the combined thickness of the carbon layers on both sides of the copper foil being 1-1.5 μm.

[0040] It can be understood that the negative electrode sheet of the present invention includes the second negative electrode active layer 2, the first negative electrode active layer 1, the negative electrode current collector 4 and the third negative electrode active layer 3 in the stacking direction, or the negative electrode sheet of the present invention includes the third negative electrode active layer 3, the negative electrode current collector 4, the first negative electrode active layer 1 and the second negative electrode active layer 2 in the stacking direction.

[0041] In the present invention, the particle size of the first negative electrode active material refers to the average particle size of the first negative electrode active material, the particle size of the second negative electrode active material refers to the average particle size of the second negative electrode active material, and the particle size of the third negative electrode active material refers to the average particle size of the third negative electrode active material.

[0042] The first negative electrode active material, the second negative electrode active material and the third negative electrode active material of the present invention can all be selected from negative electrode active materials commonly used in the art. For example, the first negative electrode active material, the second negative electrode active material and the third negative electrode active material are independently selected from graphite and / or silicon.

[0043] It is understood that the first negative electrode active layer 1 of the present invention may further include a first binder and a first conductive agent, the second negative electrode active layer 2 may further include a second binder and a second conductive agent, and the third negative electrode active layer 3 may further include a third binder and a third conductive agent. The first binder, the second binder, and the third binder are independently selected from binders commonly used in the art, and the first conductive agent, the second conductive agent, and the third conductive agent are independently selected from conductive agents commonly used in the art.

[0044] In the present invention, the particle size of the second negative electrode active material on the surface of the negative electrode sheet is smaller than the particle size of the third negative electrode active material and the particle size of the first negative electrode active material, which helps to quickly deintercalate lithium from the surface of the negative electrode sheet, not only preventing the battery from expanding during high-rate charging, but also improving the cycle performance of the battery.

[0045] Taking wound batteries as an example, the winding direction can be controlled according to the degree of lithium deposition at different positions of the wound battery cell, so that the first functional layer is close to the area with severe lithium deposition in the wound battery cell, so as to promote the rapid deintercalation of lithium ions in this area and improve the battery's cycle performance and cycle expansion performance.

[0046] In some embodiments of the present invention, the particle size of the first negative electrode active material is larger than the particle size of the third negative electrode active material.

[0047] It can be understood that in the present invention, the particle sizes of the second negative electrode active material, the third negative electrode active material, and the first negative electrode active material increase in order. Since both the first and second negative electrode active materials are disposed on the first functional surface, the particle size of the second negative electrode active material is minimized, while the particle size of the first negative electrode active material is maximized. This balances the cyclic expansion performance, energy density, and cycling performance of the first functional layer. The particle size of the third negative electrode active material, disposed solely on the second functional surface, lies between the particle sizes of the first and second negative electrode active materials. This allows the third negative electrode active layer to achieve a combination of superior cyclic expansion performance, energy density, and cycling performance, contributing to improved overall battery performance.

[0048] In some embodiments of the present invention, D501 of the first negative electrode active material and D502 of the second negative electrode active material satisfy the following relationship:

[0049] 1.5≤D501 / D502≤5.5.

[0050] In the present invention, D50 refers to the particle size of the material that accounts for 50% of the volume of the material. For example, D501 of the first negative electrode active material refers to the particle size of the first negative electrode active material that accounts for 50% of the volume of the first negative electrode active material.

[0051] In the present invention, when D501 of the first negative electrode active material and D502 of the second negative electrode active material satisfy the above relationship, it helps to make the battery have excellent cycle expansion performance, cycle performance and energy density.

[0052] Further, D501 is 15-20 μm; and / or,

[0053] D502 is 3 to 10 μm; and / or

[0054] When D503 of the third negative electrode active material is 10-15 μm, the battery has better cycle expansion performance, cycle performance and energy density.

[0055] In some embodiments of the present invention, the compaction density of the first negative electrode active material is greater than the compaction density of the second negative electrode active material; and / or,

[0056] The fast charging capability of the second negative electrode active material is greater than the fast charging capability of the first negative electrode active material.

[0057] In the present invention, the compaction density of the first negative electrode active material near the negative electrode current collector is greater than that of the second negative electrode active material, which helps alleviate the pressure caused by the compaction of the negative electrode sheet and can ensure the energy density of the negative electrode sheet. The fast charging capability of the second negative electrode active material near the outer side of the negative electrode sheet is greater than that of the second negative electrode active material, which helps promote the rapid insertion and extraction of lithium ions on the surface of the negative electrode sheet, thereby improving the cycle performance and cycle expansion performance of the lithium-ion battery.

[0058] In some embodiments, the first negative electrode active material is high-density graphite to ensure that the compaction density of the first negative electrode active material is greater than the compaction density of the second negative electrode active material; the second negative electrode active material is graphite with a surface coating to ensure that the fast charging capability of the second negative electrode active material is greater than the fast charging capability of the first negative electrode active material. It will be understood that in some embodiments, the compaction density refers to the ultimate compaction density.

[0059] Furthermore, when the compaction density of the first negative electrode active material is greater than or equal to 1.8 g / cm 3 and / or,

[0060] When the charge rate of the second negative electrode active material is greater than or equal to 3C, the battery has better energy density, cycle performance and cycle expansion performance.

[0061] The charge rate of the second negative electrode active material is greater than or equal to 3C, which can be understood as the second negative electrode active material will not release lithium at a charge rate greater than or equal to 3C.

[0062] In some embodiments of the present invention, the total surface density of the negative electrode sheet is greater than or equal to 12.5 mg / cm 3 .

[0063] In the present invention, the total surface density of the negative electrode sheet refers to the sum of the surface density of the first functional layer and the surface density of the second functional layer, that is, the sum of the surface density of the first negative electrode active layer 1, the surface density of the second negative electrode active layer 2 and the surface density of the third negative electrode active layer 3.

[0064] The negative electrode sheet of the present invention has a total surface density greater than or equal to 12.5 mg / cm 3 The negative electrode sheet not only has a better energy density, but also has excellent cycle expansion performance and cycle performance under high rate charge and discharge conditions.

[0065] In some embodiments of the present invention, the areal density of the first functional layer is greater than the areal density of the second functional layer.

[0066] In the present invention, the areal density of the first functional layer refers to the sum of the areal density of the first negative electrode active layer 1 and the areal density of the second negative electrode active layer 2 , and the areal density of the second functional layer refers to the areal density of the third negative electrode active layer 3 .

[0067] The surface density of the first functional layer is greater than that of the second functional layer. When preparing a battery with a wound structure, the second functional layer is arranged on the inner side of the wound battery cell, and the first functional layer is arranged on the outer side of the wound battery cell. Since the second functional layer with a lower density is arranged on the inner side of the wound battery cell, wrinkles are not easy to occur during winding. This not only simplifies the winding process and improves the product yield, but also further alleviates the problem of lithium plating at the wrinkles and improves the cycle performance of the electrode.

[0068] Furthermore, in order to improve the cycle performance, cycle expansion performance and energy density of the battery, the ratio of the surface density of the first functional layer to the surface density of the second functional layer is (1.005-1.2):1. In a specific embodiment, the surface density of the first functional layer can be 13 mg / cm 3 The surface density of the second functional layer can be 12 mg / cm 3 , and the ratio of the surface density of the second functional layer is 1.08.

[0069] A second aspect of the present invention provides a battery, comprising the above-mentioned negative electrode sheet.

[0070] Since the battery of the present invention includes the above-mentioned negative electrode sheet, it has excellent cycle performance, cycle expansion performance and energy density.

[0071] The technical solutions of the present invention are further illustrated below with reference to specific examples. All parts, percentages, and ratios described in the following examples are based on weight. All reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further treatment. The instruments used in the examples are also commercially available.

[0072] Example 1

[0073] The lithium ion battery of this embodiment is prepared by the following steps:

[0074] 1) Positive electrode

[0075] The positive electrode active slurry is placed on two functional surfaces of the aluminum foil using an extrusion coater and then dried to obtain a positive electrode sheet containing a positive electrode active layer;

[0076] The mass ratio of the components in the positive electrode active layer is: LCO:PVDF:conductive agent (carbon black)=97%:1.5%:1.5%.

[0077] 2) Negative electrode

[0078] A. Using a gravure coater, a carbon layer is formed on the surface of a copper foil to obtain a negative electrode current collector; wherein the thickness of the copper foil is 5 μm, and the sum of the thickness of the carbon layers on both sides of the copper foil is 1.5 μm;

[0079] B. applying the first negative electrode active slurry to the first functional surface of the negative electrode current collector using an extrusion coater, and drying the first functional surface of the negative electrode current collector to form a first negative electrode active layer;

[0080] The first negative electrode active layer includes a first graphite, a binder of SBR, CMC, and a conductive agent of super P. The mass ratio of the first graphite, the binder, the CMC, and the conductive agent is 96.5%:1.5%:1.5%:0.5%. The solid content of the first negative electrode active slurry is 45.8%, the viscosity is 4568 mPa.s, the D501 of the first graphite is 17.3 μm, and the surface density of the first negative electrode active layer is 6.25 mg / cm 3 The ultimate compaction density of the first graphite is 1.85g / cc, and the first graphite can support 1.5C rate charging without lithium deposition;

[0081] C. Using an extrusion coater, place the second negative electrode active slurry on the surface of the first negative electrode active layer away from the negative electrode current collector, and dry it on the surface of the first negative electrode active layer to form a second negative electrode active layer;

[0082] The second negative electrode active layer includes a second graphite, a binder SBR, CMC, and a conductive agent superP. The mass ratio of the second graphite, the binder, the CMC, and the conductive agent is 96.5%:1.5%:1.5%:0.5%. The solid content of the second negative electrode active slurry is 44.3%, the viscosity is 4320 mPa.s, the D502 of the second graphite is 8 μm, and the surface density of the second negative electrode active layer is 6.25 mg / cm 3 The ultimate compaction density of the second graphite is 1.7g / cc, and the second graphite can support charging above 8C without lithium deposition;

[0083] D. applying the third negative electrode active slurry to the second functional surface of the negative electrode current collector using an extrusion coater, and drying to obtain a negative electrode sheet including the third negative electrode active layer;

[0084] The third negative electrode active layer includes a third graphite, a binder SBR, a CMC, and a conductive agent superP. The mass ratio of the third graphite, the binder, the CMC, and the conductive agent is 96.5%:1.5%:1.5%:0.5%. The solid content of the third negative electrode active slurry is 46.7%, the viscosity is 4768 mPa.s, the D503 of the third graphite is 13.2 μm, and the surface density of the third negative electrode active layer is 12.5 mg / cm 3The ultimate compaction density of the third graphite is 1.78g / cc, and the third graphite can support 3C rate charging without lithium deposition;

[0085] 3) Lithium-ion batteries

[0086] The positive electrode sheet of step 1), the negative electrode sheet of step 2) and the separator are wound into a core, with the third negative electrode active layer close to the center of the core, the core is placed in an outer package, the electrolyte is injected, and the battery is formed, repackaged (ensuring that the residual liquid coefficient is above 1.3), and divided into different volumes to obtain a lithium-ion battery;

[0087] Among them, the diaphragm includes a stacked ceramic layer, a PVDF coating layer, a polypropylene base film, a PVDF coating layer and a ceramic layer. The thickness of the diaphragm is 9μm, the thickness of the polypropylene base film is 5μm, the thickness of the two ceramic layers is 2μm in total, and the thickness of the two coating layers is 2μm in total.

[0088] Example 2

[0089] The preparation method of the lithium ion battery of this embodiment is basically the same as that of Example 1, except that:

[0090] The surface density of the first negative electrode active layer is 6.5 mg / cm 3 The surface density of the second negative electrode active layer is 6.5 mg / cm 3 The surface density of the third negative electrode active layer is 12 mg / cm 3 .

[0091] Example 3

[0092] The preparation method of the lithium ion battery of this embodiment is basically the same as that of Example 1, except that:

[0093] The surface density of the first negative electrode active layer is 6.75 mg / cm 3 The surface density of the second negative electrode active layer is 6.75 mg / cm 3 The surface density of the third negative electrode active layer is 11.5 mg / cm 3 .

[0094] Example 4

[0095] The preparation method of the lithium ion battery of this embodiment is basically the same as that of Example 1, except that:

[0096] The surface density of the first negative electrode active layer is 7 mg / cm 3 The surface density of the second negative electrode active layer is 7 mg / cm 3 The surface density of the third negative electrode active layer is 11 mg / cm 3 .

[0097] Example 5

[0098] The preparation method of the lithium ion battery of this embodiment is basically the same as that of Example 1, except that:

[0099] The surface density of the first negative electrode active layer is 6.5 mg / cm 3 ;

[0100] The surface density of the second negative electrode active layer is 6.5 mg / cm 3 , the particle size of the second negative electrode active material is 4 μm;

[0101] The surface density of the third negative electrode active layer is 12 mg / cm 3 .

[0102] Example 6

[0103] The preparation method of the lithium ion battery of this embodiment is basically the same as that of Example 1, except that:

[0104] The D501 of the first negative electrode active material was 23 μm; the D502 of the second negative electrode active material was 13 μm; and the D503 of the third negative electrode active material was 18 μm.

[0105] Example 7

[0106] The preparation method of the lithium ion battery of this embodiment is basically the same as that of Example 1, except that:

[0107] The D502 of the second negative electrode active material is 2.5 μm, that is, D501 / D502=17.3 / 2.5=6.92.

[0108] Example 8

[0109] The preparation method of the lithium ion battery of this embodiment is basically the same as that of Example 1, except that:

[0110] D501 of the first negative electrode active material is 11 μm, that is, D501 / D502=11 / 8=1.375.

[0111] Comparative Example 1

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

[0113] The second negative electrode active slurry in step 2) is respectively placed on the two functional surfaces of the negative electrode current collector, and dried to form a negative electrode sheet including a negative electrode active layer;

[0114] The surface density of the negative electrode active layer on any functional surface is 12.5 mg / cm 3 .

[0115] Comparative Example 2

[0116] The preparation method of the lithium ion battery of this comparative example is basically the same as that of Example 1, except that:

[0117] The first negative electrode active slurry in step 2) is respectively placed on the two functional surfaces of the negative electrode current collector, and dried to form a negative electrode sheet including a negative electrode active layer;

[0118] The surface density of the negative electrode active layer on any functional surface is 12.5 mg / cm 3 .

[0119] Comparative Example 3

[0120] The preparation method of the lithium ion battery of this comparative example is basically the same as that of Example 1, except that:

[0121] The third negative electrode active slurry in step 2) is respectively placed on the two functional surfaces of the negative electrode current collector, and dried to form a negative electrode sheet including a negative electrode active layer;

[0122] The surface density of the negative electrode active layer on any functional surface is 12.5 mg / cm 3 .

[0123] Comparative Example 4

[0124] The preparation method of the lithium ion battery of this comparative example is basically the same as that of Example 1, except that:

[0125] The second negative electrode active slurry in step 2) is placed on two functional surfaces of the negative electrode current collector, and dried to form a first negative electrode active layer on the two functional surfaces of the negative electrode current collector;

[0126] Disposing the first negative electrode active slurry on the surface of the first negative electrode active layer away from the negative electrode current collector, and drying to form a negative electrode sheet including the second negative electrode active layer;

[0127] The surface density of the first negative electrode active layer and the second negative electrode active layer on any functional surface is 6.25 mg / cm 3 .

[0128] Performance Testing

[0129] The following tests were performed on the batteries of the embodiment and the comparative example. The test results are shown in Table 1:

[0130] 1) Energy density calculation

[0131] The capacity of the lithium-ion batteries of the embodiment of the present invention and the comparative example was tested using a sorting cabinet. The battery energy density was calculated using the formula: energy density = capacity * voltage platform / mass.

[0132] 2) Cyclic performance, cyclic expansion performance, and rate performance

[0133] Place the battery in a (25±3)℃ or (45±3)℃ environment and let it stand for 3 hours. When the battery cell reaches (25±3)℃ or (45±3)℃, charge the battery to 4.25V at 1C, then charge it to 4.48V at 0.7C, then charge it to a cutoff current of 0.05C at 4.48V, and then discharge it to 3V at 0.5C. Record the initial capacity Q0 and initial thickness h0. When the required number of cycles is reached or the capacity attenuation rate is less than 70% or the thickness exceeds the test requirement, use the previous discharge capacity as the battery capacity Q2, and simultaneously test the thickness h2 of the battery cell to calculate the capacity retention rate (%) and thickness expansion rate (%):

[0134] Capacity retention rate (%) = Q2 / Q0×100%

[0135] Thickness expansion rate (%) = h2 / h0×100%.

[0136] Table 1

[0137]

[0138] It can be seen from Table 1 that the lithium-ion battery prepared in the embodiment of the present invention has relatively excellent cycle performance, cycle expansion performance and energy density.

[0139] Each embodiment in this specification is described in a related manner. Similar parts between the embodiments can be referred to in conjunction with each other. Each embodiment focuses on the differences from other embodiments. The above are only 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 in the scope of protection of the present invention.

Claims

1. A negative electrode sheet, characterized in that: The negative electrode sheet comprises a negative electrode current collector, a first functional layer disposed on a first functional surface of the negative electrode current collector, and a second functional layer disposed on a second functional surface of the negative electrode current collector; the first functional layer and the second functional layer are disposed opposite each other; in the thickness direction of the negative electrode sheet, the first functional layer comprises a first negative electrode active layer and a second negative electrode active layer stacked in a direction away from the negative electrode current collector; the second functional layer comprises a third negative electrode active layer; The first negative electrode active layer includes a first negative electrode active material, the second negative electrode active layer includes a second negative electrode active material, and the third negative electrode active layer includes a third negative electrode active material; The particle size of the second negative electrode active material is smaller than that of the first negative electrode active material; the particle size of the second negative electrode active material is smaller than that of the third negative electrode active material; The particle size of the first negative electrode active material is greater than the particle size of the third negative electrode active material; The total surface density of the negative electrode sheet is greater than or equal to 12.5 mg / cm 3 ; The ratio of the surface density of the first functional layer to the surface density of the second functional layer is (1.005-1.2):

1.

2. The negative electrode sheet according to claim 1, characterized in that: The D501 of the first negative electrode active material and the D502 of the second negative electrode active material satisfy the following relationship: 1.5≤D501 / D502≤5.

5.

3. The negative electrode sheet according to claim 2, characterized in that: D501 is 15-20 μm; and / or D502 is 3~10μm; and / or, The D503 of the third negative electrode active material is 10-15 μm.

4. The negative electrode sheet according to claim 1, characterized in that: The compaction density of the first negative electrode active material is greater than the compaction density of the second negative electrode active material; and / or, The fast charging capability of the second negative electrode active material is greater than the fast charging capability of the first negative electrode active material.

5. The negative electrode sheet according to claim 1, characterized in that: The compaction density of the first negative electrode active material is greater than or equal to 1.8 g / cm 3 and / or, The charge rate of the second negative electrode active material is greater than or equal to 3C.

6. A battery, characterized in that: The negative electrode sheet comprises the negative electrode sheet according to any one of claims 1 to 5.

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