Negative pole piece, lithium ion battery and electronic equipment

Abstract

The invention relates to a negative pole piece, a lithium ion battery and electronic equipment, and relates to the technical field of lithium ion batteries. The negative pole piece comprises a negative current collector, the width change rate delta W1 of the pole piece when the battery is fully charged, the width change rate delta W2 of the pole piece when the battery is overcharged to 150%, and the tensile strength M of an elastic area of the negative current collector meet the following relation: M / delta W1 is more than or equal to 0.1 and less than or equal to 1.2; 0.1 < = M / [delta] W2 < = 0.8; 0.1 < = [delta] W1 / [delta] W2 < = 0.7. By controlling the relationship among the pole piece width change rate delta W1 when the negative pole piece is fully charged, the pole piece width change rate delta W2 when the negative pole piece is overcharged to 150% and the tensile strength M of the elastic area of the negative current collector, Y expansion of the negative pole piece can be controlled, and the problems of battery deformation and cycle expansion in the battery cycle process can be reduced; and the cycle life of the battery is prolonged.

Description

Technical Field

[0001] This disclosure relates to the field of lithium-ion battery technology, and more particularly to a negative electrode, a lithium-ion battery, and an electronic device. Background Technology

[0002] With the fast pace of life, people have increasingly higher demands for mobile phone charging speed and battery life. However, lithium-ion batteries experience significant capacity loss during fast charging. Silicon, as a negative electrode material, has a theoretical capacity of up to 4200 mAh / g, far exceeding that of graphite negative electrodes, and can significantly improve battery capacity. However, silicon undergoes significant volume expansion during charging and discharging, leading to structural damage to the electrode material and affecting the battery's cycle stability and cycle life. Summary of the Invention

[0003] To overcome the problems existing in related technologies, this disclosure provides a negative electrode sheet, a lithium-ion battery, and an electronic device.

[0004] According to a first aspect of the present disclosure, a negative electrode sheet is provided, the negative electrode sheet including a negative electrode current collector, the electrode sheet width change rate ΔW1 when the battery is fully charged, the electrode sheet width change rate ΔW2 when the battery is overcharged to 150%, and the tensile strength M of the elastic region of the negative electrode current collector, satisfying the following relationship:

[0005] 0.1≤M / ΔW1≤1.2;

[0006] 0.1≤M / ΔW2≤0.8;

[0007] 0.1≤ΔW1 / ΔW2≤0.7.

[0008] In some embodiments of this disclosure, the tensile strength of the negative electrode current collector is 0.3-1.3 GPa;

[0009] The tensile strength of the elastic region of the negative electrode current collector is 0.3-0.6 GPa.

[0010] In some embodiments of this disclosure, the width of the negative electrode sheet is 30-120 mm.

[0011] In some embodiments of this disclosure, the weight per unit area of ​​the negative electrode sheet is 40-100 mg / cm². 2 ;

[0012] The thickness of the cold-pressed negative electrode sheet is 0.02-0.05 mm.

[0013] In some embodiments of this disclosure, the negative electrode sheet further includes a first active material layer disposed on at least one side of the negative electrode current collector;

[0014] The first active material layer includes a first active material, the first active material includes a first effective component, the first effective component includes a first negative electrode active material; the first negative electrode active material includes carbon material and silicon-based material in a predetermined ratio.

[0015] In some embodiments of this disclosure, the preset ratio is 2.5-5.8:1.

[0016] In some embodiments of this disclosure, the carbon material includes at least one of graphite, hard carbon, soft carbon, and mesophase microspheres;

[0017] The silicon-based material includes at least one of pure silicon, silicon alloy, silicon-carbon composite material, and silicon-oxygen composite material.

[0018] In some embodiments of this disclosure, the first negative electrode active material further includes lithium titanate, and the mass ratio of the carbon material to the silicon-based material and the carbon material to the lithium titanate is 2.3-4.5:1.

[0019] In some embodiments of this disclosure, the first effective component further includes a first conductive agent and a first adhesive.

[0020] In some embodiments of this disclosure, the first adhesive includes at least one of sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyacrylic acid, polyacrylate, polyamide-imide, and polyvinyl alcohol;

[0021] The first conductive agent includes at least one of conductive carbon black, discrete carbon nanotubes, acetylene black, conductive graphite, and graphene.

[0022] In some embodiments of this disclosure, the negative electrode sheet further includes a second active material layer, which is disposed between the negative current collector and the first active material layer;

[0023] The second active material layer includes a second active material, and the second active material includes a second effective component;

[0024] The second effective component includes a high-temperature resistant material, which has a mass change of 0-0.5% under an inert atmosphere and at a temperature of 350-450°C.

[0025] In some embodiments of this disclosure, the percentage of the mass of each component of the second effective component relative to the total mass of the second effective component is as follows:

[0026]

[0027] In some embodiments of this disclosure, the second conductive agent includes carbon nanotubes, and the carbon nanotubes include at least one of single-walled carbon nanotubes and multi-walled carbon nanotubes.

[0028] The second adhesive includes at least one of polyvinyl alcohol, polyvinyl acetal, carboxymethyl cellulose, carboxymethyl cellulose salt, polyacrylic acid, polyacrylate, polyvinylidene fluoride, and sodium alginate;

[0029] The high-temperature resistant material includes at least one of polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride-chlorotrifluoroethylene copolymer, polyvinylidene fluoride-trichloroethylene copolymer, polymethyl methacrylate, polybutyl acrylate, polyacrylonitrile, and polyvinylpyrrolidone.

[0030] In some embodiments of this disclosure, the thickness of the first active material layer is 0.1-4.5 μm; and, or

[0031] The weight per unit area of ​​the first active material layer is 0.2-1.2 mg / m². 2 ;

[0032] The thickness of the second active material layer is 20.4-103.1 μm; and, or

[0033] The weight per unit area of ​​the second active substance layer is 40-100 mg / m². 2 .

[0034] In some embodiments of this disclosure, the negative electrode sheet further includes a high-temperature resistant layer, which is disposed between the negative electrode current collector and the first active material layer;

[0035] The weight W1 per unit area of ​​the high-temperature resistant layer and the weight W2 per unit area of ​​the negative electrode sheet satisfy the following relationship:

[0036] 50≤W2 / W1≤200.

[0037] In some embodiments of this disclosure, the weight W1 per unit area of ​​the high-temperature resistant layer is 0.5-2.5 mg / m². 2 ;

[0038] The weight W2 per unit area of ​​the negative electrode sheet is 40-140 mg / m². 2 .

[0039] In some embodiments of this disclosure, the high-temperature resistant layer includes a third conductive agent, the mass of which accounts for 5.2-10.8% of the total mass of the high-temperature resistant layer.

[0040] In some embodiments of this disclosure, the third conductive agent comprises a carbon nanotube cluster, wherein the carbon nanotube cluster comprises at least one of single-walled carbon nanotubes and multi-walled carbon nanotubes.

[0041] In some embodiments of this disclosure, when the carbon nanotube cluster comprises single-walled carbon nanotubes, the average diameter of the single-walled carbon nanotubes is 1-20 nm; and / or,

[0042] When the carbon nanotube cluster includes multi-walled carbon nanotubes, the average diameter of the multi-walled carbon nanotubes is 50-200 nm.

[0043] In some embodiments of this disclosure, the high-temperature resistant layer further includes inorganic fillers and a third adhesive, and the percentage of the mass of the inorganic fillers and the third adhesive relative to the total mass of the high-temperature resistant layer is expressed as follows:

[0044] Inorganic filler content: 51.5-72.5%;

[0045] The third adhesive is 20.3-41.4%.

[0046] In some embodiments of this disclosure, the inorganic filler includes at least one selected from boehmite, gibbsite, barium sulfate, calcium sulfate, calcium silicate, and magnesium hydroxide.

[0047] The third adhesive includes at least one of the following: copolymers of propylene derivatives, polyacrylic acid, polyacrylate, polyacrylic acid ester, polyacrylonitrile, carboxymethyl cellulose salt, nitrile rubber, polyvinylidene fluoride, polyhexafluoropropylene, polyvinylpyrrolidone, polyamide, polyvinyl ether, and polymethyl methacrylate.

[0048] According to a second aspect of the present disclosure, a lithium-ion battery is provided, comprising a negative electrode sheet as described above.

[0049] According to a third aspect of the present disclosure, an electronic device is provided, including a lithium-ion battery as described above.

[0050] The technical solutions provided by the embodiments of this disclosure may include the following beneficial effects:

[0051] This disclosure controls the Y-expansion of the negative electrode sheet by controlling the relationship between the electrode width change rate ΔW1 during full charge, the electrode width change rate ΔW2 during overcharge to 150%, and the tensile strength M of the elastic region of the negative electrode current collector. This helps reduce battery deformation and cycle expansion during battery cycling, thereby improving battery cycle life. Furthermore, controlling the Y-expansion of the negative electrode sheet can also improve the battery's energy density and kinetics, thus enhancing its range and charge / discharge speed.

[0052] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0053] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0054] Figure 1 This is a schematic diagram of the layer structure of a negative electrode sheet according to an exemplary embodiment.

[0055] Figure 2 This is a schematic diagram of the layer structure of a negative electrode sheet according to an exemplary embodiment.

[0056] Figure 3 This is a schematic diagram of the layer structure of a negative electrode sheet according to an exemplary embodiment.

[0057] Figure 4 This is a schematic diagram of the layer structure of a negative electrode sheet according to an exemplary embodiment. Detailed Implementation

[0058] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0059] While silicon materials can significantly increase battery capacity, they undergo significant volume expansion during charging and discharging, which damages the structure of the electrode materials and affects the battery's cycle stability and cycle life.

[0060] To address the aforementioned technical problems, this disclosure provides a negative electrode sheet, comprising a negative current collector, and the following relationships satisfying the following parameters: the electrode width change rate ΔW1 when the battery is fully charged, the electrode width change rate ΔW2 when the battery is overcharged to 150%, and the tensile strength M of the elastic region of the negative current collector. These relationships are: 0.1 ≤ M / ΔW1 ≤ 1.2; 0.1 ≤ M / ΔW2 ≤ 0.8; 0.1 ≤ ΔW1 / ΔW2 ≤ 0.7. By controlling the relationship between the electrode width change rate ΔW1 when fully charged, the electrode width change rate ΔW2 when overcharged to 150%, and the tensile strength M of the elastic region of the negative current collector, the Y-expansion of the negative electrode sheet can be controlled. This helps reduce battery deformation and cycle expansion during battery cycling, thereby improving the battery's cycle life. Furthermore, controlling the Y-expansion of the negative electrode sheet can also improve the battery's energy density and dynamics, thereby increasing the battery's range and charge / discharge speed.

[0061] like Figure 1As shown, an exemplary embodiment of this disclosure provides a negative electrode sheet, which includes a negative electrode current collector 1. The electrode sheet width change rate ΔW1 when the battery is fully charged, the electrode sheet width change rate ΔW2 when the battery is overcharged to 150%, and the tensile strength M of the elastic region of the negative electrode current collector 1 satisfy the following relationship:

[0062] 0.1≤M / ΔW1≤1.2;

[0063] 0.1≤M / ΔW2≤0.8;

[0064] 0.1≤ΔW1 / ΔW2≤0.7.

[0065] In this embodiment, by controlling the relationship between the electrode width change rate ΔW1 when the negative electrode is fully charged, the electrode width change rate ΔW2 when overcharged to 150%, and the tensile strength M of the elastic region of the negative electrode current collector 1, the Y-expansion (i.e., expansion in the Y-axis direction) of the negative electrode can be controlled. This helps reduce battery deformation and cycle expansion during battery cycling, thereby improving the battery's cycle life. Furthermore, controlling the Y-expansion of the negative electrode can also improve the battery's energy density and dynamics, thus enhancing its range and charge / discharge speed.

[0066] Here, "full charge" and "overcharge" refer to the battery's state of charge. The State of Charge (SOC) is an indicator of the battery's current remaining capacity. Typically, SOC is controlled between 0% (fully discharged) and 100% (fully charged). When SOC exceeds 100%, it indicates that the battery has been charged beyond its fully charged state. In this embodiment, ΔW1 represents the electrode width change rate at 100% SOC, and ΔW2 represents the electrode width change rate at 150% SOC.

[0067] The width of the electrode can be detected using a charge-coupled device (CCD). The width of the electrode after cold pressing is denoted as W', the width of the electrode after being fully charged and removed from the battery is denoted as W”, and the width of the electrode after being overcharged to 150% SOC and removed from the battery is denoted as W”’. The difference between W” and W' is denoted as the electrode width change rate ΔW1, and the difference between W”’ and W' is denoted as the electrode width change rate ΔW2.

[0068] The elastic zone of the negative electrode current collector 1 refers to the range within which the negative electrode current collector 1 can undergo elastic deformation without permanent deformation under external force. In this embodiment, the tensile strength of the elastic zone of the negative electrode current collector 1 refers to the tensile strength of the negative electrode current collector 1 corresponding to a displacement of 0.5 mm during a high-speed rail tensile test. The material of the negative electrode current collector 1 is not particularly limited and can be any known negative electrode current collector 1 in the art, such as copper foil or composite copper foil.

[0069] For example, in one embodiment, ΔW1, ΔW2, and M satisfy the following relationship:

[0070] M / ΔW1=1.2; M / ΔW2=0.6; ΔW1 / ΔW2=0.5.

[0071] In another embodiment, ΔW1, ΔW2, and M satisfy the following relationship:

[0072] M / ΔW1=1.2; M / ΔW2=0.8; ΔW1 / ΔW2=0.7.

[0073] In another embodiment, ΔW1, ΔW2, and M satisfy the following relationship:

[0074] M / ΔW1=1.0; M / ΔW2=0.7; ΔW1 / ΔW2=0.7.

[0075] In another embodiment, ΔW1, ΔW2, and M satisfy the following relationship:

[0076] M / ΔW1=1.0; M / ΔW2=0.3; ΔW1 / ΔW2=0.3.

[0077] In another embodiment, ΔW1, ΔW2, and M satisfy the following relationship:

[0078] M / ΔW1=1.0; M / ΔW2=0.1; ΔW1 / ΔW2=0.1.

[0079] In another embodiment, ΔW1, ΔW2, and M satisfy the following relationship:

[0080] M / ΔW1=0.5; M / ΔW2=0.3; ΔW1 / ΔW2=0.6.

[0081] In another embodiment, ΔW1, ΔW2, and M satisfy the following relationship:

[0082] M / ΔW1=0.2; M / ΔW2=0.1; ΔW1 / ΔW2=0.5.

[0083] In an exemplary embodiment, the tensile strength of the negative electrode current collector 1 is 0.3-1.3 GPa; the tensile strength of the elastic region of the negative electrode current collector 1 is 0.3-0.6 GPa.

[0084] In this embodiment, by controlling the tensile strength of the negative electrode current collector 1 and the tensile strength of the elastic region of the negative electrode current collector 1, the negative electrode current collector 1 can better resist the volume expansion caused by the silicon material during battery charging and discharging, thereby better resisting deformation and ensuring the integrity of the electrode structure. For example, the tensile strength of the negative electrode current collector 1 can be 0.3 GPa, 0.6 GPa, 1.0 GPa, or 1.3 GPa. The tensile strength value of the negative electrode current collector 1 can also be any value between the exemplary tensile strength values; for example, the tensile strength of the negative electrode current collector 1 can also be any value between 0.6 and 1.0 GPa. The tensile strength of the elastic region of the negative electrode current collector 1 is 0.3 GPa, 0.4 GPa, 0.5 GPa, or 0.6 GPa. The tensile strength of the elastic region of the negative electrode current collector 1 can also be any value between the exemplary tensile strength values; for example, the tensile strength of the elastic region of the negative electrode current collector 1 can also be any value between 0.4 and 0.5 GPa.

[0085] In one exemplary embodiment, the width of the negative electrode sheet is 30-120 mm.

[0086] Increasing the width of the negative electrode increases the distance the charge travels within the electrode, leading to increased internal resistance and impacting the battery's charge / discharge efficiency and rate performance. In this embodiment, controlling the width of the negative electrode within 30-120mm allows the battery to maintain optimal overall performance. For example, the width of the negative electrode can be 30mm, 50mm, 80mm, 100mm, or 120mm. The width can also be any value between these exemplary values; for instance, the width of the negative electrode can be any value between 50-100mm.

[0087] For example, the tensile strength M of the elastic region of the negative electrode current collector is 0.5 GPa; the width W' of the negative electrode sheet is 50 mm, and the electrode sheet width W”” when the battery is fully charged is 50.42 mm, then the electrode sheet width change rate ΔW1 when the battery is fully charged is 0.42; when the battery is overcharged to 150% SOC, the electrode sheet width W”” is 50.83 mm, and the electrode sheet width change rate ΔW2 when the battery is overcharged to 150% is 0.83; then, M / ΔW1=1.2, M / ΔW2=0.6, ΔW1 / ΔW2=0.5.

[0088] In one exemplary embodiment, the negative electrode sheet has a unit area weight of 40-100 mg / cm². 2 .

[0089] In this embodiment, by controlling the weight per unit area of ​​the negative electrode sheet, the battery can maintain better overall performance. For example, the weight per unit area of ​​the negative electrode sheet is 40 mg / cm². 260mg / cm 2 70mg / cm 2 90mg / cm 2 100mg / cm 2 The weight per unit area of ​​the negative electrode can also be any value between the exemplary weight per unit area ranges; for example, the weight per unit area of ​​the negative electrode can also be 60-90 mg / cm³. 2 Any value between.

[0090] In one exemplary embodiment, the thickness of the cold-pressed negative electrode sheet is 0.02-0.05 mm.

[0091] In this embodiment, by controlling the thickness of the cold-pressed negative electrode sheet, the battery can maintain better overall performance. For example, the thickness of the cold-pressed negative electrode sheet is 0.02 mm, 0.03 mm, 0.04 mm, or 0.05 mm. The width of the cold-pressed negative electrode sheet can also be any value between the exemplary width values; for example, the width of the cold-pressed negative electrode sheet can be any value between 0.03 and 0.04 mm.

[0092] like Figure 1 As shown, in an exemplary embodiment, the negative electrode sheet further includes a first active material layer 2 disposed on at least one side of the negative electrode current collector 1; the first active material layer 2 includes a first active material material, the first active material material includes a first effective component, the first effective component includes a first negative electrode active material; the first negative electrode active material includes a carbon material and a silicon-based material in a preset ratio.

[0093] Silicon-based materials have a much higher specific capacity than carbon materials. In this embodiment, by combining carbon materials with silicon-based materials, the energy density, cycle stability, charge and discharge efficiency, rate performance, and mechanical stability of the battery can be improved.

[0094] Among them, such as Figure 1 As shown, the first active material layer 2 can be disposed only on one side of the negative electrode current collector 1; it can be understood that, as Figure 2 As shown, the first active material layer 2 can also be disposed on both sides of the negative electrode current collector 1, which can be selected according to actual needs.

[0095] The first effective component contains the main functional ingredients. The first negative electrode active material can be applied to the negative electrode current collector 1 by roller coating or extrusion. To improve the uniformity of the coating of the first negative electrode active material, the first negative electrode active material may also include a first solvent. For example, the first solvent may be at least one of N-methylpyrrolidone (NMP), ethylene carbonate (EC), dimethyl carbonate (DMC), and dimethylacetamide (DMAc). The first effective component can be dissolved or dispersed by the first solvent, thus the first negative electrode active material can be made into a slurry for use. The first negative electrode active material is coated onto the negative electrode current collector 1 in the form of a slurry to form a uniform coating on the negative electrode current collector 1.

[0096] For example, the negative electrode sheet can be prepared by the following method: coating a first negative electrode active material onto both sides of the negative electrode current collector 1 to form a first active material layer 2; and cold pressing to form the negative electrode sheet. The cold pressing (rolling) temperature can be, for example, 20-30°C, and the rolling pressure can be 20-40T.

[0097] In one exemplary embodiment, the preset ratio is 2.5-5.8:1.

[0098] In this embodiment, by controlling the preset ratio between 2.5 and 5.8:1, the battery can maintain better overall performance. Exemplarily, the preset ratios are 2.5:1, 3.4:1, 4.7:1, and 5.8:1. The preset ratio can also be any value between the exemplary preset ratios; for example, the preset ratio can also be any value between 3.4 and 4.7:1.

[0099] In one exemplary embodiment, the carbon material includes at least one of graphite, hard carbon, soft carbon, and mesophase microspheres; the silicon-based material includes at least one of pure silicon, silicon alloy, silicon-carbon composite material, and silicon-oxygen composite material.

[0100] In this embodiment, the carbon material can be one of graphite, hard carbon, soft carbon, or mesophase microspheres, or a combination of several of them. For example, the carbon material may include graphite and hard carbon in a mass ratio of 1.2-3.5:1, or the carbon material may include graphite, hard carbon, and soft carbon in a mass ratio of 0.8-1.2:2.3-3.3:1. The silicon-based material can be one of pure silicon, silicon alloy, silicon-carbon composite material, or silicon-oxygen composite material, or a combination of several of them. For example, the silicon-based material may include pure silicon and silicon-carbon composite material in a mass ratio of 0.5-1.2:1, or the silicon-based material may include silicon in a mass ratio of 1.2-2.1:3.1-3.6:1.

[0101] In an exemplary embodiment, the first negative electrode active material further includes lithium titanate, and the mass ratio of carbon material to silicon-based material to lithium titanate is 2.3-4.5:1.

[0102] In this embodiment, the first negative electrode active material may further include lithium titanate, which can effectively improve the cycle stability and safety of the battery. Exemplarily, the mass ratio of the carbon material to the silicon-based material to lithium titanate is 2.3:1, 3.2:1, 3.8:1, 4.0:1, or 4.5:1. The mass ratio of the carbon material to the silicon-based material to lithium titanate can also be any value between the exemplary mass ratios; for example, the mass ratio of the carbon material to the silicon-based material to lithium titanate can also be any value between 3.2 and 4.0:1.

[0103] In one exemplary embodiment, the first effective component further includes a first conductive agent and a first adhesive.

[0104] In this embodiment, the first effective component may further include a first conductive agent and a first binder. The percentage of the first conductive agent by mass in the total mass of the first effective component may be, for example, 21.3-37.9%; the percentage of the first binder by mass in the total mass of the first effective component may be, for example, 12.4-18.8%; and the amount of the first negative electrode active material is the balance.

[0105] The first conductive agent can form a conductive network between the first negative electrode active material and the negative electrode current collector 1 to improve the conductivity of the negative electrode sheet. The first conductive agent includes at least one of conductive carbon black, discrete carbon nanotubes, acetylene black, conductive graphite, and graphene. For example, the first conductive agent may include one of conductive carbon black, discrete carbon nanotubes, acetylene black, conductive graphite, and graphene, or it may be a blend of several of conductive carbon black, Ketjen black, carbon nanotubes, and graphene. For example, the first conductive agent may include conductive carbon black and carbon nanotubes in a mass ratio of 1:1.5-3.4; or, the first conductive agent may include conductive carbon black, carbon nanotubes, and graphene in a mass ratio of 1:2.3-4.0:4.5-5.8.

[0106] The first adhesive is used to adhere the first negative electrode active material and the first conductive agent to the negative electrode current collector 1 to ensure the integrity of the negative electrode structure and to enhance the transmission efficiency between the first negative electrode active material, the first conductive agent, and the negative electrode current collector 1. Exemplarily, the first adhesive can be one of sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyacrylic acid, polyacrylate, polyamide-imide, and polyvinyl alcohol, where polyacrylate can be, for example, sodium polyacrylate. Alternatively, several of these can be compounded. For example, the first adhesive may include sodium carboxymethyl cellulose and polyacrylic acid in a mass ratio of 1:1.2-3.6, or the first adhesive may include sodium carboxymethyl cellulose, polyacrylic acid, and polyvinyl alcohol in a mass ratio of 1:1.4-2.4:2.5-4.5.

[0107] like Figure 3As shown, in an exemplary embodiment, the negative electrode sheet further includes a second active material layer 3, which is disposed between the negative current collector 1 and the first active material layer 2.

[0108] The second active material layer 3 includes a second active material, which includes a second effective component; the second effective component includes a high-temperature resistant material, and the mass change of the high-temperature resistant material is 0-0.5% under an inert atmosphere and at a temperature of 350-450°C.

[0109] In this embodiment, by providing a second active material layer 3 on the negative electrode sheet, and by including a high-temperature resistant material in the second active material layer 3, the battery's temperature resistance can be improved when thermal runaway occurs, thereby enhancing the battery's safety performance. Furthermore, by providing two active material layers, the amount of active material in the negative electrode sheet can be increased, which is beneficial for improving the battery's energy density and enhancing its kinetic and rate performance.

[0110] To improve the uniformity of the coating of the second negative electrode active material, the second negative electrode active material may further include a second solvent. For example, the second solvent may be at least one of N-methylpyrrolidone (NMP), ethylene carbonate (EC), dimethyl carbonate (DMC), and dimethylacetamide (DMAc). The second solvent can dissolve or disperse the second active component, thus allowing the second electrode active material to be prepared into a slurry for use. The second negative electrode active material is coated onto the negative electrode current collector 1 in the form of a slurry, thereby forming a uniform coating on the negative electrode current collector 1.

[0111] In one exemplary embodiment, the percentage of the mass of each component of the second effective component relative to the total mass of the second effective component is as follows:

[0112]

[0113] In this embodiment, by controlling the mass ratio of each component in the second effective component, the battery can maintain better overall performance.

[0114] For example, in one embodiment, the percentage of the mass of each component in the second effective component relative to the total mass of the second effective component is as follows:

[0115]

[0116]

[0117] In another embodiment, the percentage of each component's mass in the second effective component relative to the total mass of the second effective component is as follows:

[0118]

[0119] In another embodiment, the percentage of each component's mass in the second effective component relative to the total mass of the second effective component is as follows:

[0120]

[0121] In another embodiment, the percentage of each component's mass in the second effective component relative to the total mass of the second effective component is as follows:

[0122]

[0123] In another embodiment, the percentage of each component's mass in the second effective component relative to the total mass of the second effective component is as follows:

[0124]

[0125] In one exemplary embodiment, the second conductive agent includes carbon nanotubes, which include at least one of single-walled carbon nanotubes and multi-walled carbon nanotubes.

[0126] In this embodiment, the second conductive agent can be carbon nanotubes. Carbon nanotubes possess high conductivity, a large specific surface area, and excellent mechanical properties, which can improve the electron transport efficiency of the electrode and enhance the charge-discharge performance and rate performance of the battery. Furthermore, carbon nanotubes also exhibit good thermal conductivity, which helps in thermal management during battery charging and discharging, improving the battery's thermal stability. The carbon nanotubes can be single-walled or multi-walled carbon nanotubes, or a mixture of single-walled and multi-walled carbon nanotubes at a mass ratio of 0.8-2.3:1.

[0127] In one exemplary embodiment, the second adhesive includes at least one selected from polyvinyl alcohol, polyvinyl acetal, carboxymethyl cellulose, carboxymethyl cellulose salt, polyacrylic acid, polyacrylate, polyvinylidene fluoride, and sodium alginate.

[0128] In this embodiment, the second adhesive can be selected from one of polyvinyl alcohol, polyvinyl acetal, carboxymethyl cellulose, carboxymethyl cellulose salt, polyacrylic acid, polyacrylate, polyvinylidene fluoride, and sodium alginate, or several of them can be selected and compounded. For example, the second adhesive includes polyvinyl alcohol and carboxymethyl cellulose in a mass ratio of 1.2-2.5:1, or the second adhesive includes polyvinyl alcohol in a mass ratio of 0.8-1.5:1.8-2.7:1.

[0129] In one exemplary embodiment, the high-temperature resistant material includes at least one of polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride-chlorotrifluoroethylene copolymer, polyvinylidene fluoride-trichloroethylene copolymer, polymethyl methacrylate, polybutyl acrylate, polyacrylonitrile, and polyvinylpyrrolidone.

[0130] In this embodiment, the high-temperature resistant material can be selected from one of the following: polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride-chlorotrifluoroethylene copolymer, polyvinylidene fluoride-trichloroethylene copolymer, polymethyl methacrylate, polybutyl acrylate, polyacrylonitrile, and polyvinylpyrrolidone. Alternatively, several of these materials can be selected and compounded. For example, the high-temperature resistant material can be selected from polyvinylidene fluoride-hexafluoropropylene copolymer and polymethyl methacrylate in a mass ratio of 2.1-3.7:1. Alternatively, the high-temperature resistant material can be selected from polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride-chlorotrifluoroethylene copolymer, and polymethyl methacrylate in a mass ratio of 1.2-1.8:0.5-1.0:1.

[0131] In one exemplary embodiment, the thickness of the first active material layer is 0.1-4.5 μm. Exemplarily, the thickness of the first active material layer is 0.1 μm, 1.3 μm, 2.5 μm, 3.7 μm, or 4.5 μm. The thickness of the first active material layer can also be any value between the exemplary thickness values; for example, the thickness of the first active material layer can also be any value between 1.3 and 3.7 μm.

[0132] In an exemplary embodiment, the weight per unit area of ​​the first active material layer is 0.2-1.2 mg / m². 2 For example, the weight per unit area of ​​the first active material layer is 0.2 mg / m². 2 0.5mg / m 2 0.8 mg / m 2 1.0 mg / m 2 1.2 mg / m 2 The weight per unit area of ​​the first active substance layer can also be any value between the exemplary weight values, for example, the weight per unit area of ​​the first active substance layer is 0.5-1.0 mg / m². 2 Any value between.

[0133] In one exemplary embodiment, the thickness of the second active material layer is 20.4-103.1 μm. Exemplarily, the thickness of the second active material layer is 20.4 μm, 41.3 μm, 73.7 μm, 95.4 μm, or 103.1 μm. The thickness of the second active material layer can also be any value between the exemplary thickness values; for example, the thickness of the second active material layer can also be any value between 41.3 and 73.7 μm.

[0134] In one exemplary embodiment, the weight per unit area of ​​the second active material layer is 40-100 mg / m². 2 For example, the weight per unit area of ​​the second active material layer is 40 mg / m². 2 55mg / m 275mg / m 2 84mg / m 2 100mg / m 2 The weight per unit area of ​​the second active substance layer can also be any value between the exemplary weight values, for example, the weight per unit area of ​​the second active substance layer is 55-84 mg / m². 2 Any value between.

[0135] like Figure 4 As shown, in an exemplary embodiment, the negative electrode sheet further includes a high-temperature resistant layer 4, which is disposed between the negative electrode current collector 1 and the first active material layer 2.

[0136] The weight per unit area W1 of the high-temperature resistant layer 4 and the weight per unit area W2 of the negative electrode sheet satisfy the following relationship:

[0137] 50≤W2 / W1≤200.

[0138] In this embodiment, the high-temperature resistant layer 4 protects the negative electrode at high temperatures, preventing short circuits caused by contact between the negative and positive electrodes, thus improving battery safety. Furthermore, the high-temperature resistant layer 4 allows the battery to achieve both good energy density and battery safety. For example, the ratio of the weight per unit area W2 of the negative electrode sheet to the weight per unit area W1 of the high-temperature resistant layer 4 can be 50, 130, 160, 180, or 200. The W2 / W1 ratio can also be any value between these exemplary ratios; for example, the W2 / W1 ratio can be any value between 130 and 180:1.

[0139] In an exemplary embodiment, the weight W1 per unit area of ​​the high-temperature resistant layer 4 is 0.5-2.5 mg / m². 2 The weight per unit area (W2) of the negative electrode sheet is 40-140 mg / m². 2 .

[0140] In this embodiment, by controlling the weight per unit area of ​​the high-temperature resistant layer 4 and the weight per unit area of ​​the negative electrode sheet, the battery can maintain better overall performance. For example, the weight W1 per unit area of ​​the high-temperature resistant layer 4 can be 0.5 mg / m². 2 1.0 mg / m 2 1.6 mg / m 2 2.1 mg / m 2 2.5mg / m 2 The weight per unit area (W2) of the negative electrode is 40 mg / m². 2 65mg / m 2 84mg / m 2 102mg / m 2 124mg / m2 140mg / m 2 The weight per unit area W1 of the high-temperature resistant layer 4 and the weight per unit area W2 of the negative electrode sheet can also be any value between the exemplary weight values. For example, the weight per unit area W1 of the high-temperature resistant layer 4 can also be 1.0-2.1 mg / m². 2 The weight per unit area W2 of the negative electrode sheet can also be 84-124 mg / m². 2 .

[0141] In an exemplary embodiment, the high-temperature resistant layer 4 includes a third conductive agent, the mass of which accounts for 5.2-10.8% of the total mass of the high-temperature resistant layer 4.

[0142] In this embodiment, the high-temperature resistant layer 4 further includes a third conductive agent. The addition of the third conductive agent can improve the electron transport efficiency of the electrode and enhance the charge / discharge performance and rate performance of the battery. Exemplarily, the mass of the third conductive agent accounts for 5.2%, 7.3%, 8.9%, 9.6%, and 10.8% of the total mass of the high-temperature resistant layer 4. The mass ratio of the third conductive agent to the total mass of the high-temperature resistant layer 4 can also be any value between the exemplary mass ratios; for example, the mass of the third conductive agent accounts for 7.3-9.6% of the total mass of the high-temperature resistant layer 4.

[0143] In one exemplary embodiment, the third conductive agent includes a carbon nanotube cluster, which includes at least one of single-walled carbon nanotubes and multi-walled carbon nanotubes.

[0144] In this embodiment, single-walled carbon nanotubes possess excellent electrical and thermal conductivity, which enhances the charge-discharge performance and thermal management of the battery in its role as a negative electrode material. Multi-walled carbon nanotubes, composed of multiple concentric carbon nanotube layers, typically have a larger diameter, resulting in superior thermal stability and mechanical strength. The third conductive agent can be either single-walled or multi-walled carbon nanotubes, or a mixture of single-walled and multi-walled carbon nanotubes in a mass ratio of 1.1-2.8:1.

[0145] In one exemplary embodiment, when the carbon nanotube cluster comprises single-walled carbon nanotubes, the average diameter of the single-walled carbon nanotubes is 1-20 nm; and / or,

[0146] When carbon nanotube clusters include multi-walled carbon nanotubes, the average diameter of the multi-walled carbon nanotubes is 50-200 nm.

[0147] In this embodiment, the average diameter of single-walled carbon nanotubes can be, for example, 1 nm, 5 nm, 10 nm, or 20 nm; the average diameter of multi-walled carbon nanotubes can be, for example, 50 nm, 90 nm, 130 nm, 160 nm, or 200 nm. The average length of the multi-walled carbon nanotubes can be, for example, 0.5-3 μm.

[0148] In one exemplary embodiment, the high-temperature resistant layer 4 further includes inorganic fillers and a third adhesive, the percentage of the mass of the inorganic fillers and the third adhesive relative to the total mass of the high-temperature resistant layer 4 being expressed as follows:

[0149] Inorganic filler content: 51.5-72.5%;

[0150] The third adhesive is 20.3-41.4%.

[0151] The addition of inorganic fillers can improve battery safety, electrochemical performance, and structural stability. A third binder is used to adhere the inorganic filler and the third conductive agent to the negative electrode current collector 1 to ensure the integrity of the negative electrode structure. In this embodiment, by controlling the amount of each component, the battery can maintain optimal overall performance.

[0152] For example, in one embodiment, the percentage of the mass of each component of the high-temperature resistant layer 4 to the total mass of the high-temperature resistant layer 4 is expressed as follows:

[0153] Inorganic filler content: 51.5%;

[0154] Third adhesive 41.4%;

[0155] The third conductive agent is 7.1%.

[0156] In another embodiment, the percentage of the mass of each component of the high-temperature resistant layer 4 to the total mass of the high-temperature resistant layer 4 is expressed as follows:

[0157] Inorganic filler content: 72.5%;

[0158] Third adhesive 20.3%;

[0159] The third conductive agent is 7.2%.

[0160] In another embodiment, the percentage of the mass of each component of the high-temperature resistant layer 4 to the total mass of the high-temperature resistant layer 4 is expressed as follows:

[0161] Inorganic filler content: 62.5%;

[0162] The third adhesive is 32.3%;

[0163] The third conductive agent is 5.2%.

[0164] In another embodiment, the percentage of the mass of each component of the high-temperature resistant layer 4 to the total mass of the high-temperature resistant layer 4 is expressed as follows:

[0165] Inorganic filler content: 65.0%;

[0166] Third adhesive 24.2%;

[0167] The third conductive agent is 10.8%.

[0168] In an exemplary embodiment, the inorganic filler includes at least one selected from boehmite, gibbsite, barium sulfate, calcium sulfate, calcium silicate, and magnesium hydroxide.

[0169] In this embodiment, the inorganic filler can be selected from one of boehmite, gibbsite, barium sulfate, calcium sulfate, calcium silicate, and magnesium hydroxide, or several of them can be selected and compounded. For example, the inorganic filler includes boehmite and gibbsite in a mass ratio of 1.3-3.4:1; or the inorganic filler includes barium sulfate, boehmite, and calcium silicate in a mass ratio of 1:2.3-4.3:4.7-5.6.

[0170] In one exemplary embodiment, the third adhesive includes at least one of the following: copolymer of propylene derivatives, polyacrylic acid, polyacrylate, polyacrylic acid ester, polyacrylonitrile, carboxymethyl cellulose salt, nitrile rubber, polyvinylidene fluoride, polyhexafluoropropylene, polyvinylpyrrolidone, polyamide, polyvinyl ether, and polymethyl methacrylate.

[0171] In this embodiment, the copolymer of propylene derivatives is a copolymer of propylene monomers and other monomers (such as ethylene, acrylic acid, and acrylonitrile). For example, the copolymer of propylene derivatives can be propylene-ethylene copolymer, propylene-acrylic acid copolymer, acrylate copolymer, etc.; polyacrylate can be sodium polyacrylate for example; carboxymethyl cellulose salt can be sodium carboxymethyl cellulose for example.

[0172] The third adhesive can be selected from one of the following: copolymers of propylene derivatives, polyacrylic acid, polyacrylate, polyacrylic acid ester, polyacrylonitrile, carboxymethyl cellulose salt, nitrile rubber, polyvinylidene fluoride, polyhexafluoropropylene, polyvinylpyrrolidone, polyamide, polyethylene ether, and polymethyl methacrylate. Alternatively, several of these can be selected and compounded. For example, the adhesive may include polyacrylic acid and polyacrylonitrile in a mass ratio of 1:2.5-4.0; or the adhesive may include carboxymethyl cellulose salt and polyamide in a mass ratio of 2.3-4.8:1.

[0173] An exemplary embodiment of this disclosure provides a lithium-ion battery, including any of the negative electrode sheets described above.

[0174] The negative electrode in this embodiment can be the same as the negative electrode in the above embodiment. After being charged at 25°C, the electrode resistance is not higher than 5Ω / m and the electrode adhesion force is not higher than 20N / m.

[0175] In this embodiment, the lithium-ion battery may further include a positive electrode and an electrolyte. The types of the positive electrode and electrolyte are not particularly limited, as long as they achieve the purpose of this disclosure. The positive electrode can be formed by coating with a positive active material. For example, the positive active material can be at least one of lithium cobalt oxide, lithium manganese oxide, nickel-cobalt-manganese ternary materials, lithium iron phosphate, lithium-rich lithium cobalt oxide, lithium-rich lithium nickel manganese oxide, and lithium-rich manganese-based materials.

[0176] Lithium-ion batteries may also include a separator, separating the positive and negative electrode sheets to prevent internal short circuits. The positive and negative electrode sheets and the separator are wound or stacked to form a bare cell, which is then processed through liquid injection / formation / molding to create a finished lithium-ion battery. The fully charged voltage of a lithium-ion battery is not less than 4.5V.

[0177] The material of the separator is not particularly limited, as long as it can achieve the purpose of this disclosure; for example, the separator can be a polyolefin separator, a polyester separator, a polyamide separator, etc.; the polyolefin separator can be a polyethylene resin separator or a polypropylene resin separator; the polyester separator can be a polyethylene terephthalate separator; the polyamide separator can be a nylon 6 separator or a nylon 66 separator.

[0178] An exemplary embodiment of this disclosure provides an electronic device including the lithium-ion battery described above. The electronic device may be, for example, a mobile phone, a laptop computer, a tablet computer, or a wearable device.

[0179] To more clearly explain the technical solution of this disclosure, specific embodiments of the negative electrode are provided, and the beneficial effects of selecting the above-mentioned ranges of parameters are illustrated by specific experimental data through specific embodiments.

[0180] Example

[0181] It should be noted that, unless otherwise specified, the raw materials used in the following embodiments are all commercially available.

[0182] The anode current collector is copper foil; the carbon material is graphite; the silicon-based material is pure silicon; the first conductive agent is conductive carbon black and carbon nanotubes in a mass ratio of 1:1.5; the first binder is sodium carboxymethyl cellulose and polyacrylic acid in a mass ratio of 1:1.2; the second conductive agent is single-walled carbon nanotubes and multi-walled carbon nanotubes in a mass ratio of 1:1; the first solvent is N-methylpyrrolidone; the second binder is polyvinyl alcohol; the high-temperature resistant material is polyvinylidene fluoride-hexafluoropropylene copolymer; the second anode active material is graphite; the second solvent is N-methylpyrrolidone; the inorganic filler is gibbsite; the third conductive agent is carbon nanotube clusters, which are single-walled carbon nanotubes and multi-walled carbon nanotubes in a mass ratio of 1:1; and the third binder is nitrile rubber.

[0183] Example 1: A negative electrode sheet is prepared by the following method:

[0184] (1) Mix 60.5% of the first negative electrode active material, 23.2% of the first conductive agent, and 16.3% of the first binder to obtain the first effective component. The first negative electrode active material includes carbon material and silicon-based material, and the mass ratio of carbon material to silicon-based material is 2.5:1.

[0185] (2) The first effective component is mixed with the first solvent to obtain the first active material.

[0186] (3) The first active material is coated on both sides of the negative electrode current collector to form a first active material layer on both sides of the negative electrode current collector, thereby obtaining an electrode intermediate. The tensile strength of the negative electrode current collector is 0.5 GPa, and the tensile strength of the elastic region is 0.3 GPa.

[0187] (4) The electrode intermediate is cold-pressed to obtain the negative electrode. The width of the negative electrode is 30 mm; the weight per unit area of ​​the negative electrode is 40 mg / cm³. 2 The thickness of the cold-pressed electrode sheet is 0.02 mm.

[0188] The tensile strength M of the elastic region of the negative electrode current collector, the electrode width change rate ΔW1 when the battery is fully charged, and the electrode width change rate ΔW2 when the battery is overcharged to 150% SOC satisfy the following relationship:

[0189] M / ΔW1=1.2; M / ΔW2=0.6; ΔW1 / ΔW2=0.5.

[0190] To more clearly explain the technical solution of this disclosure, this disclosure also provides examples 2-7 of negative electrode plates, wherein the setting parameters of examples 2-7 are shown in Table 1.

[0191] Table 1 shows specific embodiments of the negative electrode sheet in this disclosure. It should be noted that, except for the parameters listed in Table 1, the other parameters of embodiments 2-7 are basically the same as those of embodiment 1.

[0192] Wherein, the ratio C1 is the mass ratio of carbon material to silicon-based material in the first negative electrode active material.

[0193] The ratio C2 is the mass ratio of carbon material to silicon-based material and to lithium titanate.

[0194] Table 1. Setting parameters for the negative electrode sheet in Examples 1-7

[0195]

[0196] Example 8: A negative electrode sheet is prepared by the following method:

[0197] (1) 60.5% of a first negative electrode active material, 23.2% of a first conductive agent, and 16.3% of a first binder are mixed to obtain a first effective component. The first negative electrode active material includes carbon material and silicon-based material, with a mass ratio of carbon material to silicon-based material of 2.5:1. The first effective component is mixed with a first solvent to obtain a first active material.

[0198] (2) Mix 54.2% of the second negative electrode active material, 5.3% of the high-temperature resistant material, 10.5% of the second conductive agent, and 30.0% of the second binder to obtain the second effective component. Mix the second effective component with the second solvent to obtain the second active material.

[0199] (3) The first active material is coated on both sides of the negative electrode current collector to form a first active material layer on both sides of the negative electrode current collector; the second active material is coated on the first active material layer to obtain a second active material layer; thereby obtaining an electrode intermediate.

[0200] (4) The electrode intermediate is cold-pressed to obtain the negative electrode.

[0201] The thickness of the first active material layer is 0.1 μm; the weight per unit area of ​​the first active material layer is 0.2 mg / m². 2 The thickness of the second active material layer is 20.4 μm; the weight per unit area of ​​the second active material layer is 40 mg / m². 2 .

[0202] To more clearly explain the technical solution of this disclosure, this disclosure also provides examples 9-12 of negative electrode plates, wherein the setting parameters of examples 9-12 are shown in Table 2.

[0203] Table 2 shows specific embodiments of the negative electrode sheet in this disclosure. It should be noted that, except for the parameters listed in Table 2, the other parameters of embodiments 9-12 are basically the same as those of embodiment 8.

[0204] Table 2. Setting parameters for the negative electrode sheet in Examples 8-12

[0205]

[0206] Example 13: A negative electrode sheet is prepared by the following method:

[0207] (1) 60.5% of a first negative electrode active material, 23.2% of a first conductive agent, and 16.3% of a first binder are mixed to obtain a first effective component. The first negative electrode active material includes carbon material and silicon-based material, with a mass ratio of carbon material to silicon-based material of 2.5:1. The first effective component is mixed with a first solvent to obtain a first active material.

[0208] (2) Mix 51.5% inorganic filler, 7.1% third conductive agent and 41.4% third adhesive to obtain a mixture for high temperature resistant layer.

[0209] (3) A high-temperature resistant layer is coated on both sides of the negative electrode current collector with a mixture to form a high-temperature resistant layer on both sides of the negative electrode current collector. The first active material is coated on the high-temperature resistant layer to obtain the first active material layer; thereby obtaining the electrode intermediate.

[0210] (4) The electrode intermediate is cold-pressed to obtain the negative electrode.

[0211] The weight W1 of the high-temperature resistant layer per unit area is 0.5 mg / m². 2 The weight per unit area of ​​the negative electrode, W2, is 40 mg / m². 2 The ratio of W2 to W1 is 80.

[0212] To more clearly explain the technical solution of this disclosure, this disclosure also provides examples 14-18 of negative electrode plates, wherein the setting parameters of examples 14-18 are shown in Table 3.

[0213] Table 3 shows specific embodiments of the negative electrode sheet in this disclosure. It should be noted that, except for the parameters listed in Table 3, the other parameters of embodiments 14-18 are basically the same as those of embodiment 13.

[0214] Table 3. Setting parameters for the negative electrode sheet in Examples 13-18

[0215]

[0216] Application examples

[0217] The positive electrode sheet, separator, and negative electrode sheet prepared in each embodiment are wound or stacked to form a bare cell, which is then injected with liquid / formed / shaped to form a finished lithium-ion battery.

[0218] The electrolyte contains 27.0% carboxylic acid ester (methyl formate), 48.5% linear ester (dimethyl carbonate), 8.5% cyclic ester (ethylene carbonate), 12.4% ether (dibutyl ether), and 3.6% nitrile (acrylonitrile). The electrolyte viscosity is 0.05 cp.

[0219] Performance testing

[0220] The performance of the negative electrode sheet in the embodiment and the lithium-ion battery in the application example were tested respectively, and the test results are recorded in Table 4.

[0221] Application Examples 1-18 correspond to Examples 1-18, respectively.

[0222] Table 4 Performance Test Table of Battery and Negative Electrode in Application Examples

[0223]

[0224] Table 4 (continued) Performance test table of battery and negative electrode in application examples

[0225]

[0226] As can be seen from the data in Table 4, the lithium-ion battery prepared using the negative electrode sheet disclosed herein has an energy density ≥700Wh / L, a cycle life ≥1000, a voltage ≥4.50V, and a resistance ≤30mΩ. It has passed the safety performance test, indicating that the battery has good overall performance.

[0227] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This disclosure is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the claims.

[0228] It should be understood that this disclosure is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this disclosure is limited only by the appended claims.

Claims

1. A negative electrode sheet, characterized in that, The negative electrode sheet includes a negative electrode current collector. The electrode sheet width change rate ΔW1 when the battery is fully charged, the electrode sheet width change rate ΔW2 when the battery is overcharged to 150%, and the tensile strength M of the elastic region of the negative electrode current collector satisfy the following relationship: 0.1≤M / ΔW1≤1.2; 0.1≤M / ΔW2≤0.8; 0.1≤ΔW1 / ΔW2≤0.

7.

2. The negative electrode sheet according to claim 1, characterized in that, The tensile strength of the negative electrode current collector is 0.3-1.3 GPa; The tensile strength of the elastic region of the negative electrode current collector is 0.3-0.6 GPa.

3. The negative electrode sheet according to claim 1, characterized in that, The width of the negative electrode sheet is 30-120mm.

4. The negative electrode sheet according to claim 1, characterized in that, The negative electrode sheet has a unit area weight of 40-100 mg / cm³. 2 ; The thickness of the cold-pressed negative electrode sheet is 0.02-0.05 mm.

5. The negative electrode sheet according to claim 1, characterized in that, The negative electrode sheet further includes a first active material layer disposed on at least one side of the negative electrode current collector; The first active material layer includes a first active material, the first active material includes a first effective component, the first effective component includes a first negative electrode active material; the first negative electrode active material includes carbon material and silicon-based material in a predetermined ratio.

6. The negative electrode sheet according to claim 5, characterized in that, The preset ratio is 2.5-5.8:

1.

7. The negative electrode sheet according to claim 5, characterized in that, The carbon material includes at least one of graphite, hard carbon, soft carbon, and mesophase microspheres; The silicon-based material includes at least one of pure silicon, silicon alloy, silicon-carbon composite material, and silicon-oxygen composite material.

8. The negative electrode sheet according to claim 5, characterized in that, The first negative electrode active material further includes lithium titanate, and the mass ratio of the carbon material to the silicon-based material and to the lithium titanate is 2.3-4.5:

1.

9. The negative electrode sheet according to claim 5, characterized in that, The first effective component further includes a first conductive agent and a first adhesive.

10. The negative electrode sheet according to claim 9, characterized in that, The first adhesive includes at least one of sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyacrylic acid, polyacrylate, polyamide-imide, and polyvinyl alcohol; The first conductive agent includes at least one of conductive carbon black, discrete carbon nanotubes, acetylene black, conductive graphite, and graphene.

11. The negative electrode sheet according to claim 5, characterized in that, The negative electrode sheet further includes a second active material layer, which is disposed between the negative electrode current collector and the first active material layer; The second active material layer includes a second active material, and the second active material includes a second effective component; The second effective component includes a high-temperature resistant material, which has a mass change of 0-0.5% under an inert atmosphere and at a temperature of 350-450°C.

12. The negative electrode sheet according to claim 11, characterized in that, The percentage of each component of the second effective component relative to the total mass of the second effective component is as follows: Second conductive agent 10.5-22.4%; Secondary adhesive 30.0-52.7%; High-temperature resistant materials: 5.3-10.8%; The second negative electrode active material accounts for 14.1%-54.2%.

13. The negative electrode sheet according to claim 12, characterized in that, The second conductive agent includes carbon nanotubes, wherein the carbon nanotubes include at least one of single-walled carbon nanotubes and multi-walled carbon nanotubes; The second adhesive includes at least one of polyvinyl alcohol, polyvinyl acetal, carboxymethyl cellulose, carboxymethyl cellulose salt, polyacrylic acid, polyacrylate, polyvinylidene fluoride, and sodium alginate; The high-temperature resistant material includes at least one of polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride-chlorotrifluoroethylene copolymer, polyvinylidene fluoride-trichloroethylene copolymer, polymethyl methacrylate, polybutyl acrylate, polyacrylonitrile, and polyvinylpyrrolidone.

14. The negative electrode sheet according to claim 11, characterized in that, The thickness of the first active material layer is 0.1-4.5 μm; and, or The weight per unit area of ​​the first active material layer is 0.2-1.2 mg / m². 2 ; The thickness of the second active material layer is 20.4-103.1 μm; and, or The weight per unit area of ​​the second active substance layer is 40-100 mg / m². 2 .

15. The negative electrode sheet according to claim 5, characterized in that, The negative electrode sheet further includes a high-temperature resistant layer, which is disposed between the negative electrode current collector and the first active material layer. The weight W1 per unit area of ​​the high-temperature resistant layer and the weight W2 per unit area of ​​the negative electrode sheet satisfy the following relationship: 50≤W2 / W1≤200.

16. The negative electrode sheet according to claim 15, characterized in that, The weight W1 per unit area of ​​the high-temperature resistant layer is 0.5-2.5 mg / m². 2 ; The weight W2 per unit area of ​​the negative electrode sheet is 40-140 mg / m². 2 .

17. The negative electrode sheet according to claim 15, characterized in that, The high-temperature resistant layer includes a third conductive agent, the mass of which accounts for 5.2-10.8% of the total mass of the high-temperature resistant layer.

18. The negative electrode sheet according to claim 17, characterized in that, The third conductive agent includes carbon nanotube clusters, which include at least one of single-walled carbon nanotubes and multi-walled carbon nanotubes.

19. The negative electrode sheet according to claim 18, characterized in that, When the carbon nanotube cluster comprises single-walled carbon nanotubes, the average diameter of the single-walled carbon nanotubes is 1-20 nm; and / or, When the carbon nanotube cluster includes multi-walled carbon nanotubes, the average diameter of the multi-walled carbon nanotubes is 50-200 nm.

20. The negative electrode sheet according to claim 15, characterized in that, The high-temperature resistant layer further includes inorganic fillers and a third adhesive, and the percentage of the mass of the inorganic fillers and the third adhesive to the total mass of the high-temperature resistant layer is expressed as follows: Inorganic filler content: 51.5-72.5%; The third adhesive is 20.3-41.4%.

21. The negative electrode sheet according to claim 20, characterized in that, The inorganic filler includes at least one of boehmite, gibbsite, barium sulfate, calcium sulfate, calcium silicate, and magnesium hydroxide. The third adhesive includes at least one of the following: copolymers of propylene derivatives, polyacrylic acid, polyacrylate, polyacrylic acid ester, polyacrylonitrile, carboxymethyl cellulose salt, nitrile rubber, polyvinylidene fluoride, polyhexafluoropropylene, polyvinylpyrrolidone, polyamide, polyvinyl ether, and polymethyl methacrylate.

22. A lithium-ion battery, characterized in that, Includes the negative electrode sheet as described in any one of claims 1-21.

23. An electronic device, characterized in that, Including the lithium-ion battery as described in claim 22.

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