Negative active material, negative pole piece, lithium ion battery and electronic equipment

Abstract

The invention relates to a negative active material, a negative pole piece, a lithium ion battery and electronic equipment, and relates to the technical field of lithium ion batteries. The negative polarity material comprises a base material, and the base material comprises a first carbon material and a first silicon-based material in a first preset proportion. According to the invention, the first carbon material and the first silicon-based material are mixed according to the first preset proportion, so that the energy density of the battery can be effectively improved, the stress concentration generated during expansion of silicon particles can be reduced, the volume expansion of silicon can be inhibited, and the stability of the electrode structure can be improved.

Description

Technical Field

[0001] This disclosure relates to the field of lithium-ion battery technology, and in particular to a negative electrode active material, a negative electrode sheet, 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 active material, 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 active material is provided, the negative electrode active material comprising a matrix material, the matrix material comprising a first carbon material and a first silicon-based material in a first preset ratio.

[0005] In some embodiments of this disclosure, the first preset ratio is 2.3-199.0:1.

[0006] In some embodiments of this disclosure, the first carbon material includes a first porous carbon material matrix; the first silicon-based material includes a first nano-silicon material.

[0007] The first nano-silicon material is deposited in the pores of the first porous carbon material matrix.

[0008] In some embodiments of this disclosure, the first porous carbon material matrix includes at least one of hard carbon, soft carbon, carbon black, graphite, carbon fiber, vapor-grown carbon fiber, carbon nanotube, and graphene.

[0009] The first nano-silicon material is at least one of pure silicon, silicon alloy, silicon-carbon composite material, and silicon-oxygen composite material.

[0010] In some embodiments of this disclosure, the negative electrode active material further includes a polymer coating layer, which coats the surface of the matrix material.

[0011] In some embodiments of this disclosure, the polymer coating layer comprises an aromatic -COOR-containing polymer, wherein the aromatic -COOR-containing polymer is a polymer or a salt thereof with the following structural formula, the structural formula of which is shown in general formula (I):

[0012]

[0013] Wherein, R1 is selected from H, Li or Na; R2 is selected from hydrogen, sulfonic acid group, hydroxyl group, amino group or thiol.

[0014] In some embodiments of this disclosure, the aromatic -COOR-containing polymer is selected from...

[0015]

[0016] At least one of them.

[0017] In some embodiments of this disclosure, the aromatic -COOR-containing polymer accounts for 1.8-7.2% of the mass of the matrix material.

[0018] In some embodiments of this disclosure, the polymer coating layer comprises a high-temperature resistant fiber material.

[0019] In some embodiments of this disclosure, the high-temperature resistant fiber material includes aramid.

[0020] In some embodiments of this disclosure, the aramid includes at least one of meta-aramid, para-aramid, and ortho-aramid.

[0021] In some embodiments of this disclosure, the specific surface area of ​​the first porous carbon material matrix is ​​2.2-12.3 m². 2 / g; and / or

[0022] The porosity of the first porous carbon material matrix is ​​38.5-83.2%; and / or

[0023] The filling degree of the first nano-silicon material in the first porous carbon material matrix is ​​38.5-83.2%.

[0024] In some embodiments of this disclosure, the first particle size Dv50 of the first porous carbon material matrix is ​​5.0-10.5 μm; and / or

[0025] The second particle size Dv50 of the first nano-silicon material is 5.0-82.5 nm; and / or

[0026] The particle spacing of the first nano-silicon material is 1.0-23.5 nm.

[0027] In some embodiments of this disclosure, the thickness of the polymer coating layer is 1.2-5.8% of the thickness of the matrix material.

[0028] According to a second aspect of the present disclosure, a negative electrode sheet is provided, the negative electrode sheet including a negative current collector and a first active material layer disposed on at least one side of the negative current collector, the first active material layer including a first active material material, the first active material material including a first effective component, the first effective component including the negative electrode active material as described above.

[0029] In some embodiments of this disclosure, the weight per unit area of ​​the negative electrode sheet is 38-105 mg / cm². 2 ; and / or

[0030] The thickness of the negative electrode sheet is 0.01-0.15 mm.

[0031] In some embodiments of this disclosure, the negative electrode sheet further includes a second active material layer, which is disposed on the side of the first active material layer away from the positive current collector.

[0032] The second active material layer includes a second active material, and the second active material includes a second effective component;

[0033] When the battery is fully charged, the first active material layer has a first thickness H1, and the second active material layer has a second thickness H2. The first thickness H1 and the second thickness H2 satisfy the following relationship:

[0034] 1.3≤H1 / H2≤6.6.

[0035] In some embodiments of this disclosure, the first active material layer has a third thickness H3 after cold pressing, wherein the third thickness H3 is 15.5-52.4 μm;

[0036] The first thickness H1 is 20.3-79.6 μm;

[0037] The second active material layer has a fourth thickness H4 after cold pressing, and the fourth thickness H4 is 5.2-20.7 μm;

[0038] The second thickness H2 is 5.5-25.5 μm.

[0039] In some embodiments of this disclosure, the first weight m1 per unit volume of the first active material layer is 40.4-82.3 mg / cc;

[0040] The second weight m2 per unit volume of the second active substance layer is 9.6-42.5 mg / cc.

[0041] In some embodiments of this disclosure, the second effective component includes a second carbon material and a second silicon-based material in a second preset ratio;

[0042] The second carbon material includes a second porous carbon material matrix; the second silicon-based material includes a second nano-silicon material; the second nano-silicon material is deposited in the pores of the second porous carbon material matrix.

[0043] In some embodiments of this disclosure, when the first carbon material includes first graphite, the orientation index of the first graphite is 5.2-21.5;

[0044] When the second porous carbon material matrix includes a second graphite, the orientation index of the second graphite is 4.8-12.3.

[0045] In some embodiments of this disclosure, when the second porous carbon material matrix further includes hard carbon, the mass of the hard carbon accounts for 4.7-22.1% of the mass of the second effective component.

[0046] In some embodiments of this disclosure, the surface pore volume of the hard carbon is 0.05-0.08 cc / g.

[0047] In some embodiments of this disclosure, the first effective component further includes a first adhesive, which includes polyacrylic acid and its derivatives or alkali metal salts of polyacrylic acid and its derivatives.

[0048] The second effective component further includes a second adhesive, which includes at least two of styrene-butadiene rubber, styrene-acrylic emulsion, polyacrylic acid and its derivatives, and alkali metal salts of polyacrylic acid and its derivatives.

[0049] In some embodiments of this disclosure, the first active material further includes a first solvent, which includes at least one of methyl acetate, acetone, cyclohexane, and tetrahydrofuran.

[0050] The second active material also includes a second solvent, which includes at least one of N-methylpyrrolidone, ethylene carbonate, dimethyl carbonate, and ethyl carbonate.

[0051] According to a third aspect of the present disclosure, a lithium-ion battery is provided, including a negative electrode as described above.

[0052] In some embodiments of this disclosure, the lithium-ion battery further includes an electrolyte comprising linear carbonate, wherein the linear carbonate accounts for 10-70% of the total mass of the electrolyte.

[0053] In some embodiments of this disclosure, the percentage of silicon mass in the first silicon-based material relative to the total mass of the first effective component is x;

[0054] The width of the negative electrode sheet is y;

[0055] The length of the inner pit of the isolation membrane is z;

[0056] The silicon content x, the width y of the negative electrode sheet, and the pit length z of the separator membrane satisfy the following relationship:

[0057] 0.5≤y / x≤2;

[0058] 1≤zy≤1.6.

[0059] In some embodiments of this disclosure, the content 'a' of the linear carbonate and the content 'x' of the silicon satisfy the following relationship:

[0060] 0.2≤a / x≤2.0.

[0061] In some embodiments of this disclosure, the silicon content x is 0.5-22.4%.

[0062] In some embodiments of this disclosure, the electrolyte further includes at least one of cyclic esters, ether compounds, and nitrile compounds; the viscosity of the electrolyte is less than or equal to 1 cp.

[0063] According to a fourth aspect of the present disclosure, an electronic device is provided, including a lithium-ion battery as described above.

[0064] The technical solutions provided by the embodiments of this disclosure may include the following beneficial effects:

[0065] This disclosure, by mixing a first carbon material and a first silicon-based material in a first preset ratio, can effectively increase the energy density of the battery while reducing stress concentration caused by the expansion of silicon particles, suppressing the volume expansion of silicon, and improving the stability of the electrode structure.

[0066] 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

[0067] 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.

[0068] Figure 1 This is a schematic diagram of the layer structure of a negative electrode sheet according to an exemplary embodiment.

[0069] Figure 2 This is a schematic diagram of the layer structure of a negative electrode sheet according to an exemplary embodiment.

[0070] Figure 3 This is a schematic diagram of the layer structure of a negative electrode sheet according to an exemplary embodiment. Detailed Implementation

[0071] 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.

[0072] 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.

[0073] To address the above technical issues, this disclosure provides a negative electrode active material, which includes a matrix material comprising a first carbon material and a first silicon-based material in a first preset ratio. By mixing the first carbon material and the first silicon-based material in the first preset ratio, the energy density of the battery can be effectively increased while reducing stress concentration caused by the expansion of silicon particles, suppressing the volume expansion of silicon, and improving the stability of the electrode structure.

[0074] An exemplary embodiment of this disclosure provides a negative electrode active material, the negative electrode active material including a matrix material, the matrix material including a first carbon material and a first silicon-based material in a first preset ratio.

[0075] In this embodiment, by mixing the first carbon material and the first silicon-based material in a first preset ratio, the energy density of the battery can be effectively improved while reducing stress concentration caused by the expansion of silicon particles, suppressing the volume expansion of silicon, and improving the stability of the electrode structure.

[0076] In an exemplary embodiment, the first preset ratio is 2.3-199.0:1.

[0077] In this embodiment, controlling the first preset ratio within the range of 2.3-99.0:1 allows the battery to maintain optimal overall performance. Exemplarily, the first preset ratio can be 2.3:1, 30.2:1, 49.7:1, 71.1:1, 145.5:1, or 199.0:1. The first preset ratio can also be any value within the exemplary range, for example, any value between 30.2 and 71.1:1.

[0078] In an exemplary embodiment, the first carbon material includes a first porous carbon material matrix; the first silicon-based material includes a first nano-silicon material; the first nano-silicon material is deposited in the pores of the first porous carbon material matrix.

[0079] In this embodiment, the first nano-silicon material is deposited in the pores of the first porous carbon material matrix, which can reduce the stress concentration caused by the expansion of silicon particles and reduce the risk of material breakage, thereby helping to improve the energy density, cycle stability and rate performance of the battery.

[0080] In an exemplary embodiment, the first porous carbon material matrix includes at least one of hard carbon, soft carbon, carbon black, graphite, carbon fiber, vapor-grown carbon fiber, carbon nanotube, and graphene; and the first nano-silicon material includes at least one of pure silicon, silicon alloy, silicon-carbon composite material, and silicon-oxygen composite material.

[0081] In this embodiment, the first porous carbon material matrix can be one of hard carbon, soft carbon, carbon black, graphite, carbon fiber, vapor-grown carbon fiber, carbon nanotubes, and graphene, or a combination of several of them. For example, the first porous carbon material matrix includes graphite and hard carbon in a mass ratio of 1.2-3.5:1, or the first porous carbon material matrix includes graphite, hard carbon, and soft carbon in a mass ratio of 0.8-1.2:2.3-3.3:1. The first nano-silicon material can be one of pure silicon, silicon alloy, silicon-carbon composite material, and silicon-oxygen composite material, or a combination of several of them. For example, the first nano-silicon material includes pure silicon and silicon-carbon composite material in a mass ratio of 0.5-1.2:1, or the first nano-silicon material includes a mass ratio of 1.2-2.1:3.1-3.6:1.

[0082] In one exemplary embodiment, the negative electrode active material further includes a polymer coating layer that coats the surface of the matrix material.

[0083] In this embodiment, by coating the surface of the matrix material with a polymer coating layer, the problem of cyclic expansion of the negative electrode sheet can be reduced, effectively improving the energy density of the battery.

[0084] In one exemplary embodiment, the polymer coating layer comprises an aromatic -COOR-containing polymer, which is a polymer or a salt thereof with the following structural formula, as shown in general formula (I):

[0085]

[0086] R1 is selected from H, Li or Na; R2 is selected from hydrogen, sulfonic acid group, hydroxyl group, amino group or thiol.

[0087] In this embodiment, by coating the matrix material with an aromatic -COOR-containing polymer, the silicon particles form chemical bonds with the -COOR bonds, which can reduce the expansion of the negative electrode and effectively improve the energy density of the battery. Furthermore, coating the matrix material with the aromatic -COOR-containing polymer facilitates ion transport between matrix materials, thereby improving the battery's initial efficiency and cycle performance.

[0088] When the polymer coating layer includes an aromatic -COOR polymer, the negative electrode active material can be prepared by the following method: mixing the matrix material and the aromatic -COOR polymer at a temperature of 40-60°C, so that the aromatic -COOR polymer is uniformly coated on the surface of the matrix material to form a polymer coating layer.

[0089] In one exemplary embodiment, the aromatic -COOR-containing polymer is selected from...

[0090]

[0091] At least one of them.

[0092] In this embodiment, the aromatic -COOR polymer can be one of the polymers mentioned above, or several of them can be selected for compounding. For example, the aromatic -COOR polymer can include an aromatic -COOH polymer containing sulfonic acid groups and an aromatic -COOLi polymer containing hydroxyl groups in a mass ratio of 1.5-2.5:1.

[0093] In one exemplary embodiment, the aromatic -COOR-containing polymer accounts for 1.8-7.2% of the mass of the matrix material.

[0094] In this embodiment, the mass ratio of the aromatic -COOR-containing polymer to the matrix material can be 1.8%, 3.4%, 4.5%, 6.1%, or 7.2%. The mass ratio of the aromatic -COOR-containing polymer to the matrix material can also be any value within the exemplary mass percentage range; for example, the mass ratio of the aromatic -COOR-containing polymer to the matrix material can be any value between 3.4% and 6.1%.

[0095] In one exemplary embodiment, the polymer coating layer comprises a high-temperature resistant fiber material.

[0096] In this embodiment, using high-temperature resistant fiber material as the coating layer of the matrix material can improve the high-temperature stability of the electrode, thereby reducing the probability of battery thermal runaway and improving the battery's safety performance.

[0097] In one exemplary embodiment, the high-temperature resistant fiber material includes aramid.

[0098] Aramid, as a high-performance synthetic fiber, has the advantages of high tensile strength, high temperature resistance and low coefficient of thermal expansion, which are beneficial to improving the high temperature stability of batteries and reducing the probability of thermal runaway. In addition, coating with aramid can also improve the wetting of electrolyte and improve the initial efficiency and cycle performance of batteries.

[0099] When the polymer coating layer includes aramid, the negative electrode active material can be prepared by the following method: depositing a first nano-silicon material on a first porous carbon material matrix to form a matrix material; mixing the matrix material and aramid at a temperature of 200-500℃ to uniformly coat the surface of the matrix material with aramid to form a polymer coating layer.

[0100] In one exemplary embodiment, the aramid includes at least one of meta-aramid, para-aramid, and ortho-aramid.

[0101] Meta-aramid (aramid 1313) has a serrated molecular chain arrangement, exhibiting excellent high-temperature resistance and chemical stability; para-aramid (aramid 1414) has a linear molecular chain arrangement, resulting in even better high-temperature resistance; ortho-aramid also possesses the advantages of high-temperature resistance and chemical stability. In this embodiment, the aramid can be one of meta-aramid, para-aramid, or ortho-aramid, or a blend of several of them. For example, the aramid includes meta-aramid and para-aramid in a mass ratio of 1.2-2.8:1.

[0102] In one exemplary embodiment, the specific surface area of ​​the first porous carbon material matrix is ​​2.2-12.3 m². 2 / g.

[0103] The high specific surface area of ​​the first porous carbon material matrix can provide more active sites, increasing the contact area with the electrolyte, thereby improving the charge transfer rate and reaction kinetics of the battery. In this embodiment, by controlling the specific surface area of ​​the first porous carbon material matrix, the battery can maintain better overall performance. For example, the specific surface area of ​​the first porous carbon material matrix can be 2.2 m². 2 / g, 4.8m 2 / g, 7.3m 2 / g, 10.4m 2 / g, 12.3m 2 / g. The specific surface area of ​​the first porous carbon material matrix can also be any value between the exemplary specific surface area values; for example, the specific surface area of ​​the first porous carbon material matrix can also be 4.8-10.4 μm. 2 Any value between / g.

[0104] In one exemplary embodiment, the porosity of the first porous carbon material matrix is ​​38.5-83.2%.

[0105] Porosity can affect the ion diffusion rate and electron transport efficiency of a battery. Higher porosity helps improve the rate performance and cycle stability of the battery, and reduces the shedding of active material and structural damage. In this embodiment, controlling the porosity of the first porous carbon material matrix can help maintain better overall battery performance. For example, the porosity of the first porous carbon material matrix can be 38.5%, 45.1%, 68.1%, 76.3%, or 83.2%. The porosity of the first porous carbon material matrix can also be any porosity between the exemplary porosities; for example, the porosity of the first porous carbon material matrix can be any porosity between 45.1% and 68.1%.

[0106] In one exemplary embodiment, the first nano-silicon material has a filling degree of 38.5-83.2% in the first porous carbon material matrix.

[0107] In this embodiment, the filling degree of the first nano-silicon material in the first porous carbon material matrix is ​​related to the porosity of the first porous carbon material matrix. The filling degree of the first nano-silicon material in the first porous carbon material matrix is ​​less than or equal to the porosity of the first porous carbon material matrix. For example, the filling degree of the first nano-silicon material in the first porous carbon material matrix can be 38.5%, 40.2%, 45.1%, 68.1%, 71.2%, 76.3%, or 83.2%. The filling degree of the first nano-silicon material in the first porous carbon material matrix can also be any filling degree between the exemplary filling degrees; for example, the filling degree of the first nano-silicon material in the first porous carbon material matrix can also be any filling degree between 40.2% and 68.1%.

[0108] In an exemplary embodiment, the first particle size Dv50 of the first porous carbon material matrix is ​​5.0-10.5 μm.

[0109] Here, Dv50, also known as D50, is a parameter describing particle size, indicating that in a set of particle size distributions, 50% of the particles have a particle size smaller than or equal to this value. For example, Dv50 indicates that 50% of the particles in the first porous carbon material matrix have a particle size smaller than or equal to 5.0-10.5 μm. In this embodiment, the first particle size Dv50 of the first porous carbon material matrix is ​​5.0 μm, 7.8 μm, 8.5 μm, 9.3 μm, and 10.5 μm. The first particle size Dv50 of the first porous carbon material matrix can also be any particle size between the exemplary first particle sizes; for example, the first particle size Dv50 of the first porous carbon material matrix can also be any particle size between 7.8 and 9.3 μm.

[0110] In an exemplary embodiment, the second particle size Dv50 of the first nano-silicon material is 5.0-82.5 nm.

[0111] In this embodiment, the second particle size Dv50 of the first nano-silicon material can be, for example, 5.0 nm, 25.7 nm, 48.9 nm, 67.1 nm, or 82.5 nm. The second particle size Dv50 of the first nano-silicon material can also be any particle size between the exemplary second particle sizes; for example, the second particle size Dv50 of the first nano-silicon material can also be any particle size between 25.7 and 67.1 nm.

[0112] In an exemplary embodiment, the particle spacing of the first nano-silicon material is 1.0-23.5 nm.

[0113] In this embodiment, the particle spacing of the first nano-silicon material can be 1.0 nm, 5.8 nm, 13.6 nm, 18.9 nm, or 23.5 nm. The particle spacing of the first nano-silicon material can also be any value between the exemplary particle spacings; for example, the particle spacing of the first nano-silicon material can be any value between 5.8 and 18.9 nm.

[0114] In one exemplary embodiment, the thickness of the polymer coating layer is 1.2-5.8% of the thickness of the base material.

[0115] In this embodiment, by controlling the ratio of the polymer coating thickness to the substrate material thickness, the battery can maintain better overall performance. For example, the thickness of the polymer coating is 1.2%, 2.3%, 3.8%, 4.5%, or 5.8% of the substrate material thickness. The ratio of the polymer coating thickness to the substrate material thickness can also be any value between the exemplary ratios; for example, the ratio of the polymer coating thickness to the substrate material thickness can be any value between 2.3% and 4.5%.

[0116] like Figure 1 As shown, an exemplary embodiment of this disclosure provides a negative electrode sheet, which includes a negative electrode current collector 1 and 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, which includes a first effective component, and the first effective component includes the negative electrode active material as described above.

[0117] In this embodiment, by combining a first porous carbon material matrix with a first nano-carbon material, the energy density, cycle stability, charge / discharge efficiency, rate performance, and mechanical stability of the battery can be improved. The material of the negative electrode current collector 1 is not particularly limited and can be any negative electrode current collector 1 known in the art, such as copper foil or composite copper foil.

[0118] like 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 2As 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.

[0119] For example, the negative electrode sheet can be prepared by coating the 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.

[0120] In one exemplary embodiment, the negative electrode sheet has a surface area weight of 38-105 mg / cm². 2 .

[0121] 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 can be 38 mg / cm³. 2 54mg / cm 2 79mg / cm 2 95mg / cm 2 105mg / 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 54-95 mg / cm³. 2 Any value between.

[0122] In one exemplary embodiment, the thickness of the negative electrode sheet is 0.01-0.15 mm.

[0123] In this embodiment, by controlling the thickness of the negative electrode sheet, the battery can maintain better overall performance. For example, the thickness of the negative electrode sheet can be 0.01mm, 0.05mm, 0.08mm, 0.10mm, or 0.15mm. The thickness of the negative electrode sheet can also be any thickness between the exemplary values; for example, the thickness of the negative electrode sheet can be any value between 0.05mm and 0.10mm.

[0124] like Figure 3 As shown in an exemplary embodiment of this disclosure, the negative electrode further includes a second active material layer 3, which is disposed on the side of the first active material layer 2 away from the positive current collector; the second active material layer 3 includes a second active material material, which includes a second effective component; when the battery is fully charged, the first active material layer 2 has a first thickness H1, and the second active material layer 3 has a second thickness H2, wherein the first thickness H1 and the second thickness H2 satisfy the following relationship:

[0125] 1.3≤H1 / H2≤6.6.

[0126] In this embodiment, the negative electrode sheet, by setting multiple active material layers, can effectively solve the cycle expansion problem of lithium-ion batteries. For example, the ratio of the first thickness H1 to the second thickness H2 can be 1.3, 2.5, 3.5, 5.2, or 6.6. The ratio of the first thickness H1 to the second thickness H2 can also be any ratio between the exemplary ratios; for example, the ratio of the first thickness H1 to the second thickness H2 can also be any ratio between 2.5 and 5.2.

[0127] In an exemplary embodiment, the first active material layer 2 has a third thickness H3 after cold pressing, the third thickness H3 being 15.5-52.4 μm; the first thickness H1 being 20.3-79.6 μm; the second active material layer 3 has a fourth thickness H4 after cold pressing, the fourth thickness H4 being 5.2-20.7 μm; and the second thickness H2 being 5.5-25.5 μm.

[0128] In this embodiment, the third thickness H3 of the first active material layer 2 after cold pressing can be 15.5 μm, 28.9 μm, 43.2 μm, or 52.4 μm. The third thickness H3 of the first active material layer 2 after cold pressing can also be any thickness between the exemplary thickness values. For example, the third thickness H3 can also be any thickness between 28.9 and 43.2 μm.

[0129] The first thickness H1 can be 20.3 μm, 45.7 μm, 60.7 μm, 70.4 μm, or 79.6 μm. The first thickness H1 can also be any thickness between the exemplary thickness values; for example, the first thickness H1 can also be any thickness between 45.7 and 70.4 μm.

[0130] The fourth thickness H4 after cold pressing of the second active material layer 3 can be 5.2 μm, 8.1 μm, 13.7 μm, 17.0 μm, or 20.7 μm. The fourth thickness H4 after cold pressing of the second active material layer 3 can also be any thickness between the exemplary thickness values, for example, the fourth thickness H4 can also be any thickness between 8.1 and 17.0 μm.

[0131] The second thickness H2 can be 5.5μm, 10.5μm, 14.9μm, 18.0μm, 20.6μm, or 25.5μm. The second thickness H2 can also be any thickness between the exemplary thickness values; for example, the second thickness H2 can also be any thickness between 10.5 and 20.6μm.

[0132] For example, in one embodiment, the first thickness H1 is 20.3 μm and the second thickness H2 is 5.5 μm, then the ratio of H1 / H2 is 3.7.

[0133] In another embodiment, the first thickness H1 is 25.0 μm and the second thickness H2 is 19.2 μm, then the ratio of H1 / H2 is 1.3.

[0134] In another embodiment, the first thickness H1 is 66.0 μm and the second thickness H2 is 10.0 μm, then the ratio of H1 / H2 is 6.6.

[0135] In another embodiment, the first thickness H1 is 79.6 μm and the second thickness H2 is 25.5 μm, then the ratio of H1 / H2 is 3.1.

[0136] In an exemplary embodiment, the first weight m1 per unit volume of the first active material layer 2 is 40.4-82.3 mg / cc; the second weight m2 per unit volume of the second active material layer 3 is 9.6-42.5 mg / cc.

[0137] In this embodiment, by controlling the first weight m1 per unit volume of the first active material layer 2 and the second weight m2 per unit volume of the second active material layer 3, the battery can maintain better overall performance. For example, the first weight m1 per unit volume of the first active material layer 2 can be 40.4 mg / cc, 63.2 mg / cc, 77.0 mg / cc, or 82.3 mg / cc. The first weight m1 per unit volume of the first active material layer 2 can also be any value between the exemplary first weight values; for example, the first weight m1 per unit volume of the first active material layer 2 can also be any value between 63.2 and 77.0 mg / cc.

[0138] The second weight m2 per unit volume of the second active substance layer 3 can be 9.6 mg / cc, 19.2 mg / cc, 32.0 mg / cc, 37.6 mg / cc, or 42.5 mg / cc. The second weight m2 per unit volume of the second active substance layer 3 can also be any value between the exemplary second weight values; for example, the second weight m2 per unit volume of the second active substance layer 3 can also be any value between 19.2 and 37.6 mg / cc.

[0139] In an exemplary embodiment, the second effective component includes a second carbon material and a second silicon-based material in a second preset ratio; the second carbon material includes a second porous carbon material matrix; the second silicon-based material includes a second nano-silicon material; and the second nano-silicon material is deposited in the pores of the second porous carbon material matrix.

[0140] In this embodiment, by setting a first active material layer 2 and a second active material layer 3, and by including nano-silicon materials and porous carbon material matrices in the first active material layer 2 and the second active material layer 3, the problem of battery cycle expansion can be effectively solved.

[0141] In an exemplary embodiment, when the first carbon material includes first graphite, the orientation index of the first graphite is 5.2-21.5; when the second porous carbon material matrix includes second graphite, the orientation index of the second graphite is 4.8-12.3.

[0142] The orientation index (OI) of graphite is a parameter describing the degree of orderliness of the graphite sheets in a graphite material. By controlling the orientation of graphite, the charge-discharge performance and cycle performance of a battery can be optimized. For example, the OI value of the first graphite can be 5.2, 7.4, 10.5, 14.6, 19.1, or 21.5. The OI value of the first graphite can also be any OI value between the exemplary OI values; for example, the OI value of the first graphite can be any OI value between 10.5 and 19.1. The OI value of the second graphite can be 4.8, 7.2, 8.5, 10.3, or 12.3. The OI value of the second graphite can also be any OI value between the exemplary OI values; for example, the OI value of the second graphite can be any OI value between 7.2 and 10.3.

[0143] In one exemplary embodiment, when the second porous carbon material matrix further includes hard carbon, the mass of hard carbon accounts for 4.7-22.1% of the mass of the second effective component.

[0144] In this embodiment, hard carbon is incorporated into the second porous carbon material matrix, which can improve the low-temperature discharge performance of the battery. By controlling the mass percentage of hard carbon in the second effective component, the battery can maintain optimal overall performance. For example, the mass percentage of hard carbon in the second effective component is 4.7%, 8.2%, 13.5%, 18.8%, and 22.1%. The ratio of the mass of hard carbon to the mass of the second effective component can also be any of the exemplary ratios; for example, the ratio of the mass of hard carbon to the mass of the second effective component can be any ratio between 8.2% and 18.8%.

[0145] In one exemplary embodiment, the surface pore volume of hard carbon is 0.05-0.08 cc / g.

[0146] In this embodiment, the surface pore volume of hard carbon can be 0.05cc / g, 0.06cc / g, 0.07cc / g, or 0.08cc / g. The surface pore volume of hard carbon can also be any value between the exemplary surface pore volumes; for example, the surface pore volume of hard carbon can be any value between 0.06 and 0.07cc / g.

[0147] In one exemplary embodiment, the first effective component further includes a first adhesive, which comprises polyacrylic acid and its derivatives or alkali metal salts of polyacrylic acid and its derivatives; the second effective component further includes a second adhesive, which comprises at least two of styrene-butadiene rubber, styrene-acrylic emulsion, polyacrylic acid and its derivatives, and alkali metal salts of polyacrylic acid and its derivatives.

[0148] In this embodiment, the first adhesive and the second adhesive serve to bond the electrode, ensuring the integrity of the electrode structure. The polyacrylic acid and its derivatives, or alkali metal salts of polyacrylic acid and its derivatives, can be polyacrylic acid, sodium polyacrylate, potassium polyacrylate, polyacrylamide, etc. The second adhesive can be, for example, a mixture of styrene-butadiene rubber and styrene-acrylic emulsion in a mass ratio of 2.3-4.0:1; or, a mixture of styrene-butadiene rubber, styrene-acrylic emulsion, and polyacrylic acid in a mass ratio of 1.1-3.4:2.3-4.3:1.

[0149] In order to form a conductive network between the negative electrode active material and the negative electrode current collector 1, the first active material further includes a first conductive agent, and the second active material further includes a second conductive agent. The first and second conductive agents can be one or more of conductive carbon black, carbon nanotubes, acetylene black, conductive graphite, and graphene.

[0150] In an exemplary embodiment, the first active material further includes a first solvent, which includes at least one of methyl acetate, acetone, cyclohexane, and tetrahydrofuran; the second active material further includes a second solvent, which includes at least one of N-methylpyrrolidone, ethylene carbonate, dimethyl carbonate, and ethyl carbonate.

[0151] The first and second effective components contain the main functional ingredients. The first and second active materials can be applied to the negative electrode current collector 1 by roller coating or extrusion. To improve the uniformity of the negative electrode active material coating, the first active material may also include a first solvent, and the second active material may also include a second solvent. The first (second) solvent can dissolve or disperse the first (second) effective component, thus making the first (second) active material into a slurry. The first (second) 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.

[0152] An exemplary embodiment of this disclosure provides a lithium-ion battery, including the negative electrode as described above.

[0153] The lithium-ion battery may further include a positive electrode sheet. The type of positive electrode sheet is not particularly limited, as long as it achieves the purpose of this disclosure. The positive electrode sheet can be formed by coating a positive electrode active material. For example, the positive electrode active material can be selected from 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 nickel-manganese oxide, and lithium-rich manganese-based materials.

[0154] In one exemplary embodiment, the lithium-ion battery further includes an electrolyte comprising linear carbonate, wherein the linear carbonate accounts for 10-70% of the total mass of the electrolyte.

[0155] In this embodiment, by controlling the mass percentage of linear carbonate, the low-temperature performance of the battery can be improved. The linear carbonate can be, for example, one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), and dipropyl carbonate (DPC). Exemplarily, the mass percentage of linear carbonate is 10%, 30%, 35%, 43%, 47%, 50%, or 70% of the total electrolyte mass. The mass percentage of linear carbonate to the total electrolyte mass can also be any of the exemplary ratios, for example, any ratio between 35% and 47% of the total electrolyte mass.

[0156] 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.

[0157] 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.

[0158] In one exemplary embodiment, the percentage of silicon mass in the first silicon-based material relative to the total mass of the first effective component is x;

[0159] The width of the negative electrode plate is y;

[0160] The length of the inner pit of the separator is z;

[0161] The silicon content x, the width y of the negative electrode sheet, and the pit length z of the separator satisfy the following relationship:

[0162] 0.5 ≤ y / x ≤ 2.0;

[0163] 1.0≤zy≤1.6.

[0164] In this embodiment, by controlling the silicon content x, the width y of the negative electrode sheet, and the inner pit length z of the separator, reliability issues such as corrosion caused by the anode top packaging film due to xy expansion (i.e., expansion in the x-axis direction and y-axis direction) during battery cycling can be reduced, thereby avoiding the problem of corner breakage and leakage.

[0165] For example, in one embodiment, the silicon content x, the width y of the negative electrode sheet, and the inner pit length z of the separator satisfy the following relationship: y / x = 0.5; zy = 1.0.

[0166] In another embodiment, the silicon content x, the width y of the negative electrode sheet, and the pit length z of the separator satisfy the following relationship: y / x = 1.5; zy = 1.4.

[0167] In another embodiment, the silicon content x, the width y of the negative electrode sheet, and the inner pit length z of the separator satisfy the following relationship: y / x = 2.0; zy = 1.6.

[0168] In an exemplary embodiment, the linear carbonate content a and the silicon content x satisfy the following relationship: 0.2 ≤ a / x ≤ 2.0.

[0169] In this embodiment, by controlling the relationship between silicon content and linear carbonate in the electrolyte, the operating temperature range of the battery can be broadened, which helps to reduce the risks of battery swelling due to high temperature. For example, the a / x ratio can be 0.2, 0.8, 1.3, 1.6, or 2.0. a / x can also be any ratio between these exemplary values; for example, the a / x ratio can be any ratio between 0.8 and 1.6.

[0170] In one exemplary embodiment, the silicon content x is 0.5-22.4%.

[0171] In this embodiment, by controlling the silicon content, the battery can maintain better overall performance. For example, the silicon content x is 0.5%, 3.8%, 8.6%, 12.4%, 16.5%, and 22.4%. The silicon content x can also be any of the exemplary contents; for example, the silicon content can be any content between 3.8% and 12.4%.

[0172] For example, the silicon content x of the first silicon-based material is 10%, the width y of the negative electrode is 20 mm, the inner pit length z of the separator is 21.5 mm, and the linear carbonate content a is 10%; then y / x = 2.0; zy = 1.5; a / x = 1.0.

[0173] In one exemplary embodiment, the electrolyte further includes at least one of cyclic esters, ether compounds, and nitrile compounds; the electrolyte viscosity is less than or equal to 1 cp.

[0174] In this embodiment, the electrolyte is compounded using the above-mentioned components, and the viscosity of the electrolyte is controlled at 1 cp, which can improve the ion migration rate, reduce the battery resistance, and improve the overall performance of the battery.

[0175] Among them, the cyclic ester can be one or more of ethylene carbonate (EC), propylene carbonate (PC), and butyl carbonate (BC), and its amount can be 3-10%; the ether compound can be one or more of dibutyl ether, diethylene glycol dimethyl ether, and ethoxymethoxyethane, and its amount can be 5-15%; the nitrile compound can be, for example, acrylonitrile, and its amount can be 0.5-5%.

[0176] 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.

[0177] 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.

[0178] Example

[0179] It should be noted that, unless otherwise specified, the raw materials used in the following embodiments are all commercially available.

[0180] The negative electrode current collector is copper foil; the first porous carbon material matrix is ​​first graphite with an OI value of 10.5; the first silicon nanomaterial is pure silicon; the polymer coating layer (aromatic polymer containing -COOR) is an aromatic polymer containing -COOH with sulfonic acid groups; the polymer coating layer (high temperature resistant fiber material) is meta-aramid; the first conductive agent is conductive carbon black and carbon nanotubes in a mass ratio of 1:1.5; the first binder is polyacrylic acid; the first solvent is methyl acetate; the second porous carbon material matrix is ​​second graphite and hard carbon with an OI value of 8.5; the second nanomaterial is pure silicon; the second conductive agent is conductive carbon black; the second binder is styrene-butadiene rubber; and the second solvent is N-methylpyrrolidone.

[0181] Example 1: A negative electrode sheet is prepared by the following method:

[0182] (1) 60.5% of the negative electrode active material, 23.2% of the first conductive agent, and 16.3% of the first binder are mixed to obtain the first effective component. The negative electrode active material comprises a first porous carbon material matrix and a first nano-silicon material, wherein the mass percentage of silicon in the first silicon-based material is x = 5.0% of the total mass of the first effective component.

[0183] (2) The first effective component is mixed with the first solvent to obtain the first active material.

[0184] (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 the electrode intermediate.

[0185] (4) The electrode intermediate is cold-pressed to obtain the negative electrode.

[0186] The negative electrode sheet has a unit area weight of 38 mg / cm². 2 The thickness of the negative electrode sheet is 0.05 mm.

[0187] The positive electrode sheet, separator, and negative electrode sheet prepared in Example 1 are wound or stacked to form a bare cell, which is then injected with liquid / formed / shaped to form a finished lithium-ion battery.

[0188] In Example 1, the content of linear carbonate (dimethyl carbonate) a in the electrolyte was 10%.

[0189] The width y of the negative electrode sheet is 2.5mm; the inner pit length z of the separator is 3.5mm;

[0190] y / x=0.5; zy=1.0; a / x=2.0.

[0191] To more clearly explain the technical solution of this disclosure, this disclosure also provides examples 2-6 of negative electrode plates, wherein the setting parameters of examples 2-6 are shown in Table 1.

[0192] 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 2-6 are basically the same as those of embodiment 1.

[0193] Table 1. Setting parameters for the negative electrode sheet in Examples 1-6

[0194]

[0195] Example 8: A negative electrode sheet is prepared by the following method:

[0196] (1) A first effective component is obtained by mixing 60.5% of the negative electrode active material, 23.2% of the first conductive agent, and 16.3% of the first binder. The negative electrode active material comprises a first porous carbon material matrix and a first nano-silicon material, with a mass ratio of 2.3:1 between the first porous carbon material matrix and the first nano-silicon material. The first effective component is then mixed with a first solvent to obtain a first active material.

[0197] (2) Mix 64.8% of the second graphite, 4.7% of the hard carbon, 0.5% of the second nano-silicon material, 13.0% of the second conductive agent, and 17.0% 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.

[0198] (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.

[0199] (4) The electrode intermediate is cold-pressed to obtain the negative electrode.

[0200] The first thickness H1 of the first active material layer is 20.3 μm, the second thickness H2 of the second active material layer is 5.5 μm, and the ratio of the first thickness H1 to the second thickness H2 is 3.7.

[0201] The third thickness H3 of the first active material layer after cold pressing is 15.5 μm; the second active material layer after cold pressing has a fourth thickness H4, which is 5.2 μm.

[0202] The first weight m1 per unit volume of the first active substance layer is 40.4 mg / cc; the second weight m2 per unit volume of the second active substance layer is 9.6 mg / cc.

[0203] To more clearly explain the technical solution of this disclosure, this disclosure also provides examples 8-12 of negative electrode plates, wherein the setting parameters of examples 8-12 are shown in Table 2.

[0204] 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 8-12 are basically the same as those of embodiment 7.

[0205] Table 2. Setting parameters for the negative electrode sheet in Examples 7-12

[0206]

[0207] Example 13: A negative electrode sheet is prepared by the following method:

[0208] (1) The matrix material and the aromatic -COOR polymer are mixed at a temperature of 50°C so that the aromatic -COOR polymer is uniformly coated on the surface of the matrix material to form a polymer coating layer.

[0209] (2) A first effective component is obtained by mixing 60.5% of the negative electrode active material, 23.2% of the first conductive agent, and 16.3% of the first binder. The negative electrode active material matrix material and the aromatic -COOR-containing polymer are present. The matrix material includes a first porous carbon material matrix and a first nano-silicon material, with a mass ratio of 2.3:1 between the first porous carbon material matrix and the first nano-silicon material. The aromatic -COOR-containing polymer accounts for 1.8% of the mass of the matrix material.

[0210] (3) The first effective component is mixed with the first solvent to obtain the first active material.

[0211] (4) 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 the electrode intermediate.

[0212] (5) The electrode intermediate is cold-pressed to obtain the negative electrode.

[0213] To more clearly explain the technical solution of this disclosure, this disclosure also provides examples 14-17 of negative electrode plates, wherein the setting parameters of examples 14-17 are shown in Table 3.

[0214] 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 14-17 are basically the same as those of embodiment 13.

[0215] Table 3. Setting parameters for the negative electrode sheet in Examples 13-17

[0216]

[0217] Example 18: A negative electrode sheet is prepared by the following method:

[0218] (1) Mix the matrix material and aramid at a temperature of 200-500℃ to uniformly coat the surface of the matrix material with aramid to form a polymer coating layer.

[0219] (2) A first effective component is obtained by mixing 60.5% of the negative electrode active material, 23.2% of the first conductive agent, and 16.3% of the first binder. The negative electrode active material matrix material and aramid fiber are included. The matrix material comprises a first porous carbon material matrix and a first nano-silicon material, with a mass ratio of 2.3:1 between the first porous carbon material matrix and the first nano-silicon material. The thickness of the aramid fiber is 1.2% of the thickness of the matrix material.

[0220] (3) The first effective component is mixed with the first solvent to obtain the first active material.

[0221] (4) 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 the electrode intermediate.

[0222] (5) The electrode intermediate is cold-pressed to obtain the negative electrode.

[0223] The first particle size Dv50 of the first porous carbon material matrix is ​​5.0 μm;

[0224] The second particle size Dv50 of the first nano-silicon material is 5.0 nm;

[0225] The particle spacing of the first nanometer silicon material is 1.0 nm;

[0226] The specific surface area of ​​the first porous carbon material matrix is ​​4.5 m². 2 / g;

[0227] The porosity of the first porous carbon material matrix is ​​43.4%;

[0228] The first nano-silicon material has a filling degree of 38.5% in the first porous carbon material matrix.

[0229] To more clearly explain the technical solution of this disclosure, this disclosure also provides examples 19-23 of negative electrode plates, wherein the setting parameters of examples 19-23 are shown in Table 4.

[0230] Table 4 shows specific embodiments of the negative electrode sheet in this disclosure. It should be noted that, except for the parameters listed in Table 4, the other parameters of embodiments 19-23 are basically the same as those of embodiment 18.

[0231] Table 4. Setting parameters for the negative electrode sheet in Examples 18-23

[0232]

[0233] Application examples

[0234] 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.

[0235] In the electrolytes of Examples 7-23, the content of carboxylic acid ester (methyl formate) was 27.0%; the content of linear carbonate (dimethyl carbonate) was 48.5%; the content of cyclic ester (ethylene carbonate) was 8.5%; the content of ether compound (dibutyl ether) was 12.4%; the content of nitrile compound (acrylonitrile) was 3.6%; and the viscosity of the electrolyte was 0.05 cp.

[0236] Performance testing

[0237] 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 5.

[0238] Application Examples 1-23 correspond to Examples 1-23, respectively.

[0239] Table 5 Performance Test Table of Battery and Negative Electrode in Application Examples

[0240]

[0241] Table 5 (continued) Performance test table of battery and negative electrode in application examples

[0242]

[0243] Table 5 (continued) Performance test table of battery and negative electrode in application examples

[0244] Application Example 19 Application Example 20 Application Example 21 Application Example 22 Application Example 23 Energy density, Wh / kg 961 977 980 991 1000 Cycle life 1600 1600 1600 1600 1600 Safety performance pass pass pass pass pass Resistance, Mω 15.5 27.1 22.4 26.7 11.5 Voltage, V 4.5 4.5 4.5 4.5 4.5

[0245] As can be seen from the data in Table 5, the lithium-ion battery prepared using the negative electrode sheet disclosed herein has an energy density ≥700Wh / kg, a cycle life ≥1600 cycles, a voltage ≥4.50V, and a resistance ≤30MΩ. It has passed the safety performance test, indicating that the battery has good overall performance.

[0246] 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.

[0247] 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 active material, characterized in that, The negative electrode active material includes a matrix material, which includes a first carbon material and a first silicon-based material in a first preset ratio.

2. The negative electrode active material according to claim 1, characterized in that, The first preset ratio is 2.3-199.0:

1.

3. The negative electrode active material according to claim 1, wherein the first carbon material comprises a first porous carbon material matrix; and the first silicon-based material comprises a first nano-silicon material; The first nano-silicon material is deposited in the pores of the first porous carbon material matrix.

4. The negative electrode active material according to claim 3, characterized in that, The negative electrode active material further includes a polymer coating layer, which coats the surface of the matrix material.

5. The negative electrode active material according to claim 4, characterized in that, The polymer coating layer comprises an aromatic -COOR-containing polymer, wherein the aromatic -COOR-containing polymer is a polymer or a salt thereof with the following structural formula, and the structural formula of the aromatic -COOR polymer is shown in general formula (I): Wherein, R1 is selected from H, Li or Na; R2 is selected from hydrogen, sulfonic acid group, hydroxyl group, amino group or thiol.

6. The negative electrode active material according to claim 5, characterized in that... The aromatic -COOR-containing polymer is selected from... At least one of them.

7. The negative electrode active material according to claim 5, characterized in that... The aromatic -COOR-containing polymer accounts for 1.8-7.2% of the mass of the matrix material.

8. The negative electrode active material according to claim 4, characterized in that, The polymer coating layer includes a high-temperature resistant fiber material; The high-temperature resistant fiber material includes aramid.

9. The negative electrode active material according to claim 8, characterized in that, The specific surface area of ​​the first porous carbon material matrix is ​​2.2-12.3 m². 2 / g; and / or The porosity of the first porous carbon material matrix is ​​38.5-83.2%; and / or The filling degree of the first nano-silicon material in the first porous carbon material matrix is ​​38.5-83.2%; and / or The first particle size Dv50 of the first porous carbon material matrix is ​​5.0-10.5 μm; and / or The second particle size Dv50 of the first nano-silicon material is 5.0-82.5 nm; and / or The particle spacing of the first nano-silicon material is 1.0-23.5 nm.

10. The negative electrode active material according to claim 8, characterized in that, The thickness of the polymer coating layer is 1.2-5.8% of the thickness of the matrix material.

11. A negative electrode sheet, characterized in that, The negative electrode sheet includes a negative current collector and a first active material layer disposed on at least one side of the negative current collector. The first active material layer includes a first active material material, which includes a first effective component. The first effective component includes the negative electrode active material as described in any one of claims 1-10.

12. The negative electrode sheet according to claim 11, characterized in that, The negative electrode sheet further includes a second active material layer, which is disposed on the side of the first active material layer away from the positive current collector. The second active material layer includes a second active material, and the second active material includes a second effective component; When the battery is fully charged, the first active material layer has a first thickness H1, and the second active material layer has a second thickness H2. The first thickness H1 and the second thickness H2 satisfy the following relationship: 1.3≤H1 / H2≤6.

6.

13. The negative electrode sheet according to claim 12, characterized in that, The first active material layer has a third thickness H3 after cold pressing, and the third thickness H3 is 15.5-52.4 μm; The first thickness H1 is 20.3-79.6 μm; The second active material layer has a fourth thickness H4 after cold pressing, and the fourth thickness H4 is 5.2-20.7 μm; The second thickness H2 is 5.5-25.5 μm; The first weight m1 per unit volume of the first active substance layer is 40.4-82.3 mg / cc; The second weight m2 per unit volume of the second active substance layer is 9.6-42.5 mg / cc.

14. The negative electrode sheet according to claim 12, characterized in that, The second effective component includes a second carbon material and a second silicon-based material in a second preset ratio; The second carbon material includes a second porous carbon material matrix; the second silicon-based material includes a second nano-silicon material; the second nano-silicon material is deposited in the pores of the second porous carbon material matrix.

15. The negative electrode sheet according to claim 14, characterized in that, When the first carbon material includes the first graphite, the orientation index of the first graphite is 5.2-21.5; When the second porous carbon material matrix includes a second graphite, the orientation index of the second graphite is 4.8-12.3; When the second porous carbon material matrix further includes hard carbon, the mass of the hard carbon accounts for 4.7-22.1% of the mass of the second effective component.

16. A lithium-ion battery, characterized in that, Includes the negative electrode sheet as described in any one of claims 11-15.

17. The lithium-ion battery according to claim 16, characterized in that, The lithium-ion battery also includes an electrolyte, which comprises linear carbonate, and the linear carbonate accounts for 10-70% of the total mass of the electrolyte.

18. The lithium-ion battery according to claim 16, characterized in that, The percentage of silicon mass in the first silicon-based material relative to the total mass of the first effective component is x; The width of the negative electrode sheet is y; The length of the inner pit of the isolation membrane is z; The silicon content x, the width y of the negative electrode sheet, and the pit length z of the separator membrane satisfy the following relationship: 0.5 ≤ y / x ≤ 2.0; 1.0≤zy≤1.

6.

19. The lithium-ion battery according to claim 18, characterized in that, The content 'a' of the linear carbonate and the content 'x' of the silicon satisfy the following relationship: 0.2 ≤ a / x ≤ 2.0; The silicon content x is 0.5-22.4%.

20. An electronic device, characterized in that, Including the lithium-ion battery as described in any one of claims 16-19.

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