A fast-charging negative electrode sheet, a lithium ion battery and an electric device

Abstract

The application provides a fast-charging negative electrode sheet, a lithium ion battery and an electric device. The negative electrode active material in the negative electrode material layer of the fast-charging negative electrode sheet comprises a silicon-based material and a carbon-based material. The mass fraction of the silicon-based material in the negative electrode active material is 70wt%-99.5wt%, and the mass fraction of the carbon-based material in the negative electrode active material is 0.5wt%-30wt%, with the mass of the negative electrode active material being 100%. The negative electrode active material in the negative electrode material layer of the fast-charging negative electrode sheet comprises the silicon-based material and the carbon-based material, and the silicon-based material is the main component of the negative electrode active material, which ensures that the negative electrode material layer has high specific capacity and fast-charging performance, and at the same time, the negative electrode material layer has low surface density. The lithium ion battery prepared by matching the fast-charging negative electrode sheet with a positive electrode sheet with high surface density has high energy density and can also realize high-rate charging. The fast-charging negative electrode sheet also has the advantages of low production cost and simple production process.

Description

Technical Field

[0001] This invention belongs to the field of battery technology and relates to a fast-charging negative electrode sheet, and more particularly to a fast-charging negative electrode sheet, a lithium-ion battery, and an electric device. Background Technology

[0002] Lithium-ion batteries are rapidly developing across various industries. To meet the demands for extended battery life, the requirements for energy density and fast-charging performance are constantly increasing. The improvement of fast-charging capability is closely related to the design of the negative electrode. Traditional fast-charging battery negative electrode design primarily improves the kinetic performance of the negative electrode by selecting fast-charging graphite materials, reducing the areal density of the negative electrode, and increasing the content of conductive agents. However, the higher the rate capability of graphite, the lower its specific capacity. Therefore, to achieve higher fast-charging capabilities, the battery energy density must be sacrificed.

[0003] To address the shortcomings of traditional fast-charging battery electrode designs, dual-layer or multi-layer coating techniques have emerged. Each layer uses different active materials; for example, a high-energy-density material is used near the current collector layer, while a material with good fast-charging capabilities is used further away, achieving both high energy density and good fast-charging performance. Additionally, laser grooving is used to extend the lithium-ion migration path, thereby improving fast-charging performance. However, these new technologies result in complex structures and high manufacturing costs for fast-charging battery electrodes, hindering large-scale adoption in production.

[0004] CN117410545A discloses a fast-charging high-energy-density lithium-ion battery and its application. The lithium-ion battery includes a positive electrode, a negative electrode, a separator, and an electrolyte. The negative electrode includes a negative electrode current collector and a negative electrode slurry coating coated on the negative electrode current collector. The negative electrode slurry coating includes a negative electrode active material, which is graphite mixed with silicon oxide or graphite mixed with silicon carbon. The particle size of the graphite is 5-20 μm, and the particle size of the silicon oxide or silicon carbon is 4-15 μm. Based on the total mass of the negative electrode active material, the content of silicon oxide or silicon carbon is 0-33.3%, with the remainder being graphite. However, the fast-charging performance of this fast-charging high-energy-density lithium-ion battery is still insufficient, and the rate performance of the prepared lithium-ion battery is low.

[0005] CN117810358A discloses a composite negative electrode sheet, its preparation method, and a lithium-ion battery. The composite negative electrode sheet includes: a negative electrode current collector; a first active material coating coated on at least one surface of the negative electrode current collector; and a second active material coating coated on the outer surface of the first active material coating. The compaction density of the first active material coating is greater than that of the second active material coating. However, this composite negative electrode sheet has a complex structure and high manufacturing cost.

[0006] Existing fast-charging negative electrode sheets all have certain drawbacks, including insufficient fast-charging performance, complex structure, and high manufacturing cost. Therefore, it is crucial to develop and design a novel fast-charging negative electrode sheet, lithium-ion battery, and electric device. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a fast-charging negative electrode sheet, a lithium-ion battery, and an electric device. The negative electrode active material in the negative electrode material layer of the fast-charging negative electrode sheet provided by the present invention includes silicon-based and carbon-based materials, with silicon-based materials being the main component. This ensures that the negative electrode material layer has high specific capacity and fast-charging performance while maintaining low areal density and compaction density. A lithium-ion battery prepared using this fast-charging negative electrode sheet in conjunction with a positive electrode sheet having high areal density can achieve high-rate charging while maintaining high energy density. Furthermore, the fast-charging negative electrode sheet of the present invention has a simple structure and uses common raw materials, thus offering advantages such as low production cost and simple manufacturing process.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a fast-charging negative electrode sheet, wherein the negative electrode active material in the negative electrode material layer of the fast-charging negative electrode sheet includes silicon-based materials and carbon-based materials;

[0010] Based on the mass of the negative electrode active material, the mass fraction of silicon-based material in the negative electrode active material is 70wt% to 99.5wt%, and the mass fraction of carbon-based material is 0.5wt% to 30wt%.

[0011] In this invention, the mass of the negative electrode active material is taken as 100%. The mass fraction of silicon-based material in the negative electrode active material is 70wt% to 99.5wt%, for example, it can be 70wt%, 71wt%, 72wt%, 73wt%, 74wt%, 75wt%, 76wt%, 77wt%, 78wt%, 79wt%, 80wt%, 82wt%, 84wt%, 86wt%, 88wt%, 90wt%, 92wt%, 94wt%, 96wt%, 98wt%, 99wt%, 99.2wt%, or 99.5wt%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0012] In this invention, the mass of the negative electrode active material is taken as 100%. The mass fraction of carbon-based material in the negative electrode active material is 0.5wt% to 30wt%, for example, it can be 0.5wt%, 0.7wt%, 1wt%, 2wt%, 4wt%, 6wt%, 8wt%, 10wt%, 12wt%, 14wt%, 16wt%, 18wt%, 20wt%, 22wt%, 24wt%, 26wt%, 28wt%, or 30wt%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0013] The negative electrode active material in the negative electrode material layer of the fast-charging negative electrode sheet provided by this invention includes silicon-based materials and carbon-based materials, with silicon-based materials being the main component of the negative electrode active material. This ensures that the negative electrode material layer has high specific capacity and fast-charging performance, while also giving it low areal density and compaction density. The lithium-ion battery prepared by combining the fast-charging negative electrode sheet with a positive electrode sheet having high areal density can achieve high-rate charging while having high energy density. In addition, the fast-charging negative electrode sheet of this invention has a simple structure and uses common raw materials, thus also having the advantages of low production cost and simple production process.

[0014] Preferably, the areal density of the fast-charging negative electrode sheet is ≤70g / m³. 2 Compacted density ≤1.4g / cm³ 3 .

[0015] The areal density of the fast-charging negative electrode sheet described in this invention is ≤70g / m². 2 For example, it could be 70g / m 2 68g / m 2 65g / m 2 62g / m 2 60g / m 2 58g / m 2 55g / m 2 52g / m 2 50g / m 2 48g / m 2 45g / m 2 42g / m 2 or 40g / m 2 However, this does not apply to all values ​​listed; other unlisted values ​​within the same range also apply.

[0016] The compaction density of the fast-charging negative electrode sheet described in this invention is ≤1.4 g / cm³. 3 For example, it could be 1.4 g / cm³. 3 1.3g / cm 3 1.2g / cm 31.1g / cm 3 1.0g / cm 3 0.9g / cm 3 0.8g / cm 3 0.7g / cm 3 0.6g / cm 3 0.5g / cm 3 0.4g / cm 3 0.3g / cm 3 or 0.2g / cm 3 However, this does not apply to all values ​​listed; other unlisted values ​​within the same range also apply.

[0017] The specific capacity of the fast-charging negative electrode sheet described in this invention is not less than 1200mAh / g, for example, it can be 1200mAh / g, 1300mAh / g, 1400mAh / g, 1500mAh / g, 1600mAh / g, 1800mAh / g, 2000mAh / g, 2200mAh / g, 2500mAh / g, 2800mAh / g or 3000mAh / g, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0018] Preferably, the fast-charging negative electrode sheet further includes a negative electrode current collector, and the negative electrode material layer is disposed on at least one side surface of the negative electrode current collector.

[0019] Preferably, the silicon-based material includes any one or a combination of at least two of silicon nanoparticles, silicon carbon materials, and silicon oxides. Typical but non-limiting combinations include combinations of silicon nanoparticles and silicon carbon materials, combinations of silicon carbon materials and silicon oxides, or combinations of silicon nanoparticles, silicon carbon materials, and silicon oxides.

[0020] Preferably, the D50 particle size of the silicon carbide material is 2 to 18 μm, for example, it can be 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, 16 μm or 18 μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0021] Preferably, the D50 particle size of the silicon oxide is 2 to 18 μm, for example, it can be 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, 16 μm or 18 μm, but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0022] Preferably, the carbon-based material includes any one or a combination of at least two of hard carbon, graphite, or soft carbon. Typical but non-limiting combinations include a combination of hard carbon and graphite, a combination of graphite and soft carbon, or a combination of hard carbon, graphite, and soft carbon.

[0023] Preferably, the D50 particle size of the hard carbon is 5 to 25 μm, for example, it can be 5 μm, 8 μm, 10 μm, 15 μm, 20 μm or 25 μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0024] Preferably, the D50 particle size of the graphite is 5 to 25 μm, for example, it can be 5 μm, 8 μm, 10 μm, 15 μm, 20 μm or 25 μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0025] Preferably, the negative electrode material layer further includes a conductive agent and a binder.

[0026] Preferably, based on the mass of the negative electrode material layer, the mass fraction of the negative electrode active material in the negative electrode material layer is 90wt% to 98wt%, the mass fraction of the conductive agent is 0.02wt% to 8wt%, and the balance is binder.

[0027] In this invention, the mass of the negative electrode material layer is taken as 100%. The mass fraction of the negative electrode active material in the negative electrode material layer is 90wt% to 98wt%, for example, it can be 90wt%, 91wt%, 92wt%, 93wt%, 94wt%, 95wt%, 96wt%, 97wt%, or 98wt%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0028] In this invention, the mass of the negative electrode material layer is taken as 100%. The mass fraction of the conductive agent in the negative electrode material layer is 0.02wt% to 8wt%, for example, it can be 0.02wt%, 0.05wt%, 0.08wt%, 0.1wt%, 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, or 8wt%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0029] Preferably, the conductive agent includes a first conductive agent and a second conductive agent.

[0030] The first conductive agent includes any one or a combination of at least two of conductive carbon black, acetylene black, Ketjen black, conductive graphite, or graphene. Typical but non-limiting combinations include a combination of conductive carbon black and acetylene black, a combination of acetylene black and Ketjen black, a combination of conductive graphite and graphene, or a combination of conductive carbon black, acetylene black, and Ketjen black.

[0031] The second conductive agent includes carbon fibers and / or carbon nanotubes.

[0032] Preferably, the average particle size of the conductive carbon black is 10nm to 100nm, for example, it can be 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm or 100nm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0033] Preferably, the average particle size of the acetylene black is 10nm to 100nm, for example, it can be 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm or 100nm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0034] Preferably, the average particle size of the Ketjenblack is 10nm to 100nm, for example, it can be 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm or 100nm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0035] Preferably, the average particle size of the conductive graphite is 2μm to 15μm, for example, it can be 2μm, 4μm, 6μm, 8μm, 10μm, 12μm, 14μm or 15μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0036] Preferably, the average sheet diameter of the graphene is 2μm to 15μm, for example, it can be 2μm, 4μm, 6μm, 8μm, 10μm, 12μm, 14μm or 15μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0037] Preferably, the aspect ratio of the carbon fiber is 40 to 100, for example, it can be 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 or 100, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0038] Preferably, the aspect ratio of the carbon nanotubes is 500 to 10000, for example, it can be 500, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000, 5500, 6000, 6500, 7000, 7500, 8000, 8500, 9000, 9500 or 10000, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0039] Preferably, the adhesive comprises any one or a combination of at least two of polyvinylidene fluoride, polyimide, polyacrylonitrile, styrene-butadiene rubber, carboxymethyl cellulose, or polyacrylic acid. Typical but non-limiting combinations include combinations of polyvinylidene fluoride and polyimide, combinations of polyimide and polyacrylonitrile, combinations of styrene-butadiene rubber and carboxymethyl cellulose, combinations of carboxymethyl cellulose and polyacrylic acid, or combinations of polyvinylidene fluoride, polyimide, and polyacrylonitrile.

[0040] Preferably, the molecular weight of the polyvinylidene fluoride is between 500,000 and 2,000,000, for example, it can be 500,000, 800,000, 1,000,000, 1,200,000, 1,400,000, 1,600,000, 1,800,000 or 2,000,000, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0041] Preferably, the molecular weight of the polyimide is between 100,000 and 1,000,000, for example, it can be 100,000, 200,000, 300,000, 400,000, 500,000, 600,000, 700,000, 800,000, 900,000 or 1,000,000, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0042] Preferably, the molecular weight of the polyacrylonitrile is between 100,000 and 1,000,000, for example, it can be 100,000, 200,000, 300,000, 400,000, 500,000, 600,000, 700,000, 800,000, 900,000 or 1,000,000, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0043] Preferably, the molecular weight of the styrene-butadiene rubber is between 100,000 and 800,000, for example, it can be 100,000, 200,000, 300,000, 400,000, 500,000, 600,000, 700,000 or 800,000, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0044] Preferably, the molecular weight of the carboxymethyl cellulose is between 100,000 and 1,000,000, for example, it can be 100,000, 200,000, 300,000, 400,000, 500,000, 600,000, 700,000, 800,000, 900,000 or 1,000,000, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0045] Preferably, the molecular weight of the polyacrylic acid is between 100,000 and 1,000,000, for example, it can be 100,000, 200,000, 300,000, 400,000, 500,000, 600,000, 700,000, 800,000, 900,000 or 1,000,000, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0046] In a second aspect, the present invention provides a lithium-ion battery, the lithium-ion battery comprising a positive electrode and the fast-charging negative electrode as described in the first aspect;

[0047] The areal density of the positive electrode sheet is ≥120 g / m³. 2 Compacted density ≤ 4.25 g / cm³ 3 ;

[0048] The specific capacity of the positive electrode sheet is not less than 140mAh / g;

[0049] The lithium-ion battery has a charging rate ≥6C.

[0050] The areal density of the positive electrode sheet described in this invention is ≥120 g / m². 2 For example, it could be 120g / m 2 130g / m 2 140g / m 2 150g / m 2 160g / m 2 170g / m 2 180g / m 2 190g / m 2 Or 200g / m 2 However, this does not apply to all values ​​listed; other unlisted values ​​within the same range also apply.

[0051] The compacted density of the positive electrode sheet described in this invention is ≤4.25 g / cm³. 3 For example, it could be 4.25 g / cm³ 3 4.2g / cm 3 4.15g / cm 3 4.1g / cm 3 4.05g / cm 3 4.00g / cm 3 2.95g / cm 3 3.9g / cm 3 Or 3.8g / cm 3 However, this does not apply to all values ​​listed; other unlisted values ​​within the same range also apply.

[0052] The specific capacity of the positive electrode sheet described in this invention is not less than 140 mAh / g, for example, it can be 140 mAh / g, 150 mAh / g, 160 mAh / g, 180 mAh / g, 200 mAh / g, 220 mAh / g, 240 mAh / g or 260 mAh / g, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0053] The lithium-ion battery described in this invention has a charging rate ≥6C, for example, it can be 6C, 6.1C, 6.2C, 6.3C, 6.4C, 6.5C, 6.8C, 7C, 7.5C, 8C, 8.5C or 9C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0054] Thirdly, the present invention provides an electric device comprising the lithium-ion battery described in the second aspect.

[0055] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0056] Compared with the prior art, the present invention has the following beneficial effects:

[0057] The negative electrode active material in the negative electrode material layer of the fast-charging negative electrode sheet provided by this invention includes silicon-based materials and carbon-based materials, with silicon-based materials being the main component of the negative electrode active material. This ensures that the negative electrode material layer has high specific capacity and fast-charging performance, while also giving it low areal density and compaction density. The lithium-ion battery prepared by combining the fast-charging negative electrode sheet with a positive electrode sheet having high areal density can achieve high-rate charging while having high energy density. In addition, the fast-charging negative electrode sheet of this invention has a simple structure and uses common raw materials, thus also having the advantages of low production cost and simple production process. Detailed Implementation

[0058] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0059] Example 1

[0060] This embodiment provides a fast-charging negative electrode sheet, the areal density of which is 45 g / m³. 2 The compacted density is 1.4 g / cm³. 3 The capacity is 1200mAh / g;

[0061] The fast-charging negative electrode sheet also includes a negative electrode current collector and a negative electrode material layer covering both sides of the negative electrode current collector. The negative electrode material layer includes a negative electrode active material, a conductive agent, and a binder. Based on the mass of the negative electrode material layer, the mass fraction of the negative electrode active material in the negative electrode material layer is 92wt%, the mass fraction of the conductive agent is 4wt%, and the remainder is a binder.

[0062] The negative electrode active material includes silicon-based material (silicon-carbon material with a D50 particle size of 10 μm) and carbon-based material (hard carbon with a D50 particle size of 15 μm). Based on the mass of the negative electrode active material, the mass fraction of silicon-based material in the negative electrode active material is 85 wt%, and the mass fraction of carbon-based material is 15 wt%.

[0063] The conductive agent includes a first conductive agent (conductive carbon black with an average particle size of 50 nm) and a second conductive agent (carbon fiber with an aspect ratio of 70).

[0064] The adhesive comprises polyvinylidene fluoride with a molecular weight of 1.2 million.

[0065] This embodiment also provides a lithium-ion battery, which includes a positive electrode and the fast-charging negative electrode described in this embodiment.

[0066] The areal density of the positive electrode sheet is 210 g / m³. 2 The compacted density is 3.4 g / cm³. 3 The capacity is 210mAh / g;

[0067] The lithium-ion battery has a charging rate ≥6C.

[0068] Example 2

[0069] This embodiment provides a fast-charging negative electrode sheet with an areal density of 35 g / m³. 2 The compacted density is 1.4 g / cm³. 3 The capacity is 1200mAh / g;

[0070] The fast-charging negative electrode sheet also includes a negative electrode current collector and a negative electrode material layer covering both sides of the negative electrode current collector. The negative electrode material layer includes a negative electrode active material, a conductive agent, and a binder. Based on the mass of the negative electrode material layer, the mass fraction of the negative electrode active material in the negative electrode material layer is 92wt%, the mass fraction of the conductive agent is 4wt%, and the remainder is a binder.

[0071] The negative electrode active material includes silicon-based material (silicon oxide with a D50 particle size of 2 μm) and carbon-based material (graphite with a D50 particle size of 25 μm). Based on the mass of the negative electrode active material, the mass fraction of silicon-based material in the negative electrode active material is 70 wt%, and the mass fraction of carbon-based material is 30 wt%.

[0072] The conductive agent includes a first conductive agent (acetylene black with an average particle size of 100 nm) and a second conductive agent (carbon nanotubes with an aspect ratio of 500).

[0073] The adhesive comprises polyimide with a molecular weight of 100,000.

[0074] This embodiment also provides a lithium-ion battery, which includes a positive electrode and the fast-charging negative electrode described in this embodiment.

[0075] The areal density of the positive electrode sheet is 160 g / m³. 2 The compacted density is 3.4 g / cm³. 3 The capacity is 210mAh / g;

[0076] The lithium-ion battery has a charging rate ≥6C.

[0077] Example 3

[0078] This embodiment provides a fast-charging negative electrode sheet, the areal density of which is 70 g / m³. 2 The compacted density is 1.4 g / cm³. 3 The capacity is 1200mAh / g;

[0079] The fast-charging negative electrode sheet also includes a negative electrode current collector and a negative electrode material layer covering both sides of the negative electrode current collector. The negative electrode material layer includes a negative electrode active material, a conductive agent, and a binder. Based on the mass of the negative electrode material layer, the mass fraction of the negative electrode active material in the negative electrode material layer is 98 wt%, the mass fraction of the conductive agent is 0.02 wt%, and the remainder is a binder.

[0080] The negative electrode active material includes silicon-based material (silicon-carbon material with a D50 particle size of 18 μm) and carbon-based material (graphite with a D50 particle size of 5 μm). Based on the mass of the negative electrode active material, the mass fraction of silicon-based material in the negative electrode active material is 99.5 wt%, and the mass fraction of carbon-based material is 0.5 wt%.

[0081] The conductive agent includes a first conductive agent (Ketjen Black with an average particle size of 10 nm) and a second conductive agent (carbon nanotubes with an aspect ratio of 10000).

[0082] The adhesive comprises polyacrylonitrile with a molecular weight of 1 million.

[0083] This embodiment also provides a lithium-ion battery, which includes a positive electrode and the fast-charging negative electrode described in this embodiment.

[0084] The areal density of the positive electrode sheet is 345 g / m³. 2 The compacted density is 3.4 g / cm³. 3 The capacity is 210mAh / g;

[0085] The lithium-ion battery has a charging rate ≥6C.

[0086] Example 4

[0087] This embodiment provides a fast-charging negative electrode sheet, except that the areal density of the fast-charging negative electrode sheet is 100g / m³. 2 The compacted density is 1.4 g / cm³. 3 Except for the capacity of 1200mAh / g, it is the same as in Example 1.

[0088] This embodiment also provides a lithium-ion battery, except that the negative electrode of the lithium-ion battery is the fast-charging negative electrode of this embodiment, and everything else is the same as in embodiment 1.

[0089] Example 5

[0090] This embodiment provides a fast-charging negative electrode sheet, which is the same as that in Example 1 except that the particle size of the silicon-carbon material is 1μm.

[0091] This embodiment also provides a lithium-ion battery, except that the negative electrode of the lithium-ion battery is the fast-charging negative electrode of this embodiment, and everything else is the same as in embodiment 1.

[0092] Example 6

[0093] This embodiment provides a fast-charging negative electrode sheet, which is the same as that in Example 1 except that the particle size of the silicon-carbon material is 25μm.

[0094] This embodiment also provides a lithium-ion battery, except that the negative electrode of the lithium-ion battery is the fast-charging negative electrode of this embodiment, and everything else is the same as in embodiment 1.

[0095] Example 7

[0096] This embodiment provides a fast-charging negative electrode sheet, which is the same as that in Example 1 except that the particle size of the hard carbon is 4μm.

[0097] This embodiment also provides a lithium-ion battery, except that the negative electrode of the lithium-ion battery is the fast-charging negative electrode of this embodiment, and everything else is the same as in embodiment 1.

[0098] Example 8

[0099] This embodiment provides a fast-charging negative electrode sheet, which is the same as that in Example 1 except that the particle size of the hard carbon is 35μm.

[0100] This embodiment also provides a lithium-ion battery, except that the negative electrode of the lithium-ion battery is the fast-charging negative electrode of this embodiment, and everything else is the same as in embodiment 1.

[0101] Example 9

[0102] This embodiment provides a fast-charging negative electrode sheet, which is the same as in Example 1 except that the first conductive agent (conductive carbon black with an average particle size of 50 nm) is replaced with an equal mass of the second conductive agent (carbon fiber with an aspect ratio of 70).

[0103] This embodiment also provides a lithium-ion battery, except that the negative electrode of the lithium-ion battery is the fast-charging negative electrode of this embodiment, and everything else is the same as in embodiment 1.

[0104] Example 10

[0105] This embodiment provides a fast-charging negative electrode sheet, which is the same as in Example 1 except that the second conductive agent (carbon fiber with an aspect ratio of 70) is replaced with the same mass of the first conductive agent (conductive carbon black with an average particle size of 50nm).

[0106] This embodiment also provides a lithium-ion battery, except that the negative electrode of the lithium-ion battery is the fast-charging negative electrode of this embodiment, and everything else is the same as in embodiment 1.

[0107] Example 11

[0108] This embodiment provides a fast-charging negative electrode sheet, which is the same as that in Embodiment 1.

[0109] This embodiment also provides a lithium-ion battery, wherein the areal density of the positive electrode sheet of the lithium-ion battery is 100 g / m². 2 Compacted density 3.4 g / cm³ 3 Except for the capacity of not less than 1200mAh / g, everything else is the same as in Example 1.

[0110] Comparative Example 1

[0111] This comparative example provides a fast-charging negative electrode sheet, which is the same as in Example 1 except that the mass fraction of silicon-based material in the negative electrode active material is 60 wt% and the mass fraction of carbon-based material is 40 wt%.

[0112] This comparative example also provides a lithium-ion battery, except that the negative electrode of the lithium-ion battery is the fast-charging negative electrode of this comparative example, and everything else is the same as in Example 1.

[0113] The energy density of the lithium-ion batteries provided in the above embodiments and comparative examples was tested. The test method was as follows: the total energy density of the lithium battery = battery discharge energy / battery weight; the discharge energy test method was as follows: charge at 0.2C constant current and constant voltage to 4.35V, then discharge at 0.2C to 2.5V, cycle for 3 weeks, and obtain the discharge energy. The total energy density was calculated as shown in Table 1.

[0114] The rate performance of the lithium-ion batteries provided in the above embodiments and comparative examples was tested. The test method was as follows: the lithium-ion batteries were charged and discharged using a battery testing system with a test voltage range of 2.5 to 4.35V. The 10C rate performance of the lithium-ion batteries was obtained as shown in Table 1.

[0115] Table 1

[0116]

[0117]

[0118] From Table 1, we can obtain:

[0119] (1) The lithium-ion batteries provided in Examples 1 to 3 have high rate performance and still maintain high energy density;

[0120] (2) A comparison between Example 1 and Example 4 shows that the areal density of the fast-charging negative electrode sheet in this invention affects the performance of the lithium-ion battery; when the areal density of the fast-charging negative electrode sheet is ≤70g / m³, the performance of the lithium-ion battery is affected. 2 At this time, lithium-ion batteries exhibit superior performance because the smaller the electrode surface density, the thinner the coating, and the better the uniformity of lithium-ion concentration distribution in the thickness direction, thereby reducing transmission impedance. Combined with a positive electrode with a larger surface density, this improves the performance of lithium-ion batteries.

[0121] (3) By comparing Example 1 with Examples 5 and 6, it can be seen that the particle size of silicon-based materials in this invention affects the performance of lithium-ion batteries. When the particle size of silicon-based materials is too low or too high, the performance of lithium-ion batteries will deteriorate. This is because if the particle size is too low, the processing performance of silicon-based materials will be insufficient, and the side reactions will increase, thereby resulting in a deterioration in the performance of fast-charging negative electrode sheets and lithium-ion batteries. If the particle size is too high, the kinetic performance of silicon-based materials will be reduced, thereby resulting in a deterioration in the performance of fast-charging negative electrode sheets and lithium-ion batteries.

[0122] (4) By comparing Example 1 with Examples 7 and 8, it can be seen that the particle size of the carbon-based material in this invention affects the performance of the lithium-ion battery. When the particle size of the carbon-based material is too low or too high, the performance of the lithium-ion battery will deteriorate. This is because if the particle size is too low, the processing performance of the carbon-based material will be insufficient, the side reactions will increase, and thus the performance of the fast-charging negative electrode and the lithium-ion battery will deteriorate. If the particle size is too high, the kinetic performance of the carbon-based material will be reduced, thus the performance of the fast-charging negative electrode and the lithium-ion battery will deteriorate.

[0123] (5) By comparing Example 1 with Examples 9 and 10, it can be seen that when the conductive agent in the present invention is two different types of conductive agent, it is beneficial to improve the performance of lithium-ion battery. This is because when the conductive agent is two different types of conductive agent, it can improve the integrity of the conductive network, make the active particles contain point, line and surface contact, and reduce the failure of the conductive network caused by the expansion of silicon-based material.

[0124] (6) A comparison between Example 1 and Example 11 shows that when the surface area of ​​the positive electrode sheet is ≥120g / m 2 At that time, lithium-ion batteries exhibit superior energy density. This is because the larger the surface density of the positive electrode, the better it can be combined with the fast-charging negative electrode with strong rate performance, thereby improving the overall energy density of the battery and enabling the battery to have both high energy density and excellent rate performance.

[0125] (7) By comparing Example 1 and Comparative Example 1, it can be seen that the negative electrode active material in the negative electrode material layer of the fast-charging negative electrode sheet provided by the present invention includes silicon-based material and carbon-based material, and the silicon-based material is the main component of the negative electrode active material. This ensures that the negative electrode material layer has a high specific capacity and fast-charging performance, while also making the negative electrode material layer have a low areal density and compaction density. The lithium-ion battery prepared by combining the fast-charging negative electrode sheet with a positive electrode sheet with a high areal density has a high energy density and can also achieve high-rate charging. In addition, the fast-charging negative electrode sheet of the present invention has a simple structure and the raw materials are common materials, so it also has the advantages of low production cost and simple production process.

[0126] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A lithium-ion battery, characterized in that, The lithium-ion battery includes a positive electrode and a fast-charging negative electrode. The negative electrode active material in the negative electrode material layer of the fast-charging negative electrode sheet includes silicon-based materials and carbon-based materials; Based on the mass of the negative electrode active material, the mass fraction of silicon-based material in the negative electrode active material is 70wt%~99.5wt%, and the mass fraction of carbon-based material is 0.5wt%~30wt%. The areal density of the fast-charging negative electrode sheet is 35 g / m³. 2 ~70g / m 2 ; The areal density of the positive electrode sheet is 160 g / m³. 2 ~345g / m 2 ; The compacted density of the positive electrode sheet is ≤4.25 g / cm³. 3 ; The specific capacity of the positive electrode sheet is not less than 140mAh / g; The lithium-ion battery has a charging rate ≥6C.

2. The lithium-ion battery according to claim 1, characterized in that, The compaction density of the fast-charging negative electrode sheet is ≤1.4g / cm³. 3 .

3. The lithium-ion battery according to claim 1, characterized in that, The specific capacity of the fast-charging negative electrode sheet is not less than 1200mAh / g.

4. The lithium-ion battery according to claim 1, characterized in that, The silicon-based material includes any one or a combination of at least two of silicon nanoparticles, silicon-carbon materials, or silicon oxides.

5. The lithium-ion battery according to claim 4, characterized in that, The D50 particle size of the silicon-carbon material is 2~18μm.

6. The lithium-ion battery according to claim 4, characterized in that, The D50 particle size of the silicon oxide is 2~18μm.

7. The lithium-ion battery according to claim 1, characterized in that, The carbon-based material includes any one or a combination of at least two of hard carbon, graphite, or soft carbon.

8. The lithium-ion battery according to claim 7, characterized in that, The D50 particle size of the hard carbon is 5~25μm.

9. The lithium-ion battery according to claim 7, characterized in that, The D50 particle size of the graphite is 5~25μm.

10. The lithium-ion battery according to any one of claims 1 to 9, characterized in that, The negative electrode material layer also includes a conductive agent and a binder.

11. The lithium-ion battery according to claim 10, characterized in that, Based on the mass of the negative electrode material layer, the mass fraction of the negative electrode active material in the negative electrode material layer is 90wt%~98wt%, the mass fraction of the conductive agent is 0.02wt%~8wt%, and the balance is binder.

12. According to claims 10 The lithium-ion battery described above is characterized in that, The conductive agent includes a first conductive agent and a second conductive agent; The first conductive agent includes any one or a combination of at least two of conductive carbon black, conductive graphite, or graphene. The second conductive agent includes carbon fibers and / or carbon nanotubes.

13. The lithium-ion battery according to claim 12, characterized in that, The average particle size of the conductive carbon black is 10 nm to 100 nm.

14. The lithium-ion battery according to claim 12, characterized in that, The conductive carbon black includes acetylene black, and the average particle size of the acetylene black is 10 nm to 100 nm.

15. The lithium-ion battery according to claim 12, characterized in that, The conductive carbon black includes Ketjen black, and the average particle size of the Ketjen black is 10 nm to 100 nm.

16. The lithium-ion battery according to claim 12, characterized in that, The average particle size of the conductive graphite is 2μm~15μm.

17. The lithium-ion battery according to claim 12, characterized in that, The average sheet size of the graphene is 2μm~15μm.

18. The lithium-ion battery according to claim 12, characterized in that, The aspect ratio of the carbon fiber is 40 to 100.

19. The lithium-ion battery according to claim 12, characterized in that, The aspect ratio of the carbon nanotubes is 500 to 10000.

20. The lithium-ion battery according to claim 10, characterized in that, The adhesive comprises any one or a combination of at least two of polyvinylidene fluoride, polyimide, polyacrylonitrile, styrene-butadiene rubber, carboxymethyl cellulose, or polyacrylic acid.

21. The lithium-ion battery according to claim 20, characterized in that, The molecular weight of the polyvinylidene fluoride is 500,000 to 2,000,000.

22. The lithium-ion battery according to claim 20, characterized in that, The polyimide has a molecular weight of 100,000 to 1,000,000.

23. The lithium-ion battery according to claim 20, characterized in that, The molecular weight of the polyacrylonitrile is 100,000 to 1,000,000.

24. The lithium-ion battery according to claim 20, characterized in that, The molecular weight of the styrene-butadiene rubber is 100,000 to 800,000.

25. The lithium-ion battery according to claim 20, characterized in that, The molecular weight of the carboxymethyl cellulose is 100,000 to 1,000,000.

26. The lithium-ion battery according to claim 20, characterized in that, The molecular weight of the polyacrylic acid is 100,000 to 1,000,000.

27. An electric device, characterized in that, The electric device includes the lithium-ion battery as described in any one of claims 1 to 26.

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