Fast-charging negative pole piece, lithium ion battery and electric device

Abstract

The invention provides a fast-charging negative pole piece, a lithium ion battery and an electric device. A negative active material in a negative material layer of the fast-charging negative pole piece comprises a silicon-based material and a carbon-based material; based on the mass percentage of the negative electrode active material, the mass fraction of the silicon-based material in the negative electrode active material is 70-99.5 wt%, and the mass fraction of the carbon-based material in the negative electrode active material is 0.5-30 wt%. The negative electrode active material in the negative electrode material layer of the fast-charging negative electrode plate 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, so that the negative electrode material layer has relatively low surface density while relatively high gram volume and fast-charging performance of the negative electrode material layer are ensured; the lithium ion battery prepared by matching the fast-charging negative pole piece with the positive pole piece with relatively high surface density has relatively high energy density and also can realize high-rate charging; the fast-charging negative pole piece also has the advantages of low production cost and simple production process.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries and relates to a fast-charging negative electrode plate, and in particular to a fast-charging negative electrode plate, a lithium-ion battery and an electric device. Background Art

[0002] Lithium-ion batteries are developing rapidly in different industries. In order to meet the demand for 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. The design method of the negative electrode sheet of traditional fast-charging batteries mainly improves the kinetic performance of the negative electrode sheet by selecting fast-charging graphite materials, reducing the surface density of the negative electrode sheet, and increasing the content of the conductive agent. However, the higher the rate capability of graphite, the lower its gram capacity. Therefore, in order to achieve higher fast charging capability, the battery energy density must be sacrificed.

[0003] In order to solve the shortcomings of traditional fast-charging battery pole piece design methods, double-layer or multi-layer coating technology has begun to appear. Different active materials are selected for each layer. For example, energy-biased materials that can achieve high compaction are used near the current collector layer, and materials with good fast charging capabilities are used away from the current collector layer to achieve higher energy density while maintaining good fast charging capabilities. In addition, laser grooving is used to expand the lithium ion migration path, thereby improving the fast charging capability. However, the fast-charging battery pole pieces prepared by these new process technologies have a complex structure and a high preparation cost, which is not conducive to large-scale promotion and use in production practice.

[0004] CN117410545A discloses a fast-charge high-energy density lithium-ion battery and its application, wherein the lithium-ion battery comprises a positive electrode, a negative electrode, a separator and an electrolyte, wherein the negative electrode comprises a negative electrode current collector and a negative electrode slurry coating applied on the negative electrode current collector, wherein the negative electrode slurry coating comprises a negative electrode active material, wherein the negative electrode active material comprises graphite mixed with silicon oxygen or graphite mixed with silicon carbon, wherein the particle size of the graphite is 5-20 μm, the particle size of the silicon oxygen or silicon carbon is 4-15 μm, and the content of the silicon oxygen or silicon carbon is 0-33.3% based on the total mass of the negative electrode active material, and the rest is graphite. However, the fast-charge performance of the fast-charge 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, a preparation method thereof and a lithium ion battery, wherein the composite negative electrode sheet comprises: a negative electrode current collector; a first active material coating applied to at least one surface of the negative electrode current collector; and a second active material coating applied to the outer surface of the first active material coating; wherein the compaction density of the first active material coating is greater than the compaction density of the second active material coating. However, the structure of the composite negative electrode sheet is complex and the preparation cost is high.

[0006] The fast-charging negative electrode plates disclosed in the prior art all have certain defects, such as insufficient fast-charging performance, complex structure and high manufacturing cost. Therefore, it is very important to develop and design a new type of fast-charging negative electrode plate, lithium-ion battery and electric device. Summary of the invention

[0007] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a fast-charging negative electrode plate, 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 plate provided by the present invention includes silicon-based materials and carbon-based materials, and the silicon-based material is the main component of the negative electrode active material, which ensures that the negative electrode material layer has a high gram capacity and fast charging performance while making the negative electrode material layer have a low surface density and compaction density. The lithium-ion battery prepared by combining the fast-charging negative electrode plate with a positive electrode plate with a high surface density has a high energy density and can also achieve high-rate charging. In addition, the fast-charging negative electrode plate in 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.

[0008] To achieve this object, the present invention adopts the following technical solutions:

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

[0010] Taking the mass of the negative electrode active material as 100%, the mass fraction of the silicon-based material in the negative electrode active material is 70wt% to 99.5wt%, and the mass fraction of the carbon-based material is 0.5wt% to 30wt%.

[0011] In the present invention, the mass fraction of the 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, and other values ​​not listed within the numerical range are also applicable.

[0012] In the present invention, the mass fraction of 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, and other values ​​not listed within the numerical range are also applicable.

[0013] The negative electrode active materials in the negative electrode material layer of the fast-charging negative electrode plate provided by the present invention include silicon-based materials and carbon-based materials, and the silicon-based materials are the main components of the negative electrode active materials, which ensures that the negative electrode material layer has a high gram capacity and fast charging performance while making the negative electrode material layer have a low surface density and compaction density. The lithium-ion battery prepared by combining the fast-charging negative electrode plate with a positive electrode plate with a high surface density has a high energy density and can also achieve high-rate charging. In addition, the fast-charging negative electrode plate in 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.

[0014] Preferably, the surface density of the fast-charging negative electrode sheet is ≤70g / m 2 , compacted density ≤1.4g / cm 3 .

[0015] The surface density of the fast-charging negative electrode sheet in the present invention is ≤70g / m 2 , for example, it can 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 , but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0016] The compaction density of the fast-charging negative electrode sheet of the present invention is ≤1.4g / cm 3 , for example, it can be 1.4 g / cm 3 , 1.3g / cm 3 , 1.2g / cm 3, 1.1g / 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 , but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0017] The gram capacity of the fast-charging negative electrode sheet described in the present 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 is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0018] Preferably, the fast-charging negative electrode plate 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 of silicon nanoparticles, silicon carbon materials, and silicon oxides, or a combination of at least two of them. Typical but non-limiting combinations include a combination of silicon nanoparticles and silicon carbon materials, a combination of silicon carbon materials and silicon oxides, or a combination of silicon nanoparticles, silicon carbon materials and silicon oxides.

[0020] Preferably, the D50 particle size of the silicon-carbon material is 2 to 18 μm, for example, 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, 16 μm or 18 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

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

[0022] Preferably, the carbon-based material includes any one of hard carbon, graphite or soft carbon or a combination of at least two of them. 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, 5 μm, 8 μm, 10 μm, 15 μm, 20 μm or 25 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

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

[0025] Preferably, the negative electrode material layer also 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 remainder is a binder.

[0027] In the present invention, the mass fraction of 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, and other unlisted values ​​within the numerical range are also applicable.

[0028] In the present invention, 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, and other unlisted values ​​within the numerical 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 of conductive carbon black, acetylene black, Ketjen black, conductive graphite or graphene, or a combination of at least two of them. 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 is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

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

[0034] Preferably, the average particle size of the Ketjen black is 10 nm to 100 nm, for example, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm or 100 nm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

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

[0036] Preferably, the average flake size of the graphene is 2 μm to 15 μm, for example, 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, 12 μm, 14 μm or 15 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

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

[0038] Preferably, the aspect ratio of the carbon nanotubes is 500-10000, 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, and other unlisted values ​​within the numerical range are also applicable.

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

[0040] Preferably, the molecular weight of the polyvinylidene fluoride is 500,000 to 2 million, for example, 500,000, 800,000, 1 million, 1.2 million, 1.4 million, 1.6 million, 1.8 million or 2 million, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

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

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

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

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

[0045] Preferably, the molecular weight of the polyacrylic acid is 100,000 to 1,000,000, for example, 100,000, 200,000, 300,000, 400,000, 500,000, 600,000, 700,000, 800,000, 900,000 or 1,000,000, but is not limited to the listed values, and other unlisted values ​​within the numerical 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 plate and the fast-charging negative electrode plate described in the first aspect;

[0047] The surface density of the positive electrode sheet is ≥120g / m 2 , compacted density ≤4.25g / cm 3 ;

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

[0049] The charging rate of the lithium-ion battery is ≥6C.

[0050] The surface density of the positive electrode sheet in the present invention is ≥120g / m 2 , for example, it can 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 , but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0051] The compaction density of the positive electrode sheet in the present invention is ≤4.25g / cm 3 , for example, it can be 4.25g / cm 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 , but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

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

[0053] The charging rate of the lithium-ion battery described in the present invention is ≥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, and other unlisted values ​​within the numerical range are also applicable.

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

[0055] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists 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 materials in the negative electrode material layer of the fast-charging negative electrode plate provided by the present invention include silicon-based materials and carbon-based materials, and the silicon-based materials are the main components of the negative electrode active materials, which ensures that the negative electrode material layer has a high gram capacity and fast charging performance while making the negative electrode material layer have a low surface density and compaction density. The lithium-ion battery prepared by combining the fast-charging negative electrode plate with a positive electrode plate with a high surface density has a high energy density and can also achieve high-rate charging. In addition, the fast-charging negative electrode plate in 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. DETAILED DESCRIPTION

[0058] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0059] Example 1

[0060] This embodiment provides a fast-charging negative electrode plate, the surface density of which is 45 g / m 2 , compacted density is 1.4g / cm 3 , gram capacity is 1200mAh / g;

[0061] The fast-charging negative electrode plate also includes a negative current collector and a negative electrode material layer covered on both sides of the negative current collector, wherein 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 comprises a silicon-based material (a silicon-carbon material with a D50 particle size of 10 μm) and a carbon-based material (a hard carbon with a D50 particle size of 15 μm). Based on the mass of the negative electrode active material, the mass fraction of the silicon-based material in the negative electrode active material is 85wt%, and the mass fraction of the carbon-based material is 15wt%;

[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 binder includes polyvinylidene fluoride with a molecular weight of 1.2 million.

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

[0066] The surface density of the positive electrode sheet is 210 g / m 2 , compacted density is 3.4g / cm 3 , gram capacity is 210mAh / g;

[0067] The charging rate of the lithium-ion battery is ≥6C.

[0068] Example 2

[0069] This embodiment provides a fast-charging negative electrode plate, the surface density of the fast-charging negative electrode plate is 35g / m 2 , compacted density is 1.4g / cm 3 , gram capacity is 1200mAh / g;

[0070] The fast-charging negative electrode plate also includes a negative current collector and a negative electrode material layer covered on both sides of the negative current collector, wherein 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 comprises a silicon-based material (silicon oxide with a D50 particle size of 2 μm) and a carbon-based material (graphite with a D50 particle size of 25 μm), and based on the mass of the negative electrode active material, the mass fraction of the silicon-based material in the negative electrode active material is 70wt%, and the mass fraction of the carbon-based material is 30wt%;

[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 binder includes polyimide with a molecular weight of 100,000.

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

[0075] The surface density of the positive electrode sheet is 160g / m 2 , compacted density is 3.4g / cm 3 , gram capacity is 210mAh / g;

[0076] The charging rate of the lithium-ion battery is ≥6C.

[0077] Example 3

[0078] This embodiment provides a fast-charging negative electrode plate, the surface density of which is 70 g / m 2 , compacted density is 1.4g / cm 3 , gram capacity is 1200mAh / g;

[0079] The fast-charging negative electrode plate also includes a negative current collector and a negative electrode material layer covered on both sides of the negative current collector, wherein 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 98wt%, the mass fraction of the conductive agent is 0.02wt%, and the remainder is a binder;

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

[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 binder includes polyacrylonitrile with a molecular weight of 1 million.

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

[0084] The surface density of the positive electrode sheet is 345g / m 2 , compacted density is 3.4g / cm 3 , gram capacity is 210mAh / g;

[0085] The charging rate of the lithium-ion battery is ≥6C.

[0086] Example 4

[0087] This embodiment provides a fast-charging negative electrode plate, except that the surface density of the fast-charging negative electrode plate is 100g / m 2 , compacted density is 1.4g / cm 3 Except that the gram capacity is 1200 mAh / g, the rest are the same as those in Example 1.

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

[0089] Example 5

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

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

[0092] Example 6

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

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

[0095] Example 7

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

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

[0098] Example 8

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

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

[0101] Example 9

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

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

[0104] Example 10

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

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

[0107] Embodiment 11

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

[0109] This embodiment also provides a lithium-ion battery, except that the surface density of the positive electrode sheet of the lithium-ion battery is 100g / m 2 , compacted density 3.4g / cm 3 , except that the gram capacity is not less than 1200 mAh / g, the rest is the same as Example 1.

[0110] Comparative Example 1

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

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

[0113] The energy density of the lithium-ion batteries provided in the above embodiments and comparative examples was tested, and the testing method was: the total electrical energy density of the lithium battery = battery discharge energy / battery weight; the test method of discharge energy: charge to 4.35V at 0.2C constant current and constant voltage, and then discharge to 2.5V at 0.2C, cycle for 3 weeks, and obtain the discharge energy. The total electrical energy density is 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 testing method is: a battery testing system is used to perform charge and discharge tests on the obtained lithium-ion batteries. The test voltage range is 2.5 to 4.35 V. The 10C rate performance of the lithium-ion batteries obtained by the test is shown in Table 1.

[0115] Table 1

[0116]

[0117]

[0118] From Table 1, we can get:

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

[0120] (2) By comparing Example 1 with Example 4, it can be seen that the surface density of the fast-charging negative electrode sheet in the present invention will affect the performance of the lithium-ion battery; when the surface density of the fast-charging negative electrode sheet is ≤70g / m 2 When the surface density of the electrode is smaller, the coating is thinner, and the distribution consistency of lithium ion concentration in the thickness direction is better, thereby reducing the transmission impedance. The performance of the lithium ion battery is improved with the positive electrode with a larger surface density.

[0121] (3) By comparing Example 1 with Examples 5 and 6, it can be seen that the particle size of the silicon-based material in the present invention affects the performance of the lithium-ion battery; when the particle size of the silicon-based material is too low or too high, the performance of the lithium-ion battery will deteriorate. This is because when the particle size is too low, the processing performance of the silicon-based material will be insufficient, and the side reactions will increase, thereby causing the performance of the fast-charging negative electrode sheet and the lithium-ion battery to deteriorate; when the particle size is too high, the kinetic performance of the silicon-based material will be reduced, thereby causing the performance of the fast-charging negative electrode sheet and the lithium-ion battery to deteriorate;

[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 the present 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, and the side reactions will increase, thereby causing the performance of the fast-charging negative electrode sheet and the lithium-ion battery to deteriorate; if the particle size is too high, the kinetic performance of the carbon-based material will be reduced, thereby causing the performance of the fast-charging negative electrode sheet and the lithium-ion battery to 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 agents, it is beneficial to improve the performance of the lithium ion battery. This is because when the conductive agent is two different types of conductive agents, the integrity of the conductive network can be improved, so that the active particles contain point, line and surface contacts, and the failure of the conductive network caused by the expansion of the silicon-based material is reduced;

[0124] (6) By comparing Example 1 with Example 11, it can be seen that when the surface of the positive electrode sheet is ≥120g / m 2 When the positive electrode is charged, the lithium-ion battery shows a better energy density. This is because the larger the positive electrode surface density, the more it can cooperate with the fast-charging negative electrode with a stronger rate performance, thereby improving the overall energy density of the battery, so that the battery has a higher energy density and excellent rate performance.

[0125] (7) By comparing Example 1 with 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 plate provided by the present invention includes silicon-based materials and carbon-based materials, and the silicon-based material is the main component of the negative electrode active material, which ensures that the negative electrode material layer has a high gram capacity and fast charging performance while making the negative electrode material layer have a low surface density and compaction density. The lithium-ion battery prepared by combining the fast-charging negative electrode plate with a positive electrode plate with a high surface density has a high energy density and can also achieve high-rate charging. In addition, the fast-charging negative electrode plate in 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 implementation mode 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 thought of by those skilled in the art within the technical scope disclosed by the present invention are within the protection scope and disclosure scope of the present invention.

Claims

1. A fast-charging negative electrode plate, characterized in that: The negative electrode active material in the negative electrode material layer of the fast-charging negative electrode plate includes silicon-based materials and carbon-based materials; Taking the mass of the negative electrode active material as 100%, the mass fraction of the silicon-based material in the negative electrode active material is 70wt% to 99.5wt%, and the mass fraction of the carbon-based material is 0.5wt% to 30wt%.

2. The fast-charging negative electrode sheet according to claim 1, characterized in that: The surface density of the fast-charging negative electrode plate is ≤70g / m 2 , compacted density ≤1.4g / cm 3 ; Preferably, the gram capacity of the fast-charging negative electrode plate is not less than 1200 mAh / g.

3. The fast-charging negative electrode sheet according to claim 1 or 2, 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; Preferably, the D50 particle size of the silicon-carbon material is 2 to 18 μm; Preferably, the D50 particle size of the silicon oxide is 2 to 18 μm.

4. The fast-charging negative electrode sheet according to any one of claims 1 to 3, characterized in that: The carbon-based material includes any one of hard carbon, graphite or soft carbon, or a combination of at least two thereof; Preferably, the D50 particle size of the hard carbon is 5 to 25 μm; Preferably, the D50 particle size of the graphite is 5 to 25 μm.

5. The fast-charging negative electrode sheet according to any one of claims 1 to 4, characterized in that: The negative electrode material layer also includes a conductive agent and a binder; 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 remainder is a binder.

6. The fast-charging negative electrode plate according to claim 5, characterized in that: The conductive agent includes a first conductive agent and a second conductive agent; The first conductive agent includes any one of conductive carbon black, acetylene black, Ketjen black, conductive graphite or graphene, or a combination of at least two thereof; The second conductive agent includes carbon fibers and / or carbon nanotubes.

7. The fast-charging negative electrode sheet according to claim 6, characterized in that: The average particle size of the conductive carbon black is 10nm to 100nm; Preferably, the average particle size of the acetylene black is 10 nm to 100 nm; Preferably, the average particle size of the Ketjen black is 10nm to 100nm; Preferably, the average particle size of the conductive graphite is 2 μm to 15 μm; Preferably, the average sheet diameter of the graphene is 2 μm to 15 μm; Preferably, the aspect ratio of the carbon fiber is 40 to 100; Preferably, the aspect ratio of the carbon nanotubes is 500-10000.

8. The fast-charging negative electrode sheet according to any one of claims 5 to 7, characterized in that: The binder includes any one or a combination of at least two of polyvinylidene fluoride, polyimide, polyacrylonitrile, styrene-butadiene rubber, carboxymethyl cellulose or polyacrylic acid; Preferably, the molecular weight of the polyvinylidene fluoride is 500,000 to 2,000,000; Preferably, the molecular weight of the polyimide is 100,000 to 1,000,000; Preferably, the molecular weight of the polyacrylonitrile is 100,000 to 1,000,000; Preferably, the molecular weight of the styrene-butadiene rubber is 100,000 to 800,000; Preferably, the molecular weight of the carboxymethyl cellulose is 100,000 to 1,000,000; Preferably, the molecular weight of the polyacrylic acid is 100,000 to 1,000,000.

9. A lithium ion battery, characterized in that: The lithium-ion battery comprises a positive electrode plate and a fast-charging negative electrode plate as claimed in any one of claims 1 to 8; The surface density of the positive electrode sheet is ≥120g / m 2 , compacted density ≤4.25g / cm 3 ; The gram capacity of the positive electrode sheet is not less than 140 mAh / g; The charging rate of the lithium-ion battery is ≥6C.

10. An electric device, characterized in that: The electric device includes the lithium-ion battery of claim 9.

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