Secondary battery and power consuming device

Abstract

The present application provides a secondary battery and a power consuming device. The negative electrode sheet of the secondary battery includes a negative electrode current collector and a negative electrode film layer, the negative electrode film layer includes a first surface away from the negative electrode current collector and a second surface facing the first surface, the thickness of the negative electrode film layer is H, a region within a thickness range of 0.3H from the second surface of the negative electrode film layer is a first region of the negative electrode film layer, and a region within a thickness range of 0.3H from the first surface of the negative electrode film layer is a second region of the negative electrode film layer, the first region includes a first active material, the second region includes a second active material, the first active material includes a first carbon-based material, the second active material includes a second carbon-based material, the first carbon-based material has a pore structure, and the I of the first carbon-based material is a pore structure. D / I G is the second carbon-based material I D / I G In the present application, on the premise that the secondary battery has a high energy density, it is possible to achieve both good dynamic performance and storage performance. Figure 1

Description

[Technical field]

[0001] The present application relates to the technical field of batteries, and more particularly to secondary batteries and power consuming devices. [Background technology]

[0002] In recent years, secondary batteries have been widely applied in many fields, such as energy storage power systems such as hydroelectric, thermal, wind and solar power plants, electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. As the application range of secondary batteries becomes wider and wider, serious challenges have been raised for the performance of secondary batteries, for example, secondary batteries are required to balance various performances such as energy density, dynamic performance and service life. However, the challenge faced in the prior art is that it is often difficult to balance the energy density of secondary batteries when improving the dynamic performance of secondary batteries, and the dynamic performance and service life of secondary batteries are often affected when improving the energy density of secondary batteries. Summary of the Invention

[0003] The present application has been made in consideration of the above-mentioned problems, and its purpose is to provide a secondary battery and a power consumption device that can achieve both good dynamic performance and storage performance while having a high energy density.

[0004] A first aspect of the present application is a secondary battery including a negative electrode sheet, the negative electrode sheet including a negative electrode current collector and a negative electrode film layer formed on at least one surface of the negative electrode current collector, the negative electrode film layer including a first surface away from the negative electrode current collector and a second surface provided opposite to the first surface, the thickness of the negative electrode film layer is H, a region within a thickness range of 0.3H from the second surface of the negative electrode film layer is a first region of the negative electrode film layer, and a region within a thickness range of 0.3H from the first surface of the negative electrode film layer is a second region of the negative electrode film layer, the first region includes a first active material, the second region includes a second active material, the first active material includes a first carbon-based material, the second active material includes a second carbon-based material, the first carbon-based material has a pore structure, and a pore size of the first carbon-based material is I. D / I G is the second carbon-based material I D / I G smaller than I D is 1350±50cm in the Raman spectrum. -1 The D peak intensity at I G is 1580±50 cm in the Raman spectrum. -1 The present invention provides a secondary battery exhibiting a G peak intensity at

[0005] In the study, the inventors have found that a first region of a negative electrode film layer includes a first carbon-based material, a second region includes a second carbon-based material, the first carbon-based material has a pore structure, and the I D / I G The second carbon-based material I D / I G It has been discovered that by making the negative electrode sheet smaller than 0.1 mm in diameter, the negative electrode sheet can have a high compression density, high active ion transport performance, and high surface stability, and thus the secondary battery can have both good kinetic performance and storage performance under the premise of having a high energy density.

[0006] In any embodiment of the present application, I of the second carbon-based material D / I G I of the first carbon-based material D / I GThe ratio A is 0.80 or less, and can be selected from 0.32 to 0.77. When α is within the above range, it is advantageous to achieve good dynamic performance and storage performance on the premise that the secondary battery has a high energy density.

[0007] In any embodiment of the present application, I of the first carbon-based material D / I G is 0.152 to 0.280, and optionally 0.155 to 0.220. D / I G When is within the above range, the first carbon-based material has a small amount of disordered carbon, a high gram capacity (capacity per gram) and high chemical stability, thereby reducing the occurrence of side reactions and improving the energy density and storage performance of the secondary battery.

[0008] In any embodiment of the present application, I of the second carbon-based material D / I G is 0.230-0.500, optionally 0.235-0.450. D / I G When the second carbon-based material is within the above range, its active ion transport performance is better, which is advantageous for improving the dynamic performance of the secondary battery.

[0009] In any embodiment of the present application, the volume distribution particle diameter Dv50 of the second carbon-based material is smaller than the volume distribution particle diameter Dv50 of the first carbon-based material, which is advantageous for the first and second regions of the negative electrode membrane layer to have a suitable pore distribution, and can improve the compression density of the negative electrode membrane layer and the energy density of the secondary battery, while improving the impregnation and retention properties of the negative electrode membrane layer with respect to the electrolyte and reducing the expansion of the negative electrode sheet, thereby improving the storage performance and / or cycle performance of the secondary battery.

[0010] In any embodiment of the present application, the second carbon-based material has a powder compression density at a pressure of 20,000 N that is smaller than the powder compression density of the first carbon-based material at a pressure of 20,000 N. By adjusting the powder compression density of the second carbon-based material to be smaller than the powder compression density of the first carbon-based material, it is advantageous to improve the energy density of the secondary battery, while it is advantageous for the first and second regions of the negative electrode membrane layer to have a suitable pore distribution, thereby improving the impregnation and retention properties of the negative electrode membrane layer with respect to the electrolyte, and improving the kinetic performance and / or cycle performance of the secondary battery.

[0011] In any embodiment of the present application, the second carbon-based material comprises at least one of synthetic graphite and natural graphite, and optionally, the second carbon-based material comprises natural graphite.

[0012] In any embodiment of the present application, the first carbon-based material does not have a diffraction peak of 3R phase 012 plane in the X-ray diffraction spectrum, so that the first carbon-based material particles have few internal defects, which can further reduce the occurrence of side reactions and the irreversible consumption of active ions, thereby improving the initial coulombic efficiency and storage performance of the secondary battery.

[0013] In any embodiment of the present application, the second carbon-based material has a diffraction peak of a 3R phase 012 plane in an X-ray diffraction spectrum.

[0014] In any embodiment of the present application, the second carbon-based material has a pore structure.

[0015] In any embodiment of the present application, the second carbon-based material has a particle size of 0.15 μm 2 and optionally, one or more pore structures having a pore area of ​​0.15 μm or more. 2 ~2.0μm 2 The porous structure includes one or more pore structures having a pore area of

[0016] In any embodiment of the present application, the ratio of the pore area in the cross section of the first carbon-based material particle to the cross-sectional area of ​​the first carbon-based material particle is α1 and the ratio of the pore area in the cross section of the second carbon-based material particle to the cross-sectional area of ​​the second carbon-based material particle is α 2 And α 1 <α 2 It is.

[0017] In any embodiment of the present application, the first carbon-based material has a particle size of 0.15 μm 2 and optionally, one or more pore structures having a pore area of ​​0.15 μm or more. 2 ~2.0μm 2 When the first carbon-based material includes a pore structure having the above pore area, the pore structure can ensure an expansion space required for the volume change of the particles, thereby further reducing the risk of new interfaces being generated due to particle crushing, further reducing the occurrence of side reactions, and improving the storage performance of the secondary battery.

[0018] In any embodiment of the present application, the first carbon-based material includes an outer region and an inner region located inside the outer region, the outer region is a region extending from the surface of the first carbon-based material particle to the inside of the particle by a distance of 0.25L, L being the minor axis length of the first carbon-based material particle, and the total pore area of ​​the outer region is defined as S 1 The total pore area of ​​the inner region is S 2 And S 2 >S 1 The first carbon-based material is S 2 >S 1 Further, when the above condition is satisfied, the initial coulombic efficiency of the secondary battery can be improved, and the storage performance and / or cycle performance of the secondary battery can be further improved.

[0019] In any embodiment of the present application, 1.5≦S 2 / S 1 ≦500, selectable 2≦S 2 / S 1 ≦450. 2 / S 1 When the content of the carbon nanotube is within the above range, the secondary battery can more suitably achieve both high energy density and good storage performance.

[0020] In any embodiment of the present application, the area of ​​the pore structure in the outer region of the first carbon-based material is less than or equal to 0.2 μm 2 Selectable below 0.10μm 2 By controlling the area of ​​the pore structure in the outer region of the first carbon-based material within the above range, the outer region of the first carbon-based material can be made to have a dense structure, which effectively improves the structural stability of the first carbon-based material, prevents the electrolyte from penetrating into the pore structure inside the first carbon-based material particles as much as possible, reduces the occurrence of side reactions, and effectively improves the storage performance of the secondary battery.

[0021] In any embodiment of the present application, the inner region of the first carbon-based material may have a thickness of 0.15 μm 2 and optionally, one or more pore structures having an area of ​​0.15 μm or more. 2 ~2.0μm 2 Since the internal region of the first carbon-based material includes a pore structure of the above size, the pressure of the roll press of the negative electrode sheet can be effectively reduced, damage to the particles can be effectively reduced, and a sufficient and stable expansion space can be ensured for the volume change of the first carbon-based material particles, reducing the risk of crushing the first carbon-based material particles, while improving the compression density of the negative electrode film layer and improving the energy density of the secondary battery.

[0022] In any embodiment of the present application, the first carbon-based material and / or the second carbon-based material includes primary particles. When the first carbon-based material includes a suitable proportion of primary particles, it has high structural stability, reduces the occurrence of side reactions, and can improve the storage performance of the secondary battery, and can also improve the compression density of the negative electrode film layer, and can improve the energy density of the secondary battery. When the second carbon-based material includes a suitable proportion of primary particles, it has high structural stability, reduces the occurrence of side reactions, and can improve the storage performance of the secondary battery, and can also improve the compression density of the negative electrode film layer, and can improve the energy density of the secondary battery.

[0023] In any embodiment of the present application, the number percentage of the primary particles in the first carbon-based material is 50% or more.

[0024] In any embodiment of the present application, the number percentage of the primary particles in the second carbon-based material is 50% or more.

[0025] In any embodiment of the present application, at least a portion of the surface of the first carbon-based material and / or the second carbon-based material has a coating layer, optionally comprising carbon.

[0026] In any embodiment of the present application, the specific surface area of ​​the first carbon-based material is 2.1 m 2 / g or less, and selectable 1.1m 2 / g~2.0m 2 The first carbon-based material has a low specific surface area, which can reduce the consumption of active ions due to the formation of the SEI film and improve the initial coulombic efficiency and storage performance of the secondary battery.

[0027] In any embodiment of the present application, the first carbon-based material has a volume distribution particle size Dv50 of 8.0 μm to 25.0 μm, and optionally 10.0 μm to 22.0 μm.

[0028] In any embodiment of the present application, the first carbon-based material has a volume distribution particle size Dv90 of 16.0 μm to 45.0 μm, and optionally 16.5 μm to 42.0 μm.

[0029] When the volume distribution particle size Dv50 and / or Dv90 of the first carbon-based material is within the above range, it is advantageous to improve the transport performance of active ions and electrons, thereby further improving the dynamic performance of the secondary battery, and also to reduce the specific surface area of ​​the first carbon-based material, reduce the occurrence of side reactions, and improve the storage performance of the secondary battery.

[0030] In any embodiment of the present application, the particle size distribution (Dv90-Dv10) / Dv50 of the first carbon-based material is less than 1.55, and optionally ranges from 0.90 to 1.50. When the particle size distribution (Dv90-Dv10) / Dv50 of the first carbon-based material is within the above range, the particle deposition performance thereof is good, which is favorable for improving the compression density of the negative electrode membrane layer, thereby further improving the energy density of the secondary battery, and is also favorable for adjusting the pore distribution of the negative electrode membrane layer, thereby improving the dynamic performance of the secondary battery.

[0031] In any embodiment of the present application, the first carbon-based material has a powder compaction density of 1.65 g / cm at a pressure of 20,000 N. 3 ~2.0g / cm 3 and selectable 1.68g / cm 3 ~1.98g / cm 3 When the compression density of the powder of the first carbon-based material is within the above range, it is possible to improve the compression density of the negative electrode film layer, improve the energy density of the secondary battery, and form a reasonable channel structure between the particles of the negative electrode film layer, which is favorable for improving the transport performance of active ions and electrons, and improving the dynamic performance of the secondary battery.

[0032] In any embodiment of the present application, the first carbon-based material has a tap density of 0.85 g / cm 3 ~1.30g / cm 3 and can be selected from 0.90g / cm 3 ~1.25g / cm 3 When the tap density of the first carbon-based material is within the above range, it can improve the compression density of the negative electrode film layer, improve the energy density of the secondary battery, and form a reasonable channel structure between the particles of the negative electrode film layer, which is favorable for improving the transport performance of active ions and electrons, and further improving the dynamic performance of the secondary battery.

[0033] In any embodiment of the present application, the graphitization degree of the first carbon-based material is 95.5% or more, and optionally 95.5% to 98.0%, which is advantageous for improving the energy density of the secondary battery.

[0034] In any embodiment of the present application, the gram capacity of the first carbon-based material is 355mAh / g or more, and optionally 355mAh / g to 370mAh / g, which is advantageous for improving the energy density of the secondary battery.

[0035] In any embodiment of the present application, the first carbon-based material has a diffraction peak of the 3R phase 101 plane in the X-ray diffraction spectrum, which provides many active sites on the surface of the first carbon-based material, and is advantageous for rapid insertion and desorption of active ions.

[0036] In any embodiment of the present application, the adsorption amount of the first carbon-based material for 100 g of linseed oil is 30 ml to 47 mL. If the adsorption amount of the first carbon-based material for linseed oil is within the above range, it is advantageous for improving the storage performance and / or dynamic performance of the secondary battery.

[0037] In any embodiment of the present application, the specific surface area of ​​the second carbon-based material is 1.8 m 2 / g or more, selectable 1.9m 2 / g~3.5m 2 When the specific surface area of ​​the second carbon-based material is within the above range, it is advantageous for reducing the occurrence of side reactions and reducing the consumption of active ions due to the formation of the SEI film, so that the secondary battery can achieve both a high initial coulombic efficiency and good cycle performance and storage performance.

[0038] In any embodiment of the present application, the second carbon-based material has a Dv50 of 8.0 μm to 15.0 μm, and optionally 10.0 μm to 15.0 μm. If the volume distribution particle size Dv50 of the second carbon-based material is within the above range, it is advantageous to improve the transport performance of active ions and electrons, thereby further improving the dynamic performance of the secondary battery, and also reducing the specific surface area of ​​the second carbon-based material, reducing the occurrence of side reactions, and improving the storage performance of the secondary battery.

[0039] In any embodiment of the present application, the particle size distribution (Dv90-Dv10) / Dv50 of the second carbon-based material is less than 1.65, and optionally 0.90-1.65. When the particle size distribution (Dv90-Dv10) / Dv50 of the second carbon-based material is within the above range, the particle deposition performance is good, which is favorable for improving the compression density of the negative electrode membrane layer, thereby further improving the energy density of the secondary battery, and is also favorable for adjusting the pore distribution of the negative electrode membrane layer, thereby improving the dynamic performance of the secondary battery.

[0040] In any embodiment of the present application, the second carbon-based material has a powder compaction density of 1.60 g / cm at a pressure of 20,000 N. 3 ~1.95g / cm 3 and selectable 1.65g / cm 3 ~1.92g / cm 3 When the compressed density of the powder of the second carbon-based material is within the above range, it is possible to improve the compressed density of the negative electrode film layer, improve the energy density of the secondary battery, and also to form a reasonable channel structure between the particles of the negative electrode film layer, improve the active ion and electron transport performance, improve the impregnation and retention properties of the negative electrode film layer with respect to the electrolyte, and further to improve the kinetic performance and / or cycle performance of the secondary battery.

[0041] In any embodiment of the present application, the second carbon-based material has a tap density of 0.85 g / cm 3 ~1.25g / cm 3 and can be selected from 0.90g / cm 3 ~1.25g / cm 3 When the tap density of the second carbon-based material is within the above range, it is possible to improve the compression density of the negative electrode film layer, improve the energy density of the secondary battery, and also to form a reasonable channel structure between the particles of the negative electrode film layer, improve the active ion and electron transport performance, improve the electrolyte impregnation and retention properties of the negative electrode film layer, and further improve the dynamic performance of the secondary battery.

[0042] In any embodiment of the present application, the graphitization degree of the second carbon-based material is 94.5% to 98.0%, and optionally 95.0% to 97.5%. When the graphitization degree of the second carbon-based material is within the above range, it is advantageous to improve the active ion transport performance of the negative electrode film layer and also advantageous to improve the negative electrode capacity, so that the secondary battery can achieve both high energy density and good dynamic performance.

[0043] In any embodiment of the present application, the gram capacity of the second carbon-based material is 355mAh / g to 372mAh / g, and optionally 356mAh / g to 370mAh / g. When the gram capacity of the second carbon-based material is within the above range, the energy density of the secondary battery can be improved while the second carbon-based material can also have good active ion transport performance, which is advantageous for improving the dynamic performance of the secondary battery.

[0044] In any embodiment of the present application, the second carbon-based material has a diffraction peak of a 3R phase 101 plane in an X-ray diffraction spectrum.

[0045] In any embodiment of the present application, the first active material further comprises a third carbon-based material, and the third carbon-based material comprises primary particle form of artificial graphite. The combination of the first carbon-based material and the third carbon-based material is advantageous for the negative electrode film layer to have a suitable channel structure and for improving the active ion transport performance of the negative electrode film layer.

[0046] In any embodiment of the present application, the surface of the primary particle-form artificial graphite does not have a carbon coating layer. The primary particle-form artificial graphite has a stable surface, and when the surface does not have a carbon coating layer, it is advantageous to maintain its low side reaction activity and to reduce the occurrence of side reactions, which can further improve the cycle performance and storage performance of the secondary battery.

[0047] In any embodiment of the present application, the mass percentage of the third carbon-based material in the first active material is 80 wt% or less, and optionally 20 wt% to 70 wt%.

[0048] In any embodiment of the present application, the graphitization degree of the third carbon-based material is 92.5% to 95.5%, and optionally 92.7% to 95.5%. When the graphitization degree of the third carbon-based material is within the above range, it is favorable for improving the active ion transport performance of the negative electrode film layer, particularly the first region, and thus favorable for the secondary battery to achieve both high energy density and good dynamic performance.

[0049] In any embodiment of the present application, the third carbon-based material has a powder OI value of 4.5 to 11.5, and optionally 4.5 to 11.0. The third carbon-based material has a small powder OI value and has active ion insertion ports in all directions of the particles, which can quickly receive active ions from the positive electrode, and is therefore advantageous for further improving the dynamic performance of the secondary battery.

[0050] In any embodiment of the present application, the particle size distribution (Dv90-Dv10) / Dv50 of the third carbon-based material is less than 1.65, and optionally ranges from 0.90 to 1.65. When the particle size distribution (Dv90-Dv10) / Dv50 of the third carbon-based material is within the above range, the particle deposition performance thereof is good, which is favorable for improving the compression density of the negative electrode membrane layer, thereby further improving the energy density of the secondary battery, and is also favorable for adjusting the pore distribution of the negative electrode membrane layer, thereby improving the dynamic performance of the secondary battery.

[0051] In any embodiment of the present application, the third carbon-based material has a volume distribution particle size Dv50 of 12.0 μm to 22.0 μm, and optionally 13.5 μm to 20.0 μm. When the volume distribution particle size Dv50 of the third carbon-based material is within the above range, it is advantageous to improve the transport performance of active ions and electrons, thereby further improving the dynamic performance of the secondary battery, and also reducing the specific surface area of ​​the third carbon-based material, reducing the occurrence of side reactions, and improving the storage performance of the secondary battery.

[0052] In any embodiment of the present application, the third carbon-based material has a specific surface area of ​​1.0 m 2 / g~2.0m 2 / g, selectable 1.05m 2 / g~1.95m 2 The third carbon-based material has a low specific surface area, which can reduce the consumption of active ions due to the formation of the SEI film, reduce the occurrence of side reactions, and improve the initial coulombic efficiency and storage performance of the secondary battery.

[0053] In any embodiment of the present application, the third carbon-based material has a tap density of 0.95 g / cm 3 ~1.25g / cm 3 and can be selected from 1.00g / cm 3 ~1.25g / cm 3 When the tap density of the third carbon-based material is within the above range, it can improve the compression density of the negative electrode film layer, improve the energy density of the secondary battery, and form a reasonable channel structure between the particles of the negative electrode film layer, which is favorable for improving the transport performance of active ions and electrons, and further improving the dynamic performance of the secondary battery.

[0054] In any embodiment of the present application, the gram capacity of the third carbon-based material is 350mAh / g to 363mAh / g, and optionally 352mAh / g to 362mAh / g. When the gram capacity of the third carbon-based material is within the above range, the energy density of the secondary battery can be improved while the transport performance of the active ions of the negative electrode film layer can be improved, which is also advantageous for improving the dynamic performance of the secondary battery.

[0055] In any embodiment of the present application, the first region and / or the second region further comprises a silicon-based material, which plays a role in improving the channel structure in the negative electrode film layer, facilitating the impregnation and liquid retention of the electrolyte, improving the dynamic performance of the secondary battery, and improving the negative electrode capacity, thereby further improving the energy density of the secondary battery.

[0056] In any embodiment of the present application, the first region and the second region both contain a silicon-based material, and the mass ratio of the silicon-based material in the first region is equal to or less than the mass ratio of the silicon-based material in the second region, which is advantageous in improving the impregnation property of the negative electrode film layer with respect to the electrolyte, improving the transport performance of active ions, and improving the cycle performance and / or kinetic performance of the secondary battery.

[0057] In any embodiment of the present application, an intermediate region located between the first region and the second region includes the first active material and / or the second active material.

[0058] In any embodiment of the present application, the porosity of the negative electrode membrane layer is 18.0% to 36.7%, and optionally 19.0% to 34.0%, which is favorable for the negative electrode membrane layer to achieve both high capacity and a suitable channel structure, and is favorable for the secondary battery to achieve both high energy density and good storage performance and dynamic performance.

[0059] In any embodiment of the present application, the compressed density of the negative electrode film layer is 1.45 g / cm 3 ~1.90g / cm 3 and can be selected from 1.50g / cm 3 ~1.85g / cm 3 This is advantageous for the negative electrode film layer to have both high capacity and high active ion and electron transport performance, and is advantageous for the secondary battery to have both high energy density and good storage and dynamic performance.

[0060] In any embodiment of the present application, the areal density of the negative electrode film layer is 5.0 mg / cm 2 ~25.0mg / cm 2 and selectable at 5.5mg / cm 2 ~22.5mg / cm 2 This is advantageous for the negative electrode film layer to have both high capacity and high active ion and electron transport performance, and is advantageous for the secondary battery to have both high energy density and good storage and dynamic performance.

[0061] In any embodiment of the present application, the OI value of the negative electrode film layer is 45.0 or less, and optionally 8.0 to 45.0, which is advantageous for improving the insertion performance of active ions in the negative electrode film layer, and also for lowering the thickness repulsion rate of the negative electrode film layer, which is advantageous for the secondary battery to have both good storage performance and dynamic performance.

[0062] In any embodiment of the present application, the thickness of the negative electrode film layer is 60 μm or more, and optionally 70 μm to 250 μm.

[0063] A second aspect of the present application provides a power consuming device including the secondary battery of the first aspect of the present application.

[0064] The power consumption device of the present application includes the secondary battery of the present application and therefore has at least the same advantages as the secondary battery. [Brief description of the drawings]

[0065] In order to more clearly describe the technical solutions of the embodiments of the present application, the drawings required in the embodiments of the present application are briefly described below. It is obvious that the drawings described below are only some embodiments of the present application, and those skilled in the art can obtain other drawings based on the drawings without creative efforts. [Figure 1] FIG. 1 is a schematic diagram of one embodiment of a negative electrode sheet of the present application. [Diagram 2] FIG. 2 is a schematic diagram of another embodiment of the negative electrode sheet of the present application. [Diagram 3]FIG. 2 is a schematic diagram of yet another embodiment of the negative electrode sheet of the present application. [Figure 4] FIG. 2 is a schematic diagram of a cross-sectional image of one of the first carbon-based material particles of the present application. [Diagram 5] FIG. 1 is a schematic diagram of an embodiment of a secondary battery of the present application. [Figure 6] 1 is an exploded schematic view of an embodiment of a secondary battery of the present application. [Figure 7] FIG. 1 is a schematic diagram of one embodiment of a battery module of the present application. [Figure 8] FIG. 1 is a schematic diagram of one embodiment of a battery pack of the present application. [Figure 9] FIG. 9 is an exploded schematic view of the embodiment of the battery pack shown in FIG. 8. [Figure 10] 1 is a schematic diagram of one embodiment of a power consuming device that includes a secondary battery of the present application as a power source. [Explanation of symbols]

[0066] 1 battery pack 2 Upper housing 3 Lower housing 4 Battery Module 5 secondary battery 51 cases 52 Electrode Assembly 53 cover plate 10 Negative electrode sheet 101 Negative electrode current collector 102 Negative electrode film layer 102a 1st surface 102b 2nd surface 1021 1st area 1022 Second area 1023 Intermediate area 200 Carbon-based materials No. 1 201 external area 202 internal area DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0067] Hereinafter, with reference to the drawings as appropriate, detailed descriptions will be given of embodiments specifically disclosing the secondary battery and power consumption device of the present application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of known matters and duplicate descriptions of the same structure may be omitted. This is to avoid the following description becoming unnecessarily redundant and to facilitate understanding by those skilled in the art. Furthermore, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application, and are not intended to limit the subject matter described in the claims.

[0068] The "ranges" disclosed in this application are defined in the form of lower and upper limits, and a given range is defined by selecting lower and upper limits that define the boundaries of the particular range. Such defined ranges may or may not include the end values, and may be arbitrarily combined, i.e., any lower limit value may be combined with any upper limit value to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it can be understood that ranges of 60-110 and 80-120 are also contemplated. Also, if 1 and 2 are listed as minimum range values, and 3, 4, and 5 are listed as maximum range values, then the ranges of 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5 are all contemplated. In this application, unless otherwise stated, a numerical range of "a to b" represents a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, a numerical range of "0-5" means that all real numbers between "0-5" are listed herein, and "0-5" is an abbreviation for combinations of these numerical values. Also, when a parameter is described as an integer of 2 or greater, this corresponds to disclosing that the parameter is an integer, e.g., 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0069] Unless otherwise stated, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution, and such technical solution should be considered to be included in the disclosure content of the present application.

[0070] Unless otherwise stated, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution, and such a technical solution should be considered as being included in the disclosure content of the present application.

[0071] Unless otherwise stated, all steps in the present application may be performed sequentially, randomly, or preferably sequentially. For example, when the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, when the method includes a step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or may include steps (a), (c), and (b), or may include steps (c), (a), and (b).

[0072] Unless otherwise specified, the terms "comprise", "have", and "comprise" used herein mean open-ended and may also be closed-ended. For example, the terms "comprise", "have", and "comprise" may mean "comprise", "have", or "comprise" other components not listed, or "comprise", "have", or "comprise" only the components listed.

[0073] In this application, unless otherwise stated, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following conditions satisfy the condition "A or B": A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), or A and B are both true (or exist).

[0074] Unless otherwise explained, terms used in this application have the known meanings commonly understood by those of ordinary skill in the art.

[0075] Unless otherwise specified, the numerical values ​​of each parameter mentioned in this application can be measured by various test methods commonly used in the field, for example, according to the test methods provided in this application.

[0076] Unless otherwise specified, in this application, the term "active ions" refers to ions that can be repeatedly inserted and removed between the positive and negative electrodes of a secondary battery, including, but not limited to, lithium ions.

[0077] As used herein, the terms "plurality" and "multiple types" refer to two or more.

[0078] The present inventors have found that in order to improve the dynamic performance of a secondary battery, especially the fast charging performance, it is important to improve the dynamic performance of the negative electrode. Currently, the dynamic performance of the negative electrode is often improved by reducing the surface density of the negative electrode film layer or reducing the compression density of the negative electrode film layer. However, as proven by many studies, the above-mentioned method for improving the dynamic performance of the negative electrode only improves the dynamic performance of the battery at the beginning of charging to a certain extent, and does not have a significant effect on improving the dynamic performance of the battery at the end of charging, so that the dynamic performance of the secondary battery cannot be effectively improved, and thus the secondary battery cannot actually be charged at a high rate. In addition, the energy density of the secondary battery is also significantly reduced.

[0079] For example, when the energy density of a secondary battery is improved by increasing the compression density of the negative electrode film layer, the dynamic performance of the secondary battery is often deteriorated. In addition, the electrolyte infiltration property of the negative electrode film layer at high compression density is deteriorated, and the risk of crushing the negative electrode active material particles is increased, which increases side reactions inside the battery and further affects the storage performance of the secondary battery.

[0080] Therefore, it is difficult for current secondary batteries to achieve both high energy density and good dynamic and storage performance.

[0081] The present inventors conducted further research and ingeniously improved the structure of the negative electrode film layer, thereby solving the above problems.

[0082] Specifically, a first aspect of an embodiment of the present application provides a secondary battery.

[0083] The present application does not particularly limit the type of secondary battery, and for example, the secondary battery may be a lithium ion battery. In general, the secondary battery includes a positive electrode sheet, a negative electrode sheet, and an electrolyte. During charging and discharging of the secondary battery, active ions are repeatedly inserted and removed between the positive electrode sheet and the negative electrode sheet, and the electrolyte serves to conduct the active ions between the positive electrode sheet and the negative electrode sheet. The present application does not particularly limit the type of the electrolyte, and it may be selected according to actual needs. For example, the electrolyte may be at least one selected from a solid electrolyte and a liquid electrolyte (i.e., an electrolyte solution). The secondary battery using the electrolyte solution and the secondary battery using the solid electrolyte may further include a separator provided between the positive electrode sheet and the negative electrode sheet and serving as an insulator. [Negative electrode sheet]

[0084] 1 to 3 are schematic diagrams of an embodiment of a negative electrode sheet of the present application. As shown in Fig. 1 to 3, a negative electrode sheet 10 includes a negative electrode current collector 101 and a negative electrode film layer 102 formed on at least one surface of the negative electrode current collector 101. The negative electrode film layer 102 has a first surface 102a away from the negative electrode current collector 101 and a second surface 102b provided opposite to the first surface 102a. The thickness of the negative electrode film layer 102 is H, and the thickness range from the second surface 102b of the negative electrode film layer to 0.3H is H. a region within a thickness range of 0.3H from a first surface 102a of the negative electrode film layer is a first region 1021 of the negative electrode film layer, and a region within a thickness range of 0.3H from a first surface 102a of the negative electrode film layer is a second region 1022 of the negative electrode film layer, the first region 1021 includes a first active material, the second region 1022 includes a second active material, the first active material includes a first carbon-based material, the second active material includes a second carbon-based material, the first carbon-based material has a pore structure, and the I D / I G is the second carbon-based material I D / IG smaller than I D is 1350±50cm in the Raman spectrum. -1 The D peak intensity at I G is 1580±50cm in the Raman spectrum. -1 The thickness H of the negative electrode film layer refers to the thickness of the negative electrode film layer located on one side of the negative electrode current collector.

[0085] The inventors have conducted research and found that a first region of a negative electrode film layer includes a first carbon-based material, a second region includes a second carbon-based material, the first carbon-based material has a pore structure, and the I of the first carbon-based material D / I G The second carbon-based material I D / I G It has been discovered that by making the negative electrode sheet smaller than 0.1 mm in diameter, the negative electrode sheet can have a high compression density, high active ion transport performance, and high surface stability, and thus the secondary battery can have both good kinetic performance and storage performance under the premise of having a high energy density.

[0086] Secondary carbon-based materials I D / I G Since the negative electrode membrane layer has a large area, it has better kinetic performance, improves the speed at which active ions are embedded in the negative electrode membrane layer, improves the transport performance of active ions in the negative electrode membrane layer, and is advantageous for improving the kinetic performance of the secondary battery. In addition, when it is located in the second region of the negative electrode membrane layer, it is advantageous for fully exerting the advantage of its excellent kinetic performance, and is advantageous for improving the impregnation and retention properties of the negative electrode membrane layer with respect to the electrolyte.

[0087] The first carbon-based material has a pore structure and a large compression density, which can improve the compression density of the negative electrode film layer and the energy density of the secondary battery. D / I GDue to its small size, it has high surface stability and low surface activity, which can reduce the occurrence of side reactions and improve the storage performance of the secondary battery. At the same time, the first carbon-based material has the advantage of higher capacity, and when it is located in the first region of the negative electrode film layer, it can fully exert the advantages of its high capacity and high compression density, thereby improving the energy density of the secondary battery.

[0088] Therefore, the negative electrode sheet according to the present application can achieve both high compression density, high active ion transport performance, and high surface stability. In addition, a secondary battery using the negative electrode sheet according to the present application can achieve both good kinetic performance and storage performance on the premise of having a high energy density.

[0089] In some embodiments, the second carbon-based material I D / I G I of the first carbon-based material D / I G The ratio A is 0.80 or less, and can be selected from 0.32 to 0.77, or 0.33 to 0.70. If α is within the above range, it is advantageous to better achieve both good dynamic performance and storage performance on the premise that the secondary battery has a high energy density.

[0090] In some embodiments, the I of the first carbon-based material D / I G is 0.152~0.280, and can be selected from 0.152~0.260, 0.153~0.240, 0.155~0.220, 0.155~0.200, and 0.155~0.180. D / I G When is within the above range, the first carbon-based material has a small amount of disordered carbon, a high gram capacity (capacity per gram) and high chemical stability, thereby reducing the occurrence of side reactions and improving the energy density and storage performance of the secondary battery.

[0091] In some embodiments, the second carbon-based material I D / I Gis 0.230-0.500, optionally 0.235-0.450. D / I G When is within the above range, the second carbon-based material has better active ion transport performance, which is advantageous for improving the dynamic performance of the secondary battery.

[0092] In some embodiments, the volume distribution particle size Dv50 of the second carbon-based material is smaller than the volume distribution particle size Dv50 of the first carbon-based material, which is advantageous for the first and second regions of the negative electrode membrane layer to have a suitable pore distribution, thereby improving the compression density of the negative electrode membrane layer and the energy density of the secondary battery, while improving the electrolyte impregnation and retention properties of the negative electrode membrane layer and reducing the expansion of the negative electrode sheet, thereby improving the storage performance and / or cycle performance of the secondary battery.

[0093] In some embodiments, the second carbon-based material has a powder compression density lower than that of the first carbon-based material at a pressure of 20,000 N. Adjusting the powder compression density of the second carbon-based material to be lower than that of the first carbon-based material is advantageous for improving the energy density of the secondary battery, while also favoring that the first and second regions of the negative electrode membrane layer have a suitable pore distribution, thereby improving the electrolyte impregnation and retention properties of the negative electrode membrane layer, and improving the kinetic performance and / or cycle performance of the secondary battery.

[0094] In some embodiments, the second carbon-based material comprises at least one of synthetic graphite and natural graphite. Optionally, the second carbon-based material comprises natural graphite.

[0095] In certain embodiments, the second carbon-based material has a pore structure.

[0096] In some embodiments, the ratio of the pore area in the cross section of the first carbon-based material particle to the cross-sectional area of ​​the first carbon-based material particle is α 1and the ratio of the pore area in the cross section of the second carbon-based material particle to the cross-sectional area of ​​the second carbon-based material particle is α 2 And α 1 <α 2 Let us assume that.

[0097] In the present application, the ratio α of the pore area in the cross section of the first carbon-based material particle to the cross-sectional area of ​​the first carbon-based material particle 1 and a ratio α of the pore area in the cross section of the second carbon-based material particle to the cross-sectional area of ​​the second carbon-based material particle. 2 can be obtained by testing the cross-sectional images of the first carbon-based material and the second carbon-based material, respectively. For example, a cross-section polisher (e.g., IB-09010 CP type argon ion cross-section polisher from JEOL Co., Ltd., Japan) is used to produce a cross-section of the first carbon-based material (or the second carbon-based material). Then, referring to JY / T010-1996, a scanning electron microscope (e.g., Sigma 300 type scanning electron microscope from ZEISS Co., Ltd., Germany) is used to scan the cross-section of the first carbon-based material (or the second carbon-based material). Finally, an image processing software (e.g., AVIZO) is used to calculate the pore area of ​​the first carbon-based material (or the second carbon-based material), and α 1 is the ratio of the pore area in the cross section of the first carbon-based material particle to the cross-sectional area of ​​the first carbon-based material particle, and α 2 is the ratio of the pore area in the cross section of the second carbon-based material particle to the cross-sectional area of ​​the second carbon-based material particle.

[0098] In some embodiments, the second carbon-based material has a thickness of 0.15 μm. 2 and optionally, one or more pore structures having a pore area of ​​0.15 μm or more. 2 ~2.0μm 2 The porous structure includes one or more pore structures having a pore area of

[0099] In some embodiments, the X-ray diffraction spectrum of the first carbon-based material does not have a diffraction peak of a 3R phase 012 plane.

[0100] In some embodiments, the second carbon-based material has an X-ray diffraction spectrum having a diffraction peak of a 3R phase 012 plane.

[0101] In some embodiments, the second carbon-based material has an X-ray diffraction spectrum having a diffraction peak of a 3R phase 101 plane.

[0102] 3R (rhombohedral) phase is rhombohedral phase crystalline carbon having an ABCABC... stacking structure. Natural graphite usually has many internal defects and contains 3R phase crystalline carbon, and for example, in its X-ray diffraction spectrum, it usually has diffraction peaks of the 3R phase 012 and 101 planes. However, artificial graphite usually does not have 3R phase crystalline carbon, and for example, in its X-ray diffraction spectrum, it usually does not have diffraction peaks of the 3R phase 012 and 101 planes.

[0103] The diffraction peak of the 3R phase 012 plane has a corresponding 2θ range of 46° to 47° in the X-ray diffraction spectrum, and the diffraction peak of the 3R phase 101 plane has a corresponding 2θ range of 43° to 44° in the X-ray diffraction spectrum.

[0104] Since the first carbon-based material does not have a diffraction peak of the 3R phase 012 plane, the first carbon-based material particles have fewer internal defects, which can further reduce the occurrence of side reactions and the irreversible consumption of active ions, and improve the initial coulombic efficiency and storage performance of the secondary battery.

[0105] In some embodiments, the first carbon-based material has a thickness of 0.15 μm. 2 and optionally, one or more pore structures having a pore area of ​​0.15 μm or more. 2 ~2.0μm 2 When the first carbon-based material includes a pore structure having the pore area, the pore structure can ensure an expansion space required for the volume change of the particles, thereby further reducing the risk of new interfaces being generated due to particle fracture, reducing the occurrence of side reactions, and improving the storage performance of the secondary battery.

[0106] In some embodiments, the first carbon-based material includes an outer region and an inner region located inside the outer region, the outer region being a region extending from a surface of the first carbon-based material particle to an interior of the particle by a distance of 0.25L, where L is the minor axis length of the first carbon-based material particle, and the total pore area of ​​the outer region is S. 1 The total pore area of ​​the inner region is S 2 And S 2 >S 1 Let us assume that.

[0107] The first carbon-based material is S 2 >S 1 If the above conditions are satisfied, the first carbon-based material further has the characteristics that the number of pores in the inner region is large and / or the size of the pores is large, and the number of pores in the outer region is small and / or the size of the pores is small. The pore structure of the inner region of the first carbon-based material can effectively reduce the pressure of the roll press of the negative electrode sheet, effectively reduce the damage to the particles, and ensure the expansion space required for the volume change of the particles, thereby reducing the risk of new interfaces caused by particle crushing, and further reducing the occurrence of side reactions. The small number of pores and / or the small size of the pores in the outer region of the first carbon-based material allows the first carbon-based material particles to have a stable structure, and can prevent the electrolyte from penetrating into the inner pore structure of the first carbon-based material particles as much as possible, thereby further reducing the occurrence of side reactions and reducing the consumption of active ions due to the formation of the SEI film inside the particles. Therefore, it is possible to obtain a first carbon-based material having a stable structure and a small pore size. 2 >S 1 Further, when the above requirement is satisfied, the initial coulombic efficiency of the secondary battery can be improved, and the storage performance and / or cycle performance of the secondary battery can be further improved.

[0108] In some embodiments, 1.5≦S 2 / S 1 ≦500, 2≦S 2 / S 1 ≦450, 2.2≦S 2 / S 1 ≦400, 2.4≦S 2 / S 1 ≦300, 2.5≦S 2 / S 1 ≦250, 2.6≦S 2 / S 1 ≦200, 2.8≦S 2 / S 1 ≦150, 3.0≦S 2 / S 1 ≦100. The present inventors have further investigated the 2 / S 1 It has been found that when the content of the ionic liquid falls within the above range, the secondary battery can more suitably achieve both high energy density and good storage performance.

[0109] In the present application, the total pore area S of the outer region of the first carbon-based material 1 and the total pore area S of the inner region 2 can be obtained by testing a cross-sectional image of the first carbon-based material.

[0110] In this application, a cross-sectional image of a first carbon-based material includes a cross-sectional image passing through the center of a particle of the first carbon-based material. The "particle center" refers to a range within a radius extending 0.1 μm from the geometric center of the particle toward the particle surface.

[0111] In the present application, the minor axis length of a particle refers to the minimum value when a connecting line between two points on the surface of the particle passes through the geometric center of the particle.

[0112] 4 is a schematic diagram of a cross-sectional image of one of the particles of the first carbon-based material 200 of the present application, where the cross-sectional image passes through the center of the particle of the first carbon-based material 200. As shown in FIG. 4, L indicates the short axis length of the particle of the first carbon-based material 200, and a region extending from the surface of the particle of the first carbon-based material 200 to the inside of the particle by a distance of 0.25L is an outer region 201, and a region inside the outer region 201 is an inner region 202.

[0113] The cross section of the first carbon-based material can be prepared by using a cross section polisher (e.g., IB-09010 CP type argon ion cross section polisher from JEOL Co., Ltd., Japan). Then, referring to JY / T010-1996, the cross section of the first carbon-based material is scanned by using a scanning electron microscope (e.g., Sigma 300 type scanning electron microscope from ZEISS Co., Ltd., Germany). Finally, the total pore area S of the outer region of the first carbon-based material is calculated by using image processing software (e.g., AVIZO). 1 and the total hole area S of the inner region 2 Calculate.

[0114] In some embodiments, the short axis length L of the first carbon-based material particles satisfies L≧6 μm, optionally 6 μm≦L≦25 μm, 6 μm≦L≦20 μm, 7 μm≦L≦20 μm, 8 μm≦L≦20 μm, 8 μm≦L≦18 μm, 8 μm≦L≦16 μm.

[0115] In some embodiments, the area of ​​the pore structure in the outer region of the first carbon-based material is less than 0.2 μm 2 Selectable below 0.10μm 2 The inventors have found in further research that the area of ​​the pore structure in the outer region of the first carbon-based material can be controlled within the above range to provide a dense structure in the outer region of the first carbon-based material. This effectively improves the structural stability of the first carbon-based material, prevents the electrolyte from penetrating the pore structure inside the first carbon-based material particles as much as possible, reduces the occurrence of side reactions, and effectively improves the storage performance of the secondary battery. Of course, the present application does not require that the areas of all pore structures in the outer region of the first carbon-based material be less than 0.2 μm 2 For example, 95% or more, optionally 99% or more of the pore structure has an area of ​​0.2 μm 2 It can be controlled so that:

[0116] In some embodiments, the inner region of the first carbon-based material is 0.15 μm 2and optionally, one or more pore structures having an area of ​​0.15 μm or more. 2 ~2.0μm 2 In further research, the present inventors have found that the inner region of the first carbon-based material includes a pore structure of the above size, which can effectively reduce the pressure of the roll press of the negative electrode sheet, effectively reduce damage to the particles, ensure a sufficient and stable expansion space for the volume change of the first carbon-based material particles, reduce the risk of crushing the first carbon-based material particles, while improving the compression density of the negative electrode film layer and improving the energy density of the secondary battery.

[0117] In some embodiments, at least a portion of the surface of the first carbon-based material has a coating layer. Optionally, 80% or more of the surface of the first carbon-based material is coated with the coating layer, and further, 90% to 100% of the surface of the first carbon-based material is coated with the coating layer. Optionally, in some embodiments, the coating layer contains carbon, for example, amorphous carbon and / or crystalline carbon with a graphitization degree of between 65% and 89%. This can improve the dynamic performance of the secondary battery.

[0118] Of course, in some embodiments, the surface of the first carbon-based material may not have a coating layer. The first carbon-based material of the present application has a relatively stable surface, and when the surface does not have a coating layer, it is advantageous to maintain low side reaction activity and reduce the occurrence of side reactions, which can further improve the cycle performance and / or storage performance of the secondary battery.

[0119] In some embodiments, at least a part of the surface of the second carbon-based material has a coating layer. In particular, natural graphite has a high surface activity, and by forming a coating layer on the surface of the natural graphite, the surface activity can be reduced, thereby further improving the storage performance and cycle performance of the secondary battery.

[0120] In some embodiments, 80% or more of the surface of the second carbon-based material is coated with a coating layer, and optionally, 90% to 100% of the surface of the second carbon-based material is coated with a coating layer. In some embodiments, the coating layer may include carbon, for example, amorphous carbon, which is advantageous for improving the dynamic performance of the secondary battery. The carbon may be obtained by carbonizing an organic carbon source. The organic carbon source may be a carbon-containing material known in the art that is suitable for coating, and may include, for example, one or more of coal pitch, petroleum pitch, phenolic resin, coconut shell, etc.

[0121] In some embodiments, the first carbon-based material includes primary particles, and optionally the quantity ratio of the primary particles in the first carbon-based material is 50% or more, for example, 50% to 100%, 55% to 95%, 60% to 100%, 65% to 90%, 65% to 80%, 70% to 100%, 75% to 90%, 80% to 100%, 90% to 100%, or 95% to 100%. When the first carbon-based material includes a suitable proportion of primary particles, it has high structural stability, reduces the occurrence of side reactions, and can improve the storage performance of the secondary battery, and can also improve the compression density of the negative electrode film layer and improve the energy density of the secondary battery.

[0122] In some embodiments, the first carbon-based material may be all primary particles, ie, the number percentage of the primary particles in the first carbon-based material is 100%.

[0123] In some embodiments, the second carbon-based material includes primary particles, and optionally the quantity ratio of the primary particles in the second carbon-based material is 50% or more, for example, 50% to 100%, 55% to 95%, 60% to 100%, 65% to 90%, 65% to 80%, 70% to 100%, 75% to 90%, 80% to 100%, 90% to 100%, or 95% to 100%. When the second carbon-based material includes a suitable proportion of primary particles, it has high structural stability, reduces side reactions, and improves the storage performance of the secondary battery, and can also improve the compression density of the negative electrode film layer and improve the energy density of the secondary battery.

[0124] In some embodiments, the second carbon-based material may be all primary particles, ie, the number percentage of the primary particles in the second carbon-based material is 100%.

[0125] In further research, the present inventors have found that when the first carbon-based material satisfies the above design and further satisfies one or more of the following conditions, the performance of the secondary battery can be further improved, for example, at least one of the energy density, storage performance, kinetic performance, and cycle performance of the secondary battery can be improved.

[0126] In some embodiments, the first carbon-based material has a specific surface area of ​​2.1 m 2 / g or less, selectable 1.0m 2 / g~2.1m 2 / g, 1.1m 2 / g~2.0m 2 / g, 1.15m 2 / g~1.8m 2 The first carbon-based material has a relatively low specific surface area, which can reduce the consumption of active ions due to the formation of the SEI film and improve the initial coulombic efficiency and storage performance of the secondary battery.

[0127] In some embodiments, the first carbon-based material has a volume distribution particle size Dv50 of 8.0 μm to 25.0 μm, optionally 10.0 μm to 22.0 μm.

[0128] In some embodiments, the first carbon-based material has a volume distribution particle size Dv90 of 16.0 μm to 45.0 μm, optionally 16.5 μm to 42.0 μm.

[0129] When the volume distribution particle size Dv50 and / or Dv90 of the first carbon-based material is within the above range, it is advantageous to improve the transport performance of active ions and electrons, thereby further improving the dynamic performance of the secondary battery, and also to reduce the specific surface area of ​​the first carbon-based material, reduce the occurrence of side reactions, and improve the storage performance of the secondary battery.

[0130] In some embodiments, the particle size distribution (Dv90-Dv10) / Dv50 of the first carbon-based material is less than 1.55, and optionally ranges from 0.90 to 1.50. When the particle size distribution (Dv90-Dv10) / Dv50 of the first carbon-based material is within the above range, the particle deposition performance is good, which is favorable for improving the compression density of the negative electrode membrane layer, thereby further improving the energy density of the secondary battery, and is favorable for adjusting the pore distribution of the negative electrode membrane layer, thereby improving the dynamic performance of the secondary battery.

[0131] In some embodiments, the powder of the carbon-based material has a compressed density of 1.65 g / cm at a pressure of 20,000 N. 3 ~2.0g / cm 3 and selectable 1.68g / cm 3 ~1.98g / cm 3 When the compression density of the powder of the first carbon-based material is within the above range, it can improve the compression density of the negative electrode film layer, improve the energy density of the secondary battery, and form a reasonable channel structure between the particles of the negative electrode film layer, which is favorable for improving the transport performance of active ions and electrons, and further improving the dynamic performance of the secondary battery.

[0132] In some embodiments, the carbon-based material has a tap density of 0.85 g / cm 3 ~1.30g / cm 3and can be selected from 0.90g / cm 3 ~1.25g / cm 3 When the tap density of the first carbon-based material is within the above range, it can improve the compression density of the negative electrode film layer, improve the energy density of the secondary battery, and form a reasonable channel structure between the particles of the negative electrode film layer, which is favorable for improving the transport performance of active ions and electrons, and further improving the dynamic performance of the secondary battery.

[0133] In some embodiments, the graphitization degree of the first carbon-based material is 95.5% or more, and optionally 95.5% to 98.0%. When the graphitization degree of the first carbon-based material is within the above range, it is advantageous for improving the energy density of the secondary battery.

[0134] In some embodiments, the gram capacity (capacity per gram) of the first carbon-based material is 355 mAh / g or more, and optionally 355 mAh / g to 370 mAh / g. If the gram capacity of the first carbon-based material is within the above range, it is advantageous to improve the energy density of the secondary battery.

[0135] In some embodiments, the X-ray diffraction spectrum of the first carbon-based material has a diffraction peak of the 3R phase 101 plane. When the first carbon-based material has a diffraction peak of the 3R phase 101 plane, there are many active sites on the surface of the first carbon-based material, which is advantageous for rapid insertion and desorption of active ions.

[0136] In some embodiments, the adsorption amount of the first carbon-based material for 100 g of linseed oil is 30 ml to 47 ml, and optionally 33 ml to 46 ml. When the adsorption amount of the first carbon-based material for linseed oil is within the above range, the side reaction activity of the surface of the first carbon-based material particles is low, which can reduce the consumption of active ions due to the formation of the SEI film, and the negative electrode film layer has a reasonable channel structure, which is advantageous for improving the impregnation and liquid retention properties of the negative electrode film layer with respect to the electrolyte. Therefore, when the adsorption amount of the first carbon-based material for linseed oil is within the above range, it is advantageous for improving the storage performance and / or dynamic performance of the secondary battery.

[0137] The adsorption amount of 100g of the first carbon-based material to linseed oil can be tested according to the following method. Refer to GB / T 3780.2-2017, weigh a dried test sample with a certain mass (e.g., 20g), place the weighed sample in the mixing chamber of the oil absorption meter, and cover the mixing chamber when the temperature of the mixing chamber is 23°C. Align the oil inlet of the constant speed burette above the hole in the lid of the mixing chamber. Start the oil absorption meter, and the instrument starts to operate and drip linseed oil. As the oil absorption amount of the sample increases, the mixture material changes from a free-flowing state to a semi-plastic aggregate, and the viscosity of the mixture continues to increase, and the viscosity is transmitted to the torque sensor system of the oil absorption meter. When the dripped oil causes the semi-plastic aggregate to reach a preset torque level, the oil absorption meter and the constant speed burette are automatically closed. Read the value corresponding to 70% of the maximum torque of the fitting curve, and calculate the torque according to the formula V = (V 0 The adsorption amount V of 100 g of the first carbon-based material to linseed oil is calculated using the formula (1 / m) × 100, and V 0 indicates the volume of linseed oil consumed by the sample corresponding to 70% of the maximum torque, in ml, and m is the mass of the added sample, in g.

[0138] In further research, the inventors have found that when the second carbon-based material satisfies the above design and further satisfies one or more of the following conditions, the performance of the secondary battery can be further improved, for example, at least one of the energy density, storage performance, kinetic performance, and cycle performance of the secondary battery can be improved.

[0139] In some embodiments, the second carbon-based material has a specific surface area of ​​1.8 m 2 / g or more, selectable 1.9m 2 / g~3.5m 2 / g, 1.85m 2 / g~3.50m 2 / g, 1.90m 2 / g~3.45m 2When the specific surface area of ​​the second carbon-based material is within the above range, it is advantageous for reducing the occurrence of side reactions and reducing the consumption of active ions due to the formation of the SEI film, so that the secondary battery can achieve both a high initial coulombic efficiency and good cycle performance and storage performance.

[0140] In some embodiments, the second carbon-based material has a Dv50 of 8.0 μm to 15.0 μm, and optionally 10.0 μm to 15.0 μm. When the volume distribution particle size Dv50 of the second carbon-based material is within the above range, it is advantageous to improve the transport performance of active ions and electrons, and the dynamic performance of the secondary battery can be further improved, and the specific surface area of ​​the second carbon-based material can be reduced, which can reduce the occurrence of side reactions and improve the storage performance of the secondary battery.

[0141] In some embodiments, the particle size distribution (Dv90-Dv10) / Dv50 of the second carbon-based material is less than 1.65, and optionally ranges from 0.90 to 1.65. When the particle size distribution (Dv90-Dv10) / Dv50 of the second carbon-based material is within the above range, the particle deposition performance is good, which is favorable for improving the compression density of the negative electrode membrane layer, thereby further improving the energy density of the secondary battery, and is favorable for adjusting the pore distribution of the negative electrode membrane layer, thereby improving the dynamic performance of the secondary battery.

[0142] In some embodiments, the second carbon-based material has a powder compaction density of 1.60 g / cm at a pressure of 20,000 N. 3 ~1.95g / cm 3 and selectable 1.65g / cm 3 ~1.92g / cm 3 When the compressed density of the powder of the second carbon-based material is within the above range, it is possible to improve the compressed density of the negative electrode film layer, improve the energy density of the secondary battery, and also to form a reasonable channel structure between the particles of the negative electrode film layer, improve the transport performance of active ions and electrons, improve the impregnation and retention properties of the negative electrode film layer with respect to the electrolyte, and further to improve the kinetic performance and / or cycle performance of the secondary battery.

[0143] In some embodiments, the second carbon-based material has a tap density of 0.85 g / cm 3 ~1.25g / cm 3 and can be selected from 0.90g / cm 3 ~1.25g / cm 3 When the tap density of the second carbon-based material is within the above range, it is possible to improve the compression density of the negative electrode film layer, improve the energy density of the secondary battery, and also to form a reasonable channel structure between the particles of the negative electrode film layer, improve the transport performance of active ions and electrons, improve the impregnation and retention properties of the negative electrode film layer for the electrolyte, and further improve the dynamic performance of the secondary battery.

[0144] In some embodiments, the graphitization degree of the second carbon-based material is 94.5%-98.0%, optionally 95.0%-97.5%, which is favorable for improving the active ion transport performance of the negative electrode membrane layer and for improving the negative electrode capacity, so that the secondary battery can achieve both high energy density and good dynamic performance.

[0145] In some embodiments, the gram capacity of the second carbon-based material is 355 mAh / g to 372 mAh / g, and optionally 356 mAh / g to 370 mAh / g. When the gram capacity of the second carbon-based material is within the above range, the energy density of the secondary battery is improved, while the second carbon-based material also has good active ion transport performance, which is advantageous for improving the kinetic performance of the secondary battery.

[0146] In some embodiments, the first active material further comprises a third carbon-based material, the third carbon-based material comprising primary particle form of artificial graphite. The combination of the first carbon-based material and the third carbon-based material is advantageous for the negative electrode film layer to have a suitable channel structure, and is also advantageous for improving the active ion transport performance of the negative electrode film layer.

[0147] In some embodiments, the surface of the primary particle-form artificial graphite does not have a carbon coating layer. The primary particle-form artificial graphite has a more stable surface, and when the surface does not have a coating layer, it is advantageous to maintain its low side reaction activity and reduce the occurrence of side reactions, thereby further improving the cycle performance and storage performance of the secondary battery.

[0148] In some embodiments, the mass proportion of the third carbon-based material in the first active material is less than 80 wt%, and optionally is 20 wt%-70 wt%, 30 wt%-70 wt%, 35 wt%-70 wt%, 40 wt%-70 wt%, 30 wt%-60 wt%, 35 wt%-60 wt%, or 40 wt%-60 wt%.

[0149] In further research, the present inventors have found that when the third carbon-based material satisfies the above design and further satisfies one or more of the following conditions, the performance of the secondary battery can be further improved, for example, at least one of the energy density, storage performance, kinetic performance, and cycle performance of the secondary battery can be improved.

[0150] In some embodiments, the third carbon-based material has a graphitization degree of 92.5%-95.5%, optionally 92.7%-95.5%. The graphitization degree of the third carbon-based material within the above range is favorable for improving the active ion transport performance of the negative electrode film layer, especially the first region, so that the secondary battery can achieve both high energy density and good dynamic performance.

[0151] In some embodiments, the third carbon-based material has a powder OI value of 4.5 to 11.5, and optionally 4.5 to 11.0. The third carbon-based material has a small powder OI value and has active ion insertion ports in all directions of the particles, which is advantageous for quickly receiving active ions from the positive electrode, thereby further improving the dynamic performance of the secondary battery. In addition, the third carbon-based material particles have high homogeneity, which is advantageous for dispersing the expansion rate during active ion insertion and reducing the volume change and thickness repulsion rate of the negative electrode film layer, thereby further improving the cycle performance and storage performance of the secondary battery.

[0152] In some embodiments, the particle size distribution (Dv90-Dv10) / Dv50 of the third carbon-based material is less than 1.65, and optionally between 0.90 and 1.65. When the particle size distribution (Dv90-Dv10) / Dv50 of the third carbon-based material is within the above range, the particle deposition performance thereof is good, which is favorable for improving the compression density of the negative electrode membrane layer, thereby further improving the energy density of the secondary battery, and is favorable for adjusting the pore distribution of the negative electrode membrane layer, thereby improving the dynamic performance of the secondary battery.

[0153] In some embodiments, the third carbon-based material has a volume distribution particle size Dv50 of 12.0 μm to 22.0 μm, and optionally 13.5 μm to 20.0 μm. When the volume distribution particle size Dv50 of the third carbon-based material is within the above range, it is advantageous to improve the transport performance of active ions and electrons, thereby further improving the dynamic performance of the secondary battery, and also to reduce the specific surface area of ​​the third carbon-based material, reduce the occurrence of side reactions, and improve the storage performance of the secondary battery.

[0154] In some embodiments, the third carbon-based material has a specific surface area of ​​1.0 m 2 / g~2.0m 2 / g, selectable 1.05m 2 / g~1.95m 2The third carbon-based material has a low specific surface area, which can reduce the consumption of active ions due to the formation of the SEI film, reduce the occurrence of side reactions, and improve the initial coulombic efficiency and storage performance of the secondary battery.

[0155] In some embodiments, the third carbon-based material has a tap density of 0.95 g / cm 3 ~1.25g / cm 3 and can be selected from 1.00g / cm 3 ~1.25g / cm 3 When the tap density of the third carbon-based material is within the above range, it can improve the compression density of the negative electrode film layer, improve the energy density of the secondary battery, and form a reasonable channel structure between the particles of the negative electrode film layer, which is favorable for improving the transport performance of active ions and electrons, and further improving the dynamic performance of the secondary battery.

[0156] In some embodiments, the gram capacity of the third carbon-based material is 350mAh / g to 363mAh / g, and optionally 352mAh / g to 362mAh / g. When the gram capacity of the third carbon-based material is within the above range, the energy density of the secondary battery can be improved while the transport performance of the active ions of the negative electrode film layer can be improved, which is also advantageous for improving the dynamic performance of the secondary battery.

[0157] As shown in Figures 1 to 3, the negative electrode film layer 102 further includes an intermediate region 1023 located between the first region 1021 of the negative electrode film layer and the second region 1022 of the negative electrode film layer and having a thickness of 0.4H (H indicates the thickness of the negative electrode film layer 102).

[0158] In some embodiments, the intermediate region includes the first active material and / or the second active material. For example, as shown in FIG. 2, the intermediate region 1023 may have the same composition as the first region 1021, so that the distribution region of the first active material in the thickness direction of the negative electrode film layer 102 is within a thickness range of 0.7H from the second surface 102b of the negative electrode film layer, or as shown in FIG. 3, the intermediate region 1023 may have the same composition as the second region 1022, so that the distribution region of the second active material in the thickness direction of the negative electrode film layer 102 is within a thickness range of 0.7H from the first surface 102a of the negative electrode film layer, or as shown in FIG. 1, the intermediate region 1023 includes the first active material and the second active material at the same time, in which case the intermediate region 1023 includes a layer structure having the first active material and a layer structure having the second active material at the same time, and the two-layer structure may further have a layer interface.

[0159] In some embodiments, the first region of the negative electrode film layer may further include other negative electrode active materials known in the art other than the first carbon-based material and the third carbon-based material, for example, may further include a silicon-based material. The silicon-based material plays a role in improving the channel structure in the negative electrode film layer, facilitating the impregnation and liquid retention of the electrolyte, improving the dynamic performance of the secondary battery, and improving the negative electrode capacity, thereby further improving the energy density of the secondary battery. Optionally, the silicon-based material may include one or more of elemental silicon, silicon oxide, silicon carbon composite, silicon nitrogen composite, and silicon alloy material.

[0160] In some embodiments, when the first region of the negative electrode film layer further contains a silicon-based material, the mass ratio of the silicon-based material in the first region of the negative electrode film layer may be 10% or less, for example, 1% to 8%, 2% to 6%, or 3% to 7%, thereby improving the dynamic performance and energy density of the secondary battery and simultaneously achieving good cycle performance and storage performance of the secondary battery.

[0161] In some embodiments, the second region of the negative electrode film layer may further include other negative electrode active materials known in the art other than the second carbon-based material, for example, may further include a silicon-based material. The silicon-based material plays a role in improving the channel structure in the negative electrode film layer, facilitating the impregnation and liquid retention of the electrolyte, improving the dynamic performance of the secondary battery, and improving the negative electrode capacity, thereby further improving the energy density of the secondary battery. Optionally, the silicon-based material may include one or more of elemental silicon, silicon oxide, silicon carbon composite, silicon nitrogen composite, and silicon alloy material.

[0162] In some embodiments, when the second region of the negative electrode film layer further comprises a silicon-based material, the mass ratio of the silicon-based material in the second region of the negative electrode film layer may be 10% or less, for example, 1% to 8%, 2% to 6%, or 3% to 7%, thereby improving the dynamic performance and energy density of the secondary battery and simultaneously achieving good cycle performance and storage performance of the secondary battery.

[0163] In some embodiments, the first region and the second region both contain a silicon-based material, and the mass ratio of the silicon-based material in the first region is equal to or less than the mass ratio of the silicon-based material in the second region. During the charge and discharge process of the secondary battery, the volume expansion of the silicon-based material is greater than that of the carbon-based material, which is advantageous for the second region of the negative electrode membrane layer to have a high porosity, thereby improving the impregnation property of the negative electrode membrane layer with respect to the electrolyte, improving the transport performance of active ions, and improving the cycle performance and / or kinetic performance of the secondary battery. In addition, the high porosity of the second region of the negative electrode membrane layer can improve the active ion transport performance of the first region of the negative electrode membrane layer.

[0164] In some embodiments, the intermediate region of the negative electrode film layer further comprises a silicon-based material.

[0165] In some embodiments, the first region, the second region and the middle region of the negative electrode membrane layer may include a negative electrode conductive agent and / or a negative electrode adhesive, as required.

[0166] In the present application, the type of the negative electrode conductive agent is not particularly limited. For example, the negative electrode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0167] In the present application, the type of the negative electrode adhesive is not particularly limited. For example, the negative electrode adhesive may include one or more of styrene butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0168] In some embodiments, the first region, the second region and the intermediate region of the negative electrode membrane layer further include other auxiliary agents as necessary. For example, the other auxiliary agents may include a thickener, such as sodium carboxymethylcellulose (CMC), a PTC thermistor material, etc.

[0169] In some embodiments, the porosity of the negative electrode membrane layer is 18.0%-36.7%, and optionally 19.0%-34.0%, which is favorable for the negative electrode membrane layer to achieve both high capacity and suitable channel structure, and therefore favorable for the secondary battery to achieve both high energy density and good storage and dynamic performance.

[0170] In some embodiments, the negative electrode film layer has a compressed density of 1.45 g / cm 3 ~1.90g / cm 3 and can be selected from 1.50g / cm 3~1.85g / cm 3 This is advantageous for the negative electrode film layer to achieve both high capacity and high active ion and electron transport performance, and is therefore advantageous for the secondary battery to achieve both high energy density and good storage and dynamic performance.

[0171] In some embodiments, the areal density of the negative electrode film layer is 5.0 mg / cm 2 ~25.0mg / cm 2 and selectable at 5.5mg / cm 2 ~22.5mg / cm 2 This is advantageous for the negative electrode film layer to achieve both high capacity and high active ion and electron transport performance, and is advantageous for the secondary battery to achieve both high energy density and good storage and dynamic performance.

[0172] In some embodiments, the OI value of the negative electrode film layer is 45.0 or less, and optionally 8.0 to 45.0, which is advantageous for improving the active ion insertion performance of the negative electrode film layer and for lowering the thickness repulsion rate of the negative electrode film layer, which is advantageous for the secondary battery to have both good storage performance and dynamic performance.

[0173] In some embodiments, the thickness of the negative electrode film layer is 60 μm or more, optionally 70 μm to 250 μm, 90 μm to 220 μm.

[0174] In some embodiments, the negative electrode current collector may be a metal foil sheet or a composite current collector. An example of a metal foil sheet may be copper foil. The composite current collector may include a polymeric material base layer and a metal material layer formed on at least one surface of the polymeric material base layer. For example, the metal material may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. For example, the polymeric material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0175] The negative electrode sheet does not exclude additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode sheet according to the present application further includes a conductive undercoat layer (e.g., made of a conductive agent and an adhesive) sandwiched between the negative electrode collector and the negative electrode film layer and provided on the surface of the negative electrode collector, and in some embodiments, the negative electrode sheet according to the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0176] The negative electrode current collector has two surfaces facing each other in the thickness direction, and the negative electrode film layer is provided on one or both of the two facing surfaces of the negative electrode current collector. Note that each negative electrode film layer parameter (e.g., compressed density, areal density, porosity, OI value, etc.) provided in the present application refers to the parameters of the negative electrode film layer on one side of the negative electrode current collector. When the negative electrode film layer is provided on both sides of the negative electrode current collector, if the parameters of the negative electrode film layer on either side satisfy the present application, it is considered to be within the protection scope of the present application.

[0177] In the present application, whether or not a coating layer is present on the surface of a material (eg, the first carbon-based material, the second carbon-based material, the third carbon-based material, etc.) can be determined by a transmission electron microscope.

[0178] In this application, the specific surface area of ​​a material (e.g., the first carbon-based material, the second carbon-based material, the third carbon-based material, etc.) has a meaning known in the art and can be measured by an instrument and method known in the art. For example, it can be tested by a nitrogen gas adsorption specific surface area analysis test method with reference to GB / T 19587-2017, and calculated by the BET (Brunauer Emmett Teller) method. The test instrument can be a Tri-Star 3020 type specific surface area pore size analysis tester from Micromeritics, USA.

[0179] In the present application, the graphitization degree of a material (e.g., the first carbon-based material, the second carbon-based material, the third carbon-based material, etc.) has a meaning known in the art, and can be tested by an apparatus and method known in the art. For example, the graphitization degree can be tested using an X-ray diffraction apparatus (e.g., Bruker D8 Discover), and the test can be performed with reference to JIS K 0131-1996 and JB / T 4220-2011, and the average layer spacing d of the C(002) plane in the crystal structure of the material can be measured. 002 Then, use the formula g=(0.344-d 002 The graphitization degree can be calculated based on the formula: d / (0.344-0.3354) × 100%. 002 is the average layer spacing of the C(002) plane in the material crystal structure, expressed in nanometers (nm).

[0180] In this application, the volume distribution particle size Dv10, Dv50, and Dv90 of a material (e.g., a first carbon-based material, a second carbon-based material, a third carbon-based material, etc.) have the meaning known in the art, and respectively indicate the particle size corresponding to when the cumulative volume distribution percentage of the material reaches 10%, 50%, and 90%, and can be measured by an instrument and method known in the art. For example, referring to GB / T 19077-2016, it can be measured using a laser particle size analyzer. The test instrument may be a Mastersizer 3000 type laser particle size analyzer from Malvern Panalytical Co., Ltd., UK.

[0181] In this application, the powder compaction density of a material (e.g., the first carbon-based material, the second carbon-based material, the third carbon-based material, etc.) has a meaning known in the art and can be measured by instruments and methods known in the art. For example, see GB / T 24533-2009 and can be measured by an electronic pressure tester (e.g., UTM7305 type electronic pressure tester). An exemplary test method is to weigh 1 g of sample powder and measure the powder compaction density of the material having a base area of ​​1.327 cm. 2 The powder is placed in a mold, pressurized to 2000 kg, and held for 30 seconds. The pressure is then released and held for 10 seconds. The powder compressed density of the material at a pressure of 20,000 N is then recorded and calculated.

[0182] In this application, the tap density of a material (e.g., the first carbon-based material, the second carbon-based material, the third carbon-based material, etc.) has a meaning known in the art and can be measured by instruments and methods known in the art. For example, it can be measured using a powder tap density tester with reference to GB / T5162-2006. The test instrument can be Dandong Baite BT-301, and the test parameters are vibration frequency 250±15 times / min, amplitude 3±0.2mm, vibration frequency 5000 times, and measuring cylinder 25mL.

[0183] In the present application, the I of a material (e.g., a first carbon-based material, a second carbon-based material, a third carbon-based material, etc.) D / I G can be tested using a Raman spectrometer. D is the 1350±50 cm of the Raman spectrum of the material. -1 represents the D peak intensity at G is the 1580±50 cm of the Raman spectrum of the material. -1 The test conditions were: excitation wavelength 532 nm, diffraction grating 600 markings, objective lens 50x, integration time 10 s, accumulation number 3, surface scanning to obtain D peak and G peak intensities at 100 points, and I peak intensity at 100 points. D / I G Calculate the maximum and minimum of 30 I D / I G The remaining 40 points are averaged and the I D / I G The test equipment can be a Horiba LabRAM HR800 Raman spectrometer.

[0184] In the present application, the powder OI value of the third carbon-based material has a meaning known in the art, and can be tested by using an apparatus and method known in the art. For example, the powder OI value can be tested using an X-ray diffraction apparatus (e.g., Bruker D8 Discover), and the test can be performed by obtaining an X-ray diffraction spectrum of a powder sample with reference to JIS K 0131-1996 and JB / T 4220-2011, and determining the OI value=I 004 / I 110 Based on this, the powder OI value of the sample can be calculated. 004 is the integrated area of ​​the diffraction peak of the crystalline carbon 004 plane in the powder sample, and I 110 is the integrated area of ​​the diffraction peak of the 110 plane of crystalline carbon in the powder sample.

[0185] In the X-ray diffraction analysis test of this application, a copper target is used as the anode target, CuKα radiation is used as the radiation source, the radiation wavelength λ=1.5418 angstroms, the scanning 2θ angle range is 20°-80°, and the scanning speed is 4° / min.

[0186] In this application, the quantitative proportion of primary particles in the first carbon-based material (or the second carbon-based material) refers to the following steps: randomly selecting one test sample in the negative electrode film layer, randomly selecting multiple test areas in the test sample, obtaining images of the multiple test areas using a scanning electron microscope, calculating the proportion of the number of the first carbon-based material (or the second carbon-based material) in the form of primary particles in each image to the total number of particles of the first carbon-based material (or the second carbon-based material), and taking the average of the multiple statistical results to represent the quantitative proportion of primary particles in the first carbon-based material (or the second carbon-based material).

[0187] In this application, the gram capacity (volume per gram) of a material (e.g., a first carbon-based material, a second carbon-based material, a third carbon-based material, etc.) has a meaning known in the art and can be tested by a method known in the art. An exemplary test method is as follows. A sample powder, a conductive agent such as carbon black (Super P), and an adhesive such as polyvinylidene fluoride (PVDF) are uniformly mixed with a solvent such as N-methylpyrrolidone (NMP) in a mass ratio of 91.6:1.8:6.6 to prepare a slurry. The prepared slurry is applied to the surface of a copper foil as a negative electrode current collector, and dried in an oven to prepare as required. Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent, and then LiPF 6 is dissolved in the organic solvent to produce an electrolyte solution with a concentration of 1 mol / L, and then a CR2430 button battery is assembled in a glove box protected by argon gas with a metallic lithium sheet as the counter electrode and a polyethylene (PE) thin film as the separator. The obtained button battery is left to stand for 12 h, and then discharged at a constant current of 0.05 C to 0.005 V at 25 ° C, left to stand for 10 minutes, discharged at a constant current of 50 μA to 0.005 V, left to stand for 10 minutes, and discharged at a constant current of 10 μA to 0.005 V. Then, it is charged at a constant current of 0.1 C to 2 V, and the charge capacity is recorded. The ratio of the charge capacity to the mass of the sample is the gram capacity of the corresponding material (e.g., the first carbon-based material, the second carbon-based material, the third carbon-based material, etc.).

[0188] In this application, the surface density of the negative electrode film layer has a meaning known in the art and can be tested by a method known in the art. For example, a negative electrode sheet that is coated on one side and cold pressed (if the negative electrode sheet is coated on both sides, the negative electrode film layer on one side can be wiped off first) is selected, and the surface area is S 1 The weight of the small disk is measured and the measurement is carried out. 1 Then, the negative electrode film layer of the weighed negative electrode sheet is wiped off, and the weight of the negative electrode current collector is weighed, and the weight is recorded as M 0 The surface density of the negative electrode sheet is recorded as (M 1 -M 0) / S 1 .

[0189] In this application, the compression density of the negative electrode film layer has a meaning known in the art and can be tested by a method known in the art. Compression density of the negative electrode film layer = surface density of the negative electrode film layer / thickness of the negative electrode film layer. The thickness of the negative electrode film layer has a meaning known in the art and can be tested by a method known in the art, for example, a micrometer (e.g., Mitutoyo 293-100 type, accuracy 0.1 μm) can be used.

[0190] In this application, the porosity of the negative electrode film layer has a meaning known in the art and can be measured by a method known in the art. An exemplary test method is to take a negative electrode sheet that is coated on one side and cold pressed (if the negative electrode sheet is coated on both sides, the negative electrode film layer on one side can be wiped off first), punch it into a small disk sample with a certain area, and measure the apparent volume V of the negative electrode sheet. 1 Refer to GB / T24586-2009, use inert gas (such as helium gas or nitrogen gas) as the medium, adopt gas replacement method, and use a density tester to measure the true volume V of the negative electrode sheet. 2 Test the porosity of the negative electrode membrane layer = (V 1 -V 2 ) / V 1 × 100%. The accuracy of the test results can be improved by testing multiple (e.g., 30) samples of negative electrode sheets that have good appearance and no powdering at the edges and averaging the results. The test equipment used can be a Micromeritics AccuPyc II 1340 true density tester.

[0191] In the present application, the OI value of the negative electrode film layer has a meaning known in the art, and can be tested by using equipment and methods known in the art. For example, it can be tested using an X-ray diffraction device (e.g., Bruker D8 Discover). The test is performed by referring to JIS K 0131-1996 and JB / T 4220-2011 to obtain an X-ray diffraction pattern of the negative electrode sheet, and the OI value = I 004 / I 110The OI value of the negative electrode film layer is calculated based on I 004 is the integrated area of ​​the diffraction peak of the crystalline carbon 004 plane in the negative electrode film layer, and I 110 is the integrated area of ​​the diffraction peak of the crystalline carbon 110 plane in the negative electrode film layer. In the X-ray diffraction analysis test of this application, a copper target is used as the anode target, CuKα radiation is used as the radiation source, the radiation wavelength is λ=1.5418 angstroms, the scanning 2θ angle range is 20°~80°, and the scanning speed is 4° / min.

[0192] In addition, various parameters of the first active material, the second active material, or the negative electrode film layer can be tested by sampling from a secondary battery manufactured according to the following steps.

[0193] Discharge the secondary battery (for safety, the secondary battery is generally fully discharged), remove the secondary battery, take out the negative electrode sheet, and soak the negative electrode sheet in dimethyl carbonate for a certain time (for example, 2h to 10h), then take out the negative electrode sheet and dry it at a certain temperature and time (for example, 60°C, 4h or more), and take out the negative electrode sheet after drying. In this case, the negative electrode sheet after drying can be sampled to test each parameter related to the above-mentioned negative electrode film layer, such as the areal density, compressed density, porosity, OI value, etc. of the negative electrode film layer.

[0194] The dried negative electrode sheet is sintered at a certain temperature and time (e.g., 400°C, 2h or more), and one area is arbitrarily selected from the sintered negative electrode sheet. First, the second active material is sampled (the powder may be scraped off using a blade for sampling), and the sampling position is the second area of ​​the negative electrode film layer. Then, the first active material is sampled in the same manner, and the sampling position is the first area of ​​the negative electrode film layer. The collected first and second active materials are sieved (e.g., sieved through a 200 mesh sieve), and finally the first and second active material samples are obtained for testing the parameters of each of the above materials in the present application. [Method of manufacturing negative electrode sheet]

[0195] The present application further provides a method for manufacturing the negative electrode sheet of the present application, the method including the steps of providing a first slurry containing a first active material and a second slurry containing a second active material, coating the first slurry on a negative electrode current collector, coating the second slurry on the first slurry, drying, and cold pressing to obtain a negative electrode sheet.

[0196] In some embodiments, the first active material and optional conductive agent, optional adhesive, and optional other auxiliary agents can be dispersed in a solvent (e.g., deionized water) to form a first slurry.

[0197] In some embodiments, the second active material and optional conductive agent, optional adhesive, and optional other auxiliary agents can be dispersed in a solvent (e.g., deionized water) to form a second slurry.

[0198] In some embodiments, the first active material comprises a first carbon-based material or a mixture of a first carbon-based material and a third carbon-based material.

[0199] In certain embodiments, the second active material comprises a second carbon-based material.

[0200] In certain embodiments, the first slurry and / or the second slurry further comprises a silicon-based material.

[0201] The first and second slurries may be applied simultaneously in one step, or may be applied in two separate steps. In some embodiments, the first and second slurries are applied simultaneously in one step. By applying the first and second slurries simultaneously in one step, the resistance of the negative electrode film layer can be reduced, thereby further improving the kinetic and cycle performance of the secondary battery.

[0202] The coating weight of the first slurry and the second slurry can be adjusted according to the actual situation.

[0203] In the present application, the above-mentioned first active material, second active material, etc. are commercially available or are produced by the following method of the present application.

[0204] In some embodiments, the method for producing the first carbon-based material includes the steps of: providing a raw material having a plurality of pore structures; uniformly mixing the raw material with a filler in a predetermined ratio; and then heating the raw material to a first temperature T 1 At the first time t 1 Step 2 is to keep the temperature and, after completion, cool the mixture to room temperature to obtain an intermediate, and then to heat the intermediate to a second temperature T 2 At the second time t 2 and step 3 of obtaining a first carbon-based material after the completion of the incubation.

[0205] In some embodiments, in step 1, the raw material for producing the first carbon-based material includes natural graphite. Optionally, the natural graphite includes one or more of flake graphite, natural spheroidal graphite, and microcrystalline graphite, more preferably natural spheroidal graphite.

[0206] "Natural spherical graphite" refers to natural graphite having a spherical or nearly spherical shape, and does not mean that all natural graphite particles are controlled to be ideal spheres. In some embodiments, natural spherical graphite having a desired particle size and shape can be obtained by performing a pretreatment on flake graphite. Optionally, the pretreatment includes a process such as crushing, classification, spheroidization, and purification.

[0207] In some embodiments, in step 1, the graphitization degree of the raw material is 94.5% or more, which is advantageous for adjusting the graphitization degree and layer spacing of the first carbon-based material.

[0208] In some embodiments, in step 1, the volume distribution particle size Dv50 of the raw material may be 8.0 μm to 25.0 μm, and optionally 10.0 μm to 22.0 μm.

[0209] In some embodiments, in step 1, the specific surface area of ​​the raw material is 2.5 m 2 / g or more, and optionally 2.5m 2 / g~10.0m 2 / g. When the specific surface area of ​​the raw material is within the above range, it is advantageous to carry out a subsequent filling process to obtain a first carbon-based material with a desired specific surface area, and it is also advantageous for the first carbon-based material to have a high capacity and a high initial coulombic efficiency. It is also advantageous for the first carbon-based material to have a better kinetic performance.

[0210] In some embodiments, in step 2, the softening point temperature of the filler is 100° C. to 170° C. Optionally, the softening point temperature of the filler is 106° C. to 170° C., 106° C. to 160° C., 106° C. to 152° C., 106° C. to 146° C., 106° C. to 138° C., 112° C. to 160° C., 112° C. to 152° C., 112° C. to 146° C., or 112° C. to 138° C.

[0211] In some embodiments, in step 2, the volume distribution particle size Dv50 of the filler is less than 6 μm, and optionally 1 μm-6 μm, 1 μm-5 μm, 2 μm-5 μm, or 3 μm-5 μm, which is advantageous for the filler to be filled into the pore structure of the raw material after being melted by heat, and is also advantageous for improving the dispersion uniformity of the filler and the raw material.

[0212] In some embodiments, in step 2, the coking value of the filler is 20%-48%, optionally 25%-38%. In the present application, the coking value of the filler has a meaning known in the art and can be measured by instruments and methods known in the art, for example, by referring to GB / T 8727-2008.

[0213] In certain embodiments, in step 2, the filler material comprises one or more of coal pitch, petroleum pitch, polymer, and resin, optionally comprising one or more of coal pitch and petroleum pitch.

[0214] In some embodiments, in step 2, the mass ratio of the filler to the raw material is (10-40):100, and optionally is (10-30):100, (10-25):100, (10-20):100, (12-30):100, (12-20):100, (14-28):100, or (15-25):100.

[0215] In step 2, by adjusting one or more parameters of the type of filler, softening point, caulking value, amount of filler, etc., within the above range, it is advantageous to adjust the number of holes and / or the size of the holes in the outer region and the inner region of the first carbon-based material within a suitable range, and the S of the first carbon-based material 2 / S 1 It is advantageous to adjust the temperature to within an appropriate range.

[0216] By adjusting parameters such as the type, softening point, caulking value, and amount of the filler within the above ranges, the filler does not have a high viscosity and maintains good fluidity after being melted by heat, and the raw material particles are less likely to adhere to each other, thereby reducing the aggregation of the raw material particles in the subsequent manufacturing process. As a result, problems such as an increase in surface defects and an increase in surface active sites of the first carbon-based material particles due to the need to increase the depolymerization process can be reduced.

[0217] In some embodiments, in step 2, the raw material and the filling material are uniformly mixed in a predetermined ratio, and then heated to a first temperature T 1 The temperature increase process is a stepwise temperature increase process.

[0218] In some embodiments, the stepwise temperature increase process includes a first temperature increase process, a second temperature increase process, and a third temperature increase process.

[0219] In some embodiments, the first temperature-raising process involves raising the temperature to 200° C. to 250° C. and maintaining the temperature for 0.5 h to 3 h.

[0220] In some embodiments, the second temperature increase process involves increasing the temperature to 450° C. to 550° C. and maintaining the temperature for 0 h to 2 h. When the temperature maintenance time is 0 h, no maintenance process is performed when the temperature is increased to within the range of 450° C. to 550° C., and the first temperature T 1 This indicates that the temperature will continue to rise until

[0221] In some embodiments, the third heating process is performed at the first temperature T 1 The temperature is raised to t 1 Keep warm.

[0222] In the stepwise heating process, the temperature is first raised to 200°C-250°C, and since the heating temperature is higher than the softening point temperature of the filler, the filler melts and softens due to heat, and is kept warm for 0.5h-3h to allow it to flow and fill into the pore structure of the raw material. Then, the temperature is raised to 450°C-550°C, and the melted and softened filler undergoes a carbonization reaction, gradually turning into a semi-coked state and becoming a viscous liquid or solid, thereby preventing the filler from entering all of the pore structure of the raw material. Finally, the temperature is raised to the first temperature, and the filler undergoes a carbonization reaction, thereby effectively filling the pore structure occupied by the filler.

[0223] In some embodiments, in step 2, the first temperature T 1 For example, the rate of temperature rise may be 1° C. / min, 2° C. / min, 3° C. / min, 4° C. / min, 5° C. / min, 6° C. / min, 7° C. / min, 8° C. / min, 9° C. / min, 10° C. / min, or any range of the above values. Optionally, the rate of temperature rise is 1.5° C. / min to 8° C. / min, 1.5° C. / min to 6° C. / min, 2° C. / min to 6° C. / min, or 2° C. / min to 5° C. / min.

[0224] In some embodiments, the heating rate of the first heating process may be 1° C. / min to 10° C. / min, and may be selectable between 1.5° C. / min to 8° C. / min, 1.5° C. / min to 6° C. / min, 2° C. / min to 6° C. / min, or 2° C. / min to 5° C. / min.

[0225] In some embodiments, the heating rate of the second heating process may be 1° C. / min to 10° C. / min, and optionally 2° C. / min to 8° C. / min.

[0226] In some embodiments, the heating rate of the third heating process may be 1° C. / min to 10° C. / min, and optionally 2° C. / min to 8° C. / min.

[0227] In some embodiments, in step 2, the first temperature T 1 For example, the first temperature T 1 The first temperature T may be 700° C., 750° C., 800° C., 850° C., 900° C., 950° C., 1000° C., 1050° C., 1100° C., 1200° C., or a range of any value greater than or equal to the first temperature T 1 are 750℃~1100℃, 800℃~1100℃, and 850℃~1000℃.

[0228] In some embodiments, in step 2, the first time t 1 For example, the first hour t 1 Optionally, the first time t 1 is 2h~4h.

[0229] In some embodiments, in step 2, the heat treatment can be carried out in equipment capable of performing a programmable temperature ramp, such as an intermediate frequency furnace, a roller hearth kiln, a rotary kiln, a pusher hearth kiln, a vertical granulator, a horizontal granulator, a vertical reactor, a horizontal reactor, or a drum furnace.

[0230] In some embodiments, the heat treatment atmosphere may be a protective gas atmosphere in step 2. The protective gas may include one or more of nitrogen gas, argon gas, and helium gas.

[0231] In step 2, by adjusting one or more of the heating rate, the first temperature, the first time, the heating process, etc., within the above range, it is advantageous to adjust the number of holes and / or the size of the holes in the outer region and the inner region of the first carbon-based material within a suitable range, and further to adjust the S of the first carbon-based material. 2 / S 1 It is advantageous to adjust the temperature to within an appropriate range.

[0232] In some embodiments, in step 3, the second temperature T 2 The second temperature T 2 are 2040℃~2500℃, 2040℃~2460℃, 2040℃~2420℃, 2040℃~2380℃, 2080℃~2500℃, 2080℃~2460℃, 2080℃~2420℃, and 2080℃~2380℃.

[0233] In some embodiments, in step 3, the second time t 2 For example, the second time t 2 Optionally, the second time t 2 is 2h~5h.

[0234] In certain embodiments, in step 3, the heat treating can be performed in an intermediate frequency furnace, a box type graphitization furnace, an Acheson type graphitization furnace, a continuous graphitization furnace, or an internal in-line graphitization furnace.

[0235] In some embodiments, in step 3, the intermediate frequency furnace, continuous graphitization heat treatment atmosphere may be a protective gas atmosphere. The protective gas may include one or more of nitrogen gas, argon gas, and helium gas.

[0236] In step 3, by adjusting one or more of the second temperature and the second time within the above range, it is advantageous to adjust the content of random carbon in the first carbon-based material within a suitable range, and the I of the first carbon-based material is D / I G and / or it is advantageous to adjust parameters such as the degree of graphitization within appropriate ranges.

[0237] In the above-mentioned method for producing the first carbon-based material, one or more of the parameters of natural graphite, the parameters of the filler, the heating rate, the first temperature, the first time, the heating process, the second temperature, the second time, etc. are adjusted within the above-mentioned ranges to obtain the S of the first carbon-based material. 2 / S 1 , I D / I G It is advantageous to adjust parameters such as graphitization degree, gram volume, specific surface area, particle size, powder pressed density, tap density, linseed oil adsorption, etc.

[0238] In some embodiments, the method for producing the second carbon-based material includes mixing a raw material with an organic carbon source, followed by a carbonization process, and obtaining a second carbon-based material after completion of the process. Optionally, the raw material includes at least one of artificial graphite and natural graphite, and optionally includes natural graphite.

[0239] In some embodiments, the organic carbon source can be any carbon-containing material known in the art that is suitable for coating, and can include, for example, one or more of coal pitch, petroleum pitch, phenolic resin, coconut shell, and the like.

[0240] In some embodiments, the carbonization temperature may be between 900°C and 1300°C.

[0241] In the method for producing the second carbon-based material, one or more parameters of raw material parameters (e.g., particle size, specific surface area, particle size distribution, type, etc.), amount of organic carbon source added, carbonization temperature, carbonization time, etc. are adjusted to produce the second carbon-based material I. D / I G It is advantageous to adjust parameters such as the degree of graphitization, gram volume, particle size, specific surface area, pressed density of the powder, tap density, etc. [Positive electrode sheet]

[0242] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector. For example, the positive electrode current collector has two surfaces facing each other in a thickness direction thereof, and the positive electrode film layer is provided on one or both of the two facing surfaces of the positive electrode current collector.

[0243] The positive electrode current collector may be a metal foil sheet or a composite current collector. An example of the metal foil sheet may be aluminum foil. The composite current collector may include a polymeric material base layer and a metal material layer formed on at least one surface of the polymeric material base layer. For example, the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. For example, the polymeric material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0244] The positive electrode membrane layer typically includes a positive electrode active material, an optional adhesive, and an optional conductive agent. The positive electrode membrane layer is typically formed by applying a positive electrode slurry to the positive electrode current collector, drying, and cold pressing. The positive electrode slurry is typically formed by dispersing the positive electrode active material, the optional conductive agent, the optional adhesive, and any other components in a solvent and stirring uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP). For example, the adhesive used in the positive electrode membrane layer may include any one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin. For example, the conductive agent used in the positive electrode film layer may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0245] As the positive electrode active material, any positive electrode active material for secondary batteries known in the art can be used.

[0246] When the secondary battery of the present application is a lithium-ion battery, the positive electrode active material includes, but is not limited to, one or more of lithium-containing transition metal oxides, lithium-containing phosphates, and modified compounds thereof. Examples of the lithium transition metal oxides include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and modified compounds thereof. Examples of the lithium-containing phosphates include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite material of lithium manganese iron phosphate and carbon, and modified compounds thereof.

[0247] In some embodiments, in order to further improve the energy density of the secondary battery, the positive electrode active material used in the lithium-ion battery may include one or more of lithium transition metal oxides and modified compounds thereof having the general formula Li a Ni b Co c M d O e A f where 0.8 ≦ a ≦ 1.2, 0.5 ≦ b < 1, 0 < c < 1, 0 < d < 1, 1 ≦ e ≦ 2, 0 ≦ f ≦ 1, M is one or more selected from Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, and B, and A is one or more selected from N, F, S, and Cl.

[0248] In some embodiments, by way of example, the positive electrode active material for the lithium-ion battery is LiCoO 2 、LiNiO 2 、LiMnO 2 、LiMn 2 O 4 、LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811), LiNi 0.85 Co 0.15 Al 0.05 O 2 , LiFePO 4 and LiMnPO 4 It may contain one or more of the following:

[0249] In the present application, the modified compounds of the above-mentioned positive electrode active materials are obtained by performing doping modification and / or surface coating modification on the positive electrode active materials. [Electrolyte]

[0250] In some embodiments, the electrolyte is an electrolyte solution including an electrolyte salt and a solvent.

[0251] The type of the electrolyte salt is not specifically limited and may be selected according to actual needs.

[0252] When the secondary battery of the present application is a lithium ion battery, the electrolyte salt is, for example, lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium bisfluorosulfonylimide (LiFSI), lithium bistrifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB) and lithium bis(oxalatoborate) (LiBOB), lithium difluorophosphate (LiPO2 F 2 ), lithium difluorobisoxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0253] The type of the solvent is not particularly limited and can be selected according to actual needs. In some embodiments, by way of example, the organic solvent may include one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0254] In some embodiments, the electrolyte may further include additives as necessary. For example, the additives may include a negative electrode film-forming additive, a positive electrode film-forming additive, or an additive capable of improving a certain performance of a secondary battery, such as an additive for improving the overcharge performance of a secondary battery, an additive for improving the high temperature performance of a secondary battery, or an additive for improving the low temperature output performance of a secondary battery. [Separator]

[0255] In the present application, the type of the separator is not particularly limited, and any known porous structure separator having good chemical stability and mechanical stability can be selected.

[0256] In some embodiments, the separator may be made of one or more of the following materials: glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a monolayer film or a multilayer composite film. When the separator is a multilayer composite film, the materials of each layer may be the same or different.

[0257] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet can be wound or stacked to produce an electrode assembly.

[0258] In some embodiments, the secondary battery may include an exterior case that is used to seal the electrode assembly and electrolyte described above.

[0259] In some embodiments, the exterior may be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The exterior may be a soft package, such as a bag soft package. The material of the soft package may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0260] The shape of the secondary battery of the present application is not particularly limited, and may be cylindrical, rectangular, or any other shape. Fig. 5 shows a secondary battery 5 having a rectangular structure as an example.

[0261] In some embodiments, as shown in FIG. 6, the exterior may include a case 51 and a cover plate 53. The case 51 includes a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate are surrounded to form a receiving chamber. The case 51 has an opening communicating with the receiving chamber, and the cover plate 53 covers the opening to close the receiving chamber. The positive electrode sheet, the negative electrode sheet and the separator may form an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is packaged in the receiving chamber. The electrolyte is permeated into the electrode assembly 52. ​​The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and may be adjusted according to demand.

[0262] The method of manufacturing the secondary battery of the present application is well known. In some embodiments, a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte solution can be assembled to form a secondary battery. For example, a positive electrode sheet, a separator, and a negative electrode sheet can be formed into an electrode assembly by a winding process or a lamination process, and the electrode assembly can be placed in an outer casing, dried, and then an electrolyte solution can be injected, and a secondary battery can be obtained through processes such as vacuum sealing, standing, chemical formation, and shaping.

[0263] In some embodiments of the present application, the secondary battery of the present application may be assembled into a battery module, and the number of secondary batteries included in the battery module may be multiple, and the specific number may be adjusted according to the application and capacity of the battery module.

[0264] Fig. 7 is a schematic diagram of an example battery module 4. As shown in Fig. 7, in the battery module 4, the multiple secondary batteries 5 may be arranged in sequence along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the multiple secondary batteries 5 may be fixed by a fastener.

[0265] Optionally, the battery module 4 further includes an outer case having an accommodating space, and the multiple secondary batteries 5 are accommodated in the accommodating space.

[0266] In some embodiments, the battery modules may be assembled into a battery pack, and the number of battery modules included in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0267] 8 and 9 are schematic diagrams of an example battery pack 1. As shown in Fig. 8 and 9, the battery pack 1 may include a battery housing and a plurality of battery modules 4 provided in the battery housing. The battery housing includes an upper housing 2 and a lower housing 3, and the upper housing 2 covers the lower housing 3 to form an enclosed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery housing in any manner.

[0268] The present application further provides a power consuming device including at least one of the secondary batteries, battery modules, or battery packs of the present application. The secondary batteries, battery modules, or battery packs may be used as a power source for the power consuming device, or may be used as an energy storage means for the power consuming device. The power consuming device may be, but is not limited to, a mobile device (e.g., a mobile phone, a tablet computer, a notebook computer, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.

[0269] The power consumption device can select a secondary battery, a battery module or a battery pack according to the demand.

[0270] 10 is a schematic diagram of an example power consuming device, such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. A battery pack or battery module may be employed to meet the high power and high energy density requirements of the power consuming device.

[0271] Another example of the power consuming device may be a mobile phone, a tablet computer, a notebook computer, etc. Generally, the power consuming device is required to be thin and may employ a secondary battery as a power source. Working Example

[0272] The following examples are provided to more specifically illustrate the disclosure of the present application, and these examples are merely intended to interpret the present application, since it is obvious to those skilled in the art that various modifications and changes can be made within the scope of the disclosure of the present application.Unless otherwise specified, all parts, percentages, and ratios described in the following examples are calculated based on mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing, and the equipment used in the examples are commercially available.

[0273] In each of the following Examples and Comparative Examples, the first carbon-based material can be produced by the following method of the present application. (1) Production of the first carbon-based material

[0274] The flake graphite was mechanically crushed, classified, spheroidized, and refined to obtain natural spheroidal graphite. The obtained natural spheroidal graphite was mixed with petroleum pitch, and the mixed material was placed in a programmable heating device and subjected to a stepwise heating heat treatment. After completion, the material was cooled to room temperature to obtain an intermediate. The obtained intermediate was placed in a graphitization furnace and subjected to a heat treatment. After completion, the material was demagnetized and sieved to obtain a first carbon-based material. In the above process, the volume average particle diameter Dv50 and S of the first carbon-based material were 2 / S 1 , I D / I G can be controlled in accordance with the manufacturing process of the first carbon-based material of the present application so that the parameters are within the ranges shown in Table 1.

[0275] The first carbon-based material, S 2 / S 1 is obtained by testing in the following way:

[0276] The adhesive for sample preparation is mixed uniformly with the powder of the first carbon-based material, and then applied to a copper foil and dried at 60°C for 30 min to prepare for use. The sample is cut into a size of 6 mm x 6 mm and attached to the sample stage of a CP-type argon ion cross-section polisher. The sample is cut using a plasma beam to obtain a cross section of the first carbon-based material, and the cross section of the first carbon-based material passes through the center of the first carbon-based material particle. The test equipment can be an IB-09010 CP-type argon ion cross-section polisher from JEOL Co., Ltd., Japan. The cross section of the first carbon-based material was scanned using a scanning electron microscope. The test can refer to JY / T010-1996. The test equipment can be a Sigma 300-type scanning electron microscope from ZEISS Co., Ltd., Germany. The region extending from the particle surface of the first carbon-based material to the inside of the particle at a distance of 0.25L is the outer region, and the region inside the outer region is the inner region, where L indicates the short axis length of the particle of the first carbon-based material. Using image processing software, the total pore area S of the outer region of the first carbon-based material was 1 and the total pore area S of the inner region of the first carbon-based material. 2 The image processing software may be AVIZO.

[0277] In each of the following Examples and Comparative Examples, the second carbon-based material can be produced by the following method of the present application. (2) Manufacture of secondary carbon-based materials

[0278] After mixing natural graphite and petroleum pitch, the mixture was carbonized at 900°C to 1300°C, and then sieved to obtain the second carbon-based material. D / I G One or more of the parameters such as the amount of natural graphite and / or petroleum pitch added, the carbonization temperature, the carbonization time, etc. can be adjusted so that the parameters are within the ranges shown in Table 1.

[0279] In each of the following Examples and Comparative Examples, the third carbon-based material is commercially available. The secondary batteries of Examples 1 to 30 were all produced by the following method.

[0280] The first carbon-based material (see Table 1 for details), the conductive agent carbon black (Super P), the thickener sodium carboxymethylcellulose, and the adhesive styrene butadiene rubber were thoroughly stirred and mixed in a weight ratio of 96.4:1:1.2:1.4 in an appropriate amount of deionized water as a solvent to form a first slurry. The second carbon-based material (see Table 1 for details), the conductive agent carbon black (Super P), the thickener sodium carboxymethylcellulose, and the adhesive styrene butadiene rubber were thoroughly stirred and mixed in a weight ratio of 96.4:1:1.2:1.4 in an appropriate amount of deionized water as a solvent to form a second slurry. The first and second slurries are extruded simultaneously by a double cavity coating die. The first slurry is applied to the copper foil of the negative electrode current collector, and the second slurry is applied to the first slurry. After drying and cold pressing, a negative electrode sheet is obtained. The application weights of the first and second slurries are the same.

[0281] LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523), carbon black (Super P) as a conductive agent, and polyvinylidene fluoride as an adhesive were mixed in a weight ratio of 96:2:2, and an appropriate amount of NMP as a solvent was added and stirred uniformly to obtain a positive electrode slurry. The positive electrode slurry was applied to two surfaces of aluminum foil as a positive electrode current collector, and after drying and cold pressing, a positive electrode sheet was obtained.

[0282] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent, and then LiPF 6 was dissolved in the organic solvent to prepare an electrolyte solution with a concentration of 1 mol / L.

[0283] The positive and negative electrode sheets prepared above were arranged in order using a polyethylene film as a separator, and the separator was placed between the positive and negative electrode sheets to perform an isolating function, and then rolled up to obtain an electrode assembly. The electrode assembly was placed in an outer casing, dried, and then an electrolyte was injected, and the secondary battery was obtained through processes such as vacuum sealing, standing, chemical formation, and shaping. Comparative Example 1

[0284] The secondary battery of Comparative Example 1 was manufactured by a method similar to that of Example 1, with the difference being the positions at which the first and second slurries were applied. The second slurry prepared in Example 1 was applied to the copper foil of the negative electrode current collector, and the first slurry prepared in Example 1 was applied to the second slurry prepared in Example 1. After drying and cold pressing, a negative electrode sheet was obtained. The test results are shown in Table 2. Example 31

[0285] The secondary battery of Example 31 was manufactured by a method similar to that of Example 1, with the difference being the manufacture of a first slurry. The first and third carbon-based materials (see Table 3 for details, mass ratio 50:50), carbon black (Super P) as a conductive agent, sodium carboxymethylcellulose as a thickener, and styrene butadiene rubber as an adhesive were thoroughly stirred and mixed in a weight ratio of 96.4:1:1.2:1.4 in an appropriate amount of deionized water as a solvent to form a first slurry. Performance Testing (1) Testing the rapid charging performance of secondary batteries

[0286] At 25°C, the secondary battery is charged at a constant current of 0.33C up to 4.3V, then charged at a constant voltage until the current reaches 0.05C. After leaving the battery to stand for 5 minutes, the secondary battery is discharged at a constant current of 0.33C down to 2.8V, and the actual capacity is taken as C0.

[0287] After that, the secondary battery was charged at a constant current of 1.0C0, 1.3C0, 1.5C0, 1.8C0, 2.0C0, 2.3C0, 2.5C0, and 3.0C0 in order to a negative electrode cutoff potential of 4.3V or 0V (based on the first one reached). After each charge, the battery was discharged at 1C0 to 2.8V, and then charged at different charge rates of 10%, 20%, 30%, ..., and 80% SOC (State of Charge). The negative electrode potential corresponding to the charging up to 0 V was recorded, and charge rate-negative electrode potential curves at different SOC states were drawn and linearly fitted to obtain the charge rates corresponding to the negative electrode potential of 0 V at different SOC states. The charge rates are the charge windows at the SOC states, which are C10% SOC, C20% SOC, C30% SOC, C40% SOC, C50% SOC, C60% SOC, C70% SOC, and C80% SOC, respectively. The charge time T (assuming that lithium does not precipitate in the secondary battery) from 10% SOC to 80% SOC of the secondary battery was calculated based on the formula (60 / C20% SOC+60 / C30% SOC+60 / C40% SOC+60 / C50% SOC+60 / C60% SOC+60 / C70% SOC+60 / C80% SOC)×10%, in min. The shorter the charging time, the better the dynamic performance of the secondary battery. (2) Testing the storage performance of secondary batteries

[0288] At 25°C, the secondary battery prepared above is charged at a constant current of 1C up to 4.3V, then charged at a constant voltage until the current becomes 0.05C, and after leaving it to stand for 5 minutes, the secondary battery is discharged at a constant current of 1C up to 2.8V, and the discharge capacity at this time is recorded and used as the discharge capacity before storage.

[0289] At 25°C, the secondary battery produced above was charged at a constant current of 1C up to 4.3V, and then charged at a constant voltage until the current reached 0.05C. The secondary battery was then placed in a thermostatic chamber at 60°C and stored for 200 days. The capacity retention rate (%) of the secondary battery stored at 60°C for 200 days = discharge capacity after storage / discharge capacity before storage × 100%.

[0290] As can be seen from the results in Tables 1 to 3, the first region of the negative electrode film layer contains a first carbon-based material, the second region contains a second carbon-based material, the first carbon-based material has a pore structure, and the I D / I G The second carbon-based material is D / I G Since the capacitance is smaller than 100 kΩ, it is possible to achieve both good dynamic performance and good storage performance on the premise that the battery has a high energy density.

[0291] In the negative electrode film layer of Comparative Example 1, the first carbon-based material I D / I G is the second carbon-based material I D / I G In this case, the battery's fast charging capability, dynamic performance, and storage performance will be poor.

[0292] The present application is not limited to the above-mentioned embodiment. The above-mentioned embodiment is merely an example, and any embodiment having substantially the same configuration as the technical idea within the technical scope of the present application and having similar effects is included in the technical scope of the present application. In addition, within the scope of the present application, various modifications that a person skilled in the art can conceive of, and other forms constructed by combining some of the components in the embodiment are also included in the scope of the present application.

[0293] [Table 1]

[0294] [Table 2]

[0295] [Table 3]

Claims

1. A secondary battery including a negative electrode sheet, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer formed on at least one surface of the negative electrode current collector, the negative electrode film layer includes a first surface remote from the negative electrode current collector and a second surface opposite to the first surface, The thickness of the negative electrode film layer is H, a region within a thickness range of 0.3H from the second surface of the negative electrode film layer is a first region of the negative electrode film layer, and a region within a thickness range of 0.3H from the first surface of the negative electrode film layer is a second region of the negative electrode film layer, the first region includes a first active material and the second region includes a second active material; the first active material comprises a first carbon-based material, and the second active material comprises a second carbon-based material; The first carbon-based material has a pore structure, and I of the first carbon-based material Ｄ / I Ｇ is the I of the second carbon-based material Ｄ / I Ｇ is smaller than I Ｄ is 1350±50 cm of the Raman spectrum －１ D peak intensity at I Ｇ is 1580±50 cm in the Raman spectrum. －１ The G peak intensity at Secondary battery.

2. I of the second carbon-based material Ｄ / I Ｇ I of the first carbon-based material Ｄ / I Ｇ 2. The secondary battery according to claim 1, wherein the ratio A is 0.80 or less, and selectably 0.32 to 0.

77.

3. I of the first carbon-based material Ｄ / I Ｇ is between 0.152 and 0.280, optionally between 0.155 and 0.220; and / or I of the second carbon-based material Ｄ / I Ｇ is between 0.230 and 0.500, optionally between 0.235 and 0.450; The secondary battery according to claim 1 or 2.

4. The secondary battery according to claim 1 , wherein a volume distribution particle size Dv50 of the second carbon-based material is smaller than a volume distribution particle size Dv50 of the first carbon-based material.

5. The secondary battery according to claim 1 , wherein a compressed density of powder of the second carbon-based material at a pressure of 20,000 N is smaller than a compressed density of powder of the first carbon-based material at a pressure of 20,000 N.

6. The secondary battery according to claim 1 , wherein the second carbon-based material includes at least one of artificial graphite and natural graphite, and optionally, the second carbon-based material includes natural graphite.

7. In the X-ray diffraction spectrum of the first carbon-based material, there is no diffraction peak of a 3R phase 012 plane, and / or In the X-ray diffraction spectrum of the second carbon-based material, a diffraction peak of a 3R phase 012 plane is present. The secondary battery according to claim 1 .

8. The second carbon-based material has a pore structure and can be selectively configured to have a ratio of a pore area in a cross section of a particle of the first carbon-based material to a cross section of the particle of the first carbon-based material of α １ and the ratio of the pore area in the cross section of the second carbon-based material particle to the cross-sectional area of ​​the second carbon-based material particle is α ２ And α １ <α ２ The secondary battery according to claim 1 ,

9. The first carbon-based material and / or the second carbon-based material has a thickness of 0.15 μm. ２ and optionally, one or more pore structures having a pore area of ​​0.15 μm or more. ２ ~2.0μm ２ The secondary battery according to claim 1 , comprising one or more pore structures having a pore area of

10. The first carbon-based material includes an outer region and an inner region located inside the outer region, the outer region is a region extending from the surface of the first carbon-based material particle to the inside of the particle by a distance of 0.25L, where L is the minor axis length of the first carbon-based material particle; The total pore area of ​​the outer region is defined as S １ The total pore area of ​​the inner region is S ２ And S ２ >S １ , selectably, 1.5≦S ２ / S １ ≦500, 2≦S ２ / S １ ≦450; The secondary battery according to claim 1 .

11. The area of ​​the pore structure in the outer region of the first carbon-based material is 0.2 μm ２ or less, optionally 0.10 μm ２ and / or The inner region of the first carbon-based material is 0.15 μm ２ and optionally, one or more pore structures having an area of ​​0.15 μm or more. ２ ~2.0μm ２ and one or more pore structures having an area of The secondary battery according to claim 10.

12. The secondary battery according to claim 1 , wherein at least a part of the surface of the first carbon-based material and / or the second carbon-based material has a coating layer, and optionally, the coating layer comprises carbon.

13. the first carbon-based material and / or the second carbon-based material comprises primary particles; Optionally, the number ratio of the primary particles in the first carbon-based material is 50% or more; Optionally, the number ratio of the primary particles in the second carbon-based material is 50% or more. The secondary battery according to claim 1 .

14. The secondary battery according to claim 1 , wherein the first carbon-based material satisfies at least one of the following conditions: (1) The specific surface area of ​​the first carbon-based material is 2.1 m ２ / g or less, and selectable 1.1m ２ / g to 2.0 m ２ / g. (2) The first carbon-based material has a volume distribution particle size Dv50 of 8.0 μm to 25.0 μm, and optionally 10.0 μm to 22.0 μm. (3) The first carbon-based material has a volume distribution particle size Dv90 of 16.0 μm to 45.0 μm, and optionally 16.5 μm to 42.0 μm. (4) The particle size distribution (Dv90-Dv10) / Dv50 of the first carbon-based material is less than or equal to 1.55, and optionally is between 0.90 and 1.

50. (5) The compressed density of the powder of the first carbon-based material at a pressure of 20,000 N is 1.65 g / cm ３ ~2.0g / cm ３ and optionally 1.68 g / cm ３ ~1.98g / cm ３ It is. (6) The tap density of the first carbon-based material is 0.85 g / cm ３ ~1.30g / cm ３ and optionally 0.90 g / cm ３ ~1.25g / cm ３ It is. (7) The graphitization degree of the first carbon-based material is 95.5% or more, and optionally 95.5% to 98.0%. (8) The gram capacity of the first carbon-based material is greater than or equal to 355 mAh / g, and optionally between 355 mAh / g and 370 mAh / g. (9) In an X-ray diffraction spectrum of the first carbon-based material, it has a diffraction peak of a 3R phase (101) plane. (10) The adsorption amount of 100 g of the first carbon-based material to linseed oil is 30 ml to 47 mL.

15. The secondary battery according to claim 1 , wherein the second carbon-based material satisfies at least one of the following conditions: (1) The specific surface area of ​​the second carbon-based material is 1.8 m ２ / g or more, and selectable 1.9m ２ / g to 3.5m ２ / g. (2) The Dv50 of the second carbon-based material is between 8.0 μm and 15.0 μm, and optionally between 10.0 μm and 15.0 μm. (3) The particle size distribution (Dv90-Dv10) / Dv50 of the second carbon-based material is less than or equal to 1.65, and optionally is between 0.90 and 1.

65. (4) The compressed density of the powder of the second carbon-based material at a pressure of 20,000 N is 1.60 g / cm ３ ~1.95g / cm ３ and optionally 1.65 g / cm ３ ~1.92g / cm ３ It is. (5) The tap density of the second carbon-based material is 0.85 g / cm ３ ~1.25g / cm ３ and optionally 0.90 g / cm ３ ~1.25g / cm ３ It is. (6) The degree of graphitization of the second carbon-based material is between 94.5% and 98.0%, and optionally between 95.0% and 97.5%. (7) The gram capacity of the second carbon-based material is between 355 mAh / g and 372 mAh / g, optionally between 356 mAh / g and 370 mAh / g. (8) In the X-ray diffraction spectrum of the second carbon-based material, it has a diffraction peak of a 3R phase (101) plane.

16. The secondary battery of claim 1 , wherein the first active material further comprises a third carbon-based material, and the third carbon-based material comprises artificial graphite in a primary particle form.

17. The negative electrode sheet according to claim 16 , wherein the surface of the primary particle form of the artificial graphite does not have a carbon coating layer.

18. 18. The secondary battery according to claim 16, wherein a mass ratio of the third carbon-based material in the first active material is 80 wt % or less, and optionally 20 wt % to 70 wt %.

19. The secondary battery according to claim 16 , wherein the third carbon-based material satisfies at least one of the following conditions: (1) The graphitization degree of the third carbon-based material is 92.5% to 95.5%, and optionally 92.7% to 95.5%. (2) The powder OI value of the third carbon-based material is 4.5 to 11.5, and optionally 4.5 to 11.

0. (3) The particle size distribution (Dv90-Dv10) / Dv50 of the third carbon-based material is less than or equal to 1.65, and optionally is between 0.90 and 1.

65. (4) The third carbon-based material has a volume distribution particle size Dv50 of 12.0 μm to 22.0 μm, and optionally 13.5 μm to 20.0 μm. (5) The specific surface area of ​​the third carbon-based material is 1.0 m ２ / g to 2.0 m ２ / g, and optionally 1.05m ２ / g to 1.95 m ２ / g. (6) The tap density of the third carbon-based material is 0.95 g / cm ３ ~1.25g / cm ３ and optionally 1.00 g / cm ３ ~1.25g / cm ３ It is. (7) The gram capacity of the third carbon-based material is between 350 mAh / g and 363 mAh / g, optionally between 352 mAh / g and 362 mAh / g.

20. 20. The secondary battery of claim 1, wherein the first region and / or the second region further comprises a silicon-based material, and, optionally, the first region and the second region both comprise a silicon-based material, and the mass proportion of the silicon-based material in the first region is equal to or less than the mass proportion of the silicon-based material in the second region.

21. The secondary battery according to claim 1 , wherein an intermediate region located between the first region and the second region contains the first active material and / or the second active material.

22. The secondary battery according to claim 1 , wherein the negative electrode film layer satisfies at least one of the following conditions: (1) The porosity of the negative electrode membrane layer is 18.0%-36.7%, and optionally 19.0%-34.0%. (2) The compressed density of the negative electrode film layer is 1.45 g / cm ３ ~1.90g / cm ３ and optionally 1.50 g / cm ３ ~1.85g / cm ３ It is. (3) The surface density of the negative electrode film layer is 5.0 mg / cm ２ ~25.0mg / cm ２ and optionally 5.5 mg / cm ２ ~22.5mg / cm ２ It is. (4) The OI value of the negative electrode film layer is 45.0 or less, and optionally is 8.0 to 45.

0. (5) The thickness of the negative electrode film layer is 60 μm or more, and optionally 70 μm to 250 μm.

23. A power consuming device comprising the secondary battery according to any one of claims 1 to 22.

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