Secondary battery and power consuming device

Abstract

The present application provides a secondary battery and a power consumption device. The secondary battery includes 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 has 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 first active material includes a first carbon-based material and a second carbon-based material, the first carbon-based material has a pore structure, and the second carbon-based material includes artificial graphite. The present application provides a secondary battery having high energy density, and can combine high safety performance with good kinetic performance and cycle performance.

Description

[Technical field]

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

[0002] In recent years, secondary batteries have been widely used in many fields, such as energy storage power systems for 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, it poses serious challenges to the performance of secondary batteries, for example, secondary batteries are required to combine various performances such as energy density, dynamic performance and service life. However, the problem faced in the prior art is that it is often difficult to combine the energy density of secondary batteries with the improvement of the dynamic performance of secondary batteries, and the improvement of the energy density of secondary batteries often affects the dynamic performance and service life of secondary batteries. Summary of the Invention

[0003] The present application has been made in consideration of the above technical problems, and its purpose is to provide a secondary battery and a power consuming device that can provide a secondary battery having a high energy density while also providing high safety performance and good dynamic performance and cycle performance.

[0004] A first aspect of the present application provides 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 having 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 first active material includes a first carbon-based material and a second carbon-based material, the first carbon-based material has a pore structure, and the second carbon-based material includes artificial graphite.

[0005] Through research, the inventors have found that the first region of the negative electrode film layer simultaneously comprises a first carbon-based material and a second carbon-based material, the first carbon-based material having a pore structure, and the second carbon-based material comprising artificial graphite, so that the negative electrode sheet can have high compression density, low volume change and high active ion transmission rate, and thus, under the premise that the secondary battery has high energy density, it is possible to achieve both high safety performance and good kinetic performance and cycle performance.

[0006] In any embodiment of the present application, the second carbon-based material comprises secondary particles of artificial graphite, and optionally the proportion of the secondary particles of artificial graphite in the second carbon-based material is 50% or more. When the second carbon-based material comprises an appropriate proportion of secondary particles of artificial graphite, it can increase the active ion passage in the negative electrode film layer, shorten the active ion insertion path, further improve the dynamic performance of the secondary battery, and also reduce the battery polarization and the occurrence of side reactions, so that the secondary battery has both good cycle performance and dynamic performance.

[0007] In any embodiment of the present application, the layer spacing of the 002 plane of the second carbon-based material is larger than that of the 002 plane of the first carbon-based material. By adjusting the layer spacing of the 002 plane of the second carbon-based material in the first region of the negative electrode film layer to be larger than that of the 002 plane of the first carbon-based material, it is advantageous for the secondary battery to have both high energy density and good dynamic performance.

[0008] In any embodiment of the present application, the graphitization degree of the second carbon-based material is smaller than that of the first carbon-based material. By adjusting the graphitization degree of the second carbon-based material in the first region of the negative electrode film layer to be smaller than that of the first carbon-based material, it is advantageous for the secondary battery to have both high energy density and good dynamic performance.

[0009] In any embodiment of the present application, the capacity per gram of the second carbon-based material is smaller than the capacity per gram of the first carbon-based material. By combining the first carbon-based material having high capacity and the second carbon-based material containing artificial graphite in the first region of the negative electrode film layer, it is advantageous for the secondary battery to have both high energy density and good dynamic performance.

[0010] In any embodiment of the present application, the layer spacing of the 002 plane of the second carbon-based material is 0.33600 nm or less, and optionally 0.33571 nm to 0.33600 nm. When the layer spacing of the second carbon-based material is within the above range, it has high surface stability, so that it can reduce the occurrence of side reactions, and is favorable for the rapid desorption of active ions, and is favorable for the improvement of the active ion transmission performance of the negative electrode film layer. Therefore, the secondary battery can have both high energy density and good cycle performance and kinetic performance.

[0011] In any embodiment of the present application, the capacity per gram of the second carbon-based material is 353mAh / g or more, and optionally 355mAh / g to 365mAh / g. When the capacity per gram 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 transmission performance, which is advantageous for improving the dynamic performance of the secondary battery.

[0012] In any embodiment of the present application, the second carbon-based material has a powder compaction density of 1.75 g / cm under a pressure of 20,000 N. 3 ~2.05g / cm 3 and optionally 1.78g / cm 3 ~2.00g / cm 3 When the powder compression density of the second 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, improve the active ion and electron transmission performance, improve the electrolyte infiltration and retention properties of the negative electrode film layer, and further improve the cycle performance and dynamic performance of the secondary battery.

[0013] In any embodiment of the present application, the second carbon-based material comprises artificial graphite, and the surface of the artificial graphite does not have a carbon coating layer. The artificial graphite has a relatively stable surface, and if the surface does not have a carbon coating layer, it is favorable to maintain its low side reaction activity and to reduce the occurrence of side reactions, and the cycle performance of the secondary battery can be further improved.

[0014] In any embodiment of the present application, the second carbon-based material has a volume distribution particle size Dv10 of 6 μm to 12 μm, optionally 6.5 μm to 11.5 μm.

[0015] In any embodiment of the present application, the second carbon-based material has a volume distribution particle size Dv50 of 12.0 μm to 22.0 μm, optionally 13.5 μm to 20.5 μm.

[0016] When the volume distribution particle size Dv10 and / or Dv50 of the second carbon-based material is within the above range, it is advantageous to improve the transmission performance of active ions and electrons, and the dynamic performance of the secondary battery can be further improved. In addition, the specific surface area of ​​the second carbon-based material can be reduced, the occurrence of side reactions can be reduced, and the cycle performance of the secondary battery can be improved. In addition, a reasonable channel structure can be formed with the first carbon-based material in the negative electrode film layer, and the electrolyte infiltration and retention properties of the negative electrode film layer can be improved.

[0017] In any embodiment of the present application, the particle size distribution of the second carbon-based material (Dv90-Dv10) / Dv50 is less than or equal to 1.65, and optionally between 0.90 and 1.65.

[0018] When the particle size distribution (Dv90-Dv10) / Dv50 of the second carbon-based material is within the above range, it has good particle deposition performance, which is favorable for improving the compression density of the negative electrode film layer and the energy density of the secondary battery, and also forms a reasonable channel structure with the first carbon-based material in the negative electrode film layer, which improves the active ion and electron transmission performance, improves the electrolyte infiltration and retention properties of the negative electrode film layer, and further improves the cycle performance and dynamic performance of the secondary battery.

[0019] In any embodiment of the present application, the tap density of the second carbon-based material is 0.85 g / cm 3 ~1.30g / cm 3 and optionally 0.90 g / cm 3 ~1.30g / cm 3 When the tap density of the second carbonaceous 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 with the first carbonaceous material in the negative electrode film layer, improve the active ion and electron transmission performance, improve the electrolyte infiltration and retention properties of the negative electrode film layer, and further improve the cycle performance and dynamic performance of the secondary battery.

[0020] In any embodiment of the present application, the specific surface area of ​​the second carbon-based material is 1.0 m 2 / g~2.9m 2 / g, optionally 1.2m 2 / g~2.5m 2 When the specific surface area of ​​the second carbon-based material is within the above range, it is advantageous to reduce the occurrence of side reactions and the consumption of active ions due to the formation of the SEI film, and it is advantageous for the secondary battery to have both high initial coulombic efficiency and good cycle performance, and the second carbon-based material has good active ion desorption performance, which can improve the kinetic performance of the secondary battery.

[0021] In any embodiment of the present application, the first carbon-based material has a pore area of ​​0.15 μm 2 and optionally, one or more pore structures having a pore area of ​​0.15 μm 2 ~2.0μm 2 When the first carbon-based material includes a pore structure having the above pore area, the pore structure can secure an expansion space required for the volume change of the particles, which can further reduce the risk of new interfaces occurring due to particle crushing, reduce the occurrence of side reactions, and improve the cycle performance of the secondary battery.

[0022] 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 refers to a region extending from the surface of the particle of the first carbon-based material to the inside of the particle by a distance of 0.25L, L refers to the length of the minor axis of the particle of the first carbon-based material, 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 The first carbon-based material is S 2 >S 1 Further, when the above requirement is satisfied, the initial coulombic efficiency and cycle performance of the secondary battery can be improved.

[0023] In any embodiment of the present application, 1.5≦S2 / S 1 ≦500, and optionally, 2≦S 2 / S 1 ≦450. 2 / S 1 When the content of the electrolyte is within the above range, the secondary battery can be made to have both a high energy density and good cycle performance.

[0024] 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 0.15 μm 2 or less, optionally 0.10 μm 2 By controlling the area of ​​the pore structure in the outer region of the first carbon-based material within the above range, it is possible to provide a dense structure in the outer region of the first carbon-based material, which effectively improves the structural stability of the first carbon-based material, prevents the electrolyte from penetrating into the pore structure inside the particles of the first carbon-based material as much as possible, and effectively improves the cycle performance of the secondary battery.

[0025] In any embodiment of the present application, the internal region of the first carbon-based material may include a region having an area of ​​0.15 μm 2 and optionally one or more pore structures having an area of ​​0.15 μm 2 ~2.0μm 2 The first carbon-based material has one or more pore structures of the above size in the internal region thereof, which can effectively reduce the roll pressing pressure of the negative electrode sheet, effectively reduce damage to the particles, ensure 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, and improve the compression density of the negative electrode film layer and buffer the volume change of the negative electrode film layer.

[0026] In any embodiment of the present application, the specific surface area of ​​the first carbon-based material is 0.7 m 2 / g~1.8m 2 / g, optionally 0.8m 2 / g~1.6m 2The first carbon-based material has a low specific surface area, which reduces the consumption of active ions due to the formation of the SEI film, and can improve the initial coulombic efficiency and cycle 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 20.0 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 35.0 μm, and optionally 17.0 μm to 32.0 μm.

[0029] When the volume distribution particle size Dv50 and / or Dv90 of the first carbon-based material are within the above ranges, it is advantageous to improve the transmission performance of active ions and electrons, and the dynamic performance of the secondary battery can be further improved. In addition, the specific surface area of ​​the first carbon-based material can be reduced, the occurrence of side reactions can be reduced, and the cycle performance of the secondary battery can be improved. In addition, a reasonable channel structure can be formed with the second carbon-based material in the negative electrode film layer, and the electrolyte infiltration and retention properties of the negative electrode film layer can be improved.

[0030] In any embodiment of the present application, the first carbon-based material has a (Dv90-Dv10) / Dv50 of less than or equal to 1.50, and optionally between 0.7 and 1.40.

[0031] When the (Dv90-Dv10) / Dv50 of the first carbon-based material is within the above range, it has good particle deposition performance, which is favorable for improving the compression density of the negative electrode film layer, so that the energy density of the secondary battery can be further improved; and it also forms a reasonable channel structure with the second carbon-based material in the negative electrode film layer, which is favorable for improving the active ion and electron transmission performance, improving the electrolyte infiltration and retention properties of the negative electrode film layer, and improving the cycle performance and dynamic performance of the secondary battery.

[0032] In any embodiment of the present application, the powder compaction density of the first carbon-based material under a pressure of 20,000 N is 1.75 g / cm 3 ~1.95g / cm 3 and optionally 1.80 g / cm 3 ~1.90g / cm 3 It is.

[0033] When the powder compression 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 with the first carbon-based material in the negative electrode film layer, improve the active ion and electron transmission performance, improve the electrolyte infiltration and retention properties of the negative electrode film layer, and further improve the cycle performance and dynamic performance of the secondary battery.

[0034] In any embodiment of the present application, the tap density of the first carbon-based material is 0.80 g / cm 3 ~1.50g / cm 3 and optionally 0.85g / cm 3 ~1.45g / cm 3 It is.

[0035] 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 with the second carbon-based material of the negative electrode film layer to improve the active ion and electron transmission performance, improve the electrolyte infiltration and retention properties of the negative electrode film layer, and further improve the cycle performance and kinetic performance of the secondary battery.

[0036] In any embodiment of the present application, the graphitization degree of the first carbon-based material is 93.5% or more, and optionally 93.8% to 98%.

[0037] When the graphitization degree of the first carbon-based material is within the above range, the capacity per gram thereof is higher, which is advantageous for improving the energy density of the secondary battery.

[0038] In any embodiment of the present application, the powder OI value of the first carbon-based material is 8 to 18, and optionally 8 to 16. When the powder OI value of the first carbon-based material is within the above range, it is advantageous for accepting active ions and is also advantageous for reducing the thickness expansion rate of the negative electrode film layer.

[0039] In any embodiment of the present application, the capacity per gram of the first carbon-based material is 354 mAh / g or more, and optionally 354 mAh / g to 370 mAh / g, thereby improving the energy density of the secondary battery.

[0040] In any embodiment of the present application, the first carbon-based material has two diffraction peaks in a 2θ range of 25.5° to 27.5° in a peak division spectrum of an X-ray diffraction spectrum. When the first carbon-based material has two diffraction peaks in a 2θ range of 25.5° to 27.5° in a peak division spectrum of an X-ray diffraction spectrum, it is advantageous for improving the energy density and dynamic performance of a secondary battery.

[0041] In any embodiment of the present application, of the two diffraction peaks, the one having a smaller 2θ is designated as a first peak, and the other having a larger 2θ is designated as a second peak, and the ratio of the peak intensity of the first peak to the peak intensity of the second peak is 10:90 to 40:60. If the ratio of the peak intensity of the first peak to the peak intensity of the second peak is within the above range, it is advantageous for the secondary battery to better combine high energy density and good dynamic performance.

[0042] In any embodiment of the present application, the mass ratio of the first carbonaceous material in the first active material is 20wt% or more, and optionally 30wt% to 70wt%. When the mass ratio of the first carbonaceous material is within the above range, it is advantageous for the secondary battery to have both high energy density and good dynamic performance.

[0043] In any embodiment of the present application, the second region comprises a second active material, the second active material comprising a third carbon-based material, optionally having a carbon coating layer on the surface of the third carbon-based material, which is advantageous in improving the kinetic performance of the secondary battery.

[0044] In any embodiment of the present application, the third carbon-based material includes graphite having a carbon coating layer on a surface thereof. Optionally, the graphite includes at least one of artificial graphite and natural graphite.

[0045] In any embodiment of the present application, the third carbon-based material comprises artificial graphite having a carbon coating layer on its surface, and the artificial graphite comprises secondary particles, optionally the proportion of the secondary particles in the artificial graphite is 50% or more. When the third carbon-based material comprises a suitable proportion of secondary particles, it can increase the active ion passage in the negative electrode film layer, shorten the active ion insertion path, further improve the dynamic performance of the secondary battery, and also reduce the battery polarization and the occurrence of side reactions, so that the secondary battery has good cycle performance.

[0046] In any embodiment of the present application, the layer spacing of the 002 plane of the second carbon-based material is smaller than that of the 002 plane of the third carbon-based material. Since the layer spacing of the third carbon-based material is large and favorable for rapid desorption of active ions, the layer spacing of the 002 plane of the second carbon-based material is adjusted to be smaller than that of the 002 plane of the third carbon-based material, so that the dynamic performance of the secondary battery can be further improved.

[0047] In any embodiment of the present application, the graphitization degree of the second carbon-based material is greater than that of the third carbon-based material. Since the third carbon-based material has a small graphitization degree and a large interlayer spacing, which is favorable for rapid desorption of active ions, the graphitization degree of the second carbon-based material is adjusted to be greater than that of the third carbon-based material, so that the dynamic performance of the secondary battery can be further improved.

[0048] In any embodiment of the present application, the capacity per gram of the second carbon-based material is greater than the capacity per gram of the third carbon-based material. The third carbon-based material has a small capacity per gram and a large interlayer spacing, which is favorable for the rapid desorption of active ions, and can further improve the dynamic performance of the secondary battery. The second carbon-based material and the first carbon-based material have a high capacity per gram, which is also favorable for the secondary battery to have both high energy density and good dynamic performance.

[0049] In any embodiment of the present application, the powder compressed density of the second carbon-based material under a pressure of 20,000 N is greater than the powder compressed density of the third carbon-based material under a pressure of 20,000 N. By adjusting the powder compressed density of the second carbon-based material to be greater than the powder compressed density of the third carbon-based material, it is advantageous to have a reasonable pore distribution in the thickness direction of the negative electrode membrane layer, improve the transmission performance of active ions and electrons, improve the electrolyte infiltration and retention properties of the negative electrode membrane layer, reduce the volume change of the negative electrode membrane layer, and further improve the cycle performance, safety performance and dynamic performance of the secondary battery.

[0050] In any embodiment of the present application, the powder compressed density of the first carbon-based material under a pressure of 20,000 N is greater than the powder compressed density of the third carbon-based material under a pressure of 20,000 N. By adjusting the powder compressed density of the first carbon-based material to be greater than the powder compressed density of the third carbon-based material, it is advantageous to have a reasonable pore distribution in the thickness direction of the negative electrode membrane layer, improve the transmission performance of active ions and electrons, improve the electrolyte infiltration and retention properties of the negative electrode membrane layer, reduce the volume change of the negative electrode membrane layer, and further improve the cycle performance, safety performance and dynamic performance of the secondary battery.

[0051] In any embodiment of the present application, the volume distribution particle diameter Dv50 of the second carbonaceous material is larger than that of the third carbonaceous material. By adjusting the volume distribution particle diameter Dv50 of the second carbonaceous material to be larger than that of the third carbonaceous material, it is advantageous to have a reasonable pore distribution in the thickness direction of the negative electrode membrane layer, improve the transmission performance of active ions and electrons, improve the electrolyte infiltration and retention properties of the negative electrode membrane layer, reduce the volume change of the negative electrode membrane layer, and further improve the cycle performance, safety performance and dynamic performance of the secondary battery.

[0052] In any embodiment of the present application, the volume distribution particle diameter Dv50 of the first carbonaceous material is larger than that of the third carbonaceous material. By adjusting the volume distribution particle diameter Dv50 of the first carbonaceous material to be larger than that of the third carbonaceous material, it is advantageous to have a reasonable pore distribution in the thickness direction of the negative electrode membrane layer, improve the transmission performance of active ions and electrons, improve the electrolyte infiltration and retention properties of the negative electrode membrane layer, reduce the volume change of the negative electrode membrane layer, and further improve the cycle performance, safety performance and dynamic performance of the secondary battery.

[0053] In any embodiment of the present application, the volume distribution particle diameter Dv50 of the third carbon-based material is 10.0 μm to 22.0 μm, and optionally 11.5 μm to 20.0 μm. When the volume distribution particle diameter Dv50 of the third carbon-based material is within the above range, it is favorable for improving the transmission performance of active ions and electrons, and can further improve the dynamic performance of the secondary battery, and can also reduce the specific surface area of ​​the third carbon-based material, reduce the occurrence of side reactions, and improve the cycle performance of the secondary battery.

[0054] In any embodiment of the present application, the third carbon-based material has a (Dv90-Dv10) / Dv50 of less than 1.65, and optionally 0.90-1.65. When the third carbon-based material has a (Dv90-Dv10) / Dv50 within the above range, its particle deposition performance is good, which is favorable for improving the compression density of the negative electrode film layer, so that the energy density of the secondary battery can be further improved; and the negative electrode film layer has a suitable pore distribution, which is favorable for improving the electrolyte infiltration and retention properties of the negative electrode film layer, and improving the cycle performance and dynamic performance of the secondary battery.

[0055] In any embodiment of the present application, the third carbon-based material has a powder OI value of 2.0 to 6.5, and optionally 2.0 to 6.0. The third carbon-based material has a small powder OI value and has active ion insertion ports in all directions of the particles, so that the active ions can be rapidly received from the positive electrode, and the dynamic performance of the secondary battery can be further improved.

[0056] In any embodiment of the present application, the third carbon-based material has a powder compaction density of 1.65 g / cm under a pressure of 20,000 N. 3 ~2.00g / cm 3 and optionally 1.68g / cm 3 ~1.98g / cm 3 When the powder compressed density of the third carbon-based material is within the above range, it can improve the compressed density of the negative electrode film layer, improve the energy density of the secondary battery, and has a suitable pore distribution, which is favorable for improving the active ion and electron transmission performance, improving the electrolyte infiltration and retention properties of the negative electrode film layer, and further improving the cycle performance and dynamic performance of the secondary battery.

[0057] In any embodiment of the present application, the third carbon-based material has a tap density of 0.85 g / cm 3 ~1.25g / cm 3 and optionally 0.90 g / cm 3 ~1.25g / cm 3When 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 the negative electrode film layer has a suitable pore distribution, which is favorable for improving the active ion and electron transmission performance, improving the electrolyte infiltration and retention properties of the negative electrode film layer, and further improving the cycle performance and dynamic performance of the secondary battery.

[0058] In any embodiment of the present application, the graphitization degree of the third carbon-based material is 96% or less, and optionally 90.5% 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 transmission performance of the negative electrode film layer, and is favorable for the secondary battery to have both high energy density and good dynamic performance.

[0059] In any embodiment of the present application, the specific surface area of ​​the third carbon-based material is 0.9 m 2 / g~2.5m 2 / g, optionally 0.95m 2 / g~2.45m 2 When the specific surface area of ​​the third carbon-based material is within the above range, it is favorable for the rapid desorption of active ions, and can improve the dynamic performance of the secondary battery, reduce the consumption of active ions due to the formation of the SEI film, and improve the initial Coulombic efficiency of the secondary battery.

[0060] In any embodiment of the present application, the capacity per gram of the third carbon-based material is 340mAh / g to 360mAh / g, and optionally 345mAh / g to 360mAh / g. The capacity per gram of the third carbon-based material being within the above range allows the third carbon-based material to have good active ion transmission performance, which improves the dynamic performance of the secondary battery, and is also advantageous for the secondary battery to have high energy density.

[0061] In any embodiment of the present application, the first region and / or the second region further comprises a silicon-based material, which serves to improve the pore structure in the negative electrode membrane layer, facilitates the infiltration and retention of the electrolyte, improves the dynamic performance of the secondary battery, and improves the negative electrode capacity, thereby further improving the energy density of the secondary battery.

[0062] In any embodiment of the present application, the first region and the second region further include 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 electrolyte permeability of the negative electrode film layer, improving the transmission performance of active ions, and improving the cycle performance and / or kinetic performance of the secondary battery.

[0063] 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.

[0064] A second aspect of the present application provides a power consuming device including the secondary battery of the first aspect of the present application.

[0065] The power consuming 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]

[0066] In order to more clearly describe the technical solutions of the embodiments of the present application, the following briefly introduces the drawings necessary for the embodiments of the present application. It is clear that the drawings described below are only some embodiments of the present application. Those skilled in the art can further obtain other drawings based on the drawings even without creative labor.

[0067] [Figure 1] FIG. 1 is a schematic diagram of an 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 a particle of the first carbon-based material of the present application. [Diagram 5] 1 is a schematic diagram of an embodiment of a secondary battery of the present application. [Figure 6] FIG. 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 an embodiment of a battery module of the present application. [Figure 8] FIG. 1 is a schematic diagram of an embodiment of a battery pack of the present application. [Figure 9] 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 an embodiment of a power consuming device including a secondary battery of the present application as a power source.

[0068] In the drawings, which are not necessarily drawn to scale, the symbols are as follows: 1 battery pack, 2 upper housing, 3 lower housing, 4 battery module, 5 secondary battery, 51 case, 52 electrode assembly, 53 cover plate, 10 negative electrode sheet, 101 negative electrode current collector, 102 negative electrode film layer, 102a first surface, 102b second surface, 1021 first region, 1022 second region, 1023 middle region, 200 first carbon-based material, 201 outer region, 202 inner region. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0069] Hereinafter, the embodiments specifically disclosing the secondary battery and power consumption device of the present application will be described in detail with reference to the drawings as appropriate. However, unnecessary detailed description may be omitted. For example, detailed description of already well-known matters and duplicate description of substantially the same configuration may be omitted. This is to avoid the following description becoming unnecessarily redundant and to facilitate understanding by those skilled in the art. Note that the attached 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.

[0070] The "ranges" disclosed herein are defined in the form of lower and upper limits, where a given range is defined by selecting one lower limit and one upper limit, and the selected lower and upper limits specifically define the boundaries of the range. Ranges defined in this manner may or may not include the endpoints and may be arbitrarily combined, i.e., any lower limit may be combined with any upper limit to form a range. For example, when the ranges 60-120 and 80-110 are recited for a particular parameter, it is understood that the ranges 60-110 and 80-120 are also contemplated. Also, when the minimum range values ​​1 and 2 and the maximum range values ​​3, 4 and 5 are recited, the ranges 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5 are all contemplated. In this application, unless otherwise stated, the numerical range "a-b" is a shorthand notation for any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is an abbreviation for combinations of these numerical values. Furthermore, a notation that a parameter is an integer greater than or equal to 2 (≧2) is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0071] Unless otherwise specified, all the embodiments and optional embodiments of the present application may be combined with each other to form a new technical solution, and such technical solution is considered to be included in the disclosure content of the present application.

[0072] Unless otherwise stated, all technical features and optional technical features in the present application may be combined with each other to form new technical solutions, and such technical solutions are deemed to be included in the disclosure content of the present application.

[0073] Unless otherwise stated, all steps in this application may be performed in sequence or randomly, but are preferably performed in sequence. For example, the method includes steps (a) and (b) and may include steps (a) and (b) performed in sequence, or may include steps (b) and (a) performed in sequence. For example, when it is stated that the method may further include 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), may include steps (a), (c) and (b), may include steps (c), (a) and (b), etc.

[0074] Unless otherwise specified, the terms "comprise" and "include" used herein mean open-ended and may also be closed-ended. For example, the terms "comprise" and "include" may refer to further "comprising" or "including" other components not listed, or to "comprising" or "including" only the listed components.

[0075] Unless otherwise stated, in this application, 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 are met: 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 both A and B are true (or exist).

[0076] Unless otherwise explained, terms used in this application have the well-known meanings commonly understood by those of ordinary skill in the art.

[0077] 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.

[0078] Unless otherwise specified, in this application, the term "active ions" refers to ions that can be inserted and removed back and forth between the positive and negative electrodes of a secondary battery, including, but not limited to, lithium ions.

[0079] As used herein, the terms "plurality" and "multiple types" refer to two or more than two types.

[0080] The inventors have found that in order to improve the cycle performance of a secondary battery, it is important to balance the energy density and charging ability of the battery. At present, the kinetic performance of the negative electrode is often improved by reducing the coating weight of the negative electrode film layer or reducing the compression density of the negative electrode film layer. However, a large amount of research has proven that the above-mentioned methods for improving the kinetics of the negative electrode can only improve the kinetic performance of the battery at the beginning of charging to a certain extent, and have no significant effect on improving the kinetic performance of the battery at the end of charging, and cannot effectively improve the kinetic performance of the secondary battery, and therefore cannot actually perform high-rate charging on the secondary battery. In addition, the energy density of the secondary battery is also significantly reduced.

[0081] For example, when the energy density of a secondary battery is improved by increasing the compression density of the negative electrode film layer, this often leads to deterioration of the dynamic performance and cycle performance of the secondary battery, and also increases the volume change of the negative electrode film layer, thereby increasing the risk of electrolyte bridge breakage, which affects the safety performance of the secondary battery.

[0082] For this reason, it is currently difficult for a secondary battery to have high energy density, high safety performance, and good cycle performance and dynamic performance.

[0083] The inventors conducted further research and ingeniously improved the composition of the negative electrode film layer, thus overcoming the above bottleneck.

[0084] Specifically, a first aspect of an embodiment of the present application provides a secondary battery.

[0085] In the present application, the type of the secondary battery is not particularly limited, 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. In the charging and discharging process of the secondary battery, active ions can be 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. In the present application, the type of the electrolyte is not particularly limited, and 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). In the secondary battery using the electrolyte solution and the secondary battery using the solid electrolyte, a separator may be provided between the positive electrode sheet and the negative electrode sheet and serve to separate them.

[0086] [Negative electrode sheet]

[0087] 1 to 3 are schematic diagrams of an embodiment of the negative electrode sheet of the present application. As shown in FIGS. 1 to 3, the 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 the first surface 102a. The thickness of the negative electrode film layer 102 is H, a region within a range from the second surface 102b of the negative electrode film layer to a thickness of 0.3H is a first region 1021 of the negative electrode film layer, and a region within a range from the first surface 102a of the negative electrode film layer to a thickness of 0.3H is a second region 1022 of the negative electrode film layer. The first region 1021 includes a first active material including a first carbon-based material and a second carbon-based material, the first carbon-based material has a pore structure, and the second carbon-based material includes artificial graphite. The thickness H of the negative electrode film layer is the thickness of the negative electrode film layer located on one side of the negative electrode current collector.

[0088] In the present application, "the first carbon-based material has a pore structure" means that the first carbon-based material has a pore structure that can be directly observed from a cross-sectional image (e.g., a scanning electron microscope image with a magnification of 1000 times), i.e., the pore structure in the raw material for producing the first carbon-based material is not completely filled.

[0089] Through research, the inventors have found that the first region of the negative electrode film layer simultaneously comprises a first carbon-based material and a second carbon-based material, the first carbon-based material having a pore structure, and the second carbon-based material comprising artificial graphite, so that the negative electrode sheet can have high compression density, low volume change and high active ion transmission rate, and thus, under the premise that the secondary battery has high energy density, it can have high safety performance and good kinetic performance and cycle performance.

[0090] Through intensive research, the inventors have found that the first carbon-based material has a pore structure and is easily deformed during cold pressing. When it is located in the first region of the negative electrode membrane layer, it can effectively reduce the roll pressing pressure of the negative electrode sheet, and can effectively reduce damage to the particles and reduce the occurrence of side reactions. The pore structure of the first carbon-based material can also ensure the expansion space required for the volume change of the particles, which can reduce the risk of new interfaces being generated due to particle crushing, and can further reduce the occurrence of side reactions. In addition, when the first carbon-based material is located in the first region of the negative electrode membrane layer, it can reduce the adverse effects on the dynamic performance of the secondary battery, and can fully exert the advantages of its high capacity and high compression density, thereby improving the energy density of the secondary battery.

[0091] The second carbon-based material includes artificial graphite and has good kinetic performance, which can improve the speed at which active ions are inserted into the first region of the negative electrode membrane layer, improve the active ion transmission performance of the negative electrode membrane layer, and is advantageous for improving the kinetic performance of the secondary battery; at the same time, the second carbon-based material may further form a good channel structure with the first carbon-based material having a pore structure, which can improve the electrolyte infiltration and retention properties of the negative electrode membrane layer and reduce the volume change of the negative electrode membrane layer.

[0092] Therefore, the negative electrode sheet according to the present application has a good channel structure, as well as a high compression density, a low volume change, and a high active ion transmission rate, and can provide a secondary battery with high energy density, while also providing high safety performance and good dynamic performance and cycle performance.

[0093] In some embodiments, the second carbon-based material includes secondary particles of artificial graphite. Optionally, the number ratio of the secondary particles of artificial graphite in the second carbon-based material is 50% or more, for example, 60% to 95%, 60% to 100%, 65% to 85%, 70% to 100%, 75% to 90%, 75% to 85%, 80% to 100%, 80% to 90%, 85% to 95%, or 90% to 100%. When the second carbon-based material includes an appropriate ratio of secondary particles of artificial graphite, it can increase the active ion passage in the negative electrode film layer, shorten the active ion insertion path, further improve the dynamic performance of the secondary battery, and also reduce the battery polarization and the occurrence of side reactions, so that the secondary battery has both good cycle performance and dynamic performance.

[0094] In this application, the proportion of the number of secondary particles of artificial graphite in the second carbon-based material refers to the following steps: randomly taking one test sample in the negative electrode film layer, randomly taking multiple test regions in the test sample, obtaining images of the multiple test regions using a scanning electron microscope, and statistically calculating the proportion of the number of secondary particles of artificial graphite in a first region of the negative electrode film layer in each image to the total number of particles of the second carbon-based material; and the average of the multiple statistical results is the proportion of the number of secondary particles of artificial graphite in the second carbon-based material.

[0095] In some embodiments, the layer spacing of the 002 plane of the second carbon-based material is larger than that of the 002 plane of the first carbon-based material. The larger layer spacing of the second carbon-based material is favorable for rapid desorption of active ions, and the smaller layer spacing of the first carbon-based material is favorable for high capacity per gram. Therefore, by adjusting the layer spacing of the 002 plane of the second carbon-based material in the first region of the negative electrode film layer to be larger than that of the 002 plane of the first carbon-based material, it is favorable for the secondary battery to have both high energy density and good dynamic performance.

[0096] In some embodiments, the graphitization degree of the second carbon-based material is smaller than that of the first carbon-based material. The second carbon-based material has a smaller graphitization degree and a larger interlayer spacing, which is advantageous for rapid desorption of active ions, and the first carbon-based material has a higher graphitization degree and a higher capacity per gram. Therefore, by adjusting the graphitization degree of the second carbon-based material in the first region of the negative electrode film layer to be smaller than that of the first carbon-based material, it is advantageous to provide the secondary battery with both high energy density and good dynamic performance.

[0097] In some embodiments, the capacity per gram of the second carbon-based material is smaller than the capacity per gram of the first carbon-based material. The combination of the first carbon-based material having high capacity and the second carbon-based material including artificial graphite in the first region of the negative electrode film layer is advantageous for providing the secondary battery with both high energy density and good dynamic performance.

[0098] In some embodiments, the layer spacing of the 002 plane of the second carbon-based material is 0.33600 nm or less, and optionally 0.33571 nm to 0.33600 nm. When the layer spacing of the second carbon-based material is within the above range, it has high surface stability, which can reduce the occurrence of side reactions and is favorable for the rapid desorption of active ions, and is favorable for the improvement of the active ion transmission performance of the negative electrode film layer. Therefore, the secondary battery can have both high energy density and good cycle performance and kinetic performance.

[0099] In some embodiments, the capacity per gram of the second carbon-based material is 353 mAh / g or more, optionally 355 mAh / g to 365 mAh / g. When the capacity per gram 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 transmission performance, which is advantageous for improving the dynamic performance of the secondary battery.

[0100] In some embodiments, the second carbon-based material has a powder compaction density of 1.75 g / cm under a pressure of 20,000 N. 3 ~2.05g / cm 3 and optionally 1.75 g / cm 3 ~2.00g / cm 3 , 1.78g / cm 3 ~2.00g / cm 3 When the powder compression density of the second 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, improve the active ion and electron transmission performance, improve the electrolyte infiltration and retention properties of the negative electrode film layer, and further improve the cycle performance and dynamic performance of the secondary battery.

[0101] In some embodiments, the second carbon-based material comprises artificial graphite, and the surface of the artificial graphite does not have a carbon coating layer. The artificial graphite has a relatively stable surface, and if the surface does not have a carbon coating layer, it is favorable to maintain its low side reaction activity and to reduce the occurrence of side reactions, which can further improve the cycle performance of the secondary battery.

[0102] In further research, the inventors have found that the second carbon-based material can further improve the performance of the secondary battery, for example, at least one of the energy density, safety performance, kinetic performance, and cycle performance of the secondary battery, by further satisfying one or more of the following conditions in addition to satisfying the above design:

[0103] In some embodiments, the second carbon-based material has a volume distribution particle size Dv10 between 6 μm and 12 μm, optionally between 6.5 μm and 11.5 μm.

[0104] In some embodiments, the second carbon-based material has a volume distribution particle size Dv50 between 12.0 μm and 22.0 μm, optionally between 13.5 μm and 20.5 μm.

[0105] When the volume distribution particle size Dv10 and / or Dv50 of the second carbon-based material is within the above range, it is favorable for improving the transmission performance of active ions and electrons, and can further improve the kinetic performance of the secondary battery, reduce the specific surface area of ​​the second carbon-based material, reduce the occurrence of side reactions, and improve the cycle performance of the secondary battery. It can also form a reasonable channel structure with the first carbon-based material in the negative electrode film layer, improve the electrolyte infiltration and retention properties of the negative electrode film layer, reduce the volume change of the negative electrode film layer, and improve the cycle performance and safety performance of the secondary battery.

[0106] In some embodiments, 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 film layer and the energy density of the secondary battery, and is also favorable for forming a reasonable channel structure with the first carbon-based material in the negative electrode film layer, improving the active ion and electron transmission performance, improving the electrolyte infiltration and retention properties of the negative electrode film layer, reducing the volume change of the negative electrode film layer, and further improving the cycle performance, safety performance and / or dynamic performance of the secondary battery.

[0107] In some embodiments, the second carbon-based material has a tap density of 0.85 g / cm 3 ~1.30g / cm 3 and optionally 0.90 g / cm 3 ~1.30g / cm 3 When the tap density of the second 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 with the first carbon-based material in the negative electrode film layer, improve the active ion and electron transmission performance, improve the electrolyte infiltration and retention properties of the negative electrode film layer, reduce the volume change of the negative electrode film layer, and further improve the cycle performance, safety performance and / or dynamic performance of the secondary battery.

[0108] In some embodiments, the second carbon-based material has a specific surface area of ​​1.0 m 2 / g~2.9m 2 / g, optionally 1.2m 2 / g~2.5m 2When the specific surface area of ​​the second carbon-based material is within the above range, it is advantageous to reduce the occurrence of side reactions and the consumption of active ions due to the formation of the SEI film, and it is advantageous to provide the secondary battery with both high initial coulombic efficiency and good cycle performance, and the second carbon-based material has good active ion desorption performance, which can improve the kinetic performance of the secondary battery.

[0109] In some embodiments, the first carbon-based material has a pore area of ​​0.15 μm 2 and optionally one or more pore structures having a pore area of ​​0.15 μm or greater. 2 ~2.0μm 2 When the first carbon-based material includes a pore structure having the above pore area, the pore structure can secure an expansion space required for the volume change of the particles, which can further reduce the risk of new interfaces occurring due to particle crushing, reduce the occurrence of side reactions, and improve the cycle performance of the secondary battery.

[0110] 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 particle surface of the first carbon-based material to an inner portion 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 It is.

[0111] The first carbon-based material is S 2 >S 1If the above conditions are satisfied, the first carbon-based material further has the characteristics that the number of holes in the inner region is large and / or the size of the holes is large, but the number of holes in the outer region is small and / or the size of the holes is small. The pore structure of the inner region of the first carbon-based material can effectively reduce the roll pressure 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 effectively reducing the occurrence of side reactions. Since the number of holes in the outer region of the first carbon-based material is small and / or the size of the holes is small, the first carbon-based material particles have a stable structure, and the electrolyte can be prevented from penetrating 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 stable structure of the first carbon-based material particles by using the first carbon-based material particles having a small number of holes and / or a small size of the holes. 2 >S 1 Further, when the above requirement is satisfied, the initial coulombic efficiency and cycle performance of the secondary battery can be improved.

[0112] 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 In further studies, the inventors found that S 2 / S 1 It has been found that when the content of the carbon black is within the above range, the secondary battery can have both a high energy density and good cycle performance in a better manner.

[0113] In the present application, the total pore area S of the outer region of the first carbon-based material 1 and the total hole area S of the inner region 2 can be obtained by examining a cross-sectional image of the first carbon-based material.

[0114] In this application, a cross-sectional image of a first carbon-based material includes a cross-sectional image through the center of a particle of the first carbon-based material. "Particle center" refers to a range within a radius extending from the geometric center of the particle toward the particle surface at 0.1 μm.

[0115] 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 particle surface passes through the geometric center of the particle.

[0116] 4 is a schematic diagram of a cross-sectional image of a particle of the first carbon-based material 200 of the present application, and 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 length of the short axis of the particle of the first carbon-based material 200, 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.

[0117] 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), then refer to JY / T010-1996 and scan the cross section of the first carbon-based material by using a scanning electron microscope (e.g., Sigma 300 type scanning electron microscope from ZEISS Co., Ltd., Germany), and finally, the total pore area S of the outer region of the first carbon-based material can be calculated by using image processing software (e.g., AVIZO). 1 and the total hole area S of the inner region 2 Calculate.

[0118] In some embodiments, the length L of the minor axis of the first carbon-based material particles satisfies L≧5.5 μm, and optionally 6 μm≦L≦20 μm, 8 μm≦L≦20 μm, 8 μm≦L≦18 μm, or 8 μm≦L≦16 μm.

[0119] In some embodiments, the area of ​​the pore structure in the outer region of the first carbon-based material is less than 0.15 μm 2 or less, optionally 0.10 μm 2 The inventors, in further research, found that 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 have a dense structure, thereby effectively improving the structural stability of the first carbon-based material, preventing the electrolyte from penetrating into the pore structure inside the first carbon-based material particles as much as possible, and effectively improving the cycle performance of the secondary battery. Of course, the present application does not require that the areas of all the pore structures in the outer region of the first carbon-based material be less than 0.15 μm 2 For example, 95% or more, optionally 99% or more of the pore structure has an area of ​​0.15 μm 2 The following is controlled:

[0120] In some embodiments, the interior region of the first carbon-based material has an area of ​​0.15 μm 2 and optionally, one or more pore structures having an area of ​​0.15 μm 2 ~2.0μm 2 In further research, the inventors found that by making the internal region of the first carbon-based material include a pore structure of the above size, the roll pressing pressure of the negative electrode sheet can be effectively reduced, particle damage can be effectively reduced, and sufficient and stable expansion space can be ensured for the volume change of the first carbon-based material particles, the risk of crushing the first carbon-based material particles can be reduced, while the compression density of the negative electrode film layer can be improved and the volume change of the negative electrode film layer can be buffered.

[0121] In further research, the inventors have found that the performance of the secondary battery, for example at least one of the energy density, kinetic performance, and cycle performance of the secondary battery, can be further improved by making the first carbon-based material further satisfy one or more of the following conditions in addition to satisfying the above design.

[0122] In some embodiments, the first carbon-based material has a specific surface area of ​​0.7 m 2 / g~1.8m 2 / g, optionally 0.8m 2 / g~1.6m 2 The first carbon-based material has a low specific surface area, which reduces the consumption of active ions due to the formation of the SEI film, and can improve the initial coulombic efficiency and cycle performance of the secondary battery.

[0123] 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 20.0 μm.

[0124] In some embodiments, the first carbon-based material has a volume distribution particle size Dv90 of 16.0 μm to 35.0 μm, optionally 17.0 μm to 32.0 μm.

[0125] 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 transmission performance of active ions and electrons, so that the kinetic performance of the secondary battery can be further improved, the specific surface area of ​​the first carbon-based material can be reduced, the occurrence of side reactions can be reduced, and the cycle performance of the secondary battery can be improved. In addition, a reasonable channel structure can be formed with the second carbon-based material in the negative electrode film layer, and the electrolyte infiltration and retention properties of the negative electrode film layer can be improved.

[0126] In some embodiments, the (Dv90-Dv10) / Dv50 of the first carbon-based material is less than 1.50, and optionally 0.7-1.40. When the (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 film layer, so that the energy density of the secondary battery can be further improved, and the first carbon-based material forms a reasonable channel structure with the second carbon-based material in the negative electrode film layer, which improves the active ion and electron transmission performance, which improves the electrolyte infiltration and retention properties of the negative electrode film layer, and which is favorable for improving the cycle performance and dynamic performance of the secondary battery.

[0127] In some embodiments, the first carbon-based material has a powder compaction density of 1.75 g / cm under a pressure of 20,000 N. 3 ~1.95g / cm 3 and optionally 1.80 g / cm 3 ~1.90g / cm 3 When the powder compression density of the first carbonaceous 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 also form a reasonable channel structure with the first carbonaceous material in the negative electrode film layer, improve the active ion and electron transmission performance, improve the electrolyte infiltration and retention properties of the negative electrode film layer, and further improve the cycle performance and dynamic performance of the secondary battery.

[0128] In some embodiments, the first carbon-based material has a tap density of 0.80 g / cm 3 ~1.50g / cm 3 and optionally 0.85g / cm 3 ~1.45g / cm 3 When the tap density of the first carbonaceous 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 also form a reasonable channel structure with the second carbonaceous material of the negative electrode film layer, improve the active ion and electron transmission performance, improve the electrolyte infiltration and retention properties of the negative electrode film layer, and further improve the cycle performance and dynamic performance of the secondary battery.

[0129] In some embodiments, the graphitization degree of the first carbon-based material is 93.5% or more, and optionally 93.8% to 98%, 94.5% to 98%, or 95.0% to 98%. When the graphitization degree of the first carbon-based material is within the above range, its capacity per gram is higher, which is advantageous for improving the energy density of the secondary battery.

[0130] In some embodiments, the powder OI value of the first carbon-based material is 8 to 18, optionally 8 to 16. When the powder OI value of the first carbon-based material is within the above range, it is favorable for accepting active ions and is also favorable for reducing the thickness expansion rate of the negative electrode film layer.

[0131] In some embodiments, the capacity per gram of the first carbon-based material is 354 mAh / g or more, optionally 354 mAh / g to 370 mAh / g. When the capacity per gram of the first carbon-based material is within the above range, the energy density of the secondary battery can be improved.

[0132] In some embodiments, the first carbon-based material has two diffraction peaks in the range of 2θ from 25.5° to 27.5° in the peak split spectrum of the X-ray diffraction spectrum. When the first carbon-based material has two diffraction peaks in the range of 2θ from 25.5° to 27.5° in the peak split spectrum of the X-ray diffraction spectrum, the first carbon-based material can simultaneously contain a crystalline carbon component with a high degree of graphitization (e.g., crystalline carbon with a degree of graphitization of 95.0% or more) and a crystalline carbon component with a low degree of graphitization (e.g., crystalline carbon with a degree of graphitization of 70% to 90%). The crystalline carbon component with a low degree of graphitization can have a large layer spacing, which is advantageous for the diffusion of active ions, thereby improving the dynamic performance of the secondary battery, and the crystalline carbon component with a high degree of graphitization allows the first carbon-based material to have a high capacity per gram and / or compressed density, thereby improving the energy density of the secondary battery. Therefore, when the first carbon-based material has two diffraction peaks in the 2θ range of 25.5° to 27.5° in the peak division spectrum of the X-ray diffraction spectrum, it is advantageous for improving the energy density and dynamic performance of the secondary battery.

[0133] In some embodiments, the two diffraction peaks with a smaller 2θ are referred to as a first peak, and the peak with a larger 2θ are referred to as a second peak, and the ratio of the peak intensity of the first peak to the peak intensity of the second peak is 10:90 to 40:60, optionally 15:85 to 35:65, 15:85 to 30:70. In further studies, the inventors have found that when the ratio of the peak intensity of the first peak to the peak intensity of the second peak is within the above range, it is advantageous for the secondary battery to better combine high energy density and good kinetic performance.

[0134] The peak division spectrum of the X-ray diffraction spectrum of the first carbon-based material was obtained by precisely correcting the X-ray diffraction spectrum of the first carbon-based material using the Rietveld full spectrum fitting precise correction method using Topas software, and 2θ of 25.5° to 27.5° corresponds to the peak top position of the carbon 002 plane. The X-ray diffraction spectrum of the first carbon-based material can be tested using an X-ray diffractometer, and the test can refer to JIS K 0131-1996 and JB / T 4220-2011. The test equipment can be a Bruker D8 Discover X-ray diffractometer. In the X-ray diffraction analysis test, the test conditions are as follows: the first carbon-based material is prepared by a flat sample preparation method, a copper target is used as the anode target, CuKα radiation is used as the radiation source, the voltage is 40KV, the current is 40mA, the anti-scattering slit is 1mm, the scanning 2θ angle range is 20°-80°, the step length is 0.01671°, the time length of each step is 0.24s, and the scanning speed is 4° / min. In the peak division spectrum of the X-ray diffraction spectrum of the first carbon-based material of the present application, the 2θ of the first peak is located between 26.256°-26.456°, and the 2θ of the second peak is located between 26.509°-26.569°.

[0135] In this application, the ratio of the peak intensity of a first peak to the peak intensity of a second peak is the ratio of the integrated area of ​​the first peak to the integrated area of ​​the second peak.

[0136] In some embodiments, the mass ratio of the first carbonaceous material in the first active material is 20 wt% or more, optionally 30 wt% to 70 wt%. When the mass ratio of the first carbonaceous material is within the above range, it is advantageous for the secondary battery to have both high energy density and good dynamic performance.

[0137] The second region 1022 includes a second active material that includes a third carbon-based material.

[0138] In some embodiments, the third carbon-based material has a carbon coating layer on its surface. In some embodiments, 80% or more of the surface of the third carbon-based material is coated with the carbon coating layer, and optionally, 90% to 100% of the surface of the third carbon-based material is coated with the carbon coating layer. When the third carbon-based material is located in the second region of the negative electrode film layer and has a carbon coating layer on its surface, it is advantageous to improve the speed at which active ions are inserted into the negative electrode film layer and improve the kinetic performance of the secondary battery.

[0139] In some embodiments, the carbon in the coating layer includes 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 any 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.

[0140] In some embodiments, the third carbon-based material includes graphite having a carbon coating layer thereon. Optionally, the graphite includes at least one of artificial graphite and natural graphite.

[0141] In some embodiments, the third carbon-based material includes artificial graphite having a carbon coating layer on its surface, and the artificial graphite includes secondary particles. Optionally, the proportion of the quantity of the secondary particles in the artificial graphite is 50% or more, for example, 50% to 100%, 60% to 95%, 60% to 100%, 65% to 85%, 70% to 100%, 75% to 90%, 75% to 85%, 80% to 100%, 80% to 90%, 85% to 95%, or 90% to 100%. When the third carbon-based material includes an appropriate proportion of secondary particles, it can increase the active ion passage in the negative electrode film layer and shorten the active ion insertion path, thereby further improving the dynamic performance of the secondary battery, and also reducing the battery polarization and the occurrence of side reactions, and making the secondary battery have good cycle performance.

[0142] In this application, the proportion of the number of secondary particles in artificial graphite refers to the following procedure: one test sample is randomly taken from the negative electrode film layer, multiple test regions are randomly taken from the test sample, images of the multiple test regions are obtained using a scanning electron microscope, the proportion of the number of secondary artificial graphite particles in the second region of the negative electrode film layer in each image to the total number of artificial graphite particles in the second region is calculated, and the average of the multiple statistical results represents the proportion of the number of secondary particles in the artificial graphite.

[0143] In some embodiments, the layer spacing of the 002 plane of the second carbon-based material is smaller than that of the 002 plane of the third carbon-based material. Since the layer spacing of the third carbon-based material is large and favorable for rapid desorption of active ions, the layer spacing of the 002 plane of the second carbon-based material is adjusted to be smaller than that of the 002 plane of the third carbon-based material, so that the dynamic performance of the secondary battery can be further improved.

[0144] In some embodiments, the graphitization degree of the second carbon-based material is greater than that of the third carbon-based material, and since the third carbon-based material has a smaller graphitization degree and a larger interlayer spacing, which is favorable for the rapid desorption of active ions, the graphitization degree of the second carbon-based material is adjusted to be greater than that of the third carbon-based material, thereby further improving the dynamic performance of the secondary battery.

[0145] In some embodiments, the capacity per gram of the second carbon-based material is greater than the capacity per gram of the third carbon-based material. The capacity per gram of the third carbon-based material is small, the interlayer spacing is large, and it is favorable for the rapid desorption of active ions, so that the dynamic performance of the secondary battery can be further improved, and the capacity per gram of the second carbon-based material and the capacity per gram of the first carbon-based material are high, so that the secondary battery has both high energy density and good dynamic performance.

[0146] In some embodiments, the second carbon-based material has a powder compaction density greater than that of the third carbon-based material at a pressure of 20,000 N. Adjusting the powder compaction density of the second carbon-based material to be greater than that of the third carbon-based material is advantageous to have a reasonable pore distribution in the thickness direction of the negative electrode membrane layer, which can improve the transmission performance of active ions and electrons, improve the electrolyte infiltration and retention properties of the negative electrode membrane layer, reduce the volume change of the negative electrode membrane layer, and further improve the cycle performance, safety performance and dynamic performance of the secondary battery.

[0147] In some embodiments, the first carbon-based material has a powder compaction density greater than that of the third carbon-based material under a pressure of 20,000 N. Adjusting the powder compaction density of the first carbon-based material to be greater than that of the third carbon-based material is advantageous to have a reasonable pore distribution in the thickness direction of the negative electrode membrane layer, which can improve the transmission performance of active ions and electrons, improve the electrolyte infiltration and retention properties of the negative electrode membrane layer, reduce the volume change of the negative electrode membrane layer, and further improve the cycle performance, safety performance and dynamic performance of the secondary battery.

[0148] In some embodiments, the volume distribution particle size Dv50 of the second carbon-based material is greater than the volume distribution particle size Dv50 of the third carbon-based material. By adjusting the volume distribution particle size Dv50 of the second carbon-based material to be greater than the volume distribution particle size Dv50 of the third carbon-based material, it is advantageous to have a reasonable pore distribution in the thickness direction of the negative electrode membrane layer, improve the transmission performance of active ions and electrons, improve the electrolyte infiltration and retention properties of the negative electrode membrane layer, reduce the volume change of the negative electrode membrane layer, and further improve the cycle performance, safety performance and dynamic performance of the secondary battery.

[0149] In some embodiments, the volume distribution particle size Dv50 of the first carbon-based material is greater than the volume distribution particle size Dv50 of the third carbon-based material. By adjusting the volume distribution particle size Dv50 of the first carbon-based material to be greater than the volume distribution particle size Dv50 of the third carbon-based material, it is advantageous to have a reasonable pore distribution in the thickness direction of the negative electrode membrane layer, improve the transmission performance of active ions and electrons, improve the electrolyte infiltration and retention properties of the negative electrode membrane layer, reduce the volume change of the negative electrode membrane layer, and further improve the cycle performance, safety performance and dynamic performance of the secondary battery.

[0150] In further research, the inventors have found that the third carbon-based material can further improve the performance of the secondary battery, for example, at least one of the energy density, kinetic performance, and cycle performance of the secondary battery, by further satisfying one or more of the following conditions in addition to satisfying the above design:

[0151] In some embodiments, the third carbon-based material has a volume distribution particle size Dv50 of 10.0 μm to 22.0 μm, optionally 11.5 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 favorable for improving the transmission performance of active ions and electrons, and can further improve the dynamic performance of the secondary battery, and can also reduce the specific surface area of ​​the third carbon-based material, reduce the occurrence of side reactions, and improve the cycle performance of the secondary battery.

[0152] In some embodiments, the third carbon-based material has a (Dv90-Dv10) / Dv50 of less than 1.65, and optionally between 0.90 and 1.65. When the third carbon-based material has a (Dv90-Dv10) / Dv50 within the above range, the particle deposition performance is good, which is favorable for improving the compression density of the negative electrode membrane layer, and the energy density of the secondary battery can be further improved, and the negative electrode membrane layer has a suitable pore distribution, which can improve the electrolyte infiltration and retention properties of the negative electrode membrane layer, and can improve the cycle performance and dynamic performance of the secondary battery.

[0153] In some embodiments, the third carbon-based material has a powder OI value of 2.0 to 6.5, and optionally 2.0 to 6.0. The third carbon-based material has a small powder OI value and has active ion insertion ports in each direction of the particles, so that active ions can be rapidly received from the positive electrode, and the dynamic performance of the secondary battery can be further improved. In addition, the particles of the third carbon-based material have high uniformity, which is advantageous in dispersing the expansion rate during active ion insertion and reducing the thickness expansion rate of the negative electrode film layer, and thus the cycle performance of the secondary battery can be further improved.

[0154] In some embodiments, the third carbon-based material has a powder compaction density of 1.65 g / cm under a pressure of 20,000 N. 3 ~2.00g / cm 3 and optionally 1.68g / cm 3 ~1.98g / cm 3 When the powder compressed density of the third carbon-based material is within the above range, it can improve the compressed density of the negative electrode film layer, improve the energy density of the secondary battery, have a suitable pore distribution, improve the active ion and electron transmission performance, improve the electrolyte infiltration and retention properties of the negative electrode film layer, and further improve the cycle performance and dynamic performance of the secondary battery.

[0155] In some embodiments, the third carbon-based material has a tap density of 0.85 g / cm 3 ~1.25g / cm 3 and optionally 0.90 g / 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 the negative electrode film layer has a suitable pore distribution, which is favorable for improving the active ion and electron transmission performance, improving the electrolyte infiltration and retention properties of the negative electrode film layer, and further improving the cycle performance and dynamic performance of the secondary battery.

[0156] In some embodiments, the graphitization degree of the third carbon-based material is less than 96%, and optionally 90.5% 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 transmission performance of the negative electrode film layer, and for providing the secondary battery with both high energy density and good dynamic performance.

[0157] In some embodiments, the specific surface area of ​​the third carbon-based material is 0.9 m 2 / g~2.5m 2 / g, optionally 0.95m 2 / g~2.45m 2 When the specific surface area of ​​the third carbon-based material is within the above range, it is favorable for the rapid desorption of active ions, which can improve the dynamic performance of the secondary battery, reduce the consumption of active ions due to the formation of the SEI film, and improve the initial Coulombic efficiency of the secondary battery.

[0158] In some embodiments, the gram capacity of the third carbon-based material is 340mAh / g to 360mAh / g, optionally 345mAh / g to 360mAh / g. The gram capacity of the third carbon-based material being within the above range allows the third carbon-based material to have good active ion transmission performance, which improves the dynamic performance of the secondary battery, while also favoring the secondary battery to have high energy density.

[0159] 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).

[0160] 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 composition of the intermediate region 1023 may be the same as that of 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 from the second surface 102b of the negative electrode film layer to 0.7H, or as shown in FIG. 3, the composition of the intermediate region 1023 may be the same as that of 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 from the first surface 102a of the negative electrode film layer to 0.7H, 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.

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

[0162] 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%, which can improve the dynamic performance and energy density of the secondary battery while providing the secondary battery with good cycle performance.

[0163] In some embodiments, the second region of the negative electrode film layer may further include other known negative electrode active materials in the art other than the third carbon-based material, for example, may further include a silicon-based material, which plays a role in improving the channel structure in the negative electrode film layer, facilitating the infiltration and retention of the electrolyte, improving the dynamic performance of the secondary battery, and improving the negative electrode capacity to further improve the energy density of the secondary battery. Optionally, the silicon-based material may include one or more of silicon elemental material, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material.

[0164] 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 more, for example, 1% to 8%, 2% to 6%, or 3% to 7%, so that the kinetic performance and energy density of the secondary battery can be improved while the secondary battery has good cycle performance.

[0165] In some embodiments, the first region and the second region both contain silicon-based materials, 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 silicon-based material has a larger volume expansion than the carbon-based material, so that it is advantageous for the second region of the negative electrode membrane layer to have a high porosity, which is advantageous for improving the electrolyte infiltration property of the negative electrode membrane layer, improving the transmission performance of active ions, and improving the cycle performance and / or dynamic performance of the secondary battery. In addition, the high porosity of the second region of the negative electrode membrane layer can also improve the transmission performance of active ions in the first region of the negative electrode membrane layer.

[0166] In some embodiments, the intermediate region of the negative electrode film layer further comprises a silicon-based material.

[0167] In some embodiments, the first region, the second region and the middle region of the negative electrode membrane layer may further optionally include a negative electrode conductive agent and / or a negative electrode adhesive.

[0168] In the present application, the type of the negative electrode conductive agent is not particularly limited, and 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.

[0169] In the present application, the type of the negative electrode adhesive is not particularly limited, and 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).

[0170] In some embodiments, the first region, the second region, and the middle region of the negative electrode membrane layer may optionally include other additives. For example, the other additives may include a thickener, such as sodium carboxymethylcellulose (CMC), a PTC thermistor material, etc.

[0171] In some embodiments, 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 have high capacity and reasonable channel structure, and further favorable for the secondary battery to have high energy density and good cycle and kinetic performance.

[0172] In some embodiments, the negative electrode film layer has a compressed density of 1.50 g / cm 3 ~1.85g / cm 3 and optionally 1.55 g / cm3 ~1.80g / cm 3 This is advantageous for the negative electrode film layer to have high capacity and good active ion and electron transport properties, and is also advantageous for the secondary battery to have high energy density and good cycle and dynamic performances.

[0173] In some embodiments, the areal 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 This is advantageous for the negative electrode film layer to have high capacity and good active ion and electron transport properties, and is also advantageous for the secondary battery to have high energy density and good cycle and dynamic performances.

[0174] In some embodiments, the OI value of the negative electrode film layer is 40.0 or more, and optionally 5.0 to 40.0, which is advantageous for improving the active ion insertion performance of the negative electrode film layer, and also for allowing the negative electrode film layer to have a low thickness expansion rate, and is further advantageous for allowing the secondary battery to have both good cycle performance and kinetic performance.

[0175] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. An example of a metal foil may be a 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).

[0176] 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 primer 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.

[0177] The negative electrode current collector has two surfaces facing each other in the thickness direction, and the negative electrode film layer is provided on either 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, thickness, 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, it is considered that the negative electrode film layer falls within the scope of protection of the present application if the parameters of the negative electrode film layer on either side satisfy the present application.

[0178] In the present application, the presence or absence of a carbon coating layer on the surface of a material (eg, a first carbon-based material, a second carbon-based material, a third carbon-based material, etc.) can be determined by a transmission electron microscope.

[0179] In this application, the specific surface area 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 measured by an apparatus and method known in the art. For example, it can be tested by a nitrogen 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 apparatus may be a Tri-Star 3020 type specific surface area pore size analysis measuring instrument from Micromeritics, USA.

[0180] In the present application, the graphitization degree of a material (e.g., a first carbon-based material, a second carbon-based material, a third carbon-based material, etc.) has a meaning well known in the art, and can be tested by using equipment and methods well 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).

[0181] 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 meanings well known in the art, and indicate the particle size when the cumulative volume distribution percentage of the material reaches 10%, 50%, and 90%, respectively, and can be measured by equipment and methods well known in the art. For example, referring to GB / T 19077-2016, they can be measured using a laser particle size analyzer. The testing equipment can be a Mastersizer 3000 type laser particle size analyzer from Malvern Instruments Ltd., UK.

[0182] In this application, the powder compaction density of a material (e.g., a first carbon-based material, a second carbon-based material, a third carbon-based material, etc.) has a meaning well known in the art and can be measured by known instruments and methods 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 as follows: 1 g of sample powder is weighed and found to have a base area of ​​1.327 cm 2 The powder compaction density of the material at a pressure of 20,000N is recorded and calculated.

[0183] In this application, the tap density of a material (such as a first carbon-based material, a second carbon-based material, a third carbon-based material, etc.) has a meaning well known in the art and can be measured by known instruments and methods in the art. For example, it can be measured using a powder tap density tester, referring to GB / T 5162-2006. The test instrument can be Dan Dong 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.

[0184] In the present application, the powder OI value of a material (e.g., a first carbon-based material, a third carbon-based material, etc.) has a meaning well known in the art and can be measured by a known device and method in the art. For example, it can be measured using an X-ray diffraction device (e.g., Bruker D8 Discover), and the test is performed with reference to JIS K 0131-1996 and JB / T 4220-2011, by obtaining an X-ray diffraction spectrum of a powder sample, and the OI value=I 004 / I 110 The powder OI value of the sample can be calculated based on I 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. In the X-ray diffraction analysis test of the present application, a copper target is used as the anode target, CuKα radiation is used as the radiation source, the radiation wavelength is λ=1.5418A, the scanning 2θ angle range is 20° to 80°, and the scanning speed is 4° / min.

[0185] In this application, primary particles and secondary particles are both defined as they are known in the art. Primary particles refer to particles in a non-aggregated state. Secondary particles refer to particles in an aggregated state in which two or more primary particles are aggregated. Primary particles and secondary particles can be distinguished using scanning electron microscope (SEM) images.

[0186] In this application, the capacity 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 well known in the art and can be tested by a method well known in the art. An exemplary test method is as follows. A sample powder, a conductive agent carbon black (Super P), an adhesive polyvinylidene fluoride (PVDF), and a solvent N-methylpyrrolidone (NMP) are uniformly mixed in a mass ratio of 91.6:1.8:6.6 to prepare a slurry, which is then applied to the surface of a copper foil, which is a negative electrode current collector, and dried in an oven for preparation. 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 prepare an electrolyte solution with a concentration of 1 mol / L. Then, a metallic lithium sheet is used as the counter electrode, a polyethylene (PE) film is used as the separator, and the electrolyte solution is assembled into a CR2430-type button battery in an argon-protected glove box. 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 capacity per gram of the corresponding material (e.g., the first carbon-based material, the second carbon-based material, the third carbon-based material, etc.).

[0187] In this application, the surface density of the negative electrode film layer has a meaning well known in the art and can be tested by a method well 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 taken, and the surface area is S 1 The weight of each piece is measured and the size of the piece is measured. 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 -M0 ) / S 1 It is.

[0188] In this application, the compression density of the negative electrode film layer has a meaning well known in the art and can be tested by a method known in the art. The compression density of the negative electrode film layer = the surface density of the negative electrode film layer / the thickness of the negative electrode film layer. The thickness of the negative electrode film layer has a meaning well 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.

[0189] In this application, the porosity of the negative electrode film layer has a meaning well known in the art and can be measured by a method well known in the art. An exemplary test method is as follows: A negative electrode sheet 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 taken, punched into a small disk sample with a certain area, and the apparent volume V of the negative electrode sheet is measured. 1 Calculate the true volume V of the negative electrode sheet by referring to GB / T24586-2009, adopting the gas replacement method with inert gas (such as helium gas or nitrogen gas) as the medium, and using a true density tester. 2 Measure 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 powder falling off the edges and averaging the results. A Micromeritics AccuPyCII 1340 true density tester can be used as the tester.

[0190] In the present application, the OI value of the negative electrode film layer has a meaning well 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), and the test is performed by referring to JIS K 0131-1996 and JB / T 4220-2011 to obtain an X-ray diffraction spectrum of the negative electrode sheet, and the OI value = I 004 / I110 The OI value of the negative electrode film layer can be 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 the present application, a copper target is used as the anode target, CuKα rays are used as the radiation source, the radiation wavelength is λ=1.5418A, the scanning 2θ angle range is 20° to 80°, and the scanning speed is 4° / min.

[0191] The above-mentioned first active material, second active material, or negative electrode film layer can be sampled and tested for various parameters from a secondary battery manufactured according to the following steps.

[0192] The secondary battery is discharged (for safety reasons, the secondary battery is generally fully discharged), the secondary battery is removed, and the negative electrode sheet is taken out. The negative electrode sheet is immersed in dimethyl carbonate for a certain time (for example, 2 to 10 hours), and then the negative electrode sheet is taken out and dried at a certain temperature and time (for example, 60°C, 4 hours or more), and the negative electrode sheet is taken out after drying. In this case, the parameters related to the above-mentioned negative electrode film layer, such as the surface density, compressed density, porosity, and OI value of the negative electrode film layer, can be sampled and tested in the dried negative electrode sheet.

[0193] 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. The second active material is sampled first (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. The first active material is then 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 samples of the first and second active materials are obtained for testing the above-mentioned material parameters of the present application.

[0194] [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 includes the steps of providing a first slurry containing a first active material and a second slurry containing a second active material, applying the first slurry to a negative electrode current collector, applying the second slurry to the first slurry, and obtaining a negative electrode sheet after drying and cold pressing.

[0196] In some embodiments, the first active material and optional conductive agent, optional adhesive, and other optional 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 other optional 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 mixture of a first carbon-based material and a second carbon-based material.

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

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

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

[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 first active material, second active material, etc. are commercially available or can be 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 and 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 intermediate to room temperature to obtain an intermediate, and step 3 is to keep the intermediate at 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 spheroidal 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 spheroidal graphite having a desired particle size and topography can be obtained by subjecting flake graphite to a pretreatment, and optionally, the pretreatment includes steps such as crushing, classification, spheroidization, and purification.

[0207] In some embodiments, in step 1, the volume distribution particle size Dv50 of the raw material may be 7.0 μm to 25.0 μm, or 10.0 μm to 20.0 μm, which is advantageous for producing a first carbon-based material with a desired volume distribution particle size.

[0208] In some embodiments, in step 1, the specific surface area of ​​the raw material is 2.5 m 2 / g or more, 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 the 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 high capacity and high initial coulombic efficiency, and it is also advantageous for the first carbon-based material to have better kinetic performance.

[0209] In some embodiments, in step 2, the softening point temperature of the filler material is 102°C to 175°C. Optionally, the softening point temperature of the filler material is 106°C to 162°C, 106°C to 156°C, 106°C to 150°C, 106°C to 146°C, 106°C to 142°C, 110°C to 162°C, 110°C to 156°C, 110°C to 150°C, 110°C to 146°C, or 110°C to 142°C.

[0210] In some embodiments, in step 2, the volume distribution particle size Dv50 of the filler material 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 material 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 material and the raw material.

[0211] In some embodiments, in step 2, the coking value of the filler is 19%-47%, optionally 22%-40%. In the present application, the coking value of the filler has a well-known meaning in the art and can be measured by instruments and methods known in the art, for example, by referring to GB / T 8727-2008.

[0212] In certain embodiments, in step 2, the filler material comprises one or more of coal pitch, petroleum pitch, a polymer, and a resin, optionally comprising one or more of coal pitch and petroleum pitch.

[0213] In some embodiments, in step 2, the mass ratio of the filler material to the raw material is (10-40):100, optionally (10-30):100, (10-25):100, (10-20):100, (12-30):100, (12-20):100, (14-28):100, (15-25):100.

[0214] In step 2, it is advantageous to adjust the number and / or size of the holes in the outer region and the inner region of the first carbon-based material within a suitable range by adjusting one or more parameters of the type, softening point, coking value, amount of addition, etc. of the filling material within the above range, and the S of the first carbon-based material can be improved. 2 / S 1 It is advantageous to adjust the temperature to within an appropriate range.

[0215] By adjusting the parameters such as the type, softening point, coking value, and amount of the filler material within the above ranges, the filler material has a low viscosity and maintains good fluidity after being melted by heat, and the raw material particles are less likely to adhere to each other, which can reduce the aggregation of the raw material particles in the subsequent manufacturing process, thereby reducing the need to increase the depolymerization process, thereby increasing the surface defects of the first carbon-based material particles, and reducing the problems of increasing the surface active sites.

[0216] 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.

[0217] In some embodiments, the stepwise temperature ramp process includes a first temperature ramp process, a second temperature ramp process, and a third temperature ramp process.

[0218] In some embodiments, the first heating process includes heating to 200° C. to 250° C. and maintaining the temperature for 0.5 h to 3 h.

[0219] In some embodiments, the second temperature-raising process involves raising the temperature to 450° C. to 550° C. and maintaining the temperature for 0 h to 2 h. When the temperature-maintaining time is 0 h, no heat-maintaining process is performed when the temperature is raised 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

[0220] In some embodiments, the third heating process is performed at the first temperature T 1 and maintaining the temperature for a first time t 1 The key is to keep warm.

[0221] In the stepwise heating process, the temperature is first raised to 200°C-250°C, and the heating temperature is higher than the softening point temperature of the filler material, so the filler melts and softens due to the heat, and is kept warm for 0.5h-3h to be filled 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-coke state and a viscous liquid or solid, thereby preventing the filler from entering all the pore structure of the raw material. Finally, the temperature is raised to the first temperature, and the filler undergoes a carbonization reaction, so that the pore structure occupied by the filler material can be effectively filled.

[0222] 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.

[0223] In some embodiments, the heating rate of the first heating process may be 1° C. / min to 10° C. / min, and optionally 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 second heating process may be 1° C. / min to 10° C. / min, optionally 2° C. / min to 8° C. / min.

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

[0226] In some embodiments, in step 2, the first temperature T 1 For example, the first temperature T 1 Optionally, 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 any range of values ​​therein. 1 are 750℃~1100℃, 800℃~1100℃, and 850℃~1000℃.

[0227] In some embodiments, in step 2, the first time t 1 For example, the first time t 1 Optionally, the first time t may be 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, or any range of values ​​greater than or equal to 1 h. 1 is 2h~4h.

[0228] 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.

[0229] 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, argon, and helium.

[0230] In step 2, it is advantageous to adjust the number of holes and / or the size of holes in the outer region and the inner region of the first carbon-based material within a suitable range by adjusting one or more of the heating rate, the first temperature, the first time, the heating process, etc., within the above range, and the S of the first carbon-based material can be obtained. 2 / S 1 It is advantageous to adjust the temperature to within an appropriate range.

[0231] In some embodiments, in step 3, the second temperature T 2 Optionally, the second temperature T 2 are 2025℃~2525℃, 2025℃~2475℃, 2025℃~2425℃, 2025℃~2375℃, 2075℃~2525℃, 2075℃~2475℃, 2075℃~2425℃, 2075℃~2375℃.

[0232] In some embodiments, in step 3, the second time t 2 For example, the second time t 1 Optionally, the second time t may be 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, or any range of values ​​greater than or equal to 2h. 2 is 2h~5h.

[0233] 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.

[0234] 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, argon, and helium.

[0235] In step 3, by adjusting one or more of the second temperature and the second time within the above ranges, it is advantageous to adjust the content of disordered carbon in the first carbon-based material within an appropriate range, and it is advantageous for the first carbon-based material to have an appropriate graphitization degree, layer spacing, etc.

[0236] In the above-mentioned method for producing the first carbon-based material, the S of the first carbon-based material can be obtained by adjusting one or more of the parameters of the natural graphite, the parameters of the filling material, the heating rate, the first temperature, the first time, the heating process, the second temperature, the second time, etc., within the above-mentioned ranges. 2 / S 1 It is advantageous to adjust parameters such as graphitization degree, layer spacing, volume per gram, specific surface area, particle size, powder pressed density, tap density, powder OI value, etc.

[0237] [Positive electrode sheet]

[0238] 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 of the positive electrode current collector, and the positive electrode film layer is provided on one or both of the two facing surfaces of the positive electrode current collector.

[0239] The positive electrode current collector may be a metal foil or a composite current collector. An example of the metal foil may be an 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).

[0240] 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). The adhesive used in the positive electrode membrane layer includes, for example, one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene ternary copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene ternary copolymer, 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.

[0241] As the positive electrode active material, any positive electrode active material known in the art for use in secondary batteries can be used.

[0242] When the secondary battery of the present application is a lithium ion battery, the positive electrode active material may include, but is not limited to, one or more of lithium-containing transition metal oxides, lithium-containing phosphates, and their respective modified compounds. Examples of the lithium transition metal oxides may 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 their respective modified compounds. Examples of the lithium-containing phosphates may 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 their respective modified compounds.

[0243] 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 their modified compounds 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.

[0244] In some embodiments, for 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 Co1 / 3 Mn 1 / 3 O 2 (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 1.0 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:

[0245] In the present application, the modifying compound for each of the positive electrode active materials can perform doping modification and / or surface coating modification on the positive electrode active material.

[0246] [Electrolyte]

[0247] In some embodiments, the electrolyte is an electrolyte solution including an electrolyte salt and a solvent.

[0248] The type of the electrolyte salt is not specifically limited and can be selected according to actual needs.

[0249] 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 difluorosulfonylimide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium disoxalate borate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ), lithium difluorodisalophosphate (LiDFOP), and lithium tetrafluorooxalophosphate (LiTFOP).

[0250] The type of the solvent is not specifically limited and can be selected according to actual needs. In some embodiments, by way of example, the 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).

[0251] In some embodiments, the electrolyte may optionally include an additive. For example, the additive may include a negative electrode film-forming additive, a positive electrode film-forming additive, or an additive capable of improving a certain performance of the secondary battery, such as an additive for improving the overcharge performance of the secondary battery, an additive for improving the high temperature performance of the secondary battery, or an additive for improving the low temperature output performance of the secondary battery.

[0252] [Separator]

[0253] In the present application, the type of the separator is not particularly limited, and any well-known porous structure separator having good chemical stability and mechanical stability can be selected.

[0254] In some embodiments, the separator may be made of one or more materials selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer may be the same or different.

[0255] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet can be wound or stacked to produce an electrode assembly.

[0256] In some embodiments, the secondary battery can include an exterior case that can be used to seal the electrode assembly and electrolyte.

[0257] 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-type 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).

[0258] In the present application, the shape of the secondary battery is not particularly limited, and may be cylindrical, rectangular, or any other shape. For example, FIG. 5 shows a secondary battery 5 having a rectangular structure as an example.

[0259] 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 chamber. The case 51 has an opening communicating with the chamber, and the cover plate 53 covers the opening to seal the chamber. The positive electrode sheet, the negative electrode sheet and the separator may form an electrode assembly 52 by a winding process or a lamination process. The electrode assembly 52 is sealed in the chamber. The electrode assembly 52 is infiltrated with an electrolyte. The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and may be adjusted according to needs.

[0260] 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.

[0261] 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.

[0262] 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.

[0263] Optionally, the battery module 4 further includes a housing having an accommodating space, and the multiple secondary batteries 5 are accommodated in the accommodating space.

[0264] 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.

[0265] 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 box and a plurality of battery modules 4 provided in the battery box. The battery box includes an upper housing 2 and a lower housing 3, and the upper housing 2 is covered by 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 box in any manner.

[0266] The present application further provides a power consuming device including at least one of the secondary battery, battery module, and battery pack of the present application. The secondary battery, battery module, and battery pack may be used as a power source for the power consuming device, or may be used as an energy storage unit 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, a satellite, an energy storage system, etc.

[0267] The power consumption device can select a secondary battery, a battery module or a battery pack according to its usage demand.

[0268] 10 is a schematic diagram of an example power consuming device, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, that may employ a battery pack or battery module to meet the high power and high energy density demands of the power consuming device.

[0269] Other examples of power consuming devices may be mobile phones, tablet computers, notebook computers, etc. Such power consuming devices are usually required to be thin and may employ secondary batteries as their power source.

[0270] Working Example

[0271] The following examples are provided to more specifically describe the disclosure of the present application, and these examples are merely for the purpose of interpreting the present application, since it is obvious to those skilled in the art that various modifications and changes are made within the scope of the disclosure of the present application.Unless otherwise stated, 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 obtained by synthesis according to conventional methods and can be used directly without further treatment, and the equipment used in the examples is commercially available.

[0272] In each of the following Examples and Comparative Examples, the first carbon-based material used can be produced by the following method of the present application.

[0273] (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 Dv50, layer spacing, and S of the first carbon-based material were measured. 2 / S 1 can be controlled according to the manufacturing process of the first carbon-based material described in the present application so that the carbon-based material content is within the range of Table 1.

[0275] The first carbon-based material, S 2 / S 1is tested by the following method. The adhesive for sample production is mixed uniformly with the powder of the first carbon-based material, and then coated on a copper foil and dried at 60°C for 30 min to prepare it. 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 tester can be an IB-09010 CP-type argon ion cross-section polisher from JEOL Co., Ltd. A scanning electron microscope is used to scan the cross section of the first carbon-based material. The test can refer to JY / T010-1996. The tester can be a Sigma 300-type scanning electron microscope from ZEISS, 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 defined as the outer region, and the region inside the outer region is defined as the inner region, where L is the length of the minor axis of the particle of the first carbon-based material. The total pore area S of the outer region of the first carbon-based material was calculated using image processing software. 1 and the total pore area S of the internal region of the first carbon-based material. 2 The image processing software may be AVIZO.

[0276] In each of the following Examples and Comparative Examples, the second carbon-based material and the third carbon-based material are commercially available.

[0277] The secondary batteries of Examples 1 to 25 were all produced by the following method.

[0278] A mixture of the first carbon-based material and the second carbon-based material (see Table 1 for details, mass ratio 50:50) as the first active material, carbon black (Super P) as the conductive agent, sodium carboxymethylcellulose as the thickener, and styrene butadiene rubber as the adhesive were thoroughly mixed in a weight ratio of 96.4:1:1.2:1.4 in an appropriate amount of deionized water as the solvent, to form a first slurry. A third carbon-based material (see Table 1 for details) as the second active material, carbon black (Super P) as the conductive agent, sodium carboxymethylcellulose as the thickener, and styrene butadiene rubber as the adhesive were thoroughly mixed in a weight ratio of 96.4:1:1.2:1.4 in an appropriate amount of deionized water as the solvent, to form a second slurry. The first and second slurries were extruded simultaneously by a double chamber coating device. The first slurry was applied to a copper foil as a negative electrode current collector, and the second slurry was applied to the first slurry. After drying and cold pressing, a negative electrode sheet was obtained. The coating weights of the first and second slurries were the same. The compressed density of the negative electrode film layer was 1.72 g / cm 3 ~1.76g / cm 3 It was.

[0279] Lithium iron phosphate, 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.

[0280] 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 above organic solvent to prepare an electrolyte solution with a concentration of 1 mol / L.

[0281] Using a polyethylene film as a separator, the positive electrode sheet and the negative electrode sheet prepared above were arranged in order, and the separator was placed between the positive electrode sheet and the negative electrode sheet to perform an insulating 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 after that, and a secondary battery was obtained through processes such as vacuum sealing, standing, chemical formation, and shaping.

[0282] Comparative Example 1

[0283] The manufacturing method of the secondary battery of Comparative Example 1 was similar to those of Examples 1 to 25, except for the manufacture of the negative electrode sheet.

[0284] The third carbon-based material shown in Table 1, the conductive agent carbon black (Super P), the thickener sodium carboxymethylcellulose, and the adhesive styrene butadiene rubber were thoroughly 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 slurry. The slurry was applied to copper foil as a negative electrode current collector, dried, and cold pressed to obtain a negative electrode sheet. The compressed density of the negative electrode film layer was 1.72 g / cm. 3 ~1.76g / cm 3 It was.

[0285] Performance Testing

[0286] (1) Rapid charging performance test of secondary batteries At 25°C, the secondary battery was charged at a constant current of 0.33 C up to 3.65 V, then charged at a constant voltage until the current reached 0.05 C. After leaving the battery to stand for 5 minutes, the secondary battery was discharged at a constant current of 0.33 C down to 2.5 V, and the actual capacity was recorded as C0.

[0287] Then, 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 sequence to a negative electrode cutoff potential of 3.65V or 0V (based on the first one reached), and discharged to 2.5V at 1C0 each time charging was completed. The corresponding negative electrode potentials were recorded when charging to 10%, 20%, 30%, ..., 80% SOC (State of Charge) at different charge rates, and the charge rate-negative electrode potential curves at different SOC states were drawn and linearly fitted to obtain the corresponding charge rates when the negative electrode potential at different SOC states was 0V. The charge rates were the charge windows at the SOC states, and were respectively C10%SOC, C20%SOC, C30%SOC, C40%SOC, C50%SOC, C60%SOC, C70%SOC, C80%SOC, C90%SOC, C10%SOC, C120%SOC, C130%SOC, C140%SOC, C150%SOC, C160%SOC, C170%SOC, C180%SOC, C20%SOC, C25%SOC, C30%SOC, C40%SOC, C50%SOC, C60%SOC, C70%SOC, C80%SOC, C90%SOC, C10%SOC, C20 ... SOC, C70%SOC, C80%SOC, and the charging time t (assuming that lithium does not precipitate in the secondary battery) for the secondary battery to be charged from 10% SOC to 80% SOC was calculated according to the formula (60 / C20%SOC+60 / C30%SOC+60 / C40%SOC+60 / C50%SOC+60 / C60%SOC+60 / C70%SOC+60 / C80%SOC)×10%, and the unit was min. The shorter this charging time, the better the dynamic performance of the secondary battery.

[0288] (2) Cycle performance test of secondary batteries

[0289] At 45°C, the secondary battery was charged at a constant current of 1C up to 3.65V, then charged at a constant voltage until the current reached 0.05C, and after leaving the battery to stand for 5 minutes, the secondary battery was discharged at a constant current of 1C up to 2.5V, and the discharge capacity at that time was recorded and used as the initial discharge capacity. The secondary battery was subjected to a cycle charge-discharge test according to the above method, and the discharge capacity of each cycle was recorded. The test was stopped until the discharge capacity of the secondary battery after cycling had decayed to 80% of the initial discharge capacity, and the number of cycles of the secondary battery was recorded.

[0290] (3) Testing the thickness expansion rate of the negative electrode film layer

[0291] At 25°C, the secondary battery was charged at a constant current of 0.33C up to 3.65V, then charged at a constant voltage of 0.05C until the current reached 0.05C. After leaving the battery for 10 minutes, the negative electrode sheet in the 100% SOC state was taken out and the average thickness of the negative electrode film layer was measured. 1 The thickness expansion rate of the negative electrode film layer = (D 1 -D 0 ) / D 0 D 0 indicates the average thickness of the negative electrode film layer of the negative electrode sheet after cold pressing.

[0292] The negative electrode film layer of Comparative Example 1 contains only the third carbon-based material, and the powder compressed density of the third carbon-based material is small, so that the compressed density of the negative electrode film layer is improved (the compressed density of the negative electrode film layer of Comparative Example 1 is 1.72 g / cm 3 ~1.76g / cm 3 Increasing the energy density of a battery by increasing the compression density of the negative electrode film layer will result in a deterioration in both cycle performance and dynamic performance of the battery, and a high thickness expansion rate of the negative electrode film layer. In addition, the capacity per gram of the third carbon-based material is low, so the effect of increasing the compression density of the negative electrode film layer on improving the energy density of the battery is limited.

[0293] The first carbon-based material and / or the second carbon-based material have the advantage of high capacity. As can be seen from Table 1, the first region of the negative electrode film layer simultaneously comprises the first carbon-based material and the second carbon-based material, the first carbon-based material has a pore structure, and the second carbon-based material comprises artificial graphite, so that the negative electrode sheet can have high compression density and low volume change, and the negative electrode film layer can have a reasonable pore distribution, which is favorable for the transmission of active ions. As a result, under the premise of the battery having high energy density, it can have high safety performance and good kinetic performance and cycle performance.

[0294] 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. [Table 1-1] [Table 1-2]

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 has 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, and a region of the negative electrode film layer 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; A region within a thickness range of 0.3H from a first surface of the negative electrode film layer is defined as a second region of the negative electrode film layer; The first region includes a first active material, the first active material includes a first carbon-based material and a second carbon-based material, the first carbon-based material has a pore structure, and the second carbon-based material includes artificial graphite. Secondary battery.

2. The second carbon-based material includes secondary particles of artificial graphite, and optionally, the proportion of the secondary particles of artificial graphite in the second carbon-based material is 50% or more. The secondary battery according to claim 1 .

3. a layer spacing of a 002 plane of the second carbon-based material is larger than a layer spacing of a 002 plane of the first carbon-based material, and / or a graphitization degree of the second carbon-based material is smaller than a graphitization degree of the first carbon-based material; The secondary battery according to claim 1 or 2.

4. The capacity per gram of the second carbon-based material is less than the capacity per gram of the first carbon-based material; The secondary battery according to any one of claims 1 to 3.

5. The layer spacing of the 002 plane of the second carbon-based material is 0.33600 nm or less, and optionally 0.33571 nm to 0.33600 nm; The secondary battery according to any one of claims 1 to 4.

6. The capacity per gram of the second carbon-based material is 353 mAh / g or greater, optionally 355 mAh / g to 365 mAh / g; The secondary battery according to any one of claims 1 to 5.

7. The powder compaction density of the second carbon-based material under a pressure of 20,000 N is 1.75 g / cm ３ ~2.05g / cm ３ and optionally 1.78 g / cm ３ ~2.00g / cm ３ That is, The secondary battery according to any one of claims 1 to 6.

8. The second carbon-based material includes artificial graphite, and a surface of the artificial graphite does not have a carbon coating layer. The secondary battery according to any one of claims 1 to 7.

9. The second carbon-based material satisfies at least one of the following: (1) the volume distribution particle size Dv10 of the second carbon-based material is 6 μm to 12 μm, optionally 6.5 μm to 11.5 μm; (2) The volume distribution particle size Dv50 of the second carbon-based material is 12.0 μm to 22.0 μm, and optionally 13.5 μm to 20.5 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 tap density of the second carbon-based material is 0.85 g / cm ３ ~1.30g / cm ３ and optionally 0.90 g / cm ３ ~1.30g / cm ３ That is, (5) The specific surface area of ​​the second carbon-based material is 1.0 m ２ / g to 2.9 m ２ / g, optionally 1.2m ２ / g to 2.5m ２ / g, The secondary battery according to any one of claims 1 to 8.

10. The first carbonaceous material has a pore area 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 and one or more pore structures, The secondary battery according to any one of claims 1 to 9.

11. 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 particle surface of the first carbon-based material to the inside of the particle by a distance of 0.25L, 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 and optionally, 1.5≦S ２ / S １ ≦500, and optionally 2≦S ２ / S １ ≦450; The secondary battery according to any one of claims 1 to 10.

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

13. The first carbon-based material satisfies at least one of the following: (1) The specific surface area of ​​the first carbon-based material is 0.7 m ２ / g to 1.8m ２ / g, optionally 0.8m ２ / g to 1.6m ２ / g, (2) The volume distribution particle size Dv50 of the first carbon-based material is 8.0 μm to 25.0 μm, and optionally 10.0 μm to 20.0 μm; (3) The volume distribution particle size Dv90 of the first carbon-based material is 16.0 μm to 35.0 μm, and optionally 17.0 μm to 32.0 μm; (4) The (Dv90-Dv10) / Dv50 of the first carbon-based material is 1.50 or less, and optionally 0.7 to 1.40; (5) The powder compression density of the first carbon-based material under a pressure of 20,000 N is 1.75 g / cm ３ ~1.95g / cm ３ and optionally 1.80 g / cm ３ ~1.90g / cm ３ That is, (6) The tap density of the first carbon-based material is 0.80 g / cm ３ ~1.50g / cm ３ and optionally 0.85 g / cm ３ ~1.45g / cm ３ That is, (7) The graphitization degree of the first carbon-based material is 93.5% or more, and optionally 93.8% to 98%; (8) The powder OI value of the first carbon-based material is 8 to 18, optionally 8 to 16; (9) The capacity per gram of the first carbon-based material is 354 mAh / g or more, and optionally 354 mAh / g to 370 mAh / g; (10) In a peak division spectrum of an X-ray diffraction spectrum of the first carbon-based material, there are two diffraction peaks within a range of 2θ from 25.5° to 27.5°, and of the two diffraction peaks, the smaller of 2θ is a first peak and the larger of 2θ is a second peak, and optionally, the ratio of the peak intensity of the first peak to the peak intensity of the second peak is 10:90 to 40:

60. The secondary battery according to any one of claims 1 to 12.

14. The mass ratio of the first carbonaceous material in the first active material is 20 wt % or more, and optionally 30 wt % to 70 wt %; The secondary battery according to any one of claims 1 to 13.

15. the second region comprises a second active material, the second active material comprising a third carbon-based material, optionally having a carbon coating layer on a surface of the third carbon-based material; The secondary battery according to any one of claims 1 to 14.

16. The third carbon-based material includes graphite having a carbon coating layer on a surface thereof, and optionally, the graphite includes at least one of artificial graphite and natural graphite. The secondary battery according to claim 15.

17. The third carbon-based material includes artificial graphite having a carbon coating layer on a surface thereof, and the artificial graphite includes secondary particles, and optionally, the proportion of the secondary particles in the artificial graphite is 50% or more. The secondary battery according to claim 15 or 16.

18. a layer spacing of a 002 plane of the second carbon-based material is smaller than a layer spacing of a 002 plane of the third carbon-based material, and / or a graphitization degree of the second carbon-based material is larger than a graphitization degree of the third carbon-based material; The secondary battery according to any one of claims 15 to 17.

19. The capacity per gram of the second carbon-based material is greater than the capacity per gram of the third carbon-based material; The secondary battery according to any one of claims 15 to 18.

20. The powder compaction density of the second carbon-based material under a pressure of 20,000 N is greater than the powder compaction density of the third carbon-based material under a pressure of 20,000 N, and / or the powder compaction density of the first carbon-based material under a pressure of 20,000 N is greater than the powder compaction density of the third carbon-based material under a pressure of 20,000 N; The secondary battery according to any one of claims 15 to 19.

21. The volume distribution particle size Dv50 of the second carbon-based material is larger than the volume distribution particle size Dv50 of the third carbon-based material, and / or the volume distribution particle size Dv50 of the first carbon-based material is larger than the volume distribution particle size Dv50 of the third carbon-based material; The secondary battery according to any one of claims 15 to 20.

22. The third carbon-based material satisfies at least one of the following: (1) The volume distribution particle size Dv50 of the third carbon-based material is 10.0 μm to 22.0 μm, and optionally 11.5 μm to 20.0 μm; (2) the (Dv90-Dv10) / Dv50 of the third carbon-based material is 1.65 or less, and optionally 0.90 to 1.65; (3) the powder OI value of the third carbon-based material is 2.0 to 6.5, optionally 2.0 to 6.0; (4) The powder compression density of the third carbon-based material under a pressure of 20,000 N is 1.65 g / cm ３ ~2.00g / cm ３ and optionally 1.68 g / cm ３ ~1.98g / cm ３ That is, (5) The tap density of the third carbon-based material is 0.85 g / cm ３ ~1.25g / cm ３ and optionally 0.90 g / cm ３ ~1.25g / cm ３ That is, (6) The graphitization degree of the third carbon-based material is 96% or less, and optionally 90.5% to 95.5%; (7) The specific surface area of ​​the third carbon-based material is 0.9 m ２ / g to 2.5m ２ / g, optionally 0.95m ２ / g to 2.45 m ２ / g, (8) The capacity per gram of the third carbon-based material is between 340 mAh / g and 360 mAh / g, optionally between 345 mAh / g and 360 mAh / g; The secondary battery according to any one of claims 15 to 21.

23. The first region and / or the second region further comprise a silicon-based material, and optionally, the first region and the second region both comprise 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. The secondary battery according to any one of claims 1 to 22.

24. an intermediate region located between the first region and the second region includes the first active material and / or the second active material; The secondary battery according to any one of claims 1 to 23.

25. A power consuming device comprising the secondary battery according to any one of claims 1 to 24.

Images