Secondary battery and power consumption device

Abstract

The present application provides a secondary battery and a power consumption device. The secondary battery includes a negative electrode current collector and a negative electrode sheet formed on at least one surface of the negative electrode current collector and including a negative electrode film layer containing a negative electrode active material. The negative electrode active material includes a first carbon-based material and a second carbon-based material. The first carbon-based material has a pore structure, and at least a part of the surface of the second carbon-based material has a carbon coating layer. On the premise that the secondary battery has a high energy density, the present application can achieve both good kinetic performance and storage performance.

Description

Technical Field

[0001] This application belongs to the field of battery technology, and specifically relates to secondary batteries and power consumption devices.

Background Art

[0002] In recent years, secondary batteries have been widely used in many fields such as energy storage power systems like hydro, thermal, wind, and solar power plants, as well as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. As the application range of secondary batteries becomes increasingly wide, profound challenges have been posed to the performance of secondary batteries. For example, it is required that secondary batteries can balance various performances such as energy density, kinetic performance, and service life. However, the problem faced by the prior art is that when improving the kinetic performance of secondary batteries, it is often difficult to balance the energy density of secondary batteries. When improving the energy density of secondary batteries, it often affects the kinetic performance and service life of secondary batteries.

Summary of the Invention

[0003] This application is made in view of such problems, and its purpose is to provide a secondary battery and a power consumption device in which the secondary battery can have a high energy density while achieving good kinetic performance and storage performance.

[0004] The first aspect of this application is a secondary battery including a negative electrode sheet, where 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 and containing a negative electrode active material. The negative electrode active material includes a first carbon-based material and a second carbon-based material. The first carbon-based material has a pore structure, and at least a part of the surface of the second carbon-based material has a carbon coating layer, and a secondary battery is provided.

[0005] In their intensive research, the inventors have found that the negative electrode active material in the negative electrode film layer simultaneously contains a first carbon-based material and a second carbon-based material, the first carbon-based material has a pore structure, and a carbon coating layer is provided on at least a part of the surface of the second carbon-based material, so that the characteristics of high capacity and high compression density of the first carbon-based material and the good kinetic characteristics of the second carbon-based material can be fully exerted. As a result, the negative electrode sheet can have a high compression density, a low volume change, and high active ion transfer performance. Furthermore, it has been found that a secondary battery using the negative electrode sheet can achieve both good kinetic performance and storage performance on the premise of having a high energy density.

[0006] In any embodiment of the present application, the interlayer distance of the crystal plane of the second carbon-based material 002 is larger than the interlayer distance of the crystal plane of the first carbon-based material 002. By making the interlayer distance of the 002 crystal plane of the second carbon-based material larger than the interlayer distance of the 002 crystal plane of the first carbon-based material, it is advantageous for achieving both high energy density and good kinetic performance of the secondary battery.

[0007] In any embodiment of the present application, the gram capacity (capacity per gram) of the second carbon-based material is smaller than the gram capacity of the first carbon-based material. By combining and using the first carbon-based material having a high capacity and the second carbon-based material having a carbon coating layer, it is advantageous for achieving both high energy density and good kinetic performance of the secondary battery.

[0008] In any embodiment of the present application, the powder compression density of the second carbon-based material under a pressing force of 5000 kg is smaller than the powder compression density of the first carbon-based material under a pressing force of 5000 kg. By combining and using the second carbon-based material having a low powder compression density and the first carbon-based material having a high powder compression density, it is advantageous for the negative electrode film layer to have a reasonable pore structure, for the negative electrode film layer to achieve both good active ion transport performance and electron transport performance, and further for the secondary battery to achieve both high energy density and good cycle performance and kinetic performance.

[0009] In any embodiment of the present application, the peak intensity ratio I of the D peak to the G peak in the Raman spectrum of the second carbon-based material D / I G is greater than the peak intensity ratio I of the D peak to the G peak in the Raman spectrum of the first carbon-based material D / I G . By adjusting I of the second carbon-based material D / I G to be greater than I of the first carbon-based material D / I G , it is advantageous for improving the surface stability of the entire negative electrode active material, reducing the occurrence of side reactions, and improving the storage performance. On the other hand, it is also advantageous for the secondary battery to have good kinetic performance.

[0010] In any embodiment of the present application, the second carbon-based material includes secondary particles. Optionally, the quantitative ratio of the secondary particles in the second carbon-based material is 50% or more. When the second carbon-based material contains an appropriate ratio of secondary particles, the active ion channels in the negative electrode film layer can be increased, the insertion path of active ions can be shortened, the kinetic performance of the secondary battery can be further improved, and polarization and side reactions can also be reduced. Therefore, good storage performance can also be achieved for the secondary battery.

[0011] In any embodiment of the present application, the peak intensity ratio I of the D peak to the G peak in the Raman spectrum of the second carbon-based material D / I G is ≧0.23 (0.23 or more), and optionally 0.23 - 0.41. By adjusting I of the second carbon-based material D / I G within the above range, the active ion transport performance of the second carbon-based material becomes better, which is advantageous for improving the kinetic performance of the secondary battery.

[0012] In any embodiment of the present application, the powder compression density of the second carbon-based material under a pressing force of 5000 kg is ≧1.65 g / cm 3 and optionally 1.65 g / cm 3 -1.90 g / cm 3That is. By adjusting the powder compression density of the second carbon-based material within the above range, it is advantageous to form a reasonable pore structure between the particles of the negative electrode film layer. Thereby, it is advantageous for the secondary battery to achieve both high energy density and good kinetic performance.

[0013] In any embodiment of the present application, the interlayer distance of the crystal plane of the second carbon-based material 002 is ≤ 0.336217 nm (not exceeding 0.336217 nm), and optionally 0.335787 nm - 0.336217 nm. By adjusting the interlayer distance of the second carbon-based material within the above range, it is advantageous for the rapid insertion and desorption of active ions, so it is advantageous to improve the active ion transport performance of the negative electrode film layer. In addition, since the second carbon-based material can have high surface stability and high gram capacity, the occurrence of side reactions can be reduced.

[0014] In any embodiment of the present application, the specific surface area of the second carbon-based material is ≥ 0.90 m 2 / g, and optionally 0.9 m 2 / g - 2.5 m 2 / g. By adjusting the specific surface area of the second carbon-based material within the above range, it is advantageous for the rapid insertion and desorption of active ions, so the kinetic performance of the secondary battery can be further improved. In addition, it is advantageous to reduce the occurrence of side reactions and reduce the consumption of active ions due to the formation of the SEI film, so it is also advantageous for the secondary battery to achieve both high initial Coulomb efficiency and good cycle performance and storage performance.

[0015] In any embodiment of the present application, the volume distribution particle size Dv50 of the second carbon-based material is ≥ 10 μm, and optionally 10 μm - 22 μm. When the volume distribution particle size Dv50 of the second carbon-based material is within the above range, the specific surface area of the second carbon-based material can be reduced, the occurrence of side reactions can be reduced, and the storage performance and / or cycle performance of the secondary battery can be improved. In addition, since it is also advantageous to improve the transport performance of active ions and electrons, the kinetic performance of the secondary battery can be further improved.

[0016] In any embodiment of the present application, the particle size distribution (Dv90 - Dv10) / Dv50 of the second carbon-based material is ≤ 1.65, and optionally 0.9 - 1.65. When the particle size distribution (Dv90 - Dv10) / Dv50 of the second carbon-based material is within the above range, its particle deposition performance is good, which is beneficial to improving the compression density of the negative electrode film layer and the energy density of the secondary battery. Also, it is beneficial to form a reasonable pore structure between the particles of the negative electrode film layer, improve the transport performance of active ions and electrons, and further improve the kinetic performance of the secondary battery.

[0017] In any embodiment of the present application, the tap density of the second carbon-based material is ≥ 0.85 g / cm 3 and optionally 0.9 g / cm 3 - 1.25 g / cm 3 When the tap density of the second carbon-based material is within the above range, the compression density of the negative electrode film layer can be improved, and the energy density of the secondary battery can be improved. Also, it is beneficial to form a reasonable pore structure between the particles of the negative electrode film layer, improve the transport performance of active ions and electrons, and further improve the kinetic performance of the secondary battery.

[0018] In any embodiment of the present application, the gram capacity of the second carbon-based material is ≥ 340 mAh / g, and optionally 340 mAh / g - 360 mAh / g. By adjusting the gram capacity of the second carbon-based material within the above range, while improving the energy density of the secondary battery, the second carbon-based material can have good active ion transport performance, which is also beneficial to improving the kinetic performance of the secondary battery.

[0019] In any embodiment of the present application, the second carbon-based material includes at least one of artificial graphite and natural graphite. Optionally, the second carbon-based material includes artificial graphite.

[0020] In any embodiment of the present application, the first carbon-based material includes one or more pore structures having a pore area of 0.1 μm 2 or more, and optionally 0.12 μm 2 - 2.5 μm 2It includes one or more pore structures having the above pore area. When the first carbon-based material includes a pore structure having the above pore area, the pore structure can secure an expansion space necessary for volume change of its particles, thereby further reducing the risk of generation of a new interface due to particle crushing, further reducing the occurrence of side reactions, and improving the storage performance of the secondary battery.

[0021] In any embodiment of the present application, the first carbon-based material includes an external region and an internal region located inside the external region. The external region refers to a region extending from the surface of the particles of the first carbon-based material to the inside of the particles at a distance of 0.25L, where L refers to the minor axis length of the particles of the first carbon-based material. The total pore area of the external region is S 1 represented as, and the total pore area of the internal region is S 2 represented as, and S 2 >S 1 is. When the first carbon-based material further satisfies S 2 >S 1 the initial Coulomb efficiency of the secondary battery can be improved, and the storage performance of the secondary battery can be further improved.

[0022] In any embodiment of the present application, 1.5 ≤ S 2 / S 1 ≤ 500, and optionally, 2 ≤ S 2 / S 1 ≤ 450. When S 2 / S 1 is within the above range, a high energy density and good storage performance of the secondary battery can be better balanced.

[0023] In any embodiment of the present application, the area of the pore structure in the external region of the first carbon-based material is 0.15 μm 2 or less, and optionally 0.13 μm 2The following is achieved. By controlling the area of the pore structure in the outer region of the first carbon-based material within the above range, a dense structure can be imparted to the outer region of the first carbon-based material, thereby effectively improving the structural stability of the first carbon-based material, avoiding as much as possible the penetration of the electrolyte into the pore structure inside the first carbon-based material particles, and further effectively improving the storage performance of the secondary battery.

[0024] In any embodiment of the present application, the inner region of the first carbon-based material includes one or more pore structures having an area of 0.15 μm 2 or more, and optionally includes one or more pore structures having an area of 0.15 μm 2 -2.0 μm 2 or more. By the inner region of the first carbon-based material including pore structures of the above size, a sufficient and stable expansion space is ensured due to the volume change of the first carbon-based material particles, the risk of crushing of the first carbon-based material particles is reduced, the occurrence of side reactions is reduced, while the compression density of the negative electrode film layer can be improved.

[0025] In any embodiment of the present application, the first carbon-based material has a carbon coating layer on at least a part of its surface.

[0026] In any embodiment of the present application, the first carbon-based material includes primary particles. Optionally, the quantitative ratio of the primary particles in the first carbon-based material is 50% or more. When the first carbon-based material includes an appropriate ratio of primary particles, it has high structural stability and reduces the occurrence of side reactions, so the storage performance of the secondary battery is improved, and also the compression density of the negative electrode film layer is improved, so the energy density of the secondary battery can be improved.

[0027] In any embodiment of the present application, the specific surface area of the first carbon-based material is ≤ 2.3 m 2 and optionally 0.7 m 2 / g - 2.3 m 2 / g. Since the first carbon-based material has a low specific surface area, it can reduce the consumption of active ions due to the formation of the SEI film, reduce the occurrence of side reactions, and improve the initial Coulomb efficiency and storage performance of the secondary battery.

[0028] In any embodiment of the present application, the volume distribution particle size Dv50 of the first carbon-based material is ≧6.0 μm, and optionally 6.0 μm - 25.0 μm.

[0029] In any embodiment of the present application, the volume distribution particle size Dv90 of the first carbon-based material is ≧16.0 μm, and optionally 16.0 μm - 40.0 μm.

[0030] When the volume distribution particle size Dv50 and / or Dv90 of the first carbon-based material is within the above range, it is advantageous for improving the transport performance of active ions and electrons, so the kinetic performance of the secondary battery can be improved. Also, the specific surface area of the first carbon-based material can be further reduced, the occurrence of side reactions can be decreased, and the storage performance of the secondary battery can be improved.

[0031] In any embodiment of the present application, the particle size distribution (Dv90 - Dv10) / Dv50 of the first carbon-based material is ≦1.55, and optionally 0.9 - 1.55. When the particle size distribution (Dv90 - Dv10) / Dv50 of the first carbon-based material is within the above range, its particle deposition performance is good, which is advantageous for improving the compression density of the negative electrode film layer and the energy density of the secondary battery. Also, it is advantageous for forming a reasonable pore structure between the particles of the negative electrode film layer, improving the transport performance of active ions and electrons, and improving the kinetic performance of the secondary battery.

[0032] In any embodiment of the present application, the tap density of the first carbon-based material is ≧0.8 g / cm 3 and optionally 0.8 g / cm 3 -1.20 g / cm 3When the tap density of the first carbon-based material is within the above range, the compression density of the negative electrode film layer can be improved, the energy density of the secondary battery can be improved, a reasonable pore structure can be formed between the particles of the negative electrode film layer, the transport performance of active ions and electrons can be improved, and it is advantageous for further improving the kinetic performance of the secondary battery.

[0033] In any embodiment of the present application, the powder compression density of the first carbon-based material at a pressing force of 5000 kg is ≤ 2.10 g / cm 3 and optionally 1.85 g / cm 3 -2.10 g / cm 3 When the powder compression density of the first carbon-based material is within the above range, the compression density of the negative electrode film layer can be improved, the energy density of the secondary battery can be improved, a reasonable pore structure can be formed between the particles of the negative electrode film layer, the transport performance of active ions and electrons can be improved, and it is advantageous for further improving the kinetic performance of the secondary battery.

[0034] In any embodiment of the present application, the interlayer distance of the crystal plane of the first carbon-based material 002 is ≤ 0.335916 nm, and optionally 0.335576 nm - 0.335916 nm. When the interlayer distance of the first carbon-based material is within the above range, its gram capacity becomes higher, which is advantageous for improving the energy density of the secondary battery.

[0035] In any embodiment of the present application, the gram capacity of the first carbon-based material is ≥ 358 mAh / g, and optionally 358 mAh / g - 370 mAh / g. When the gram capacity of the first carbon-based material is within the above range, the energy density of the secondary battery can be improved.

[0036] In any embodiment of the present application, the X-ray diffraction pattern of the first carbon-based material has a diffraction peak of the 3R phase 101 crystal plane. When the first carbon-based material has a diffraction peak of the 3R phase 101 crystal plane, many active sites exist on the surface of the first carbon-based material particles, and the transport of active ions can be accelerated.

[0037] In any embodiment of the present application, the X-ray diffraction pattern of the first carbon-based material does not have a diffraction peak of the 012 crystal plane of the 3R phase. When the first carbon-based material does not have a diffraction peak of the 012 crystal plane of the 3R phase, the internal defects thereof are reduced, the consumption of active ions is reduced, and the initial Coulomb efficiency and storage performance of the secondary battery can be improved.

[0038] In any embodiment of the present application, in the thermogravimetric analysis test of the first carbon-based material under an air atmosphere, the weight loss rate of the first carbon-based material between 35°C and 790°C is ≤50%, and optionally 16% - 43%. The first carbon-based material has a small weight loss rate between 35°C and 790°C, and at this time has fewer surface defects and / or bulk phase defects, reduces the consumption of active ions due to the formation of the SEI film, and reduces the consumption of active ions during the storage process of the secondary battery, so the storage performance of the secondary battery can be improved.

[0039] In any embodiment of the present application, in the thermogravimetric analysis test of the first carbon-based material under an air atmosphere, the temperature corresponding to the maximum weight loss rate of the first carbon-based material is T max Then, T max is 795°C or higher, and optionally 805°C - 850°C. The first carbon-based material has a temperature T max corresponding to a high maximum weight loss rate, and at this time has good thermal stability and low reaction activity, reduces the consumption of active ions due to the formation of the SEI film, and reduces the consumption of active ions during the storage process of the secondary battery, so the storage performance of the secondary battery can be improved.

[0040] In any embodiment of the present application, the mass ratio of the first carbon-based material in the negative electrode active material is ≥30 wt%, and optionally 30 wt% - 80 wt%. When the content of the first carbon-based material is within the above range, the energy density of the secondary battery can be improved, and the secondary battery can be given good kinetic performance.

[0041] In any embodiment of the present application, the volume distribution particle size Dv50 of the negative electrode active material is ≧6 μm, and optionally 6 μm - 23 μm. When the volume distribution particle size Dv50 of the negative electrode active material is within the above range, it is advantageous for improving the transport performance of active ions and electrons, so that the kinetic performance of the secondary battery can be further improved. In addition, the occurrence of side reactions can be further reduced, and the storage performance of the secondary battery can also be improved.

[0042] In any embodiment of the present application, the particle size distribution (Dv90 - Dv10) / Dv50 of the negative electrode active material is ≧0.9, and optionally 0.9 - 1.55. When the particle size distribution (Dv90 - Dv10) / Dv50 of the negative electrode active material is within the above range, its particle deposition performance is good, which is advantageous for improving the compression density of the negative electrode film layer, so that the energy density of the secondary battery can be further improved. In addition, it is also advantageous for forming a reasonable pore structure between the particles of the negative electrode film layer and improving the kinetic performance of the secondary battery.

[0043] In any embodiment of the present application, the graphitization degree of the negative electrode active material is 92% or more, and optionally 92% - 96%. By adjusting the graphitization degree of the negative electrode active material within the above range, it is advantageous for the negative electrode active material to have a high gram capacity and good active ion transport performance, so it is advantageous for the secondary battery to have both a high energy density and good kinetic performance.

[0044] In any embodiment of the present application, the gram capacity of the negative electrode active material is ≧350 mAh / g, and optionally 350 mAh / g - 365 mAh / g. By adjusting the gram capacity of the negative electrode active material within the above range, it is advantageous for improving the energy density of the secondary battery.

[0045] In any embodiment of the present application, the negative electrode film layer further contains a silicon-based material. The silicon-based material plays a role in improving the pore structure in the negative electrode film layer, facilitating the infiltration and liquid storage of the electrolyte, improving the kinetic performance of the secondary battery, and improving the negative electrode capacity, so that the energy density of the secondary battery can be further improved.

[0046] In any embodiment of the present application, the mass ratio of the silicon-based material in the negative electrode film layer is 20% or less. Thereby, while improving the kinetic performance and energy density of the secondary battery, it is possible to achieve both good cycle performance and storage performance in the secondary battery.

[0047] In any embodiment of the present application, the porosity of the negative electrode film layer is ≧15.5%, and optionally 15.5%-38%. Thereby, since it is advantageous for the negative electrode film layer to have both a high capacity and an appropriate pore structure, it is advantageous for the secondary battery to have both a high energy density and good storage performance and kinetic performance.

[0048] In any embodiment of the present application, the compression density of the negative electrode film layer is ≧1.40 g / cm 3 and optionally 1.40 g / cm 3 -1.80 g / cm 3 Thereby, it is advantageous for the negative electrode film layer to have both a high capacity and high transport performance of active ions and electrons, and further it is advantageous for the secondary battery to have both a high energy density and good storage performance and kinetic performance.

[0049] In any embodiment of the present application, the areal density of the negative electrode film layer is ≧5.5 g / cm 2 and optionally 6.0 g / cm 3 -19.5 g / cm 2 Thereby, it is advantageous for the negative electrode film layer to have both a high capacity and high transport performance of active ions and electrons, and further it is advantageous for the secondary battery to have both a high energy density and good storage performance and kinetic performance.

[0050] In any embodiment of the present application, the OI value of the negative electrode film layer is ≦38, and optionally 8-38. Thereby, it is advantageous for improving the insertion performance of active ions in the negative electrode film layer, the negative electrode film layer can also have a low thickness repulsion rate, and further it is advantageous for achieving both good storage performance and kinetic performance in the secondary battery.

[0051] The second aspect of the present application provides a power consumption device including the secondary battery of the first aspect of the present application.

[0052] Since the power consumption device of the present application includes the secondary battery of the present application, it has at least the same advantages as the secondary battery.

Brief Description of the Drawings

[0053] To more clearly explain the technical solutions of the embodiments of the present application, the drawings necessary for use in the embodiments of the present application are briefly described below. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can also obtain other drawings based on these drawings without creative efforts. In the drawings, they are not necessarily drawn to actual scale.

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Modes for Carrying Out the Invention

[0054] Hereinafter, embodiments specifically disclosing the secondary battery and the power consumption device of the present application will be described in detail with reference to the drawings as appropriate. However, detailed descriptions that are more than necessary may be omitted. For example, detailed descriptions of known matters or duplicate descriptions of actually the same structure may be omitted. This is to avoid the following description from becoming unnecessarily redundant and to facilitate the understanding of those skilled in the art. Furthermore, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0055] The "range" disclosed in the present application is limited in the form of a lower limit and an upper limit, and a predetermined range is limited by selecting the lower limit and the upper limit that define the boundary of the specific range. The range defined in this way may or may not include the end values, and any combination is possible, that is, it is possible to form one range by combining any lower limit value and any upper limit value. For example, when ranges of 60 - 120 and 80 - 110 are given for a specific parameter, it can be understood that ranges of 60 - 110 and 80 - 120 are also expected. Also, when the minimum range values are 1 and 2 and the maximum range values are 3, 4, and 5, ranges of 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5 are all expected. In the present application, unless otherwise specified, the range of "a - b" represents a shortened expression of any combination of real numbers between a and b. Here, both a and b are real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" are included in this specification, and "0 - 5" is a shortening of the combination of these numerical values. Also, when it is described that a certain parameter is an integer of 2 or more, it corresponds to the disclosure that the parameter is an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0056] Unless otherwise specified, all embodiments and selectable embodiments of the present application can be combined with each other to form a new technical solution, and such a technical solution should be regarded as being included in the disclosure content of the present application.

[0057] Unless otherwise specified, all technical features of this application and selectable technical features can be combined with each other to form a new technical solution, and such a technical solution should be regarded as being included in the disclosure content of this application.

[0058] Unless otherwise specified, all steps of this application may be performed sequentially, randomly, or preferably sequentially. For example, if the method includes steps (a) and (b), it indicates that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, when it is mentioned that the method may further include step (c), it indicates 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), and may also include steps (c), (a), and (b).

[0059] Unless otherwise specified, the terms "comprising", "having", and "including" described in this application are meant to be open-ended and may also be closed-ended. For example, the above "comprising", "having", and "including" can represent further "comprising", "having", and "including" other components not listed, or "comprising", "having", and "including" only the listed components.

[0060] Unless otherwise specified, the term "or" in this application is inclusive. For example, the phrase "A or B" represents "A, B, or both A and B". More specifically, any of the following conditions is satisfied: 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).

[0061] Unless otherwise specified, the terms used in this application have the meanings known to those skilled in the art.

[0062] Unless otherwise specified, the numerical values of the parameters mentioned in this application can be measured by various test methods commonly used in this field. For example, they can be measured according to the test methods provided in this application.

[0063] Unless otherwise specified, in this application, the term "active ion" refers to ions that can reciprocally insert and desorb between the positive electrode and the negative electrode of a secondary battery, including but not limited to lithium ions.

[0064] In this application, the terms "a plurality" and "a plurality of types" refer to two or more.

[0065] The inventors have found that in order to improve the kinetic performance of a secondary battery, particularly the rapid charging ability, it is important to improve the kinetic performance of the negative electrode. Currently, 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, as proven by many studies, the above methods for improving the negative electrode kinetics only improve the kinetic performance to a certain extent at the initial stage of battery charging and have no significant effect on improving the kinetic performance at the end stage of battery charging. The kinetic performance of the secondary battery cannot be effectively improved, and thus, a large-rate charge cannot actually be performed on the secondary battery. Also, the energy density of the secondary battery significantly decreases.

[0066] For example, when improving the energy density of a secondary battery by increasing the compression density of the negative electrode film layer, it often leads to deterioration of the kinetic performance of the secondary battery. Also, the electrolyte infiltration characteristics of the negative electrode film layer at a high compression density deteriorate, and the risk of crushing of the negative electrode active material particles increases, resulting in an increase in side reactions inside the battery and further affecting the storage performance of the secondary battery.

[0067] Therefore, it is difficult for current secondary batteries to achieve both high energy density and good kinetic performance and storage performance.

[0068] The inventors of the present invention have conducted further research and ingeniously improved the structure of the negative electrode film layer to solve the above problems.

[0069] Specifically, a first aspect of an embodiment of the present application provides a secondary battery.

[0070] The present application does not particularly limit the type of secondary battery. For example, the secondary battery may be a lithium-ion battery or the like. Generally, a secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and the like. During the charging and discharging processes of the secondary battery, active ions reciprocate between the positive electrode sheet and the negative electrode sheet for insertion and desorption, and the electrolyte serves to conduct the active ions between the positive electrode sheet and the negative electrode sheet. The present application does not particularly limit the type of the electrolyte, and it can 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 electrolytic solution). In a secondary battery using an electrolytic solution and a secondary battery using a solid electrolyte, a separator may be further included, which is provided between the positive electrode sheet and the negative electrode sheet and serves as an isolation function. [Negative electrode sheet]

[0071] 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 and containing a negative electrode active material. The negative electrode active material includes a first carbon-based material and a second carbon-based material. The first carbon-based material has a pore structure, and at least a part of the surface of the second carbon-based material has a carbon coating layer.

[0072] 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 (for example, a scanning electron microscope image at a magnification of 1000 times), that is, the pore structure in the raw material bulk structure for manufacturing the first carbon-based material is not completely filled.

[0073] The inventors of the present invention have discovered the following through research. When at least a part of the surface of the second carbon-based material has a carbon coating layer (for example, a coating layer containing amorphous carbon), its kinetic performance is good, which is advantageous for the rapid insertion and desorption of active ions. However, the gram capacity and compression density of the second carbon-based material decrease, which affects the compression density of the negative electrode film layer and the energy density of the secondary battery. The first carbon-based material has a pore structure, its compression density is large, which can improve the compression density of the negative electrode film layer and the energy density of the secondary battery. At the same time, the pore structure can ensure the expansion space required for the volume change of the particles, reduce the risk of the generation of new interfaces due to particle crushing, and reduce the occurrence of side reactions.

[0074] The inventors of the present invention have found through intensive research the following. When the negative electrode active material in the negative electrode film layer contains both the first carbon-based material and the second carbon-based material, the first carbon-based material has a pore structure, and at least a part of the surface of the second carbon-based material has a carbon coating layer, the characteristics of the high capacity and high compression density of the first carbon-based material and the good kinetic characteristics of the second carbon-based material can be fully exerted. As a result, the negative electrode sheet can have a high compression density, a low volume change, and a high active ion transfer performance. Furthermore, the secondary battery using the negative electrode sheet can achieve both good kinetic performance and storage performance on the premise of having a high energy density.

[0075] In some embodiments, the interlayer distance of the crystal plane of the second carbon-based material 002 is larger than the interlayer distance of the crystal plane of the first carbon-based material 002. The larger interlayer distance of the second carbon-based material is advantageous for the rapid desorption of active ions, and the smaller interlayer distance of the first carbon-based material and the higher gram capacity. Therefore, adjusting the interlayer distance of the 002 crystal plane of the second carbon-based material to be larger than the interlayer distance of the 002 crystal plane of the first carbon-based material is advantageous for achieving both high energy density and good kinetic performance of the secondary battery.

[0076] In some embodiments, the gram capacity of the second carbon-based material is smaller than the gram capacity of the first carbon-based material. By combining and using a first carbon-based material having a high capacity and a second carbon-based material having a carbon coating layer, it is advantageous for achieving both a high energy density and good kinetic performance of the secondary battery.

[0077] In some embodiments, the powder compression density of the second carbon-based material at a pressing force of 5000 kg is smaller than the powder compression density of the first carbon-based material at a pressing force of 5000 kg. A high powder compression density of the first carbon-based material is advantageous for forming a good electron conduction network in the negative electrode film layer, and a small powder compression density of the second carbon-based material is advantageous for the negative electrode film layer having good electrolyte infiltration characteristics. Therefore, by combining and using a second carbon-based material having a low powder compression density and a first carbon-based material having a high powder compression density, it is advantageous for the negative electrode film layer to have a reasonable pore structure, for the negative electrode film layer to achieve both good active ion transport performance and electron transport performance, and further for the secondary battery to achieve both a high energy density and good cycle performance and kinetic performance.

[0078] In some embodiments, the peak intensity ratio I of the D peak and the G peak in the Raman spectrum of the second carbon-based material D / I G is greater than the peak intensity ratio I of the D peak and the G peak in the Raman spectrum of the first carbon-based material D / I G A large I of the second carbon-based material D / I G indicates that there are many surface active sites on the particles, which is advantageous for the rapid insertion and desorption of active ions. A small I of the first carbon-based material D / I G results in high surface stability of the particles and can reduce the occurrence of side reactions. Therefore, by making the I of the second carbon-based material D / I G greater than the I of the first carbon-based material D / I GBy adjusting it to be larger than that, it is advantageous for improving the surface stability of the entire negative electrode active material, reducing the occurrence of side reactions, and improving the storage performance. On the other hand, it is also advantageous for the secondary battery to have good kinetic performance.

[0079] In some embodiments, the second carbon-based material includes secondary particles. Optionally, the quantitative ratio of the secondary particles in the second carbon-based material is 50% or more, for example, 50%-95%, 60%-100%, 65%-85%, 70%-100%, 75%-90%, 75%-85%, 80%-100%, 80%-90%, 85%-95%, or 90%-100%. When the second carbon-based material contains an appropriate proportion of secondary particles, the active ion channels in the negative electrode film layer can be increased, and the insertion path of active ions can be shortened. Therefore, the kinetic performance of the secondary battery can be further improved, and polarization can be reduced and side reactions can be decreased. Thus, good storage performance of the secondary battery can also be achieved.

[0080] In some embodiments, all of the second carbon-based materials are secondary particles, that is, the quantitative ratio of the secondary particles in the second carbon-based material is 100%.

[0081] In the present application, the quantitative ratio of the secondary particles in the second carbon-based material means that any one test sample is selected in the negative electrode film layer, any plurality of test regions are taken from the test sample, images of the plurality of test regions are obtained using a scanning electron microscope, and the ratio of the number of the second carbon-based materials in the secondary particle form to the total number of the second carbon-based material particles in each image is statistically analyzed. The average value of the plurality of statistical results is the quantitative ratio of the secondary particles in the second carbon-based material.

[0082] In some embodiments, the peak intensity ratio I D / I G of the D peak and the G peak in the Raman spectrum of the second carbon-based material is ≧0.23, and optionally 0.23-0.41. The I D / I GBy adjusting within the above range, the active ion transport performance of the second carbon-based material is improved, which is beneficial to the improvement of the kinetic performance of the secondary battery.

[0083] In some embodiments, the powder compression density of the second carbon-based material at a pressing force of 5000 kg is ≧ 1.65 g / cm 3 and optionally 1.65 g / cm 3 -1.90 g / cm 3 By adjusting the powder compression density of the second carbon-based material within the above range, it is beneficial to form a reasonable pore structure between the particles of the negative electrode film layer. Therefore, it is beneficial for the secondary battery to have both high energy density and good kinetic performance.

[0084] In some embodiments, the interlayer distance of the crystal plane of the second carbon-based material 002 is ≦ 0.336217 nm, and optionally 0.335787 nm - 0.336217 nm. By adjusting the interlayer distance of the second carbon-based material within the above range, it is beneficial for the rapid insertion and desorption of active ions, so it is beneficial to improve the active ion transport performance of the negative electrode film layer. In addition, since the second carbon-based material can have high surface stability and high gram capacity, the occurrence of side reactions can be reduced. Therefore, the secondary battery can have both high energy density and good mechanical performance and storage performance.

[0085] In some embodiments, the specific surface area of the second carbon-based material is ≧ 0.90 m 2 / g, and optionally 0.9 m 2 / g - 2.5 m 2 / g, 0.95 m 2 / g - 2.45 m 2 / g. By adjusting the specific surface area of the second carbon-based material within the above range, it is beneficial for the rapid desorption of active ions, so the kinetic performance of the secondary battery can be further improved. In addition, it is beneficial to reduce the occurrence of side reactions and reduce the consumption of active ions due to the formation of the SEI film. Therefore, it is also beneficial for the secondary battery to have both high initial Coulomb efficiency and good cycle performance and storage performance.

[0086] In some embodiments, the volume distribution particle size Dv50 of the second carbon-based material is ≧ 10 μm, optionally 10 μm - 22 μm, and optionally 11.5 μm - 20.0 μm. When the volume distribution particle size Dv50 of the second carbon-based material is within the above range, the specific surface area of the second carbon-based material can be reduced, the occurrence of side reactions can be decreased, and the storage performance and / or cycle performance of the secondary battery can be improved. Also, since it is advantageous for improving the transport performance of active ions and electrons, the kinetic performance of the secondary battery can be further improved.

[0087] In some embodiments, the particle size distribution (Dv90 - Dv10) / Dv50 of the second carbon-based material is ≦ 1.65, optionally 0.9 - 1.65. When the particle size distribution (Dv90 - Dv10) / Dv50 of the second carbon-based material is within the above range, its particle deposition performance is good, which is advantageous for improving the compression density of the negative electrode film layer and the energy density of the secondary battery. Also, it is advantageous for forming a reasonable pore structure between the particles of the negative electrode film layer, improving the transport performance of active ions and electrons, and further improving the kinetic performance of the secondary battery.

[0088] In some embodiments, the tap density of the second carbon-based material is ≧ 0.85 g / cm 3 and optionally 0.85 g / cm 3 - 1.25 g / cm 3 , 0.9 g / cm 3 - 1.25 g / cm 3 When the tap density of the second carbon-based material is within the above range, the compression density of the negative electrode film layer can be improved, and the energy density of the secondary battery can be improved. Also, it is advantageous for forming a reasonable pore structure between the particles of the negative electrode film layer, improving the transport performance of active ions and electrons, and further improving the kinetic performance of the secondary battery.

[0089] In some embodiments, the gram capacity of the second carbon-based material is ≧340 mAh / g, and optionally 340 mAh / g - 360 mAh / g, 345 mAh / g - 360 mAh / g. By adjusting the gram capacity of the second carbon-based material within the above range, while improving the energy density of the secondary battery, the second carbon-based material can have good active ion transport performance, which is also beneficial to the improvement of the kinetic performance of the secondary battery.

[0090] In some embodiments, the second carbon-based material includes at least one of artificial graphite and natural graphite. Optionally, the second carbon-based material includes artificial graphite.

[0091] In some embodiments, more than 80% of the surface of the second carbon-based material is coated with a carbon coating layer. Optionally, 90% - 100% of the surface of the graphite is coated with a carbon coating layer.

[0092] In some embodiments, the carbon in the coating layer includes amorphous carbon, which is advantageous for the rapid insertion and desorption of active ions. The carbon may be obtained by carbonizing an organic carbon source. The organic carbon source can employ a carbon-containing material suitable for coating known in the art, and can include, for example, one or more of coal pitch, petroleum pitch, phenolic resin, coconut shell, etc.

[0093] In some embodiments, the second carbon-based material includes artificial graphite in the form of secondary particles, and has a carbon coating layer on at least a part of the surface of the artificial graphite. Optionally, the quantitative ratio of the artificial graphite in the form of secondary particles in the second carbon-based material is 50% or more, for example, 50% - 95%, 60% - 100%, 65% - 85%, 70% - 100%, 75% - 90%, 75% - 85%, 80% - 100%, 80% - 90%, 85% - 95%, or 90% - 100%.

[0094] In the present application, the quantitative ratio of artificial graphite in the form of secondary particles in the second carbon-based material means that one test sample is arbitrarily selected in the negative electrode film layer, a plurality of test regions are arbitrarily selected from the test sample, images of the plurality of test regions are acquired using a scanning electron microscope, and the ratio of the number of artificial graphite in the form of secondary particles to the total number of second carbon-based material particles in each image is statistically analyzed. The average value of the plurality of statistical results is the quantitative ratio of artificial graphite in the form of secondary particles in the second carbon-based material.

[0095] In some embodiments, the first carbon-based material includes one or more pore structures with a pore area of 0.1 μm 2 or more, and optionally includes one or more pore structures with a pore area of 0.12 μm 2 -2.5 μm 2 When the first carbon-based material includes a pore structure having the above pore area, the pore structure can ensure an expansion space necessary for the volume change of its particles. Thereby, the risk of generating a new interface due to particle crushing can be further reduced, the occurrence of side reactions can be further reduced, and the storage performance of the secondary battery can be improved.

[0096] In some embodiments, 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 a distance of 0.25L inside the particle, where L is the minor axis length of the first carbon-based material particle. Let the total pore area of the outer region be S 1 and the total pore area of the inner region be S 2 , and S 2 >S 1 is satisfied.

[0097] When the first carbon-based material has S 2 >S 1When further satisfied, the first carbon-based material further has the characteristics that the number of pores in the internal region is large and / or the pore size is large, while the number of pores in the external region is small and / or the pore size is small. The pore structure in the internal region of the first carbon-based material can ensure the expansion space required for the volume change of the particles, thereby reducing the risk of generating a new interface due to particle crushing, reducing the repulsion rate of the thickness of the negative electrode film layer, and further reducing the occurrence of side reactions. Since the number of pores in the external region of the first carbon-based material is small and / or the pore size is small, the first carbon-based material particles have a stable structure, and the electrolyte can be avoided from infiltrating into the pore structure inside the first carbon-based material particles as much as possible. Therefore, the occurrence of side reactions can be further reduced, and the consumption of active ions due to the formation of the SEI film inside the particles can be reduced. Therefore, when the first carbon-based material satisfies S 2 >S 1 by further satisfying, the initial Coulomb efficiency of the secondary battery can be improved, and the storage performance of the secondary battery can be further improved.

[0098] In some embodiments, 1.2 ≤ S 2 / S 1 ≤ 500, 1.5 ≤ S 2 / S 1 ≤ 500, 2 ≤ S 2 / S 1 ≤ 450, 2.2 ≤ S 2 / S 1 ≤ 400, 2.4 ≤ S 2 / S 1 ≤ 300, 2.5 ≤ S 2 / S 1 ≤ 250, 2.6 ≤ S 2 / S 1 ≤ 200, 2.8 ≤ S 2 / S 1 ≤ 150, 3.0 ≤ S 2 / S 1 ≤ 100. The inventors further found from research that when S 2 / S 1 satisfies being within the above range, the secondary battery can better balance high energy density and good storage performance.

[0099] In the present application, the total pore area S of the outer region of the first carbon-based material 1 and the total pore area S of the inner region 2 can be obtained by testing with a cross-sectional image of the first carbon-based material.

[0100] In the present application, the cross-sectional image of the first carbon-based material includes a cross-sectional image passing through the center of the particles of the first carbon-based material. The "particle center" refers to the range within a radius of 0.1 μm from the geometric center of the particle toward the particle surface.

[0101] In the present application, the minor axis length of the particle refers to the minimum value when the connecting line of two points on the surface of the particle passes through the geometric center of the particle.

[0102] FIG. 1 is a schematic diagram of a cross-sectional image of one of the particles of the first carbon-based material 100 of the present application, and the cross-sectional image passes through the particle center of the first carbon-based material 100. As shown in FIG. 1, L indicates the minor axis length of the particle of the first carbon-based material 100, and the region extending from the surface of the particle of the first carbon-based material 100 to the inside of the particle at a distance of 0.25L is the outer region 101, and the region inside the outer region 101 is the inner region 102.

[0103] The cross-section of the first carbon-based material can be prepared by using a cross-section polisher (for example, IB-09010 CP type argon ion cross-section polisher manufactured by JEOL, Japan). Then, referring to JY / T010-1996, the cross-section of the first carbon-based material is scanned by using a scanning electron microscope (for example, Sigma 300 type scanning electron microscope manufactured by ZEISS, Germany). Finally, by using image processing software (for example, AVIZO), the total pore area S of the outer region of the first carbon-based material 1 and the total pore area S of the inner region 2 are calculated.

[0104] In some embodiments, the short-axis length L of the first carbon-based material particles satisfies L≧4μm, and optionally, 4μm≦L≦25μm, 4μm≦L≦20μm, 6μm≦L≦20μm, 8μm≦L≦20μm, 8μm≦L≦18μm, 8μm≦L≦16μm.

[0105] In some embodiments, the area of the pore structure in the external region of the first carbon-based material is 0.15μm 2 or less, and optionally 0.13μm 2 or less. The inventors have found through further research that by controlling the area of the pore structure in the external region of the first carbon-based material within the above range, a dense structure can be provided in the external region of the first carbon-based material. Thereby, the structural stability of the first carbon-based material can be effectively improved, penetration of the electrolyte into the pore structure inside the first carbon-based material particles can be avoided as much as possible, and the storage performance of the secondary battery can be effectively improved. Of course, the present application does not limit that the area of all pore structures in the external region of the first carbon-based material is 0.15μm 2 or less. For example, it can be controlled to 95% or more, and optionally, the area of 99% or more of the pore structures is 0.15μm 2 or less.

[0106] In some embodiments, the internal region of the first carbon-based material includes one or more pore structures with an area of 0.15μm 2 or more, and optionally includes one or more pore structures with an area of 0.15μm 2 -2.0μm 2 or more. The inventors have found through further research that by including the pore structure of the above size in the internal region of the first carbon-based material, a sufficient and stable expansion space can be ensured for the volume change of the first carbon-based material particles, the risk of crushing of the first carbon-based material particles can be reduced, the occurrence of side reactions can be reduced, while the compression density of the negative electrode film layer can be improved.

[0107] In some embodiments, at least a part of the surface of the first carbon-based material has a carbon coating layer. Optionally, 80% or more of the surface of the first carbon-based material is coated with a carbon coating layer, and further, 90%-100% of the surface of the first carbon-based material is coated with a carbon coating layer.

[0108] In some embodiments, the carbon in the coating layer includes amorphous carbon and / or crystalline carbon with a graphitization degree of 68%-90%. Thereby, the kinetic performance of the secondary battery can be further improved.

[0109] In some embodiments, the first carbon-based material may not have a carbon coating layer. The first carbon-based material of the present application has a relatively stable surface. When it does not have a carbon coating layer on its surface, it maintains its low side reaction activity and is advantageous for reducing the occurrence of side reactions, so the cycle performance and / or storage performance of the secondary battery can be further improved.

[0110] In some embodiments, the first carbon-based material includes primary particles, and the quantitative ratio of the primary particles in the first carbon-based material is 50% or more, for example, 55%-95%, 60%-100%, 65%-90%, 65%-80%, 70%-100%, 75%-90%, 80%-100%, 90%-100%, or 95%-100%. When the first carbon-based material contains an appropriate ratio of primary particles, it has high structural stability and reduces the occurrence of side reactions, so it can improve the storage performance of the secondary battery. Also, since it improves the compression density of the negative electrode film layer, the energy density of the secondary battery can be improved.

[0111] In some embodiments, all of the first carbon-based materials may be primary particles, that is, the quantitative ratio of the primary particles in the first carbon-based material is 100%.

[0112] In the present application, the quantity ratio of primary particles in the first carbon-based material means that one test sample is arbitrarily selected in the negative electrode film layer, a plurality of test regions are arbitrarily selected from the test sample, images of the plurality of test regions are acquired using a scanning electron microscope, and the ratio of the number of the first carbon-based material in the primary particle form to the total number of the first carbon-based material particles in each image is statistically analyzed. The average value of the plurality of statistical results is the quantity ratio of primary particles in the first carbon-based material.

[0113] In some embodiments, the specific surface area of the first carbon-based material is ≤ 2.3 m 2 and optionally 0.7 m 2 / g - 2.3 m 2 / g, 0.7 m 2 / g - 2.1 m 2 / g, 0.7 m 2 / g - 1.8 m 2 / g, 0.7 m 2 / g - 1.7 m 2 / g, 0.7 m 2 / g - 1.6 m 2 / g, 0.7 m 2 / g - 1.5 m 2 / g, 0.7 m 2 / g - 1.4 m 2 / g, 0.7 m 2 / g - 1.3 m 2 / g, 0.7 m 2 / g - 1.25 m 2 / g. Since the first carbon-based material has a low specific surface area, it can reduce the consumption of active ions due to the formation of the SEI film, reduce the occurrence of side reactions, and improve the initial Coulomb efficiency and storage performance of the secondary battery.

[0114] In some embodiments, the volume distribution particle size Dv50 of the first carbon-based material is ≥ 6.0 μm and optionally 6.0 μm - 25.0 μm.

[0115] In some embodiments, the volume distribution particle size Dv90 of the first carbon-based material is ≥ 16.0 μm and optionally 16.0 μm - 40.0 μm.

[0116] When the volume distribution particle sizes Dv50 and / or Dv90 of the first carbon-based material are within the above ranges, it is advantageous for improving the transport performance of active ions and electrons, so that the kinetic performance of the secondary battery can be improved. Also, the specific surface area of the first carbon-based material can be reduced, the occurrence of side reactions can be decreased, and the storage performance of the secondary battery can also be improved.

[0117] In some embodiments, the particle size distribution (Dv90 - Dv10) / Dv50 of the first carbon-based material is ≦ 1.55, and optionally 0.9 - 1.55. When the particle size distribution (Dv90 - Dv10) / Dv50 of the first carbon-based material is within the above range, its particle deposition performance is good, which is advantageous for improving the compression density of the negative electrode film layer and the energy density of the secondary battery. Also, it is advantageous for forming a reasonable pore structure between the particles of the negative electrode film layer, improving the transport performance of active ions and electrons, and improving the kinetic performance of the secondary battery.

[0118] In some embodiments, the tap density of the first carbon-based material is ≧ 0.8 g / cm 3 and optionally 0.8 g / cm 3 - 1.20 g / cm 3 When the tap density of the first carbon-based material is within the above range, the compression density of the negative electrode film layer can be improved, and the energy density of the secondary battery can be improved. Also, it is advantageous for forming a reasonable pore structure between the particles of the negative electrode film layer, improving the transport performance of active ions and electrons, and further improving the kinetic performance of the secondary battery.

[0119] In some embodiments, the powder compression density of the first carbon-based material under a pressing force of 5000 kg is ≦ 2.10 g / cm 3 and optionally 1.85 g / cm 3 - 2.10 g / cm 3 When the powder compression density of the first carbon-based material is within the above range, the compression density of the negative electrode film layer can be improved, and the energy density of the secondary battery can be improved. Also, it is advantageous for forming a reasonable pore structure between the particles of the negative electrode film layer, improving the transport performance of active ions and electrons, and further improving the kinetic performance of the secondary battery.

[0120] In some embodiments, the interlayer distance of the crystal plane of the first carbon-based material 002 is ≦ 0.335916 nm, and optionally 0.335576 nm - 0.335916 nm. When the interlayer distance of the first carbon-based material is within the above range, its gram capacity becomes higher, which is advantageous for improving the energy density of the secondary battery.

[0121] In some embodiments, the gram capacity of the first carbon-based material is ≧ 358 mAh / g, and optionally 358 mAh / g - 370 mAh / g. When the gram capacity of the first carbon-based material is within the above range, the energy density of the secondary battery can be improved.

[0122] In some embodiments, the X-ray diffraction pattern of the first carbon-based material has a diffraction peak of the 3R phase 101 crystal plane.

[0123] In some embodiments, the X-ray diffraction pattern of the first carbon-based material does not have a diffraction peak of the 3R phase 012 crystal plane. In the X-ray diffraction pattern of the first carbon-based material, the 2θ of the diffraction peak of the 3R phase 101 crystal plane is in the range of 43° - 44°, and the 2θ of the diffraction peak of the 3R phase 012 crystal plane is in the range of 46° - 47°.

[0124] The crystalline carbon of the 3R (Rhombohedral) phase is rhombohedral crystalline carbon and has a stacking structure of ABCABC···, and the crystalline carbon of the 2H (Hexagonal) phase is hexagonal crystalline carbon and has a stacking structure of ABAB···.

[0125] The inventors have found the following in the research process. When the first carbon-based material has a diffraction peak of the 3R phase 101 crystal plane, many active sites exist on the surface of the first carbon-based material particles, and the transport of active ions can be accelerated. When the first carbon-based material does not have a diffraction peak of the 3R phase 012 crystal plane, the internal defects are reduced, the consumption of active ions is reduced, and the initial Coulomb efficiency and storage performance of the secondary battery can be improved.

[0126] In some embodiments, in the thermogravimetric analysis test of the first carbon-based material in an air atmosphere, the weight loss rate of the first carbon-based material between 35°C and 790°C is ≤50%, and optionally 10%-50%, 16%-43%. The first carbon-based material has a relatively small weight loss rate between 35°C and 790°C. At this time, it has fewer surface defects and / or bulk phase defects, reduces the consumption of active ions due to the formation of the SEI film, and reduces the consumption of active ions during the storage process of the secondary battery. Therefore, the storage performance of the secondary battery can be improved.

[0127] In some embodiments, in the thermogravimetric analysis test of the first carbon-based material under an air atmosphere, let the temperature corresponding to the maximum weight loss rate of the first carbon-based material be T max Then, T max is 795°C or higher, and optionally 800°C - 855°C, 805°C - 850°C. The first carbon-based material has a temperature T max corresponding to a high maximum weight loss rate. At this time, it has good thermal stability and low reaction activity, reduces the consumption of active ions due to the formation of the SEI film, and reduces the consumption of active ions during the storage process of the secondary battery. Therefore, the storage performance of the secondary battery can be improved.

[0128] The thermogravimetric analysis (TG) test of the first carbon-based material can be carried out with reference to JY / T 014-1996. This application may also be carried out under the following conditions. That is, the weighed mass of the sample is 10 ± 0.05 mg, air is used as the purge gas, the gas flow rate is 60 mL / min, the heating rate is 5°C / min, and the test temperature range is 35°C - 950°C. The test equipment may be a NETZSCH STA 449F3 type simultaneous thermal analyzer of NETZSCH Company in Germany. The temperature T max corresponding to the maximum weight loss rate of the first carbon-based material is the peak temperature of the thermogravimetric differential curve of the first carbon-based material.

[0129] In some embodiments, the mass ratio of the first carbon-based material in the negative electrode active material is ≧30 wt% (30 wt% or more), and optionally 30 wt% - 80 wt%. When the content of the first carbon-based material is within the above range, the energy density of the secondary battery can be improved, and the secondary battery can be given good kinetic performance.

[0130] In some embodiments, the volume distribution particle size Dv50 of the negative electrode active material is ≧6 μm, and optionally 6 μm - 23 μm. By adjusting parameters such as the volume distribution particle size, particle size distribution, and mass content of the first carbon-based material and / or the second carbon-based material, the volume distribution particle size of the negative electrode active material can be made within the above range. When the volume distribution particle size Dv50 of the negative electrode active material is within the above range, it is advantageous for improving the transport performance of active ions and electrons, so the kinetic performance of the secondary battery can be further improved. In addition, the occurrence of side reactions can be reduced, and the storage performance of the secondary battery can also be improved.

[0131] In some embodiments, the particle size distribution (Dv90 - Dv10) / Dv50 of the negative electrode active material is ≧0.9 (0.9 or more), and optionally 0.9 - 1.55. By adjusting parameters such as the volume distribution particle size, particle size distribution, and mass content of the first carbon-based material and / or the second carbon-based material, the particle size distribution of the negative electrode active material can be made within the above range. When the particle size distribution (Dv90 - Dv10) / Dv50 of the negative electrode active material is within the above range, its particle deposition performance is good, which is advantageous for improving the compression density of the negative electrode film layer, so the energy density of the secondary battery can be further improved. In addition, it is also advantageous for forming a reasonable pore structure between the particles of the negative electrode film layer and improving the kinetic performance of the secondary battery.

[0132] In some embodiments, the graphitization degree of the negative electrode active material is 92% or more, and optionally 92% - 96%. By adjusting parameters such as the graphitization degree and mass content of the first carbon-based material and / or the second carbon-based material, the graphitization degree of the negative electrode active material can be within the above range. By adjusting the graphitization degree of the negative electrode active material within the above range, it is advantageous for the negative electrode active material to have a high gram capacity and good active ion transport performance, so it is advantageous for the secondary battery to have both a high energy density and good kinetic performance.

[0133] In some embodiments, the gram capacity of the negative electrode active material is ≥ 350 mAh / g, and optionally 350 mAh / g - 365 mAh / g. By adjusting parameters such as the gram capacity and mass content of the first carbon-based material and / or the second carbon-based material, the gram capacity of the negative electrode active material can be within the above range. By adjusting the gram capacity of the negative electrode active material within the above range, it is advantageous for improving the energy density of the secondary battery.

[0134] In some embodiments, the negative electrode film layer may further include other negative electrode active materials known in the art other than the above first carbon-based material and the second silicon-based material. For example, the negative electrode film layer may further include a silicon-based material. The silicon-based material can play a role in improving the pore structure in the negative electrode film layer, facilitating the infiltration and liquid storage of the electrolyte, improving the kinetic performance of the secondary battery, and improving the negative electrode capacity, thereby further improving the energy density of the secondary battery. Optionally, the silicon-based material may include one or more of silicon monomer, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material.

[0135] In some embodiments, when the negative electrode film layer further contains a silicon-based material, the mass ratio of the silicon-based material in the negative electrode film layer is 20% or less, and for example, it may be 1% - 20%, 1% - 15%, 1% - 10%, 1.5% - 8%, 2% - 6%, or 3% - 7%. Thereby, while improving the kinetic performance and energy density of the secondary battery, it is possible to achieve both good cycle performance and storage performance in the secondary battery.

[0136] In some embodiments, the negative electrode film layer may optionally further contain a negative electrode conductive agent. In the present application, the type of the negative electrode conductive agent is not particularly limited. As an 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.

[0137] In some embodiments, the negative electrode film layer may optionally further contain a negative electrode adhesive. In the present application, the type of the negative electrode adhesive is not particularly limited. As an example, the negative electrode adhesive may include one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic resin (for example, polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0138] In some embodiments, the negative electrode film layer may optionally further contain other auxiliaries. As an example, the other auxiliaries may include a thickener, for example, sodium carboxymethyl cellulose (CMC), PTC thermistor material, and the like.

[0139] In some embodiments, the negative electrode current collector can be a metal foil sheet or a composite current collector. As an example of the metal foil sheet, a copper foil can be used. The composite current collector can include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0140] The negative electrode film layer is usually formed by applying a negative electrode slurry to a negative electrode current collector, drying, and cold pressing. The negative electrode slurry is usually formed by dispersing a negative electrode active material, an optional conductive agent, an optional adhesive, an optional other auxiliary agent, etc. in a solvent and uniformly stirring. The solvent may be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.

[0141] The negative electrode sheet does not exclude other additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode sheet according to the present application further includes a conductive undercoat layer (for example, composed of a conductive agent and an adhesive) sandwiched between the negative electrode current collector and the negative electrode film layer and provided on the surface of the negative electrode current collector. 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.

[0142] In some embodiments, the porosity of the negative electrode film layer is ≧15.5%, and optionally 15.5%-38%. This is advantageous for the negative electrode film layer to have both high capacity and an appropriate pore structure, and is advantageous for the secondary battery to have both high energy density and good storage performance and kinetic performance.

[0143] In some embodiments, the compression density of the negative electrode film layer is ≧1.40 g / cm 3 and optionally 1.40 g / cm3 -1.80 g / cm 3 This makes it advantageous for the negative electrode film layer to achieve both high capacity and high transport performance of active ions and electrons, and further makes it advantageous for the secondary battery to achieve both high energy density and good storage performance and kinetic performance.

[0144] In some embodiments, the areal density of the negative electrode film layer is ≧5.5 g / cm 2 and, optionally, 6.0 g / cm 3 -19.5 g / cm 2 This makes it advantageous for the negative electrode film layer to achieve both high capacity and high transport performance of active ions and electrons, and further makes it advantageous for the secondary battery to achieve both high energy density and good storage performance and kinetic performance.

[0145] In some embodiments, the OI value of the negative electrode film layer is ≦38, and optionally 8 - 38. This is advantageous for improving the active ion insertion performance of the negative electrode film layer, and the negative electrode film layer can also have a low thickness repulsion rate, and further is advantageous for achieving both good storage performance and kinetic performance of the secondary battery.

[0146] The negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode film layer is provided on either one or both of the two opposing surfaces of the negative electrode current collector. It should be noted that each parameter of the negative electrode film layer provided in the present application (such as compression density, areal density, porosity, OI value, etc.) refers to the parameter of the negative electrode film layer on one side of the negative electrode current collector. When the negative electrode film layer is provided on both sides of the negative electrode current collector, if the parameter of the negative electrode film layer on either side meets the requirements of the present application, it is considered to be within the protection scope of the present application.

[0147] In the present application, the specific surface area of a material (for example, the first carbon-based material, the second carbon-based material, etc.) has the meaning known in the art and can be measured by devices and methods known in the art. For example, referring to GB / T 19587-2017, it can be tested by the nitrogen gas adsorption specific surface area analysis test method and calculated by the BET (Brunauer Emmett Teller) method. The test device may be a Tri-Star 3020 specific surface area and pore size analyzer manufactured by Micromeritics, USA.

[0148] In the present application, whether a coating layer exists on the surface of a material (for example, the first carbon-based material, the second carbon-based material, etc.) can be determined by a transmission electron microscope.

[0149] In the present application, the interlayer distance of the (002) crystal plane of a material (for example, the first carbon-based material, the second carbon-based material) has the meaning known in the art and can be tested by devices and methods known in the art. For example, it can be tested using an X-ray diffractometer (for example, Bruker D8 Discover). The test can refer to JIS K 0131-1996 and JB / T 4220-2011 to obtain the interlayer distance of the C(002) crystal plane in the crystal structure of the material.

[0150] In the present application, the graphitization degree of the negative electrode active material has the meaning known in the art and can be tested by devices and methods known in the art. For example, it can be tested using an X-ray diffractometer (for example, Bruker D8 Discover). The test refers to JIS K 0131-1996 and JB / T 4220-2011 to obtain the average interlayer distance d of the C(002) crystal plane in the crystal structure of the material. 002 After that, the graphitization degree can be calculated based on the formula g = (0.344 - d 002 ) / (0.344 - 0.3354) × 100%. In the above formula, d 002 is the average interlayer distance of the C(002) crystal plane in the crystal structure of the material expressed in nanometers (nm).

[0151] In this application, the volume distribution particle sizes Dv10, Dv50, and Dv90 of a material (such as a first carbon-based material, a second carbon-based material, a negative electrode active material, etc.) have the meanings known in this field, and respectively indicate the particle sizes corresponding when the cumulative volume distribution percentage of the material reaches 10%, 50%, and 90%, and can be measured by devices and methods known in this field. For example, referring to GB / T 19077-2016, it can be measured using a laser particle size analyzer. The test device may be a Mastersizer 3000 type laser particle size analyzer of Malvern Panalytical Limited, UK.

[0152] In this application, the powder compression density of a material (such as a first carbon-based material, a second carbon-based material, etc.) has the meaning known in this field and can be measured by devices and methods known in this field. For example, referring to GB / T24533-2009, it can be measured by an electronic pressure tester (such as a UTM7305 type electronic pressure tester). An exemplary test method is to weigh 1 g of sample powder, put it into a mold with a bottom area of 1.327 cm 2 , apply a pressure of 5000 kg, keep the pressure for 30 s, then release the pressure, keep it for 10 s, and then record and calculate the powder compression density of the material at a press force of 5000 kg.

[0153] In this application, the tap density of a material (such as a first carbon-based material, a second carbon-based material, etc.) has the meaning known in this field and can be measured by devices and methods known in this field. For example, referring to GB / T5162-2006, it can be measured using a powder tap density tester. The test device can adopt Dandong Baite BT-301, and the test parameters are a vibration frequency of 250 ± 15 times / min, an amplitude of 3 ± 0.2 mm, a vibration number of 5000 times, and a graduated cylinder of 25 mL.

[0154] In this application, the I D / I G can be tested using a Raman spectrometer. I D is the Raman spectrum of the material at 1350 ± 50 cm -1represents the D peak intensity in, and I G represents the G peak intensity in the Raman spectrum of the material at 1580 ± 50 cm -1 . The test conditions are as follows: the excitation wavelength is 532 nm, the diffraction grating has 600 lines, the objective lens has a magnification of 50 times, the integration time is 10 s, the number of accumulations is 3 times, and the surface is scanned to obtain the D peak and G peak intensities at 100 points. The I D / I G is calculated, and the maximum and minimum 30 I D / I G are removed, and the average value of the remaining 40 points is the I D / I G of the material. As the test equipment, a Horiba LabRAM HR800 Raman spectrometer can be used.

[0155] In the present application, both the primary particles and the secondary particles have the meanings known in the art. The primary particles refer to non-aggregated particles. The secondary particles refer to aggregated particles in which two or more primary particles are aggregated. The primary particles and the secondary particles can be distinguished using a scanning electron microscope (SEM) image.

[0156] In the present application, the gram capacity of a material (for example, the first carbon-based material, the second carbon-based material, the negative electrode active material, etc.) (also referred to as the capacity per gram) has the meaning known in the art and can be tested by a method known in the art. An exemplary test method is to uniformly mix sample powder, carbon black (Super P) as a conductive agent, and polyvinylidene fluoride (PVDF) as an adhesive in a mass ratio of 91.6:1.8:6.6 with N-methylpyrrolidone (NMP) as a solvent to produce a slurry, apply the produced slurry to the surface of a copper foil as a negative electrode current collector, and dry it in an oven for preparation. After mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 1:1:1 to obtain an organic solvent, LiPF 6Dissolve it in the above organic solvent to prepare an electrolyte solution with a concentration of 1 mol / L. Then, using a lithium metal sheet as the counter electrode and a polyethylene (PE) thin film as the separator, assemble a CR2430 coin cell in a glove box protected by the above electrolyte solution and argon gas. After allowing the obtained coin cell to stand for 12 h, at 25 °C, perform a constant current discharge from 0.05 C to 0.005 V, allow it to stand for 10 min, perform a constant current discharge from 50 μA to 0.005 V, allow it to stand for 10 min, and discharge at a constant current of 10 μA to 0.005 V. Then, charge at a constant current of 0.1 C to 2 V and record the charge capacity. The ratio of the charge capacity to the mass of the sample is the gram capacity of the corresponding material (for example, the first carbon-based material, the second carbon-based material, the negative electrode active material, etc.).

[0157] In the present application, the areal density of the negative electrode film layer has the meaning known in the art and can be tested by methods known in the art. For example, select a negative electrode sheet coated on one side and cold-pressed (if it is a negative electrode sheet coated on both sides, the negative electrode film layer on one side can be wiped off first), and punch it into a small disc with an area of S 1 and record its weight as M 1 . Then, wipe off the negative electrode film layer of the weighed negative electrode sheet, weigh the weight of the negative electrode current collector, and record it as M 0 . Areal density of the negative electrode sheet = (M 1 - M 0 ) / S 1 .

[0158] In the present application, the compression density of the negative electrode film layer has the meaning known in the art and can be tested by methods known in the art. Compression density of the negative electrode film layer = areal density of the negative electrode film layer / thickness of the negative electrode film layer. The thickness of the negative electrode film layer has the meaning known in the art and can be tested using methods known in the art. For example, use a micrometer (for example, Mitutoyo 293 - 100 type, accuracy 0.1 μm).

[0159] In the present application, the porosity of the negative electrode film layer has the meaning known in the art and can be measured by methods known in the art. An exemplary test method is to take a negative electrode sheet coated on one side and cold-pressed (if it is a negative electrode sheet coated on both sides, first wipe off the negative electrode film layer on one side), punch it into small disc samples of a certain area, and measure the apparent volume V of the negative electrode sheet 1 Calculate 1 , refer to GB / T 24586-2009, adopt the gas displacement method with an inert gas (such as helium gas or nitrogen gas) as the medium, and use a true density tester to test the true volume V of the negative electrode sheet 2 . The porosity of the negative electrode film layer = (V 1 - V 2 ) / V 1 ×100%. Test samples of multiple (for example, 30) negative electrode sheets with good appearance and no powder falling off at the edges, and take the average value of the results to improve the accuracy of the test results. As the test equipment, a Micromeritics AccuPyc II 1340 type true density tester can be used.

[0160] In the present application, the OI value of the negative electrode film layer has the meaning known in the art and can be tested by equipment and methods known in the art. For example, it can be tested using an X-ray diffractometer (such as a Bruker D8 Discover). The test refers to JIS K 0131-1996 and JB / T 4220-2011 to obtain the X-ray diffraction pattern of the negative electrode sheet. The OI value = I 004 / I 110 to calculate the OI value of the negative electrode film layer. I 004 is the integrated area of the diffraction peak of the 004 crystal plane of crystalline carbon in the negative electrode film layer, and I 110 is the integrated area of the diffraction peak of the 110 crystal plane of crystalline carbon in the negative electrode film layer.

[0161] 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 λ = 1.5418 Å, the scanning 2θ angle range is 20° - 80°, and the scanning speed is 4° / min.

[0162] In addition, the tests of various parameters for the above-mentioned negative electrode active material or negative electrode film layer can be sampled and tested from a secondary battery manufactured according to the following steps.

[0163] The secondary battery is discharged (for safety, generally the secondary battery is brought to a fully discharged state), after removing the secondary battery, the negative electrode sheet is taken out, and the negative electrode sheet is immersed in dimethyl carbonate for a certain period of time (for example, 2h - 10h), then the negative electrode sheet is taken out and dried at a certain temperature and time (for example, 60°C, 4h or more), and the negative electrode sheet is taken out after drying. In this case, it is possible to sample from the dried negative electrode sheet and test various parameters related to the above-mentioned negative electrode film layer, such as the areal density, compression density, porosity, OI value, etc. of the negative electrode film layer.

[0164] The above-mentioned dried negative electrode sheet is fired at a certain temperature and time (for example, 400°C, 2h or more), in any one region of the fired negative electrode sheet, the negative electrode active material is sampled (it may be sampled by scraping the powder with a blade), the collected negative electrode active material is sieved (for example, sieved with a 200-mesh sieve), and finally a sample for testing the parameters of each of the above-mentioned negative electrode active materials is obtained.

[0165] In the present application, the above-mentioned first active material and second active material are commercially available or can be manufactured by the following method of the present application.

[0166] In some embodiments, the manufacturing method of the first carbon-based material includes step 1 of providing a raw material having a plurality of pore structures, step 2 of uniformly mixing the raw material and a filler at a predetermined ratio, and then holding at a first temperature T 1 for a first time t 1 and after completion, cooling to room temperature to obtain an intermediate, step 3 of holding the obtained intermediate at a second temperature T 2 for a second time t 2 and after completion, obtaining the first carbon-based material.

[0167] In some embodiments, in step 1, the raw material for manufacturing the first carbon-based material includes natural graphite. Optionally, the natural graphite includes one or more of flake graphite, natural spherical graphite, and microcrystalline graphite, and more optionally includes natural spherical graphite.

[0168] "Natural spherical graphite" means natural graphite having a spherical or quasi-spherical shape, and does not control all natural graphite particles into ideal spheres. In some embodiments, by performing pretreatment on flake graphite, natural spherical graphite with a desired particle size and morphology can be obtained. Optionally, the pretreatment includes processes such as crushing, classification, spheroidization, and purification.

[0169] In some embodiments, in step 1, the volume distribution particle size Dv50 of the raw material may be 6.0 μm - 25.0 μm.

[0170] In some embodiments, in step 1, the specific surface area of the raw material may be ≧ 2.5 m 2 / g, and optionally 2.5 m 2 / g - 10.0 m 2 / g. When the specific surface area of the raw material is within the above range, it is advantageous for subsequent filling treatment 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 Coulomb efficiency. It is also advantageous for the first carbon-based material to have better kinetic performance.

[0171] In some embodiments, in step 2, the softening point temperature of the filler is 90°C - 150°C. Optionally, the softening point temperature of the filler is 94°C - 146°C, 94°C - 142°C, 94°C - 138°C, 94°C - 134°C, 94°C - 130°C, 104°C - 146°C, 104°C - 142°C, 104°C - 138°C, 104°C - 134°C, 104°C - 130°C.

[0172] In some embodiments, in step 2, the volume distribution particle size Dv50 of the filler is 6 μm or less, and can be optionally 1 μm - 6 μm, 1 μm - 5 μm, 2 μm - 5 μm, 3 μm - 5 μm. Thereby, it is advantageous for the filler to be filled into the pore structure of the raw material after melting by heat, and it is also advantageous to improve the dispersion uniformity between the filler and the raw material.

[0173] In some embodiments, in step 2, the coking value of the filler is 15% - 40%, and can be optionally 18% - 34%. In the present application, the coking value of the filler is a meaning known in the art and can be measured by equipment and methods known in the art. For example, it can be measured with reference to GB / T 8727 - 2008.

[0174] In some embodiments, in step 2, the filler includes one or more of coal pitch, petroleum pitch, polymer compounds, and resins, and can be optionally one or more of coal pitch and petroleum pitch.

[0175] In some embodiments, in step 2, the mass ratio of the filler to the raw material is (10 - 40):100, and can be optionally (10 - 32):100, (10 - 30):100, (10 - 25):100, (10 - 20):100, (12 - 30):100, (14 - 28):100, (15 - 25):100.

[0176] In step 2, by adjusting one or more parameters such as the type, softening point, coking value, addition amount, etc. of the filler within the above ranges, it is advantageous to adjust the number and / or size of pores in the external region and internal region of the first carbon - based material within an appropriate range, and to adjust S 2 / S 1 within an appropriate range.

[0177] By adjusting parameters such as the type of filler, softening point, coking value, and addition amount within the above ranges, after the filler melts due to heat, its viscosity is not high, it maintains good fluidity, it is difficult for raw material particles to adhere, and the aggregation of raw material particles in subsequent manufacturing processes can be reduced. As a result, problems such as an increase in surface defects of the first carbon-based material particles and an increase in surfactant sites due to the need to increase the depolymerization process can also be reduced.

[0178] In some embodiments, in step 2, after uniformly mixing the raw material and the filling material at a predetermined ratio, the heating process of heating to the first temperature T 1 may be a stepwise heating process.

[0179] In some embodiments, the stepwise heating process includes a first heating process, a second heating process, and a third heating process.

[0180] In some embodiments, the first heating process heats up to 200°C - 250°C and holds the temperature at this range for 0.5 h - 3 h.

[0181] In some embodiments, the second heating process heats up to 450°C - 550°C and holds the temperature at this range for 0 h - 2 h. When the holding time is 0 h, it means that no heat preservation treatment is performed when heating within the range of 450°C - 550°C, and continue to heat up to the first temperature T 1 until reaching.

[0182] In some embodiments, the third heating process heats up to the first temperature T 1 and holds the temperature at this range for the first time t 1 for heat preservation.

[0183] In the stepwise heating process, first heat up to 200°C - 250°C. Since the heating temperature is higher than the softening point temperature of the filler, at this time, the filler melts and softens due to heat, and can be kept warm for 0.5h - 3h to allow it to flow and fill the pore structure of the raw material. Then, heat up to 450°C - 550°C. At this time, the melted and softened filler undergoes a carbonization reaction and gradually becomes in a semi-coke state, turning into a viscous liquid or solid, thereby avoiding the filler from entering all the pore structures of the raw material. Finally, heat up to the first temperature, and at this time, the filler undergoes a carbonization reaction, thereby effectively filling the pore structures occupied by the filler.

[0184] In some embodiments, in step 2, heat up to the first temperature T at a rate of 1°C / min - 10°C / min. 1 For example, the heating rate may be in the range consisting of 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 numerical value above. Optionally, the heating rate is 1.5°C / min - 8°C / min, 1.5°C / min - 6°C / min, 2°C / min - 6°C / min, 2°C / min - 5°C / min.

[0185] In some embodiments, the heating rate of the first heating process may be 1°C / min - 10°C / min, and optionally, may be 1.5°C / min - 8°C / min, 1.5°C / min - 6°C / min, 2°C / min - 6°C / min, 2°C / min - 5°C / min.

[0186] In some embodiments, the heating rate of the second heating process may be 1°C / min - 10°C / min, and optionally, may be 2°C / min - 8°C / min.

[0187] In some embodiments, the heating rate of the third heating process may be 1°C / min - 10°C / min, and optionally, may be 2°C / min - 8°C / min.

[0188] In some embodiments, in step 2, the first temperature T 1 is 700 °C - 1200 °C. For example, the first temperature T 1 may be in the range consisting of any value such as 700 °C, 750 °C, 800 °C, 850 °C, 900 °C, 950 °C, 1000 °C, 1050 °C, 1100 °C, 1200 °C or more. Optionally, the first temperature T 1 is 750 °C - 1100 °C, 800 °C - 1100 °C, 850 °C - 1100 °C, 900 °C - 1100 °C, 850 °C - 1000 °C.

[0189] In some embodiments, in step 2, the first time t 1 is 1 h - 5 h. For example, the first time t 1 may be in the range consisting of any value such as 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h or more. Optionally, the first time t 1 is 2 h - 4 h.

[0190] In some embodiments, in step 2, the heat treatment can be carried out in equipment capable of performing programmed temperature increase such as an intermediate frequency furnace, a roller hearth kiln, a rotary kiln, a pusher hearth kiln, a vertical granulation kettle, a horizontal granulation kettle, a vertical reaction kettle, a horizontal reaction kettle or a drum furnace.

[0191] In some embodiments, in step 2, the heat treatment atmosphere may be a protective gas atmosphere. The protective gas may include one or more of nitrogen gas, argon gas, and helium gas.

[0192] In step 2, by adjusting one or more of the heating rate, the first temperature, the first time, the heating process, etc. within the above range, it is advantageous to adjust the number and / or size of the pores in the external region and the internal region of the first carbon-based material within an appropriate range, and further it is advantageous to adjust the S 2 / S 1 of the first carbon-based material within an appropriate range.

[0193] In some embodiments, in step 3, the second temperature T 2 is 2070°C - 2700°C. Optionally, the second temperature T 2 is 2070°C - 2570°C, 2070°C - 2510°C, 2070°C - 2450°C, 2070°C - 2360°C, 2140°C - 2570°C, 2140°C - 2510°C, 2140°C - 2450°C, 2140°C - 2360°C.

[0194] In some embodiments, in step 3, the second time t 2 is 1.5 h - 6 h. For example, the second time t 2 may be in the range consisting of 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h, 6 h or any numerical value above. Optionally, the second time t 2 is 2 h - 5 h.

[0195] In some embodiments, in step 3, the heat treatment 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 series graphitization furnace.

[0196] In some embodiments, in step 3, the intermediate frequency furnace, continuous graphitization heat treatment atmosphere may be a protective gas atmosphere. The protective gas may include one or more of nitrogen gas, argon gas, and helium gas.

[0197] In step 3, by adjusting one or more of the second temperature and the second time within the above range, it is advantageous to adjust the content of amorphous 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 degree of graphitization, interlayer distance, and I D / I G etc.

[0198] In the method for manufacturing the first carbon-based material, by adjusting one or more of the parameters of natural graphite, the parameters of the filler, the heating rate, the first temperature, the first time, the heating process, the second temperature, the second time, etc. within the above ranges, the S of the first carbon-based material 2 / S 1 、I D / I G 、parameters such as graphitization degree, gram capacity, specific surface area, particle size, powder compression density, tap density, weight loss rate, etc. are advantageously adjusted.

[0199] In some embodiments, the method for manufacturing the second carbon-based material includes performing carbonization treatment after mixing a raw material and an organic carbon source to form a carbon coating layer on at least a part of the surface of the particles, and obtaining a second carbon-based material after completion. The raw material includes at least one of artificial graphite and natural graphite, and optionally includes artificial graphite.

[0200] In some embodiments, the organic carbon source can employ a carbon-containing material suitable for coatings known in the art, and can include, for example, one or more of coal pitch, petroleum pitch, phenolic resin, coconut shell, etc.

[0201] In some embodiments, the carbonization temperature is 900°C - 1300°C.

[0202] In the method for manufacturing the second carbon-based material, by adjusting one or more parameters among the parameters of the raw material (such as particle size, specific surface area, particle size distribution, gram capacity, etc.), the addition amount of the organic carbon source, the carbonization temperature, the carbonization time, etc., the I of the second carbon-based material D / I G 、parameters such as graphitization degree, interlayer distance, gram capacity, particle size, specific surface area, powder compression density, tap density, etc. are advantageously adjusted. [Positive electrode sheet]

[0203] 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 its own thickness direction, and the positive electrode film layer is provided on either one or both of the two opposing surfaces of the positive electrode current collector.

[0204] The positive electrode current collector can use a metal foil sheet or a composite current collector. As an example of the metal foil sheet, an aluminum foil can be used. The composite current collector can include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0205] The positive electrode film layer usually includes a positive electrode active material, an optional adhesive, and an optional conductive agent. The positive electrode film layer is usually formed by applying a positive electrode slurry to the positive electrode current collector, drying, and cold pressing. The positive electrode slurry is usually formed by dispersing a positive electrode active material, an optional conductive agent, an optional adhesive, and optional other components in a solvent and stirring uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP). As an example, the adhesive used in the positive electrode film layer may include any one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a terpolymer of vinylidene fluoride-tetrafluoroethylene-propylene, a terpolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, a copolymer of tetrafluoroethylene-hexafluoropropylene, and a fluorine-containing acrylate resin. As an example, the conductive agent used in the positive electrode film layer includes any one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0206] The positive electrode active material can employ a positive electrode active material for secondary batteries known in the art.

[0207] When the secondary battery of the present application is a lithium ion battery, the positive electrode active material includes, but is not limited to, one or more of lithium-containing transition metal oxides, lithium-containing phosphates, and their modified compounds. Examples of the lithium transition metal oxides include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds. Examples of the lithium-containing phosphates include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite material of lithium manganese iron phosphate and carbon, and their modified compounds.

[0208] 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 represented by the general formula Li a Ni b Co c M d O e A f and their modified compounds. 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.

[0209] 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 Co 1 / 3 Mn 1 / 3 O2 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811), LiNi 0.80 Co 0.15 Al 0.05 O 2 , LiFePO 4 and LiMnPO 4 may include one or more of them.

[0210] In the present application, the modified compound of each of the above cathode active materials is obtained by performing doping modification and / or surface coating modification on the cathode active material. [Electrolyte]

[0211] In some embodiments, the electrolyte uses an electrolytic solution containing an electrolyte salt and a solvent.

[0212] The type of the electrolyte salt is not specifically limited and can be selected according to actual needs.

[0213] When the secondary battery of the present application is a lithium-ion battery, for example, the electrolyte salt is lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB) and lithium bis(oxalate) borate (LiBOB), lithium difluorophosphate (LiPO2 F 2 ) may include one or more of lithium difluorobisoxalate phosphate (LiDFOP) and lithium tetrafluorooxalate phosphate (LiTFOP).

[0214] The type of the solvent is not particularly limited and can be selected according to actual needs. In some embodiments, for example, the organic solvent may include one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0215] In some embodiments, the electrolyte may optionally further include an additive. For example, the additive may include a negative electrode film-forming additive, a positive electrode film-forming additive, and an additive that can improve certain performance of the secondary battery, such as an additive that improves the overcharge performance of the secondary battery, an additive that improves the high-temperature performance of the secondary battery, an additive that improves the low-temperature output performance of the secondary battery, and the like. [Separator]

[0216] In the present application, the type of the separator is not particularly limited, and any known porous structure separator having good chemical stability and mechanical stability can be selected.

[0217] In some embodiments, the material of the separator may include one or more of glass fiber, non-woven 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.

[0218] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet can be used to manufacture an electrode assembly by a winding process or a lamination process.

[0219] In some embodiments, the secondary battery may include an exterior. The exterior is used for sealing the above-described electrode assembly and electrolyte.

[0220] In some embodiments, the exterior may be a hard case such as a hard plastic case, an aluminum case, or a steel case. The exterior may also be a soft bag, such as a soft plastic bag. The material of the soft package may be one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0221] The shape of the secondary battery of the present application is not particularly limited and may be cylindrical, rectangular, or any other arbitrary shape. FIG. 2 shows a rectangular-structured secondary battery 5 as an example.

[0222] In some embodiments, as shown in FIG. 3, the exterior can include a case 51 and a cover plate 53. The case 51 includes a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose to form a storage chamber. The case 51 has an opening communicating with the storage chamber, and the bar plate 53 closes the opening so as to close the storage chamber. The positive electrode sheet, the negative electrode sheet, and the separator can form an electrode assembly 52 by a winding process or a lamination process. The electrode assembly 52 is packaged in the storage chamber. The electrolyte infiltrates the electrode assembly 52. The number of electrode assemblies 52 included in the secondary battery 5 can be one or more, and can be adjusted according to demand.

[0223] The manufacturing method of the secondary battery of the present application is well-known. In some embodiments, a secondary battery can be formed by assembling a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte. As an example, a positive electrode sheet, a separator, and a negative electrode sheet are formed into an electrode assembly by a winding process or a lamination process, the electrode assembly is placed in an exterior, and after drying, an electrolyte is injected, and through processes such as vacuum encapsulation, standing, formation, and shaping, a secondary battery can be obtained.

[0224] 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 plural, and the specific number may be adjusted according to the application and capacity of the battery module.

[0225] FIG. 4 is a schematic diagram of a battery module 4 as an example. As shown in FIG. 4, in the battery module 4, a plurality of 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. Further, the plurality of secondary batteries 5 may be fixed by fasteners.

[0226] Optionally, the battery module 4 further includes an external case having a storage space, and the plurality of secondary batteries 5 are stored in the storage space.

[0227] In some embodiments, the battery module may be assembled as a battery pack, and the number of battery modules included in the battery pack may be adjusted according to the use and capacity of the battery pack.

[0228] FIGS. 5 and 6 are schematic diagrams of a battery pack 1 as an example. As shown in FIGS. 5 and 6, the battery pack 1 may include a battery case and a plurality of battery modules 4 provided in the battery case. The battery case includes an upper case 2 and a lower case 3, and the upper case 2 covers the lower case 3 to form a sealed space for accommodating the battery module 4. The plurality of battery modules 4 may be arranged in the battery case in any manner.

[0229] Embodiments of the present application provide a power consumption device including at least one of a secondary battery, a battery module, or a battery pack of the present application. The secondary battery, battery module, or battery pack may be used as a power source of the power consumption device or as an energy storage means of the power consumption device. The power consumption device may be a mobile device (e.g., a mobile phone, 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.), a train, a ship, and a satellite, an energy storage system, etc., but is not limited thereto.

[0230] The power consumption device can select a secondary battery, a battery module, or a battery pack according to demand.

[0231] FIG. 7 is a schematic diagram of a power consumption device as an example. This power consumption device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. In order to meet the requirements of high output and high energy density of this power consumption device, a battery pack or a battery module can be adopted.

[0232] As another example, the power consumption device may be a mobile phone, a tablet computer, a notebook computer, or the like. This power consumption device is generally required to be thin, and a secondary battery can be adopted as a power source. Example

[0233] The following examples illustrate the content of the present application in more detail. However, these examples are merely illustrative, and it is obvious to those skilled in the art that various modifications and changes can be made within the scope of the disclosure of the present application. Unless otherwise specified, all parts, percentages, and ratio values described in the following examples are all based on mass standards. In addition, all reagents used in the examples may be commercially available or synthesized according to conventional methods, and can be used as they are without further treatment. Also, all devices used in the examples are commercially available.

[0234] In the following examples and comparative examples, the first carbon-based material can be produced by the following method of the present application.

[0235] In the following examples and comparative examples, except for using artificial graphite without a coating layer as the second carbon-based material in Comparative Example 3, all other second carbon-based materials are artificial graphite with a carbon coating layer, and all are commercially available.

[0236] The flaky graphite was mechanically pulverized, classified, spheroidized, and purified to obtain natural spherical graphite. After mixing the obtained natural spherical graphite and petroleum pitch, the mixed material was placed in a device capable of programmed heating, and stepwise heating heat treatment was performed. After completion, it was cooled to room temperature to obtain an intermediate. The obtained intermediate was placed in a graphitization furnace and heat-treated. After completion, it was demagnetized and sieved to obtain the first carbon-based material. In the above process, the S 2 / S 1 , interlayer distance, volume distribution particle size Dv50 and other parameters can be controlled according to the manufacturing process of the first carbon-based material mentioned in the present application so that they are within the ranges shown in Table 1.

[0237] S of the first carbon-based material 2 / S 1 is tested by the following method. After uniformly mixing the adhesive for sample preparation with the first carbon-based material powder, it is applied to a copper foil and dried at 60 °C for 30 min to prepare. The sample is cut into a size of 6 mm × 6 mm and attached to the sample stage of a CP type argon ion cross-section polisher, and the sample is cut using a plasma beam to obtain the 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 particles. As the test apparatus, an IB-09010 CP type argon ion cross-section polisher manufactured by JEOL Ltd. of Japan can be used. The cross-section of the first carbon-based material is scanned using a scanning electron microscope. The test can refer to JY / T010-1996. The test equipment may be a Sigma 300 type scanning electron microscope manufactured by ZEISS of Germany. A region extending from the particle surface to the particle interior of the first carbon-based material at a distance of 0.25L is defined as the external region, and the region inside the external region is defined as the internal region, where L represents the minor axis length of the particles of the first carbon-based material. Using image processing software, the total pore area S 1 of the outer region of the first carbon-based material and the total pore area S 2 of the inner region of the first carbon-based material are calculated. The image processing software may be AVIZO. The secondary batteries of Examples 1-29 and Comparative Examples 1-3 were all manufactured by the following method.

[0238] The negative electrode active material (a mixture of the first carbon-based material and the second carbon-based material, for details, refer to Table 1), carbon black (Super P) as the conductive agent, sodium carboxymethyl cellulose as the thickening agent, and styrene-butadiene rubber as the adhesive are sufficiently stirred and mixed in deionized water, which is an appropriate amount of solvent, at a weight ratio of 96.4:1:1.2:1.4 to form a negative electrode slurry. The negative electrode slurry is applied to both surfaces of a copper foil, which is the negative electrode current collector, dried, and cold-pressed to obtain a negative electrode sheet.

[0239] LiNi 0.5 Co 0.2 Mn 0.3 O 2(NCM523), carbon black (Super P) as the conductive agent, and polyvinylidene fluoride as the binder were mixed at a weight ratio of 96:2:2. An appropriate amount of NMP, the solvent, was added and stirred uniformly to obtain the positive electrode slurry. The positive electrode slurry was coated on both surfaces of an aluminum foil, which is the positive electrode current collector, dried, and cold-pressed to obtain the positive electrode sheet.

[0240] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed at a volume ratio of 1:1:1 to obtain an organic solvent. Then, LiPF 6 was dissolved in the above organic solvent to prepare an electrolyte solution with a concentration of 1 mol / L.

[0241] Using a polyethylene film as the separator, the positive electrode sheet and the negative electrode sheet manufactured above were arranged in order, with the separator positioned between the positive electrode sheet and the negative electrode sheet to perform the isolation function. Then, it was wound to obtain the electrode assembly. The electrode assembly was placed in the outer package, and after drying, the electrolyte solution was injected. Through processes such as vacuum sealing, standing, forming, and shaping, a secondary battery was obtained. Performance test (1) Test of the rapid charging performance of the secondary battery

[0242] At 25°C, the secondary battery was charged at a constant current of 0.33C to 4.3V, then charged at a constant voltage until the current reached 0.05C. After standing for 5 minutes, the secondary battery was discharged at a constant current of 0.33C to 2.8V, and its actual capacity was designated as C0.

[0243] Thereafter, the secondary battery is charged at a constant current in sequence at 1.0C0, 1.3C0, 1.5C0, 1.8C0, 2.0C0, 2.3C0, 2.5C0, 3.0C0 until the negative electrode cut-off potential of 4.3V or 0V (based on the one reached first), and after each charge completion, it is discharged at 1C0 until 2.8V. The negative electrode potential corresponding to when charging to 10%, 20%, 30%, …, 80% SOC (State of Charge) at different charging rates is recorded, and the charge rate - negative electrode potential curve at different SOC states is drawn. After linear fitting, the charging rate corresponding to when the negative electrode potential is 0V at different SOC states is obtained. This charging rate is the charging window at the corresponding SOC state, denoted as C10%SOC, C20%SOC, C30%SOC, C40%SOC, C50%SOC, C60%SOC, C70%SOC, C80%SOC respectively. Based on the formula (60 / C20%SOC + 60 / C30%SOC + 60 / C40%SOC + 60 / C50%SOC + 60 / C60%SOC + 60 / C70%SOC + 60 / C80%SOC) × 10% with the unit of min, the charging time T of the secondary battery from 10% SOC to 80% SOC (on the premise that lithium does not precipitate in the secondary battery) is calculated. The shorter the charging time, the better the kinetic performance of the secondary battery. (2) Test on the storage performance of the secondary battery

[0244] At 25°C, the secondary battery prepared above is charged at a constant current at 1C until 4.3V, and then charged at a constant voltage until the current reaches 0.05C. After standing for 5 minutes, the secondary battery is discharged at a constant current at 1C until 2.8V, and the discharge capacity at this time is recorded, which is the discharge capacity before storage.

[0245] At 25°C, the secondary battery manufactured above is charged at a constant current at 1C until 4.3V, and then charged at a constant voltage until the current reaches 0.05C. Thereafter, the secondary battery is placed in a constant temperature bath at 60°C and stored for 180 days. The capacity retention rate (%) of the secondary battery stored at 60°C for 180 days = discharge capacity after storage / discharge capacity before storage × 100%.

[0246] As can be seen from Table 1, the negative electrode active material in the negative electrode film layer simultaneously contains a first carbon-based material having a pore structure and a second carbon-based material having a carbon coating layer on at least a portion of its surface, so that the secondary battery can have both good kinetic performance and storage performance on the premise of having a high energy density.

[0247] Taking the test results of Example 1, Comparative Example 1, and Comparative Example 2 together, it can be seen that there is a synergistic effect between the first carbon-based material and the second carbon-based material, and the battery has a longer storage life under the premise of having a high energy density.

[0248] In Comparative Example 3, the second carbon-based material not having a carbon coating layer was used in combination with the first carbon-based material, and the dynamic performance and storage performance of the battery were both poor.

[0249] The present application is not limited to the above-mentioned embodiment. The above-mentioned embodiment is an example, and any configuration that has substantially the same technical idea as the technical scope of the present application and exhibits similar effects is included in the technical scope of the present application. In addition, various modifications to the embodiment that a person skilled in the art can conceive, and other forms constructed by combining some of the components in the embodiment, are also included in the scope of the present application, within the scope of the present application.

[0250] [Table 1] JPEG2025517147000003.jpg25245 [Explanation of symbols]

[0251] 1 Battery pack 2 Upper case 3 Lower housing 4 Battery Module 5 Secondary battery 51 cases 52 Electrode Assembly 53 Cover plate 100 First carbon-based material 101 External area 102 Inner region

Claims

1. A secondary battery including a negative electrode sheet, wherein 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 and containing a negative electrode active material, the negative electrode active material includes a first carbon-based material and a second carbon-based material, and the first carbon-based material has a pore structure and has a carbon coating layer on at least a part of the surface of the second carbon-based material, a secondary battery.

2. The secondary battery according to claim 1, wherein the interlayer distance of the crystal plane of the second carbon-based material 002 is larger than the interlayer distance of the crystal plane of the first carbon-based material 002.

3. The secondary battery according to claim 1 or 2, wherein the gram capacity of the second carbon-based material is smaller than the gram capacity of the first carbon-based material.

4. The secondary battery according to any one of claims 1-3, wherein the powder compression density of the second carbon-based material at a pressing force of 5000 kg is smaller than the powder compression density of the first carbon-based material at a pressing force of 5000 kg.

5. The peak intensity ratio I of the D peak and the G peak in the Raman spectrum of the second carbon-based material Ｄ / I Ｇ is greater than the peak intensity ratio I of the D peak and the G peak in the Raman spectrum of the first carbon-based material Ｄ / I Ｇ The secondary battery according to any one of claims 1 to 4

6. The secondary battery according to any one of claims 1-5, wherein the second carbon-based material includes secondary particles, and optionally, the quantitative ratio of the secondary particles in the second carbon-based material is 50% or more.

7. The secondary battery according to any one of claims 1-6, wherein the second carbon-based material satisfies at least one of the following conditions. (1) The peak intensity ratio I of the D peak to the G peak in the Raman spectrum of the second carbon-based material Ｄ / I Ｇ is ≧ 0.23, and optionally 0.23 - 0.

41. (2) The powder compression density of the second carbon-based material at a pressing force of 5000 kg is ≧ 1.65 g / cm ３ and optionally 1.65 g / cm ３ - 1.90 g / cm ３ is. (3) The interlayer distance of the crystal plane of the second carbon-based material 002 is ≤ 0.336217 nm, and optionally, it is 0.335787 nm - 0.336217 nm. (4) The specific surface area of the second carbon-based material is ≧ 0.90 m ２ / g, and optionally 0.9 m ２ / g - 2.5 m ２ / g. (5) The volume distribution particle size Dv50 of the second carbon-based material is ≥ 10 μm, and optionally, it is 10 μm - 22 μm. (6) The particle size distribution (Dv90 - Dv10) / Dv50 of the second carbon-based material is ≤ 1.65, and optionally, it is 0.9 - 1.

65. (7) The tap density of the second carbon-based material is ≧ 0.85 g / cm ３ and optionally 0.9 g / cm ３ - 1.25 g / cm ３ is. (8) The gram capacity of the second carbon-based material is ≥ 340 mAh / g, and optionally, it is 340 mAh / g - 360 mAh / g.

8. The secondary battery according to any one of claims 1-7, wherein the second carbon-based material includes at least one of artificial graphite and natural graphite, and optionally, the second carbon-based material includes artificial graphite.

9. The first carbon-based material includes one or more pore structures with a pore area of 0.1 μm ２ or more, and optionally includes one or more pore structures with a pore area of 0.12 μm ２ -2.5 μm ２ The secondary battery according to any one of claims 1-8, which includes one or more pore structures with a pore area of 0.12 μm

10. The first carbon-based material includes an external region and an internal region located inside the external region. The external region is a region extending from the particle surface to the particle interior of the first carbon-based material at a distance of 0.25L, where L is the minor axis length of the first carbon-based material particle. Let the total pore area of the external region be S １ and the total pore area of the internal region be S ２ . S ２ > S １ . Optionally, 1.5 ≤ S ２ / S １ ≤ 500, 2 ≤ S ２ / S １ ≤ 450. The secondary battery according to any one of claims 1-9

11. The area of the pore structure in the outer region of the first carbon-based material is 0.15 μm ２ or less, and optionally 0.13 μm ２ or less, and / or In the internal region of the first carbon-based material, there is at least one pore structure with an area of 0.15 μm ２ or more, and optionally, at least one pore structure with an area of 0.15 μm ２ -2.0 μm ２ The secondary battery according to claim 10, comprising.

12. The secondary battery according to any one of claims 1-11, wherein the first carbon-based material has a carbon coating layer on at least a part of its surface.

13. The first carbon-based material contains primary particles. Optionally, the quantitative ratio of the primary particles in the first carbon-based material is 50% or more. The secondary battery according to any one of claims 1 to 12.

14. The first carbon-based material satisfies at least one of the following conditions. The secondary battery according to any one of claims 1 to 13. (1) The specific surface area of the first carbon-based material is ≤ 2.3 m ２ and optionally 0.7 m ２ / g - 2.3 m ２ / g. (2) The volume distribution particle size Dv50 of the first carbon-based material is ≧ 6.0 μm, and optionally 6.0 μm - 25.0 μm. (3) The volume distribution particle size Dv90 of the first carbon-based material is ≧ 16.0 μm, and optionally 16.0 μm - 40.0 μm. (4) The particle size distribution (Dv90 - Dv10) / Dv50 of the first carbon-based material is ≦ 1.55, and optionally 0.9 - 1.

55. (5) The tap density of the first carbon-based material is ≧ 0.8 g / cm ３ and optionally 0.8 g / cm ３ - 1.20 g / cm ３ is. (6) The powder compression density of the first carbon-based material at a press force of 5000 kg is ≦ 2.10 g / cm ３ and is optionally 1.85 g / cm ３ - 2.10 g / cm ３ is. (7) The interlayer distance of the crystal plane of the first carbon-based material 002 is ≦ 0.335916 nm, and optionally 0.335576 nm - 0.335916 nm. (8) The gram capacity of the first carbon-based material is ≧ 358 mAh / g, and optionally 358 mAh / g - 370 mAh / g. (9) The X-ray diffraction pattern of the first carbon-based material has a diffraction peak of the 3R phase 101 crystal plane. (10) The X-ray diffraction pattern of the first carbon-based material does not have a diffraction peak of the 3R phase 012 crystal plane. (11) In the thermogravimetric analysis test of the first carbon-based material in an air atmosphere, the weight loss rate of the first carbon-based material between 35°C and 790°C is ≦ 50%, and optionally 16% - 43%. (12) In the thermogravimetric analysis test of the first carbon-based material in an air atmosphere, the temperature corresponding to the maximum weight loss rate of the first carbon-based material is T ｍａｘ Let it be, then T ｍａｘ is 795°C or higher, and optionally 805°C - 850°C.

15. The mass ratio of the negative electrode active material in the first carbon-based material is ≧ 30% by weight, and optionally 30% by weight - 80% by weight. The secondary battery according to any one of claims 1 to 14.

16. The negative electrode active material satisfies at least one of the following conditions. The secondary battery according to any one of claims 1 to 15. (1) The volume distribution particle size Dv50 of the negative electrode active material is ≧ 6 μm, and optionally 6 μm - 23 μm. (2) The particle size distribution (Dv90 - Dv10) / Dv50 of the negative electrode active material is ≧ 0.9, and optionally 0.9 - 1.

55. (3) The graphitization degree of the negative electrode active material is ≧ 92%, and optionally 92% - 96%. (4) The gram capacity of the negative electrode active material is ≧ 350 mAh / g, and optionally 350 mAh / g - 365 mAh / g.

17. The negative electrode film layer further contains a silicon-based material, and optionally, the mass ratio of the silicon-based material in the negative electrode film layer is 20% or less. The secondary battery according to any one of claims 1-16.

18. The negative electrode film layer satisfies at least one of the following conditions. The secondary battery according to any one of claims 1-17. (1) The porosity of the negative electrode film layer is ≧ 15.5%, and optionally 15.5% - 38%. (2) The compression density of the negative electrode film layer is ≥ 1.40 g / cm ３ and optionally 1.40 g / cm ３ - 1.80 g / cm ３ is. (3) The areal density of the negative electrode film layer is ≥ 5.5 g / cm ２ and optionally 6.0 g / cm ３ - 19.5 g / cm ２ is. (4) The OI value of the negative electrode film layer is ≦ 38, and optionally 8 - 38.

19. A power consumption device comprising the secondary battery according to any one of claims 1-18.

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