Secondary batteries and power consumption devices

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 more specifically relates to secondary batteries and power consumption devices. [Background technology]

[0002] In recent years, rechargeable batteries have been widely used in many fields, including energy storage and power systems such as hydroelectric, thermal, wind, and solar power plants, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. As the range of applications for rechargeable batteries expands, serious challenges have been raised regarding their performance. For example, rechargeable batteries are required to achieve a balance between various performance characteristics such as energy density, dynamic performance, and service life. However, a problem faced by conventional technology is that it is often difficult to improve the energy density of a rechargeable battery while simultaneously improving its dynamic performance. Furthermore, improving the energy density of a rechargeable battery often affects its dynamic performance and service life. [Overview of the project]

[0003] This invention was made in view of these problems, and its purpose is to provide a secondary battery and a power consumption device that can achieve both good dynamic performance and storage performance while having a high energy density.

[0004] A first aspect of the present application provides 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, the first carbon-based material having a porous structure and the second carbon-based material having a carbon coating layer on at least a portion of its surface.

[0005] Through diligent research, the inventors have discovered that by simultaneously containing a first carbon-based material and a second carbon-based material in the negative electrode film layer, with the first carbon-based material having a porous structure and at least a portion of the surface of the second carbon-based material having a carbon coating layer, the high capacity and high compressive density characteristics of the first carbon-based material and the good dynamic characteristics of the second carbon-based material can be fully utilized. As a result, the negative electrode sheet can have high compressive density, low volume change, and high active ion transfer performance. Furthermore, a secondary battery using the said negative electrode sheet can achieve both good dynamic performance and storage performance, assuming a high energy density.

[0006] In any embodiment of the present application, the interlayer distance of the crystal planes of the second carbon-based material 002 is greater than the interlayer distance of the crystal planes of the first carbon-based material 002. Making the interlayer distance of the 002 crystal planes of the second carbon-based material greater than the interlayer distance of the 002 crystal planes of the first carbon-based material is advantageous for achieving both high energy density and good dynamic performance in a 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 using a combination of a first carbon-based material having a high capacity and a second carbon-based material having a carbon coating layer, it is advantageous to achieve both high energy density and good dynamic performance in a secondary battery.

[0008] In any embodiment of the present application, the powder compressibility density of the second carbon-based material at a 5000 kg press force is lower than that of the first carbon-based material at a 5000 kg press force. By using a combination of a second carbon-based material having a low powder compressibility density and a first carbon-based material having a high powder compressibility density, it is advantageous for the negative electrode film layer to have a rational pore structure, for the negative electrode film layer to achieve both good active ion transport performance and electron transport performance, and further advantageous 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 to improve the surface stability of the entire negative electrode active material, reduce the occurrence of side reactions, and improve 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 contains 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, polarization can be reduced, side reactions can be reduced, and good storage performance of the secondary battery can also be achieved.

[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 at a pressing force of 5000 kg is ≧1.65 g / cm 3 and optionally 1.65 g / cm 3 -1.90 g / cm 3Therefore, adjusting the powder compression density of the second carbon-based material within the above range is advantageous for forming a rational pore structure between the particles of the negative electrode film layer. This is advantageous for secondary batteries to achieve both high energy density and good dynamic performance.

[0013] In any embodiment of the present application, the interlayer distance of the crystal planes of the second carbon-based material 002 is ≤0.336217 nm (0.336217 nm or less), and is selectably between 0.335787 nm and 0.336217 nm. Adjusting the interlayer distance of the second carbon-based material to within the above range is advantageous for the rapid insertion and removal of active ions, and is therefore advantageous for improving the active ion transport performance of the negative electrode film layer. Furthermore, the second carbon-based material can have high surface stability and high gram capacity, thus reducing the occurrence of side reactions.

[0014] In any embodiment of the present application, the specific surface area of ​​the second carbon-based material is ≥ 0.90 m². 2 It is / g, and 0.9m is selectable. 2 / g-2.5m 2 The value is / g. By adjusting the specific surface area of ​​the second carbon-based material to within the above range, it is advantageous for the rapid insertion and removal of active ions, thereby further improving the kinetic performance of secondary batteries. Furthermore, it is advantageous for reducing the occurrence of side reactions and the consumption of active ions due to the formation of SEI films, which is beneficial for secondary batteries to achieve both high initial Coulomb efficiency and good cycle performance and storage performance.

[0015] In any embodiment of the present application, the volume-distributed particle size Dv50 of the second carbon-based material is ≥10 μm and selectively between 10 μm and 22 μm. When the volume-distributed 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. Furthermore, since it is also advantageous for improving 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 is selectably between 0.9 and 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 compressive density of the negative electrode film layer and improving the energy density of the secondary battery. Furthermore, it is advantageous for forming a rational 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.

[0017] In any embodiment of the present application, the tap density of the second carbon-based material is ≥0.85 g / cm³ 3 Therefore, 0.9 g / cm³ is available as an option. 3 -1.25 g / cm³ 3 Therefore, if the tap density of the second carbon-based material is within the above range, the compressive density of the negative electrode film layer can be improved, thereby increasing the energy density of the secondary battery. Furthermore, it is advantageous to form a rational 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.

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

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

[0020] In any embodiment of the present application, the first carbon-based material is 0.1 μm 2 It includes one or more pore structures having the above pore area, and selectively includes 0.12 μm 2 -2.5μm 2The material includes one or more pore structures having the above-mentioned pore area. When the first carbon-based material includes pore structures having the above-mentioned pore area, the pore structures can secure the expansion space necessary for volume changes of the particles, thereby further reducing the risk of new interfaces being generated due to particle fragmentation, 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 outer region and an inner region located inside the outer region, wherein the outer region refers to a region extending from the surface of the particles of the first carbon-based material into the interior of the particles at a distance of 0.25 L, where L is the minor axis length of the particles of the first carbon-based material, the total pore area of ​​the outer region is represented as S1, and the total pore area of ​​the inner region is represented as S2, where S2 > S1. If the first carbon-based material further satisfies S2 > S1, 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 ≤ S2 / S1 ≤ 500, and optionally, 2 ≤ S2 / S1 ≤ 450. When S2 / S1 is within the above range, a better balance between high energy density and good storage performance of the secondary battery can be achieved.

[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 μm². 2 The following are available, with a selectable size of 0.13 μm. 2 The following is the result: By controlling the area of ​​the pore structure in the external region of the first carbon-based material to within the above range, a dense structure can be provided in the external region of the first carbon-based material. This effectively improves the structural stability of the first carbon-based material, minimizes penetration of the electrolyte into the internal pore structure of the first carbon-based material particles, and further effectively improves the storage performance of the secondary battery.

[0024] In any embodiment of the present application, the internal region of the first carbon-based material is 0.15 μm 2It includes one or more pore structures having the above area, and optionally, 0.15 μm 2 -2.0 μm 2 It includes one or more pore structures having the above area. By including pore structures of the above size in the internal region of the first carbon-based material, a sufficient and stable expansion space can be secured for volume changes of the first carbon-based material particles, reducing the risk of fragmentation of the first carbon-based material particles and reducing the occurrence of side reactions, while improving the compressive density of the negative electrode film layer.

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

[0026] In any embodiment of the present application, the first carbon-based material includes primary particles. Optionally, the quantity proportion of primary particles in the first carbon-based material is 50% or more. When the first carbon-based material contains an appropriate proportion of primary particles, it provides high structural stability and reduces the occurrence of side reactions, thereby improving the storage performance of the secondary battery. It also improves the compressive density of the negative electrode film layer, thereby improving the energy density of the secondary battery.

[0027] In any embodiment of the present application, the specific surface area of ​​the first carbon-based material is ≤2.3 m². 2 And, it is selectable to 0.7m 2 / g-2.3m 2 The value is / g. Because the first carbon-based material has a low specific surface area, it can reduce the consumption of active ions due to the formation of SEI films, reduce the occurrence of side reactions, and improve the initial Coulomb efficiency and storage performance of secondary batteries.

[0028] In any embodiment of the present application, the volume-distributed particle size Dv50 of the first carbon-based material is ≥6.0 μm and is selectably between 6.0 μm and 25.0 μm.

[0029] In any embodiment of the present application, the volume-distributed particle size Dv90 of the first carbon-based material is ≥16.0 μm and is selectably between 16.0 μm and 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, thereby improving the kinetic performance of the secondary battery. Furthermore, by further reducing the specific surface area of ​​the first carbon-based material, the occurrence of side reactions is reduced, 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 selectively between 0.9 and 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 compressive density of the negative electrode film layer and improving the energy density of the secondary battery. It is also advantageous for forming a rational 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 / cm³. 3 Therefore, 0.8 g / cm³ is available as a selectable option. 3 -1.20 g / cm³ 3 Therefore, when the tap density of the first carbon-based material is within the above range, it is possible to improve the compressive density of the negative electrode film layer, thereby improving the energy density of the secondary battery, forming a rational 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.

[0033] In any embodiment of the present application, the powder compression density of the first carbon-based material at a 5000 kg press force is ≤2.10 g / cm³. 3 And it is selectable at 1.85 g / cm³ 3 -2.10 g / cm³ 3 Therefore, when the powder compressibility density of the first carbon-based material is within the above range, it is possible to improve the compressibility density of the negative electrode film layer, thereby improving the energy density of the secondary battery, forming a rational 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.

[0034] In any embodiment of the present application, the interlayer distance of the crystal planes of the first carbon-based material 002 is ≤0.335916 nm and is selectively between 0.335576 nm and 0.335916 nm. When the interlayer distance of the first carbon-based material is within the above range, its gram capacity is 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 selectively between 358 mAh / g and 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 diffraction peaks on the 3R phase 101 crystal plane. When the first carbon-based material has diffraction peaks on the 3R phase 101 crystal plane, many active sites are present on the surface of the first carbon-based material particles, which can accelerate the transport of active ions.

[0037] In any embodiment of the present application, the X-ray diffraction pattern of the first carbon-based material does not have diffraction peaks on the 3R phase 012 crystal plane. When the first carbon-based material does not have diffraction peaks on the 3R phase 012 crystal plane, its 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.

[0038] In any embodiment of the present application, in a 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 selectively between 16% and 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, which 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, thereby improving the storage performance of the secondary battery.

[0039] In any embodiment of the present application, in a 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 set to T max Therefore, T max The temperature range is 795°C or higher, and is selectable between 805°C and 850°C. The first carbon-based material corresponds to a high maximum weight loss rate at temperature T. max This material possesses 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, thereby improving the storage performance of the secondary battery.

[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 is selectably between 30 wt% and 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 is selectably between 6 μm and 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, and thus 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 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 selectively between 0.9 and 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 compressive density of the negative electrode film layer, and thus further improving the energy density of the secondary battery. It is also advantageous for forming a rational pore structure between the particles of the negative electrode film layer, which improves the kinetic performance of the secondary battery.

[0043] In any embodiment of the present application, the degree of graphitization of the negative electrode active material is 92% or higher, and is selectably between 92% and 96%. Adjusting the degree of graphitization of the negative electrode active material within the above range is advantageous because it allows the negative electrode active material to have a high gram capacity and good active ion transport performance, thus advantageous for achieving both high energy density and good dynamic performance in a secondary battery.

[0044] In any embodiment of the present application, the gram capacity of the negative electrode active material is ≥350 mAh / g and is selectably between 350 mAh / g and 365 mAh / g. Adjusting the gram capacity of the negative electrode active material to within the above range 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 comprises a silicon-based material. The silicon-based material plays a role in improving the pore structure in the negative electrode film layer, facilitating electrolyte infiltration and liquid storage, improving the kinetic performance of the secondary battery, and improving the negative electrode capacity, thereby further increasing the energy density of the secondary battery.

[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. This makes it possible to improve the kinetic performance and energy density of the secondary battery while simultaneously achieving good cycle performance and storage performance.

[0047] In any embodiment of the present application, the porosity of the negative electrode film layer is ≥15.5%, and is selectably between 15.5% and 38%. This is advantageous for the negative electrode film layer to achieve both high capacity and an appropriate pore structure, and is therefore advantageous for the secondary battery to achieve both high energy density, good storage performance and dynamic performance.

[0048] In any embodiment of the present application, the compressive density of the negative electrode film layer is ≥1.40 g / cm³ 3 And it is selectable at 1.40 g / cm³ 3 -1.80 g / cm³ 3This is advantageous for the negative electrode film layer to achieve both high capacity and high active ion and electron transport performance, and further advantageous for the secondary battery to achieve both high energy density and good storage and dynamic performance.

[0049] In any embodiment of the present application, the surface density of the negative electrode film layer is ≥ 5.5 g / cm³ 2 And it is selectable at 6.0 g / cm³ 3 -19.5 g / cm³ 2 This is advantageous for the negative electrode film layer to achieve both high capacity and high active ion and electron transport performance, and further advantageous for the secondary battery to achieve both high energy density and good storage and dynamic performance.

[0050] In any embodiment of the present application, the OI value of the negative electrode film layer is ≤38 and selectably between 8 and 38. This is advantageous for improving the active ion insertion performance of the negative electrode film layer, allows the negative electrode film layer to have a low repulsion rate at a low thickness, and is also advantageous for achieving both good storage performance and kinetic performance of the secondary battery.

[0051] A second aspect of the present application provides a power consumption device including a secondary battery as described in the first aspect of the present application.

[0052] Since the power consumption device of the present invention is equipped with a secondary battery, it has at least the same advantages as a secondary battery. [Brief explanation of the drawing]

[0053] To more clearly illustrate the technical concept of the embodiments of this application, the drawings that need to be used in the embodiments of this application are briefly described below. Clearly, the drawings described below represent only a few embodiments of this application, and those skilled in the art can obtain other drawings based on these without any creative effort. The drawings are not necessarily drawn to actual scale. [Figure 1] This is a schematic diagram of a cross-sectional image of one of the particles of the first carbon-based material of the present invention. [Figure 2] This is a schematic diagram of one embodiment of the secondary battery of the present invention. [Figure 3] This is an exploded schematic diagram of one embodiment of the secondary battery of the present invention. [Figure 4] This is a schematic diagram of one embodiment of the battery module of the present invention. [Figure 5] This is a schematic diagram of one embodiment of the battery pack of the present invention. [Figure 6] Figure 5 is a schematic exploded view of an embodiment of the battery pack shown. [Figure 7] This is a schematic diagram of one embodiment of a power consumption device that includes a secondary battery of the present invention as a power source. [Modes for carrying out the invention]

[0054] Hereinafter, embodiments specifically disclosing the secondary battery and power consumption device of the present application will be described in detail, with reference to the drawings as appropriate. However, some unnecessary details may be omitted. For example, detailed explanations of known matters or redundant explanations of the same structure may be omitted. This is to avoid the following explanation becoming unnecessarily verbose and to facilitate understanding by those skilled in the art. Furthermore, the drawings and the following explanation are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0055] The “ranges” disclosed herein are limited in the form of lower and upper limits, and a given range is limited by selecting lower and upper limits that define the boundaries of a particular range. Such defined ranges may or may not include end values, and any combination is possible, that is, any lower limit and any upper limit can be combined to form a single range. For example, if the ranges 60-120 and 80-110 are given for a particular parameter, it can be understood that the ranges 60-110 and 80-120 are also expected. Also, if the minimum range values ​​are given as 1 and 2, and the maximum range values ​​are given as 3, 4, and 5, then the ranges 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5 are all expected. In this application, unless otherwise specified, the range “ab” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this specification, and "0-5" is an abbreviation for combinations of these numbers. Also, when a parameter is described as being 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 optional embodiments of this Application can be combined to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this Application.

[0057] Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical concepts, and such technical concepts should be considered to be included in the disclosures of this application.

[0058] Unless otherwise specified, all steps of this invention 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, if 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), or steps (a), (c), and (b), or steps (c), (a), and (b).

[0059] Unless otherwise specified, the terms "contains," "possesses," and "equip" as used in this application mean either open or closed. For example, the aforementioned "contains," "possesses," and "equips" may mean further "contains," "possesses," or "equips" other components not listed, or "contains," "possesses," or "equips" only the listed components.

[0060] Unless otherwise specified, the term "or" in this application is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0061] Unless otherwise specified, the terms used in this application have the meanings that are commonly understood by those skilled in the art.

[0062] Unless otherwise specified, the numerical values ​​of each parameter mentioned herein can be measured by various test methods commonly used in the art, for example, according to the test methods provided herein.

[0063] Unless otherwise specified, the term "active ion" in this application refers to an ion capable of reciprocal insertion and withdrawal between the positive and negative electrodes of a secondary battery, and includes, but is not limited to, lithium ions.

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

[0065] The inventors of this invention have found that improving the dynamic performance of the negative electrode is crucial for improving the dynamic performance of secondary batteries, particularly their rapid charging capability. Currently, negative electrode dynamic performance is often improved by reducing the coating weight of the negative electrode film layer or by reducing the compressive density of the negative electrode film layer. However, as many studies have shown, the above methods for improving negative electrode dynamics only improve the dynamic performance in the early stages of battery charging to a certain extent, and have no significant effect on improving the dynamic performance in the later stages of charging. As a result, the dynamic performance of secondary batteries cannot be effectively improved, and consequently, high-rate charging of secondary batteries is not possible. Furthermore, the energy density of the secondary battery is also significantly reduced.

[0066] For example, when increasing the energy density of a secondary battery by increasing the compressive density of the negative electrode film layer, it often leads to a deterioration in the kinetic performance of the secondary battery. Furthermore, the electrolyte penetration characteristics of the negative electrode film layer deteriorate at high compressive densities, and the risk of fragmentation of negative electrode active material particles increases, leading to 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 dynamic performance and storage capacity.

[0068] The inventors conducted further research and cleverly improved the structure of the negative electrode film layer, thereby solving the above problem.

[0069] Specifically, the first embodiment of the present invention provides a secondary battery.

[0070] This application does not particularly limit the type of secondary battery; for example, the secondary battery may be a lithium-ion battery. Typically, a secondary battery includes a positive electrode sheet, a negative electrode sheet, and an electrolyte. During the charging and discharging process of the secondary battery, active ions reciprocate between the positive electrode sheet and the negative electrode sheet for insertion and removal, and the electrolyte plays a role in conducting active ions between the positive electrode sheet and the negative electrode sheet. This application does not particularly limit the type of 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 electrolyte solution). A secondary battery using an electrolyte solution and a secondary battery using a solid electrolyte may further include a separator provided between the positive electrode sheet and the negative electrode sheet to serve as an isolation. [Negative electrode sheet]

[0071] The negative electrode sheet comprises 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, wherein the negative electrode active material comprises a first carbon-based material and a second carbon-based material, the first carbon-based material having a porous structure and the second carbon-based material having a carbon coating layer on at least a portion of its surface.

[0072] In this 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 1000x), 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 have discovered the following through their research: When at least a portion of the surface of a second carbon-based material has a carbon coating layer structure (e.g., a coating layer containing amorphous carbon), its kinetic performance is good and advantageous for the rapid insertion and removal of active ions. However, the gram capacity and compressible density of the second carbon-based material are reduced, affecting the compressible density of the negative electrode film layer and thus the energy density of the secondary battery. The first carbon-based material has a porous structure and a high compressible density, which can improve the compressible density of the negative electrode film layer and thus improve the energy density of the secondary battery. Furthermore, this porous structure can secure the expansion space necessary for volume changes of particles, reducing the risk of new interfaces being generated due to particle fragmentation and reducing the occurrence of side reactions.

[0074] The inventors have found the following through diligent research: By simultaneously containing a first carbon-based material and a second carbon-based material in the negative electrode film layer, with the first carbon-based material having a porous structure and the second carbon-based material having a carbon coating layer on at least a portion of its surface, the high capacity and high compressive density characteristics of the first carbon-based material and the good dynamic characteristics of the second carbon-based material can be fully exhibited. As a result, the negative electrode sheet can have high compressive density, low volume change, and high active ion transfer performance. Furthermore, a secondary battery using the negative electrode sheet can achieve both good dynamic performance and storage performance, assuming a high energy density.

[0075] In some embodiments, the interlayer distance of the crystal plane of the second carbon-based material 002 is greater 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, while the smaller interlayer distance of the first carbon-based material results in a higher gram capacity. Therefore, adjusting the interlayer distance of the 002 crystal plane of the second carbon-based material to be greater than that of the 002 crystal plane of the first carbon-based material is advantageous for achieving both high energy density and good dynamic performance in secondary batteries.

[0076] In some embodiments, the gram capacity of the second carbon-based material is smaller than that of the first carbon-based material. Combining a first carbon-based material with high capacity with a second carbon-based material having a carbon coating layer is advantageous for achieving both high energy density and good dynamic performance in secondary batteries.

[0077] In some embodiments, the powder compression density of the second carbon-based material at a 5000 kg press force is lower than that of the first carbon-based material at a 5000 kg press force. The high powder compression density of the first carbon-based material is advantageous for the anode film layer to form a good electron conduction network, while the low powder compression density of the second carbon-based material is advantageous for the anode film layer to have good electrolyte penetration characteristics. Therefore, by using a combination of a second carbon-based material with a low powder compression density and a first carbon-based material with a high powder compression density, it is advantageous for the anode film layer to have a rational pore structure, for the anode film layer to achieve both good active ion transport performance and electron transport performance, and further advantageous for the secondary battery to achieve both high energy density and good cycle performance and dynamic performance.

[0078] In some examples, the peak intensity ratio of the D peak to the G peak in the Raman spectrum of the second carbon-based material is D / I G This is the peak intensity ratio I of the D peak and G peak in the Raman spectrum of the first carbon-based material. D / I G Larger than. I of second carbon-based materials D / I G A large size indicates a large number of surface active sites in the particles, which is advantageous for the rapid insertion and removal of active ions, and is the I of first carbon-based materials. D / I G The small size of the particle surface stability increases, reducing the occurrence of side reactions. Therefore, the I of the second carbon-based material D / I G The first carbon-based material D / I GBy adjusting the setting to a greater extent, it is advantageous to improve the overall surface stability of the negative electrode active material, reduce the occurrence of side reactions, and improve storage performance, while also being advantageous for the secondary battery to achieve good kinetic performance.

[0079] In some embodiments, the second carbon-based material includes secondary particles, and the quantitative ratio of the secondary particles in the second carbon-based material is selectable to be 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 number of active ion channels in the negative electrode film layer can be increased and the insertion path of active ions can be shortened, thereby further improving the kinetic performance of the secondary battery. Furthermore, polarization can be reduced and side reactions can be decreased, thus enabling good storage performance for the secondary battery.

[0080] In some embodiments, the second carbon-based material consists of secondary particles, meaning that the quantity ratio of secondary particles in the second carbon-based material is 100%.

[0081] In this application, the quantity ratio of secondary particles in the second carbon-based material is determined by selecting any one test sample in the negative electrode film layer, taking any multiple test areas from the test sample, acquiring images of the multiple test areas using a scanning electron microscope, statistically calculating the ratio of the number of second carbon-based material particles in secondary particle form to the total number of second carbon-based material particles in each image, and averaging the results of multiple statistical calculations.

[0082] In some examples, the peak intensity ratio of the D peak to the G peak in the Raman spectrum of the second carbon-based material is D / I G The value is ≥0.23 and is selectably between 0.23 and 0.41. For the second carbon-based material, I D / I GBy adjusting the value within the above range, the active ion transport performance of the second carbon-based material is improved, which is advantageous for improving the dynamic performance of secondary batteries.

[0083] In some examples, the powder compression density of the second carbon-based material at a 5000 kg press force was ≥ 1.65 g / cm³. 3 And it is selectable at 1.65 g / cm³ 3 -1.90 g / cm³ 3 Therefore, by adjusting the powder compression density of the second carbon-based material within the above range, it is advantageous to form a rational pore structure between the particles of the negative electrode film layer, which is advantageous for secondary batteries to achieve both high energy density and good dynamic performance.

[0084] In some embodiments, the interlayer distance of the crystal plane of the second carbon-based material 002 is ≤0.336217 nm, and is selectably between 0.335787 nm and 0.336217 nm. Adjusting the interlayer distance of the second carbon-based material within the above range is advantageous for the rapid insertion and removal of active ions, thus improving the active ion transport performance of the negative electrode film layer. Furthermore, the second carbon-based material can have high surface stability and high gram capacity, thereby reducing the occurrence of side reactions. Consequently, the secondary battery can achieve both high energy density and good mechanical and storage performance.

[0085] In some embodiments, the specific surface area of ​​the second carbon-based material is ≥ 0.90 m². 2 It is / g, and 0.9m is selectable. 2 / g-2.5m 2 / g, 0.95m 2 / g-2.45m 2 The value is / g. By adjusting the specific surface area of ​​the second carbon-based material to within the above range, it is advantageous for the rapid desorption of active ions, thereby further improving the kinetic performance of the secondary battery. Furthermore, it is advantageous for reducing the occurrence of side reactions and the consumption of active ions due to the formation of the SEI film, which is beneficial for the secondary battery to achieve both high initial Coulomb efficiency and good cycle performance and storage performance.

[0086] In some embodiments, the volume-distributed particle size Dv50 of the second carbon-based material is ≥10 μm, selectively between 10 μm and 22 μm, and selectively between 11.5 μm and 20.0 μm. When the volume-distributed 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. Furthermore, since it is also 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 and selectively between 0.9 and 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 compressive density of the negative electrode film layer and the energy density of the secondary battery. Furthermore, it is advantageous for forming a rational 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 examples, the tap density of the second carbon-based material is ≥0.85 g / cm³. 3 And it is selectable at 0.85 g / cm³ 3 -1.25 g / cm³ 3 , 0.9 g / cm³ 3 -1.25 g / cm³ 3 Therefore, if the tap density of the second carbon-based material is within the above range, the compressive density of the negative electrode film layer can be improved, thereby increasing the energy density of the secondary battery. Furthermore, it is advantageous to form a rational 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 is selectable between 340 mAh / g and 360 mAh / g, and between 345 mAh / g and 360 mAh / g. By adjusting the gram capacity of the second carbon-based material within the above range, the energy density of the secondary battery can be improved, while the second carbon-based material can also achieve good active ion transport performance, which is advantageous for improving the dynamic performance of the secondary battery.

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

[0091] In some embodiments, more than 80% of the surface of the second carbon-based material is covered with a carbon coating layer, and optionally, 90%-100% of the surface of the graphite is covered 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 removal of active ions. The carbon may be obtained by carbonizing an organic carbon source. The organic carbon source can be a carbon-containing material known in the art that is suitable for coatings, and may include one or more of the following: coal pitch, petroleum pitch, phenolic resin, coconut shell, etc.

[0093] In some embodiments, the second carbon-based material comprises artificial graphite in secondary particle form and has a carbon coating layer on at least a portion of the surface of the artificial graphite. Optionally, the quantity proportion of the artificial graphite in secondary particle form in the second carbon-based material is 50% or more, and may be, 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 this application, the quantitative ratio of artificial graphite in secondary particle form in the second carbon-based material is determined by arbitrarily selecting one test sample in the negative electrode film layer, arbitrarily selecting multiple test areas from the test sample, acquiring images of the multiple test areas using a scanning electron microscope, statistically calculating the ratio of the number of artificial graphite particles in secondary particle form to the total number of second carbon-based material particles in each image, and averaging the multiple statistical results to determine the quantitative ratio of artificial graphite in secondary particle form in the second carbon-based material.

[0095] In some embodiments, the first carbon-based material has a pore area of ​​0.1 μm². 2 It includes one or more pore structures as described above, and selectively has a pore area of ​​0.12 μm². 2 -2.5μm 2 It includes one or more pore structures. When the first carbon-based material includes a pore structure having the above-mentioned pore area, the pore structure can secure the expansion space necessary for volume changes of its particles. This further reduces the risk of new interfaces being generated due to particle fragmentation, further reduces the occurrence of side reactions, and improves the storage performance of the secondary battery.

[0096] In some embodiments, the first carbon-based material includes an outer region and an inner region located inside the outer region, wherein the outer region is a region extended from the particle surface of the first carbon-based material into the particle at a distance of 0.25 L, where L is the short axis length of the first carbon-based material particle, the total pore area of ​​the outer region is S1, and the total pore area of ​​the inner region is S2, where S2 > S1.

[0097] If the first carbon-based material further satisfies S2>S1, it further has the characteristic of having a large number of pores and / or large pore size in the internal region, but a small number of pores and / or small pore size in the external region. The pore structure in the internal region of the first carbon-based material can secure the expansion space necessary for volume changes of the particles, thereby reducing the risk of new interface formation due to particle fragmentation, reducing the rebound coefficient of the negative electrode film layer thickness, and further reducing the occurrence of side reactions. The small number of pores and / or small pore size in the external region of the first carbon-based material gives the first carbon-based material particles a stable structure, and prevents the electrolyte from penetrating the internal pore structure of the first carbon-based material particles as much as possible, further reducing the occurrence of side reactions and reducing the consumption of active ions due to the formation of the internal SEI film of the particles. Therefore, by further satisfying S2>S1 in the first carbon-based material, 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 several embodiments, the values ​​are 1.2≦S2 / S1≦500, 1.5≦S2 / S1≦500, 2≦S2 / S1≦450, 2.2≦S2 / S1≦400, 2.4≦S2 / S1≦300, 2.5≦S2 / S1≦250, 2.6≦S2 / S1≦200, 2.8≦S2 / S1≦150, and 3.0≦S2 / S1≦100. Through further research, the inventors have found that when S2 / S1 falls within the above ranges, secondary batteries can achieve a better balance between high energy density and good storage performance.

[0099] In this application, the total pore area S1 of the outer region and the total pore area S2 of the inner region of the first carbon-based material can be obtained by testing a cross-sectional image of the first carbon-based material.

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

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

[0102] Figure 1 is a schematic diagram of a cross-sectional image of one particle of the first carbon-based material 100 of the present application, and the cross-sectional image passes through the center of the particle of the first carbon-based material 100. As shown in Figure 1, L represents the minor axis length of the particle of the first carbon-based material 100, and the stretched region extending from the surface of the particle of the first carbon-based material 100 to the interior 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 using a cross-section polisher (e.g., the IB-09010 CP type argon ion cross-section polisher from JEOL Japan). Next, the cross-section of the first carbon-based material is scanned using a scanning electron microscope (e.g., the Sigma 300 scanning electron microscope from ZEISS Germany) in reference to JY / T010-1996. Finally, the total pore area S1 of the outer region and the total pore area S2 of the inner region of the first carbon-based material are calculated using image processing software (e.g., AVIZO).

[0104] In some embodiments, the short axis length L of the first carbon-based material particles satisfies L ≥ 4 μm and can be selected from 4 μm ≤ L ≤ 25 μm, 4 μm ≤ L ≤ 20 μm, 6 μm ≤ L ≤ 20 μm, 8 μm ≤ L ≤ 20 μm, 8 μm ≤ L ≤ 18 μm, and 8 μm ≤ L ≤ 16 μm.

[0105] In some embodiments, the area of ​​the pore structure in the external region of the first carbon-based material is 0.15 μm². 2 The following are available, with a selectable size of 0.13 μm. 2The present inventors have found the following through further research: By controlling the area of ​​the pore structure in the external region of the first carbon-based material to within the above range, a dense structure can be provided in the external region of the first carbon-based material. This effectively improves the structural stability of the first carbon-based material, minimizes the penetration of the electrolyte into the pore structure inside the particles of the first carbon-based material, and further effectively improves the storage performance of the secondary battery. Of course, in this application, the area of ​​all pore structures in the external region of the first carbon-based material is all 0.15 μm. 2 This does not limit the scope to the following, for example, it can be controlled to over 95%, and the area of ​​the pore structure with over 99% of the pores can be selected to be 0.15 μm². 2 The following applies:

[0106] In some embodiments, the internal region of the first carbon-based material has an area of ​​0.15 μm². 2 It contains one or more pore structures as described above, and is selectable, with an area of ​​0.15 μm². 2 -2.0 μm 2 The material contains one or more pore structures as described above. Through further research, the inventors have found that by incorporating pore structures of the above size into the internal region of the first carbon-based material, a sufficient and stable expansion space can be secured for volume changes of the first carbon-based material particles, reducing the risk of fragmentation of the first carbon-based material particles, reducing the occurrence of side reactions, and improving the compressive density of the negative electrode film layer.

[0107] In some embodiments, the surface of the first carbon-based material is covered with a carbon coating layer. Optionally, 80% or more of the surface of the first carbon-based material is covered with the carbon coating layer, or 90%-100% of the surface of the first carbon-based material is covered with the carbon coating layer.

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

[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 a low side reaction activity, which 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, it may be 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 improves 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 quantitative ratio of the 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 obtained using a scanning electron microscope, and the ratio of the number of the first carbon-based materials in the primary particle form to the total number of the first carbon-based material particles in each image is statistically calculated, and the average value of the plurality of statistical results is the quantitative ratio of the 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 m2 / 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 It is / 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 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 reduced, the occurrence of side reactions can be decreased, and the storage performance of the secondary battery can be improved.

[0117] In some embodiments, the particle size distribution (Dv90-Dv10) / Dv50 of the first carbon-based material is ≤1.55 and selectively between 0.9 and 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 compressive density of the negative electrode film layer and the energy density of the secondary battery. It is also advantageous for forming a rational 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 examples, the tap density of the first carbon-based material is ≥ 0.8 g / cm³. 3 Therefore, 0.8 g / cm³ is available as a selectable option. 3 -1.20 g / cm³ 3 Therefore, if the tap density of the first carbon-based material is within the above range, the compressive density of the negative electrode film layer can be improved, thereby increasing the energy density of the secondary battery. Furthermore, it is advantageous to form a rational 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 at a 5000 kg press force is ≤2.10 g / cm³. 3 And it is selectable at 1.85 g / cm³ 3 -2.10 g / cm³ 3 Therefore, if the powder compressibility density of the first carbon-based material is within the above range, the compressibility density of the negative electrode film layer can be improved, thereby increasing the energy density of the secondary battery. Furthermore, it is advantageous to form a rational 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 planes of the first carbon-based material 002 is ≤0.335916 nm, and is selectively between 0.335576 nm and 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 ≥358mAh / g and selectively between 358mAh / g and 370mAh / 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 diffraction peaks on the 3R phase 101 crystal plane.

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

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

[0125] The inventors have found the following during their research: When the first carbon-based material has diffraction peaks on the 3R phase 101 crystal plane, many active sites exist on the surface of the first carbon-based material particles, which can accelerate the transport of active ions. When the first carbon-based material does not have diffraction peaks on the 3R phase 012 crystal plane, its internal defects are reduced, which can decrease the consumption of active ions and improve the initial Coulomb efficiency and storage performance of the secondary battery.

[0126] In some embodiments, thermogravimetric analysis tests of the first carbon-based material in an air atmosphere showed that the weight loss rate of the first carbon-based material between 35°C and 790°C was ≤50%, and selectively between 10%-50% and 16%-43%. The first carbon-based material has a relatively small weight loss rate between 35°C and 790°C, and at this time has fewer surface defects and / or bulk phase defects, which 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, thereby improving the storage performance of the secondary battery.

[0127] In some embodiments, in a 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 set to T max Therefore, T max The temperature range is 795°C or higher, with selectable ranges of 800°C-855°C and 805°C-850°C. The first carbon-based material has a temperature range T that corresponds to a high maximum weight loss rate. max This material possesses 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, thereby improving the storage performance of the secondary battery.

[0128] Thermogravimetric analysis (TG) testing of the first carbon-based material can be performed by referring to JY / T 014-1996. The present invention may also be carried out under the following conditions: the weighed mass of the sample is 10 ± 0.05 mg, air is used as the purge gas, the airflow rate is 60 mL / min, the heating rate is 5 °C / min, and the test temperature range is 35 °C-950 °C. The test instrument may be a NETZSCH STA 449F3 simultaneous thermal analyzer from NETZSCH GmbH, Germany. The temperature T corresponding to the maximum weight loss rate of the first carbon-based material... max This is the peak temperature of the thermogravimetric derivative curve of the first carbon-based material.

[0129] In some embodiments, the mass percentage of the first carbon-based material in the negative electrode active material is ≥30 wt% (30 wt% or more), and is selectably between 30 wt% and 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 dynamic performance.

[0130] In some embodiments, the volume distribution particle size Dv50 of the negative electrode active material is ≥6 μm and is selectably between 6 μm and 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 brought 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, and thus the dynamic performance of the secondary battery can be further improved. It can also reduce the occurrence of side reactions and improve the storage performance of the secondary battery.

[0131] In some embodiments, the particle size distribution (Dv90-Dv10) / Dv50 of the negative electrode active material is ≥0.9 (0.9 or greater) and is selectably between 0.9 and 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 brought 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 compressive density of the negative electrode film layer, and thus the energy density of the secondary battery can be further improved. It is also advantageous for forming a rational pore structure between the particles of the negative electrode film layer, which is beneficial for improving the dynamic performance of the secondary battery.

[0132] In some embodiments, the degree of graphitization of the negative electrode active material is 92% or higher, and is selectably between 92% and 96%. By adjusting parameters such as the degree of graphitization and mass content of the first carbon-based material and / or the second carbon-based material, the degree of graphitization of the negative electrode active material can be brought within the above range. Adjusting the degree of graphitization of the negative electrode active material within the above range is advantageous because it allows the negative electrode active material to have a high gram capacity and good active ion transport performance, thus enabling the secondary battery to achieve both high energy density and good dynamic performance.

[0133] In some embodiments, the gram capacity of the negative electrode active material is ≥350 mAh / g, and is selectably between 350 mAh / g and 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 brought within the above range. Adjusting the gram capacity of the negative electrode active material within the above range is advantageous for improving the energy density of the secondary battery.

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

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

[0136] In some embodiments, the negative electrode film layer may optionally further contain a negative electrode conductive agent. The type of the negative electrode conductive agent is not particularly limited in this application. For example, the negative electrode conductive agent may include one or more of the following: 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. The type of the negative electrode adhesive is not particularly limited in this application. For example, the negative electrode adhesive may contain one or more of the following: styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic resin (e.g., polyacrylate PAA, polymethacrylate 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 additives. For example, the other additives may include thickeners such as sodium carboxymethylcellulose (CMC), PTC thermistor material, etc.

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

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

[0141] The negative electrode sheet does not exclude any additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode sheet according to the present invention further includes a conductive undercoat layer (e.g., consisting 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, and in some embodiments, the negative electrode sheet according to the present invention 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 is selectably between 15.5% and 38%. This is advantageous for the negative electrode film layer to achieve both high capacity and an appropriate pore structure, and is advantageous for the secondary battery to achieve both high energy density and good storage and dynamic performance.

[0143] In some embodiments, the compressed density of the negative electrode film layer is ≥ 1.40 g / cm³. 3 And it is selectable at 1.40 g / cm³3 -1.80 g / cm³ 3 This is advantageous for the negative electrode film layer to achieve both high capacity and high active ion and electron transport performance, and further advantageous for the secondary battery to achieve both high energy density and good storage and dynamic performance.

[0144] In some embodiments, the surface density of the negative electrode film layer is ≥ 5.5 g / cm³. 2 And, as selectable, 6.0 g / cm³ 3 -19.5 g / cm³ 2 This is advantageous for the negative electrode film layer to achieve both high capacity and high active ion and electron transport performance, and further advantageous for the secondary battery to achieve both high energy density and good storage and dynamic performance.

[0145] In some embodiments, the OI value of the negative electrode film layer is ≤38 and can be selected between 8 and 38. This is advantageous for improving the active ion insertion performance of the negative electrode film layer, allows the negative electrode film layer to have a low repulsion rate at a low thickness, and is also advantageous for achieving both good storage performance and kinetic performance of the secondary battery.

[0146] The negative electrode current collector has two opposing surfaces in the thickness direction, and the negative electrode film layer is provided on one or both of the two opposing surfaces of the negative electrode current collector. Note that each negative electrode film layer parameter provided in this application (e.g., compressive density, surface density, porosity, OI value, etc.) refers to the parameter of the negative electrode film layer on one side of the negative electrode current collector. If the negative electrode film layer is provided on both sides of the negative electrode current collector, it is considered that the application falls within the scope of protection if the parameters of the negative electrode film layer on either side satisfy the requirements of this application.

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

[0148] In this application, whether or not a coating layer exists on the surface of a material (for example, a first carbon-based material, a second carbon-based material, etc.) can be determined by a transmission electron microscope.

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

[0150] In this application, the degree of graphitization of the negative electrode active material has a meaning known in the art and can be tested using instruments and methods known in the art. For example, it can be tested using an X-ray diffractometer (e.g., Bruker D8 Discover), and the test can be performed referring to JIS K 0131-1996, JB / T 4220-2011, to determine the average interlayer distance d of the C(002) crystal plane in the material's crystal structure. 002 After obtaining the equation g=(0.344-d 002 The degree of graphitization can be calculated based on ) / (0.344-0.3354)×100%. In the above formula, d 002 This is the average interlayer distance of the C(002) crystal plane in the material crystal structure, expressed in nanometers (nm).

[0151] In this application, the volume distribution particle sizes Dv10, Dv50, and Dv90 of materials (e.g., first carbon-based materials, second carbon-based materials, negative electrode active materials, etc.) have meanings known in the art, and represent the particle sizes corresponding to when the cumulative volume distribution percentage of the material reaches 10%, 50%, and 90%, respectively, and can be measured with instruments and methods known in the art. For example, they can be measured using a laser particle size analyzer, referring to GB / T 19077-2016. The test instrument may be a Mastersizer 3000 laser particle size analyzer from Malvern Panalytical Ltd., UK.

[0152] In this application, the powder compressibility density of a material (e.g., first carbon-based material, second carbon-based material, etc.) is in the sense known in the art and can be measured with instruments and methods known in the art. For example, it can be measured by an electronic pressure tester (e.g., a UTM7305 electronic pressure tester) referring to GB / T24533-2009. An exemplary test method involves weighing 1 g of sample powder and measuring it with a base area of ​​1.327 cm². 2 The material is placed in a mold, pressurized to 5000 kg, held for 30 seconds, the pressure is released, held for 10 seconds, and then the powder compression density of the material at a 5000 kg press force is recorded and calculated.

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

[0154] In this application, the material (e.g., first carbon-based material, second carbon-based material, etc.) D / I G This can be tested using a Raman spectrometer. D This is the Raman spectrum of the material at 1350±50 cm⁻¹. -1This represents the D peak intensity at I G This is the Raman spectrum of the material at 1580±50 cm⁻¹. -1 This represents the G peak intensity at [location]. The test conditions were: excitation wavelength 532 nm, diffraction grating with 600 markings, objective lens with 50x magnification, integration time 10 s, cumulative number of trials 3, surface scanning to obtain 100 points of D peak and G peak intensity. D / I G Calculate the maximum and minimum 30 I D / I G Remove the remaining 40 points, and the average value of the material I D / I G The Horiba LabRAM HR800 Raman spectrometer can be used as the test equipment.

[0155] In this application, primary particles and secondary particles are both known in the art. Primary particles are particles in a non-aggregated state. Secondary particles are particles in an aggregated state formed by the aggregation of two or more primary particles. Primary and secondary particles can be distinguished using scanning electron microscope (SEM) images.

[0156] In this application, the gram capacity (also called the capacity per gram) of a material (e.g., first carbon-based material, second carbon-based material, negative electrode active material, etc.) has a meaning known in the art and can be tested by methods known in the art. An exemplary test method involves uniformly mixing the sample powder with the conductive agent carbon black (Super P) and the adhesive polyvinylidene fluoride (PVDF) in a mass ratio of 91.6:1.8:6.6 with the solvent N-methylpyrrolidone (NMP) to prepare a slurry. The prepared slurry is then applied to the surface of a copper foil negative electrode current collector and dried in an oven. Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent. LiPF6 is then dissolved in the organic solvent to prepare an electrolyte with a concentration of 1 mol / L. Subsequently, a CR2430 type coin cell is assembled in a glove box protected by the electrolyte and argon gas, using a metallic lithium sheet as the counter electrode and a polyethylene (PE) thin film as the separator. After the resulting coin cell is left to stand for 12 hours, it is discharged at 25°C at 0.05C to 0.005V, left to stand for 10 minutes, discharged at a constant current of 50 μA to 0.005V, left to stand for 10 minutes, and discharged at a constant current of 10 μA to 0.005V. After that, it is charged at 0.1C to 2V with a constant current, and the charged capacity is recorded. The ratio of the charge capacity to the sample mass is the gram capacity of the corresponding material (e.g., first carbon-based material, second carbon-based material, negative electrode active material, etc.).

[0157] In this application, the surface density of the negative electrode film layer has a meaning known in the art and can be tested by methods known in the art. For example, a negative electrode sheet coated on one side and cold-pressed (if the negative electrode sheet is coated on both sides, the negative electrode film layer on one side can be wiped off first) is selected and punched out into a small disc with an area of ​​S1, and its weight is recorded as M1. Then, the negative electrode film layer of the weighed negative electrode sheet is wiped off, the weight of the negative electrode current collector is weighed and recorded as M0. Surface density of the negative electrode sheet = (M1 - M0) / S1.

[0158] In this application, the compressive density of the negative electrode film layer is as known in the art and can be tested by methods known in the art. Compressive density of the negative electrode film layer = surface density of the negative electrode film layer / thickness of the negative electrode film layer. The thickness of the negative electrode film layer is as known in the art and can be tested using methods known in the art, for example, by using a micrometer (e.g., Mitutoyo 293-100, accuracy 0.1 μm).

[0159] In this application, the porosity of the negative electrode film layer has a meaning known in the art and can be measured by methods known in the art. An exemplary test method involves taking a negative electrode sheet coated on one side and cold-pressed (if the negative electrode sheet is coated on both sides, the negative electrode film layer on one side can be wiped off first), punching it into a small disc sample of a certain area, calculating the apparent volume V1 of the negative electrode sheet, and testing the true volume V2 of the negative electrode sheet using a true density tester with a gas displacement method employing an inert gas (e.g., helium or nitrogen gas) as the medium, referring to GB / T24586-2009. Porosity of the negative electrode film layer = (V1-V2) / V1 × 100%. The accuracy of the test results can be improved by testing multiple samples (e.g., 30) of negative electrode sheets with good appearance and no powder fallout at the edges, and taking the average value of the results. As the test equipment, a Micromeritics AccuPyc II 1340 true density tester can be used.

[0160] In this application, the OI value of the negative electrode film layer has a meaning known in the art and can be tested using instruments and methods known in the art. For example, it can be tested using an X-ray diffractometer (e.g., Bruker D8 Discover). The test is performed by obtaining the X-ray diffraction pattern of the negative electrode sheet, referring to JIS K 0131-1996 and JB / T 4220-2011. OI value = I 004 / I 110 The OI value of the negative electrode film layer is calculated based on this. 004 This is the integral area of ​​the diffraction peaks of the crystalline carbon 004 crystal plane in the negative electrode film layer, and I 110 This represents the integrated area of ​​the diffraction peaks of the crystalline carbon 110 crystal plane in the negative electrode film layer.

[0161] In the X-ray diffraction analysis test of this invention, 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] Furthermore, the various parameters for the negative electrode active material or negative electrode film layer described above can be tested by sampling from secondary batteries manufactured according to the following steps.

[0163] The secondary battery is discharged (generally completely discharged for safety), the battery is removed, and the negative electrode sheet is taken out. The negative electrode sheet is then immersed in dimethyl carbonate for a certain period of time (e.g., 2-10 hours), and then the negative electrode sheet is removed and dried at a certain temperature and time (e.g., 60°C, 4 hours or more). After drying, the negative electrode sheet is removed. In this case, samples can be taken from the dried negative electrode sheet to test various parameters related to the negative electrode film layer, such as the surface density, compressive density, porosity, and OI value of the negative electrode film layer.

[0164] The dried negative electrode sheet is fired at a constant temperature and time (for example, 400°C for 2 hours or more), the negative electrode active material is sampled from any one area of ​​the fired negative electrode sheet (the powder may be scraped off using a blade), the collected negative electrode active material is processed by sieving (for example, by sieving with a 200-mesh sieve), and finally a sample is obtained for testing the parameters of each of the negative electrode active materials.

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

[0166] In some embodiments, the method for producing the first carbon-based material includes: step 1 providing a raw material having a plurality of pore structures; step 2 uniformly mixing the raw material and a filler in a predetermined ratio, then maintaining the mixture at a first temperature T1 for a first time t1, and after completion, cooling to room temperature to obtain an intermediate; and step 3 maintaining the obtained intermediate at a second temperature T2 for a second time t2, and after completion, obtaining the first carbon-based material.

[0167] In some embodiments, in step 1, the raw materials for producing the first carbon-based material include natural graphite. Optionally, the natural graphite includes one or more of the following: flake graphite, natural spheroidal graphite, and microcrystalline graphite, and more optionally, natural spheroidal graphite.

[0168] "Natural spheroidal graphite" refers to natural graphite that is spherical or near-spheroidal, and does not mean that all natural graphite particles are controlled to be ideal spheres. In some examples, natural spheroidal graphite of a desired particle size and morphology can be obtained by pretreatment of flake graphite. Optionally, the pretreatment may include steps 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 to 25.0 μm.

[0170] In some embodiments, in step 1, the specific surface area of ​​the raw material is ≥ 2.5 m². 2 It may also be / g, and 2.5m is selectable. 2 / g-10.0m 2 The value is / g. When the specific surface area of ​​the raw material is within the above range, it is advantageous to perform the subsequent filling process to obtain a first carbon-based material with the desired specific surface area, and it is also advantageous for the first carbon-based material to have high capacity and high initial Coulomb efficiency. Furthermore, it is advantageous for the first carbon-based material to have better dynamical performance.

[0171] In some embodiments, in step 2, the softening point temperature of the filler is 90°C-150°C. Selectively, the softening point temperatures of the filler are 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, and 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 is selectable to be 1 μm-6 μm, 1 μm-5 μm, 2 μm-5 μm, or 3 μm-5 μm. This is advantageous because the filler material fills the pore structure of the raw material after being melted by heat, and is also advantageous in improving the uniformity of the dispersion between the filler material and the raw material.

[0173] In some embodiments, in step 2, the caulking value of the filler is 15%-40%, and selectively 18%-34%. In this application, the caulking value of the filler has an art-known meaning and can be measured with art-known instruments and methods. 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 optionally includes one or more of coal pitch and petroleum pitch.

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

[0176] In step 2, adjusting one or more parameters such as the type of filler, softening point, coking value, and amount of additive within the above range is advantageous in adjusting the number and / or size of pores in the external and internal regions of the first carbon-based material to an appropriate range, and is advantageous in adjusting the S2 / S1 of the first carbon-based material to an appropriate range.

[0177] By adjusting parameters such as the type of filler, softening point, coking value, and amount of additive within the above range, the filler can maintain good fluidity without high viscosity after melting due to heat, and the raw material particles can be less likely to adhere to each other, reducing aggregation of raw material particles in subsequent manufacturing processes. This also reduces problems such as an increase in surface defects in the primary carbon-based material particles and an increase in surfactant sites, which would otherwise be necessary due to the need to increase the depolymerization process.

[0178] In some embodiments, the heating process in step 2, in which the raw materials and the filling material are uniformly mixed in a predetermined ratio and then heated to a first temperature T1, 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 involves raising the temperature to 200°C-250°C and maintaining the temperature for 0.5h-3h.

[0181] In some embodiments, the second heating process involves raising the temperature to 450°C-550°C and maintaining that temperature for 0-2 hours. When the maintenance time is 0 hours, it indicates that no maintenance is performed when raising the temperature within the 450°C-550°C range, and the temperature continues to rise to the first temperature T1.

[0182] In some embodiments, the third heating process involves raising the temperature to the first temperature T1 and maintaining that temperature for a first time t1.

[0183] In the stepwise heating process, the temperature is first raised to 200°C-250°C. Since the heating temperature is higher than the softening point of the filler, the filler melts and softens due to the heat at this time, and can be fluidly filled into the pore structure of the raw material by being kept warm for 0.5-3 hours. Subsequently, the temperature is raised to 450°C-550°C, at which point the molten and softened filler undergoes a carbonization reaction, gradually becoming a semi-coked state, turning into a viscous liquid or solid. This prevents the filler from entering all the pore structures of the raw material. Finally, the temperature is raised to the first temperature, at which point the filler undergoes a carbonization reaction, thereby effectively filling the pore structures occupied by the filler.

[0184] In some embodiments, in step 2, the temperature is raised to the first temperature T1 at a rate of 1°C / min-10°C / min. For example, the heating rate may be in the range 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 of these values. Selectively, the heating rates are 1.5°C / min-8°C / min, 1.5°C / min-6°C / min, 2°C / min-6°C / min, and 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 may be selectively 1.5°C / min-8°C / min, 1.5°C / min-6°C / min, 2°C / min-6°C / min, or 2°C / min-5°C / min.

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

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

[0188] In some embodiments, in step 2, the first temperature T1 is 700°C-1200°C. For example, the first temperature T1 may be in the range of any number of 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1200°C or higher. Selectively, the first temperature T1 is 750°C-1100°C, 800°C-1100°C, 850°C-1100°C, 900°C-1100°C, or 850°C-1000°C.

[0189] In some embodiments, in step 2, the first time t1 is 1h-5h. For example, the first time t1 may be in the range of 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, or any of these values. Selectively, the first time t1 is 2h-4h.

[0190] In some embodiments, in step 2, the heat treatment can be carried out in equipment capable of programmed heating, such as an intermediate frequency furnace, roller hearth kiln, rotary kiln, pusher hearth kiln, vertical granulator, horizontal granulator, vertical reaction vessel, horizontal reaction vessel, or 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, adjusting one or more of the heating rate, first temperature, first time, heating process, etc., within the above range is advantageous for adjusting the number and / or size of pores in the external and internal regions of the first carbon-based material within an appropriate range, and further advantageous for adjusting the S2 / S1 of the first carbon-based material within an appropriate range.

[0193] In some embodiments, in step 3, the second temperature T2 is 2070°C-2700°C. Selectively, the second temperature T2 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, or 2140°C-2360°C.

[0194] In some embodiments, in step 3, the second time t2 is 1.5h-6h. For example, the second time t2 may be in the range of 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, or any of these values. Selectively, the second time t2 is 2h-5h.

[0195] In some embodiments, in step 3, the heat treatment can be carried out in a medium-frequency furnace, a box-type graphitizing furnace, an Acheson-type graphitizing furnace, a continuous graphitizing furnace, or an internal series graphitizing furnace.

[0196] In some embodiments, in step 3, the intermediate frequency furnace and the 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, adjusting one or more of the second temperature and second time within the above range is advantageous in adjusting the amorphous carbon content in the first carbon-based material to an appropriate range, and the first carbon-based material has an appropriate degree of graphitization, interlayer distance and I D / I G Having such advantages is beneficial.

[0198] In the method for producing the first carbon-based material described above, by adjusting one or more of the parameters of natural graphite, filler parameters, heating rate, first temperature, first time, heating process, second temperature, second time, etc., within the above range, the S2 / S1, I of the first carbon-based material can be obtained. D / I GThis is advantageous for adjusting parameters such as graphitization degree, gram volume, specific surface area, particle size, powder compression density, tap density, and weight loss rate.

[0199] In some embodiments, the method for producing the second carbon-based material includes mixing a raw material with an organic carbon source, then performing a carbonization treatment to form a carbon coating layer on the surface of at least some of the particles, and obtaining the 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 be a carbon-containing material known in the art that is suitable for coating, and may include one or more of the following: coal pitch, petroleum pitch, phenolic resin, coconut shell, etc.

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

[0202] In the above method for producing a second carbon-based material, by adjusting one or more parameters from among the parameters of the raw material (e.g., particle size, specific surface area, particle size distribution, gram volume, etc.), the amount of organic carbon source added, carbonization temperature, carbonization time, etc., the second carbon-based material can be produced. D / I G This is advantageous for adjusting parameters such as graphitization degree, interlayer distance, gram volume, particle size, specific surface area, powder compression density, and tap density. [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 opposing surfaces in the direction of its own thickness, and the positive electrode film layer is provided on one or both of the two opposing surfaces of the positive electrode current collector.

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

[0205] The positive electrode film layer typically comprises a positive electrode active material, a selectable adhesive, and a selectable conductive agent. The positive electrode film layer is typically formed by applying a positive electrode slurry to the positive electrode current collector, drying, and cold pressing. The positive electrode slurry is typically formed by dispersing the positive electrode active material, a selectable conductive agent, a selectable adhesive, and other selectable components in a solvent and stirring uniformly. The solvent may, but is not limited to, N-methylpyrrolidone (NMP). For example, the adhesive used for the positive electrode film layer may include one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a ternary copolymer of vinylidene fluoride-tetrafluoroethylene-propylene, a ternary copolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, a copolymer of tetrafluoroethylene-hexafluoropropylene, and a fluorine-containing acrylate resin. For example, the conductive agent used in the positive electrode film layer includes one or more of the following: 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 be a positive electrode active material for secondary batteries known in this field.

[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 and their modified compounds with the general formula Li a Ni b Co c M d O e A f where 0.8 ≦ a ≦ 1.2, 0.5 ≦ b < 1, 0 < c < 1, 0 < d < 1, 1 ≦ e ≦ 2, 0 ≦ f ≦ 1, M is one or more selected from Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, and B, and A is one or more selected from N, F, S, and Cl.

[0209] In some embodiments, for example, the positive electrode active material for the lithium ion battery is LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3O2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), LiNi 0.80 Co 0.15 Al 0.05 It may contain one or more of the following: O2, LiFePO4, and LiMnPO4.

[0210] In this application, the modified compounds for each of the above-mentioned positive electrode active materials are obtained by performing doping modification and / or surface coating modification on the positive electrode active material. [Electrolyte]

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

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

[0213] If the secondary battery of the present application is a lithium-ion battery, the electrolyte salt may, for example, include one or more of the following: lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonylimide (LiFSI), lithium bistrifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB) and lithium bisoxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobisoxalate phosphate (LiDFOP) and lithium tetrafluorooxalate phosphate (LiTFOP).

[0214] The type of solvent is not particularly limited and can be selected according to actual demand. In some examples, the organic solvent may include, for instance, one or more of the following: 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 contain additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain performance characteristics of the secondary battery, such as additives that improve the overcharge performance of the secondary battery, additives that improve the high-temperature performance of the secondary battery, and additives that improve the low-temperature output performance of the secondary battery. [Separator]

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

[0217] In some embodiments, the separator material may include one or more of the following: glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film. If the separator is a multilayer 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 manufactured into an electrode assembly by a winding process or a lamination process.

[0219] In some embodiments, the secondary battery may include an outer casing. This casing is used to seal the electrode assembly and electrolyte described above.

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

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

[0222] In some embodiments, as shown in Figure 3, the exterior may 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 side plates enclose a housing chamber. The case 51 has an opening that communicates with the housing chamber, and the cover plate 53 closes the opening so as to close the housing chamber. The positive electrode sheet, negative electrode sheet and separator can be formed into an electrode assembly 52 by a winding process or a lamination process. The electrode assembly 52 is packaged into the housing chamber. The electrolyte permeates the electrode assembly 52. ​​The number of electrode assemblies 52 included in the secondary battery 5 may be one or more and may be adjusted according to demand.

[0223] The method for manufacturing the secondary battery of the present invention 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. For example, an electrode assembly can be formed by winding or laminating a positive electrode sheet, a separator, and a negative electrode sheet, the electrode assembly can be placed in an outer casing, dried, and then the electrolyte can be injected. A secondary battery can then be obtained through processes such as vacuum sealing, standing, chemical formation, and shaping.

[0224] In some embodiments of the present invention, the secondary battery may be assembled into a battery module, and the number of secondary batteries included in the battery module may be multiple, and the specific number may be adjusted according to the application and capacity of the battery module.

[0225] Figure 4 is a schematic diagram of a battery module 4 as an example. As shown in Figure 4, in the battery module 4, the multiple secondary batteries 5 may be arranged sequentially along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, these multiple secondary batteries 5 may be fixed together with fasteners.

[0226] Optionally, the battery module 4 further includes an external case having a housing space, and multiple secondary batteries 5 are housed in the housing space.

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

[0228] Figures 5 and 6 are schematic diagrams of an example battery pack 1. As shown in Figures 5 and 6, the battery pack 1 may include a battery housing and a plurality of battery modules 4 provided in the battery housing. The battery housing includes an upper housing 2 and a lower housing 3, with the upper housing 2 covering the lower housing 3 and forming a sealed space for housing the battery modules 4. The plurality of battery modules 4 may be arranged in the battery housing 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] Another example of the power consumption device may be a mobile phone, a tablet computer, a notebook computer, etc. This power consumption device is generally required to be thin, and a secondary battery can be adopted as a power source. Examples

[0233] The following examples illustrate the content of the present application in more detail. However, these examples are merely illustrative explanations, 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. Also, 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. Moreover, all the devices used in the examples are commercially available.

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

[0235] In each of the following examples and comparative examples, except that artificial graphite without a coating layer was used 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 are all 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 temperature increase, and stepwise temperature increase 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 for heat treatment. After completion, it was demagnetized and sieved to obtain the first carbon-based material. In the above process, it can be controlled according to the manufacturing process of the first carbon-based material mentioned in the present application so that parameters such as S2 / S1, interlayer distance, and volume distribution particle size Dv50 of the first carbon-based material are within the ranges shown in Table 1.

[0237] The S2 / S1 of the first carbon-based material is tested by the following method: After uniformly mixing the sample preparation adhesive with the first carbon-based material powder, the mixture is applied to copper foil and dried at 60°C for 30 minutes. The sample is then cut to a size of 6 mm × 6 mm and attached to the sample stage of a CP-type argon ion cross-section polisher. The sample is cut using a plasma beam to obtain a cross-section of the first carbon-based material, and the cross-section of the first carbon-based material passes through the center of the first carbon-based material particles. The IB-09010 CP-type argon ion cross-section polisher from JEOL Japan can be used as the test apparatus. The cross-section of the first carbon-based material was scanned using a scanning electron microscope. The test can be referred to in JY / T010-1996. The test instrument may also be a Sigma 300 scanning electron microscope from ZEISS Germany. The region extending 0.25 L from the particle surface to the interior of the first carbon-based material is defined as the outer region, and the region inside the outer region is defined as the inner region, where L represents the short axis length of the particle of the first carbon-based material. The total pore area S1 of the outer region and the total pore area S2 of the inner region of the first carbon-based material were calculated using image processing software. AVIZO may also be used as the image processing software. The secondary batteries in Examples 1-29 and Comparative Examples 1-3 were all manufactured by the following method.

[0238] A negative electrode slurry was formed by thoroughly stirring and mixing a negative electrode active material (a mixture of first-carbon and second-carbon materials; see Table 1 for details), a conductive agent (carbon black, Super P), a thickener (carboxymethylcellulose sodium), and an adhesive (styrene-butadiene rubber) in a weight ratio of 96.4:1:1.2:1.4 with an appropriate amount of deionized water as a solvent. The negative electrode slurry was applied to two surfaces of a copper foil negative electrode current collector, dried, and cold-pressed to obtain a negative electrode sheet.

[0239] LiRing 0.5 Co 0.2 Mn 0.3O2 (NCM523), the conductive agent carbon black (Super P), and the adhesive polyvinylidene fluoride were mixed in a weight ratio of 96:2:2. An appropriate amount of solvent, NMP, was added, and the mixture was uniformly stirred to obtain a positive electrode slurry. The positive electrode slurry was applied to two surfaces of aluminum foil, which served as the positive electrode current collector. After drying and cold pressing, a positive electrode sheet was obtained.

[0240] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. Then, LiPF6 was dissolved in the above organic solvent to prepare an electrolyte solution with a concentration of 1 mol / L.

[0241] A polyethylene film is used as a separator, and the positive electrode sheet and negative electrode sheet manufactured above are arranged in order. The separator is positioned between the positive electrode sheet and the negative electrode sheet to provide isolation, and then the film is wound to obtain an electrode assembly. The electrode assembly is placed in an outer casing, dried, and then the electrolyte is injected. After going through processes such as vacuum sealing, standing, chemical formation, and shaping, a secondary battery is obtained. Performance testing (1) Testing of the rapid charging performance of secondary batteries

[0242] At 25°C, the secondary battery is charged with a constant current of 0.33C up to 4.3V, then charged with a constant voltage until the current drops to 0.05C, left to stand for 5 minutes, and then discharged with a constant current of 0.33C up to 2.8V. Its actual capacity is defined as C0.

[0243] Subsequently, the secondary battery was charged with a constant current at 1.0C0, 1.3C0, 1.5C0, 1.8C0, 2.0C0, 2.3C0, 2.5C0, and 3.0C0 in sequence until it reached a negative electrode cutoff potential of 4.3V or 0V (referenced to the first one reached). After each charge was complete, it was discharged to 2.8V at 1C0, and then charged at different rates to 10%, 20%, 30%, ..., 80% SOC (State of Charge). When the battery is charged to the state of charge (SOC), the corresponding negative electrode potential is recorded. Charge rate-negative electrode potential curves are drawn for different SOC states, and after linear fitting, the charge rate corresponding to when the negative electrode potential is 0V in each SOC state is obtained. This charge rate represents the charge window for that SOC state, denoted as C10%SOC, C20%SOC, C30%SOC, C40%SOC, C50%SOC, C60%SOC, C70%SOC, and C80%SOC, respectively. The charging time T from 10%SOC to 80%SOC of the secondary battery (assuming no lithium is deposited in the secondary battery) is calculated based on the formula (60 / C20%SOC+60 / C30%SOC+60 / C40%SOC+60 / C50%SOC+60 / C60%SOC+60 / C70%SOC+60 / C80%SOC) × 10%, with the unit being min. The shorter the charging time, the better the kinetic performance of the secondary battery. (2) Testing of the storage performance of secondary batteries

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

[0245] At 25°C, the secondary battery manufactured as described above was charged with a constant current of 1C to 4.3V, and then charged with a constant voltage until the current reached 0.05C. Afterward, the secondary battery was stored in a constant temperature bath at 60°C for 180 days. The capacity retention rate (%) of the secondary battery after 180 days of storage at 60°C = Discharge capacity after storage / Discharge capacity before storage × 100%.

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

[0247] 综合实施例1、比较例1和比较例2的测试结果可知,第一碳系材料和第二碳系材料之间具有协同效应,在电池具有高能量密度的前提下,电池具有更长的储存寿命。

[0248] In Comparative Example 3, a second carbon-based material without a carbon coating layer is combined with the first carbon-based material for use, and both the kinetic performance and storage performance of the battery are inferior.

[0249] Note that the present application is not limited to the above embodiments. The above embodiments are illustrative, and any configurations that have substantially the same technical concept and the same effects within the technical scope of the present application are included in the technical scope of the present application. Also, within the scope not departing from the gist of the present application, various modifications that those skilled in the art can conceive for the embodiments, and other forms constructed by combining some components in the embodiments are also included in the scope of the present application.

[0250]

Table 1

Explanation of Reference Signs

[0251] 1 Battery Pack 2 Upper Housing 3 Lower Housing 4 Battery Module 5 Secondary Battery 51 Case 52 Electrode Assembly 53 Cover Plate [[ID=四十四]]100 First Carbon-Based Material 101 External Region 102 Internal Domain

Claims

1. A secondary battery including a negative electrode sheet, The negative electrode sheet comprises 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 comprises a first carbon-based material and a second carbon-based material, wherein the first carbon-based material has a porous structure and the second carbon-based material has a carbon coating layer on at least a portion of its surface. The first carbon-based material comprises an outer region and an inner region located inside the outer region, wherein the outer region is a region extended from the particle surface of the first carbon-based material into the particle at a distance of 0.25 L, where L is the short axis length of the particle of the first carbon-based material, the total pore area of ​​the outer region is S1, the total pore area of ​​the inner region is S2, and S2 > S1, wherein the 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 greater than the interlayer distance of the crystal plane of the first carbon-based material 002.

3. The secondary battery according to claim 1, 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 claim 1, 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 G peak in the Raman spectrum of the second carbon-based material Ｄ / I Ｇ The peak intensity ratio I of the D peak and G peak in the Raman spectrum of the first carbon-based material is Ｄ / I Ｇ A secondary battery according to claim 1, which is larger than the one described above.

6. The secondary battery according to claim 1, wherein the second carbon-based material includes secondary particles.

7. The secondary battery according to claim 6, wherein the quantity ratio of the secondary particles in the second carbon-based material is 50% or more.

8. The secondary battery according to claim 1, wherein the second carbon-based material satisfies the following conditions. (1) The peak intensity ratio I of the D peak and G peak in the Raman spectrum of the second carbon-based material Ｄ / I Ｇ The value is ≥ 0.

23. (2) The powder compression density of the second carbon-based material at a pressing force of 5000 kg is ≥ 1.65 g / cm³ ３ That is the case. (3) The interlayer distance of the crystal planes of the second carbon-based material 002 is ≤ 0.336217 nm. (4) The gram capacity of the second carbon-based material is ≥ 340 mAh / g.

9. The secondary battery according to claim 1, wherein the second carbon-based material satisfies the following conditions. (1) The specific surface area of ​​the second carbon-based material is ≥ 0.90 m² / g. (2) The volume distribution particle size Dv50 of the second carbon-based material is ≥ 10 μm. (3) The particle size distribution (Dv90 - Dv10) / Dv50 of the second carbon-based material is ≤ 1.

65. (4) The tap density of the second carbon-based material is ≥ 0.85 g / cm³.

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

11. The first carbon-based material has a pore area of ​​0.1 μm². ２ The secondary battery according to claim 1, comprising one or more pore structures as described above.

12. 1.5 ≤ S ２ / S １ ≤ 500, the secondary battery according to Claim 1.

13. The area of ​​the pore structure in the external region of the first carbon-based material is 0.15 μm². ２ The following and / or, The internal region of the first carbon-based material has an area of ​​0.15 μm ２ The secondary battery according to claim 1, comprising one or more pore structures as described above.

14. The secondary battery according to claim 1, wherein the first carbon-based material has a carbon coating layer on at least a portion of its surface.

15. The secondary battery according to claim 1, wherein the first carbon-based material includes primary particles.

16. The secondary battery according to claim 15, wherein the quantity ratio of primary particles in the first carbon-based material is 50% or more.

17. The secondary battery according to claim 1, wherein the first carbon-based material satisfies the following conditions. (1) The specific surface area of ​​the first carbon-based material is ≤ 2.3 m² / g. (2) The volume distribution particle size Dv50 of the first carbon-based material is ≥ 6.0 μm. (3) The volume distribution particle size Dv90 of the first carbon-based material is ≥ 16.0 μm. (4) The particle size distribution (Dv90 - Dv10) / Dv50 of the first carbon-based material is ≤ 1.

55.

18. The secondary battery according to claim 1, wherein the first carbon-based material satisfies the following conditions. (1) The tap density of the first carbon-based material is ≥ 0.8 g / cm³. (2) The powder compression density of the first carbon-based material under a pressing force of 5000 kg is ≤ 2.10 g / cm³. (3) The interlayer distance of the crystal planes of the first carbon-based material 002 is ≤ 0.335916 nm. (4) The gram capacity of the first carbon-based material is ≥ 358 mAh / g.

19. The secondary battery according to claim 1, wherein the first carbon-based material satisfies the following conditions. (1) The X-ray diffraction pattern of the first carbon-based material has diffraction peaks on the 3R phase 101 crystal plane. (2) The X-ray diffraction pattern of the first carbon-based material does not have diffraction peaks on the 3R phase 012 crystal plane. (3) In a 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%. (4) In a thermogravimetric analysis test of the first carbon-based material under an air atmosphere, if T max is the temperature corresponding to the maximum weight loss rate of the first carbon-based material, then T max is 795°C or higher.

20. The secondary battery according to claim 1, wherein the mass ratio of the negative electrode active material in the first carbon-based material is ≥ 30% by weight.

21. The secondary battery according to claim 1, wherein the negative electrode active material satisfies the following conditions. (1) The volume distribution particle size Dv50 of the negative electrode active material is ≥ 6 μm. (2) The particle size distribution of the negative electrode active material (Dv90 - Dv10) / Dv50 is ≥ 0.

9. (3) The degree of graphitization of the negative electrode active material is ≥ 92%. (4) The gram capacity of the negative electrode active material is ≥ 350 mAh / g.

22. The secondary battery according to claim 1, wherein the negative electrode film layer further comprises a silicon-based material.

23. The secondary battery according to claim 1, wherein the negative electrode film layer satisfies the following conditions. (1) The porosity of the negative electrode film layer is ≥ 15.5%. (2) The compressive density of the negative electrode film layer is ≥ 1.40 g / cm³ ３ That is the case. (3) The surface density of the negative electrode film layer is ≥ 5.5 g / cm³ ２ That is the case. (4) The OI value of the negative electrode film layer is ≤38.

24. A power consumption device comprising a secondary battery according to any one of claims 1 to 23.

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