Composite artificial graphite, its preparation method, and a secondary battery and electrical device comprising the composite artificial graphite.

Abstract

This application provides a composite artificial graphite, a method for preparing the same, and a secondary battery and electrical device comprising the composite artificial graphite. The composite artificial graphite includes graphite A and graphite B. Graphite A consists of secondary particles with a graphite interlayer spacing d002 of 0.33560 nm to 0.33610 nm; graphite B consists of primary particles with a graphite interlayer spacing d002 of 0.33620 nm to 0.33670 nm; and the mass percentage content of graphite A in the composite artificial graphite is 40% to 90%. The secondary battery provided by this application can maintain high energy density while exhibiting low cycle volume expansion.

Description

Technical Field

[0001] This application relates to the field of secondary battery technology, and in particular to a composite artificial graphite, a method for preparing the same, and a secondary battery and electrical device comprising the composite artificial graphite. Background Technology

[0002] Secondary batteries are widely used due to their outstanding characteristics such as high energy density, no pollution, and long service life.

[0003] However, in secondary batteries, continuous charging and discharging causes volume changes in the negative electrode active material during lithium insertion / extraction, such as volume expansion during cycling. This increases the battery's internal stress, thus affecting its lifespan and safety performance. Recently, with the rapid popularization of new energy vehicles, the market demands increasingly higher lifespan and safety performance from power-type secondary batteries. Therefore, to enhance the market competitiveness of new energy vehicles, it is necessary to provide a new technology that can reduce the volume expansion of secondary batteries. Summary of the Invention

[0004] This application is made in view of the above-mentioned problems, and its purpose is to provide a composite artificial graphite with low expansion and high specific capacity, a method for preparing the same, and a negative electrode sheet prepared from the composite artificial graphite as a negative electrode active material. Furthermore, this application also aims to provide a secondary battery with low volume expansion and high energy density during cycling, a battery module comprising the secondary battery, a battery pack, and an electrical device.

[0005] To achieve the above objectives, a first aspect of this application provides a composite artificial graphite comprising graphite A and graphite B, wherein graphite A consists of secondary particles with a graphite interlayer spacing d. 002 The wavelength range is 0.33560 nm to 0.33610 nm; the graphite B is a primary particle with a graphite interlayer spacing d. 002 The wavelength range is 0.33620 nm to 0.33670 nm; and the mass percentage content of graphite A in the composite artificial graphite is 40% to 90%.

[0006] In some embodiments, the graphite interlayer spacing d of the graphite A 002 The interlayer spacing d of the graphite B can be from 0.33570 nm to 0.33600 nm. 002 It can be 0.33630 nm to 0.33660 nm.

[0007] In some embodiments, the mass percentage content of graphite A in the composite artificial graphite can be 70% to 90%.

[0008] In some embodiments, the volume average particle size D of the composite artificial graphitev 50 can be 11.5 μm ~ 21.5 μm, can be selected from 12.0 μm ~ 20.0 μm, and can be further selected from 12.0 μm ~ 16.0 μm.

[0009] In some embodiments, the number particle size distribution D of the composite artificial graphite n 10 can be 1.3 μm to 6.5 μm, or 2.0 μm to 4.5 μm.

[0010] In some embodiments, the compacted density of the composite artificial graphite powder under 2000 kg pressure can be 1.55 g / cm³. 3 ~ 1.85 g / cm 3 The option is 1.65 g / cm³. 3 ~ 1.80 g / cm 3 .

[0011] In some embodiments, the specific capacity of the composite artificial graphite can be 335 mAh / g or higher, and optionally 342 mAh / g or higher.

[0012] In some embodiments, the volume average particle size D of the graphite A v 50 can be 12.0 μm ~ 22.0 μm, can be selected from 14.0 μm ~ 20.0 μm, and can be further selected from 14.0 μm ~ 16.0 μm.

[0013] In some embodiments, the number particle size distribution D of the graphite A n 10 can be 1.5 μm to 7.5 μm, or 2.5 μm to 4.5 μm.

[0014] In some embodiments, the volume average particle size D of the graphite B v 50 can be 8.0 μm ~ 20.0 μm, and can be selected as 10.0 μm ~ 15.0 μm.

[0015] In some embodiments, the number particle size distribution D of the graphite B n 10 can be 1.2 μm to 6.0 μm, or 1.5 μm to 2.0 μm.

[0016] In some embodiments, the graphitization degree of graphite A can be 91%~97%, and optionally 94%~97%.

[0017] In some embodiments, the graphitization degree of the graphite B can be 85% to 90%, and optionally 86% to 89%.

[0018] A second aspect of this application provides a method for preparing composite artificial graphite, comprising the following steps:

[0019] 1) Preparation of graphite A:

[0020] S11: The raw material 1 is crushed, graded, and shaped to obtain precursor 1;

[0021] S12: Granulate the precursor 1 obtained in step S11 to obtain intermediate 1; optionally, no binder is added or no binder is added during the granulation process, and when a binder is added, the amount of the binder can be 4% to 16% of the weight of the precursor 1 used in granulation step S12;

[0022] S13: The intermediate 1 obtained in step S12 is graphitized at a temperature of 2800℃~3200℃ to obtain graphite A;

[0023] 2) Preparation of graphite B:

[0024] S21: The raw material 2 is crushed, graded, and shaped to obtain precursor 2;

[0025] S22: The precursor 2 obtained in step S21 is graphitized at a temperature of 2500℃~2700℃ to obtain the graphite B;

[0026] 3) Mix the graphite A obtained in step 1) and the graphite B obtained in step 2) uniformly according to the following mass percentage content: 40%~90% graphite A and 10%~60% graphite B, optionally 70%~90% graphite A and 10%~30% graphite B, and further optionally 80%~90% graphite A and 10%~20% graphite B, to obtain the composite artificial graphite, wherein the mass percentage content is relative to the weight of the composite artificial graphite.

[0027] In some embodiments, the graphite A is a secondary particle with a graphite interlayer spacing d. 002 The wavelength range is 0.33560 nm to 0.33610 nm, and can be selected as 0.33570 nm to 0.33600 nm; the graphite B is a primary particle, and its graphite interlayer spacing d 002 The range is 0.33620 nm to 0.33670 nm, and can be selected as 0.33630 nm to 0.33660 nm.

[0028] In some embodiments, raw material 1 may include one or more of needle-shaped raw petroleum coke, non-needle-shaped raw petroleum coke, needle-shaped coal-based raw coke, non-needle-shaped coal-based raw coke, calcined needle-shaped coke, and calcined petroleum coke; raw material 2 may include one or more of needle-shaped raw petroleum coke, non-needle-shaped raw petroleum coke, metallurgical coke, raw pitch coke, needle-shaped coal-based raw coke, non-needle-shaped coal-based raw coke, calcined needle-shaped coke, and calcined petroleum coke.

[0029] In some embodiments, the intermediate 1 obtained in step S12 can be graphitized at a temperature of 3000°C to 3200°C, and the precursor 2 obtained in step S21 can be graphitized at a temperature of 2500°C to 2600°C.

[0030] A third aspect of this application provides a secondary battery comprising a negative electrode sheet, the negative electrode sheet comprising a negative electrode active material, the negative electrode active material comprising composite artificial graphite provided in the first aspect of this application or comprising composite artificial graphite prepared according to the method provided in the second aspect of this application.

[0031] A fourth aspect of this application provides a battery module that includes the secondary battery provided in the third aspect of this application.

[0032] A fifth aspect of this application provides a battery pack that includes the battery module provided in the fourth aspect of this application.

[0033] A sixth aspect of this application provides an electrical device comprising at least one selected from the third aspect of this application, the fourth aspect of this application, or the fifth aspect of this application.

[0034] Beneficial effects

[0035] In the secondary battery provided in this application, the negative electrode active material includes composite artificial graphite, which comprises secondary granular graphite A and primary granular graphite B, wherein the interlayer spacing d of graphite A is... 002 The interlayer spacing d of graphite B is 0.33560 nm to 0.33610 nm. 002The composite artificial graphite, with a wavelength of 0.33620 nm to 0.33670 nm, obtained by mixing the two in a specific ratio, exhibits high specific capacity and low cycle expansion rate. This significantly reduces the volume expansion of secondary batteries containing this composite artificial graphite during cycling (smaller volume expansion during cycling helps maintain a higher volumetric energy density; lower volume expansion also reduces internal stress in the battery cell, minimizing deformation under internal stress and effectively improving battery safety). Furthermore, it possesses high energy density, thereby enhancing both the safety and energy density of the secondary battery. In addition, the low volume expansion of the secondary battery maintains an internal structure suitable for electrolyte wetting during cycling, allowing the electrolyte to fully wet the cell and thus improving cycle life. Simultaneously, the mixing of primary graphite B and secondary graphite A overcomes the shortcomings of individual secondary graphite particles, which typically exhibit poor processing performance and low adhesion to the current collector, making them prone to detachment. The composite artificial graphite obtained by mixing the two has improved processing performance and the advantage of high adhesion to the current collector and resistance to detachment, thereby further improving the service life of the secondary battery. The battery module, battery pack, and power device of this application include the secondary battery provided in this application, and therefore have at least the same advantages as the secondary battery. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of a secondary battery provided in an embodiment of this application.

[0038] Figure 2 This is a schematic diagram of a battery module provided in an embodiment of this application.

[0039] Figure 3 This is a schematic diagram of a battery pack provided in an embodiment of this application.

[0040] Figure 4 yes Figure 3 The exploded diagram.

[0041] Figure 5 This is a schematic diagram of an electrical device provided in an embodiment of this application.

[0042] Figures 6a-6cThe images shown are SEM (scanning electron microscope) images of the composite artificial graphite provided in Examples 1, 2, and 3 of this application, respectively.

[0043] The reference numerals in the attached figures are explained as follows:

[0044] 1. Battery pack;

[0045] 2. Upper box;

[0046] 3. Lower box;

[0047] 4. Battery module;

[0048] 5. Secondary battery. Detailed Implementation

[0049] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the composite artificial graphite and its preparation method, secondary battery, battery module, battery pack, and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for a full understanding of this application by those skilled in the art and are not intended to limit the subject matter of the claims.

[0050] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0051] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0052] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0053] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) 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 it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0054] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0055] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: 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).

[0056] In the description of this article, it should be noted that, unless otherwise stated, "above" and "below" include the number itself, and "several" in "one or several" means two or more.

[0057] Electrical energy, as an economical, practical, clean, and easily controlled and converted form of energy, is increasingly being used in various electrical devices. Rechargeable batteries, due to their advantages such as high energy density, portability, lack of memory effect, and environmental friendliness, have become a preferred power source for these devices. However, rechargeable batteries undergo volume expansion during cycling, leading to increased internal stress and even the risk of battery failure. This also limits the improvement of energy density, thus affecting battery lifespan and safety performance. Therefore, reducing the volume expansion of rechargeable batteries during cycling has become a key focus in the field of rechargeable battery technology.

[0058] Through extensive research, the inventors have noticed that graphite with a lower interlayer spacing d...002 Secondary granular graphite and graphite with high interlayer spacing d 002 Composite artificial graphite obtained by mixing primary particulate graphite in a specific ratio can have both high specific capacity and low expansion rate. It can also reduce the volume expansion of secondary batteries containing this composite artificial graphite during cycling. At the same time, this is also conducive to maintaining a high energy density of secondary batteries, thereby improving the service life and safety performance of secondary batteries, as well as battery modules, battery packs and electrical devices including these secondary batteries.

[0059] Composite Artificial Graphite

[0060] A first aspect of this application provides a composite artificial graphite. The composite artificial graphite includes graphite A and graphite B, wherein graphite A consists of secondary particles with a graphite interlayer spacing d. 002 The wavelength range is 0.33560 nm to 0.33610 nm; the graphite B is a primary particle with a graphite interlayer spacing d. 002 The wavelength range is 0.33620 nm to 0.33670 nm; and the mass percentage content of graphite A in the composite artificial graphite is 40% to 90%.

[0061] The inventors discovered that when the interlayer spacing d of the secondary particle graphite A in the composite artificial graphite... 002 The interlayer spacing d of primary graphite B 002 When the ratio of graphite A to graphite B in the composite artificial graphite is appropriate, the cycling expansion of the composite artificial graphite can be significantly reduced while maintaining high specific capacity. This significantly reduces the volume expansion of the negative electrode and secondary battery containing this composite artificial graphite during cycling. The smaller volume increase of the secondary battery during cycling helps maintain a high energy density. In particular, the low cycling expansion of the secondary battery maintains an internal structure suitable for electrolyte wetting during cycling, ensuring sufficient electrolyte wetting of the cell and thus improving the cycle life. Simultaneously, the lower cycling expansion of the secondary battery also reduces internal stress in the cell, minimizing deformation under internal stress and effectively improving the safety performance of the secondary battery. Therefore, the safety performance and service life of battery modules, battery packs, and electrical devices using this secondary battery are also enhanced.

[0062] In some embodiments, the interlayer spacing d of graphite A in the composite artificial graphite 002 The interlayer spacing d of graphite B can be 0.33570 nm to 0.33600 nm, for example, 0.33580 nm to 0.33600 nm, 0.33570 nm to 0.33590 nm, or 0.33580 nm to 0.33590 nm. 002It can be 0.33630 nm to 0.33660 nm, for example 0.33630 nm to 0.33650 nm, 0.33640 nm to 0.33660 nm, 0.33630 nm to 0.33640 nm, 0.33650 nm to 0.33660 nm.

[0063] In some embodiments, the mass percentage content of graphite A in the composite artificial graphite can be selected as 70% to 90%, for example, 70%, 80%, 85%, 90%, 75% to 90%, 85% to 90%, or 80% to 85%. The mass percentage content of graphite A in the composite artificial graphite can be further selected as 80% to 90%. Using graphite A within this mass percentage range allows the composite artificial graphite to maintain a high specific capacity while enabling the negative electrode sheet and secondary battery containing this composite artificial graphite to have lower volume expansion during cycling, which is more beneficial for improving the energy density and lifespan of the secondary battery.

[0064] In some embodiments, the volume average particle size D of the composite artificial graphite v The thickness of 50 can be 11.5 μm to 21.5 μm, optionally 12.0 μm to 20.0 μm, and further optionally 12.0 μm to 16.0 μm. Appropriate D50 of the composite artificial graphite... v 50 is suitable for achieving high ion and electron transport performance while reducing side reactions of the electrolyte at the negative electrode. It possesses appropriate D... v The 50% composite artificial graphite also helps to improve its own powder compaction density. Using this composite artificial graphite can make the electrode compaction density higher, thereby improving the energy density of the secondary battery.

[0065] In some embodiments, the number particle size distribution D of composite artificial graphite n 10 can range from 1.3 μm to 6.5 μm, for example, the D of composite artificial graphite. n The thickness of 10 can range from 1.5 μm to 6.0 μm, 1.5 μm to 5.0 μm, and 2.0 μm to 4.5 μm. The D-type of composite artificial graphite... n A suitable D10 allows it to possess a high specific capacity. Additionally, a suitable D10 for composite artificial graphite... n 10. This results in a smaller active surface area, thus reducing side reactions between the graphite and the electrolyte, and further minimizing the cycle expansion of the secondary battery. Furthermore, in composite artificial graphite containing an appropriate amount of smaller particles, these smaller particles can fill the pores between the larger particles, giving the composite artificial graphite a higher tap density and powder compaction density. Therefore, the negative electrode sheet using this composite artificial graphite can achieve a higher electrode compaction density, thereby further improving the energy density of the secondary battery.

[0066] In some embodiments, the compacted density of composite artificial graphite powder under 2000 kg pressure can be 1.55 g / cm³. 3 ~ 1.85 g / cm 3 The option is 1.65 g / cm³. 3 ~ 1.80 g / cm 3 When powder compaction is within a suitable range, the compaction density of the negative electrode sheet can be increased, thereby further improving the energy density of the secondary battery.

[0067] In some embodiments, the specific capacity of the composite artificial graphite can be 335 mAh / g or higher, for example, 335 mAh / g to 360 mAh / g, and optionally 342 mAh / g or higher, for example, 342 mAh / g to 360 mAh / g. The higher the specific capacity of the composite artificial graphite, the higher the energy density of the secondary battery containing it. The composite artificial graphite provided in this application has both low cycle expansion and high specific capacity. The combined effect of these two factors enables the secondary battery provided in this application to have both low cycle expansion characteristics and high energy density characteristics.

[0068] In some embodiments, the volume average particle size D of graphite A in the composite artificial graphite v 50 can be 12.0 μm ~ 22.0 μm, optionally 14.0 μm ~ 20.0 μm, and further optionally 14.0 μm ~ 16.0 μm; the number particle size distribution D of graphite A. n 10 can be ≥1.5 μm, selectable from 1.5 μm to 7.5 μm, and further selectable from 2.5 μm to 4.5 μm, for example 1.5 μm, 1.7 μm, 2.0 μm, 2.5 μm, 3.0 μm, 4.0 μm, 5.0 μm, 6.0 μm, 7.5 μm, 1.5 μm to 6.0 μm, 3.0 μm to 4.5 μm. When the number and particle size distribution of secondary graphite A are... n Within the above range, 10 allows graphite A to possess a higher specific capacity, which is beneficial for improving the specific capacity of composite artificial graphite and suppresses the occurrence of cycling side reactions, resulting in smaller volume expansion of the secondary battery during cycling. When the D of graphite A... n When the value is below 10, the presence of more small particles is detrimental to improving the capacity of the composite artificial graphite and will result in more cyclic side reactions, causing the secondary battery to expand in volume during cycling.

[0069] In some embodiments, the volume average particle size D of graphite B in the composite artificial graphite v50 can be 8.0 μm ~ 20.0 μm, or optionally 10.0 μm ~ 15.0 μm. The number particle size distribution D of graphite B. n 10 can be ≥1.2 μm, selectable from 1.2 μm to 6.0 μm, and further selectable from 1.5 μm to 2.0 μm, for example 1.2 μm, 1.5 μm, 1.7 μm, 2.0 μm, 2.5 μm, 3.0 μm, 4.0 μm, 5.0 μm, 6.0 μm, 1.5 μm to 6.0 μm, 1.5 μm to 2.0 μm. When the number of primary graphite particles (B) and their particle size distribution (D) are... n When 10 is within the above range, graphite B can have a higher specific capacity, which is beneficial to improving the specific capacity of composite artificial graphite, and will suppress the occurrence of cycle side reactions, so that the volume expansion of the secondary battery is smaller during the cycle.

[0070] In some embodiments, the graphitization degree of graphite A in the composite artificial graphite can be 91%~97%, optionally 94%~97%; the graphitization degree of graphite B can be 85%~90%, optionally 86%~89%. When the graphitization degrees of graphite A and graphite B are within the above ranges, the composite artificial graphite formed by mixing the two can have a high powder compaction density and specific capacity. In particular, a graphitization degree within the above range also makes the composite artificial graphite less prone to solvent co-intercalation during battery cycling, thus preventing graphite layer delamination and reducing the cycling expansion of the electrode and battery. Simultaneously, the composite artificial graphite exhibits high structural stability and is less prone to disintegration during the rolling process of preparing the negative electrode sheet, resulting in high cohesive force between particles in the electrode sheet, thereby reducing the expansion of the electrode sheet and battery during cycling.

[0071]

Preparation Method

[0072] In a second aspect, this application provides a method for preparing composite artificial graphite, which can prepare any of the above-mentioned composite artificial graphite.

[0073] The embodiments of this application provide a method for preparing composite artificial graphite, which includes the following steps:

[0074] 1) Preparation of graphite A:

[0075] S11: The raw material 1 is crushed, graded, and shaped to obtain precursor 1;

[0076] S12: Granulate the precursor 1 obtained in step S11 to obtain intermediate 1; optionally, no binder is added or no binder is added during the granulation process, and when a binder is added, the amount of the binder is 4% to 16% of the weight of the precursor 1 used in granulation step S12;

[0077] S13: The intermediate 1 obtained in step S12 is graphitized at a temperature of 2800℃~3200℃ to obtain graphite A;

[0078] 2) Preparation of graphite B:

[0079] S21: The raw material 2 is crushed, graded, and shaped to obtain precursor 2;

[0080] S22: The precursor 2 obtained in step S21 is graphitized at a temperature of 2500℃~2700℃ to obtain the graphite B;

[0081] 3) Mix the graphite A obtained in step 1) and the graphite B obtained in step 2) uniformly according to the following mass percentage content: 40%~90% graphite A and 10%~60% graphite B, or optionally 70%~90% graphite A and 10%~30% graphite B, to obtain the composite artificial graphite, wherein the mass percentage content is relative to the weight of the composite artificial graphite.

[0082] In some embodiments, the graphite interlayer spacing d is obtained by steps 1) and 2) of the above preparation method, respectively. 002 The secondary particle graphite A and the graphite interlayer spacing d are 0.33560 nm to 0.33610 nm, and can be selected as 0.33570 nm to 0.33600 nm. 002 The primary particulate graphite B has a wavelength of 0.33620 nm to 0.33670 nm, and may be 0.33630 nm to 0.33660 nm. The composite artificial graphite provided in the first aspect of this application is prepared by mixing the two in a specific ratio.

[0083] In some embodiments, the raw material 1 used to prepare graphite A in step 1) may include one or more of needle-shaped raw petroleum coke, non-needle-shaped raw petroleum coke, needle-shaped coal-based raw coke, non-needle-shaped coal-based raw coke, calcined needle-shaped coke, and calcined petroleum coke. Although metallurgical coke and raw pitch coke are also conventionally used raw materials for preparing artificial graphite, it is difficult to obtain graphite A with the required graphite interlayer spacing when using metallurgical coke and raw pitch coke as raw materials in this invention. The raw material 2 used to prepare graphite B in step 2) may include one or more of needle-shaped raw petroleum coke, non-needle-shaped raw petroleum coke, metallurgical coke, raw pitch coke, needle-shaped coal-based raw coke, non-needle-shaped coal-based raw coke, calcined needle-shaped coke, and calcined petroleum coke. By using the above combination of raw materials for preparing graphite A and graphite B, this application can ensure that the prepared graphite A and graphite B have a preset graphite interlayer spacing d. 002 Furthermore, the composite artificial graphite obtained by mixing the two in a specific ratio can maintain a high specific capacity while effectively reducing the volume expansion of the negative electrode sheet and secondary battery containing the composite artificial graphite during cycling.

[0084] In some embodiments, the raw materials can be crushed using equipment and methods known in the art in steps S11 and S21, such as air jet mills, mechanical mills, or roller mills. The crushing process often produces a large number of excessively small particles, and sometimes excessively large particles as well. Therefore, after crushing, grading can be performed as needed to remove excessively small and excessively large particles from the crushed powder. Grading can yield particulate products with a better particle size distribution, such as D... v The particle size can range from 6.0 μm to 16.5 μm to facilitate subsequent shaping and / or granulation processes. Grading can be performed using equipment and methods known in the art, such as grading sieves, gravity classifiers, centrifugal classifiers, etc.

[0085] In some embodiments, in steps S11 and S21, the particle products obtained after grading can be shaped using equipment (e.g., shaping machines or other shaping equipment) and methods known in the art, such as grinding the edges of the particle products obtained after grading, which facilitates subsequent operations and makes the product obtained after shaping have higher stability.

[0086] In some embodiments, steps S11 and S21 may further include removing fine powder after shaping. By removing fine powder after shaping, the D-value of the shaped particulate product can be controlled. n 10 ≥ 1.2 μm, so that the D of the resulting graphite A and graphite B is... n 10 is within the required range.

[0087] Fine powder can be removed using equipment and methods known in the art, such as classifying sieves, gravity classifiers, centrifugal classifiers, etc.

[0088] In some embodiments, the precursor 1 obtained in step S11 is granulated in step S12 to aggregate the independently dispersed primary particles into secondary particles, thereby obtaining graphite A. During the granulation process, a binder may or may not be used. For example, when the raw material for graphite A is raw petroleum coke with a volatile matter content ≥10% (the volatile matter content of the coke can be tested using methods known in the art, such as referring to SH / T0026-1990), a binder may not be used. When a binder is used, optionally, the amount of binder can be 4% to 16% of the weight of the precursor 1 used in granulation step S12.

[0089] In step S12, granulation can be performed using equipment known in the art, such as a granulator. A granulator typically includes a stirred reactor and a module for temperature control of the reactor. Furthermore, by adjusting process conditions such as stirring speed, heating rate, granulation temperature, and cooling rate during granulation, the volume average particle size of the granulated product (i.e., intermediate 1) can be controlled. Optionally, in this application, the stirring speed during granulation is 800 r / min to 1500 r / min, the heating rate is 8 to 15 °C / min, the granulation temperature is 400 °C to 650 °C, and the granulation time is 6 to 10 hours.

[0090] In some embodiments, the intermediate 1 obtained in step S12 is subjected to high-temperature graphitization treatment in step S13 to obtain graphite A with appropriate graphitization degree and graphite interlayer spacing. In some embodiments, the graphitization treatment temperature in step S13 can be 2800℃~3200℃, for example 2900℃~3100℃, 3000℃~3200℃. Graphite A prepared at an appropriate graphitization temperature can obtain an appropriate graphitization degree and graphite interlayer spacing, thereby enabling the composite artificial graphite to obtain high structural stability and specific capacity, as well as a low cyclic expansion rate.

[0091] In some embodiments, the precursor 2 obtained in step S21 is subjected to low-temperature graphitization in step S22 to obtain graphite B with appropriate graphitization degree and interlayer spacing. In some embodiments, the graphitization temperature in step S22 can be 2500℃~2700℃, for example 2500℃~2600℃ or 2600℃~2700℃. Graphite B prepared at an appropriate graphitization temperature can obtain appropriate graphitization degree and interlayer spacing, thereby enabling the composite artificial graphite to achieve high structural stability and specific capacity, as well as low cyclic expansion rate.

[0092] In this application, the graphite interlayer spacing d 002 The degree of graphitization can be tested using methods known in the art. For example, the degree of graphitization can be tested using an X-ray diffractometer (such as a Bruker D8 Discover), and the testing method can be referenced in JIS K 0131-1996 and JB / T 4220-2011 to measure d. 002 The size is then determined according to the formula G=(0.344-d). 002 The degree of graphitization is calculated using (0.344-0.3354) / (0.344-0.3354), where d 002 It is the interlayer spacing in the artificial graphite crystal structure, expressed in nanometers (nm).

[0093] In this application, the D of graphite n 10. D v50 can be determined using a laser particle size analyzer (such as Malvern Master Size 3000) in accordance with standard GB / T 19077.1-2016.

[0094] Among them, D n 10. D v The physical definition of 50 is as follows:

[0095] D n 10: The particle size corresponding to a cumulative percentage of graphite reaching 10%;

[0096] D v 50: The particle size corresponding to a cumulative volumetric distribution percentage of graphite reaching 50%.

[0097] In this application, the tap density of graphite can be tested using methods known in the art. For example, it can be tested using a powder tap density tester (such as Dandong Baite BT-301) in accordance with standard GB / T 5162-2006.

[0098] In this application, the compaction density of graphite powder can be tested using methods known in the art. For example, referring to GB / T 24533-2009, an electronic pressure testing machine (such as UTM7305) can be used for testing: a certain amount of powder is placed on a special compaction mold, different pressures are set, and the thickness of the powder under different pressures can be read on the equipment, and the compaction density under different pressures can be calculated.

[0099] Rechargeable batteries

[0100] A third aspect of this application provides a secondary battery comprising any composite artificial graphite provided in the first aspect of the invention or any composite artificial graphite prepared by the method provided in the second aspect of the invention.

[0101] This application provides a secondary battery in its embodiments. Typically, a secondary battery includes a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions repeatedly insert and extract between the positive and negative electrodes. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator is disposed between the positive and negative electrodes, primarily to prevent short circuits between the positive and negative electrodes while allowing ions to pass through.

[0102] [Negative electrode plate]

[0103] The negative electrode includes a negative current collector and a negative electrode film disposed on at least one surface of the negative current collector. As an example, the negative current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film is laminated and disposed on either or both of the two opposite surfaces of the negative current collector.

[0104] The negative electrode current collector can be made of a material with good conductivity and mechanical strength, serving both as a conductor and a current collector. In some embodiments, the negative electrode current collector can be made of copper foil.

[0105] The negative electrode film includes a negative electrode active material, which includes any of the composite artificial graphite provided in the first aspect of this application. This significantly reduces the volume expansion of the negative electrode sheet comprising composite artificial graphite during cycling. Lower volume expansion not only helps the secondary battery maintain a high volumetric energy density but also helps reduce the internal stress within the battery cell, minimizing cell deformation under internal stress and effectively improving the safety performance of the secondary battery.

[0106] In some embodiments, the steps of preparing a negative electrode sheet using any one or more composite artificial graphite materials of this application may include: dispersing a negative electrode active material including any one or more composite artificial graphite materials of this application, a binder, and optional thickeners and conductive agents in a solvent, the solvent being deionized water, to form a uniform negative electrode slurry; coating the negative electrode slurry onto a negative electrode current collector, and obtaining a negative electrode sheet after processes such as drying and cold pressing.

[0107] In some embodiments, the negative electrode sheet may optionally include other negative electrode active materials that can be used as the negative electrode of a secondary battery. Other negative electrode active materials may be one or more of other graphite materials (such as other artificial graphite, natural graphite), mesophase microcarbon spheres (MCMB), hard carbon, soft carbon, silicon-based materials, and tin-based materials.

[0108] In some embodiments, the adhesive may be selected from one or more of polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), styrene-butadiene rubber (SBR), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0109] In some embodiments, the thickener may be sodium carboxymethyl cellulose (CMC-Na).

[0110] In some embodiments, the conductive agent used for the negative electrode sheet may be selected from one or more of graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0111] [Positive electrode plate]

[0112] The positive electrode includes a positive current collector and a positive electrode film disposed on at least one surface of the positive current collector and comprising a positive active material. As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film is laminated on either or both of the two opposite surfaces of the positive current collector.

[0113] The positive current collector can be made of a material with good conductivity and mechanical strength. In some embodiments, the positive current collector can be aluminum foil.

[0114] This application does not impose specific restrictions on the type of positive electrode active material. Materials known in the art that can be used as positive electrodes for secondary batteries can be used, and those skilled in the art can select them according to actual needs.

[0115] In some embodiments, the secondary battery may be a lithium-ion secondary battery. The positive electrode active material may be selected from lithium transition metal oxides and their modified materials, wherein the modified material may be a lithium transition metal oxide that has undergone doping modification and / or coating modification. For example, the lithium transition metal oxide may be selected from one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and lithium phosphates with an olivine structure.

[0116] As an example, the positive electrode active material of a secondary battery can be selected from LiCoO2, LiNiO2, LiMnO2, LiMn2O4, and LiNi. 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.85 Co 0.15 Al 0.05 One or more of O2, LiFePO4 (LFP), and LiMnPO4.

[0117] In some embodiments, the positive electrode membrane may optionally include an adhesive. There is no specific limitation on the type of adhesive, and those skilled in the art can select one according to actual needs. As an example, the adhesive used for the positive electrode membrane may include one or more of polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE).

[0118] In some embodiments, the positive electrode membrane may optionally include a conductive agent. There is no specific limitation on the type of conductive agent, and those skilled in the art can select it according to actual needs. As an example, the conductive agent used for the positive electrode membrane may include one or more of graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0119] [Electrolytes]

[0120] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0121] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0122] In some embodiments, the electrolyte salt may be selected from one or more of LiPF6 (lithium hexafluorophosphate), LiBF4 (lithium tetrafluoroborate), LiClO4 (lithium perchlorate), LiAsF6 (lithium hexafluoroarsenate), LiFSI (lithium bis(fluorosulfonyl)imide), LiTFSI (lithium bis(trifluoromethanesulfonyl)imide), LiTFS (lithium trifluoromethanesulfonate), LiDFOB (lithium difluorooxalate borate), LiBOB (lithium dioxalate borate), LiPO2F2 (lithium difluorophosphate), LiDFOP (lithium difluorodioxalate phosphate), and LiTFOP (lithium tetrafluorooxalate phosphate).

[0123] In some embodiments, the solvent may be selected from one or more of ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl 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).

[0124] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, additives that improve battery low-temperature performance, etc.

[0125] [Isolation membrane]

[0126] Secondary batteries using electrolytes, and some secondary batteries using solid electrolytes, also include a separator. The separator is positioned between the positive and negative electrodes to provide isolation. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected. In some embodiments, the separator material can be selected from one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer can be the same or different.

[0127] [Outer Packaging]

[0128] In some embodiments, the secondary battery may include an outer packaging for encapsulating a positive electrode, a negative electrode, and an electrolyte. As an example, the positive electrode, negative electrode, and separator may be stacked or wound to form a stacked or wound battery cell, with the cell encapsulated within the outer packaging; the electrolyte may be a liquid electrolyte that wets the cell. The number of cells in the secondary battery may be one or more, adjustable as needed.

[0129] In some embodiments, the outer packaging of the secondary battery can be a soft pack, such as a pouch. The soft pack can be made of plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS). The outer packaging of the secondary battery can also be a hard shell, such as an aluminum shell.

[0130] In some embodiments, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly by a winding process or a stacking process.

[0131] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. Figure 1 This is an example of a square-structured secondary battery 5.

[0132] Battery Module

[0133] In a fourth aspect of this application, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be multiple, the specific number of which can be adjusted according to the application and capacity of the battery module.

[0134] Figure 2 This is battery module 4, used as an example. (See reference...) Figure 2 In battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0135] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0136] Battery Pack

[0137] In a fifth aspect of this application, the battery module provided in the fourth aspect of this application can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0138] Figure 3 and Figure 4 This is battery pack 1 as an example. (See reference...) Figure 3 and Figure 4 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0139] Electrical appliances

[0140] The sixth aspect of this application also provides an electrical device comprising a secondary battery according to the third aspect of this application, wherein the secondary battery provides power to the electrical device. The electrical device may be, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0141] The electrical device can be equipped with a secondary battery, battery module, or battery pack according to its usage requirements.

[0142] Figure 5 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0143] Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use rechargeable batteries as their power source.

[0144] Example

[0145] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0146] [Performance Testing]

[0147] (1) Specific capacity test of composite artificial graphite

[0148] The prepared composite artificial graphite, conductive agent SuperP, thickener (CMC-Na), and binder (SBR) were mixed with deionized water in a mass ratio of 94.5:1.5:1.5:2.5 to form a slurry. The prepared slurry was coated onto a copper foil current collector and dried in an oven for later use. A lithium metal sheet was used as the counter electrode. A polyethylene (PE) film was used as the separator. Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1. LiPF6 was then uniformly dissolved in the above solution to obtain an electrolyte with a concentration of 1 mol / L. The above components were assembled into a CR2430 coin cell in an argon-protected glove box.

[0149] After the obtained coin cells were left to stand for 12 hours, they were discharged at a constant current of 0.05C to 0.005V, left to stand for 10 minutes, and then discharged at a constant current of 10μA to 0.005V. They were then charged at a constant current of 0.1C to 2V, and the charging capacity was recorded. The ratio of the charging capacity to the mass of the composite artificial graphite is the specific capacity of the prepared composite artificial graphite.

[0150] (2) Cyclic expansion rate test of negative electrode sheet

[0151] The thickness of the cold-pressed negative electrode sheet is denoted as H0. The cold-pressed negative electrode sheet, along with the positive electrode sheet, separator, and electrolyte, is used to construct a secondary battery. At 45°C, the secondary battery is subjected to 1C / 1C cycles at 100% DOD (100% depth of discharge, i.e., full charge followed by full discharge) using a Newway charge / discharge machine. The discharge capacity of the first cycle (i.e., the initial capacity) is denoted as 100%. The cycle is stopped when the cycle capacity retention rate reaches 80% of the initial capacity. The secondary battery is then charged to 100% SOC (State of Charge), disassembled, and the thickness of the corresponding negative electrode sheet is measured and denoted as H1. The cycle expansion rate of the negative electrode sheet is then: (H1 / H0-1)×100%.

[0152] (3) Cyclic capacity retention

[0153] A charge-discharge test was conducted on a lithium-ion battery at 45℃. One charge-discharge cycle was as follows: constant current charging at 1C to 4.3V, then constant voltage charging at 4.3V to 0.05C, resting for 5 minutes, and then constant current discharging at 1C to 2.8V. The battery capacity at this point was recorded as C1. This constitutes one charge-discharge cycle. This process was repeated 1200 times, and the battery capacity C1200 was recorded. Therefore, the cycle capacity retention rate = C1200 / C1 × 100%.

[0154] Example 1

[0155] Preparation of composite artificial graphite

[0156] 1) Preparation of graphite A:

[0157] S11: The calcined needle coke is crushed to D by roller mill. v The particle size was 10.0 μm, and the sample was shaped and de-powdered to obtain precursor 1;

[0158] S12: Add precursor 1 obtained in step S11 to the reactor, and add 12% (by weight of binder asphalt) of the precursor 1 used for granulation for granulation. Stir at 1200 r / min, heat to 560℃ at a rate of 10℃ / min at room temperature, and hold at that temperature for 8 hours until granulation reaches D. v 50 is 17.2 μm, thus intermediate 1 is obtained;

[0159] S13: Add intermediate 1 obtained in step S12 to a graphitization furnace and heat to 3000℃ for high-temperature graphitization to obtain D. v 50 is 15.6 μm graphite A, which is a secondary particle with a graphite interlayer spacing d. 002 As shown in Table 1 below.

[0160] 2) Preparation of graphite B:

[0161] S21: The needle-shaped raw petroleum coke is crushed to D using a mechanical mill. v The particle size of 50 was 11.2 μm, and after shaping and de-fine powder removal, precursor 2 was obtained;

[0162] S22: Add the precursor 2 obtained in step S21 to a graphitization furnace and heat to 2500℃ for low-temperature graphitization to obtain D. v 50 represents 10.0 μm graphite B, which is a primary particle with a graphite interlayer spacing d. 002 As shown in Table 1 below.

[0163] 3) Preparation of composite graphite: Graphite A and graphite B were mixed evenly at a mass ratio of 75%:25% to obtain composite artificial graphite. The specific gravity of the composite artificial graphite is shown in Table 2 below. The SEM image of the composite artificial graphite is shown below. Figure 6a As shown. Figure 6a As shown, primary granular graphite B is a single block-shaped particle; secondary granular graphite A is composed of two or more block-shaped particles bonded together.

[0164] Preparation of negative electrode sheet

[0165] The composite artificial graphite, conductive agent (Super P), binder (SBR), and thickener (CMC-Na) prepared above were thoroughly mixed in an appropriate amount of deionized water at a mass ratio of 96.2:0.8:1.8:1.2 to form a uniform negative electrode slurry. The negative electrode slurry was then coated onto the surface of a copper foil current collector, and after drying and cold pressing, a negative electrode sheet was obtained. The compacted density of the negative electrode sheet was 1.65 g / cm³. 3 Its surface density is 10.7 mg / cm³. 2 The results of the cycle expansion rate of the negative electrode and the cycle capacity retention rate of the secondary battery are shown in Table 2 below.

[0166] Preparation of positive electrode sheet

[0167] LiNi, the positive electrode active material 0.5 Co 0.2 Mn 0.3 O2 (NCM523), conductive agent (Super P), and binder PVDF are thoroughly mixed in an appropriate amount of NMP at a weight ratio of 96.2:2.7:1.1 to form a uniform positive electrode slurry. The positive electrode slurry is then coated onto the surface of a positive electrode current collector aluminum foil, dried, and cold-pressed to obtain the positive electrode sheet. The compacted density of the positive electrode sheet is 3.45 g / cm³. 3 Its surface density is 18.8 mg / cm³. 2 .

[0168] Preparation of electrolyte

[0169] Ethyl carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1, and then LiPF6 was uniformly dissolved in the above solution to obtain an electrolyte with a concentration of 1 mol / L.

[0170] Separating membrane

[0171] Polyethylene (PE) film is used.

[0172] Preparation of secondary batteries

[0173] The positive electrode, separator, and negative electrode are stacked in sequence and wound to obtain a battery cell. The battery cell is then placed in an outer packaging, and the electrolyte mentioned above is added. After processes such as encapsulation, settling, formation, and aging, a secondary battery is obtained. The outer packaging is a hard shell with a length * width * height of 148mm * 28.5mm * 97.5mm.

[0174] Examples 2-11

[0175] Examples 2-5 are prepared using methods similar to Example 1, except that the raw materials and graphitization temperature for preparing graphite A and graphite B are adjusted. The process parameters for each example, as well as the test results of the physical parameters of graphite A and graphite B, are shown in Table 1 below. The specific capacity test results of the obtained composite artificial graphite, the cycle expansion rate test results of the negative electrode sheet, and the cycle capacity retention rate results of the secondary battery are shown in Table 2 below. Figure 6b , Figure 6c The images are SEM images from Examples 2 and 3, respectively.

[0176] Examples 6-11 are prepared similarly to Example 1, except that the mixing mass ratio of graphite A and graphite B is adjusted to 90%:10%, 80%:20%, 70%:30%, 60%:40%, 50%:50%, and 40%:60%, respectively. The process parameters for each example and the test results of the physical parameters of graphite A and graphite B are shown in Table 1 below. The specific capacity test results of the obtained composite artificial graphite, the cycle expansion rate test results of the negative electrode sheet, and the cycle capacity retention rate results of the secondary battery are shown in Table 2 below.

[0177] Comparative Examples 1-14

[0178] The preparation methods of Comparative Examples 1-4 are similar to those of Example 1, except that the preparation process parameters of graphite B are adjusted to obtain different composite artificial graphites. The process parameters of each comparative example, as well as the test results of the physical parameters of graphite A and graphite B, are shown in Table 1 below. The specific capacity test results of the obtained composite artificial graphite, the cycle expansion rate test results of the negative electrode sheet, and the cycle capacity retention rate results of the secondary battery are shown in Table 2 below. Specifically, the raw materials for preparing graphite B in Comparative Examples 1-4 are needle-shaped raw petroleum coke, calcined petroleum coke, or calcined needle-shaped coke; by adjusting the graphitization temperature, different primary particles are obtained.

[0179] Comparative Examples 5-8 were prepared using methods similar to Example 1, except that the graphite raw materials, preparation process parameters, and mixing ratios were adjusted to obtain different composite artificial graphites. The process parameters of each comparative example, as well as the test results of the physical parameters of graphite A and graphite B, are shown in Table 1 below. The specific capacity test results of the obtained composite artificial graphite, the cycle expansion rate test results of the secondary battery, and the cycle capacity retention rate results of the secondary battery are shown in Table 2 below.

[0180] Specifically, in Comparative Example 5, the raw material for preparing graphite A was raw pitch coke. By adjusting the graphitization temperature, secondary particles with larger interlayer spacing were obtained. The raw material for preparing graphite B was also raw pitch coke, resulting in primary particles with relatively large interlayer spacing.

[0181] In Comparative Example 6, the raw material for preparing graphite A was needle-shaped raw petroleum coke. No binder, pitch, was added during granulation. The graphitization temperature was adjusted to obtain secondary particles with relatively large interlayer spacing. The raw material for preparing graphite B was also needle-shaped raw petroleum coke, resulting in primary particles with relatively large interlayer spacing. The mixing ratio of graphite A and graphite B was adjusted to 60%:40%.

[0182] In Comparative Example 7, the raw material for preparing graphite A was needle-shaped raw petroleum coke. No binder, pitch, was added during granulation. The graphitization temperature was adjusted to obtain secondary particles with relatively large interlayer spacing. The raw material for preparing graphite B was calcined needle-shaped coke, resulting in primary particles with relatively large interlayer spacing. The mixing ratio of graphite A and graphite B was adjusted to 50%:50%.

[0183] In Comparative Example 8, the raw material for preparing graphite A was needle-shaped raw petroleum coke. By adjusting the graphitization temperature, secondary particles with larger interlayer spacing were obtained. The raw material for preparing graphite B was needle-shaped raw petroleum coke, resulting in primary particles with larger interlayer spacing. The mixing ratio of graphite A and graphite B was adjusted to 40%:60%.

[0184] Comparative Examples 9 and 10 were prepared using methods similar to those in Example 1, except that the mixing ratio of graphite A and graphite B was adjusted to obtain different composite artificial graphites. The process parameters of each comparative example, as well as the test results of the physical parameters of graphite A and graphite B, are shown in Table 1 below. The specific capacity test results of the obtained composite artificial graphite, the cycle expansion rate test results of the negative electrode sheet, and the cycle capacity retention rate results of the secondary battery are shown in Table 2 below.

[0185] Specifically, in Comparative Example 9, the mixing ratio of graphite A and graphite B was adjusted to 95%:5%.

[0186] In Comparative Example 10, the mixing ratio of graphite A and graphite B was adjusted to 30%:70%.

[0187] Comparative Examples 11-12 were prepared using methods similar to Example 1, except that the same raw materials and graphitization temperatures were used to prepare graphite A and graphite B to obtain different composite artificial graphites. The process parameters of each comparative example and the test results of the physical parameters of graphite A and graphite B are shown in Table 1 below. The specific capacity test results of the obtained composite artificial graphite, the cycle expansion rate test results of the negative electrode sheet, and the cycle capacity retention rate of the secondary battery are shown in Table 2 below.

[0188] Specifically, in Comparative Example 11, the raw materials for preparing graphite A and graphite B were both needle-shaped raw petroleum coke, and the graphitization temperature was 2700℃.

[0189] In Comparative Example 12, the raw materials for preparing graphite A and graphite B were both calcined needle coke, and the graphitization temperature was 3000℃.

[0190] Comparative Examples 13-14 were prepared in a similar manner to Example 1, except that the raw material of graphite A was adjusted to obtain different composite artificial graphites. The process parameters of each comparative example and the test results of the physical parameters of graphite A and graphite B are shown in Table 1 below. The specific capacity test results of the obtained composite artificial graphite, the cycle expansion rate test results of the negative electrode sheet, and the cycle capacity retention rate of the secondary battery are shown in Table 2 below.

[0191] Specifically, in Comparative Example 13, the raw material for preparing graphite A was metallurgical coke; in Comparative Example 14, the raw material for preparing graphite A was raw pitch coke.

[0192] Table 1: Test results of process and physical parameters of Examples 1-11 and Comparative Examples 1-14

[0193]

[0194] Table 2: Performance test results of Examples 1-11 and Comparative Examples 1-14

[0195]

[0196] As can be seen from the comparison of Examples 1-11 and Comparative Examples 1-14 shown in Tables 1 and 2 above, when secondary particulate graphite A with a smaller interlayer spacing and primary particulate graphite B with a larger interlayer spacing are mixed in a specific ratio, the resulting composite artificial graphite has a higher specific capacity. At the same time, it can effectively reduce the expansion rate of the negative electrode sheet during cycling. Thus, while maintaining the high energy density of the secondary battery, it can effectively reduce the volume expansion of the secondary battery during cycling. The reduced volume expansion is conducive to the secondary battery having a higher energy density, thereby effectively improving the service life and safety performance of the secondary battery.

[0197] In Comparative Examples 1-4, both graphite A and graphite B were prepared at relatively high graphitization temperatures. Although the resulting composite artificial graphite had a high specific capacity, the negative electrode sheet had a large expansion rate during cycling, which severely degraded its cycle performance and was detrimental to the service life of the secondary battery.

[0198] In Comparative Examples 5-8, both graphite A and graphite B were prepared at relatively low graphitization temperatures. Although the resulting composite artificial graphite could effectively reduce the expansion rate of the electrode during cycling after being used to prepare the negative electrode sheet, the specific capacity of the composite artificial graphite was low and the powder compaction density was low, which would significantly reduce the energy density of the secondary battery.

[0199] In Comparative Example 9, the ratio of graphite A to graphite B was 95%:5%. At this point, the content of secondary granular graphite A was too high. Although the specific capacity of the obtained composite artificial graphite was high, it would lead to poor processing performance, low adhesion, and easy demolding of the composite artificial graphite, resulting in the failure of the expansion rate test of the negative electrode sheet during the cycle.

[0200] In Comparative Example 10, the ratio of graphite A to graphite B content is 30%:70%. At this time, the content of primary granular graphite B is too high, which will lead to a larger expansion rate of the negative electrode sheet during cycling. It will also reduce the specific capacity of the composite artificial graphite, thereby degrading the energy density of the secondary battery.

[0201] In Comparative Examples 11-12, graphite A and graphite B used the same raw materials and graphitization conditions. Although the specific capacity of the obtained composite artificial graphite met the requirements, the expansion rate of the negative electrode sheet during cycling was too large.

[0202] In Comparative Examples 13-14, the raw materials used to prepare graphite A were metallurgical coke and raw pitch coke. The secondary particulate graphite obtained from this raw material has a low specific capacity. Although the composite artificial graphite obtained can reduce the expansion rate of the electrode during cycling after being used to prepare the negative electrode sheet, the specific capacity of the composite artificial graphite is low and the powder compaction density is low, which will significantly reduce the energy density of the secondary battery.

[0203] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A composite artificial graphite comprising graphite A and graphite B, wherein: The graphite A is a secondary particle with a graphite interlayer spacing d002 of 0.33560 nm to 0.33610 nm. The graphite B is a primary particle with a graphite interlayer spacing d002 of 0.33620 nm to 0.33670 nm; and The graphite A in the composite artificial graphite has a mass percentage content of 60% to 90%. The graphitization degree of graphite A is 91%~97%; The graphitization degree of graphite B is 85%~90%.

2. The composite artificial graphite according to claim 1, wherein, The interlayer spacing d002 of the graphite A is 0.33570 nm to 0.33600 nm.

3. The composite artificial graphite according to claim 1, wherein, The interlayer spacing d002 of the graphite B is 0.33630 nm to 0.33660 nm.

4. The composite artificial graphite according to claim 1, wherein, The volume average particle size Dv50 of the composite artificial graphite is 11.5 μm ~ 21.5 μm.

5. The composite artificial graphite according to claim 4, wherein, The volume average particle size Dv50 of the composite artificial graphite is 12.0 μm ~ 20.0 μm.

6. The composite artificial graphite according to claim 5, wherein, The volume average particle size Dv50 of the composite artificial graphite is 12.0 μm ~ 16.0 μm.

7. The composite artificial graphite according to claim 1, wherein, The particle size distribution Dn10 of the composite artificial graphite is 1.3 μm to 6.5 μm.

8. The composite artificial graphite according to claim 7, wherein, The particle size distribution Dn10 of the composite artificial graphite is 2.0 μm to 4.5 μm.

9. The composite artificial graphite according to claim 1, wherein, The compacted density of the composite artificial graphite powder under 2000 kg pressure is 1.55 g / cm³. 3 ~ 1.85 g / cm 3 .

10. The composite artificial graphite according to claim 9, wherein, The compacted density of the composite artificial graphite powder under 2000 kg pressure is 1.65 g / cm³. 3 ~ 1.80 g / cm 3 .

11. The composite artificial graphite according to claim 1, wherein, The specific capacity of the composite artificial graphite is above 335 mAh / g.

12. The composite artificial graphite according to claim 11, wherein, The specific capacity of the composite artificial graphite is above 342 mAh / g.

13. The composite artificial graphite according to claim 1, wherein, The volume average particle size Dv50 of the graphite A is 12.0 μm ~ 22.0 μm; and / or, The number and particle size distribution Dn10 of the graphite A is 1.5 μm to 7.5 μm; and / or, The volume average particle size Dv50 of the graphite B is 8.0 μm to 20.0 μm; and / or, The number of graphite B particles with a particle size distribution Dn10 is 1.2 μm to 6.0 μm.

14. The composite artificial graphite according to claim 13, wherein, The volume average particle size Dv50 of the graphite A is 14.0 μm ~ 20.0 μm; and / or, The number and particle size distribution Dn10 of the graphite A is 2.5 μm to 4.5 μm; and / or, The volume average particle size Dv50 of the graphite B is 10.0 μm ~ 15.0 μm; and / or, The number of graphite B particles with a particle size distribution Dn10 is 1.5 μm to 2.0 μm.

15. The composite artificial graphite according to claim 1, wherein, The graphitization degree of graphite A is 94%~97%; and / or, The graphitization degree of graphite B is 86%~89%.

16. The composite artificial graphite according to claim 1, wherein, The mass percentage content of graphite A in the composite artificial graphite is 70% to 90%.

17. A method for preparing composite artificial graphite, comprising the following steps: 1) Preparation of graphite A: S11: The raw material 1 is crushed, graded, and shaped to obtain precursor 1; S12: Granulate the precursor 1 obtained in step S11 to obtain intermediate 1; S13: The intermediate 1 obtained in step S12 is graphitized at a temperature of 2800℃~3200℃ to obtain graphite A; the graphite A is a secondary particle with a graphite interlayer spacing of 0.33560 nm~0.33610 nm. 2) Preparation of graphite B: S21: The raw material 2 is crushed, graded, and shaped to obtain precursor 2; S22: The precursor 2 obtained in step S21 is graphitized at a temperature of 2500℃~2700℃ to obtain graphite B; the graphite B is a primary particle with a graphite interlayer spacing of 0.33620 nm~0.33670 nm. 3) Mix the graphite A obtained in step 1) and the graphite B obtained in step 2) uniformly according to the following mass percentage: 60%~90% graphite A and 10%~40% graphite B, to obtain the composite artificial graphite, wherein the mass percentage is relative to the weight of the composite artificial graphite. The graphite A has a graphitization degree of 91%~97%, and the graphite B has a graphitization degree of 85%~90%.

18. The preparation method according to claim 17, wherein, In step S12, no binder is added or no binder is added during the granulation process, and when a binder is added, the amount of binder is 4% to 16% of the weight of the precursor 1 used in granulation step S12; and / or In step S13, the interlayer spacing of graphite A is 0.33570 nm to 0.33600 nm; and / or In step S22, the graphite interlayer spacing of graphite B is 0.33630 nm to 0.33660 nm.

19. The preparation method according to claim 17, wherein, The raw material 1 includes one or more of the following: needle-shaped raw petroleum coke, non-needle-shaped raw petroleum coke, needle-shaped coal-based raw coke, non-needle-shaped coal-based raw coke, calcined needle-shaped coke, and calcined petroleum coke. The raw material 2 includes one or more of the following: needle-shaped raw petroleum coke, non-needle-shaped raw petroleum coke, metallurgical coke, raw pitch coke, needle-shaped coal-series raw coke, non-needle-shaped coal-series raw coke, calcined needle-shaped coke, and calcined petroleum coke.

20. The preparation method according to claim 17, wherein, The intermediate 1 is graphitized at a temperature of 3000℃~3200℃, and the precursor 2 is graphitized at a temperature of 2500℃~2600℃.

21. A secondary battery comprising a negative electrode sheet, the negative electrode sheet comprising a negative electrode active material, the negative electrode active material comprising composite artificial graphite according to any one of claims 1-16 or comprising composite artificial graphite prepared by any one of claims 17-20.

22. A battery module comprising the secondary battery of claim 21.

23. A battery pack comprising the battery module of claim 22.

24. An electrical device comprising at least one selected from the secondary battery of claim 21, the battery module of claim 22, or the battery pack of claim 23.

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