Negative electrode active material, method for producing the same, secondary battery, battery module including secondary battery, battery pack, and device

Abstract

To provide secondary batteries with good fast-charging performance.SOLUTION: This application provides a negative-electrode active material and a preparation method thereof, a secondary battery, and a battery module, a battery pack and an apparatus that comprise the secondary battery. The negative-electrode active material comprises: a core containing artificial graphite; and a coating layer covering at least part of a surface of the core and containing amorphous carbon. The negative-electrode active material has a volume-based particle size distribution satisfying Dv99≤24 μm, and an average volume-based particle size Dv50 satisfying 8 μm≤Dv50≤15 μm, where Dv99 is a particle size corresponding to a cumulative volume distribution percentage of the negative-electrode active material reaching 99%, and Dv50 is a particle size corresponding to a cumulative volume distribution percentage of the negative-electrode active material reaching 50%.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present application belongs to the secondary battery technical field, and specifically relates to a negative electrode active material, a method for producing the same, a secondary battery, a battery module including the secondary battery, a battery pack, and an apparatus. [Background technology]

[0002] Secondary batteries are charged and discharged by the shuttle of active ions between the positive and negative electrodes, and have outstanding features such as high energy density, long cycle life, no pollution, no memory effect, etc. Therefore, as a clean energy source, secondary batteries are widely used in fields ranging from electronic products to large-scale devices such as electric vehicles, and are in line with environmental and energy sustainable development strategies.

[0003] However, while conventional fuel-powered vehicles require fast and timely refueling, electric vehicles generally require a low charging rate, which in turn requires long charging times, causing users to worry about the driving range and limiting the rapid adoption of electric vehicles. Therefore, in order to improve the market competitiveness of electric vehicles, it is necessary to provide a secondary battery with good fast charging performance. Summary of the Invention

[0004] The present application aims to provide a negative electrode active material that improves the charging performance and cycle performance of a secondary battery, a method for producing the same, a secondary battery, a battery module including the secondary battery, a battery pack, and a device.

[0005] In order to achieve the above object of the invention, a first aspect of the present application provides a composite particle having a core containing artificial graphite and a coating layer containing amorphous carbon that coats at least a part of the surface of the core, the composite particle having a volume particle size distribution D v 99≦24 μm and average volume particle size D v 50 is 8μm≦D v Provide a negative electrode active material that satisfies the requirement of 50≦15 μm. v 99 is the particle size corresponding to the cumulative volume distribution percentage of the negative electrode active material reaching 99%, and D v50 is the particle size corresponding to when the cumulative volume distribution percentage of the negative electrode active material reaches 50%.

[0006] Surprisingly, it was found that the negative plate using the negative active material of the present invention exhibits high solid-state diffusion of active ions. Even in a highly lithium-loaded state at the end of charging, the active ions can diffuse rapidly in the negative plate, effectively reducing ohmic and concentration polarization, thereby significantly increasing the charging rate and depth of charge of the entire negative plate and significantly improving the rapid charging capability of the battery. Furthermore, the cycle performance of the battery is also significantly improved.

[0007] In any embodiment of the present application, the negative electrode active material has a thickness of 17 μm≦D v 99≦24 μm, and optionally, 18 μm≦D v 99≦21μm. v When 99 is within the above range, the rapid charging ability and cycle performance of the battery can be further improved.

[0008] In any embodiment of the present application, the negative electrode active material has a thickness of 9 μm≦D v 50≦13 μm, and optionally, 11 μm≦D v 50≦13μm. v When 50 is within the appropriate range, the rapid charging ability and cycle performance of the battery can be further improved.

[0009] In any embodiment of the present application, the particle size uniformity of the negative electrode active material is 0.25 to 0.45, and preferably 0.32 to 0.38. When the particle size uniformity of the negative electrode active material is within this range, the rapid charging capability of the battery can be further improved, and the negative electrode plate can be provided with a high compaction density, thereby improving the energy density of the battery.

[0010] In any embodiment of the present application, the particle size-specific surface area of ​​the negative electrode active material is 0.4 m 2 / g~0.75m 2 / g, preferably 0.5m2 / g~0.65m 2 When the particle size-specific surface area of ​​the negative electrode active material is within the appropriate range, the rapid charging performance and cycle performance of the battery can be further improved, and the energy density of the battery can also be improved.

[0011] In any embodiment of the present application, the negative electrode active material contains secondary particles, and the number ratio of the secondary particles in the negative electrode active material is 50% or more. Optionally, the number ratio of the secondary particles in the negative electrode active material is 70% to 95%. When the negative electrode active material contains an appropriate amount of secondary particles, the rapid charging capability, cycle performance, and storage performance of the battery can be further improved.

[0012] In any embodiment of the present application, the negative electrode active material has a capacitance of 0.6≦(D v 90-D v 10) / D v 50≦1.8, and optionally, 0.8≦(D v 90-D v 10) / D v 50≦1.4. D v 90 is the particle size corresponding to when the cumulative volume distribution percentage of the negative electrode active material reaches 90%, and D v 10 is the particle size corresponding to the cumulative volume distribution percentage of the negative electrode active material reaching 10%. v 90-D v 10) / D v The appropriate value of 50 is advantageous for further improving the rapid charging capability of the battery.

[0013] In any embodiment of the present application, the volume particle size distribution D v 90 is 13 μm to 18 μm, and optionally 14 μm to 17 μm. v If 90 is within the above range, the rapid charging capability of the battery can be further improved.

[0014] In any embodiment of the present application, the volume particle size distribution D v10 is 5 μm to 10 μm, and optionally 6 μm to 8 μm. v If 10 is within the above range, it is advantageous for improving the cycle performance and storage performance of the battery.

[0015] In any embodiment of the present application, the graphitization degree of the negative electrode active material is 91.0% to 96.0%, and preferably 94.0% to 95.0%. When the graphitization degree of the negative electrode active material is within the above range, the rapid charging capability of the battery can be further improved.

[0016] In any embodiment of the present application, the gram capacity of the negative electrode active material is 345 mAh / g to 360 mAh / g, and preferably 350 mAh / g to 358 mAh / g. When the gram capacity of the negative electrode active material is within an appropriate range, the energy density of the battery can be improved, and the rapid charging capability and cycle performance of the battery can be improved.

[0017] In any embodiment of the present application, the tap density of the negative electrode active material is 0.9 g / cm 3 ~1.3g / cm 3 and preferably 1.0 g / cm 3 ~1.1g / cm 3 When the tap density of the negative electrode active material is within a given range, the rapid charging capability of the battery can be improved, and the energy density of the battery can also be improved.

[0018] In any embodiment of the present application, the powder compaction density of the negative electrode active material at a pressure of 2 kN is 1.55 g / cm 3 ~1.67g / cm 3 and preferably 1.60 g / cm 3 ~1.65g / cm 3 When the powder compaction density of the negative electrode active material at a pressure of 2 kN is within a given range, the particles in the negative electrode film layer can be closely attached to each other, and good electrolyte wetting tunnels can be formed, improving the rapid charging capability and cycle performance of the battery.

[0019] A second aspect of the present application is A) providing a core comprising artificial graphite; The core is coated so that a coating layer containing amorphous carbon is formed on at least a part of the surface of the core. v 99≦24μm and 8μm≦D v and B) a step of obtaining a negative electrode active material that satisfies the requirement of 50≦15 μm.

[0020] In any embodiment of the present application, the preparation of artificial graphite according to step A) comprises: a) providing a coke feedstock; b) a step of shaping the coke raw material to obtain a precursor; Step c) of granulating the precursor to obtain a granulated product; The granules are graphitized to obtain a volume average particle diameter D v 50 is 6 μm to 14 μm and the volume particle size distribution D v and step d) obtaining artificial graphite having a particle size of 17 μm to 26 μm.

[0021] In any embodiment of the present application, the volume average particle size D of the granules v 50 is 9 μm to 15 μm, and the volume particle size distribution D v 99 is 17μm to 24μm.

[0022] In any embodiment of the present application, the volume average particle diameter D v 50 is 8 μm to 13 μm, and the volume particle size distribution D v 99 is 16μm to 22μm.

[0023] In any embodiment of the present application, the volume average particle diameter D v 50 is 7 μm to 12 μm, and the volume particle size distribution D v 99 is 15μm to 21μm.

[0024] In any embodiment of the present application, the particle size uniformity of the precursor is U1, and satisfies 0.2≦U1≦0.55. Optionally, 0.3≦U1≦0.45.

[0025] In any embodiment of the present application, the particle size uniformity of the artificial graphite is U2, which satisfies 0.22≦U2≦0.48. Optionally, 0.3≦U2≦0.4.

[0026] In any embodiment of the present application, the volatile content of the coke raw material is C1, the particle size uniformity of the precursor is U1, and the adhesive is added during the granulation process in step c) and the amount of adhesive used is C2, and the preparation method satisfies 21%≦(C1+C2) / U1×100%≦50%, and optionally 31%≦(C1+C2) / U1×100%≦35%.

[0027] In any embodiment of the present application, the volatile content C1 of the coke feedstock satisfies 1%≦C1≦12%. Optionally, 5%≦C1≦9%.

[0028] In any embodiment of the present application, the coke feedstock comprises one or more of petroleum-based non-needle coke, petroleum-based needle coke. Optionally, the coke feedstock comprises petroleum green coke.

[0029] In any embodiment of the present application, step B) includes step e) of coating the core with an organic carbon source and forming an amorphous carbon coating layer on at least a portion of the surface of the core by heat treatment to obtain a negative electrode active material.

[0030] In any embodiment of the present application, the amount of organic carbon source added in step e) is designated as C3, and the preparation method satisfies the following conditions: 20%≦(C1+C2+C3) / U2×100%≦56%, 1.2%≦C3×residual carbon rate≦2.5%.

[0031] The negative electrode active material obtained by the manufacturing method of the present application has a core containing artificial graphite and a coating layer containing amorphous carbon that coats the surface of the core, and the negative electrode active material is D v 99≦24μm and 8μm≦D v By satisfying the condition of 50≦15 μm, the rapid charging capability of a battery using the negative electrode active material can be significantly improved, and the cycle performance of the battery can also be significantly improved.

[0032] A third aspect provides a secondary battery including a negative electrode plate having a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector and including a negative electrode active material including the negative electrode active material described in the present application.

[0033] The secondary battery according to the present application uses the negative electrode active material described in the present application, and therefore can have high energy density, rapid charging capability, and cycle performance.

[0034] A fourth aspect of the present application provides a battery module including the secondary battery according to the present application.

[0035] A fifth aspect of the present application provides a battery pack including the secondary battery or battery module according to the present application.

[0036] A device according to a sixth aspect of the present application includes at least one of the secondary battery, the battery module, or the battery pack according to the present application.

[0037] The battery module, battery pack, and device of the present application include the secondary battery of the present application, and therefore have at least the same advantages as the secondary battery. [Brief explanation of the drawings]

[0038] In order to more clearly explain the aspects of the embodiments of the present application, the following will briefly describe the drawings that need to be used in the embodiments of the present application. Obviously, the drawings described below are only some of the embodiments of the present application, and those skilled in the art can obtain other drawings based on the drawings without any creative work. [Figure 1]1 is a scanning electron microscope (SEM) image at 1000x magnification of one embodiment of a negative electrode active material according to the present application. [Figure 2] FIG. 2 is a scanning electron microscope (SEM) image at 5000x magnification of another embodiment of the negative electrode active material according to the present application. [Figure 3] 1 is a photograph of the ion-polished cross section (CP) at a magnification of 5000 times of a negative electrode plate after the negative electrode active material according to the present application is fabricated into a negative electrode plate. [Figure 4] FIG. 2 is a transmission electron microscope (TEM) image at 60,000 times magnification of one embodiment of the negative electrode active material according to the present application. [Figure 5] FIG. 1 is a schematic diagram illustrating an embodiment of a secondary battery. [Figure 6] FIG. 6 is an exploded view of FIG. 5. [Figure 7] FIG. 1 is a schematic diagram illustrating an embodiment of a battery module. [Figure 8] FIG. 1 is a schematic diagram illustrating an embodiment of a battery pack. [Figure 9] FIG. 9 is an exploded view of FIG. 8. [Figure 10] FIG. 1 is a schematic diagram illustrating an embodiment of a device that uses a secondary battery as a power source. DETAILED DESCRIPTION OF THE INVENTION

[0039] In order to clarify the inventive object, aspects and beneficial technical effects of the present application, the present application will be described in more detail below with reference to examples. It should be understood that the examples described herein are merely for the purpose of illustrating the present application and are not intended to limit the present application.

[0040] For simplicity, this specification explicitly discloses only a few numerical ranges. However, any lower limit can be combined with any upper limit to form an open range. Any lower limit can also be combined with another lower limit to form an open range, and similarly, any upper limit can be combined with another upper limit to form an open range. Although not explicitly stated, each point or individual value between the endpoints of a range is included in this range. Therefore, each point or individual value can be combined with other points or individual values ​​as its own lower limit or upper limit, or can be combined with other lower limits or upper limits to form an open range.

[0041] In the description of this specification, unless otherwise specified, the terms "more than or equal to" and "less than or equal to" include the number, and "multiple types" in "one or more types" means two types and more than two types.

[0042] In the description of this specification, unless otherwise stated, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following conditions satisfy "A or B": A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), or A and B are both true (or exist).

[0043] The above content of the present application is not intended to describe all of the embodiments or all of the implementations disclosed herein. As follows, the description will more specifically illustrate exemplary embodiments by way of examples. In several places in the present specification, a series of examples are provided to provide teachings, and these examples can be used in various combinations. In each example, the examples are merely representative and should not be construed as exhaustive.

[0044] Secondary batteries, also called rechargeable batteries or storage batteries, are batteries that can be continuously used by activating the active material through charging after discharging.

[0045] A secondary battery generally comprises a positive electrode plate, a negative electrode plate, a separator, and an electrolyte. During the charge and discharge process of the battery, active ions (e.g., lithium ions) are absorbed and released between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily serves to prevent short-circuiting between the positive and negative electrodes and allows ions to pass through. The electrolyte primarily serves to conduct ions between the positive and negative electrodes.

[0046] The inventors have discovered that the key to improving the fast charging capability of secondary batteries lies in improving the dynamic performance of the negative electrode. A negative electrode plate typically comprises a negative current collector and a negative electrode film layer containing a negative electrode active material. The negative electrode active material generally refers to a material involved in the absorption and desorption of active ions in the negative electrode plate during the charge and discharge process of a battery. Currently, methods for improving the dynamic performance of batteries are often employed, such as reducing the thickness of the negative electrode film layer or lowering the compaction density of the negative electrode film layer. However, extensive research has shown that these methods only provide a certain degree of improvement in the dynamic performance of batteries under low SOC conditions (i.e., the early stages of charging) and little improvement in the dynamic performance under high SOC conditions (i.e., the end stages of charging). Therefore, they fail to effectively improve the fast charging capability of secondary batteries. Furthermore, the energy density of the battery is significantly reduced.

[0047] Generally, in the manufacturing process of the negative electrode active material, the volume average particle diameter D v 50 is attracting attention, and particles with a cumulative volume distribution percentage of 99% or more from the small particle size side have a small number ratio, so the D v However, the inventors have conducted extensive research and found that the D v We were surprised to discover that by keeping 99 within a specific range, the rapid lithium absorption capability of the negative electrode active material in a high lithium absorption state (corresponding to a high SOC state of the battery) can be significantly improved, thereby overcoming the above bottleneck and improving the rapid charging capability of the secondary battery in a high SOC state.

[0048] Therefore, the present invention provides a polymer having a core containing artificial graphite and a coating layer containing amorphous carbon that coats at least a part of the surface of the core, the polymer having a volume particle size distribution D v 99≦24 μm and the average volume particle size D v 50 is 8μm≦D v To provide a negative electrode active material that satisfies the requirement of 50≦15 μm.

[0049] After extensive research, the inventors have found that the use of the negative electrode active material of the present invention allows batteries to have high energy density and high solid-phase diffusion of active ions. Even in a high lithium absorption state at the end of charging (high SOC), the negative electrode active material particles maintain good electrochemical reaction activity, and active ions are rapidly absorbed and transported into the bulk phase of the negative electrode active material. This effectively improves the diffusion rate of active ions in the negative electrode plate, reduces ohmic and concentration polarization, and significantly increases the overall charge rate and depth of charge of the negative electrode plate. Therefore, the present invention enables batteries to be charged at high multipliers at all SOC states, significantly improving fast charging capability. Furthermore, the excellent active ion migration between the positive and negative electrodes and the small polarization in the battery also significantly improve cycle performance. Generally, a low SOC state generally refers to 30% SOC or less, and a high SOC state generally refers to 60% SOC or more.

[0050] The artificial graphite referred to in this application generally refers to a graphite material obtained through a high-temperature graphitization treatment, and the degree of graphitization crystallization is generally high.

[0051] Amorphous carbon, as used herein, generally refers to carbon materials that have a low degree of graphitic crystallization.

[0052] In general, the lattice structure of artificial graphite tends to be a layered arrangement with long-range order, while the lattice structure of amorphous carbon tends to be disordered. Generally, the lattice arrangement can be observed by transmission electron microscope (TEM) images.

[0053] In some embodiments, the core may have one or more of the following shapes: a block shape, a sheet shape, and a roughly spherical shape.

[0054] In some embodiments, the thickness of the coating layer is ≧2 nm, optionally 2 nm to 20 nm, for example, 2 nm to 15 nm, 2 nm to 10 nm, or 5 nm to 10 nm.

[0055] In some embodiments, the coverage of the coating layer on the core surface is ≧50%, optionally 60% to 100%.

[0056] In some embodiments, the negative electrode active material is D v 99≦23.8 μm, ≦23.5 μm, ≦23 μm, ≦22.5 μm, ≦22 μm, ≦21 μm, or ≦20 μm can be satisfied.

[0057] In some embodiments, the negative electrode active material is D v 99≧15 μm, ≧16 μm, ≧17 μm, ≧18 μm, ≧19 μm can be satisfied.

[0058] In some embodiments, the negative electrode active material has a thickness of 15 μm≦D v 99≦24μm, for example, 16μm≦D v 99≦22μm, 17μm≦D v 99≦24μm, 17μm≦D v 99≦23μm, 15μm≦D v 99≦21μm, 18μm≦D v 99≦21μm, 19μm≦D v 99≦21μm, 19μm≦D v 99≦22μm, 19μm≦D v 99≦23μm, 20μm≦D v 99≦22μm, 20μm≦D v 99≦21.5μm or 20μm≦D v 99≦21 μm.

[0059] Negative electrode active material D vWhen 99 is within the appropriate range, it can further improve the solid-phase diffusion rate of active ions when the negative electrode is in a high lithium absorption state, reduce polarization, help reduce the number of relatively small particles, allow the particles to absorb more active ions, and form a smooth tunnel structure in the negative electrode film layer, shorten the liquid phase conduction path, and further improve the battery's fast charging ability and cycle performance. v By using an appropriate negative electrode active material, the secondary battery can achieve both high rapid charging capability and cycle performance.

[0060] In some embodiments, the negative electrode active material is D v 50≦14 μm, ≦13 μm, or ≦12 μm. v 50≧8 μm, ≧9 μm, ≧10 μm, or ≧11 μm. For example, the negative electrode active material has a thickness of 8 μm≦D v 50≦14μm, 9μm≦D v 50≦13μm, 10μm≦D v 50≦14μm, 12μm≦D v 50≦14μm, 12μm≦D v 50≦13μm or 11μm≦D v The condition 50≦13 μm can be satisfied.

[0061] Negative electrode active material D v When the D 50 is within the appropriate range, it is possible to shorten the migration path of the active ions in the negative active material particles, which is advantageous for forming a smooth porous structure in the negative electrode membrane layer, allowing the negative electrode plate to have good solid-phase diffusion speed and good liquid-phase transport performance of the active ions, and further improving the rapid charging ability of the battery. v When 50 is within the appropriate range, it can further ensure that the negative electrode active material has a high gram capacity, which is beneficial for achieving a high energy density of the battery, and also reduces side reactions of the electrolyte at the negative electrode, thereby improving the cycle performance of the battery.

[0062] In some embodiments, the particle size uniformity of the negative electrode active material is 0.25 to 0.45, and may be, for example, 0.28 to 0.4, 0.32 to 0.4, 0.32 to 0.38, 0.30 to 0.36, 0.31 to 0.35, or 0.32 to 0.36. The particle size uniformity of the negative electrode active material is determined by the particle size of all particles in the negative electrode active material being smaller than the volume average particle size D v 50, and reflects the uniformity of the particle size distribution of the negative electrode active material. When the particle size uniformity of the negative electrode active material is within this range, it is easy to form a short liquid phase transport path in the negative electrode film layer and a large contact area between particles, which is beneficial for electron conduction and active ion transport in the negative electrode plate, further improving the battery's fast charging capability. It also allows the particles in the negative electrode film layer to adhere to each other, increasing the compaction density of the negative electrode plate and improving the battery's energy density.

[0063] In some embodiments, the negative electrode active material has a molecular weight of 0.6≦(D v 90-D v 10) / D v 50≦1.8. v 90-D v 10) / D v 50 is, for example, 0.8 to 1.4, 0.9 to 1.3, 1.0 to 1.25, or 1.2 to 1.6. v 90-D v 10) / D v 50 is the volume average particle diameter D v The negative electrode active material (D v 90-D v 10) / D v An appropriate 50 is beneficial to improving the processability of the negative electrode slurry and the negative electrode film layer, ensuring that the entire negative electrode film layer has a high particle distribution uniformity, and favoring high active ion transport performance in different regions of the negative electrode film layer, which in turn improves the fast charging ability of the battery.

[0064] In some embodiments, the volume particle size distribution D of the negative electrode active materialv The thickness 90 is 13 μm to 18 μm, and may be, for example, 13 μm to 16 μm, 14 μm to 17 μm, or 15 μm to 18 μm. v When 90 is within the appropriate range, the solid-state diffusion rate of the active ions in the negative electrode film layer can be further improved, the rapid charging capability of the battery can be further improved, and the negative electrode active material can have a high gram capacity, which helps to improve the energy density of the battery.

[0065] In some embodiments, the volume particle size distribution D of the negative electrode active material v The particle size 10 is 5 μm to 10 μm, and may be, for example, 6 μm to 8 μm. Since the content of small particles in the negative electrode active material is small, side reactions between the electrolyte and the material are reduced, and the cycle performance and storage performance of the battery can be improved.

[0066] In some embodiments, the particle size-specific surface area of ​​the negative electrode active material is 0.4 m 2 / g~0.75m 2 / g, for example, 0.4m 2 / g~0.7m 2 / g, 0.42m 2 / g~0.68m 2 / g, 0.46m 2 / g~0.55m 2 / g, 0.5m 2 / g~0.68m 2 / g, or 0.5m 2 / g~0.65m 2 / g.

[0067] The "particle-size specific surface area" of the negative electrode active material according to the present application differs from the "specific surface area" of general negative electrode active materials. Currently, the specific surface area (SSA) of negative electrode active materials in the industry is often obtained using the gas adsorption BET method, and is used to represent only the physical adsorption specific surface area of ​​the negative electrode active material. The "particle-size specific surface area" of the negative electrode active material according to the present application is obtained using laser diffraction particle size analysis, and represents the degree to which the shape of the negative electrode active material deviates from sphericity.

[0068] The inventors have found that when the particle size-specific surface area of ​​the negative electrode active material is within an appropriate range, the ion release paths in the negative electrode film layer can be increased, the charge exchange impedance can be reduced, and smoother tunnels can be formed in the negative electrode film layer, improving the wettability of the electrolyte and further improving the transport rate of active ions between the solid and liquid phases in the negative electrode plate, thereby further improving the rapid charging performance and cycle performance of the battery. In addition, a moderate particle size-specific surface area of ​​the negative electrode active material can improve the compaction density of the negative electrode film layer and thereby improve the energy density of the battery.

[0069] In some embodiments, the negative electrode active material includes secondary particles, as shown in FIGS. 1 and 2 . Optionally, the number ratio of the secondary particles in the negative electrode active material is ≥ 50%. For example, the number ratio of the secondary particles in the negative electrode active material is 50% to 100%, 60% to 100%, 60% to 90%, 70% to 100%, 70% to 95%, 70% to 90%, 70% to 80%, or 75% to 85%. When the negative electrode active material contains a large amount of secondary particles, the number of active ion release paths in the negative electrode film layer increases, further improving the fast charging capability of the battery, reducing polarization, and improving cycle performance. In particular, when the negative electrode active material contains both secondary particles and primary particles, side reactions of the electrolyte in the negative electrode can be reduced, further improving the cycle performance and storage performance of the battery.

[0070] In some embodiments, the graphitization degree of the negative electrode active material is 91.0% to 96.0%, for example, 94.0% to 95.0%, or 93.0% to 94.5%. When the graphitization degree of the negative electrode active material is within this range, the particle structure can have a large interlayer distance and low powder resistance, thereby further improving the fast charging capability.

[0071] In some embodiments, the gram capacity of the negative electrode active material is 345 mAh / g to 360 mAh / g, for example, 350 mAh / g to 358 mAh / g, 351 mAh / g to 356 mAh / g, or 352 mAh / g to 355 mAh / g. The high gram capacity of the negative electrode active material can improve the energy density of the battery. Having a gram capacity within the above range means that the active ions in the active material have a short migration path, improving the rapid charging capability of the battery.

[0072] In some embodiments, the tap density of the negative electrode active material is 0.9 g / cm 3 ~1.3g / cm 3 For example, 1.0 g / cm 3 ~1.1g / cm 3 When the tap density of the negative electrode active material is within a given range, the particles in the negative electrode coating layer can be in good contact with each other, improving the rapid charging capability of the battery. In addition, the particles can be densely packed together, improving the energy density of the battery.

[0073] In some embodiments, the negative electrode active material has a powder compaction density of 1.55 g / cm at a pressure of 2 kN. 3 ~1.67g / cm 3 For example, 1.60 g / cm 3 ~1.65g / cm 3 When the powder compaction density of the negative electrode active material at a pressure of 2 kN is within a given range, the particles in the negative electrode film layer can be closely attached to each other, and good electrolyte wetting tunnels can be formed, thereby improving the rapid charging capability and cycle performance of the battery.

[0074] In the present application, the negative electrode active material D v 99, D v 90, D v 50, D v10. The particle size uniformity and particle size specific surface area can be measured by laser diffraction particle size analysis, for example, referring to GB / T19077-2016 standard, using a laser particle size analyzer (e.g., Malvern Master Size 3000).

[0075] D v 99 is the particle size corresponding to when the cumulative volume distribution percentage of the negative electrode active material reaches 99%, and D v 90 is the particle size corresponding to when the cumulative volume distribution percentage of the negative electrode active material reaches 90%, and D v 50 is the particle size corresponding to when the cumulative volume distribution percentage of the negative electrode active material reaches 50%, and D v 10 is the particle size corresponding to when the cumulative volume distribution percentage of the negative electrode active material reaches 10%.

[0076] In the present application, the negative electrode active material is made into a negative electrode plate, and the material type of the core can be observed by measuring the ion polishing cross section (CP) of the negative electrode plate. For example, the measurement method may be as follows: First, the prepared negative electrode plate is cut into a sample to be measured (e.g., 2 cm x 2 cm), and the negative electrode plate is fixed to a sample stage with paraffin. Next, the sample stage is placed in a sample holder, locked and fixed, and the power of an argon ion cross section polishing device (e.g., IB-19500CP) is turned on and a vacuum (e.g., 10 -4 The argon gas flow rate (e.g., 0.15 MPa), voltage (e.g., 8 KV), and polishing time (e.g., 2 hours) are set, the sample stage is adjusted to the oscillation mode, and polishing begins. Sample measurements can be performed by referring to JY / T010-1996. Randomly select an area on the sample to be measured for scanning measurement, and obtain an ion-polished cross-section (CP) photograph of the negative electrode plate at a certain magnification (e.g., 5000x). For example, as can be seen in Figure 3 of the present application, the core of the negative electrode active material of the present application is artificial graphite.

[0077] In this application, the structure of the negative electrode active material (e.g., core and coating layer) can be measured using equipment and methods known in the art. For example, the procedure can be as follows: Select a microgrid of a certain diameter (e.g., 3 mm in diameter), pinch the edge of the microgrid with pointed tweezers, place the microgrid with the film side facing up (observe the shiny side under a lamp, i.e., the film side), gently flatten it, and place it on white filter paper. Take an appropriate amount of graphite particle sample (e.g., 1 g), place it in a beaker containing an appropriate amount of ethanol, and perform ultrasonic oscillation for 10 to 30 minutes. Then, aspirate the sample using a glass capillary. Then, drop 2 to 3 drops of the sample onto the microgrid and bake in an oven for 5 minutes. After that, place the microgrid with the sample on the sample stage and measure it using a transmission electron microscope (e.g., Hitachi HF-3300S Cs-corrected STEM) at a certain magnification (e.g., 60,000x), resulting in a transmission electron microscope (TEM) image of the sample. For example, as is clear from FIG. 4 of the present application, the negative electrode active material of the present application includes a core and a coating layer.

[0078] In this application, primary particles and secondary particles have the meanings known in the art. Primary particles refer to particles in a non-aggregated state, and secondary particles refer to particles in an aggregated state formed by the aggregation of two or more primary particles. Primary particles and secondary particles can be easily distinguished by taking SEM images with a scanning electron microscope.

[0079] The secondary particle number ratio in the negative electrode active material can be measured using methods known in the art. An exemplary measurement method involves placing the negative electrode active material on a conductive adhesive and adhering it to prepare a test sample measuring 6 cm x 1.1 cm in length x width. The particle shape is then measured using a scanning electron microscope (e.g., a ZEISS Sigma 300). For the measurement, reference can be made to JY / T010-1996. To ensure the accuracy of the measurement results, multiple (e.g., five) different regions of the test sample are randomly selected and scanned at a certain magnification (e.g., 1000x) to calculate the percentage of the secondary particles in each region relative to the total particle number. The secondary particle number ratio in that region is then calculated. The average of the measurement results for the multiple measurement regions is then used as the secondary particle number ratio in the negative electrode active material. To ensure the accuracy of the measurement results, the above measurement can be repeated for multiple samples (e.g., 10 samples), with the average of each sample being used as the final measurement result.

[0080] The graphitization degree of the negative electrode active material has a meaning known in the art and can be measured by a method known in the art. The graphitization degree can be measured, for example, using an X-ray diffractometer (e.g., Bruker D8 Discover) according to JIS K0131-1996 and JB / T4220-2011. 002 Measure the magnitude of G using the formula G = (0.344 - d 002 ) / (0.344-0.3354)×100%. 002 is the interlayer distance of the graphite crystal structure expressed in nanometers (nm). In the X-ray diffraction analysis measurement, a copper target is used as the anode target, CuKα radiation is used as the radiation source, the radiation wavelength λ is 1.5418 Å, the 2θ angle range of the scan is 20° to 80°, and the scan speed may be 4° / min.

[0081] The tap density of the negative electrode active material has a meaning known in the art and can be measured using a method known in the art. For example, it can be measured using a powder tap density tester in accordance with GB / T5162-2006. When using a tap density tester FZS4-4B from Beijing Iron and Steel Research Institute, the measurement parameters are: vibration frequency: 250±15 times / min, amplitude: 3±0.2 mm, vibration count: 5000 times, and graduated cylinder: 25 mL.

[0082] The powder compaction density of the negative electrode active material at a pressure of 2 kN has a meaning known in the art and can be measured using a method known in the art. For example, it is measured using an electronic pressure tester (e.g., UTM7305 type) in accordance with the GB / T24533-2009 standard. An exemplary measurement method is to weigh 1 g of the negative electrode active material and measure the powder compaction density at a pressure of 2 kN. 2 The powder compaction density of the negative electrode active material at a pressure of 2 kN is calculated and recorded.

[0083] The gram capacity of the negative electrode active material has a meaning known in the art and can be measured using methods known in the art. An exemplary measurement method is as follows: The prepared negative electrode active material, the conductive agent carbon black (Super P), and the adhesive polyvinylidene fluoride (PVDF) are uniformly mixed in a mass ratio of 91.6:1.8:6.6 with the solvent N-methylpyrrolidone (NMP) to prepare a slurry. The slurry is then applied to a copper foil current collector and dried in an oven before use. A metallic lithium sheet is used as the counter electrode, and a polyethylene (PE) film is used as the separator. Ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1, and LiPF6 is then uniformly dissolved in the solution to obtain an electrolyte solution with a LiPF6 concentration of 1 mol / L. A CR2430-type coin battery is assembled in an argon atmosphere glove box. The resulting coin battery was allowed to stand for 12 hours, then discharged at a constant current of 0.05 C to 0.005 V at 25°C, allowed to stand for 10 minutes, discharged at a constant current of 50 μA to 0.005 V, allowed to stand for 10 minutes, discharged at a constant current of 10 μA to 0.005 V, and then charged at a constant current of 0.1 C to 2 V, and the charge capacity was recorded. The ratio of the charge capacity to the mass of the negative electrode active material is the gram capacity of the prepared negative electrode active material.

[0084] The above-mentioned various parameters of the negative electrode active material may be measured by directly taking a sample of the negative electrode active material, or by sampling from the secondary battery.

[0085] When sampling the above-mentioned sample from the secondary battery, the sampling can be performed, for example, by the following steps.

[0086] (1) The secondary battery is discharged (for safety reasons, the battery is generally fully discharged), and after removing the battery, the negative electrode plate is taken out and immersed in dimethyl carbonate (DMC) for a certain period of time (e.g., 2 to 10 hours). After that, the negative electrode plate is taken out and dried at a certain temperature for a certain period of time (e.g., 60°C, 4 hours). After drying, the negative electrode plate is taken out.

[0087] (2) The negative electrode plate dried in step (1) is baked at a certain temperature for a certain time (for example, 400°C, 2 hours), and an arbitrary area is selected from the baked negative electrode plate, and the negative electrode active material is sampled (the powder can be scraped off with a blade for sampling).

[0088] (3) The negative electrode active materials collected in step (2) are each subjected to a sieving process (for example, sieving with a 200 mesh sieve) to finally obtain samples of the negative electrode active materials that can be used to measure the parameters of each of the above materials in the present application.

[0089] The present invention next provides a method for producing a negative electrode active material, and the above-mentioned negative electrode active material can be obtained based on this method. The method for producing a negative electrode active material can include the following steps A) and B).

[0090] A) Providing a core comprising synthetic graphite.

[0091] B) coating the core so that a coating layer containing amorphous carbon is formed on at least a portion of the surface of the core; v 99≦24μm and 8μm≦D v A negative electrode active material having a particle size of 50 μm≦15 μm is obtained.

[0092] In some embodiments, in step A), the method for producing artificial graphite comprises: a) providing a coke feedstock; Step b) of subjecting the coke raw material to a shaping treatment to obtain a precursor; Step c) of granulating the precursor to obtain a granulated product; The granules are subjected to graphitization treatment, and D v 50 is 6 μm to 14 μm, and D v and step d) obtaining artificial graphite having a particle size of 17 μm to 26 μm.

[0093] In some embodiments, the coke feedstock D v 50 becomes 7μm~12μm, D vD of coke raw material so that 99 is 15μm to 21μm v 50 and D v 99 can be adjusted. v 50 and D v If the 99 is within a given range, it is advantageous for improving the subsequent shaping and granulation processes, and the final negative electrode active material has an appropriate secondary particle content and an appropriate D v 50 and D v Optionally, the coke feedstock D v 50 is 8 μm to 12 μm, 8 μm to 11.5 μm, or 9 μm to 11 μm. Optionally, the D v 99 is 16 μm to 21 μm, 17 μm to 21 μm, 17 μm to 20 μm, or 17 μm to 19 μm.

[0094] In step a), the coke raw material can be a commercially available product or can be obtained by pulverizing the coke material. In some embodiments, the coke raw material is subjected to a pulverization process to obtain the D of the coke raw material. v 50 and D v 99 can be controlled within the desired range. The coke raw material can be pulverized using equipment and methods known in the art, such as a jet mill, mechanical mill, or roll mill. Since many undersized particles are always produced during pulverization and oversized particles may also be present, classification can be performed after pulverization as needed to remove undersized and oversized particles from the pulverized powder. After classification, a coke raw material having a desired particle size distribution can be obtained. Classification can be performed using equipment and methods known in the art, such as a classifying sieve, gravity classifier, or centrifugal classifier.

[0095] The coke raw material can be pulverized in a process unit including a pulverizer, a classifier, and an intake fan. During the pulverization process, the D of the obtained coke raw material can be controlled by adjusting and controlling the supply frequency, pulverizing frequency, classifying frequency, and intake frequency. v 50 and D v99 can be adjusted and controlled within a desired range. In contrast to the low classification frequency in the conventional pulverization process, the method of the present invention can improve the classification frequency, which is advantageous for removing undersized particles. In contrast to the high intake frequency in the conventional pulverization process, the method of the present invention can reduce the intake frequency, which is advantageous for removing oversized particles. In addition, in contrast to the wide frequency range controlled in the conventional pulverization process, the method of the present invention can further control the main machine frequency, classification frequency, and intake frequency within a narrow frequency range, which can narrow the particle size distribution width of the coke raw material, for example, the D v 50 and D v 99 within a narrow range. In addition, by synchronously adjusting and controlling the feeding frequency, the feeding amount can be controlled, which can further improve the material crushing effect.

[0096] In some embodiments, the supply frequency may be between 10 Hz and 40 Hz, for example between 25 Hz and 35 Hz.

[0097] In some embodiments, the grinding frequency may be between 20 Hz and 50 Hz, for example between 35 Hz and 45 Hz.

[0098] In some embodiments, the classification frequency may be between 20 Hz and 50 Hz, for example between 40 Hz and 50 Hz.

[0099] In some embodiments, the inspiration frequency may be between 30Hz and 55Hz, for example between 35Hz and 45Hz.

[0100] Those skilled in the art can select and adjust one or more of the above process conditions according to the actual operating conditions to finally obtain D v 50 is 7 μm to 12 μm and D v It is possible to obtain a coke raw material with a particle size of 15 μm to 21 μm.

[0101] In some embodiments, the coke feedstock described in step a) can comprise one or more of petroleum-based non-needle coke, petroleum-based needle coke. Optionally, the coke feedstock comprises petroleum green coke.

[0102] In some embodiments, the volatile content C1 of the coke feedstock described in step a) satisfies 1%≦C1≦12%. Optionally, the volatile content C1 of the coke feedstock is 3%-10%, 5%-9%, 6%-8%, 7%-8.5%, or 7.5%-8.5%, etc. An appropriate volatile content of the coke feedstock is beneficial for improving the particle size distribution of the material in the subsequent granulation process, helping the negative electrode active material have a desired particle size distribution. Furthermore, an appropriate volatile content of the coke feedstock also ensures that the artificial graphite produced has high structural strength, which can improve the cycle life of the negative electrode active material and the cycle performance of the battery.

[0103] The volatile content of the coke feedstock can be measured by methods known in the art, for example, with reference to SH / T0026-1990.

[0104] In step b), the shaping can remove the corners of the coke raw material particles, which is advantageous for the subsequent granulation process and ensures that the secondary particles in the resulting negative electrode active material have high structural stability. The shaping treatment can be performed on the coke raw material using equipment and methods known in the art, such as a shaping machine or other shaping devices.

[0105] In some embodiments, the coke raw material is subjected to a shaping process and then further classified, thereby obtaining a precursor D v 50 is 8μm~13μm, D v 99 is 16 μm to 22 μm, and the final negative electrode active material has an appropriate secondary particle content and an appropriate D v 50 and D v 99. Optionally, the precursor D v50 is 9 μm to 12 μm, 9 μm to 11 μm, 10 μm to 12 μm, or 10 μm to 11 μm. v 99 is 17 μm to 22 μm or less, 18 μm to 21 μm or less, or 18 μm to 20 μm or less. The classification process can be carried out using equipment and methods known in the art, such as a classification sieve, a gravity classifier, or a centrifugal classifier.

[0106] The shaping and classification process can be performed in a process unit including a shaping machine, a classifier, and an intake fan. In the shaping and classification process, the shaping frequency (e.g., the main and auxiliary machine frequencies of the shaping machine), the classification frequency, and the intake frequency are adjusted and controlled to control the D of the obtained precursor. v 50 and D v The inventors have found that, compared with the conventional shaping and classification processes, the method of the present invention can improve the shaping frequency in the treatment process, appropriately extend the shaping time, and further reduce the classification frequency and intake frequency in the treatment process, thereby improving the D of the obtained precursor. v 50 and D v Adjust and control 99 within the target range.

[0107] The obtained precursor can further have a suitable particle size uniformity (U1), which helps to improve the particle size uniformity of the obtained negative electrode active material.

[0108] In some embodiments, the particle size uniformity U1 of the precursor satisfies 0.2≦U1≦0.55, such as 0.2≦U1≦0.5, 0.25≦U1≦0.45, 0.3≦U1≦0.45, 0.3≦U1≦0.4, 0.35≦U1≦0.55, or 0.35≦U1≦0.45.

[0109] In some embodiments, in step b), the coke raw material is shaped and classified by controlling the main machine frequency of the shaping machine to 35 Hz to 40 Hz, the auxiliary machine frequency to 60 Hz to 70 Hz, the classification frequency to 40 Hz to 50 Hz, the intake frequency to 10 Hz to 25 Hz, and the shaping time to 160 s to 180 s, and D v 50 is 8 μm to 13 μm and Dv Obtain precursors with particle sizes between 16 μm and 22 μm.

[0110] In step c), the precursor is granulated to aggregate the independently dispersed primary particles to form secondary particles, which improves the isotropy of the artificial graphite, allowing active ions to be absorbed into the particles from all directions, improving the lithium absorption rate in the solid state, and reducing polarization.

[0111] In some embodiments, D of the granulation obtained in step c) v 50 is 9 μm to 15 μm, and D v 99 may be 17 μm to 24 μm. Optionally, the D v 50 is 10 μm to 14 μm, 11 μm to 15 μm, or 11 μm to 13 μm. Optionally, granulation D v 99 is 18 μm to 24 μm or 19 μm to 22 μm. v 50 and D v If 99 is within the appropriate range, the D of the final negative electrode active material v 50 and D v This is advantageous in keeping 99 within the desired range.

[0112] In step c), granulation can be carried out using equipment known in the art, such as a granulator. The granulator generally comprises an agitation reactor and a module for controlling the temperature of the reactor. By adjusting and controlling the agitation rotation speed, temperature rise rate, granulation temperature, temperature fall rate, etc. during the granulation process, the degree of granulation can be adjusted and controlled, and the D of the obtained granules can be adjusted and controlled. v 50 and D v Furthermore, by adjusting the granulation process, the D 99 of the final negative electrode active material can be adjusted to a desired range. v 10. D v 90 to the desired range, and the D of the resulting granules v 10. D v 90 can be made to meet your needs.

[0113] In some embodiments, the precursor and the adhesive may be mixed and then granulated at high temperature. The mixing temperature may be 20°C to 40°C. Compared with the conventional graphite production process, the present invention can improve the granulation degree by appropriately increasing the mixing frequency and shortening the mixing time, and the D of the obtained granules can be improved. v 50 and D v 99 within the desired range.

[0114] The temperature of the high-temperature granulation can be determined depending on the type of adhesive. The adhesive softens at high temperatures, bonding particles together, and granulation is achieved. In some embodiments, the adhesive is pitch. In these examples, the granulation temperature may be 700°C to 800°C. The present application further improves the temperature rise program for the high-temperature granulation process, adopting a stepwise temperature rise. By setting multiple (e.g., 2 to 4) program temperature rise platforms during the temperature rise process, the granulated material can achieve a desired particle size distribution. In addition, the granulated material has good particle size uniformity, which helps to ensure good particle size uniformity in the subsequent artificial graphite and the final negative electrode active material product.

[0115] In some embodiments, in step c), the mixing frequency is controlled to 35 Hz to 38 Hz, and the mixing time is controlled to 50 min to 65 min. Subsequently, the temperature is increased to 300°C to 400°C at 6 to 10°C / min, maintained at that temperature for 1 to 2 hours, further increased to 500°C to 600°C at 6 to 10°C / min, maintained at that temperature for 1 to 2 hours, further increased to 700°C to 800°C at 6 to 10°C / min, maintained at that temperature for 1 to 2 hours, and then allowed to cool naturally to obtain a granulated product.

[0116] In some embodiments, in step c), the amount of adhesive C2 added during the granulation process, the volatile matter content C1 of the coke raw material, and the particle size uniformity U1 of the precursor satisfy the relationship 21%≦(C1+C2) / U1×100%≦50%. Optionally, 25%≦(C1+C2) / U1×100%≦45%, 25%≦((C1+C2) / U1×100%≦38%, 27%≦(C1+C2) / U1×100%≦38%, 30%≦(C1+C2) / U1×100%≦40%, or 31%≦(C1+C2) / U1×100%≦35%. When the above relationships are satisfied among the amount C2 of binder added during the granulation process, the volatile matter content C1 of the coke raw material, and the particle size uniformity U1 of the precursor, the degree of granulation of the negative electrode active material particles can be improved, and the deionization performance and structural stability of the negative electrode active material can be enhanced.

[0117] The amount C2 of adhesive added in the granulation process is the percentage of the weight of the adhesive added in the granulation process to the total weight of the precursor. The granulation process is carried out with or without the addition of an adhesive.

[0118] In some embodiments, the amount of adhesive C2 added to the granulation process can satisfy 0%≦C2≦16%, optionally 1%≦C2≦12%, 2%≦C2≦10%, 4%≦C2≦7%, or 5%≦C2≦9%.

[0119] In some embodiments, in step d), the granules are graphitized at a temperature of 2800°C to 3200°C to obtain artificial graphite having an appropriate degree of graphitization. Optionally, the graphitization temperature may be 2900°C to 3100°C.

[0120] In step d), graphitization can be performed using equipment known in the art, such as a graphitization furnace, and further, for example, an Acheson-type graphitization furnace. After the graphitization process is completed, a small amount of oversized particles formed by agglomeration of the granules during high-temperature graphitization can be removed by sieving, and the D of the finally obtained negative electrode active material can be obtained. v 50 and D v It is advantageous to have 99 within the desired range.

[0121] In some embodiments, the D of the artificial graphite obtained in step d) v 50 may be 6.5 μm to 14 μm, 7 μm to 14 μm, 6 μm to 13 μm, 7 μm to 13.5 μm, 8 μm to 12 μm, 9 μm to 12 μm, 9 μm to 11 μm, 10 μm to 13 μm, 10 μm to 12 μm, 6.5 μm to 12 μm, or 6.5 μm to 12.5 μm.

[0122] In some embodiments, the D of the artificial graphite obtained in step d) v 99 may be 18 μm to 24 μm, 19 μm to 26 μm, 21 μm to 26 μm, 20 μm to 25 μm, 20 μm to 23 μm, or 19.5 μm to 22 μm.

[0123] In some embodiments, the particle size uniformity U2 of the artificial graphite obtained in step d) can satisfy 0.22≦U2≦0.48, and optionally 0.25≦U2≦0.45, 0.26≦U2≦0.43, 0.3≦U2≦0.4, or 0.33≦U2≦0.38. Having the particle size uniformity of the obtained artificial graphite within an appropriate range is advantageous for ensuring that the particle size uniformity of the final negative electrode active material falls within a desired range.

[0124] In some embodiments, step B) can include step e) of coating the core with an organic carbon source and heat treating the core to form an amorphous carbon coating layer on at least a portion of the surface of the core to obtain the negative electrode active material.

[0125] In some embodiments, in step e), an amorphous carbon coating layer is formed on at least a portion of the surface of the core, and then the negative electrode active material is obtained by sieving.

[0126] For example, the artificial graphite obtained in step d) may be mixed with an organic carbon source to coat at least a portion of the surface of the artificial graphite with the organic carbon source, followed by heat treatment at a temperature of 700°C to 1800°C to carbonize the organic carbon source and form an amorphous carbon coating layer on at least a portion of the surface of the artificial graphite. Optionally, the heat treatment temperature is 1000°C to 1300°C.

[0127] In some embodiments, the relationship between the amount of organic carbon source C3 added during the coating process, the volatile content C1 of the coke raw material, the amount of adhesive C2 added during the granulation process, and the particle size uniformity U2 of the artificial graphite satisfies 20%≦(C1+C2+C3) / U2×100%≦56%. The organic carbon source satisfies 1.2%≦C3×residual carbon content≦2.5%. The amount of organic carbon source C3 is the weight percentage of the organic carbon source added during the coating process relative to the total weight of the artificial graphite. The residual carbon content refers to the residual carbon content of the organic carbon source and can be measured using an LP-5731 coal pitch coking value tester. GB / T 268 "Method for Determining Carbon Residue in Petroleum Products" and GB / T 8727-2008 "Method for Determining the Coking Value of Coal Pitch-Based Products" can be referenced.

[0128] When the amount of organic carbon source added during the coating process satisfies the above relationship, the degree of granulation of the negative electrode active material can be improved. This is advantageous because the particle size uniformity, particle size-specific surface area, and secondary particle number ratio of the negative electrode active material are within the above ranges. Furthermore, when the amount of organic carbon source used is within the above range and the ratio of the coating layer on the negative electrode active material is appropriate, the negative electrode active material can achieve both good dynamic performance and a long cycle life. Optionally, 30%≦((C1+C2+C3) / U2×100%≦48%. More optionally, 40%≦(C1+C2+C3) / U2×100%≦48%. Optionally, 1.5%≦C3×residual carbon ratio≦2.4%, 1.8%≦C3×residual carbon ratio≦2.3%, or 2%≦C3×residual carbon ratio≦2.2%.

[0129] Optionally, 2%≦C3≦8%. For example, C3 may be 3%, 4%, 5%, 6% or 7%.

[0130] In some embodiments, the organic carbon source can be selected from one or more of pitch (eg, coal pitch, petroleum pitch), phenolic resin, coconut shell, and the like, more preferably pitch.

[0131] In the above-mentioned production process, the coke raw material generally contains some impurity elements (e.g., iron, nickel, chromium, zinc, sulfur, silicon, etc.), and some impurity elements (e.g., iron, copper, etc.) are also introduced in the equipment used in the crushing, shaping, and granulation processes. Generally, the content of impurity elements in the core is small, generally less than 1 ppm.

[0132] In the above-mentioned production process, trace amounts of impurity elements are introduced into the coating layer due to the organic carbon source used in the coating process and the equipment used for coating.

[0133] secondary battery

[0134] The present application also provides a secondary battery. The secondary battery includes a positive electrode plate, a negative electrode plate, and an electrolyte. During the charge and discharge process of the battery, active ions are absorbed and released between the positive electrode plate and the negative electrode plate. The electrolyte serves to conduct ions between the positive electrode plate and the negative electrode plate.

[0135] [Negative electrode]

[0136] In the secondary battery according to the present application, the negative electrode plate includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, and the negative electrode film layer includes one or more negative electrode active materials according to the present application.

[0137] In some embodiments, the negative electrode film layer may optionally contain a certain amount of other commonly used negative electrode active materials in addition to the negative electrode active materials described herein, such as one or more of natural graphite, other artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based materials may be selected from one or more of elemental silicon, silicon oxides, and silicon-carbon composites. The tin-based materials may be selected from one or more of elemental tin, tin oxides, and tin alloys.

[0138] In the secondary battery according to the present application, the negative electrode film layer generally includes a negative electrode active material, an optional adhesive, an optional conductive agent, and other optional additives, and is generally formed by coating and drying a negative electrode slurry. The negative electrode slurry is generally formed by dispersing the negative electrode active material, optional conductive agent, adhesive, etc. in a solvent and stirring the mixture uniformly. The solvent may be N-methylpyrrolidone (NMP) or deionized water.

[0139] By way of example, the conductive agent may include one or more of superconducting carbon, carbon black (such as acetylene black or ketjen black), carbon dots, carbon nanotubes, graphene, carbon nanofibers, and the like.

[0140] By way of example, the adhesive may include one or more of styrene butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin, polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0141] Other optional auxiliary agents include, for example, thickeners (for example, sodium carboxymethylcellulose CMC-Na), PTC thermistor materials, and the like.

[0142] In the secondary battery according to the present application, the negative electrode plate does not exclude additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode plate according to the present application may further include a conductive undercoat layer (e.g., composed of a conductive agent and an adhesive) interposed between the negative electrode current collector and the first negative electrode film layer and provided on the surface of the negative electrode current collector. In other embodiments, the negative electrode plate according to the present application may further include a protective coating layer covering the surface of the second negative electrode film layer.

[0143] [Positive electrode]

[0144] In the secondary battery according to the present application, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer containing a positive electrode active material and provided on at least one surface of the positive electrode current collector. The positive electrode current collector has, for example, two surfaces opposing each other in its thickness direction, and the positive electrode film layer is provided on one or both of the two opposing surfaces of the positive electrode current collector.

[0145] In the secondary battery according to the present application, the positive electrode active material may be any positive electrode active material known in the art. The positive electrode active material may include, for example, at least one or more of lithium transition metal oxides, olivine-type lithium-containing phosphates, and modified compounds thereof. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and modified compounds thereof. Examples of olivine-type lithium-containing phosphates include, but are not limited to, lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite material of lithium manganese iron phosphate and carbon, and modified compounds thereof. The present application is not limited to these materials, and other known materials conventionally available as positive electrode active materials for secondary batteries may also be used.

[0146] In some embodiments, in order to further improve the energy density of the battery, the positive electrode active material may include one or more of the lithium transition metal oxides and their modified compounds shown in Formula 1.

[0147] Li a Ni b Co c M d O e A f ···Formula 1

[0148] In Formula 1, 0.8 ≤ a ≤ 1.2, 0.5 ≤ b < 1, 0 < c < 1, 0 < d < 1, 1 ≤ e ≤ 2, 0 ≤ f ≤ 1, M is selected from one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, and B, and A is selected from one or more of N, F, S, and Cl.

[0149] In the present application, the modified compound of each of the above materials may be one obtained by doping modification or surface coating modification of the positive electrode active material.

[0150] In the secondary battery according to the present application, the positive electrode film layer generally includes a positive electrode active material, an optional adhesive, and an optional conductive agent, and is generally formed by applying, drying, and cold pressing a positive electrode slurry. The positive electrode slurry is generally formed by dispersing a positive electrode active material, an optional conductive agent, an adhesive, etc. in a solvent and uniformly stirring. The solvent may be N-methylpyrrolidone (NMP).

[0151] For example, the adhesive used for the positive electrode film layer may include one or more of polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE).

[0152] For example, the conductive agent used in the positive electrode film layer may include one or more of superconducting carbon, carbon black (e.g., acetylene black, ketjen black), carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0153] In the secondary battery according to the present application, the positive electrode current collector can be a metal foil piece or a composite current collector (a composite current collector can be formed by providing a metal material on a polymer substrate.) For example, the positive electrode current collector can be aluminum foil.

[0154] [Electrolyte]

[0155] The secondary battery according to the present invention is not particularly limited in the type of electrolyte, and can be selected as needed. The electrolyte can be selected from, for example, at least one of a solid electrolyte and a liquid electrolyte (i.e., an electrolytic solution).

[0156] In some embodiments, the electrolyte is an electrolytic solution, which includes an electrolyte salt and a solvent.

[0157] In some embodiments, the electrolyte salt can be chosen from one or more of LiPF (lithium hexafluorophosphate), LiBF (lithium tetrafluoroborate), LiClO (lithium perchlorate), LiAsF (lithium hexafluoroarsenate), LiFSI (lithium bis(fluorosulfonyl)imide), LiTFSI (lithium bis(trifluoromethanesulfonyl)imide), LiTFS (lithium trifluoromethanesulfonate), LiDFOB (lithium difluoro(oxalato)borate), LiBOB (lithium bis(oxalato)borate), LiPOF (lithium difluorophosphate), LiDFOP (lithium difluorobis(oxalato)phosphate), and LiTFOP (lithium tetrafluoro(oxalato)phosphate).

[0158] In some embodiments, the solvent can be chosen 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), 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), ethyl methyl sulfone (EMS), and diethyl sulfone (ESE).

[0159] In some embodiments, the electrolyte solution optionally contains an additive, such as an additive for forming a negative electrode film, an additive for forming a positive electrode film, or an additive for improving some performance of the battery, such as an additive for improving the overcharge performance of the battery, an additive for improving the high-temperature performance of the battery, or an additive for improving the low-temperature performance of the battery.

[0160] [Separator]

[0161] Secondary batteries using an electrolyte solution and some secondary batteries using a solid electrolyte further include a separator. The separator is disposed between the positive electrode plate and the negative electrode plate and serves to separate them. In the present application, the type of separator is not particularly limited, and any known separator with a porous structure having good chemical and mechanical stability can be used. In some embodiments, the material of the separator can be selected from one or more of glass fiber, nonwoven 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.

[0162] In some embodiments, the positive electrode plate, the negative electrode plate, and the separator can be formed into an electrode assembly by a winding process or a stacking process.

[0163] In some embodiments, the secondary battery can include an outer packaging, which is used to package the electrode assembly and electrolyte.

[0164] In some embodiments, the exterior of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, or a steel case. The exterior of the secondary battery may be a flexible package, such as a bag-type flexible package. The material of the flexible package may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc.

[0165] The present application does not particularly limit the shape of the secondary battery, and it may be cylindrical, rectangular, or any other shape. Fig. 5 shows a secondary battery 5 having a rectangular structure as an example.

[0166] In some embodiments, as shown in FIG. 6 , the exterior may include a housing 51 and a cover plate 53. The housing 51 may include a bottom plate and side plates connected to the bottom plate, which together form a surrounding storage chamber. The housing 51 has an opening communicating with the storage chamber, and the cover plate 53 covers the opening to close the storage chamber. The positive electrode plate, the negative electrode plate, and the separator may be formed into an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is sealed in the storage chamber. The electrode assembly 52 is impregnated with an electrolyte. The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and can be adjusted as needed.

[0167] In some embodiments, the secondary batteries can be assembled into a battery module, and the number of secondary batteries included in the battery module can be multiple, and the specific number can be adjusted based on the application and capacity of the battery module.

[0168] Fig. 7 shows an example of a battery module 4. As shown in Fig. 7, in the battery module 4, the plurality of secondary batteries 5 may be arranged in series along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the plurality of secondary batteries 5 may be fastened together with fasteners.

[0169] Optionally, the battery module 4 may further include a housing having a storage space for storing a plurality of secondary batteries 5.

[0170] In some embodiments, the battery modules can be further assembled into a battery pack, and the number of battery modules included in the battery pack can be adjusted based on the application and capacity of the battery pack.

[0171] 8 and 9 show an example of a battery pack 1. As shown in FIGS. 8 and 9, the battery pack 1 may include a battery case and a plurality of battery modules 4 provided in the battery case. The battery case includes an upper case 2 and a lower case 3, and the upper case 2 covers the lower case 3 to form an enclosed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery case in any manner.

[0172] Device

[0173] The present application further provides a device including at least one of the secondary batteries, battery modules, or battery packs of the present application. The secondary battery, battery module, or battery pack may be used as a power source for the device or as an energy storage means for the device. The device may be, but is not limited to, a mobile device (e.g., a mobile phone, a laptop, 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 car, an electric truck, etc.), a train, a ship, a satellite, an energy storage system, etc. The device can select a secondary battery, a battery module, or a battery pack according to its usage requirements.

[0174] An example device is shown in Figure 10. This device may be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the demand for high power output and high energy density, a battery pack or battery module can be used.

[0175] Other examples of the device may be a mobile phone, a tablet computer, a laptop computer, etc. These devices are generally required to be lightweight and thin, and can use a secondary battery as a power source.

[0176] Example

[0177] The following examples will more specifically illustrate the disclosure of the present application, but these examples are for illustrative purposes only, and various modifications and variations within the scope of the disclosure will be apparent to those skilled in the art. Unless otherwise specified, all parts, percentages, and ratios in the following examples are by weight. Furthermore, all reagents used in the examples are commercially available or can be synthesized according to conventional methods and can be used as is without further treatment. Furthermore, all instruments used in the examples are commercially available.

[0178] 1. Battery manufacturing

[0179] Example 1

[0180] Preparation of negative electrode active material

[0181] The petroleum raw coke with a volatile content C1 of 7.87% was used. The petroleum raw coke was crushed and v 50 is 11.8 μm and D v The coke raw material with a particle size of 20.1 μm was obtained.

[0182] The coke raw material is shaped and classified, v 50 is 13.0 μm and D v A precursor with a particle size of 21.3 μm was obtained.

[0183] The precursor is granulated using pitch as an adhesive, and the amount of adhesive used C2 is 5%. The obtained granules are D v 50 is 13.7 μm, and D v 99 is 21.9 μm.

[0184] The granulated material was graphitized at a temperature of 3000°C, and then sieved to obtain artificial graphite. v 99 is 22.9 μm.

[0185] Next, the artificial graphite is coated with pitch, which is an organic carbon source, and then carbonized to obtain a negative electrode active material having an organic carbon source usage amount C3 of 3%. The negative electrode active material includes an artificial graphite core and an amorphous carbon coating layer covering the surface of the artificial graphite core, and the negative electrode active material is D v 50 is 14.5 μm, D v 99 is 22.3 μm and the gram capacity is 355.2 mAh / g.

[0186] Preparation of negative electrode plate

[0187] The above-prepared negative electrode active material, styrene butadiene rubber (SBR) as an adhesive, sodium carboxymethylcellulose (CMC-Na) as a thickener, and carbon black (Super P) as a conductive agent were mixed in a weight ratio of 96.2:1.8:1.2:0.8 with an appropriate amount of deionized water and stirred thoroughly to form a uniform negative electrode slurry. The negative electrode slurry was then applied to the surface of a copper foil negative electrode current collector, followed by drying, cold pressing, striping, and cutting to obtain a negative electrode plate. The negative electrode plate had a compaction density of 1.65 g / cm. 3 , surface density is 123g / m 2 is.

[0188] Preparation of the positive electrode plate

[0189] Lithium Nickel Cobalt Manganese Oxide LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), conductive carbon black (Super P), and adhesive PVDF were mixed in a weight ratio of 97.5:1.5:1 with an appropriate amount of N-methylpyrrolidone (NMP) and thoroughly stirred to form a uniform cathode slurry. The cathode slurry was then applied to the surface of aluminum foil as a cathode current collector, followed by drying, cold pressing, striping, and cutting to obtain a cathode plate. The cathode plate had a compaction density of 3.5 g / cm. 3 and the areal density is 196 g / m 2 It was.

[0190] Separator

[0191] A polyethylene (PE) film was used as the separator.

[0192] Preparation of electrolyte

[0193] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1, and then thoroughly dried lithium salt LiPF6 was uniformly dissolved in the above solution to obtain an electrolyte solution with a LiPF6 concentration of 1 mol / L.

[0194] Secondary battery manufacturing

[0195] The positive electrode plate, separator, and negative electrode plate are stacked in this order, and a reference electrode (used for subsequent performance measurement of the battery sample, and can be a lithium sheet, lithium wire, etc., and the reference electrode should be separated by a separator to prevent contact with either the positive or negative electrode plate) is added between the separator and the negative electrode plate, and the electrode assembly is obtained through winding. The electrode assembly is then placed in a case, the above-mentioned electrolyte is added, and a secondary battery is obtained through processes such as sealing, standing, formation, and aging.

[0196] In Examples 2 to 20 and Comparative Examples 1 and 2, the manufacturing method is similar to that of Example 1, but the manufacturing parameters of the negative electrode active material are adjusted. Details of the different manufacturing parameters and product parameters are shown in Tables 2 to 5.

[0197] 2. Battery performance measurement

[0198] (1) Measurement of fast charging performance

[0199] At 25°C, the secondary batteries manufactured in the examples and comparative examples were charged at a constant current of 1C (i.e., a current value that completely discharges the theoretical capacity within 1 hour) to 4.25V, then charged at a constant voltage of 0.05C, allowed to stand for 5 minutes, and further discharged at a constant current of 1C to 2.8V, and the actual capacity was recorded as C0.

[0200] Next, the battery was charged at a constant current of 0.5C0, 1C0, 1.5C0, 2C0, 2.5C0, 3C0, 3.5C0, 4C0, and 4.5C0 in order to a negative electrode end potential of 4.25V or 0V (based on the first one reached). Each time charging was completed, it was necessary to discharge to 2.8V at 1C0. The corresponding negative electrode potential when charging to 10%, 20%, 30%, ... 80% SOC (State of Charge) at different charge rates was recorded, and the charge rate-negative electrode potential curves at different SOC states were drawn and linearly fitted to obtain the charge rate corresponding to when the negative electrode potential at different SOC states was 0V. This charge rate is the charge window at that SOC state, and each C 20%SOC , C30%SOC , C 40%SOC , C 50%SOC , C 60%SOC , C 70%SOC , C 80%SOC and the formula (60 / C 20%SOC +60 / C 30%SOC +60 / C 40%SOC +60 / C 50%SOC +60 / C 60%SOC +60 / C 70%SOC +60 / C 80%SOC ) × 10%, the charging time T (min) for this battery to charge from 10% SOC to 80% SOC was calculated. The shorter this time, the better the rapid charging performance of the battery.

[0201] (2) Measurement of cycle performance

[0202] At 25°C, the secondary batteries manufactured in the examples and comparative examples were charged at a constant current of 0.33 C to a charge cut-off voltage of 4.25 V, then charged at a constant voltage of 0.05 C, allowed to stand for 5 minutes, and then discharged at a constant current of 0.33 C to a discharge cut-off voltage of 2.8 V, and the initial capacity was recorded as C0. Thereafter, the secondary batteries were charged according to the method described in Table 1 and discharged at 0.33 C, and the cycle capacity retention rate (C n / C0×100%) until the discharge capacity C per cycle n The cycle time was recorded and the number of cycles was recorded. A higher number of cycles indicates a longer cycle life of the battery.

[0203] [Table 1]

[0204] The measurement results of Examples 1 to 20 and Comparative Examples 1 and 2 are shown in Tables 3 and 5 in detail.

[0205] [Table 2]

[0206] [Table 3]

[0207] As can be seen from the results in Table 3, the negative electrode active material according to the present invention has a core containing artificial graphite and a coating layer containing amorphous carbon that coats the surface of the core, and the negative electrode active material is D v 99≦24μm and 8μm≦D v By simultaneously satisfying the condition of 50≦15 μm, a secondary battery using this negative electrode active material can be improved in rapid charging capability and cycle performance under the condition of having a high energy density.

[0208] Comparative Example 1 does not satisfy the above conditions, and therefore is inferior in both quick charging capability and cycle performance.

[0209] [Table 4]

[0210] In Table 4, A = (C1 + C2) / U1 × 100%; B = (C1 + C2 + C3) / U2 × 100%

[0211] [Table 5]

[0212] As can be seen from the results of Examples 7 to 11, when the particle size uniformity of the negative electrode active material is also within an appropriate range, the rapid charge capability and cycle performance of the battery can be further improved.

[0213] As can be seen from the results of Examples 12 to 20, when the negative electrode active material further satisfies the requirement that its particle size-specific surface area or the ratio of the number of secondary particles is within an appropriate range, the rapid charging capability and cycle performance of the battery can be further improved.

[0214] The above content is merely a specific embodiment of the present application, and the scope of protection of the present application is not limited thereto. Those skilled in the art can easily devise various equivalent modifications and replacements within the technical scope disclosed in the present application, and all of these modifications and replacements fall within the scope of protection of the present application. Therefore, the scope of protection of the present application should be determined based on the scope of protection of the claims.

Claims

1. A negative electrode active material having a core containing artificial graphite and a coating layer containing amorphous carbon that coats at least a portion of a surface of the core, The particle size uniformity of the negative electrode active material is 0.25 to 0.45, and the volume particle size distribution D v 99≦24 μm, and D v 99 is the particle size corresponding to when the cumulative volume distribution percentage of the negative electrode active material reaches 99%.

2. The volume particle size distribution D of the negative electrode active material v 99 is 17 μm≦D v The negative electrode active material according to claim 1 , wherein the particle size satisfies 99≦24 μm.

3. The average volume particle diameter D of the negative electrode active material v 50 is 9 μm≦D v 50≦13 μm, and D v 50 is the particle size when the cumulative volume distribution percentage of the negative electrode active material reaches 50%.

4. 4. The negative electrode active material according to claim 1, wherein the particle size uniformity of the negative electrode active material is 0.32 to 0.

38.

5. The particle size specific surface area of ​​the negative electrode active material is 0.4 m 2 / g to 0.75m 2 The negative electrode active material according to any one of claims 1 to 4, wherein the average molecular weight of the negative electrode active material is 1 / g.

6. 6. The negative electrode active material according to claim 1, wherein the negative electrode active material contains secondary particles, and the ratio of the number of the secondary particles in the negative electrode active material is 50% or more.

7. The negative electrode active material has a density of 0.6≦(D v 90-D v 10) / D v 50≦1.8 is satisfied, and D v 90 is the particle size corresponding to when the cumulative volume distribution percentage of the negative electrode active material reaches 90%, and D v 10 is the particle size corresponding to when the cumulative volume distribution percentage of the negative electrode active material reaches 10%, and D v 7. The negative electrode active material according to claim 1, wherein 50 is the particle size corresponding to when the cumulative volume distribution percentage of the negative electrode active material reaches 50%.

8. The volume particle size distribution D of the negative electrode active material v The negative electrode active material according to any one of claims 1 to 7, wherein 90 is 13 µm to 18 µm.

9. The volume particle size distribution D of the negative electrode active material v 9. The negative electrode active material according to claim 1, wherein 10 is 5 μm to 10 μm.

10. The negative electrode active material further comprises (1) The graphitization degree of the negative electrode active material is 91.0% to 96.0%; (2) The gram capacity of the negative electrode active material is 345 mAh / g to 360 mAh / g; (3) The tap density of the negative electrode active material is 0.9 g / cm 3 ~1.3 g / cm 3 And, (4) The powder compaction density of the negative electrode active material at a pressure of 2 kN is 1.55 g / cm 3 ~1.67g / cm 3 The negative electrode active material according to any one of claims 1 to 9, which satisfies one or more of the following conditions:

11. A method for producing a negative electrode active material, comprising: A) providing a core comprising artificial graphite; B) coating the core to form a coating layer containing amorphous carbon on at least a portion of the surface of the core, thereby obtaining the negative electrode active material; The negative electrode active material has a particle size uniformity of 0.25 to 0.45 and satisfies D v 99≦24 μm; D v 99 is the particle size corresponding to when the cumulative volume distribution percentage of the negative electrode active material reaches 99%.

12. In the step A), the artificial graphite is produced by a) providing a coke feedstock; Step b) of subjecting the coke raw material to a shaping treatment to obtain a precursor; Step c) of granulating the precursor to obtain a granulated product; The granules are graphitized to obtain a volume average particle diameter D v 50 is 6 μm to 14 μm and the volume particle size distribution D v and step d) obtaining artificial graphite having a particle size of 17 μm to 26 μm. v 12. The method according to claim 11, wherein 50 is the particle size corresponding to when the cumulative volume distribution percentage of the negative electrode active material reaches 50%.

13. The volume average particle diameter D of the granules v 50 is 9 μm to 15 μm, and the volume particle size distribution D v 13. The method of claim 12, wherein 99 is 17 μm to 24 μm.

14. The volume average particle diameter D of the precursor v 50 is 8 μm to 13 μm, and the volume particle size distribution D v The method according to any one of claims 12 to 13, wherein 99 is 16 μm to 22 μm.

15. The volume average particle diameter D of the coke raw material v 50 is 7 μm to 12 μm, and the volume particle size distribution D v The method according to any one of claims 12 to 14, wherein 99 is 15 μm to 21 μm.

16. The particle size uniformity of the precursor is expressed as U 1 and 0.2≦U 1 ≦0.55, or The particle size uniformity of the artificial graphite is expressed as U 2 and 0.22≦U 2 The method according to any one of claims 12 to 15, wherein ≦0.48 is satisfied.

17. The volatile content of the coke raw material is C 1 The particle size uniformity of the precursor is U 1 and an adhesive is added in the granulation process of step c), and the amount of the adhesive used is C 2 and 21%≦(C 1 +C 2 ) / U 1 The method according to any one of claims 12 to 16, wherein x 100%≦50% is satisfied.

18. The volatile content C of the coke raw material 1 is 1%≦C 1 The method according to any one of claims 12 to 17, wherein the thickness satisfies ≦12%.

19. 19. The method of claim 12, wherein the coke feedstock comprises one or more of petroleum-based non-acid coke and petroleum-based needle coke.

20. The step B) The method according to any one of claims 11 to 19, further comprising a step e) of coating the core with an organic carbon source and forming an amorphous carbon coating layer on at least a portion of a surface of the core by heat treatment, thereby obtaining the negative electrode active material.

21. The step B) includes coating the core with an organic carbon source and forming an amorphous carbon coating layer on at least a part of the surface of the core by heat treatment to obtain the negative electrode active material, and the volatile content of the coke raw material is reduced to C 1 An adhesive is added to the granulation process of step c), and the amount of the adhesive used is C 2 The particle size uniformity of the artificial graphite is defined as U 2 The amount of the organic carbon source used is C 3 and 20%≦(C 1 +C 2 +C 3 ) / U 2 × 100%≦56%, 1.2%≦C 3 The method according to any one of claims 12 to 19, wherein the residual carbon rate is ≦2.5%.

22. A secondary battery comprising a negative electrode plate containing the negative electrode active material according to any one of claims 1 to 10.

23. A battery module comprising the secondary battery according to claim 22.

24. A battery pack comprising the secondary battery according to claim 22 or the battery module according to claim 23.

25. 25. An apparatus including at least one of the secondary battery according to claim 22, the battery module according to claim 23, or the battery pack according to claim 24.

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