Negative electrode material, preparation method and application thereof

Abstract

The application belongs to the technical field of batteries, and specifically discloses a negative electrode material and a preparation method and application thereof, the method comprising: selecting a first carbonaceous raw material and a second carbonaceous raw material, wherein the mass content of sulfur in the first carbonaceous raw material is 0.8% to 2.5%, and the mass content of sulfur in the second carbonaceous raw material is 0.1% to 0.5%; crushing the first carbonaceous raw material to obtain single-particle first carbonaceous powder; crushing and granulating the second carbonaceous raw material to obtain secondary-particle second carbonaceous powder; pre-carbonizing the first carbonaceous powder; graphitizing the pre-carbonized first carbonaceous powder to obtain first graphite; graphitizing the second carbonaceous powder to obtain second graphite; and mixing the first graphite and the second graphite to obtain the negative electrode material. The application can effectively make the prepared negative electrode material simultaneously have good rate performance, high compaction density, high energy density and good cycle performance.

Description

Technical Field

[0001] This application belongs to the field of battery technology, specifically relating to a negative electrode material, its preparation method, and its application. Background Technology

[0002] With the development of the energy storage industry and market demand, the energy density requirements for energy storage batteries are getting higher and higher. However, existing graphite materials cannot meet both the compaction density and long-cycle performance requirements.

[0003] Specifically, to meet the requirements of long-cycle operation, existing graphite materials require the use of raw materials with low aromaticity to be crushed and prepared into single particles, secondary particles, or compound particles. This results in low compaction density of graphite materials after being prepared into negative electrode sheets and rolled, which cannot meet the requirements of high volumetric energy density and mass energy density. Summary of the Invention

[0004] This application aims to at least partially address one of the technical problems in related technologies. Therefore, the purpose of this application is to provide a negative electrode material, its preparation method, and its application. This application can effectively enable the prepared negative electrode material to simultaneously achieve good rate performance, high compaction density, high energy density, and good cycle performance.

[0005] In one aspect of this application, a method for preparing a negative electrode material is provided. According to an embodiment of this application, the method includes:

[0006] Select a first carbonaceous raw material and a second carbonaceous raw material, wherein the mass content of sulfur in the first carbonaceous raw material is 0.8%~2.5%, and the mass content of sulfur in the second carbonaceous raw material is 0.1%~0.5%, the aromaticity of the first carbonaceous raw material is 0.68~0.8, and the aromaticity of the second carbonaceous raw material is 0.68~0.8; wherein, aromaticity = A 1630 / (A 1630 +A 1438 +A 1335 A 1630 This indicates the 1630cm in the Fourier transform infrared spectrum. -1 The intensity of the infrared characteristic peak, A 1438 This indicates that 1438 cm⁻¹ in the Fourier transform infrared spectrum -1 The intensity of the infrared characteristic peak, A 1335 This indicates that 1335 cm⁻¹ in the Fourier transform infrared spectrum -1 The intensity of infrared characteristic peaks;

[0007] The first carbonaceous raw material is crushed to obtain single-particle first carbonaceous powder.

[0008] The second carbonaceous raw material is crushed and granulated to obtain a second carbonaceous powder with secondary particles.

[0009] The first carbonaceous powder is pre-carbonized;

[0010] The first carbonaceous powder after pre-carbonization is graphitized to obtain the first graphite; the second carbonaceous powder is graphitized to obtain the second graphite.

[0011] The first graphite and the second graphite are mixed to obtain the negative electrode material;

[0012] The mass ratio of the first graphite to the second graphite is (3:7) to (8:2).

[0013] According to the method for preparing anode materials according to the embodiments of this application, a first carbonaceous raw material with a sulfur content in the range of 0.8% to 2.5% and an aromaticity in the range of 0.68 to 0.8 is formed into single particles, and a second carbonaceous raw material with a sulfur content in the range of 0.1% to 0.5% and an aromaticity in the range of 0.68 to 0.8 is formed into secondary particles. At the same time, the first graphite single particles formed after graphitization and the second graphite secondary particles formed after graphitization are compounded. This method can effectively enable the formed anode material to simultaneously achieve good rate performance, high compaction density, high energy density, and good cycle performance.

[0014] In addition, the method according to the above embodiments of this application may also have the following additional technical features:

[0015] In some embodiments of this application, the first carbonaceous raw material includes at least one of petroleum coke, needle coke, pitch coke, and shot coke; and / or, the second carbonaceous raw material includes at least one of petroleum coke, needle coke, pitch coke, and shot coke.

[0016] In some embodiments of this application, the particle size Dv50 of the first carbonaceous powder is 6µm~14µm, and the tap density of the first carbonaceous powder is 0.5g / cm³. 3 ~0.7g / cm 3 ; and / or, the particle size Dv50 of the second carbonaceous powder is 14.5µm~20.5µm, and the tap density of the second carbonaceous powder is 0.5g / cm³. 3 ~0.7g / cm 3 .

[0017] In some embodiments of this application, a binder is added during the granulation process, and the mass ratio of the second carbonaceous raw material to the binder is 100:(0~3); and / or, the temperature of the granulation process is 400℃~700℃.

[0018] In some embodiments of this application, the adhesive includes at least one of bitumen, heavy oil, and phenolic resin.

[0019] In some embodiments of this application, the temperature for pre-carbonizing the first carbonaceous powder is 700℃~1500℃, and the time is 2h~9h.

[0020] In some embodiments of this application, the graphitization temperature of the pre-carbonized first carbonaceous powder is 2400℃~3200℃; and / or, the graphitization temperature of the second carbonaceous powder is 2400℃~3200℃.

[0021] In a second aspect, this application proposes a negative electrode material. According to an embodiment of this application, the negative electrode material is prepared using the method described in the first aspect. Therefore, the negative electrode material can effectively simultaneously achieve good rate performance, high compaction density, high energy density, and good cycle performance.

[0022] In a third aspect, this application proposes a negative electrode sheet. According to an embodiment of this application, the negative electrode sheet comprises the negative electrode material prepared by the method described in the above embodiments. Therefore, the negative electrode sheet has high compaction density, high energy density, and good cycle performance.

[0023] In a fourth aspect, this application proposes a battery. According to an embodiment of this application, the battery has the negative electrode sheet described in the above embodiments. This effectively improves the battery's energy density, rate performance, and cycle performance.

[0024] A fifth aspect of this application discloses an energy storage device. According to an embodiment of this application, the energy storage device includes the battery described in the above embodiments. Therefore, the energy storage device possesses all the advantages of the battery described in the above embodiments, which will not be repeated here.

[0025] A sixth aspect of this application discloses an energy storage system. According to an embodiment of this application, the energy storage system includes: the battery or the energy storage device described in the above embodiments. Therefore, the energy storage system possesses all the advantages of the battery or the energy storage device, which will not be elaborated further here.

[0026] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0027] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0028] Figure 1This is a schematic diagram of the structure of an energy storage system according to some embodiments of this application;

[0029] Figure 2 This is a schematic diagram of the structure of an energy storage system according to some embodiments of this application;

[0030] Figure 3 This is a schematic diagram of the structure of an energy storage system according to some embodiments of this application. Detailed Implementation

[0031] The embodiments of this application are described in detail below. These embodiments are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0032] In one aspect of this application, a method for preparing a negative electrode material is proposed. According to an embodiment of this application, the method includes: selecting a first carbonaceous raw material and a second carbonaceous raw material, wherein the mass content of sulfur in the first carbonaceous raw material is 0.8%~2.5%, the mass content of sulfur in the second carbonaceous raw material is 0.1%~0.5%, the aromaticity of the first carbonaceous raw material is 0.68~0.8, and the aromaticity of the second carbonaceous raw material is 0.68~0.8; wherein, aromaticity = A 1630 / (A 1630 +A 1438 +A 1335 A 1630 This indicates the 1630cm in the Fourier transform infrared spectrum. -1 The intensity of the infrared characteristic peak, A 1438 This indicates that 1438 cm⁻¹ in the Fourier transform infrared spectrum -1 The intensity of the infrared characteristic peak, A 1335 This indicates that 1335 cm⁻¹ in the Fourier transform infrared spectrum -1The intensity of the infrared characteristic peak; the first carbonaceous raw material is crushed to obtain single-particle first carbonaceous powder; the second carbonaceous raw material is crushed and granulated to obtain secondary-particle second carbonaceous powder; the first carbonaceous powder is pre-carbonized; the pre-carbonized first carbonaceous powder is graphitized to obtain first graphite; the second carbonaceous powder is graphitized to obtain second graphite; the first graphite and the second graphite are mixed, and the mass ratio of the first graphite and the second graphite is (3:7)~(8:2) to obtain the negative electrode material. Therefore, this application forms single particles of a first carbonaceous raw material with a sulfur content in the range of 0.8% to 2.5% and an aromaticity in the range of 0.68 to 0.8, and forms secondary particles of a second carbonaceous raw material with a sulfur content in the range of 0.1% to 0.5% and an aromaticity in the range of 0.68 to 0.8. At the same time, the first graphite, which is formed into single particles after graphitization, and the second graphite, which is formed into secondary particles after graphitization, are compounded. This can effectively enable the formed negative electrode material to simultaneously achieve good rate performance, high compaction density, high energy density, and good cycle performance.

[0033] It should be noted that single particles refer to particles obtained directly from a single carbonaceous raw material through physical processing methods such as crushing and sieving. These particles are usually direct products of the original raw material and have not undergone further particle recombination or compounding. Secondary particles refer to particles formed after carbonaceous raw materials have undergone multiple processing steps (such as crushing, sieving, and agglomeration) through specific processes. These particles are usually composite particles formed by the agglomeration of multiple small particles through chemical or physical methods.

[0034] The principle behind the method for preparing the negative electrode material proposed in this application, which enables the above-mentioned beneficial effects, will be explained in detail below:

[0035] This application first selects a first carbonaceous raw material with an aromaticity in the range of 0.68 to 0.8 and a relatively high sulfur content (in the range of 0.8% to 2.5%) to form single particles, which can exhibit good electrochemical performance. However, since it is a single-particle carbonaceous raw material, its kinetic performance and compaction window still have room for improvement. Therefore, this application also selects a second carbonaceous raw material with an aromaticity in the range of 0.68 to 0.8 and a relatively low sulfur content (in the range of 0.1% to 0.5%) to introduce as a granulation product, which can further improve the compaction density and kinetic performance of the graphite anode material.

[0036] Meanwhile, for graphite anode materials, secondary granulation can significantly improve their kinetic performance and increase the compaction density to a certain extent. However, since most carbonaceous raw materials lack adhesiveness, a large amount of granulation binder (such as asphalt) needs to be introduced during the secondary granulation process. Due to the high impurity content and numerous structural defects of the granulation binder (such as asphalt), it generates soft carbon or low-graphitized graphite after heat treatment, resulting in numerous structural defects in the finished graphite. This leads to a decrease in the first-efficiency and cycle performance of the graphite anode material. Therefore, it is necessary to select carbonaceous raw materials with good self-adhesive properties and avoid or reduce the introduction of binders (such as asphalt) to improve the cycle performance of graphite anode materials.

[0037] For carbonaceous raw materials with an aromaticity range of 0.68 to 0.8, they will have a certain amount of volatile matter. However, for carbonaceous raw materials with a sulfur content range of 0.8% to 2.5%, their volatile matter contains a large amount of organic sulfur components such as thiols and thiophenes. These volatile components have small molecules and weak adhesion, resulting in weak self-adhesion of such carbonaceous raw materials. They tend to form single-particle samples, requiring the introduction of a large amount of binder (such as asphalt) during the granulation process. However, the binder (such as asphalt) cannot be transformed into graphite after graphitization but remains in an amorphous state on the graphite surface, resulting in many defects in the graphite anode material, poor cycle performance, and low first-efficiency. Therefore, this application forms the first carbonaceous powder with an aromaticity range of 0.68 to 0.8 and a relatively high sulfur content (range of 0.8% to 2.5%) into single particles.

[0038] When the sulfur content of the carbonaceous raw material is in the range of 0.1% to 0.5% and the aromaticity is in the range of 0.68 to 0.8, its volatile matter is in the range of 6% to 13%. At this time, the carbonaceous raw material can have a certain degree of self-adhesion at high temperature. Mixing at high temperature can complete granulation with minimal or no use of binders such as asphalt. At this time, the volatile matter after the sample polymerization will be transformed into graphitized carbon after graphitization. Since the proportion of amorphous carbon derived from asphalt is low, the overall graphite anode material has fewer defects, better cycle performance, and higher first-efficiency. Therefore, this application forms secondary particles from a second carbonaceous raw material with moderate aromaticity and a sulfur content in the range of 0.1% to 0.5%. The single-particle first carbonaceous powder is graphitized to form single-particle first graphite, and the secondary-particle second carbonaceous powder is graphitized to form secondary-particle second graphite. Therefore, by combining single-particle first graphite and secondary-particle second graphite, this application can effectively enable the formed anode material to simultaneously achieve good rate performance, high compaction density, high energy density, and good cycle performance.

[0039] Specifically, the above methods include:

[0040] S100: Select the first carbonaceous raw material and the second carbonaceous raw material;

[0041] In this step, a first carbonaceous raw material and a second carbonaceous raw material are selected. The first carbonaceous raw material has a sulfur content of 0.8% to 2.5% by mass (e.g., 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, 2.2%, 2.5%, etc.), and the second carbonaceous raw material has a sulfur content of 0.1% to 0.5% by mass (e.g., 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, etc.). This ensures that the sulfur content in the first carbonaceous powder particles formed after subsequent crushing is within the range of 0.8% to 2.5%, and that the sulfur content in the second carbonaceous powder particles formed after subsequent crushing and granulation is within the range of 0.1% to 0.5%. This effectively allows the formed anode material to simultaneously achieve good rate performance, high compaction density, high energy density, and good cycle performance.

[0042] In the embodiments of this application, the aromaticity of the first carbonaceous raw material is 0.68~0.8 (e.g., it can be 0.68, 0.7, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.8, etc.), and the aromaticity of the second carbonaceous raw material is 0.68~0.8 (e.g., it can be 0.68, 0.7, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.8, etc.); wherein, aromaticity = A 1630 / (A 1630 +A 1438 +A 1335 A 1630 This indicates the 1630cm in the Fourier transform infrared spectrum. -1 The intensity of the infrared characteristic peak corresponds to the absorption peak intensity of the C=C stretching vibration in aromatic hydrocarbons; A 1438 This indicates that 1438 cm⁻¹ in the Fourier transform infrared spectrum -1 The intensity of the infrared characteristic peak corresponds to the absorption peak intensity of the CH bending vibration of the saturated carmine (-CH2-); A 1335 This indicates that 1335 cm⁻¹ in the Fourier transform infrared spectrum -1The intensity of the infrared characteristic peak corresponds to the absorption peak intensity of the CH bending vibration of saturated carbon methyl (-CH3). This application, by limiting the aromaticity of both the first and second carbonaceous raw materials to the range of 0.68 to 0.8, can further effectively enable the formed anode material to simultaneously achieve good rate performance, high compaction density, high energy density, and good cycle performance. Specifically, the aromaticity can be detected and calculated using a Fourier transform infrared spectrometer, where the peak intensity of the infrared characteristic peak refers to the peak height, and the sulfur content can be detected and calculated with reference to SHT0313-1992.

[0043] Specifically, this application first selects a first carbonaceous raw material with an aromaticity in the range of 0.68 to 0.8 and a relatively high sulfur content (in the range of 0.8% to 2.5%) to form single particles, which can possess good electrochemical performance. However, since it is a single-particle carbonaceous raw material, its kinetic performance and compaction window still have room for improvement. Therefore, this application also selects a second carbonaceous raw material with an aromaticity in the range of 0.68 to 0.8 and a relatively low sulfur content (in the range of 0.1% to 0.5%) to introduce as granulation material, which can further improve the compaction density and kinetic performance of the graphite anode material.

[0044] Meanwhile, for graphite anode materials, secondary granulation can significantly improve their kinetic performance and increase the compaction density to a certain extent. However, since most carbonaceous raw materials lack adhesiveness, a large amount of granulation binder (such as asphalt) needs to be introduced during the secondary granulation process. Due to the high impurity content and numerous structural defects of the granulation binder (such as asphalt), it generates soft carbon or low-graphitized graphite after heat treatment, resulting in numerous structural defects in the finished graphite. This leads to a decrease in the first-efficiency and cycle performance of the graphite anode material. Therefore, it is necessary to select carbonaceous raw materials with good self-adhesive properties and avoid or reduce the introduction of binders (such as asphalt) to improve the cycle performance of graphite anode materials.

[0045] For carbonaceous raw materials with an aromaticity range of 0.68 to 0.8, they will have a certain amount of volatile matter. However, for carbonaceous raw materials with a sulfur content range of 0.8% to 2.5%, their volatile matter contains a large amount of organic sulfur components such as thiols and thiophenes. These volatile components have small molecules and weak adhesion, resulting in weak self-adhesion of such carbonaceous raw materials. They tend to form single-particle samples, requiring the introduction of a large amount of binder (such as asphalt) during the granulation process. However, the binder (such as asphalt) cannot be transformed into graphite after graphitization but remains in an amorphous state on the graphite surface, resulting in many defects in the graphite anode material, poor cycle performance, and low first-efficiency. Therefore, this application forms the first carbonaceous raw material with an aromaticity range of 0.68 to 0.8 and a relatively high sulfur content (range of 0.8% to 2.5%) into single particles.

[0046] When the sulfur content of the carbonaceous raw material is in the range of 0.1% to 0.5% and the aromaticity is in the range of 0.68 to 0.8, its volatile matter is in the range of 6% to 13%. At this time, the carbonaceous raw material can have a certain degree of self-adhesion at high temperature. Mixing at high temperature can complete granulation with minimal or no use of binders such as asphalt. At this time, the volatile matter after the sample polymerization will be transformed into graphitized carbon after graphitization. Since the proportion of amorphous carbon derived from asphalt is low, the overall graphite anode material has fewer defects, better cycle performance, and higher first-efficiency. Therefore, this application forms secondary particles from a second carbonaceous raw material with an aromaticity in the range of 0.68 to 0.8 and a sulfur content in the range of 0.1% to 0.5%. The single-particle first carbonaceous powder is graphitized to form single-particle first graphite, and the secondary-particle second carbonaceous powder is graphitized to form secondary-particle second graphite. Therefore, by combining single-particle first graphite and secondary-particle second graphite, this application can effectively enable the formed anode material to simultaneously achieve good rate performance, high compaction density, high energy density, and good cycle performance.

[0047] Furthermore, the inventors discovered that when the aromaticity of the first or second carbonaceous raw material is greater than 0.8, the resulting graphite anode material has insufficient lithium intercalation channels, leading to decreased kinetic performance. Simultaneously, the excessively high aromaticity results in volatiles with higher molecular weights, which are more prone to coking at high temperatures, hindering granulation and causing the second carbonaceous raw material to lack self-adhesion. This necessitates the introduction of a large amount of asphalt during the granulation process, further reducing the cycle performance of the graphite anode material. When the aromaticity of the first or second carbonaceous raw material is less than 0.68, the graphite crystallinity of the carbonaceous raw material is poor, resulting in a significant decrease in the compaction density of the graphite anode material and a reduction in the surface molecular weight of graphite, along with an increase in light components. This leads to decreased self-adhesion, requiring the introduction of binders such as asphalt during the granulation process, which in turn reduces the cycle performance of the graphite anode material.

[0048] In the embodiments of this application, the specific type of the first carbonaceous raw material is not particularly limited. As some preferred embodiments, the first carbonaceous raw material includes at least one of petroleum coke, needle coke, pitch coke and shot coke.

[0049] In the embodiments of this application, the specific type of the second carbonaceous raw material is not particularly limited. As some preferred embodiments, the second carbonaceous raw material includes at least one of petroleum coke, needle coke, pitch coke and shot coke.

[0050] According to some specific embodiments of this application, the particle size Dv50 of the first carbonaceous powder is 6µm~14µm (for example, it can be 6µm, 7µm, 8µm, 9µm, 10µm, 11µm, 12µm, 14µm, etc.), and the tap density of the first carbonaceous powder is 0.5g / cm³. 3 ~0.7g / cm 3 (For example, it can be 0.5g / cm) 3 0.52g / cm 3 0.54g / cm 3 0.56g / cm 3 0.58g / cm 3 0.6g / cm 3 0.62g / cm 3 0.64 g / cm 3 0.66 g / cm 3 0.68g / cm 3 0.7g / cm 3 (etc.). Specifically, the particle size Dv50 is obtained using a laser diffraction particle size distribution analyzer. Dv50 is the particle size measured when the cumulative volume fraction in the volume-based distribution reaches 50%. The tap density is determined by the following method: a 50 g sample is placed in a 100 ml graduated cylinder of the tap density tester, and the device is vibrated 5000 times at 250 times / minute. The sample volume is measured, and the tap density is calculated as weight / volume.

[0051] According to some specific embodiments of this application, the particle size Dv50 of the second carbonaceous powder is 14.5µm~20.5µm (for example, it can be 14.5µm, 15µm, 16µm, 17µm, 18µm, 19µm, 20µm, 20.5µm, etc.), and the tap density of the second carbonaceous powder is 0.5g / cm³. 3 ~ 0.7g / cm 3 (For example, it can be 0.5g / cm) 3 0.52g / cm 3 0.54g / cm 3 0.56g / cm 3 0.58g / cm 3 0.6g / cm 3 0.62g / cm 3 0.64 g / cm 3 0.66 g / cm 3 0.68g / cm 3 0.7g / cm 3(etc.). By limiting the particle size Dv50 and tap density of the second carbonaceous powder within the above range, the kinetic properties of the formed graphite anode material can be further significantly improved, and the compaction density of the graphite anode material can be further improved.

[0052] S200: Crushing the first carbonaceous raw material;

[0053] In this step, the first carbonaceous raw material is crushed, classified, and shaped to obtain single-particle first carbonaceous powder.

[0054] S300: Crushing and granulating the second carbonaceous raw material;

[0055] In this step, the second carbonaceous raw material is first crushed, classified, and shaped to obtain single particles of the second carbonaceous raw material, and then granulated to obtain secondary particles of the second carbonaceous powder.

[0056] It should be noted that the specific process of steps S200 and S300 is not particularly limited. Step S200 can be performed first and then step S300, or step S300 can be performed first and then step S200, or steps S200 and S300 can be performed simultaneously.

[0057] According to some specific embodiments of this application, a binder is added during the granulation process. The mass ratio of the second carbonaceous raw material to the binder is 100:(0~3), for example, it can be 100:0, 100:1, 100:2, 100:3, etc., preferably 100:0 (i.e., no binder is added). As mentioned above, when the sulfur content of the second carbonaceous raw material is in the range of 0.1%~0.5% and the aromaticity is in the range of 0.68~0.8, its volatile matter is in the range of 6%-13%. At this time, the carbonaceous raw material can have a certain degree of self-adhesion at high temperature. When mixed at high temperature, granulation can be completed with as little or no binder (such as asphalt). At this time, the volatile matter after the sample is polymerized will be transformed into graphitized carbon after graphitization. Since the proportion of amorphous carbon derived from the binder is low, the overall graphite anode material has fewer defects, better cycle performance, and higher first-time efficiency.

[0058] According to some specific embodiments of this application, the granulation temperature is 400℃~700℃ (e.g., 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, etc.). The second carbonaceous raw material has good self-adhesion within the above temperature range. Granulation can be completed with minimal or no use of binders such as asphalt. At this time, the volatiles after polymerization of the sample will be transformed into graphitized carbon after graphitization. Since the proportion of amorphous carbon derived from binders such as asphalt is low, the overall graphite anode material has fewer defects, better cycle performance, and higher first-efficiency. The inventors found that when the granulation temperature is below 400℃, the temperature is insufficient to allow the surface volatiles to melt and adhere, resulting in weak granulation effect. When the granulation temperature is above 700℃, the rapid evaporation and polymerization of surface volatiles leads to granulation failure.

[0059] In the embodiments of this application, the specific type of adhesive is not particularly limited. As some preferred embodiments, the adhesive includes at least one of asphalt, heavy oil and phenolic resin.

[0060] S400: Pre-carbonization of the first carbonaceous powder;

[0061] In this step, the first carbonaceous powder is pre-carbonized under an inert atmosphere to partially remove sulfur and volatiles, preventing excessive gas generation during graphitization, which could lead to excessive porosity and reduce furnace blasting risks. It also increases the graphite bulk density. The heat treatment equipment used for pre-carbonization includes, but is not limited to, tube furnaces, roller kilns, tunnel kilns, and rotary kilns.

[0062] According to some specific embodiments of this application, the temperature for pre-carbonizing the first carbonaceous powder is 700℃~1500℃ (e.g., 700℃, 800℃, 900℃, 1000℃, 1100℃, 1200℃, 1300℃, 1400℃, 1500℃, etc.), and the time is 2h~9h (e.g., 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, etc.), thereby ensuring that the first carbonaceous powder is fully pre-carbonized.

[0063] It should be noted that the aforementioned second carbonaceous powder may or may not be pre-carbonized. The reason is that the graphitization process of the second carbonaceous raw material with low sulfur content produces less gas and will not generate significant pores.

[0064] S500: Graphitize the first carbonaceous powder after pre-carbonization, and graphitize the second carbonaceous powder;

[0065] In this step, the pre-carbonized first carbonaceous powder is graphitized to obtain first graphite; the second carbonaceous powder is graphitized to obtain second graphite. During graphitization, the polycyclic aromatic components in the carbonaceous raw material gradually polymerize to form carbon rings, thereby forming graphite, and sulfur will be released during this process.

[0066] According to some specific embodiments of this application, the graphitization temperature of the pre-carbonized first carbonaceous powder is 2400℃~3200℃ (for example, it can be 2400℃, 2500℃, 2600℃, 2700℃, 2800℃, 2900℃, 3000℃, 3100℃, 3200℃, etc.), thereby ensuring that the pre-carbonized first carbonaceous powder is fully graphitized.

[0067] According to some specific embodiments of this application, the graphitization temperature of the second carbonaceous powder is 2400℃~3200℃ (for example, it can be 2400℃, 2500℃, 2600℃, 2700℃, 2800℃, 2900℃, 3000℃, 3100℃, 3200℃, etc.), thereby ensuring that the second carbonaceous powder is fully graphitized.

[0068] S600: The first graphite and the second graphite are mixed to obtain the negative electrode material.

[0069] In this step, the first graphite and the second graphite are mixed in a preset ratio to obtain the negative electrode material.

[0070] According to some specific embodiments of this application, the mass ratio of the first graphite and the second graphite is (3:7) to (8:2), for example, it can be 3:7, 5:7, 5:5, 7:3, 8:2, etc., thereby further effectively enabling the negative electrode material to simultaneously achieve good rate performance, high compaction density, high energy density and good cycle performance.

[0071] In a second aspect, this application proposes a negative electrode material. According to an embodiment of this application, the negative electrode material is prepared using the method of the first aspect. Therefore, the negative electrode material can effectively simultaneously achieve good rate performance, high compaction density, high energy density, and good cycle performance.

[0072] In a third aspect, this application proposes a negative electrode sheet. According to an embodiment of this application, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least a portion of the surface of the negative electrode current collector; the negative electrode active material layer comprises a negative electrode material prepared by the method described in the above embodiments. Therefore, this negative electrode sheet has high compaction density, high energy density, and good cycle performance.

[0073] In some embodiments of this application, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc.).

[0074] In some embodiments of this application, the negative electrode active material layer may optionally include a binder. The binder may include at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0075] In some embodiments of this application, the negative electrode active material layer may optionally include a conductive agent. The conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0076] The preparation method of the negative electrode sheet includes: mixing the negative electrode material, conductive agent and negative electrode binder evenly according to the preset ratio, adding solvent and stirring evenly to form a negative electrode slurry, then coating it onto the current collector, drying it, and finally cutting it into a specific shape of negative electrode sheet for later use according to the different battery casings.

[0077] In a fourth aspect, this application proposes a battery. According to an embodiment of this application, the battery has the negative electrode sheet described in the above embodiments. This effectively improves the battery's energy density, rate performance, and cycle performance.

[0078] In the embodiments of this application, the battery described above can be either a lithium-ion battery or a sodium-ion battery. The following explanation uses a lithium-ion battery as an example.

[0079] Typically, a lithium-ion battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, lithium ions repeatedly insert and extract between the positive and negative electrodes. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing lithium ions to pass through.

[0080] The positive electrode sheet includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, wherein the positive active material layer includes a positive active material. The specific type of positive active material is not particularly limited; as some specific embodiments, the positive active material includes at least one of lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, lithium nickel oxide, lithium cobalt phosphate, lithium manganese phosphate, lithium nickel phosphate, lithium manganese oxide, binary materials, and ternary materials.

[0081] In some embodiments of this application, the positive electrode current collector may include a metal foil or a composite positive electrode current collector. For example, the metal foil may be aluminum foil. The composite positive electrode current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. For example, the composite positive electrode current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc.).

[0082] In some embodiments of this application, the positive electrode active material layer may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments of this application, the positive electrode active material layer may also optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polyamide (PA), polyacrylonitrile (PAN), polyacrylate, polyethylene ether, polymethyl methacrylate (PMMA), polyhexamethylene propylene, and styrene-butadiene rubber (SBR).

[0083] In the embodiments of this application, the battery further includes an electrolyte, which includes an electrolyte salt and a solvent. The specific types and components of the electrolyte salt and the organic solvent are not specifically limited and can be selected according to actual needs.

[0084] The specific material of the diaphragm is not particularly limited. As some specific embodiments, the diaphragm includes at least one of PP diaphragm, PE diaphragm, single-sided ceramic diaphragm, double-sided ceramic diaphragm, non-woven fabric diaphragm, and glass fiber diaphragm.

[0085] The battery of this application may be in the form of a battery cell, a battery module, or a battery pack. In some embodiments, battery cells may be assembled into a battery module, and the number of battery cells contained in a battery module may be one or more, the specific number of which can be selected by those skilled in the art based on the application and capacity of the battery module. In some embodiments, battery modules may also be assembled into a battery pack, and the number of battery modules contained in a battery pack may be one or more, the specific number of which can be selected by those skilled in the art based on the application and capacity of the battery pack.

[0086] A fifth aspect of this application discloses an energy storage device. According to an embodiment of this application, the energy storage device includes the battery described in the above embodiments. Therefore, the energy storage device possesses all the advantages of the battery described in the above embodiments, which will not be repeated here.

[0087] Because the energy we need is highly time- and space-dependent, in order to utilize energy rationally and improve energy efficiency, it is necessary to store one form of energy in the same way or by converting it into another, and then release it in a specific energy form based on future application needs. Currently, the main way to generate green electricity is to develop green energy sources such as photovoltaics and wind power to replace fossil fuels.

[0088] Currently, the generation of green electricity generally relies on solar, wind, and hydropower. However, wind and solar power are characterized by strong intermittency and large fluctuations, which can cause grid instability, insufficient power during peak demand periods, and excessive power during off-peak periods. Unstable voltage can also damage the power grid. Therefore, insufficient electricity demand or insufficient grid capacity can lead to the problem of "wind and solar curtailment." Solving these problems requires energy storage. This involves converting electrical energy into other forms of energy through physical or chemical means and storing it. When needed, this energy can be converted back into electrical energy and released. Simply put, energy storage is like a large "power bank," storing electrical energy when solar and wind power are abundant and releasing the stored electricity when needed.

[0089] This application provides an energy storage device 440, which is applied to an energy storage system 400. The energy storage device 440 is equipped with the battery described in the above embodiments. It mainly uses the chemical elements in the battery as the energy storage medium. The charging and discharging process is accompanied by the chemical reaction or change of the energy storage medium. Simply put, it stores the electrical energy generated by wind and solar energy in the chemical battery. When the use of external electrical energy reaches its peak, the stored electrical energy is released for use, or transferred to places with a shortage of electricity for use.

[0090] Current energy storage applications are quite widespread, including generation-side energy storage, grid-side energy storage, and consumption-side energy storage. The corresponding energy storage devices 440 include:

[0091] (1) Large-scale energy storage power stations applied to wind power and photovoltaic power stations can help renewable energy power generation meet grid connection requirements and improve the utilization rate of renewable energy. As a high-quality active / reactive power regulation power source on the power supply side, energy storage power stations can achieve load matching of power in time and space, enhance the absorption capacity of renewable energy, reduce instantaneous power changes, reduce the impact on the power grid, improve the absorption of new energy power generation, and are of great significance in power grid system backup, alleviating peak load power supply pressure and peak regulation and frequency regulation.

[0092] (2) Energy storage containers applied on the grid side mainly function as peak shaving, frequency regulation and grid congestion relief. In terms of peak shaving, they can realize peak shaving and valley filling of electricity load, that is, charging the energy storage battery when the electricity load is low and releasing the stored electricity during the peak electricity load period, thereby achieving a balance between power production and consumption.

[0093] (3) Small energy storage cabinets applied to the electricity consumption side mainly function as self-consumption of electricity, peak-valley price arbitrage, capacity cost management, and improvement of power supply reliability. Depending on the application scenario, electricity consumption side energy storage can be divided into industrial and commercial energy storage cabinets, household energy storage devices 440, energy storage charging piles, etc., which are generally used in conjunction with distributed photovoltaics. Industrial and commercial users can use energy storage for peak-valley price arbitrage and capacity cost management. In the electricity market implementing peak-valley pricing, by charging the energy storage system 400 when the electricity price is low and discharging the energy storage system 400 when the electricity price is high, peak-valley price arbitrage can be achieved, reducing electricity costs. In addition, industrial enterprises subject to two-part tariffs can use the energy storage system 400 to store energy during the low electricity consumption period and discharge during the peak load period, thereby reducing peak power and the maximum demand declared, and achieving the goal of reducing capacity electricity costs. Household photovoltaics with energy storage can improve the level of self-consumption of electricity. Due to high electricity prices and poor power supply stability, the demand for household photovoltaic installations is driven. Given that photovoltaic power generation occurs during the day, while user load is generally higher at night, configuring energy storage can better utilize photovoltaic power, improve self-consumption levels, and reduce electricity costs. Furthermore, energy storage is needed in areas such as communication base stations and data centers for backup power.

[0094] Optionally, the energy storage device 440 may include, but is not limited to, energy storage applications such as energy storage power stations, hydropower / thermal / wind power generation systems, solar power generation systems, mobile power systems, smart home systems, or temporary power supply systems, and may also be applied in multiple fields such as data centers, military equipment, aerospace, charging piles, and electric vehicles.

[0095] Optionally, the energy storage device 440 may include, but is not limited to, a single battery cell, or a battery module, battery pack, battery cluster, power bank, energy storage cabinet / container, or other battery integrated system composed of single batteries. The actual application form of the energy storage device 440 provided in this application embodiment may be, but is not limited to, the listed products, and may also be other application forms. This application embodiment does not strictly limit the application form of the energy storage device 440. This application embodiment only uses a multi-cell battery as an example for illustration.

[0096] Optionally, when the energy storage device 440 is a single battery, the energy storage device 440 can be, but is not limited to, at least one of cylindrical, square, prismatic, or other shaped batteries.

[0097] Optionally, the single battery cell can be a rechargeable battery, which refers to a battery cell that can be recharged after discharge to activate the active materials and continue to be used. The battery cell can be a lithium-ion battery, sodium-ion battery, sodium-lithium-ion battery, lithium metal battery, sodium metal battery, lithium-sulfur battery, magnesium-ion battery, nickel-metal hydride battery, nickel-cadmium battery, lead-acid battery, etc., and this application does not specifically limit it.

[0098] A sixth aspect of this application discloses an energy storage system. According to an embodiment of this application, the energy storage system includes: the battery or the energy storage device described in the above embodiments. Therefore, the energy storage system possesses all the advantages of the battery or the energy storage device, which will not be elaborated further here.

[0099] In some embodiments, see Figure 1 , Figure 1 This is a schematic diagram of the structure of an energy storage system 400 according to an embodiment of this application. Figure 1 The embodiments are illustrated using a home energy storage scenario in user-side energy storage as an example. The energy storage device 440 of this application is not limited to the home energy storage scenario.

[0100] This application provides an energy storage system 400, which includes a first power conversion device 410 (photovoltaic panel), a first user load 420 (household lighting fixture), a second user load 430 (e.g., household appliances such as air conditioners), and an energy storage device 440. The energy storage device 440 is a small energy storage box that can be wall-mounted on an outdoor wall. However, the energy storage device 440 is not limited to wall mounting and can also be placed in a user's residence in other ways. Specifically, the photovoltaic panel can convert solar energy into electrical energy during periods of low electricity prices, and the energy storage device 440 stores this electrical energy and supplies it to lighting fixtures and household appliances during peak electricity prices, or provides power during power outages / power interruptions.

[0101] In some embodiments, see Figure 2 , Figure 2 This is a schematic diagram of the structure of an energy storage system 400 according to an embodiment of this application, and this application Figure 2 The embodiments are illustrated using a shared energy storage scenario on the generation / distribution side as an example. The energy storage device 440 of this application is not limited to the energy storage scenario on the generation / distribution side.

[0102] This application provides an energy storage system 400, which includes: a high-voltage cable 450, a first power conversion device 410, a second power conversion device 460, and an energy storage device 440 provided in this application. In some embodiments of the power generation scenario, the second power conversion device 460 can be a wind power conversion device. Since the electricity generated by wind power conversion is volatile, random, and intermittent, the unstable electricity output by the wind power conversion device can be stored in the energy storage device 440 through grid connection. The energy storage device 440 is connected to the high-voltage cable and outputs smooth electricity to the power consumption side of the distribution network, realizing peak shaving and frequency regulation, and stable grid operation; or, wind power... The conversion device is always connected to the high-voltage cable. Under normal power generation conditions, the power output of the wind power conversion device is supplied to the power consumption side of the distribution network through the high-voltage cable. When the current power load is low and the wind power conversion device generates excess power, the excess power is first stored in the energy storage device 440 to reduce wind and solar curtailment rates and improve the problem of new energy power generation consumption. When the power load is high, the power grid issues an instruction to transmit the power stored in the energy storage device 440 together with the high-voltage cable 450 in grid-connected mode to supply power to the power consumption side. This provides the power grid with various services such as peak shaving, frequency regulation, and backup, giving full play to the peak shaving role of the power grid, promoting peak shaving and valley filling, and alleviating the power supply pressure of the power grid.

[0103] In some embodiments on the distribution network side, the first power conversion device 410 can be a photovoltaic power conversion device, and the energy storage device 440 is connected to the high-voltage cable 450 and installed downstream of the high-voltage cable 450 and between the user load. The power output of the photovoltaic power conversion device is stored in the energy storage device 440, which can respond in a timely manner to act as a backup power source when the power grid / distribution network fails; or, it can provide power supply support to alleviate line congestion when the high-voltage cable 450 transmission line is blocked, and to delay the economic pressure caused by the expansion of the power grid / distribution capacity when the power grid is planned to be expanded.

[0104] Optionally, the first power conversion device 410 may include, but is not limited to, a wind power conversion device, and the second power conversion device 460 may include, but is not limited to, a photovoltaic power conversion device. The first power conversion device 410 and the second power conversion device 460 can convert at least one of solar energy, light energy, wind energy, thermal energy, tidal energy, biomass energy, and mechanical energy into electrical energy.

[0105] In some embodiments, see Figure 3 , Figure 3 This is a schematic diagram of the structure of an energy storage system 400 according to an embodiment of this application, and this application Figure 3 The embodiments are illustrated using an industrial and commercial energy storage scenario as an example. The energy storage device 440 of this application is not limited to its power generation / distribution side energy storage scenario.

[0106] This application provides an energy storage system 400, which includes: an energy storage cabinet 470, a high-voltage cable 450, a factory equipped with a first power conversion device 410, a photovoltaic-energy storage-charging station 480 equipped with a second power conversion device 460, and a vehicle 490. In some embodiments of industrial and commercial scenarios, the first power conversion device 410 can be a photovoltaic panel, which converts solar energy into electrical energy and stores it in the energy storage cabinet 470 of the factory. In the event of a power grid failure, the energy storage cabinet 470 provides power to ensure the safe and stable operation of the factory without interruption. Alternatively, when the factory's power load is high, the power grid issues an instruction to transmit the electricity stored in the energy storage cabinet 470 in conjunction with the high-voltage cable 450 in a grid-connected mode to supply the factory with electricity, providing various services such as peak shaving / frequency regulation and backup for the power grid operation. In addition, the second power conversion device 460 can also be a photovoltaic panel, which converts solar energy into electrical energy and stores it in the energy storage cabinet 470 of the photovoltaic-energy storage-charging station 480, directly charging the vehicle 490 through the photovoltaic-energy storage-charging station 480, which is fast and convenient.

[0107] Optionally, the first power conversion device 410 and the second power conversion device 460 may include, but are not limited to, photovoltaic power conversion devices. The first power conversion device 410 can convert at least one of solar energy, light energy, wind energy, thermal energy, tidal energy, biomass energy, and mechanical energy into electrical energy.

[0108] Optionally, the energy storage cabinet 470 may include, but is not limited to, energy storage application scenarios such as energy storage power stations, hydropower / thermal / wind power generation systems, solar power generation systems, mobile power systems, smart home systems, or temporary power supply systems, and is also used in multiple fields such as data centers, military equipment, aerospace, charging piles, and electric vehicles.

[0109] Optionally, the energy storage cabinet 470 may include, but is not limited to, individual batteries, or battery modules, battery packs, battery clusters, power banks, energy storage cabinets / containers, and other integrated battery systems composed of individual batteries. The actual application form of the energy storage cabinet 470 provided in this application embodiment can be, but is not limited to, the listed products, and can also be other application forms. This application embodiment does not strictly limit the application form of the energy storage cabinet 470. This application embodiment only uses a multi-cell battery in the energy storage cabinet 470 as an example for illustration.

[0110] Optionally, the individual battery cells constituting the energy storage cabinet 470 can be, but are not limited to, at least one of cylindrical, prismatic, prismatic, or other shaped batteries.

[0111] The embodiments of this application are described in detail below. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. In addition, unless otherwise specified, all reagents used in the following embodiments are commercially available or can be synthesized according to the methods described herein or known methods. For reaction conditions not listed, they are also readily available to those skilled in the art.

[0112] Example 1

[0113] (1) Preparation of the negative electrode sheet, including the following steps:

[0114] 1) Select the first carbonaceous feedstock A (petroleum coke) with an aroma content of 72.5% and a sulfur mass content of 1.8%; select the second carbonaceous feedstock B (petroleum coke) with an aroma content of 73.2% and a sulfur mass content of 0.2%.

[0115] 2) The first carbonaceous raw material A and the second carbonaceous raw material B were crushed and shaped respectively. The first carbonaceous raw material A had a Dv50 of 12µm and a tap density of 0.58g / cm³. 3 The first carbonaceous powder A and raw material B yielded a Dv50 of 10µm and a tap density of 0.57g / cm³. 3 Powder B.

[0116] 3) Granulation of powder B was performed using a granulation reactor at a granulation temperature of 600℃ to obtain second carbonaceous powder B. The Dv50 of the second carbonaceous powder was controlled at 17.5µm, and the tap density was 0.55g / cm³. 3 .

[0117] 4) The first carbonaceous powder is pre-carbonized at a temperature of 700℃ for 4 hours.

[0118] 5) The first carbonaceous powder after carbonization and the second carbonaceous powder after granulation were graphitized. The maximum temperature of graphitization was 3100℃, and the total heating, holding and cooling time was 25 days.

[0119] 6) The graphitized powder was demagnetized and sieved to obtain the first graphite and the second graphite.

[0120] 7) Mix the first graphite and the second graphite in a mass ratio of 3:7 to obtain the finished graphite anode material.

[0121] Graphite anode material, conductive carbon SP, thickener CMC, and binder SBR are dispersed in deionized water at a mass ratio of 96.5:0.5:1:2 and mixed evenly to obtain anode slurry. The anode slurry is coated onto copper foil for anode current collector, and after drying, cold pressing, slitting, and cutting, anode sheets are obtained.

[0122] (2) Preparation of positive electrode sheet

[0123] Lithium iron phosphate (LiFePO4), conductive carbon black (SP), and polyvinylidene fluoride (PVDF) binder are dispersed in the organic solvent N-methylpyrrolidone (NMP) and mixed evenly to obtain a positive electrode slurry. The mass ratio of LiFePO4, conductive carbon black, and PVDF is 97:0.7:2.3. The positive electrode slurry is coated onto aluminum foil as a positive electrode current collector. After drying, cold pressing, slitting, and cutting, the positive electrode sheet is obtained.

[0124] (3) Electrolyte preparation:

[0125] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain a mixed solvent. Dry lithium salt LiPF6 was added to the mixed solvent to prepare an electrolyte with a LiPF6 concentration of 1 mol / L.

[0126] (4) Assemble the button cell battery:

[0127] In an argon-filled glove box, the positive electrode, separator (using a 16-micrometer-thick polyethylene film), and negative electrode are stacked in sequence to obtain a battery cell. The separator must completely isolate the positive and negative electrode. The stacked battery cell is then placed in a metal casing and injected with the electrolyte.

[0128] Example 2-12

[0129] The preparation methods of Examples 2-12 are basically the same as those of Example 1, with the differences shown in Table 1. In Example 2, during the granulation process of powder B using a granulation kettle, asphalt, a granulation binder, was added, and the amount added is shown in Table 1.

[0130] Table 1

[0131]

[0132] Example 13

[0133] The preparation method of Example 13 is basically the same as that of Example 1, except that:

[0134] 3) Granulate powder B using a granulation kettle at a granulation temperature of 400℃.

[0135] Example 14

[0136] The preparation method of Example 14 is basically the same as that of Example 1, except that:

[0137] 3) Granulate powder B using a granulation kettle at a granulation temperature of 700℃.

[0138] Example 15

[0139] The preparation method of Example 15 is basically the same as that of Example 1, except that:

[0140] 4) The first carbonaceous powder is pre-carbonized at a temperature of 1000℃ for 4 hours.

[0141] Example 16

[0142] The preparation method of Example 16 is basically the same as that of Example 1, except that:

[0143] 4) The first carbonaceous powder is pre-carbonized at a temperature of 1500℃ for 2 hours.

[0144] Example 17

[0145] The preparation method of Example 17 is basically the same as that of Example 1, except that:

[0146] 5) The first carbonaceous powder after carbonization and the second carbonaceous powder after granulation are respectively subjected to graphitization treatment at a maximum temperature of 2400℃.

[0147] Example 18

[0148] The preparation method of Example 18 is basically the same as that of Example 1, except that:

[0149] 5) The first carbonaceous powder after carbonization and the second carbonaceous powder after granulation are respectively subjected to graphitization treatment at a maximum temperature of 3200℃.

[0150] Comparative Examples 1-9

[0151] The preparation methods of Comparative Examples 1 to 9 are basically the same as those of Example 1, with the differences shown in Table 1.

[0152] The specific capacity of the graphite anode materials prepared in Examples 1-18 and Comparative Examples 1-9 was tested, and the results are shown in Table 2. The test methods are as follows:

[0153] The coin cell assembled with the negative electrode and lithium-ion battery was tested on the test system using the following test method: ① After the battery was left to stand for 4 hours, it was discharged at a constant current of 0.1C to 0.005V and left to stand for 10 minutes; ② Then it was discharged at a current of 0.05mA to 0.005V and left to stand for 10 minutes; ③ Then it was discharged at a current of 0.01mA to 0.005V and left to stand for 10 minutes; ④ The battery was charged at a current density of 0.1C to 2V, and the specific capacity obtained in the final charging process was taken as the specific capacity of the negative electrode.

[0154] The compaction density of the negative electrode sheets prepared in Examples 1-18 and Comparative Examples 1-9 was tested, and the results are shown in Table 2. The test methods are as follows:

[0155] The negative electrode sheet is passed through a roller press under a pressure of 20T to obtain the negative electrode sheet. The mass of the negative electrode sheet per unit area, the mass of the negative electrode foil, and the thickness of the negative electrode active layer are measured. Compacted density = negative electrode sheet surface density / (negative electrode active layer thickness × unit area), where negative electrode sheet surface density = (mass of negative electrode sheet per unit area - mass of negative electrode foil per unit area) / unit area.

[0156] The first efficiency, lithium plating window, and capacity retention at 1000cls of the coin cells prepared in Examples 1-18 and Comparative Examples 1-9 were tested respectively, and the results are shown in Table 2.

[0157] The first-effect test method is as follows:

[0158] The coin cell assembled with the negative electrode and lithium-ion battery was tested on the test system using the following test method: ① After the battery was left to stand for 4 hours, it was discharged at a constant current of 0.1C to 0.005V and left to stand for 10 minutes; ② Subsequently, it was discharged at a current of 0.05mA to 0.005V and left to stand for 10 minutes; ③ Subsequently, it was discharged at a current of 0.01mA to 0.005V and left to stand for 10 minutes; ④ The battery was charged to 2V at a current density of 0.1C. Then, the initial efficiency = charging capacity / discharging capacity.

[0159] The lithium plating window test method is as follows:

[0160] Ten lithium-ion batteries were taken from each group prepared in the comparative examples and embodiments. First, the batteries were placed at 25°C for 1 hour. Then, two batteries were grouped together and charged to 3.65V at constant power of 1P, 1.1P, 1.2P, 1.4P, 1.6P, 1.8P, 2P, 2.1P, and 2.2P respectively. After resting for 30 minutes, they were discharged to 2.5V at constant power of 1P, 1.1P, 1.2P, 1.4P, 1.6P, 1.8P, 2P, 2.1P, and 2.2P respectively. After resting for 30 minutes, the batteries were charged to 3.65V at constant power of 1P, 1.1P, 1.2P, 1.4P, 1.6P, 1.8P, 2P, 2.1P, and 2.2P respectively. The batteries were then disassembled, and the lithium plating on the negative electrode surface was observed.

[0161] The 1000cls capacity retention rate test method is as follows:

[0162] Two lithium-ion batteries from each of the comparative examples and embodiments were taken, and the average value was calculated. The lithium-ion batteries were repeatedly charged and discharged using the following steps, and the discharge capacity retention rate of the lithium-ion batteries was calculated.

[0163] First, in an environment of 45℃, the first charge and discharge cycle was performed. Constant power charging was performed at 1P charging power until the upper limit voltage of 3.65V was reached, then constant voltage charging was switched. Then constant power discharging was performed at 1P discharging power until the final voltage was 2.5V. This was repeated twice, and the discharge capacity of the second cycle was recorded. Then 1000 charge and discharge cycles were performed, and the discharge capacity of the 1000th cycle was recorded.

[0164] Capacity retention rate after 1000 cycles = (Discharge capacity of the 1000th cycle / Discharge capacity of the second cycle) × 100%.

[0165] Table 2

[0166]

[0167] As shown in Table 2, compared with Comparative Examples 1-9, the overall performance of Examples 1-18, including specific capacity, negative electrode compaction density, first-time efficiency, lithium plating window, and 1000cls capacity retention, is significantly improved. This application demonstrates that by forming a first carbonaceous raw material with a sulfur content ranging from 0.8% to 2.5% into single particles, and a second carbonaceous raw material with a sulfur content ranging from 0.1% to 0.5% into secondary particles, and then compounding the single-particle first carbonaceous raw material and the secondary-particle second carbonaceous raw material, the resulting negative electrode material exhibits high specific capacity, a high negative electrode compaction density, and the battery demonstrates high first-time efficiency, a high lithium plating window, and a high 1000cls capacity retention.

[0168] As can be seen from Table 2, compared with Example 1, the sulfur content of the first carbonaceous raw material in Comparative Example 1 is too high, which leads to a significant reduction in the specific capacity of the negative electrode material, the compaction density of the negative electrode sheet, the first efficiency of the battery, the lithium plating window, and the capacity retention rate at 1000cls.

[0169] As can be seen from Table 2, compared with Example 1, the sulfur content of the first carbonaceous raw material in Comparative Example 3 is too low, which leads to a significant reduction in the specific capacity of the negative electrode material, the compaction density of the negative electrode sheet, the first efficiency of the battery, and the capacity retention rate at 1000cls.

[0170] As can be seen from Table 2, compared with Example 1, the sulfur content of the first carbonaceous raw material in Comparative Example 2 is too low and the sulfur content of the second carbonaceous raw material is too high, which leads to a significant reduction in the specific capacity of the negative electrode material, the compaction density of the negative electrode sheet, the first efficiency of the battery, and the capacity retention rate at 1000cls.

[0171] As can be seen from Table 2, compared with Example 1, the sulfur content of the second carbonaceous raw material in Comparative Example 4 is too high, which leads to a significant reduction in the first efficiency, lithium plating window and 1000cls capacity retention of the battery in Comparative Example 4.

[0172] As can be seen from Table 2, compared with Example 1, the sulfur content of the first carbonaceous raw material in Comparative Example 5 is too low and the aromaticity is too high, which leads to a significant reduction in the first efficiency, lithium plating window and 1000cls capacity retention of the battery in Comparative Example 5.

[0173] As can be seen from Table 2, compared with Example 1, the second carbonaceous raw material in Comparative Example 6 has a high aromaticity, which leads to a significant reduction in the first efficiency, lithium plating window and 1000cls capacity retention of the battery in Comparative Example 6.

[0174] As can be seen from Table 2, compared with Example 1, the mass ratio of the first graphite and the second graphite in Comparative Example 7 is too large, which leads to a significant reduction in the compaction density of the negative electrode sheet, the first efficiency of the battery, the lithium plating window, and the 1000cls capacity retention rate of Comparative Example 7.

[0175] As can be seen from Table 2, compared with Example 1, the mass ratio of the first graphite and the second graphite in Comparative Example 8 is too small, which leads to a significant reduction in the specific capacity of the negative electrode material, the compaction density of the negative electrode sheet, the first efficiency of the battery, and the capacity retention rate at 1000cls.

[0176] As can be seen from Table 2, compared with Example 1, in Comparative Example 9, the first carbonaceous material forms secondary particles and the second carbonaceous material forms single particles, which leads to a significant reduction in the specific capacity of the negative electrode material, the compaction density of the negative electrode sheet, the first efficiency of the battery, and the capacity retention rate at 1000cls.

[0177] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0178] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A method for preparing a negative electrode material, characterized in that, include: Select a first carbonaceous raw material and a second carbonaceous raw material, wherein the mass content of sulfur in the first carbonaceous raw material is 0.8%~2.5%, and the mass content of sulfur in the second carbonaceous raw material is 0.1%~0.5%, the aromaticity of the first carbonaceous raw material is 0.68~0.8, and the aromaticity of the second carbonaceous raw material is 0.68~0.8; wherein, aromaticity = A 1630 / (A 1630 +A 1438 +A 1335 A 1630 This indicates the 1630cm in the Fourier transform infrared spectrum. -1 The intensity of the infrared characteristic peak, A 1438 This indicates that 1438 cm⁻¹ in the Fourier transform infrared spectrum -1 The intensity of the infrared characteristic peak, A 1335 This indicates that 1335 cm⁻¹ in the Fourier transform infrared spectrum -1 The intensity of infrared characteristic peaks; The first carbonaceous raw material is crushed to obtain single-particle first carbonaceous powder. The second carbonaceous raw material is crushed and granulated to obtain a second carbonaceous powder with secondary particles. The first carbonaceous powder is pre-carbonized; The first carbonaceous powder after pre-carbonization is graphitized to obtain the first graphite; the second carbonaceous powder is graphitized to obtain the second graphite. The first graphite and the second graphite are mixed to obtain the negative electrode material; The mass ratio of the first graphite to the second graphite is (3:7) to (8:2). No binder is added during the granulation process; The granulation process is carried out at a temperature of 400℃ to 700℃. The first carbonaceous raw material includes at least one of petroleum coke, needle coke, pitch coke, and shot coke; The second carbonaceous raw material includes at least one of petroleum coke, needle coke, pitch coke, and shot coke.

2. The method according to claim 1, characterized in that, The particle size Dv50 of the first carbonaceous powder is 6µm~14µm, and the tap density of the first carbonaceous powder is 0.5g / cm³. 3 ~0.7g / cm 3 ; And / or, the particle size Dv50 of the second carbonaceous powder is 14.5µm~20.5µm, and the tap density of the second carbonaceous powder is 0.5g / cm³. 3 ~0.7g / cm 3 .

3. The method according to any one of claims 1 to 2, characterized in that, The temperature for pre-carbonizing the first carbonaceous powder is 700℃~1500℃, and the time is 2h~9h.

4. The method according to any one of claims 1 to 2, characterized in that, The temperature for graphitizing the pre-carbonized first carbonaceous powder is 2400℃~3200℃; And / or, the temperature for graphitizing the second carbonaceous powder is 2400℃~3200℃.

5. A negative electrode material, characterized in that, It is prepared by the method described in any one of claims 1 to 4.

6. A negative electrode sheet, characterized in that, The negative electrode sheet comprises the negative electrode material prepared by the method described in any one of claims 1 to 4.

7. A battery, characterized in that, Includes the negative electrode sheet as described in claim 6.

8. An energy storage device, characterized in that, Includes the battery as described in claim 7.

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