Artificial graphite negative electrode material for high-capacity lithium ion batteries and method for preparing the same

Abstract

The application belongs to the technical field of graphite negative material preparation, and particularly relates to an artificial graphite negative material for high-capacity lithium ion batteries and a preparation method thereof, which comprises the following steps: raw material pretreatment: petroleum coke or coal-based coke is crushed to obtain particles with a particle size of 5-10 mm, and then the particles are sieved into front-end materials with uniform particle size distribution; graphitization treatment: the front-end materials are heated to 2200-3300 DEG C under an inert atmosphere, and are kept for 6-30 hours for graphitization to obtain graphitized materials; coating material mixing: the graphitized materials are mixed with coating materials at a mass ratio of 98:2-70:30; and the artificial graphite negative material is formed with uniformly distributed and specific proportion macroporous and mesoporous structures on the surface through a specific preparation process. The pore structure constructs rich and smooth transmission channels and storage spaces for lithium ions, and lithium ions can be more quickly embedded and extracted from the negative material during battery charging and discharging, so that the charging and discharging efficiency and rate performance of the battery are effectively improved.

Description

Technical Field

[0001] This invention relates to the field of graphite anode material preparation technology, and in particular to a high-capacity artificial graphite anode material for lithium-ion batteries and its preparation method. Background Technology

[0002] As a key component of lithium-ion batteries, the performance of anode materials directly affects key indicators such as battery capacity, cycle life, and rate performance. Therefore, developing high-capacity, high-performance artificial graphite anode materials for lithium-ion batteries is of great practical significance.

[0003] Currently, the surface pore structure of commonly used artificial graphite anode materials on the market is not ideal, often consisting of irregularly distributed pores with unreasonable pore size ratios. This structure leads to obstructed transport channels for lithium ions during insertion and extraction from the anode material, preventing some lithium ions from reaching their storage locations smoothly, thus limiting the battery's charge / discharge efficiency and rate performance. In scenarios requiring rapid charging and discharging, such as the rapid acceleration of electric vehicles or the fast charging of electronic devices, the battery cannot provide sufficient power, impacting the user experience.

[0004] The fabrication process of some artificial graphite anode materials is relatively simple, lacking precise control over parameters at each stage. For example, inaccurate temperature control during graphitization may lead to insufficient graphitization of petroleum coke or coal-based coke, resulting in poor crystallinity and conductivity of the material. Improper processes during the mixing and carbonization of coating materials can prevent the formation of a uniform amorphous carbon coating layer, affecting the structural and chemical stability of the material. These factors can lead to rapid capacity decay and short cycle life during battery cycling, increasing operating costs.

[0005] Most existing methods for preparing artificial graphite anode materials lack effective means to control the particle size distribution of the material. Different battery design requirements and application scenarios have different needs for the particle size distribution of anode materials, and a fixed particle size distribution is difficult to meet diverse market demands. For example, in some applications with high requirements for battery energy density and volume utilization, anode materials with a more reasonable particle size distribution are needed to optimize the compaction density of battery electrodes, but current technologies struggle to achieve this goal, limiting further improvements in battery performance. Summary of the Invention

[0006] To address the aforementioned problems, this invention proposes a high-capacity artificial graphite anode material for lithium-ion batteries and its preparation method, thereby more accurately solving the problems mentioned in the background section.

[0007] This invention is achieved through the following technical solution: This invention proposes a method for preparing artificial graphite anode material for high-capacity lithium-ion batteries, comprising the following steps: raw material pretreatment: crushing petroleum coke or coal-based coke to obtain particles with a particle size of 5-10 mm, and then sieving to obtain a front-end material with uniform particle size distribution; graphitization treatment: heating the front-end material to 2200-3300℃ under an inert atmosphere and holding for 6-30 hours to obtain graphitized material; coating material mixing: mixing the graphitized material and coating material at a mass ratio of 98:2-70:30, wherein the coating material is at least one of resin or asphalt, and heating the mixture to 400-1000℃ after mixing. Pretreatment at 00℃ for 6-24 hours; Carbonization treatment: The mixture is heated to 600-1500℃ under an inert atmosphere and held for 2-24 hours to form carbonized material with amorphous carbon coating on the surface; Secondary granulation: The carbonized material and asphalt binder are mixed at a mass ratio of 100:5-20 and stirred in a reactor at 200-300℃ for 1-3 hours, then heated to 400-500℃ and stirred to obtain secondary particles with a particle size of 10-20μm; Sieving and demagnetization: The carbonized material or secondary particles are sieved to 270-350 mesh and metal impurities are removed by magnetic separator to obtain the final negative electrode material.

[0008] Preferably, the coating material is at least one of phenolic resin, epoxy resin or petroleum asphalt, and the softening point of the asphalt is 130-160℃.

[0009] Preferably, the inert atmosphere is at least one of nitrogen, argon or helium, and the graphitization process employs a three-stage power curve of "fast-slow-fast" to control the temperature.

[0010] Preferably, in the secondary granulation step, the pressure inside the reactor is 2.5 kg, the stirring speed is 30-300 rpm, and the coking value of the binder asphalt is 10-18%.

[0011] Preferably, the carbonization process further includes a wet coating step: the carbonized material is mixed with a mixed coating agent of coal tar residue oil and graphene slurry at a mass ratio of 100:2-8, wherein the mass percentage of graphene is 0.005-0.64%, the mixing and dispersion speed is 150-200 r / min, and the time is 35-40 minutes.

[0012] Preferably, the carbonization treatment after wet coating is carried out at a temperature of 1050-1250℃ for 4-24 hours under a nitrogen or argon atmosphere.

[0013] A high-capacity artificial graphite anode material for lithium-ion batteries, wherein the interlayer spacing is 0.3382-0.3410 nm, the half-cell specific capacity is 360-365 mAh / g, and the initial efficiency is ≥92%.

[0014] Preferably, the surface has a uniformly distributed macroporous structure, the ratio R of macroporous hole depth H to hole diameter D satisfies 0.5≤R<60, and the ratio r of mesoporous hole depth h to hole diameter d satisfies 0.5≤r<250.

[0015] A lithium-ion battery, wherein the battery electrode compaction density is 1.65-1.75 g / cc and the full charge rebound is less than 12%.

[0016] Preferably, the battery achieves a performance of over 72% at a 2C / 0.2C rate and retains ≥85% of its capacity after 1000 cycles.

[0017] Compared with the prior art, the present invention provides a high-capacity artificial graphite anode material for lithium-ion batteries and its preparation method, which has the following beneficial effects: This high-capacity lithium-ion battery uses artificial graphite anode material and its preparation method. Through a specific preparation process, a uniformly distributed macroporous and mesoporous structure with a specific ratio is formed on the surface of the artificial graphite anode material. This porous structure provides abundant and smooth transport channels and storage space for lithium ions. During battery charging and discharging, lithium ions can be inserted into and extracted from the anode material more quickly, effectively improving the battery's charge and discharge efficiency and rate performance.

[0018] This high-capacity lithium-ion battery uses artificial graphite anode material and its preparation method, employing a multi-stage process including raw material pretreatment, graphitization, coating material mixing, carbonization, and secondary granulation (optional), with precise control of parameters at each stage. For example, the graphitization process uses a three-stage power curve temperature control ("fast-slow-fast"), and the coating material mixing and carbonization process form a uniform amorphous carbon coating layer. The synergistic effect of the multi-stage process ensures that the final artificial graphite anode material possesses high crystallinity, good conductivity, structural stability, and chemical stability.

[0019] This high-capacity lithium-ion battery utilizes artificial graphite anode material and its preparation method. By incorporating an optional secondary granulation step and controlling relevant parameters, secondary particles of a specific size can be produced. This process allows for flexible adjustment of the anode material particle size distribution according to different battery design requirements and application scenarios, optimizing the battery electrode compaction density, further improving battery energy density and volume utilization, while reducing full-charge rebound and enhancing overall battery performance and safety. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of a high-capacity artificial graphite anode material for lithium-ion batteries and its preparation method proposed in this invention. Detailed Implementation

[0021] To more clearly and completely illustrate the technical solution of the present invention, the present invention will be further described below with reference to the accompanying drawings. Example

[0022] like Figure 1 As shown in the figure, an embodiment of the present invention proposes a method for preparing artificial graphite anode material for high-capacity lithium-ion batteries. The specific steps are as follows: Raw material pretreatment: Weigh a certain amount of petroleum coke (or coal-based coke), put it into a crusher for crushing, and obtain particles with a particle size of 5-10 mm after crushing. Then, use a screening device to screen the crushed particles to obtain front-end material with uniform particle size distribution. Graphitization treatment: Place the screened front-end material in a graphitization furnace, and introduce nitrogen (or at least one of argon or helium) into the furnace to create an inert atmosphere. Control the temperature according to the "fast-slow-fast" three-stage power curve, raise the temperature to 2200-3300℃, and keep it at that temperature for 6-30 hours for graphitization treatment. After the treatment, graphitized material is obtained. Coating material mixing: Select phenolic resin (or at least one of epoxy resin or petroleum asphalt) as the coating material, and mix the graphitized material and the coating material at a mass ratio of 98:2-70:30. After mixing, the materials are transferred to a heating device and heated to 400-1000℃ for pretreatment for 6-24 hours. Carbonization: The pretreated mixture is placed in a carbonization furnace, and nitrogen (or at least one of argon or helium) is introduced to create an inert atmosphere. The temperature is raised to 600-1500℃ and held for 2-24 hours to carbonize, forming carbonized material with amorphous carbon coating on the surface. Secondary granulation (optional): A certain amount of carbonized material is weighed, and asphalt with a softening point of 130-160℃ is selected as a binder. The carbonized material and the asphalt binder are mixed at a mass ratio of 100:5-20. The mixture is added to a reactor, the pressure inside the reactor is controlled at 2.5 kg, the stirring speed is 30-300 rpm, and stirring is carried out at 200-300℃ for 1-3 hours. Then, the temperature is raised to 400-500℃ and stirring continues to obtain secondary particles with a particle size of 10-20 μm. Sieving and demagnetization: The carbonized material (if not subjected to secondary granulation) or the secondary particles (if subjected to secondary granulation) is sieved to 270-350 mesh using a sieve, and then the metallic impurities are removed by a magnetic separator to obtain the final artificial graphite anode material. Testing shows that this anode material can be used in the subsequent preparation of lithium-ion batteries.

[0023] In this invention, the coating material is selected from phenolic resin (at least one of epoxy resin or petroleum asphalt may also be selected), and when asphalt is used, the softening point of the asphalt is ensured to be 130-160℃. For example, petroleum asphalt with a softening point of 140℃ is selected as the coating material, and the graphitized material is mixed with the asphalt at a mass ratio of 90:10. Subsequently, the steps of coating material mixing and carbonization treatment in claim 1 are followed, and the final artificial graphite anode material meets the performance requirements of high-capacity lithium-ion batteries.

[0024] In this invention, nitrogen is used as the inert atmosphere (or at least one of argon or helium). During the graphitization stage, a three-stage power curve ("fast-slow-fast") is used to control the temperature: the first stage rapidly heats to 1000℃, the second stage slowly heats to 2500℃, and the third stage rapidly heats to 3000℃, holding at 3000℃ for 15 hours for graphitization. Subsequent operations follow the steps in claim 1, resulting in an artificial graphite anode material with excellent electrochemical performance.

[0025] In this invention, during the secondary granulation step, the carbonized material is mixed with an asphalt binder having a coking value of 10-18% at a mass ratio of 100:15. The mixture is added to a reactor, the pressure inside the reactor is controlled at 2.5 kg, the stirring speed is 150 rpm, and the mixture is stirred at 250°C for 2 hours. Subsequently, the temperature is raised to 450°C and stirring continues to yield secondary particles with a particle size of 15 μm. Subsequent operations are performed according to the sieving and demagnetization steps in claim 1, resulting in a final artificial graphite anode material with a stable structure and excellent performance.

[0026] In this invention, a wet coating step is added after carbonization: a certain amount of carbonized material is weighed, and a mixed coating agent is prepared, wherein coal tar residue oil and graphene slurry are mixed in a certain proportion, and the mass percentage of graphene in the mixed coating agent is 0.005-0.64%. The carbonized material and the mixed coating agent are mixed at a mass ratio of 100:5 and placed in a dispersion device, with the mixing and dispersion speed set at 180 r / min and the dispersion time at 38 minutes. Subsequent steps such as secondary granulation can be selected according to requirements. The surface properties of the final artificial graphite anode material are improved, which is beneficial to improving battery performance.

[0027] In this invention, the carbonization treatment after wet coating is set at 1150℃ for 12 hours, and carried out under a nitrogen (or argon) atmosphere. The wet-coated material is placed in a carbonization furnace, nitrogen is introduced to create the atmosphere, and carbonization is performed according to the set temperature and time. The resulting artificial graphite anode material has higher specific capacity and better cycle stability.

[0028] A high-capacity artificial graphite anode material for lithium-ion batteries was disclosed. Performance testing was performed on this anode material. X-ray diffraction was used to determine its interlayer spacing, showing a spacing of 0.3382–0.3410 nm. A half-cell test was used to determine its specific capacity, showing a half-cell specific capacity of 360–365 mAh / g. The initial efficiency was tested, showing an initial efficiency ≥92%. This anode material meets the requirements for use in high-capacity lithium-ion batteries.

[0029] In this invention, the surface structure of the negative electrode material was examined using scanning electron microscopy and mercury porosimetry. The results showed that its surface has a uniformly distributed macroporous structure, with the ratio R of macropore depth H to pore diameter D satisfying 0.5 ≤ R < 60, and the ratio r of mesopore depth h to pore diameter d satisfying 0.5 ≤ r < 250. This unique pore structure is beneficial for lithium-ion transport and storage, thus improving battery performance. In this invention, the compaction density of the battery electrodes is controlled to be 1.65-1.75 g / cc during battery fabrication. Performance tests were conducted on the prepared batteries, and their full-charge rebound was detected using a charge-discharge tester. The results showed that the full-charge rebound was less than 12%. This lithium-ion battery exhibits good charge-discharge performance and structural stability.

[0030] In this invention, the rate performance and cycle performance of the lithium-ion battery are tested. Using a charge-discharge tester, the battery is charged and discharged at a rate of 2C / 0.2C, and the results show that the battery performance reaches over 72%. The battery is then subjected to a cycle test, and its capacity retention is measured after 1000 cycles, showing a capacity retention of ≥85%. This lithium-ion battery exhibits excellent high-rate charge-discharge performance and a long cycle life.

[0031] Finally, it should be noted that the basic concepts have been described above. Obviously, for those skilled in the art, the detailed disclosure above is merely illustrative and does not constitute a limitation of this specification. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements, and corrections to this specification. Such modifications, improvements, and corrections are suggested in this specification, and therefore remain within the spirit and scope of the exemplary embodiments of this specification. Furthermore, this specification uses specific terms to describe embodiments of this specification. For example, "an embodiment," "one embodiment," and / or "some embodiments" refer to a feature, structure, or characteristic associated with at least one embodiment of this specification. Therefore, it should be emphasized and noted that "an embodiment," "one embodiment," or "an alternative embodiment" mentioned twice or more in different locations in this specification do not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of this specification can be appropriately combined. Moreover, unless expressly stated in the claims, the order of processing elements and sequences, the use of numbers and letters, or other names described in this specification are not intended to limit the order of the processes and methods of this specification.

[0032] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a high-capacity lithium-ion battery artificial graphite anode material, characterized in that, Includes the following steps: Raw material pretreatment: Petroleum coke or coal-based coke is crushed to obtain particles with a particle size of 5-10mm, and then screened into front-end materials with uniform particle size distribution. Graphitization treatment: The front-end material is heated to 2200-3300℃ in an inert atmosphere and held for 6-30 hours to obtain graphitized material; Coating material mixing: Mix the graphitized material and the coating material at a mass ratio of 98:2-70:

30. The coating material is at least one of resin or asphalt. After mixing, heat to 400-1000℃ for pretreatment for 6-24 hours. Carbonization treatment: The mixture is heated to 600-1500℃ under an inert atmosphere and held for 2-24 hours to form carbonized material with amorphous carbon on the surface. Secondary granulation: The carbonized material and the asphalt binder are mixed at a mass ratio of 100:5-20 and stirred in a reactor at 200-300℃ for 1-3 hours. Then the temperature is raised to 400-500℃ and stirred to obtain secondary particles with a particle size of 10-20μm. Screening and demagnetization: The carbonized material or secondary particles are screened to 270-350 mesh and metal impurities are removed by magnetic separator to obtain the final negative electrode material.

2. The preparation method according to claim 1, characterized in that, The coating material is at least one of phenolic resin, epoxy resin or petroleum asphalt, and the softening point of the asphalt is 130-160℃.

3. The preparation method according to claim 1, characterized in that, The inert atmosphere is at least one of nitrogen, argon or helium, and the temperature is controlled by a three-stage power curve of "fast-slow-fast" during the graphitization process.

4. The preparation method according to claim 1, characterized in that, In the secondary granulation step, the pressure inside the reactor is 2.5 kg, the stirring speed is 30-300 rpm, and the coking value of the binder asphalt is 10-18%.

5. The preparation method according to claim 1, characterized in that, The carbonization process further includes a wet coating step: the carbonized material is mixed with a mixed coating agent of coal tar residue oil and graphene slurry at a mass ratio of 100:2-8, wherein the mass percentage of graphene is 0.005-0.64%, the mixing and dispersion speed is 150-200 r / min, and the time is 35-40 minutes.

6. The preparation method according to claim 5, characterized in that, The carbonization process following wet coating is carried out at a temperature of 1050-1250℃ for 4-24 hours under a nitrogen or argon atmosphere.

7. A high-capacity artificial graphite anode material for lithium-ion batteries, characterized in that, The cell is prepared by any one of claims 1-6, wherein the interlayer spacing is 0.3382-0.3410 nm, the half-cell specific capacity is 360-365 mAh / g, and the initial efficiency is ≥92%.

8. The artificial graphite anode material according to claim 7, characterized in that, The surface has a uniformly distributed macroporous structure, the ratio R of macroporous hole depth H to hole diameter D satisfies 0.5≤R<60, and the ratio r of mesoporous hole depth h to hole diameter d satisfies 0.5≤r<250.

9. A lithium-ion battery, characterized in that, The negative electrode material is the high-capacity artificial graphite negative electrode material as described in claim 7 or 8, and the battery electrode compaction density is 1.65-1.75 g / cc, with a full-charge rebound of less than 12%.

10. The lithium-ion battery according to claim 9, characterized in that, The battery achieves over 72% performance at 2C / 0.2C rates and retains ≥85% capacity after 1000 cycles.

Images