Spherical carbon material, preparation process thereof, negative electrode material and lithium battery

Abstract

The application relates to the technical field of lithium batteries, in particular to a spherical carbon material, a preparation process thereof, a negative electrode material and a lithium battery. The preparation process comprises the following steps: performing at least one time of grading crushing on a carbon material crude product to obtain grading crushed material; performing cyclic crushing on the grading crushed material to obtain cyclic crushed material; mixing the cyclic crushed material with at least one group of back-doping material to obtain mixed material, and shaping to obtain a spherical carbon material; meanwhile, collecting small particle carbon material generated during the grading crushing and / or the cyclic crushing at least once to obtain collection material, and the back-doping material comprises the collection material; wherein the D50 of at least one group of back-doping material is different from the D50 of the cyclic crushed material, and the absolute value of the difference between the D50 of the mixed material and the D50 of the cyclic crushed material is 0-3 mu m. The process aims to improve the problems of low yield of the spherical carbon material, in particular, low yield of the spherical graphite, low utilization rate of raw materials, more equipment required in the whole production process, more resources occupied, and large energy consumption during production.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, and more specifically, to spherical carbon materials and their preparation processes, negative electrode materials, and lithium batteries. Background Technology

[0002] Lithium-ion batteries are highly sought after by new energy companies due to their advantages such as high operating voltage, high energy density, long cycle life, low self-discharge, and no memory effect. Graphite materials still dominate the market as anode materials in commercial lithium-ion batteries. Natural graphite, with its high charge / discharge capacity, high charge / discharge platform, wide availability, and low cost, is widely used due to these advantages. However, its two fatal drawbacks are large initial irreversible capacity loss and rapid capacity decay during cycling. Therefore, surface modification of natural graphite materials is necessary to improve its electrochemical performance. The general method for modifying graphite is to first crush and grade natural flake graphite into spherical particles to increase tap density. For example, patent CN101850965A describes processing natural flake graphite using five series-connected airflow mills and fourteen series-connected spheroidizing mills to produce spherical graphite, demonstrating that natural graphite requires multiple crushing and shaping processes to produce spherical graphite. However, during these processes, natural flake black undergoes tens of thousands of collisions and cutting frictions, resulting in a large number of fine particles inside the powder. These fine particles are mostly nano- and sub-nano-sized, with a wide range of powder particle sizes and an increased specific surface area. In addition, large aspect ratio plate-shaped particles or rod-shaped irregular particles are also produced, leading to an increase in the initial irreversible capacity and internal resistance. Furthermore, the shaping time and number of shaping cycles increase, resulting in a decrease in product yield, an increase in power consumption, and a significant increase in production costs.

[0003] In view of this, the present invention is proposed. Summary of the Invention

[0004] The purpose of this invention is to provide spherical carbon materials, their preparation process, anode materials, and lithium batteries. The preparation process for these spherical carbon materials aims to improve the problems of low yield, low raw material utilization, large equipment requirements, high resource consumption, and high energy consumption associated with spherical carbon materials, particularly spherical graphite.

[0005] This invention is implemented as follows:

[0006] In a first aspect, the present invention provides a process for preparing spherical carbon materials, comprising:

[0007] The crude carbon material is subjected to at least one stage of pulverization to obtain the pulverized material.

[0008] The graded pulverized material is then subjected to cyclic pulverization to obtain cyclic pulverized material;

[0009] The recycled pulverized material is mixed with at least one set of recycled materials to obtain a mixture, which is then shaped to obtain the spherical carbon material.

[0010] Simultaneously, the small carbon particles generated during the graded crushing and / or cyclic crushing are collected at least once to obtain the collected material, and the recycled material includes the collected material;

[0011] Among them, at least one set of the recycled admixtures has a D 50 With the D of the recycled pulverized material 50 Different, and the D of the mixture 50 With the D of the recycled pulverized material 50 The absolute value of the difference is 0-3 μm.

[0012] In an optional embodiment, the preparation process satisfies at least one of the following features (1) to (4):

[0013] (1) The particle size distribution width deviation coefficient σ of the circulating crushed material is ≤7;

[0014] (2) The raw materials for the carbon material include natural graphite;

[0015] (3) The raw material of the carbon material includes natural graphite, and the carbon content of the natural graphite is more than 94%;

[0016] (4) The raw materials of the carbon material include natural graphite, which includes flake graphite and microcrystalline graphite.

[0017] In an optional embodiment, the preparation process satisfies at least one of the following features (1) to (3):

[0018] (1) The median particle size of the crude carbon material is 20-70 μm;

[0019] (2) The median particle size of the graded pulverized material is 10-40 μm;

[0020] (3) The time for each crushing and grading is less than 2 hours.

[0021] In an optional implementation, each time the collection is completed, a set of collected material is obtained, and the D of each set of collected material is... 50 Not exactly the same.

[0022] In an optional embodiment, the preparation process satisfies at least one of the following features (1) to (7):

[0023] (1) The D of the circulating crushed material 50 It is 7-30μm;

[0024] (2) The sphericity of the recycled crushed material is greater than 0.7;

[0025] (3) The D of the recycled material 50 10-35μm;

[0026] (4) The shaping time is 20-30 minutes;

[0027] (5) The D of the collected material 50 10-35μm;

[0028] (6) The collected materials are in two or more groups, and there is a distance D between each group of collected materials. 50 The absolute value of the difference is less than 7 μm;

[0029] (7) The circulating crushed material D 50 With the re-admixture D 50 The absolute value of the difference is less than 6 μm.

[0030] Secondly, the present invention provides a spherical carbon material, which is prepared by the spherical carbon material preparation process described in any of the foregoing embodiments.

[0031] In an optional embodiment, the spherical carbon material is spherical graphite.

[0032] In an optional embodiment, the spherical carbon material satisfies at least one of the following characteristics (1) to (3):

[0033] (1)D 50 The thickness is 8-30 μm;

[0034] (2) Tap density ≥ 0.9 g / cm³ 2 ;

[0035] (3) Sphericity greater than 0.9.

[0036] Thirdly, the present invention provides a negative electrode material comprising a matrix and a spherical carbon material as described in any of the foregoing embodiments, wherein the spherical carbon material is coated on the surface of the matrix.

[0037] Fourthly, the present invention provides a lithium battery comprising the negative electrode material described in the foregoing embodiments.

[0038] The present invention has the following beneficial effects: By grading and crushing, circulating crushing, and shaping all the materials formed by grading and circulating crushing, the present invention maximizes the utilization rate of materials, significantly improves the yield compared with the original process system, reduces the number of equipment used, reduces the energy consumption required during trial production, and significantly increases the overall production capacity. This process improvement can bring huge profits to the production of spherical graphite. Attached Figure Description

[0039] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 The images shown are electron microscope images of the materials provided in Embodiment 2 of the present invention. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0042] This invention provides a process for preparing spherical carbon materials, as detailed below:

[0043] First, the raw materials for carbon materials are coarsely pulverized to form crude carbon materials. These raw materials include natural graphite with a carbon content of 94% or higher; for example, 95%, 96%, 97%, 98%, and 99%, etc., with a content of 94% or higher, including flake graphite and microcrystalline graphite. It should be noted that existing technologies can also modify carbon materials used to prepare anode materials.

[0044] After coarse grinding, the particle size of the carbon material raw materials is reduced, transforming the raw materials from lumps into powder, resulting in a crude carbon material with a density of D. 50The range is 20-70 μm, for example, it can be 10-12 μm, 13-15 μm, 16-18 μm, 19-21 μm, 22-24 μm, 25-27 μm, 10-15 μm, 16-20 μm, 10-13 μm, 10-14 μm, 10-16 μm, 10-17 μm, 10-18 μm, 10-19 μm, 10-20 μm, 10-21 μm, 10-22 μm, 10-23 μm, 10-2 4μm, 10-25μm, 10-26μm, 10-27μm, 10-28μm, 10-29μm, 11-15μm, 11-18μm, 11-19μm, 20-30μm, 20-22 μm, 23-25μm, 26-28μm, 29-30μm, 20-23μm, 24-27μm, 20-24μm, 25-28μm, 28-30μm, 20-25μm, 26-30μm m, 20-26μm, 27-30μm, 20-27μm, 20-28μm, 20-29μm, 30-32μm, 33-35μm, 36-38μm, 39-40μm, 31-33μm , 35-37μm, 38-40μm, 30-33μm, 34-36μm, 37-40μm, 34-37μm, 30-34μm, 35-39μm, 30-35μm, 36-40μm, The crude carbon material is automatically transported to the next stage. The range of values ​​formed by any two values ​​between 20-70 μm is defined as follows: 30-36 μm, 30-37 μm, 30-38 μm, 30-39 μm, 20-30 μm, 30-40 μm, 40-50 μm, 50-60 μm, 60-70 μm, 35-55 μm, 35-65 μm, 45-65 μm, 35-50 μm, 40-70 μm, 66-70 μm, 65-70 μm.

[0045] It should be noted that the crushing equipment used for coarse crushing includes, but is not limited to, mechanical roller mills, mechanical mills, air-pulverizers, and crushers.

[0046] The coarse carbon material obtained from the above coarse crushing is subjected to at least one stage of classification crushing. The number of stages of crushing can be 1, 2, 3, or 4 times, etc. The time for each stage of crushing and classification is less than 2 hours. Each stage of crushing yields two types of materials: one is small carbon particles that can be directly re-blended and shaped, which are directly stored in a storage tank; the other is relatively larger particles, which are then subjected to another stage of classification crushing until the relatively larger particles meet the requirements for cyclic crushing, thus forming the classified crushed material.

[0047] The median particle size of the graded pulverized material is 10-40 μm, preferably 10-25 μm or 20-30 μm. For example, it can be 10-12μm, 13-15μm, 16-18μm, 19-21μm, 22-24μm, 25-27μm, 10-15μm, 16-20μm, 10-13μm, 10-14μm, 10-16μm, 10-17μm, 10-18μm, 10-19μm, 10-20μm, 10-21μm, 10-22μm, 10-23μm, 10-24μm, 10-25μm, 10-26μm, 10-27μm, 10-28μm, 10-29μm, 11-15μm, 11-18μm, 11-19μm, 20-30μm The range of values ​​formed by any two values ​​between 10 and 40 μm, or any value between 10 and 40 μm, is defined as m, 20-22 μm, 23-25 ​​μm, 26-28 μm, 29-30 μm, 20-23 μm, 24-27 μm, 20-24 μm, 25-28 μm, 28-30 μm, 20-25 μm, 26-30 μm, 20-26 μm, 27-30 μm, 20-27 μm, 20-28 μm, 20-29 μm, 10-30 μm, 10-35 μm, 15-35 μm, 25-35 μm, 38-40 μm, 35-40 μm, 31-μm, 30-40 μm, etc.

[0048] D of small carbon material obtained by graded crushing 50 The range is 10-35 μm, for example, it can be 10-12 μm, 13-15 μm, 16-18 μm, 19-21 μm, 22-24 μm, 25-27 μm, 10-15 μm, 16-20 μm, 10-13 μm, 10-14 μm, 10-16 μm, 10-17 μm, 10-18 μm, 10-19 μm, 10-20 μm, 10-21 μm, 10-22 μm, 10-23 μm, 10-24 μm, 10-25 μm, 10-26 μm, 10-27 μm, 10-28 μm, 10-29 μm, 11-15 μm, 11- The range of values ​​formed by any two values ​​between 10-35μm, including 18μm, 11-19μm, 20-30μm, 20-22μm, 23-25μm, 26-28μm, 29-30μm, 20-23μm, 24-27μm, 20-24μm, 25-28μm, 28-30μm, 20-25μm, 26-30μm, 20-26μm, 27-30μm, 20-27μm, 20-28μm, 20-29μm, 10-30μm, 10-35μm, 15-35μm, and 25-35μm.

[0049] The present invention illustrates the process of graded pulverization using the following example: for instance, the crude carbon material is subjected to a first graded pulverization to obtain D. 50 The material consists of small carbon particles of 10-35 μm (which are directly collected and stored) and a first large particle. The first large particle is then subjected to a second classification and pulverization to obtain D. 50 The small carbon particles of 10-35 μm (which can be collected and stored directly, or stored together with the small carbon particles obtained from the first fractionation and pulverization) and D 50 The graded and pulverized material has a particle size of 10-40 μm. At this point, the coarse graphite has undergone two stages of grading and pulverization.

[0050] For example, the crude graphite is first graded and pulverized to obtain D. 50 The small carbon particles (10-35 μm in size) and the first large particle are subjected to a second classification and pulverization to obtain D. 50 The first part consists of small carbon particles of 10-35 μm (which can be directly collected and stored together with the small carbon particles obtained from the first classification and pulverization) and a second large particle. The second large particle is then subjected to a third classification and pulverization to obtain D. 50 The small particulate material of 10-35 μm (which can be directly collected and stored together with the small particulate carbon material obtained from the first and second classification crushing) and D 50 The graded and pulverized material has a particle size of 10-40 μm; at this point, the coarse graphite has undergone three stages of grading and pulverization. The equipment for performing the grading and pulverization can be multiple pulverizers connected in parallel.

[0051] The aforementioned graded crushing method ensures that large particles are continuously crushed within the system, maximizing their utilization. Compared to existing market processes, this significantly improves material utilization and makes it easier to adjust the particle size.

[0052] The above-mentioned graded crushed material is circulated and crushed. The circulated crushing process will continuously crush and grind some of the more difficult-to-crush and larger particles through the main machine. The material that meets the standard (i.e., the small carbon particles produced during the circulated crushing) is transported to the dust collector for collection. The slightly coarser particles are returned to the main machine for further crushing until the circulated crushed material that meets the requirements is obtained.

[0053] Among them, the D of the recycled crushed material 50The value can be 7-30μm, for example, it can be any two values ​​between 7-30μm such as 7-10μm, 11-14μm, 15-18μm, 19-21μm, 22-25μm, 26-29μm, 7-9μm, 10-12μm, 13-15μm, 16-18μm, 19-22μm, 23-25μm, 26-28μm, 7-15μm, 7-20μm, 10-15μm, 15-25μm, 10-20μm, 20-30μm, 27-30μm, 28-30μm, 25-30μm, 21-30μm, etc., forming a range of values ​​or any value between 7-30μm.

[0054] D of small carbon material obtained by cyclic pulverization 50 The range is 10-35 μm, for example, it can be 10-12 μm, 13-15 μm, 16-18 μm, 19-21 μm, 22-24 μm, 25-27 μm, 10-15 μm, 16-20 μm, 10-13 μm, 10-14 μm, 10-16 μm, 10-17 μm, 10-18 μm, 10-19 μm, 10-20 μm, 10-21 μm, 10-22 μm, 10-23 μm, 10-24 μm, 10-25 μm, 10-26 μm, 10-27 μm, 10-28 μm, 10-29 μm, 11-15 μm, 11- The range of values ​​formed by any two values ​​between 10-35μm, including 18μm, 11-19μm, 20-30μm, 20-22μm, 23-25μm, 26-28μm, 29-30μm, 20-23μm, 24-27μm, 20-24μm, 25-28μm, 28-30μm, 20-25μm, 26-30μm, 20-26μm, 27-30μm, 20-27μm, 20-28μm, 20-29μm, 10-30μm, 10-35μm, 15-35μm, and 25-35μm.

[0055] Furthermore, the small particles formed by the cyclic crushing can be collected individually or together with the small particles formed by the graded crushing. Each completion of the collection yields a set of collected material, and the D of each set of collected material... 50 Not entirely the same. When the collected material consists of two or more groups, the distance between each group of collected material is D. 50 The absolute value of the difference is less than 7 μm.

[0056] The preparation process provided in this invention can maintain a relatively constant material concentration during cyclic pulverization. Compared with traditional pulverization, the small carbon particles produced after grinding of the graded pulverized material will not remain in the equipment for further pulverization, thus preventing the generation of many uneven and irregular particles. This controls the generation of fine powder during the pulverization process from the source. This also reduces the proportion of fine powder extracted during the subsequent shaping process compared with traditional processes, thereby greatly improving the yield, which can be increased from the current market maximum single product yield of 50%-60% to over 75%.

[0057] Meanwhile, the particle size of the material continuously narrows during the recycling process. This is mainly because, in the later stage of the recycling and crushing process of this invention embodiment, the average particle size is basically on the same order of magnitude as that of the traditional process, which is more conducive to the re-mixing of fine powder.

[0058] Specifically, the particle size distribution width deviation coefficient σ of the recycled crushed material is ≤7. The particle size distribution width deviation coefficient is calculated as follows: Draw a vertical dividing line on the particle size chart, ensuring that the vertical line divides the area enclosed by the particle size curve and the horizontal axis into two equal parts. Take the value at the intersection of the vertical line and the horizontal axis. Repeat this method for each particle size curve to be tested to obtain the median particle size of each curve. Perform this selection three times and calculate the median particle size using the standard deviation of the distribution frequency curve.

[0059]

[0060] Where Dnl is the average particle size, and di is the particle size of each particle (take D as D). 50 (Number).

[0061] For example, with a particle size of 10-15, taking the median of 12.5, the frequency distribution of the material after three cycles of pulverization using the new process and the corresponding three frequency distributions at the end of the pulverization stage of the traditional process were calculated. The standard deviation of the frequency distribution curve was used for the calculation. The results are as follows: for the preparation process provided in this embodiment, σχ1≈5.63, σχ2≈5.45, σχ3≈5.24 (σ≤7); for the traditional process, σс1≈7.45, σс2≈8.01, σс3≈7.92. Therefore, the standard deviation of the preparation process provided in this embodiment is significantly smaller than that of the traditional process. This leads to the conclusion that the material obtained after cyclic pulverization using the new process has a narrower particle size than that obtained using the traditional process, laying a foundation for the next step of mixing the materials. The traditional process refers to continuous pulverization without recycling the fine powder.

[0062] Meanwhile, after a period of time, the graded and pulverized material undergoes grinding within the pulverizing host, resulting in a certain degree of increased compaction (≥0.9). Small carbon particles generated during the circulating pulverization process are collected to ensure they are not wasted. After the required circulating pulverization time is reached, the final circulating pulverized material is released and mixed with the previously collected material. The D of the collected material... 50 The particle size is relatively wide, and when mixed with the circulating pulverized material, it achieves the particle size compaction index required for pulverization. Compared with traditional pulverization processes, this circulating pulverization process can control the particle size of the circulating pulverized material through pulverization time. At the same time, after multiple grinding processes, the circulating pulverized material will have a certain degree of sphericity, which is greater than 0.7.

[0063] In traditional processes, qualified particles are separated from the tailings after each crushing, resulting in a yield of less than 70%. However, the process provided in this invention eliminates the loss of large particles during the crushing process. In the subsequent shaping process, all qualified particles participate in the shaping, achieving a yield of 100%. This step also has a certain shaping effect.

[0064] It should be noted that the equipment for achieving circulating pulverization includes, but is not limited to, a series of devices with pulverizing functions such as air jet mills, mechanical mills, and air jet pulverizers, which classify materials and return them to the main unit. This equipment mainly consists of a pulverizing main unit, an internal classifier, an external classifier, and a bag filter. The internal classifier connects to the external classifier, the upper part of the external classifier connects to the bag filter, and the lower connecting pipe directly connects back to the main unit's processing chamber. During the circulating pulverization process, some materials that are difficult to pulverize and have larger particles are continuously pulverized and ground by the main unit. Materials that meet the standards are directly conveyed to the dust collector at the top of the external classifier for collection, while slightly coarser particles are returned to the main unit for further pulverization.

[0065] The number of cyclic pulverization cycles is 1, 2, 3, and 4, etc. For example, the graded pulverized material is passed through a deep pulverizer to form the small carbon particles and the first coarse particles. The first coarse particles are then further pulverized to form the small carbon particles and the cyclic pulverized material. The average particle size of the small carbon particles and the cyclic pulverized material is basically on the same order of magnitude. In this case, 2 cycles of pulverization have been performed.

[0066] Large, difficult-to-crush particles are circulated and crushed. This process allows for time-controlled particle size reduction and a certain shaping effect, laying a good foundation for subsequent shaping processes. The average particle size of the particles obtained from the circulated crushing is monitored online, which in turn determines the circulated crushing time.

[0067] This invention, through a combination of graded crushing and recirculating crushing, effectively utilizes coarse particles from a single batch, achieving a significant increase in yield. 50For spherical graphite with a diameter of 8-30 μm, the yield of a single product can be increased from 30%-50% to over 75%. Secondly, it reduces the generation of tailings, promptly recovers fine powder, and avoids excessive grinding during continuous crushing in the equipment, thus improving the utilization rate of fine powder. Simultaneously, the tailings from the shaping process can be recycled for the production of D... 50 The utilization rate of small-particle-size graphite products (3-12μm) can be further increased by 20%, and the raw material utilization rate of the entire process can reach over 95%. Energy consumption is effectively matched to the coarse powder crushing process, maximizing crushing efficiency without over-grinding. Particle size control is simplified. Furthermore, unlike the previous staged crushing, the material in the circulating crushing process is enclosed within the equipment throughout the entire crushing process, and the material size does not decrease with increasing crushing passes. During the circulating crushing process, the material achieves a certain degree of sphericity through multiple grinding processes, and the compaction is improved, providing a foundation for subsequent shaping processes.

[0068] The recycled pulverized material is mixed with at least one set of recycled materials to obtain a mixture, wherein the recycled materials include the collected material; the D of the recycled materials 50 The range is 10-35 μm, for example, it can be 10-12 μm, 13-15 μm, 16-18 μm, 19-21 μm, 22-24 μm, 25-27 μm, 10-15 μm, 16-20 μm, 10-13 μm, 10-14 μm, 10-16 μm, 10-17 μm, 10-18 μm, 10-19 μm, 10-20 μm, 10-21 μm, 10-22 μm, 10-23 μm, 10-24 μm, 10-25 μm, 10-26 μm, 10-27 μm, 10-28 μm, 10-29 μm, 11-15 μm, 11- The range of values ​​formed by any two values ​​between 10-35μm, including 18μm, 11-19μm, 20-30μm, 20-22μm, 23-25μm, 26-28μm, 29-30μm, 20-23μm, 24-27μm, 20-24μm, 25-28μm, 28-30μm, 20-25μm, 26-30μm, 20-26μm, 27-30μm, 20-27μm, 20-28μm, 20-29μm, 10-30μm, 10-35μm, 15-35μm, and 25-35μm.

[0069] At least one set of said recycled materials D 50 With the D of the recycled pulverized material 50 Different, recycled crushed material D 50 With the re-admixture D 50 The absolute value of the difference is less than 6 μm, and the D of the mixture 50 With the D of the recycled pulverized material 50The absolute value of the difference is 0-3 μm.

[0070] The above mixing method is airflow mixing. Airflow mixing does not reduce the particle size of the material during the mixing process, eliminates external factors in the material mixing process, and the particle size and compaction of the mixed material will meet the shaping requirements.

[0071] After mixing, the mixture is shaped for 20-30 minutes, such as any value between 20 minutes, 22 minutes, 23 minutes, 24 minutes, 25 minutes, 26 minutes, 27 minutes, 28 minutes, 29 minutes, and 30 minutes.

[0072] Specifically, the particles are sphericalized through mutual collision and shearing between materials. Since the large-particle graded and crushed material has already achieved a certain degree of sphericity after cyclic crushing, the morphology of the small carbon particles generated during grading and cyclic crushing is relatively easy to change, greatly improving the overall efficiency of the shaping process. After 20-30 minutes of shaping, the material passes the test and reaches within the control limits. 50 The final spherical carbon material D has a diameter of 8-30 μm. 50 The particle size is 8-30μm. Furthermore, due to the reduced generation of fine powder during the initial cyclic pulverization process, the impact of fine powder on the material is minimized during the subsequent shaping process. The shaping process reduces surface defects in the particles to a minimum, resulting in a lower Raman value, decreasing from around 0.5 in traditional processes to around 0.4. The material also exhibits better sphericity, more uniform particle size, and a tap density ≥0.9g / cm³. 2 .

[0073] This invention provides a spherical carbon material, which is prepared by the above-described preparation process. The spherical carbon material is spherical graphite. The spherical carbon material satisfies at least one of the following characteristics (1) to (3): (1) D 50 It is 8-30μm; for example, it is any range of values ​​formed by any two values ​​between 8-30μm, such as 8-10μm, 11-13μm, 14-16μm, 17-19μm, 20-22μm, 23-25μm, 26-28μm, 8-11μm, 12-15μm, 16-19μm, 20-23μm, 24-26μm, 27-30μm, 11-15μm, 16-20μm, 21-25μm, 26-30μm, 10-20μm, 8-15μm, 15-30μm, 20-30μm, 27-30μm, 24-30μm, etc.

[0074] (2) Tap density ≥ 0.9 g / cm³ 2 ;

[0075] (3) Sphericity greater than 0.9.

[0076] The production capacity of the preparation process provided in this invention is calculated to be more than twice that of the original, which can largely solve the problem of low raw material utilization. The assembled production line operates almost fully automatically, saving a significant amount of manpower and resources. It effectively utilizes the large particles produced during the crushing process, maximizing material utilization through continuous grading and final recycling of these large particles. The yield is significantly higher than the original process system, while reducing the number of equipment units used and the energy consumption required during trial production, resulting in a substantial increase in overall production capacity. This process improvement can bring huge profits to the production of spherical graphite.

[0077] This embodiment also provides a negative electrode material, which includes a matrix and the above-mentioned spherical carbon material, wherein the spherical carbon material is coated on the surface of the matrix.

[0078] This embodiment also provides a lithium battery, which includes the above-mentioned negative electrode material.

[0079] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0080] Example 1

[0081] This embodiment provides a process for preparing spherical graphite, including:

[0082] Natural graphite raw materials are selected and fed into a coarse crushing device for coarse crushing. After coarse crushing, the particle size of the natural graphite raw materials is reduced, and the raw materials are broken down from lumps into powdery coarse graphite product. 50 With a particle size of 32.1 μm, the crude graphite is automatically transported to the next stage.

[0083] After coarse crushing, the natural graphite raw material is transported via automated pipeline to the second stage, a parallel stage consisting of two first-stage crushers, where the coarse graphite undergoes its first stage of grading. The resulting particles, D, meet the requirements for the final crushing result. 50 The particle size is 23.5 μm, and it enters the storage device for storage. The relatively larger particles formed after the first classification and crushing are transported through pipelines to the next stage for a second classification and crushing. The smaller particles after the second classification and crushing enter the storage device through transport pipelines, and the relatively larger particles also enter the next stage for a third classification and crushing, and so on, with the particle size D of the fine powder being the same each time. 50 After multiple crushing and grading processes at a density of 15±6, the relatively large particles were reduced to D size. 50 The particles are 18.806 μm in size, and all of them are collected into the storage device for unified storage.

[0084] The large particles obtained from the final stage of grading and crushing, namely the graded and crushed material, enter the third stage for circulating crushing. The large particles are fed into the circulating crushing device. During this process, some materials that are difficult to crush and have large particle sizes are continuously crushed by the main unit, resulting in a continuous reduction in particle size and a certain degree of improvement in compaction. This ensures that fine powder is not wasted. During the setup phase, it is only necessary to circulate the material to stage D. 50 The required standard time (15 μm in this example) is recorded. After the required time for cyclic pulverization is reached, the final coarse particles are released into the mixing device.

[0085] Fine powder and small particles stored in the storage device are added to the mixing device after the large particles have been processed. In the mixing device, coarse particles (i.e., recycled crushed material), fine powder, and small particles are thoroughly mixed. The particle size and compaction of the mixed material will meet the shaping requirements. The D of the mixed material... 50 The particle size was 14.921 μm, and after cyclic pulverization, coarse particles were collected as D. 50 The particle size is 15.643 μm, the sphericity is 0.79, and the fine powder collected during cyclic pulverization has a D value. 50 The value is 13.501 μm, and the following relationships must be satisfied: For finely ground powder D... 50 =Circular crushing of coarse particles D 50 ±7, circulating pulverization of fine powder D 50 =Circulating crushed coarse particles ±6. In this embodiment, the standard for fine powder to be re-mixed is that the standard deviation of the distribution frequency curve of the material after circulating crushing is σx1≈5.05, σx2≈5.11, σx3≈4.99, all <7. The material after re-mixing must meet the following: Circulating crushed coarse particles = Crushed mixture ±3 (-3 < 14.921 - 15.643 = -0.722 < 3). The mixture is transported to the shaping machine, where the particles tend to be spherical through mutual collision and shearing between the materials. Since the large particles of the material have already achieved a certain degree of sphericity after circulating crushing, the morphology of the small particles is relatively easy to change, and the overall efficiency of the shaping process is greatly improved. After 20-25 minutes of shaping, the material passes the test and reaches the control value. D 50 The thickness is 14.397 μm. The single-product yield of the shaping equipment is 82%, and the tap density is 0.952 g / cm³. 2 , sphericity 0.91.

[0086] Example 2

[0087] This embodiment provides a process for preparing spherical graphite, including:

[0088] Natural graphite raw materials are selected and fed into a coarse crushing device for coarse crushing. After coarse crushing, the particle size of the natural graphite raw materials is reduced, and the raw materials are broken down from lumps into powdery coarse graphite product. 50The graphite crude material, with a diameter of 35.587 μm, is automatically transported to the next stage.

[0089] After coarse crushing, the natural graphite raw material is transported via automated pipeline to the second stage, a parallel stage consisting of two first-stage crushers, where the coarse graphite undergoes its first stage of grading. The resulting particles, D, meet the requirements for the final crushing result. 50 The particle size is 21.854 μm, and it enters the storage device for storage. The relatively larger particles formed after the first classification and crushing are transported through pipelines to the next stage for a second classification and crushing. The smaller particles after the second classification and crushing enter the storage device through transport pipelines, and the relatively larger particles also enter the next stage for a third classification and crushing, and so on. The particle size D of the fine powder is 21.854 μm each time. 50 After multiple crushing and grading processes at a temperature of 20±6, the relatively large particles were reduced to D size. 50 The particles, measuring 24.201 μm, were all collected into a storage device for unified storage.

[0090] The large particles obtained from the final stage of grading and crushing enter the third stage for recycling. These large particles are fed into the recycling crushing device. During this process, some materials that are difficult to crush and have large particle sizes are continuously crushed by the main unit, resulting in a gradual reduction in particle size and improved compaction. This ensures that fine powder is not wasted. During the setup phase, the recycled material only needs to be circulated to stage D. 50 The required standard time (20 μm in this example) is recorded. After the required time for cyclic pulverization is reached, the final coarse particles are released into the mixing device.

[0091] Fine powder and small particles stored in the storage device are added to the mixing device after the large particles have been processed. In the mixing device, the coarse particles, fine powder, and small particles are thoroughly mixed. The particle size and compaction of the mixed material will meet the shaping requirements. The D of the mixed material... 50 The particle size was 18.534 μm, and after cyclic pulverization, coarse particles were collected as D. 50 The particle size is 20.354 μm, the sphericity is 0.77, and the fine powder collected during cyclic pulverization has a D value. 50 The particle size is 16.9 μm, and the following relationships must be satisfied: For finely ground powder D... 50 =Circular crushing of coarse particles D 50 ±7, circulating pulverization of fine powder D 50=Circulating crushed coarse particles ±6. In this embodiment, the standard for fine powder to be re-mixed is that the standard deviation of the distribution frequency curve of the material after circulating crushing is σx1≈5.63, σx2≈5.45, σx3≈5.24, all <7. The material after re-mixing must meet the following: Circulating crushed coarse particles = Crushed mixture ±3 (-3 < 18.534 - 20.354 = -1.82 < 3). The mixture is transported to the shaping machine, where the particles tend to be spherical through mutual collision and shearing between the materials. Since the large particles of the material have already achieved a certain degree of sphericity after circulating crushing, the morphology of the small particles is relatively easy to change, and the overall efficiency of the shaping process is greatly improved. After 20-25 minutes of shaping, the material passes the test and reaches the control value. D 50 The thickness is 18.012 μm. The single-product yield of the shaping equipment is 80%, and the tap density is 0.980 g / cm³. 2 , sphericity 0.90.

[0092] Electron micrographs of the mixture of coarse particles, fine powder, and small particles prepared in this embodiment, as well as the shaped material, are shown below. Figure 1 .

[0093] Example 3

[0094] Natural graphite raw materials are selected and fed into a coarse crushing device for coarse crushing. After coarse crushing, the particle size of the natural graphite raw materials is reduced, and the raw materials are broken down from lumps into powdery coarse graphite product. 50 The graphite crude material, with a diameter of 37.576 μm, is automatically transported to the next stage.

[0095] After coarse crushing, the natural graphite raw material is transported via automated pipeline to the second stage, a parallel stage consisting of two first-stage crushers, where the coarse graphite undergoes its first stage of grading. The resulting particles, D, meet the requirements for the final crushing result. 50 The particle size is 28.265 μm, and it enters the storage device for storage. The relatively larger particles formed after the first classification and crushing are transported through pipelines to the next stage for a second classification and crushing. The smaller particles after the second classification and crushing enter the storage device through transport pipelines, and the relatively larger particles also enter the next stage for a third classification and crushing, and so on. The particle size D of the fine powder is 28.265 μm each time. 50 After multiple crushing and grading processes at a temperature of 20±6, the relatively large particles were reduced to D size. 50 The particles, measuring 28.221 μm, were all collected into a storage device for unified storage.

[0096] The large particles obtained from the final stage of grading and crushing enter the third stage for recycling. These large particles are fed into the recycling crushing device. During this process, some materials that are difficult to crush and have large particle sizes are continuously crushed by the main unit, resulting in a gradual reduction in particle size and improved compaction. This ensures that fine powder is not wasted. During the machine setup phase, the recycling process is not recorded until the material reaches stage D. 50 The required standard time (20 μm in this example) is 10 minutes for circulating pulverization before the material is discharged. At this point, the coarse particles D... 50 =25.561, using crushing equipment to reduce material particle size D 50 The particle size decreased to 20.125 μm, with a sphericity of 0.68. The standard deviations of its material distribution frequency curves were calculated to be σx1≈6.55, σx2≈6.98, and σx3≈6.882. However, all data did not meet the standard deviation <7. In this case, although the circulating crushing of coarse particles D... 50 It meets the requirement of around 20μm, but the D of the fine powder after graded grinding and the coarse powder mixed at the end of grinding... 50 The difference is 8.086μm > 7μm, which does not meet the requirements. During cyclic pulverization, the micronized powder D... 50 =23.423 meets the requirements, and the D of the coarse powder mixed at the end of the crushing process is correct. 50 The difference is 3.298 < 6, which meets the requirements; try air mixing of coarse and fine powders in the crushing process, the mixture D 50 =23.015μm, which is the same as the D of the coarse powder mixed at the end of the crushing process. 50 The difference is (-3 < 23.015 - 20.125 = 2.89 < 3), which meets the requirements.

[0097] After 20-25 minutes of shaping, the material passes the test and meets the control limits. 50 The particle size was 20.542 μm. The single-product yield of the shaping equipment was 69%, and the tap density was 0.911 g / cm³. 2 The sphericity of 0.89 does not meet the standard.

[0098] Example 4

[0099] Natural graphite raw materials are selected and fed into a coarse crushing device for coarse crushing. After coarse crushing, the particle size of the natural graphite raw materials is reduced, and the raw materials are broken down from lumps into powdery coarse graphite product. 50 The graphite crude material, with a diameter of 38.455 μm, is automatically transported to the next stage.

[0100] After coarse crushing, the natural graphite raw material is transported to the second stage via an automated conveyor pipeline. A parallel stage consisting of two first-stage crushers will perform the first stage of grading and crushing of the coarse graphite. The particles obtained after this first stage of grading and crushing are small particles that meet the requirements of the final crushing result. 50The particle size is 27.351 μm, and it enters the storage device for storage. The relatively larger particles formed after the first classification and crushing are transported through pipelines to the next stage for a second classification and crushing. The smaller particles after the second classification and crushing enter the storage device through transport pipelines, and the relatively larger particles also enter the next stage for a third classification and crushing, and so on. The particle size D of the fine powder is 27.351 μm each time. 50 After multiple crushing and grading processes at a temperature of 20±6, the relatively large particles were reduced to D size. 50 The particles are 29.034 μm in size, and all of them are collected into the storage device for unified storage.

[0101] The large particles obtained from the final stage of grading and crushing enter the third stage for recycling. These large particles are fed into the recycling crushing device. During this process, some materials that are difficult to crush and have large particle sizes are continuously crushed by the main unit, resulting in a gradual reduction in particle size and improved compaction. This ensures that fine powder is not wasted. During the machine setup phase, the recycling process is not recorded until the material reaches stage D. 50 The required standard time (20 μm in this example) is 8 minutes for circulating pulverization before the material is discharged. At this point, the coarse particles D... 50 =26.943, using crushing equipment to reduce material particle size D 50 The particle size decreased to 19.955 μm, with a sphericity of 0.67. The standard deviations of its material distribution frequency curves were calculated to be σx1≈7.131, σx2≈7.045, and σx3≈7.052. However, all data did not meet the standard deviation <7. In this case, although the circulating crushing of coarse particles D... 50 It meets the requirement of around 20μm, but the D of the fine powder after graded grinding and the coarse powder mixed at the end of grinding... 50 The difference is 7.396μm > 7μm, which does not meet the requirements. During cyclic pulverization, the micronized powder D... 50 =24.251 meets the requirements, and the D of the coarse powder mixed at the end of the crushing process is correct. 50 The difference is 4.296 < 6, which meets the requirements; try air mixing of coarse and fine powders in the crushing process, the mixture D 50 =23.164μm, which is similar to the D of the coarse powder mixed at the end of the crushing process. 50 The difference is (3 < 23.164 - 19.955 = 3.209), which does not meet the requirements.

[0102] After 20-25 minutes of shaping, the material passes the test and meets the control limits. 50 The particle size is 20.976 μm. The single-product yield of the shaping equipment is 65%, and the tap density is 0.902 g / cm³. 2 The sphericity of 0.88 does not meet the standard.

[0103] Example 5

[0104] This embodiment provides a process for preparing spherical graphite, including:

[0105] Natural graphite raw materials are selected and fed into a coarse crushing device for coarse crushing. After coarse crushing, the particle size of the natural graphite raw materials is reduced, and the raw materials are broken down from lumps into powdery coarse graphite product. 50 The graphite sample, measuring 36.823 μm, is automatically transported to the next stage.

[0106] After coarse crushing, the natural graphite raw material is transported to the second stage via an automated conveyor pipeline. A parallel stage consisting of two first-stage crushers will perform the first stage of grading and crushing of the coarse graphite. The particles obtained after this first stage of grading and crushing are small particles that meet the requirements of the final crushing result. 50 The particle size is 20.891 μm, and it enters the storage device for storage. The relatively larger particles formed after the first classification and crushing are transported through pipelines to the next stage for a second classification and crushing. The smaller particles after the second classification and crushing enter the storage device through transport pipelines, and the relatively larger particles also enter the next stage for a third classification and crushing, and so on. The particle size D of the fine powder is 20.891 μm each time. 50 After multiple crushing and grading processes at a temperature of 20±6, the relatively large particles were reduced to D size. 50 The particles, measuring 23.128 μm, are all collected into a storage device for unified storage.

[0107] The large particles obtained from the final stage of grading and crushing enter the third stage for recycling. These large particles are fed into the recycling crushing device. During this process, some materials that are difficult to crush and have large particle sizes are continuously crushed by the main unit, resulting in a gradual reduction in particle size and improved compaction. This ensures that fine powder is not wasted. During the setup phase, the recycled material only needs to be circulated to stage D. 50 The required standard time (20 μm in this example) is recorded. After the required time for cyclic pulverization is reached, the final coarse particles are released into the mixing device.

[0108] Fine powder and small particles stored in the storage device are added to the mixing device after the large particles have been processed. In the mixing device, the coarse particles, fine powder, and small particles are thoroughly mixed. The particle size and compaction of the mixed material will meet the shaping requirements. The D of the mixed material... 50 The particle size is 20.012 μm. After cyclic pulverization, coarse particles are collected as D. 50 The particle size is 20.051 μm, the sphericity is 0.83, and the D of the fine powder collected during cyclic pulverization is... 50 The particle size is 19.4 μm, and the following relationships must be satisfied: For finely ground powder D... 50 =Circular crushing of coarse particles D 50 ±7, circulating pulverization of fine powder D 50=Circulating crushed coarse particles ±6. In this embodiment, the standard for fine powder to be re-mixed is that the standard deviation of the distribution frequency curve of the material after circulating crushing is σx1≈0.24, σx2≈0.85, σx3≈0.13, all <7 and close to 0. The material after re-mixing must meet the following: Circulating crushed coarse particles = Crushed mixture ±3 (-3 < 20.012 - 20.051 = -0.039 < 3). The mixture is transported to the shaping machine, where the particles tend to be spherical through mutual collision and shearing between the materials. Since the large particles of the material have already achieved a certain degree of sphericity after circulating crushing, the morphology of the small particles is relatively easy to change, and the overall efficiency of the shaping process is greatly improved. After 20-25 minutes of shaping, the material passes the test and reaches the control value. D 50 The particle size is 17.523 μm. The single-product yield of the shaping equipment is 86%, and the tap density is 0.975 g / cm³. 2 , sphericity 0.90.

[0109] Comparative Example 1

[0110] Traditional craftsmanship:

[0111] This comparative example demonstrates the traditional process for spherical graphite, which involves a series of 15 crushers and 6 shaping machines for crushing, shaping, and grading.

[0112] Natural graphite raw materials are selected and fed into a coarse crushing device for graded crushing. After coarse crushing, the particle size of the natural graphite raw materials is reduced. The primary feed, secondary feed, and tail feed further break down the natural graphite raw materials from lumps into powdery coarse graphite products. Only the primary feed coarse particles are collected each time. The equipment is connected in series, and the material is continuously graded and crushed. After the crushing process is completed, the material D 50 =21.385μm, sphericity 0.382, the standard deviations of the cubic distribution frequency curves of the coarse powder are calculated as σc1≈7.45, σc2≈8.01, σc3≈7.92, all >7. The material is relatively wide, making fine powder re-blending impossible. Furthermore, the first batch of second-pass feed fine powder was tested. 50 =28.661μm, calculate the ratio of coarse to fine particles, and conduct a blending experiment D with the materials according to the ratio. 50 =26.205μm, D 50 The surface rises to 4.820 μm, and shaping cannot reduce D. 50 The material was reduced and did not meet the standards. Therefore, traditional processes cannot mix materials. After the crushed mixture is shaped by subsequent shaping equipment, the material passes the test and reaches the control value. 50 The thickness is 18.012 μm. The single-product yield of the shaping equipment is 45%, and the tap density is 0.896 g / cm³. 2 , sphericity 0.88.

[0113] Comparison of particle yield between the comparative example and the embodiment:

[0114]

[0115] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A process for preparing spherical carbon materials, characterized in that, include: The crude carbon material is subjected to at least one stage of pulverization to obtain the pulverized material. The graded pulverized material is then subjected to cyclic pulverization to obtain cyclic pulverized material; The recycled pulverized material is mixed with at least one set of recycled materials to obtain a mixture, which is then shaped to obtain the spherical carbon material. Simultaneously, the small carbon particles generated during the graded crushing and / or cyclic crushing are collected at least once to obtain the collected material, and the recycled material includes the collected material; Among them, at least one set of the recycled admixtures has a D 50 With the D of the recycled pulverized material 50 Different, and the D of the mixture 50 With the D of the recycled pulverized material 50 The absolute value of the difference is 0-3 μm; The particle size distribution width deviation coefficient σ of the recycled pulverized material is ≤7; The collected material is in two or more groups, with D between each group of collected material. 50 The absolute value of the difference is less than 7 μm; The recycled crushed material D 50 With the re-admixture D 50 The absolute value of the difference is less than 6 μm; Each time the collection is completed, a set of collected materials is obtained, and the D of each set of collected materials is... 50 Not exactly the same; the raw materials for the carbon material include natural graphite.

2. The preparation process of the spherical carbon material according to claim 1, characterized in that, The carbon content of the natural graphite is over 94%.

3. The preparation process of the spherical carbon material according to claim 1, characterized in that, The natural graphite includes flake graphite and microcrystalline graphite.

4. The preparation process of the spherical carbon material according to claim 1, characterized in that, The preparation process satisfies at least one of the following characteristics (1) to (3): (1) The D of the crude carbon material 50 20-70μm; (2) The D of the graded and crushed material 50 It is 10-40 μm; (3) The time for each crushing and grading is less than 2 hours.

5. The preparation process of the spherical carbon material according to claim 1, characterized in that, The preparation process satisfies at least one of the following features (1) to (5): (1) The D of the recycled crushed material 50 It is 7-30μm; (2) The sphericity of the recycled crushed material is greater than 0.7; (3) The D of the recycled material 50 10-35μm; (4) The shaping time is 20-30 minutes; (5) The D of the collected material 50 It is 10-35μm.

6. A spherical carbon material, characterized in that, It is prepared by the spherical carbon material preparation process described in any one of claims 1-5.

7. The spherical carbon material according to claim 6, characterized in that, The spherical carbon material is spherical graphite.

8. The spherical carbon material according to claim 7, characterized in that, The spherical carbon material satisfies at least one of the following characteristics (1) to (3): (1) D 50 The thickness is 8-30 μm; (2) Tap density ≥ 0.9 g / cm²; (3) Sphericity greater than 0.

9.

9. A negative electrode material, characterized in that, It includes a matrix and a spherical carbon material as described in any one of claims 6-8, wherein the spherical carbon material is coated on the surface of the matrix.

10. A lithium battery, characterized in that, It includes the negative electrode material as described in claim 9.

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