Modified green coke material, its preparation method and use

Abstract

The present application discloses a modified green coke material and its preparation method and use. [Means] In the polarization structure of the modified raw coke material, the sum of the ratio of the long fiber structure and the wide area structure is 55-99%, and the volatile content of the modified coke material is 1%≦<5%. The modified raw coke material of the present application has a large amount of the long fiber structure and the wide area structure in the modified raw coke, effectively reducing the volatile content, further eliminating the light components, and eliminating the self-caking property of the raw material, so that the graphite anode material is not further aggregated in the subsequent heat treatment process for preparing graphite, and the graphite anode material is prepared from the modified raw coke material, which effectively improves the graphitization degree, specific capacity and press density of the artificial graphite anode, thereby achieving a comprehensive improvement in the performance of the graphite anode material.

Description

[Technical Field]

[0001] The embodiments of this application relate to the technical field of graphite preparation raw materials, for example, to modified green coke materials, and to methods for preparing and using the same. [Background technology]

[0002] As a core component of a battery, the negative electrode material plays a crucial role in its overall performance. Among the relevant types of negative electrode materials, graphite-based materials have advantages such as a low charge / discharge plateau, high theoretical lithium insertion capacity, and good conductivity, making them a popular negative electrode material for commercial lithium-ion batteries. Natural graphite has advantages such as high specific capacity, low cost, and abundant resources, and is widely used in the field of commercial negative electrode materials. However, its poor compatibility with electrolytes, high initial irreversible capacity, and poor charge / discharge ratio performance directly affect its use in lithium-ion batteries requiring long cycle life and high ratio performance. Synthetic graphite has good compatibility with electrolytes and relatively good cycle and ratio performance, making it a suitable negative electrode material for power batteries requiring long cycle life and high ratio performance.

[0003] Conventional artificial graphite always uses green coke material as a raw material, but the structure of typical green coke is not sufficiently developed, and there are many residual light components, which negatively affects the ease of graphitization. As a result, the degree of graphitization, specific volume, and press density of the graphitized product are low, and it cannot meet the need for high-energy-density graphite anode material. Conventional green coke has a high volatile content, usually 4% to 15%, and some green coke raw materials with high volatile content are prone to agglomeration and even solidification during the heat treatment process, which increases the cost of breaking down and dispersing the agglomeration in the next process.

[0004] For example, CN109748274A discloses a low-cost method for preparing composite particle graphite anode material. A mixed material is obtained by mixing coke material and asphalt powder in a mass ratio of 100:1 to 100:20. The mixed material is placed in a graphitization furnace and graphitized to obtain composite particle graphitized material. The composite particle graphitized material is classified to obtain classified material. The classified material is sieved and demagnetized to obtain composite particle graphite anode material. The coke-like material in this document is raw coke (unfired needle coke).

[0005] Furthermore, for example, CN111354927A discloses a composite graphite anode material, a lithium-ion battery, and a method for manufacturing and using the same. The manufacturing method includes the following steps: S1: Prepare a mixture of raw coke powder before calcination, flake graphite powder, a graphitization catalyst, and a graphitizable binder. However, the mass ratio of raw coke powder before calcination to flake graphite powder is 1:1.5 to 1:4, the amount of graphitization catalyst is 0.1 to 0.8% of the mass sum of raw coke powder before calcination and flake graphite powder, and the amount of graphitizable binder is 1 to 9% of the mass sum of raw coke powder before calcination and flake graphite powder. S2: Carbonization treatment. S3: Catalytic graphitization high-temperature treatment.

[0006] The graphite raw materials used in the above-mentioned literature all utilize green coke, and to a certain extent, they fail to meet the need for high-energy-density graphite anode materials, resulting in situations where graphite materials with good overall electrochemical performance cannot be obtained.

[0007] Therefore, how to modify the coke-like raw material of the graphite material to improve the performance of the subsequently prepared graphite anode material, such as its specific capacity, initial efficiency, and press density, is a technical problem that urgently needs to be solved. [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] The following is a general overview of the subject matter described herein. This overview is not intended to limit the scope of the claims.

[0009] The embodiments of this application provide a modified green coke material, a method for preparing it, and its use. The modified green coke material according to this application has an increased amount of elongated fibrous and broad-area structures in the modified green coke, effectively reducing volatile components, further eliminating light components, and eliminating the self-coagulating properties of the raw material. As a result, it does not further aggregate during the subsequent heat treatment process for preparing graphite. By preparing a graphite anode material with this modified green coke material, it is possible to effectively improve the degree of graphitization, specific volume, and press density of the artificial graphite anode, thereby achieving an overall improvement in the performance of the graphite anode material. [Means for solving the problem]

[0010] In a first embodiment, the present invention provides a modified green coke material in which the sum of the proportions of elongated fiber structure and broad region structure in the polarized structure of the modified green coke material is 55 to 99%, and the volatile content of the modified green coke material is 1% ≤ 5%.

[0011] The modified green coke material according to this application has an increased amount of elongated fiber structure and broad-area structure in the modified green coke, and the volatile content of the modified green coke is effectively reduced, light components are further eliminated, and the self-cohesiveness of the raw material is eliminated, so that it does not further aggregate during the subsequent heat treatment process to prepare graphite, and a graphite anode material can be obtained by preparing it with the modified green coke material, effectively improving the degree of graphitization, specific capacity and press density of the artificial graphite anode, while maintaining the good characteristics of low expansion and strong charging performance of green coke, thereby achieving an overall improvement in the performance of the graphite anode material. If the volatile content of the modified green coke is too low, below 1%, it means excessive heat treatment, and the heat-treated green coke develops characteristics similar to post-calcined coke (for example, the spacing between layers after graphitization becomes smaller), so the graphite prepared subsequently is prone to expansion during the charge-discharge process, resulting in poor strong charging performance and cycle life. If the volatile content is too high, exceeding 5%, it indicates insufficient heat treatment, resulting in incomplete crystal growth of the green coke material. This limits the effectiveness of improving the gram capacity and press density of the subsequently prepared graphite anode material.

[0012] For example, the volatile content of the modified green coke material may be 1%, 1.3%, 1.5%, 1.8%, 2%, 2.3%, 2.5%, 2.8%, 3%, 3.3%, 3.5%, 3.8%, 4%, 4.3%, 4.5%, 4.8%, 4.9% or 4.95%. The sum of the ratios of the slender fiber structure and the wide-area structure may be 55%, 58%, 60%, 63%, 65%, 68%, 70%, 73%, 75%, 78%, 80%, 83%, 85%, 88%, 90%, 93%, 95%, 98% or 99%.

[0013] Preferably, the hard glove grindability index of the modified green coke material is 20-100, and may be, for example, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 or 100.

[0014] Preferably, in the modified green coke material, the volatile content is 2% ≤ volatile content < 5%, and may be, for example, 2%, 2.3%, 2.5%, 2.8%, 3%, 3.3%, 3.5%, 3.8%, 4%, 4.3%, 4.5%, 4.8%, 4.9% or 4.95%.

[0015] In the present application, when the volatile content of the modified green coke material is 2% ≤ volatile content < 5%, it is more advantageous for the development of the slender fiber structure and the wide-area structure of the green coke material. Thereby, after graphitizing the modified green coke material, its gram capacity and press density can be effectively improved, and at the same time, the good characteristics of the low expansibility and strong charge performance of the green coke are maintained.

[0016] Preferably, the true density of the modified green coke material is 1.4-2 g / cm 3 , for example, 1.4 g / cm 3 , 1.41 g / cm 3 , 1.42 g / cm 3 , 1.43 g / cm 3 , 1.44 g / cm 3 , 1.45 g / cm 3 , 1.46 g / cm 3 , 1.47 g / cm 3, 1.48 g / cm 3 , 1.49 g / cm 3 , 1.5 g / cm 3 , 1.6 g / cm 3 , 1.7 g / cm 3 , 1.8 g / cm 3 , 1.9 g / cm 3 or 2 g / cm 3 etc., and preferably 1.4 - 1.5 g / cm 3 .

[0017] In the present application, when the modified green coke material has a true density in the range of 1.4 - 1.5 g / cm 3 , the development of green coke crystals can be better realized. When the true density exceeds 1.5 g / cm 3 , the graphite prepared subsequently is likely to expand during the charge-discharge process, and its high-charge performance and cycle life are poor. When the true density is too small, it is also disadvantageous for the development of green coke crystals, resulting in low gram capacity and press density after graphitization.

[0018] As a second aspect, the embodiments of the present application provide a method for preparing a modified green coke material, including the step of treating the raw green coke material to obtain green coke particles with a D50 of 0.1 - 5 mm, and then performing low-temperature heat treatment to obtain the modified green coke material.

[0019] The present application strictly limits the low-temperature heat treatment for raw green coke material to be modified and for green coke particles with a D50 of 0.1 - 5 mm. After low-temperature heat treatment, the medium-short fiber structure in green coke can further develop into a long and slender fiber structure, improving the ratio in the polarized structure of the long and slender fiber structure and the wide-area structure. At the same time, the volatile matter is effectively reduced, the light components are further removed, and the self-bonding property of the raw material and the agglomeration phenomenon that occurs to the particles during the heat treatment process are eliminated, so that the graphitization degree, specific capacity, and press density of the artificial graphite negative electrode material prepared with the modified green coke material as the raw material can be improved.

[0020] In the present application, when the D50 of the green coke particles exceeds 5 mm, during the low-temperature heat treatment process, the volatiles are not sufficiently discharged, the crystal development is incomplete, and the sum of the ratios of the long and thin fiber structure and the wide-area structure is 55 to 99% and 1% ≤ volatile matter < 5%, making it difficult to obtain a modified green coke material. Similarly, when the D50 is less than 0.1 mm, during the low-temperature heat treatment process, the size is too small, which hinders the crystal development process during the heat treatment process, and it is still difficult to obtain the above-mentioned modified green coke material.

[0021] For example, the green coke particles may be 0.1 mm, 0.3 mm, 0.5 mm, 0.8 mm, 1 mm, 1.3 mm, 1.5 mm, 1.8 mm, 2 mm, 2.3 mm, 2.5 mm, 2.8 mm, 3 mm, 3.5 mm, 3.8 mm, 4 mm, 4.3 mm, 4.5 mm, 4.8 mm or 5 mm, etc.

[0022] Preferably, the raw green coke material includes any one or at least a combination of two of petroleum coke green coke, needle coke green coke, pitch coke green coke or mesophase coke.

[0023] Preferably, the treatment method includes performing screening and / or crushing.

[0024] Preferably, the D50 of the green coke particles is 0.3 to 3.0 mm, such as 0.3, 0.5 mm, 0.8 mm, 1 mm, 1.2 mm, 1.3 mm, 1.5 mm, 1.6 mm, 1.8 mm, 2 mm, 2.2 mm, 2.3 mm, 2.5 mm, 2.6 mm, 2.8 mm or 3 mm, etc.

[0025] In the present application, when the D50 of the green coke particles is further in the range of 0.3 to 3.0 mm, it can more effectively improve the gram capacity and press density after graphitization of the modified green coke, and at the same time maintain the good characteristics of the low expansibility and strong charge performance of the green coke.

[0026] Preferably, the temperature of the low-temperature heat treatment is 500 to 900°C, for example, 500°C, 530°C, 550°C, 580°C, 600°C, 630°C, 650°C, 680°C, 700°C, 730°C, 750°C, 780°C, 800°C, 830°C, 850°C, 880°C, or 900°C.

[0027] Preferably, the duration of the low-temperature heat treatment is 2 to 6 hours, for example, 2 hours, 3 hours, 4 hours, 5 hours, or 6 hours.

[0028] In this invention, if the temperature of the low-temperature heat treatment is too low and the time is too short, the development of crystals and the discharge of volatile components cannot be properly achieved, and the gram capacity and press density of the material after graphitization cannot be effectively improved. On the other hand, if the temperature is too high and the time is too long, the graphite prepared in the subsequent process is prone to expansion during the charge-discharge process, resulting in poor high-charge performance and cycle life after graphitization.

[0029] In other words, the present invention provides a modified green coke material prepared by adjusting and controlling the D50 of green coke particles along with the temperature and time of low-temperature heat treatment, such that the sum of the proportions of elongated fibrous structure and broad structure is 55-99% and 1% ≤ volatile matter < 5%. This material maintains the good properties of green coke, such as low expansion and strong charging performance, after graphitization, and can significantly improve its degree of graphitization, gram capacity, and press density.

[0030] Preferably, during the low-temperature heat treatment process, the oxygen gas content is 500 ppm or less, such as 500 ppm, 450 ppm, 400 ppm, 350 ppm, 300 ppm, 250 ppm, 200 ppm, 150 ppm, 100 ppm, 50 ppm, or 0 ppm.

[0031] This invention addresses the fact that in the low-temperature heat treatment process, if the oxygen gas content is too high, the burning of the material increases, further creating safety risks and being detrimental to the further graphitization of modified green coke.

[0032] As a preferred technical solution, the preparation method is: The process includes the steps of crushing raw coke material to obtain raw coke particles with a D50 of 0.1 to 5 mm, and then subjecting them to low-temperature heat treatment at a temperature of 500 to 900°C for 2 to 6 hours to obtain the modified raw coke material.

[0033] In a third aspect, the embodiment of the present application provides a graphite anode material obtained by graphitizing the modified green coke material described in the first aspect.

[0034] The methods for preparing the artificial graphite anode material according to this application are all general technical means, that is, feasible in related technologies, and all methods that use coke-like material as one of the raw materials are applicable to this application. In other words, the raw coke-modified material according to this application may be used as all of the raw materials for the artificial graphite anode material, or as one of the raw materials for the artificial graphite anode material.

[0035] Exemplaryly, the present invention provides a preparation process for preparing a graphite anode material using a modified green coke material according to the present invention. 1) The modified green coke is crushed, and the D50 after crushing is 8-20 μm. 2) The modified green coke after the above grinding is subjected to graphitization treatment, with a graphitization temperature of 2500-3500°C.

[0036] In step 2) above, the material may be treated before or after graphitization, or further treated using methods such as classification, modification, coating, or granulation.

[0037] In a fourth aspect, the embodiments of the present application further provide a lithium-ion battery comprising the graphite anode material described in the third aspect. [Effects of the Invention]

[0038] Compared to the prior art, the embodiments of this application have the following beneficial effects.

[0039] (1) The modified green coke material according to the embodiment of the present application has an increased amount of elongated fibrous structure and broad-area structure in the modified green coke, and volatile matter is effectively reduced, light components are further eliminated, and the self-cohesiveness of the raw material is eliminated, so that it does not further aggregate in the subsequent heat treatment process to prepare graphite, and a graphite anode material can be obtained by preparing with the modified green coke material, thereby effectively improving the degree of graphitization, specific volume and press density of the artificial graphite anode, and achieving an overall improvement in the performance of the graphite anode material. In the present application, the volatile matter of the modified green coke material obtained by adjusting and controlling the D50 of the green coke particles in the preparation process and the temperature and time of the low-temperature heat treatment is 1% ≤ volatile matter < 5%, and the true density is in the range of 1.4~2 g / cm³. 3 In this case, a battery using graphite material obtained from modified green coke material as the negative electrode has a gram capacity of 352.1 mAh / g or more at 1C, and the lithium deposition situation of the negative electrode is observed when the battery is charged to 100% SOC at different magnifications (magnifications are 1C, 2C, 3C, 4C, 5C, and 6C), and its charging window is 1 to 5C or more.

[0040] (2) The preparation method according to the embodiment of the present invention can obtain a modified green coke material with superior performance precisely because it strictly controls the D50 of the green coke particles in the modification process, as well as the temperature and time of the heat treatment. The preparation method is simple to operate, does not require complex processing steps, and is applicable to large-scale production.

[0041] After reviewing and understanding the drawings and detailed descriptions, other aspects can also be understood. [Brief explanation of the drawing]

[0042] The drawings are provided to provide an understanding of the technical solution described herein, constitute part of the specification, and are intended to be used in conjunction with the embodiments of the present application to interpret the technical solution of the present application, and do not limit the technical solution of the present application.

[0043] [Figure 1] This is a polarized photograph of modified petroleum coke according to Example 1. [Figure 2]This is a polarized image of primitive petroleum coke (unmodified) related to Comparative Example 1. [Modes for carrying out the invention]

[0044] The technical solution of the present application will be further described below with reference to specific embodiments. Those skilled in the art should understand that the above embodiments are merely for the purpose of understanding the present application and should not be considered as specifically limiting the present application.

[0045] In one specific embodiment, the present application provides a method for preparing a modified green coke material, comprising the following steps:

[0046] The raw coke material is crushed to obtain coke particles with a D50 of 0.1 to 5 mm, and then subjected to low-temperature heat treatment at a temperature of 500 to 900°C for 2 to 6 hours in an environment with an oxygen gas content of ≤ 500 ppm to obtain the modified coke material.

[0047] However, the raw coke material includes one or at least two of the following: petroleum coke raw coke, needle coke raw coke, pitch coke raw coke, or intermediate phase coke.

[0048] Examples 1-4 Examples 1 to 4 provide modified petroleum coke materials. The volatile content, hard globe pulverability index (HGI), true density, and the sum of the ratios of elongated fibers and broad structures in the polarized structure of the modified petroleum coke materials are shown in Table 1.

[0049] Examples 1 to 4 further provide methods for preparing modified petroleum coke materials. The preparation methods provided based on specific embodiments involve an oxygen content of less than 500 ppm during the low-temperature heat treatment process, a volatile content of 10% in the raw petroleum coke raw materials, and other parameters shown in Table 1.

[0050] Comparative Example 1 In this comparative example, no treatment is performed on the petroleum coke material.

[0051] Comparative Examples 2-6 Comparative Examples 2 to 6 provide modified petroleum coke materials. Table 1 shows the volatile content, hard globe pulverability index (HGI), true density, and the sum of the ratios of elongated fibers and broad structures in the polarized structure of the modified petroleum coke materials.

[0052] Comparative Examples 2-6 further provide methods for preparing modified petroleum coke materials. The preparation methods provided based on specific embodiments involve an oxygen content of less than 500 ppm during the low-temperature heat treatment process, a volatile content of 10% in the raw petroleum coke raw materials, and other parameters as shown in Table 1.

[0053] Figure 1 shows a polarized image of modified petroleum coke according to Example 1, and Figure 2 shows a polarized image of raw petroleum coke (unmodified) according to Comparative Example 1. As can be seen from the comparison between Figure 1 and Figure 2, the elongated fibrous structure and broad-area structure were clearly improved in the low-temperature heat-treated green coke. From the proportion of elongated fibrous structure and broad-area structure in the polarized images, it was found that the sum of the proportions of elongated fibrous structure and broad-area structure in the modified green coke was 55-99%.

[0054] [Table 1]

[0055] Modified or unmodified (Comparative Example 1) petroleum coke materials from Examples 1-4 and Comparative Examples 1-6 were used as raw materials for artificial graphite anode materials to prepare artificial graphite anode materials. The preparation process is as follows.

[0056] 1 )raw The coke is crushed, and the D50 after crushing is 15 μm.

[0057] 2) After the above grinding raw After classifying the coke, it is subjected to graphitization, with a graphitization temperature of 3000°C.

[0058] The modified or unmodified (Comparative Example 1) petroleum coke materials from Examples 1-4 and Comparative Examples 1-6 were sequentially crushed, classified, and graphitized to obtain artificial graphite anode materials.

[0059] Button-type batteries were obtained by manufacturing them using the artificial graphite anode materials described in Examples 1-4 and Comparative Examples 1-6. The test conditions for gram capacity were room temperature, 1C constant current charge / discharge, and a charge / discharge cutoff voltage of 0.005V to 2V. The charging window was defined as the range in which the batteries were charged to 100% SOC at different magnifications (magnifications of 1C, 2C, 3C, 4C, 5C, and 6C) without lithium deposition occurring on the anode sheet. The results are shown in Table 2.

[0060] [Table 2]

[0061] As can be seen from the data results of Examples 1 and 4, when the true density was too high, exceeding 1.5, and the volatile content was below 2%, it was detrimental to improving the high-charge performance of the graphitized material.

[0062] As can be seen from the data results of Example 1 and Comparative Examples 2-4, in the process of preparing modified green coke material, if the green coke particles before low-temperature heat treatment are too small (less than 0.1 mm) or too large (more than 5 mm), it is not possible to prepare a modified green coke material in which the sum of the proportions of elongated fibrous structure and broad structure is 55-99% and 1% ≤ volatile matter < 5%, and thus it is not possible to simultaneously improve the gram capacity and strong charging performance of the material after graphitization.

[0063] As can be seen from the data results of Example 1, Comparative Example 5, and Comparative Example 6, in the process of preparing modified green coke material, even if the particle size of the green coke particles is in the range of 0.1 to 5 mm, if the temperature is too low, the improvement in the gram capacity of the material after graphitization is not significant, and if the temperature is too high, it affects the strong charge performance of the material after graphitization.

[0064] Overall, as can be seen from the data results of Example 1 and Comparative Examples 2-6, the process of preparing the modified green coke material must simultaneously satisfy the particle size, temperature, and time ranges of the green coke, and because these factors act synergistically, the modified green coke material expected in this application can be obtained, and the specific capacity of the subsequent artificial graphite anode material can be improved.

[0065] Examples 5-9 Examples 5 to 9 provide modified pitch coke materials. Table 3 shows the volatile content, hard globe pulverability index (HGI), true density, and the sum of the ratio of elongated fibers to broad structures in the polarized structure of the modified pitch coke materials.

[0066] Examples 5 to 9 further provide methods for preparing modified pitch coke materials. The preparation methods provided based on specific embodiments involve an oxygen content of less than 500 ppm during the low-temperature heat treatment process, a volatile content of 6% in the original pitch coke raw material, and other parameters shown in Table 3.

[0067] Comparative Example 7 In this comparative example, no treatment is performed on the pitch coke material.

[0068] Comparative Examples 8-10 Comparative Examples 8-10 provide modified pitch coke materials. The volatile content, hard globe pulverability index (HGI), true density, and sum of the ratio of elongated fibers to broad structures in the polarized structure of the modified pitch coke material are shown. 3 This will be shown.

[0069] Comparative Examples 8-10 further provide methods for preparing modified pitch coke materials. The preparation methods provided based on specific embodiments involve an oxygen content of less than 500 ppm during the low-temperature heat treatment process, a volatile content of 10% in the original pitch coke raw material, and other parameters shown in Table 3.

[0070] [Table 3]

[0071] Modified or unmodified (Comparative Example) in Examples 5-9 and Comparative Examples 7-10 7 The pitch coke material was used as a raw material for the artificial graphite anode material to prepare and obtain the artificial graphite anode material. The preparation process is as follows.

[0072] 1 )raw The coke was crushed, and the D50 after crushing was 15 μm.

[0073] 2) After the above grinding raw After classifying the coke, it is subjected to graphitization, with a graphitization temperature of 3000°C.

[0074] Modified or unmodified (Comparative Example) in Examples 5-9 and Comparative Examples 7-10 7 The pitch coke material was sequentially crushed, classified, and graphitized to obtain an artificial graphite anode material.

[0075] Button-type batteries were manufactured using the artificial graphite anode materials described in Examples 5-9 and Comparative Examples 7-10. The test conditions for gram capacity were room temperature, 1C constant current charge / discharge, and a charge / discharge cutoff voltage of 0.005V to 2V. The charging window was defined as the charge range in which the battery was charged to 100% SOC at different charge levels (1C, 2C, 3C, 4C, 5C, and 6C) without lithium deposition occurring on the anode sheet. The results are shown in Table 4.

[0076] [Table 4]

[0077] As can be seen from the data results of Examples 5, 7, and 8, when the true density was too high, exceeding 1.5, and the volatile content was below 2%, it was detrimental to improving the high-charge performance of the graphitized material.

[0078] As can be seen from the data results of Example 5 and Comparative Example 7, if no modification treatment is performed on the green coke material, the short fibers in the green coke material cannot further develop into long fibers, and therefore it is not possible to improve the gram capacity after graphitization.

[0079] Examples 5 As can be seen from the data results of Comparative Examples 8-10, in the process of preparing modified green coke material, the temperature, time, and D50 of the green coke particles of the low-temperature heat treatment must be satisfied simultaneously and act synergistically. Only then can modification of the green coke material be achieved. Furthermore, if only one of the two conditions is satisfied by improving the specific capacity of the artificial graphite anode material, it will affect the development of the green coke crystals, and the objective of improving the gram capacity after graphitization cannot be achieved.

[0080] Examples 10-13 Examples 10-13 provide modified needle coke materials. The volatile content, hard globe pulverability index (HGI), true density, and sum of the ratio of elongated fibers to broad structures in the polarized structure of the modified needle coke material are expressed. 5 This will be shown.

[0081] Examples 10-13 further provide methods for preparing modified needle coke materials. The preparation methods provided based on specific embodiments involve an oxygen content of less than 500 ppm during the low-temperature heat treatment process, a volatile content of 6% in the original needle coke raw material, and other parameters shown in Table 5.

[0082] Comparative Example 11 In this comparative example, no treatment is performed on the needle coke material.

[0083] Comparative Examples 12-13 Comparative Examples 12-13 provide modified needle coke materials. The volatile content, hard globe pulverability index (HGI), true density, and the sum of the ratio of elongated fibers to broad structures in the polarized structure of the modified needle coke material are shown. 5 This will be shown.

[0084] Comparative Examples 12-13 further provide methods for preparing modified needle coke materials. The preparation methods provided based on specific embodiments involve an oxygen content of less than 500 ppm during the low-temperature heat treatment process, a volatile content of 10% in the original needle coke raw material, and other parameters shown in Table 5.

[0085] [Table 5]

[0086] Examples 10-13 and Comparative Examples 11- 13 Modified or unmodified (Comparative Example) 11 The needle coke material was used as a raw material for the artificial graphite anode material to prepare the artificial graphite anode material. The preparation process is as follows.

[0087] 1 )raw The coke was crushed, and the D50 after crushing was 15 μm.

[0088] 2) After the above grinding raw After classifying the coke, it is subjected to graphitization, with a graphitization temperature of 3000°C.

[0089] Modified or unmodified (Comparative Example) in Examples 10-13 and Comparative Examples 11-13 11 The needle coke material was sequentially crushed, classified, and graphitized to obtain an artificial graphite anode material.

[0090] Button-type batteries were obtained by manufacturing them using the artificial graphite anode materials described in Examples 10-13 and Comparative Examples 11-12. The test conditions for gram capacity were room temperature, 1C constant current charge / discharge, and a charge / discharge cutoff voltage of 0.005V to 2V. The charging window was defined as the range in which the battery was charged to 100% SOC at different magnifications (magnifications of 1C, 2C, 3C, 4C, 5C, and 6C) without lithium deposition occurring on the anode sheet. The results are shown in Table 6.

[0091] [Table 6]

[0092] As can be seen from the data results of Examples 10, 12, and 13, when the true density was too high, exceeding 1.5, and the volatile content was below 2%, it was detrimental to improving the strong charging performance of modified green coke after graphitization.

[0093] As can be seen from the data results of Example 10 and Comparative Example 11, if no modification treatment is performed on the green coke material, the short fibers in the green coke material cannot further develop into long fibers, and volatile components in the green coke cannot be discharged, making it impossible to improve the specific volume of the modified green coke after graphitization.

[0094] As can be seen from Tables 1 to 6, the modified green coke material according to this application can be obtained precisely because the D50 of the green coke particles, and the temperature and time of the low-temperature heat treatment must be simultaneously satisfied during the preparation process. At the same time, the volatile content of the modified green coke material must be 2% ≤ volatile content < 5%, and the true density must be in the range of 1.4 to 1.5 g / cm³. 3 In this case, the subsequent preparation of the artificial graphite anode material is less prone to aggregation, resulting in better performance and higher specific capacity of the obtained graphite anode material.

[0095] In short, the modified green coke material according to this application effectively reduces volatile matter, further eliminates light components, and eliminates the self-coagulation properties of the raw material, preventing further aggregation during the subsequent heat treatment process to prepare graphite. The modified green coke has a greater proportion of elongated fibrous structures and broad-area structures, and by preparing a graphite anode material with this modified green coke material, the degree of graphitization, specific volume, and press density of the artificial graphite anode can be effectively improved, resulting in an overall improvement in the performance of the graphite anode material. In this application, the volatile matter of the modified green coke material obtained by adjusting and controlling the D50 of the green coke particles in the preparation process and the temperature and time of the low-temperature heat treatment is 1% ≤ volatile matter < 5%, and the true density is in the range of 1.4~2 g / cm³. 3In this case, a battery using graphite material obtained from modified green coke material as the negative electrode has a gram capacity of 352.1 mAh / g or more at 1C, and the lithium deposition situation of the negative electrode when charging the battery to 100% SOC is observed at different magnifications (magnifications are 1C, 2C, 3C, 4C, 5C, and 6C), and its charging window is 1 to 5C or more.

[0096] The above describes only specific embodiments of the present application, but the applicant declares that the scope of protection of the present application is not limited thereto. A person skilled in the art should understand that any modification or substitution that is readily conceivable within the scope of the art disclosed herein is included within the scope of protection and disclosure of the present application.

Claims

1. The process involves processing raw coke material to obtain coke particles with a D50 of 0.1 to 5 mm, followed by low-temperature heat treatment at a temperature of 700 to 900°C for 2 to 6 hours to obtain modified coke material with a volatile content of 1% or more and less than 5%. The process includes the step of crushing the modified green coke material and subjecting it to graphitization to obtain a graphite anode material. Method for preparing graphite anode material.

2. The aforementioned raw coke material includes one or at least two of the following: petroleum coke raw coke, needle coke raw coke, pitch coke raw coke, or intermediate phase coke. A method for preparing a graphite anode material according to claim 1.

3. The processing method described above includes sieving and / or crushing, A method for preparing a graphite anode material according to claim 1.

4. The D50 of the aforementioned raw coke particles is 0.3 to 3.0 mm. A method for preparing a graphite anode material according to claim 1.

5. During the aforementioned low-temperature heat treatment process, the oxygen gas content is 500 ppm or less. A method for preparing a graphite anode material according to claim 1.

6. In the polarized structure of the modified green coke material, the sum of the proportions of elongated fibrous structure and broad-area structure is 55 to 99%. A method for preparing a graphite anode material according to claim 1.

7. The true density of the modified green coke material is 1.4 to 2 g / cm³. ３ That is, A method for preparing a graphite anode material according to claim 6.

8. The true density of the modified green coke material is 1.4 to 1.5 g / cm³. ３ That is, A method for preparing a graphite anode material according to claim 7.

9. The hard globe pulverability index of the modified green coke material is 20 to 100. A method for preparing a graphite anode material according to claim 6.

10. Of the modified green coke material, 2% ≤ volatile content < 5%. A method for preparing a graphite anode material according to claim 6.

11. The aforementioned crushing and graphitization treatment is Step (1) involves grinding the modified green coke material so that the D50 after grinding is 8 to 20 μm, The process includes step (2) of graphitizing the modified green coke material after pulverization, wherein the graphitization temperature is 2500 to 3500°C. A method for preparing a graphite anode material according to claim 1.

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