Drying method of negative electrode raw material coke

Abstract

The invention relates to a drying method of negative electrode raw material coke. The method comprises the following steps: (1) carrying out coarse crushing on raw material coke to obtain a material A; (2) fully stirring and mixing the obtained material A and activated aluminum oxide particles with the size of 10-15mm to obtain a mixed material B; (3) the mixed material B is subjected to standing and then screened with a 2.5-5-mesh coarse screen, oversize products are large-particle water-absorbing aluminum oxide drying agents, undersize materials are rapidly-dried raw material coke materials C, and the moisture content of the raw material coke materials C is not higher than 5%; and (4) carrying out a fine grinding process on the rapidly dried raw material coke material C so as to control the particle size D50 of the finely ground material to be 11-12 microns and D100 to be not greater than 60 microns. The drying method provided by the invention has a remarkable water removal effect on the experimental coke, is suitable for a heatless regeneration device, can achieve a remarkable water removal effect, and is simple, convenient and efficient.

Description

Technical Field

[0001] The invention relates to the technical field of processing raw material coke for lithium battery graphite negative electrode, and in particular to a method for quickly drying kilogram-level raw material coke after coarse crushing. Background Art

[0002] The graphite negative electrode of lithium-ion batteries is a key material for achieving the performance of lithium-ion batteries. The graphite negative electrode is generally prepared using raw materials such as petroleum coke, needle coke, and asphalt coke. By controlling the particle size, yield and other key indicators of each process link, the particle size, yield and other indicators required by the product can be finally met, achieving high initial coulombic efficiency and high specific capacity of the negative electrode graphite in the battery.

[0003] During the processing of lithium-ion battery graphite negative electrode, for specific raw material coke, too high incoming material moisture (more than 10%) will cause its wall sticking problem, affect the debugging of mill process parameters, and cause material blockage and loss. The rough crushing process of production materials involves a drying process based on gas hot air, but for the experimental raw material coke of kilogram-level small tests, due to the limited material quantity and various types, there is currently no specific drying method for the whole rough crushing process, and the effect and time of natural drying are greatly affected by the uncertain natural environment. Utility model CN222035783U discloses a lithium battery graphite raw material screening mechanism, which adopts a multi-layer heating guide plate with a condensing plate to realize the dehumidification function and drying of kilogram-level raw material coke. The utility model has two significant limitations: the equipment is relatively complex and costly, and only one material can be dried at a time, and multiple kilogram-level experimental materials cannot be processed at the same time; the mechanism requires multiple layers of hot plates and condensing plates to work, and requires more energy supply. From an economic point of view, long-term use will generate more cost consumption.

[0004] In order to achieve efficient, rapid and economical moisture control of kilogram-level coke, it is necessary to develop a rapid drying method for coke after coarse crushing. This method should reduce moisture without introducing new impurities, and at the same time, it does not require additional power / heat sources, can be used quickly in multiple locations and reduce energy consumption. Summary of the invention

[0005] Technical Purpose

[0006] One of the technical purposes of the present invention is to provide a rapid heatless drying method for raw coke, which has wide applicability and is not limited by site environment.

[0007] Another technical purpose of the present invention is to provide a lithium battery negative electrode material obtained by the above drying method.

[0008] Another technical purpose of the present invention is to provide a lithium-ion battery comprising a negative electrode made of the above-mentioned lithium battery negative electrode material.

[0009] Technical Solution

[0010] The present invention provides a method for rapid drying of raw coke, comprising the following steps:

[0011] (1) roughly crushing the raw coke to obtain material A;

[0012] (2) fully stirring and mixing the obtained material A and activated alumina particles having a size of 10 mm to 15 mm to obtain a mixed material B;

[0013] (3) After the mixed material B is allowed to stand, it is screened with a 2.5-5 mesh coarse screen. The material on the screen is a large particle water-absorbing alumina desiccant, and the material under the screen is the raw coke material C after rapid drying, and its moisture content is not higher than 5%;

[0014] (4) The raw coke material C after rapid drying is subjected to a fine grinding process to control the particle size of the finely ground material to D50 of 11-12 μm and D100 of no more than 60 μm.

[0015] In a specific embodiment, in step (1), the raw coke is selected from one of petroleum coke and pitch coke, and the petroleum coke is selected from needle coke, sponge coke or shot coke.

[0016] In a specific embodiment, in step (1), a kilogram-class jaw crusher is used to coarsely crush the raw coke, preferably to a size of less than 10 mm.

[0017] In a specific implementation, in step (1), the mass of the raw coke A is less than 100 kg.

[0018] In a specific embodiment, in step (2), the mass of the activated alumina particles is 5-20% of the mass of material A.

[0019] In a specific embodiment, in step (3), the standing time of the mixed material B is 30 min-3 h.

[0020] In a specific embodiment, in step (4), the collected material C is finely ground to obtain a material yield higher than 70%, wherein the yield is calculated as follows: material yield = mass of first-stage graded material in the experimental mill / total feed mass.

[0021] In another aspect, the present invention provides a graphite negative electrode material, which at least comprises the dried raw coke obtained by the above method.

[0022] In another aspect, the present invention provides a graphite negative electrode, which is prepared from the above-mentioned graphite negative electrode material.

[0023] In another aspect, the present invention provides a lithium-ion battery, which at least includes the above-mentioned graphite negative electrode.

[0024] In a specific embodiment, the negative electrode capacity of the lithium-ion battery is not less than 345 mAh / g, and the first coulombic efficiency is not less than 92%.

[0025] Beneficial Effects

[0026] The technical solution of this application is characterized by energy-saving and rapid drying of kilogram-level materials. Due to the material and size characteristics of the selected commercially available alumina, it has a hardness compatible with the raw coke and the possibility of subsequent screening among a wide range of desiccants. No suitable substitute has been found for other desiccants yet. For example, commonly used desiccants such as silica gel have insufficient hardness; for example, calcium desiccants are prone to chemical reactions after absorbing water, introducing by-product impurities into the material; for example, commercially available desiccants with a size of less than 10 mm cannot be effectively screened and separated from the material.

[0027] In this application, since the raw material particles after coarse crushing are small in size, large-particle activated alumina desiccant is introduced and fully mixed, and then passed through a coarse screen after standing, which can effectively separate the water-absorbed alumina desiccant and the coarse crushed material. Due to the high hardness of alumina particles, no additional impurities are found after mixing and screening. The target coarse crushed material is fully dried, and the alumina desiccant after absorbing water can be dried separately and reused.

[0028] The drying method of the present application has a significant water removal effect on experimental coke, is suitable for heatless regeneration equipment, can achieve a significant water removal effect, and the method is simple and efficient.

[0029] Compared with the prior art, the rapid drying method implemented in the present invention allows the kilogram-level coke source after rough crushing to be mixed and quickly absorb water and dry, and the different sizes of materials are used for rapid screening. Therefore, the drying method of the present application is suitable for the process preparation of graphite products for lithium batteries based on different types of kilogram-level raw coke, and can achieve a moisture reduction effect that is not lower than or better than that of tons of raw coke after rough crushing production equipment. As a result, kilogram-level raw coke can be quickly dried and stably verified in subsequent processes under non-thermal conditions, and the prepared product has stable performance. Accordingly, the method of the present application is a rapid non-thermal drying method with wide applicability that is not limited by the site environment.

[0030] It is further necessary to emphasize that the reasonable application goal of the technical solution of the present application is to quickly dry a large number of small-scale kilogram-level test materials of multiple batches and multiple types, rather than to produce tons of materials. The characteristics of graphite negative electrode products are strongly correlated with different types of coke sources. From the perspective of saving time and economic costs, the processing and testing process of kilogram-level raw coke is an important product development link. To this end, the technical solution of the present application helps to reduce costs, shorten the development cycle, and improve accuracy in the raw material processing process during the small-scale trial stage. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a flow chart of the rapid drying method based on the present application.

[0032] Figure 2 This is a scanning electron microscope image of the petroleum coke A ground material after being treated by the rapid drying method in Example 1.

[0033] Figure 3 This is a scanning electron microscope image of the naturally dried petroleum coke A powder material in Comparative Example 1. DETAILED DESCRIPTION

[0034] Hereinafter, the process implementation method of the present invention and the application of the method in raw coke are further described by specific examples, but the present invention is not limited to the following examples.

[0035] Materials and Apparatus:

[0036] Large particle activated alumina desiccant: Shanghai Yuejiang Titanium Dioxide Chemical; item number 230216038; specification 10-12mm or 12-15mm;

[0037] Scanning electron microscope: Guoyi Quantum SEM2100 scanning electron microscope.

[0038] Example 1

[0039] Take 5kg of petroleum coke A after coarse crushing by jaw crusher (the overall size of the material after coarse crushing is less than 10mm), introduce 500g of 15mm large-particle activated alumina desiccant, and mix thoroughly for 10min; let it stand for 1h, and pass it through a 2.5-mesh coarse sieve to effectively separate the water-absorbing alumina desiccant and the coarse crushed material. Detect the moisture content of the material. Finely grind the batch of petroleum coke that has been quickly dried. The fine grinding parameters are host frequency 17-20Hz, fan frequency 27Hz, feed frequency 6Hz, Ⅰ classification frequency 10Hz, Ⅱ classification frequency 52Hz. Collect the materials under Ⅰ classification. Collect the materials at the first discharge port of the mill.

[0040] Example 2

[0041] Take 3kg of coarsely crushed needle coke raw material B (volatile matter ≤8%, ash content ≤0.2%), introduce 14mm large-particle activated alumina desiccant and mix thoroughly; let it stand for 30 minutes, pass through a 2.5-mesh coarse sieve, separate the water-absorbed alumina desiccant and the coarsely crushed material. Detect the moisture content of the material. Then, finely grind it in the same way as in Example 1.

[0042] Example 3

[0043] The operation process is the same as that in Example 1, except that the mass of the introduced large-particle activated alumina desiccant is 1000 g.

[0044] Comparative Example 1

[0045] Take 5kg of crudely crushed petroleum coke A, dry it naturally for 4 hours, and then grind it directly into fine powder.

[0046] The moisture content of the naturally dried coarsely crushed material was detected. For the material that was not subjected to the rapid drying treatment, a fine grinding process was performed to detect the particle size. The same fine grinding parameters as in Example 1 were used. The material at the first discharge port of the mill was collected, and the yield of the finely ground material was calculated.

[0047] Comparative Example 2

[0048] Tons of production material petroleum coke A passed through the coarse crushing equipment and was sent out from the crawler after being dried by hot air from the production equipment. The moisture content and grinding particle size of the coarsely crushed material were tested.

[0049] The schematic diagram of the rapid drying process of this application is as follows Figure 1 As shown in the dashed box in Figure 1 As shown in the dotted box, the rapid drying section includes the steps of adding desiccant, stirring and mixing, standing and screening.

[0050] The general process of fine grinding in the above embodiments and comparative examples is as follows: taking the experimental mill as an example, the coarsely crushed material is finely ground, the main engine frequency is 17-20Hz, the fan frequency is 25-27Hz, the feed frequency is 5-8Hz, the I classification frequency is 5-12Hz, and the II classification frequency is 50-52Hz. Collect the material in the I classification.

[0051] Comparative Example 3

[0052] The operation process is the same as that in Example 1, except that the introduced desiccant is a 10 mm grade silica gel desiccant.

[0053] Due to the low hardness of silica gel, even if it is not broken up and collided, but just left to stand and screen according to the process, there will be residual broken dryer particles remaining on the surface of the material, which does not meet the requirements for further processing.

[0054] Test Example 1: Physical Property Test

[0055] (1) Moisture test

[0056] The moisture content of the coarsely crushed materials provided in Examples 1-3 and the coarsely crushed materials provided in Comparative Examples 1-2 was tested.

[0057] Moisture test method: weigh the material box, mix and sample 100g, put it into the material box, spread it evenly, and place it in a drying oven. Control the temperature at 105-110℃ and dry it for 4 hours. Weigh it after cooling.

[0058] The moisture test results are shown in Table 1 below.

[0059] Table 1

[0060]

[0061]

[0062] Results analysis: It can be seen from Examples 1-3 that the rapid drying method can effectively make the moisture content of different raw materials reach the target of less than 5% after coarse crushing, and the dosage of different desiccants can significantly promote the drying of materials. The moisture control effect of the tons of production materials after hot air drying in Comparative Example 2 is similar; while the moisture content of the coarse crushed materials in Comparative Example 1 is still higher than the control target after natural drying.

[0063] (2) Particle size test

[0064] The finely ground materials of Example 1 and Comparative Examples 1-2 were tested for particle size by a laser particle size analyzer. The laser particle size test method was to use an OMEC laser particle size analyzer to prepare a test sample by adding the material to a conventional dispersion (deionized water + surfactant) in the art. The test results are shown in Table 2 below.

[0065] Table 2

[0066] D00(μm) D10(μm) D50(μm) D90(μm) D100(μm) Example 1 0.617 2.453 11.810 25.451 53.842 Comparative Example 1 0.898 4.241 13.810 32.598 499.723 Comparative Example 2 0.702 3.643 11.643 29.844 50.372

[0067] Results analysis: In Example 1, the particle size of the finely ground material is D50≤12um, D100<60um, which is similar to the particle size of the finely ground production material in Comparative Example 2, and has good processability; while in Comparative Example 1, the naturally dried material has a larger particle size overall due to insufficient grinding, which does not meet the particle size requirements. At the same time, since the wall-adhering material has not been effectively ground, the material D100 is too large.

[0068] (3) Scanning electron microscopy observation

[0069] The finely ground materials of Example 1 and Comparative Example 1 were observed using a scanning electron microscope.

[0070] Figure 2 is a scanning electron microscope image of the material after fine grinding in Example 1, Figure 3 This is a scanning electron microscope image of the material after fine grinding in Example 1. By comparing the two, it can be seen that the overall material size in Example 1 is smaller and has a better grinding effect.

[0071] The material yields after fine grinding of Example 1 and Comparative Example 1 were calculated; the material yield of Example 1 was 76%, and the material yield of Comparative Example 1 was 59%. This is because in Comparative Example 1, the natural drying did not fully achieve moisture control, so the material was easily adhered to the wall and lost in the equipment, and the material yield was significantly reduced.

[0072] Test Example 2: Electrical Performance Test

[0073] Prepare finished graphite products using the materials obtained in Example 1 and Comparative Example 2;

[0074] Graphite product preparation process: the above materials are further subjected to pre-carbonization and graphitization; Pre-carbonization: the materials are loaded into a quartz crucible, isolated from the air, and sent into a track kiln to be heated to 1200-1400℃ for a certain period of time before being sent out. Graphitization: the loading crucible is placed in the Acheson graphitization furnace, and the electricity is sent to 3000 degrees for a certain period of time before being taken out.

[0075] For graphite products, cells are assembled and their electrical properties are tested.

[0076] The general process for preparing negative electrode sheets of lithium batteries from negative electrode materials is as follows: the graphite negative electrode materials obtained in Example 1 and Comparative Example 2 are formulated into a slurry in a mass ratio of graphite negative electrode material: carbon black conductive agent SP: binder (CMC+SBR) = 96.5:2:1.5, and mechanically stirred at room temperature for 30 minutes at a stirring speed of 2000 r / min. The prepared slurry is coated on a current collector, dried in an oven at 100°C for 30 minutes, and then dried in a vacuum drying oven at 120°C for 8 hours to obtain the prepared electrode sheet.

[0077] The general process of half-cell assembly and testing is as follows: prepare the electrode pieces and assemble them into lithium-ion button cells for constant current charge and discharge tests. 6 Dissolved in a mixed solvent of EC / DEC / EMC=2:3:1 at a concentration of 1 mol / L to form a non-aqueous electrolyte, where EC is ethylene carbonate, EMC is methyl ethyl carbonate, and DEC is diethyl carbonate. Assembled into batteries in a glove box for electrochemical performance testing. The first charge and discharge was performed under 1C / 1C conditions to test the gram capacity and first cycle efficiency of the material.

[0078] The battery test results of Example 1 and Comparative Example 2 are shown in Table 3 below:

[0079] Table 3

[0080] Battery first coulombic efficiency (%) Negative electrode capacity (mAh / g) Example 1 93.1 345.7 Comparative Example 2 92.8 345.2

[0081] Analysis of results: It can be seen from Example 1 and Comparative Example 2 that the performance of the battery prepared from the kilogram-level experimental material through the rapid drying method is basically the same as that of the final finished material of the production line. This proves that the method of the present application can be effectively used for the rapid drying and screening verification of kilogram-level experimental materials, which is economical and efficient and saves manpower time.

[0082] In summary, the rapid drying method of the present application is a rapid heatless drying method with wide applicability, which is not restricted by the site environment. It can effectively and quickly process and dry kilogram-level raw coke, and the effect is equivalent to that of production line materials. It is a fast and economical small batch material processing method.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A method for rapid drying of raw coke, comprising the following steps: (1) roughly crushing the raw coke to obtain material A; (2) fully stirring and mixing the obtained material A and activated alumina particles having a size of 10 mm to 15 mm to obtain a mixed material B; (3) After the mixed material B is allowed to stand, it is screened with a 2.5-5 mesh coarse screen. The material on the screen is a large particle water-absorbing alumina desiccant, and the material under the screen is the raw coke material C after rapid drying, and its moisture content is not higher than 5%; (4) The raw coke material C after rapid drying is subjected to a fine grinding process to control the particle size of the finely ground material to D50 of 11-12 μm and D100 of no more than 60 μm.

2. The method according to claim 1, wherein: In step (1), the raw coke is selected from one of petroleum coke and pitch coke, the petroleum coke is selected from needle coke, sponge coke or shot coke, and The mass of the raw coke A is less than 100 kg.

3. The method according to claim 1, wherein: In step (1), the raw coke is roughly crushed using a kilogram-class jaw crusher, preferably to a size of less than 10 mm.

4. The method according to claim 1, wherein: In step (2), the mass of the activated alumina particles is 5-20% of the mass of the material A.

5. The method according to claim 1, wherein: In step (3), the mixed material B is allowed to stand for 30 min to 3 h.

6. The method according to claim 1, wherein: In step (4), the collected material C is finely ground to obtain a material yield of more than 70%, wherein the yield is calculated as follows: material yield = mass of first-stage classified material in the experimental mill / total feed mass.

7. A graphite negative electrode material, comprising at least the dried raw coke obtained by the method according to any one of claims 1 to 6.

8. A graphite negative electrode, prepared from the graphite negative electrode material according to claim 7.

9. A lithium ion battery comprising at least the graphite negative electrode according to claim 8.

10. The lithium ion battery according to claim 9, wherein: The negative electrode capacity of the lithium ion battery is not less than 345 mAh / g, and the first coulomb efficiency is not less than 92%.

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