阅读说明：本技术 一种二次颗粒人造石墨材料及其制备方法 (Secondary particle artificial graphite material and preparation method thereof ) 是由 庞成志 许晓落 安静 刘畅 于 2021-08-27 设计创作，主要内容包括：本发明涉及一种二次颗粒人造石墨材料及其制备方法,采用本发明的方法制备二次颗粒人造石墨材料时间大幅缩短,使用传统反应釜造粒需要12-24h,本发明采用液相融合造粒方式仅仅需要2h即可达到常规反应釜的造粒产量；本发明的方法制备的二次颗粒人造石墨材料造粒均匀,单个颗粒内部粘结性好,不存在假性粘结,成品颗粒美观细粉少,大颗粒少,振实高,浆料粘度适中,不易于沉降；本发明制得的二次颗粒人造石墨材料可逆容量损失少,容量可达355mAh/g,与电解液兼容性好,首效可达95％以上,粉体压实高,循环上比固相造粒优异并且稳定性好,内阻上表现优异,可降低5％-30％。(The invention relates to a secondary particle artificial graphite material and a preparation method thereof, the time for preparing the secondary particle artificial graphite material by adopting the method is greatly shortened, the granulation of a traditional reaction kettle needs 12-24 hours, and the granulation yield of the conventional reaction kettle can be reached only 2 hours by adopting a liquid phase fusion granulation mode; the artificial graphite material with secondary particles prepared by the method is uniform in granulation, the inside of a single particle is good in cohesiveness, false cohesiveness does not exist, finished particles are attractive, fine powder is few, large particles are few, tap is high, slurry viscosity is moderate, and sedimentation is not easy to occur; the prepared secondary particle artificial graphite material has the advantages of less reversible capacity loss, capacity of 355mAh/g, good compatibility with electrolyte, first effect of over 95 percent, high powder compaction, excellent circulation performance compared with solid-phase granulation, good stability, excellent internal resistance performance and capability of reducing 5 to 30 percent.)

1. A preparation method of a secondary particle artificial graphite material is characterized by comprising the following steps:

(1) crushing the raw material coke, and then grading to remove fine powder;

(2) carrying out medium-temperature heat treatment on the classified powder to obtain a material A;

(3) mixing 100 parts of the material A and 5-30 parts of a liquid phase coating agent at a high speed according to the parts by weight to obtain a material B;

(4) carrying out medium-temperature heat treatment on the material B, cooling to room temperature, and then crushing to obtain a material C;

(5) and carrying out high-temperature heat treatment on the material C, and grading to obtain the secondary particle artificial graphite material.

2. The method for preparing a secondary particle artificial graphite material according to claim 1, wherein the raw coke in the step (1) is one or more of petroleum coke, needle coke and pitch coke.

3. The method for preparing a secondary particle artificial graphite material as claimed in claim 1, wherein the temperature of the intermediate-temperature heat treatment in the step (2) is 600-1500 ℃.

4. The method for preparing a secondary particle artificial graphite material according to claim 1, wherein the linear velocity of the high-speed mixing in the step (3) is 5 to 30m/s, and the mixing time is 3 to 60 min.

5. The method for preparing a secondary particle artificial graphite material according to claim 1, wherein the liquid phase coating agent in step (3) is a stripping byproduct of ethylene cracking tar, and preferably, the liquid phase coating agent is one or more of liquid heterocyclic aromatic hydrocarbon, ketone, hydrocarbon, resin, asphalt and heavy oil.

6. The method as claimed in claim 1 or 5, wherein the viscosity of the liquid phase coating agent is 100-2000mm²And/s, the carbon residue value is 5-30%.

7. The method for preparing a secondary particle artificial graphite material as claimed in claim 1, wherein the temperature of the medium temperature heat treatment in step (4) is 900-1300 ℃, and the crushing is performed by a pin mill at a frequency of 3-30 Hz.

8. The method as claimed in claim 1, wherein the temperature of the high temperature heat treatment in step (5) is 2200-.

9. A secondary particulate synthetic graphite material produced by the method of any one of claims 1 to 8, wherein the secondary particulate synthetic graphite material has a particle size distribution KThe value is 0.9-2.0, and the tap is 1.0-1.30g/cm³(ii) a The specific surface area is 0.7-1.5g/m²。

Technical Field

The invention belongs to the technical field of lithium battery cathode materials, and particularly relates to a secondary particle artificial graphite material and a preparation method thereof.

Background

In the last decade, the technology and material technology of the lithium ion battery are continuously optimized, the plan and requirements of the state on the new energy industry are also improved, the energy density and the safety of the lithium ion power battery become important bottlenecks, and the negative electrode material of the lithium ion power battery mainly adopts artificial graphite, so that the improvement space of the energy density is narrow, but higher requirements on the quick charging performance are provided.

The method for improving the quick charging capacity of the artificial graphite mainly aims at reducing the particle size of particles, surface coating modification, secondary particle structure design and the like, but the method cannot achieve excellent balanced performance in the aspects of energy density, compaction density, quick charging, high and low temperature, expansion life and the like. The secondary particle granulation process is an important process for improving the performance of the artificial graphite, and can effectively improve the quick filling performance, reduce the expansion and prolong the cycle life. However, the conventional granulation process adopts solid-phase asphalt and the like as binders, so that pseudo-binding is realized, the yield is low, the process cost is high, and the efficiency is low; the granulation of the secondary particles is not uniform, the particle distribution is difficult to control, the fine powder is difficult to control, the tap ratio is high, the processing of the application end is difficult and the like, thus retarding the improvement of the process and the performance of the secondary particle artificial graphite.

The present invention has been made in view of the above circumstances.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a secondary particle artificial graphite material and a preparation method thereof.

The invention provides a preparation method of a secondary particle artificial graphite material, which comprises the following steps:

(1) crushing the raw material coke, and then grading to remove fine powder;

(2) carrying out medium-temperature heat treatment on the classified powder to obtain a material A;

(3) mixing 100 parts of the material A and 5-30 parts of a liquid phase coating agent at a high speed according to the parts by weight to obtain a material B;

(4) carrying out medium-temperature heat treatment on the material B, cooling to room temperature, and then crushing to obtain a material C;

(5) and carrying out high-temperature heat treatment on the material C, and grading to obtain the secondary particle artificial graphite material.

Further, the raw coke in the step (1) is one or more of petroleum coke, needle coke and pitch coke.

In the step (1), one or more of a grading impact mill, a cyclone separator and an internal classifier are used for grading and are operated in series, and the process mainly aims to remove more fine powder and grind off edges and corners of particles to ensure that the particles have more round shapes or do not pass through the process.

Further, the temperature of the medium-temperature heat treatment in the step (2) is 600-; the main purpose of adopting the steps is to remove most of volatile components in the material before the next liquid phase granulation, reduce the specific surface of the material, and improve the tap density of the material, so that the material and the liquid phase coating agent can be better soaked and coated.

In the step (2), one or more of a roller kiln, a pushed slab kiln, a pot furnace, a rotary furnace and the like can be adopted for heating, the gas atmosphere can be nitrogen, inert gas or air, and the heating mode can be electric heating or thermal heating.

The key point of the step (2) is to carry out heat treatment on the material, the heat treatment mode and equipment are not limited, and the surface of the material can be better protected and is not easy to damage under nitrogen and inert atmosphere; if the surface of the material is damaged in the air atmosphere, but a part of the material is repaired again in the subsequent high-temperature heat treatment, and the influence is acceptable; in addition, the cost is lower by using an air atmosphere heat treatment mode, the equipment type is simple, and the operation is easy;

further, the linear speed of the high-speed mixing in the step (3) is 5-30m/s, and the mixing time is 3-60 min. The high-speed mixing mode is adopted for mixing more uniformly, so that the liquid phase coating agent and the particles after heat treatment are ensured to be soaked and absorbed more compactly, the appearance of the surfaces of the particles is improved again, and the bonding between the particles is more regular and compact.

The high-speed mixing is carried out in a stirring kettle, and the stirring kettle comprises mixing equipment suitable for solid-liquid phase mixing, such as a mechanical fusion machine, a high-speed VC machine and the like.

Further, the liquid phase coating agent in the step (3) is ethylene cracking tar stripping by-product.

Further, the liquid phase coating agent is one or more of liquid heterocyclic aromatic hydrocarbon, ketone, hydrocarbon, resin, asphalt and heavy oil.

Further, the viscosity of the liquid phase coating agent is 100-2000mm²And/s, the carbon residue value is 5-30%.

Further, the temperature of the medium temperature heat treatment in the step (4) is 900-. The purpose of the step is that the liquid phase coating agent among the particles forms carbon residue after heat treatment, the particles which are bonded together are bonded and solidified, solid-liquid phase bonding after mixing is completely changed into solid-solid phase embedding bonding, and the particles which are successfully bonded together form secondary particles.

The crushing adopts a pin type mill, the purpose of crushing materials is achieved through collision of cylindrical rods, the damage to the formed secondary particle structure is reduced, the frequency is 3-30Hz, wherein the medium-temperature heat treatment is carried out by one or more of a roller kiln, a pushed slab kiln, a box furnace and the like, and the gas atmosphere can be inert gases such as nitrogen and the like.

Further, the temperature of the high-temperature heat treatment in the step (5) is 2200-.

The high-temperature heat treatment adopts a box furnace or an Acheson furnace.

The second purpose of the invention is to provide a secondary particle artificial graphite material prepared by the method, wherein the particle size distribution K value of the secondary particle artificial graphite material is 0.9-2.0, and the tap is 1.0-1.30g/cm³(ii) a The specific surface area is 0.7-1.5g/m²。

Compared with the prior art, the invention has the beneficial effects that:

(1) the method for preparing the secondary particle artificial graphite material greatly shortens the time, the granulation of the traditional reaction kettle needs 12-24 hours, and the granulation yield of the conventional reaction kettle can be achieved only by 2 hours in a liquid phase fusion granulation mode;

(2) the secondary particle artificial graphite material prepared by the method is uniform in granulation, the inside of a single particle is good in cohesiveness, false cohesiveness does not exist, finished particles are attractive, fine powder is few, large particles are few, the tap is high, the viscosity of slurry is moderate, sedimentation is not easy to occur, and the problem of processability of an application end is solved;

(3) the prepared secondary particle artificial graphite material has the advantages of less reversible capacity loss, capacity up to 355mAh/g, good compatibility with electrolyte, first effect up to more than 95 percent, high powder compaction, and capability of increasing 0.02-0.05g/cm on 2T powder pressure compared with solid phase reaction kettle granulation³The method has the advantages of excellent cycle performance and stability compared with solid-phase granulation, excellent internal resistance performance, and capability of reducing 5-30%.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a graph showing a comparison of powder pressures of a secondary particle artificial graphite material prepared in example 1 of the present invention and a conventional granulation;

FIG. 2 is an SEM image of a secondary particle artificial graphite material prepared by example 1 of the present invention and a conventional granulation process (the left is prepared by the method of example 1, and the right is prepared by the conventional method).

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the examples given herein without any inventive step, are within the scope of the present invention.

Example 1

The preparation method of the secondary particle artificial graphite material of the embodiment comprises the following steps:

(1) 1000kg of petroleum coke is input into a mechanical mill for crushing, and then fine powder is removed by using a graded impact mill;

(2) performing medium-temperature heat treatment on the classified powder by adopting a roller kiln at the temperature of 800 ℃, and introducing nitrogen in the whole process to obtain a material A;

(3) mixing 100 parts by weight of material A and 10 parts by weight of resin liquid phase coating agent at high speed, wherein the viscosity of the liquid phase coating agent is 1000mm²The carbon residue value is 20 percent, the linear velocity is 10m/s, the time is 20min, and a material B is obtained;

(4) performing medium-temperature heat treatment on the material B by adopting a roller kiln at 1100 ℃, introducing nitrogen in the whole process, cooling to room temperature, and crushing by adopting a pin mill at the frequency of 10Hz to obtain a material C;

(5) and (3) feeding the material C into an Acheson furnace for high-temperature heat treatment at the temperature of 3100 ℃, and screening by using a double-layer screen with 150 meshes and 325 meshes after discharging to obtain the secondary particle artificial graphite material.

Example 2

The preparation method of the secondary particle artificial graphite material of the embodiment comprises the following steps:

(1) 1000kg of needle coke is input into a mechanical mill to be crushed, and then a cyclone separator is used for removing fine powder;

(2) performing medium-temperature heat treatment on the classified powder by adopting a tank furnace at the temperature of 600 ℃, and introducing nitrogen in the whole process to obtain a material A;

(3) mixing 100 parts of material A and 5 parts of heterocyclic aromatic hydrocarbon liquid phase coating agent at high speed according to the parts by weight, wherein the viscosity of the liquid phase coating agent is 100mm²The carbon residue value is 5 percent, the linear velocity is 5m/s, and the time is 60min, so that a material B is obtained;

(4) performing medium-temperature heat treatment on the material B by adopting a roller kiln at 900 ℃, introducing nitrogen in the whole process, cooling to room temperature, and crushing by adopting a pin mill at the frequency of 3Hz to obtain a material C;

(5) and (3) feeding the material C into a box furnace for high-temperature heat treatment at the temperature of 2900 ℃, and screening by using a double-layer screen with 150 meshes and 300 meshes after discharging to obtain the secondary particle artificial graphite material.

Example 3

The preparation method of the secondary particle artificial graphite material of the embodiment comprises the following steps:

(1) 1000kg of pitch coke is input into a mechanical mill to be crushed, and then fine powder is removed by using a graded impact mill;

(2) performing medium-temperature heat treatment on the classified powder by adopting a roller kiln at 1500 ℃, and introducing nitrogen in the whole process to obtain a material A;

(3) mixing 100 parts of material A and 30 parts of ketone liquid phase coating agent at high speed according to the parts by weight, wherein the viscosity of the liquid phase coating agent is 2000mm²The carbon residue value is 30 percent, the linear velocity is 30m/s, and the time is 3min, so that a material B is obtained;

(4) performing medium-temperature heat treatment on the material B by adopting a roller kiln at 1300 ℃, introducing nitrogen in the whole process, cooling to room temperature, and crushing by adopting a pin mill at the frequency of 30Hz to obtain a material C;

(5) and (3) feeding the material C into an Acheson furnace for high-temperature heat treatment at 3000 ℃, and screening by using a double-layer 200-mesh + 300-mesh screen after discharging to obtain the secondary particle artificial graphite material.

Comparative example 1

The conventional solid-phase reaction kettle is adopted for granulation to prepare the secondary particle artificial graphite material, which comprises the following specific steps: after fine powder of petroleum coke particles is ground by a mechanical mill and fine powder is ground by an impact type grading mill, solid asphalt is mixed according to a certain proportion and then is granulated in a 400-plus 600 ℃ reaction kettle, and the crushed material is sent into an Acheson graphitizing furnace for heat treatment at 3000 ℃ and then is graded to obtain a comparative product.

Test example 1

The secondary particle artificial graphite materials prepared in examples 1 to 3 and comparative example 1 were subjected to powder data testing, evaluation slurry preparation and button cell battery preparation according to the national standard GB/T243339-2019, and electrochemical performance tests were performed to test their reversible capacity, first coulombic efficiency, cycle, and the like, with the results shown in table 1.

TABLE 1

As can be seen from Table 1, the products with the similar particle size D50 can be obtained by the method of the invention and the method of the comparative example, but the particle size distribution K of the invention is smaller, which shows that the fine powder and the large particles of the products are effectively controlled; the graphite material prepared by the invention has higher tap, which indicates that secondary particle granulation is more compact and compact, and more cavities are formed among solid-phase granulation particles in a comparative example, and the defect of the granulation cavity can generate adverse effect on the processability when powder slurry is produced at the particle application end;

the graphite material ratio table is optimized, the smaller ratio table is beneficial to the fact that the product is not easy to agglomerate at the application end, the independence of particles is kept in application, and a large amount of impurities and other components in the slurry are not adsorbed due to the high specific surface energy of the ratio table, so that a slurry system is not damaged;

the graphite material slurry prepared by the method has lower viscosity, is easy to flow and sieve, and has favorable influence on subsequent processes.

The capacity of the graphite material prepared by the method is close to that of the comparative example, which shows that the method has little influence on the capacity of the graphite material, but the first effect is obviously improved, so that the method has favorable influence.

The improvement of the powder pressure (2T) of the graphite material prepared by the method is obvious, which shows that the liquid-phase granulation of the method obviously improves the secondary particle structure, the particle bonding is more compact, the excessive hole loss and compaction are avoided, the compaction density of the material at the application end can be effectively improved, the internal resistance and the circulation are reflected, the particles are not easy to be bonded and broken artificially, the internal resistance is lower, and the circulation performance is also improved.

In addition, the powder compaction comparison curves of the graphite materials prepared in example 1 and comparative example 1 are shown in fig. 1, and the SEM image is shown in fig. 2. As can be seen from fig. 1 and 2: the graphite material prepared by the method effectively improves the integrity of particle compaction and particle structure bonding, has better appearance, has less sundry particles, false bonding particles and large particles, is not easy to generate fine powder, and can effectively improve the problems of sedimentation, high viscosity, difficult sieving, large particle scratching and the like of the particles in the subsequent slurry preparation. Meanwhile, the equipment system of the method is simple, uniform material mixing and discharging can be completed in 10min, and the defects of high manufacturing cost, complex equipment design and manufacture, large environmental protection pressure, low yield and the like of a reaction kettle mode system are avoided.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.