阅读说明：本技术 一种适用于锂离子电池负极原料的各向同性焦及其制备方法 (isotropic cokes suitable for lithium ion battery cathode raw materials and preparation method thereof ) 是由 石磊 舒平 皮涛 王志勇 黄越华 邵浩明 于 2019-10-15 设计创作，主要内容包括：本发明公开了一种适用于锂离子电池负极原料的各向同性焦,其特征在于,所述各相同性焦的光学结构为镶嵌结构与小域结构共存的状态,其中小域结构占比≥40%。本发明以低温煤焦油为原料,通过超级离心机进行离心,再将离心后的低温煤焦油送入到闪蒸器中进行闪蒸,得到闪蒸料；然后将闪蒸料在惰性气氛下进行焦化处理,制得各向同性焦。本发明制备的各向同性焦压实可达1.45~1.50g/cc,容量为335~340mAh/g,能够满足6C充电恒流比≥80%。(The invention discloses isotropic cokes suitable for a lithium ion battery cathode raw material, which are characterized in that the optical structures of the isotropic cokes are in a state that an embedded structure and a small domain structure coexist, wherein the small domain structure accounts for more than or equal to 40%.)

1, isotropic cokes suitable for lithium ion battery cathode raw materials, and is characterized in that the optical structure of each isotropic coke is in a state of coexistence of a mosaic structure and a small domain structure, wherein the small domain structure accounts for more than or equal to 40%.

2, A preparation method of isotropic coke suitable for lithium ion battery cathode raw materials, which is characterized by comprising the following steps:

s1, taking low-temperature coal tar as a raw material, centrifuging the low-temperature coal tar through a super centrifuge, and separating fine particles in the low-temperature coal tar from the coal tar to ensure that the QI content of the low-temperature coal tar is lower than 0.1%;

s2, heating the centrifuged low-temperature coal tar to 120-180 ℃, and then sending the coal tar into a flash evaporator for flash evaporation, wherein the temperature is controlled to be 450-500 ℃, and the flash evaporation is carried out for 5-10S, so as to obtain a flash evaporation material;

and S3, coking the flash material in an inert atmosphere, wherein the coking temperature rise speed is 2-5 ℃/min, the highest temperature is controlled at 480-500 ℃, so that a coking material is obtained, and then, naturally cooling the coking material in the inert atmosphere, so that the isotropic coke is obtained.

3. The method for preparing isotropic cokes suitable for the lithium ion battery negative electrode raw material according to claim 2, wherein in step S1, the low-temperature coal tar is prepared by dry distillation of bituminous coal at 400-450 ℃.

4. The method for preparing kinds of isotropic coke suitable for lithium ion battery negative electrode raw materials according to claim 3, wherein in step S1, the low temperature coal tar mainly comprises phenols and hydrocarbons, wherein the mass ratio of the phenols is 60-70%, the mass ratio of the hydrocarbons is 20-30%, and the balance is heterocyclic-containing hydrocarbons.

5. The method for preparing isotropic cokes suitable for negative electrode raw materials of lithium ion batteries according to claim 4, wherein in step S1, Shanxi produced low temperature coal tar is adopted as the low temperature coal tar, the mass ratio of phenols in the low temperature coal tar is 62%, the mass ratio of hydrocarbons is 23%, and the balance is hydrocarbons containing heterocycles.

6. The method for preparing isotropic cokes suitable for negative electrode raw materials of lithium ion batteries according to claim 2, wherein in step S2, the low-temperature coal tar is heated to 150 ℃ and then sent to a vacuum wiped film flash evaporator for flash evaporation.

7. The method for preparing isotropic cokes suitable for use as anode raw materials for lithium ion batteries according to claim 2, wherein in step S3, the inert atmosphere comprises argon, nitrogen and mixed gas thereof.

8. The method for preparing kinds of isotropic coke suitable for the lithium ion battery negative electrode raw material according to claim 2, wherein in step S3, the flash material is subjected to heat preservation for 5-10 hours at a coking temperature of 480-500 ℃.

Technical Field

The invention relates to a preparation method of a lithium ion battery cathode raw material, in particular to kinds of isotropic coke suitable for the lithium ion battery cathode raw material and a preparation method thereof.

Background

The isotropic coke is kinds of coke substances with isotropic or mosaic optical structures, can be used in the fields of electrodes for electric discharge machining, mechanical sealing materials under high temperature and high pressure, airplane brake sheets, rocket nozzle throat linings and the like, and is widely used as a negative electrode raw material of a lithium ion battery by along with the rapid charging requirement of the lithium ion battery in recent years.

The preparation method of the isotropic coke comprises the following steps:

(1) the air oxidation method takes coal tar, residual oil or asphalt materials thereof as raw materials, and the components in the raw materials are crosslinked through oxidation, so that an isotropic structure is formed in the later carbonization process; the number of patents is large, and typical patents include [ CN1306070 ], [ US5066385 ] and the like.

(2) The catalytic method is characterized in that the pyrolysis and polymerization reactions of the heavy aromatic raw materials are remarkably accelerated by adding a catalyst, and the mesophase globules are solidified to form a mosaic structure in short time; such patents include US5160602, cn201410561714. x.

(3) The mesocarbon microbeads are shaped and baked to prepare the isotropic coke.

(4) The direct coking method adopts proper raw materials and is directly prepared by a coking process, and the method has relatively high requirements on the raw materials.

The isotropic coke obtained by the method is designed and developed aiming at the fields of nuclear graphite, mechanical sealing materials and the like, and is used for lithium ion battery cathode raw materials, the energy density of the obtained product hardly meets the requirements of customers, and at present, the processing technology of the isotropic coke specially used for the lithium ion battery cathode raw materials is fresh in China.

Disclosure of Invention

The invention aims to solve the problems in the background art, and provides kinds of isotropic coke suitable for a lithium ion battery negative electrode raw material and a preparation method thereof.

In order to achieve the purpose, the invention adopts the following technical scheme:

isotropic cokes suitable for lithium ion battery cathode raw materials, wherein the optical structure of each isotropic coke is in a state of coexistence of an embedded structure and a small domain structure, the embedded structure means that the size of a same-color region in a polarized light picture is less than or equal to 10 micrometers, the small domain structure means that the size of the same-color region in the polarized light picture is between 10 and 30 micrometers, and the small domain structure accounts for more than or equal to 40%.

A preparation method of isotropic coke suitable for a lithium ion battery cathode raw material, which is characterized by comprising the following steps:

s1, taking low-temperature coal tar as a raw material, centrifuging through a super centrifuge, and separating fine particles in the low-temperature coal tar from the coal tar, wherein the fine particles mainly refer to primary QI in the coal tar and comprise coal dust, metal impurities, free carbon and the like; after centrifugation, the QI content of the low-temperature coal tar is lower than 0.1%;

s2, heating the centrifuged low-temperature coal tar to 120-180 ℃, and then sending the coal tar into a flash evaporator for flash evaporation, wherein the temperature is controlled to be 450-500 ℃, and the flash evaporation is carried out for 5-10S, so as to obtain a flash evaporation material;

and S3, coking the flash material in an inert atmosphere, wherein the coking temperature rise speed is 2-5 ℃/min, the highest temperature is controlled at 480-500 ℃, so that a coking material is obtained, and then, naturally cooling the coking material in the inert atmosphere, so that the isotropic coke is obtained.

Preferably, in step S1, the low-temperature coal tar is prepared by dry distillation of bituminous coal at 400 to 450 ℃.

Preferably, in step S1, the low-temperature coal tar mainly contains phenols and hydrocarbons, wherein the mass ratio of the phenols is 60-70%, the mass ratio of the hydrocarbons is 20-30%, and the balance is heterocyclic-containing hydrocarbons.

Preferably, in step S1, the low-temperature coal tar is produced in shanxi province, the mass ratio of phenols in the low-temperature coal tar is 62%, the mass ratio of hydrocarbons is 23%, and the rest is hydrocarbons containing heterocycles.

Preferably, in step S2, the low temperature coal tar is heated to 150 ℃, and then sent to a vacuum wiped film flash evaporator for flash evaporation.

Preferably, in step S3, the inert atmosphere includes, but is not limited to, argon, nitrogen, and other gases and mixtures thereof that do not participate in the chemical reaction during the coking process.

Preferably, in the step S3, the flash material is subjected to heat preservation for 5-10 hours at the coking temperature of 480-500 ℃.

The invention has the following beneficial effects:

the traditional preparation process of the isotropic coke mainly comprises the following steps: air oxidation, catalysis, carbon sphere formation coking, and direct coking of suitable raw materials. The isotropic coke prepared by the methods is of a fine mosaic structure, the graphitization degree of the obtained product is low after graphitization, and the product is used as a lithium ion battery cathode material, and the compaction and the capacity of the product are difficult to meet the requirements.

The invention solves the problem that kinds of isotropic coke with mosaic structures and small domain structures as main bodies are developed, wherein the small domain structures account for more than or equal to 40 percent of the isotropic coke, after graphitization treatment, the compaction can reach 1.45-1.50 g/cc, the capacity is 335-340 mAh/g, and the 6C charging constant current ratio can be more than or equal to 80 percent.

The method is characterized in that a raw material is selected, the raw material belongs to low-temperature coal tar and is prepared by dry distillation of bituminous coal at 400-450 ℃, the main components of the low-temperature coal tar are phenols and hydrocarbons, wherein the mass ratio of the phenols is 60-70%, the mass ratio of the hydrocarbons is 20-30%, and the balance is mainly heterocyclic hydrocarbons.

Another innovation in the technology is the processing technology matched with the raw materials, including centrifugal separation, flash evaporation and coking, wherein the centrifugal separation is used for reducing QI in the tar to below 0.1% and aims to avoid interference of the QI on limited fusion of hydrocarbon substances, the flash evaporation is realized by quickly raising the temperature to ensure that the coal tar is only subjected to obvious cross-linking reaction and the structure of the coal tar is solidified before phenols and heteroatom-containing molecules reach molecular rearrangement to form a mosaic structure, and the temperature raising process in the coking process is relatively slow to ensure that uncured hydrocarbons still existing in flash evaporation products form a carbonaceous intermediate phase in a limited space and are fused into a small-domain structure.

The innovation point of the invention is to provide kinds of isotropic cokes with small domains and mosaic structures, wherein the small domain structure accounts for more than or equal to 40%, after the isotropic cokes are graphitized, the electrochemical performance of the isotropic cokes is tested, the result shows that the compaction can reach 1.45-1.50 g/cc, the capacity is 335-340 mAh/g, and the 6C charging constant current ratio can be more than or equal to 80%.

Drawings

FIG. 1 is an optical structural diagram of an isotropic focus prepared in example 1.

FIG. 2 is an optical structural diagram of an isotropic focus prepared in example 2.

FIG. 3 is an optical structural diagram of an isotropic focus prepared in example 3.

FIG. 4 is an optical structural diagram of an isotropic focus prepared in example 4.

FIG. 5 is an optical structural diagram of an isotropic focus prepared in example 5.

FIG. 6 is an optical structural diagram of an isotropic focus prepared in example 6.

Fig. 7 is an optical structural view of the isotropic focus prepared in comparative example 1.

Fig. 8 is an optical structural view of the isotropic focus prepared in comparative example 2.

Detailed Description

The technical solutions in the embodiments of the present invention are described clearly and completely below, and it is obvious that the described embodiments are only some embodiments, not all embodiments, of the present invention .