阅读说明：本技术 一种中间相沥青边接触式包覆石墨的工艺 (Process for coating graphite by mesophase pitches in edge contact manner ) 是由 石磊 徐帅 邵浩明 王志勇 皮涛 黄越华 于 2019-10-15 设计创作，主要内容包括：一种中间相沥青边接触式包覆石墨的工艺。本发明公开了本发明提供了一种中间相沥青碳包覆石墨的工艺,以生焦石墨化所得人造石墨为被包覆材料,以固含量为1.2~2.4%聚四氟乙烯乳液为改性剂。首先,采用聚四氟乙烯乳液对人造石墨进行改性,所得中间物为改性石墨,然后,通过固相法将沥青碳包覆在改性石墨表面,得到沥青碳六角网面垂直于石墨外表面的包覆材料。本发明方法制备的中间相沥青碳包覆石墨材料的快充性能得到显著提高。(intermediate phase asphalt side contact type graphite coating processes, the invention discloses a intermediate phase asphalt carbon coated graphite process, artificial graphite obtained by raw coke graphitization is used as a coated material, polytetrafluoroethylene emulsion with the solid content of 1.2-2.4% is used as a modifier, firstly, the artificial graphite is modified by the polytetrafluoroethylene emulsion, the obtained intermediate is modified graphite, and then, asphalt carbon is coated on the surface of the modified graphite by a solid phase method to obtain a coating material with an asphalt carbon hexagonal net surface vertical to the outer surface of the graphite.)

The process for coating graphite by using mesophase pitches in an edge contact manner is characterized by comprising the following steps of:

s1, adding artificial graphite into a kneading pot, adding polytetrafluoroethylene emulsion into the artificial graphite according to the proportion that 0.5-1.5L of polytetrafluoroethylene emulsion is added into each kilogram of artificial graphite, kneading, introducing inert atmosphere, heating the kneading pot to 250-350 ℃, continuing kneading, stopping kneading after the solvent is dried, and naturally cooling to obtain the modified graphite material;

s2, mixing the modified graphite material and the mesophase pitch, uniformly mixing, placing in a carbonization furnace protected by inert atmosphere, heating to 400-450 ℃ at the speed of 0.5-1.5 ℃/min, preserving heat for 1-3 h, heating to 900-1350 ℃ at the speed of 2-5 ℃/min, preserving heat for 0.5-1 h, and naturally cooling to obtain the coated graphite cathode material.

2. The process for middle-phase asphalt edge-contact coated graphites according to claim 1, characterized in that, in step S1, the artificial graphites including single-particle and double-granulation artificial graphites are prepared from green coke materials.

3. The process for middle-phase asphaltic edge-contact graphite coating according to claim 1, wherein in step S1, the PTFE emulsion is analytically pure with a solid content of 1.2-2.4%, and is prepared by diluting a commercial PTFE emulsion with a solid content of 60%.

4. The process for edge-contact graphite cladding with mesophase pitch as claimed in claim 1, wherein in step S1, the inert gas atmosphere comprises nitrogen, argon, or a mixture of nitrogen and argon.

5. The process for edge-contact graphite coating of kinds of mesophase pitches according to claim 1, wherein the mass ratio of the modified graphite material to the mesophase pitch in step S2 is 100 (0.5-2).

6. The process for coating graphite with kinds of mesophase pitches in a side-contact manner according to claim 1, wherein in step S2, the content of quinoline insoluble substances in the mesophase pitches is not less than 80%, the softening point of the mesophase pitches is 250-300 ℃, and the coking value of the mesophase pitches is higher than 80%.

7. The process for edge-contact coating of graphite with kinds of mesophase pitches according to claim 1, wherein in step S2, quinoline insolubles in the mesophase pitches are 86%, the softening point of the mesophase pitches is 252 ℃, and the coking value of the mesophase pitches is 84.2%.

Technical Field

The invention relates to an asphalt coating process of graphite materials for lithium ion batteries, in particular to a process for coating graphite powder in an edge contact manner by mesophase asphalt.

Background

In recent years, with the rapid development of new energy automobiles, the quick-charging type graphite cathode material gradually becomes the focus of attention of the lithium ion battery cathode industry, and in order to improve the quick-charging performance of the graphite cathode, various asphalt raw materials and corresponding coating and carbonization processes are widely adopted by .

However, in many asphalt carbon coating processes, there are no documents and patents on studies for artificially controlling the orientation arrangement of asphalt carbon crystallites. Although the asphalt carbon with regular arrangement can be spontaneously obtained by adopting a chemical vapor deposition method, the carbon hexagonal net surface of the asphalt carbon is mostly parallel to the outer surface of graphite particles, and the structure is not beneficial to the rapid insertion and extraction of lithium ions. If the hexagonal net surface of the pitch carbon can be manually controlled to be vertical to the outer surface of the graphite through a new coating process, a graphite cathode with more excellent quick charging performance is expected to be obtained.

The method takes mesophase pitch with high content of polycyclic aromatic hydrocarbon as a raw material, and achieves the purpose of coating the graphite surface by the hexagonal net surface of pitch carbon in a side contact manner through a two-step coating process.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides processes for the mesophase pitch edge-contact type graphite coating.

The invention is realized by the following technical scheme:

Process for coating graphite by mesophase pitch in edge contact mode, which is characterized by comprising the following steps:

s1, adding artificial graphite into a kneading pot, adding polytetrafluoroethylene emulsion into the artificial graphite according to the proportion that 0.5-1.5L of polytetrafluoroethylene emulsion is added into each kilogram of artificial graphite, kneading, introducing inert atmosphere, heating the kneading pot to 250-350 ℃, continuing kneading, stopping kneading after the solvent is dried, and naturally cooling to obtain the modified graphite material;

s2, mixing the modified graphite material and the mesophase pitch, uniformly mixing, placing in a carbonization furnace protected by inert atmosphere, heating to 400-450 ℃ at the speed of 0.5-1.5 ℃/min, preserving heat for 1-3 h, heating to 900-1350 ℃ at the speed of 2-5 ℃/min, preserving heat for 0.5-1 h, and naturally cooling to obtain the coated graphite cathode material.

Preferably, in step S1, the artificial graphite includes single-particle and double-particle artificial graphite, and is prepared from a green coke material.

Preferably, in step S1, the polytetrafluoroethylene emulsion is analytically pure, has a solid content of 1.2-2.4%, and is prepared by diluting a commercially available polytetrafluoroethylene emulsion having a solid content of 60%.

Preferably, in step S1, the inert atmosphere includes, but is not limited to, such as nitrogen, argon, etc., inert gas that does not chemically react with polytetrafluoroethylene and graphite within the range of 250 to 350 ℃, and a mixture thereof.

Preferably, in step S2, the mass ratio of the modified graphite material to the mesophase pitch is 100: (0.5-2).

Preferably, in step S2, the quinoline insoluble content in the mesophase pitch is not less than 80%, the softening point is 250-300 ℃, and the coking value is higher than 80%.

Preferably, in step S2, the quinoline insolubles in the mesophase pitch are 86%, the softening point of the mesophase pitch is 252 ℃, and the coking value of the mesophase pitch is 84.2%.

Preferably, in step S2, the inert atmosphere in the carbonization furnace includes, but is not limited to, nitrogen, argon, and the like, which do not chemically react with the asphalt, polytetrafluoroethylene, and graphite in the high temperature region, and a mixture thereof.

Compared with the prior art, the invention has the following technical effects:

the invention provides a process for coating graphite with kinds of asphalt carbon, which artificially controls the arrangement orientation of hexagonal mesh surfaces in the asphalt carbon for the first time, so that the quick-filling performance improvement effect on the graphite is more obvious.

In order to achieve the aim, the invention takes mesophase pitch as a coating agent, takes artificial graphite obtained by graphitizing raw coke as a coated material, and takes polytetrafluoroethylene emulsion with the solid content of 1.2-2.4% as a modifier. Firstly, modifying artificial graphite by adopting polytetrafluoroethylene emulsion, wherein the obtained intermediate is modified graphite, and then coating asphalt carbon on the surface of the modified graphite by a solid phase method to obtain a coating material with an asphalt carbon hexagonal net surface vertical to the outer surface of the graphite.

As shown in figures 1 and 2, the arrangement state of the carbonaceous intermediate phase molecules on the surfaces of different solid materials is different from , the carbonaceous intermediate phase molecules on the graphite surface are arranged in a surface contact mode as shown in figure 1, and the carbonaceous intermediate phase molecules on the polytetrafluoroethylene surface are arranged in a side contact mode as shown in figure 2.

The mesophase pitch belongs to a carbonaceous mesophase of a somatic mesophase class, so if the graphite surface is modified by polytetrafluoroethylene firstly and then is coated with the mesophase pitch, the hexagonal mesh surface of the obtained pitch carbon is coated on the graphite surface in a side contact manner, the polytetrafluoroethylene can be converted into a small amount of hard carbon to be distributed between the pitch carbon and the graphite in the carbonization process, and the hard carbon can also promote the improvement of the quick filling performance of the graphite.

When a constant-current-constant-voltage charging experiment is carried out under the condition of 3C, the constant-current capacity percentage of the asphalt carbon coated sample is 1-2% higher than that of an uncoated sample, the polytetrafluoroethylene pyrolysis coated sample is 3-6% higher than that of the uncoated sample, the sample related by the invention is 8-12% higher than that of the uncoated sample, and the quick charging performance of the material is obviously improved.

Drawings

Fig. 1 is a schematic diagram showing the arrangement of carbonaceous mesophase molecules on the surface of graphite in a surface contact manner.

FIG. 2 is a schematic diagram of the side-contact arrangement of carbonaceous mesophase molecules on the surface of polytetrafluoroethylene.

Detailed Description

The invention is further illustrated in with reference to specific examples.