High-performance artificial graphite and preparation method and application thereof

Abstract

The application discloses high-performance artificial graphite, wherein modified graphene is uniformly distributed in the high-performance artificial graphite; during preparation of the modified graphene, quaternary ammonium salt is grafted to modify graphene oxide, and the modified graphene oxide and nano carbon black are uniformly dispersed in water, and then are left to stand, and solid-liquid separation is performed to obtain the modified graphene. The application further discloses a preparation method of the high-performance artificial graphite, which comprises the following steps: S1, taking raw coke and a binder to granulate to obtain granules 1; the granules 1 are uniformly mixed with tailing fine powder, carbonized, shaped and graphitized to obtain granules 2; S2, the modified graphene is uniformly mixed with a binder after being heated, and then is uniformly mixed with the granules 2 to granulate, carbonized and shaped to obtain the high-performance artificial graphite. The application further discloses application of the high-performance artificial graphite in a lithium ion battery negative electrode. The artificial graphite prepared by the application has high tap density, and when the artificial graphite is used in a lithium ion battery, the artificial graphite has good electrochemical performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of artificial graphite, in particular to a high-performance artificial graphite and a preparation method and application thereof. BACKGROUND

[0002] Artificial graphite is obtained by high-temperature graphitization of carbonaceous raw materials. At present, in the preparation process of artificial graphite, mechanical grinding, shaping and other treatments are generally required, and the intermediate products meeting the requirements are collected after multiple classification. A lot of tailings powder is left after each classification, which has low tap density and small particle size and cannot be used in lithium ion batteries as artificial graphite, and is often treated as waste, which easily causes resource waste. Moreover, the tap density and graphitization degree of the artificial graphite prepared by the existing method are low, which will result in low electrochemical performance when the artificial graphite is used in lithium ion batteries. Moreover, the low tap density will also affect the charging capacity of the material and reduce the production capacity of the graphitization furnace. SUMMARY

[0003] Based on the technical problems existing in the background art, the present application provides a high-performance artificial graphite and a preparation method and application thereof. The artificial graphite prepared by the present application has high tap density and good electrochemical performance when used in lithium ion batteries.

[0004] The present application provides a high-performance artificial graphite, wherein the high-performance artificial graphite uniformly contains modified graphene.

[0005] In the preparation process of the modified graphene, the quaternary ammonium salt grafted modified graphene oxide and nano carbon black are uniformly dispersed in water, and then are left to stand, and are subjected to solid-liquid separation to obtain the modified graphene.

[0006] Preferably, in the preparation process of the modified graphene, the weight ratio of the quaternary ammonium salt grafted modified graphene oxide and the nano carbon black is 1:0.5-0.6; and the standing is performed at room temperature for 1-3h.

[0007] The nano carbon black and the quaternary ammonium salt grafted modified graphene oxide with positive charges are electrostatically assembled in the aqueous solution, so that the nano carbon black is loaded on the surface of the graphene. This structure makes the carbon black uniformly dispersed, and the loading of the carbon black also avoids the agglomeration of the graphene, so that the graphene has good dispersibility with the binder, the particles 2 and other substances.

[0008] The above-mentioned quaternary ammonium salt grafted modified graphene oxide can be hexadecyl trimethyl ammonium bromide modified graphene oxide, dodecyl trimethyl ammonium bromide modified graphene oxide, etc.

[0009] Preferably, the tap density of the high-performance artificial graphite is 0.95-1.01g / cm 3 .

[0010] The application further provides a preparation method of the high-performance artificial graphite.

[0011] S1, granulating raw coke and a binder to obtain granules 1; mixing the granules 1 with tailing fine powder, carbonizing, shaping and graphitizing to obtain granules 2;

[0012] S2, mixing and uniformly heating the modified graphene and the binder, mixing and uniformly heating the modified graphene and the granules 2, carbonizing and shaping to obtain the high-performance artificial graphite.

[0013] The application selects granules 1 and tailing fine powder with appropriate particle sizes, adjusts the ratio of the two, and improves the tap density of the granules 2; then the application selects the modified graphene with good dispersibility and the binder, and the granules 2, and further improves the tap density of the artificial graphite through carbonization.

[0014] Preferably, the modified graphene and the binder are uniformly mixed by heating to 50-60 DEG C.

[0015] The modified graphene and the binder are first uniformly mixed by heating, so that the two are uniformly dispersed; due to the special microstructure of the modified graphite oxide, the modified graphene forms a complex chain structure in the binder, thereby inhibiting the volume expansion during carbonization; the two effects cooperate with each other to improve the density of the artificial graphite and reduce the porosity, thereby further improving the tap density of the artificial graphite.

[0016] In addition, the modified graphene and the granules 2 are bonded by the binder, the modified graphene can be distributed in the gaps of the granules 2 to further improve the tap density; and the modified graphene with the special structure forms an interactive network structure between the artificial graphite particles after carbonization, which can increase the conductivity of the artificial graphite on the one hand and construct transmission channels of lithium ions in the electrode material on the other hand, thereby greatly improving the rate performance and cycle performance of the battery, and promoting the interface bonding of carbon black, graphene, granules 2 and the binder to improve the final graphitization degree and structural integrity.

[0017] Preferably, the raw coke is at least one of needle coke and petroleum coke; and the binder is at least one of coal tar pitch, petroleum pitch, mesophase pitch and modified pitch.

[0018] Preferably, the tailing fine powder is a fine powder remaining after screening and grading during the manufacture of the artificial graphite; and the weight ratio of the granules 1 to the tailing fine powder is 100:3-4.

[0019] Preferably, the tailing fine powder has a tap density of 0.42-0.47 g / cm 3 ; the tailing fine powder has a D 50 of 3-3.5 μm; and the granules 1 have a D 50 of 18-18.5 μm.

[0020] Adjusting the particle size of the granular 1 and the tail fine powder can further improve the tap density of the artificial graphite.

[0021] Preferably, in S1, the weight ratio of the raw coke and the binder is 8-8.5:1.5-2.

[0022] Preferably, in S1, S2, the carbonization temperature is 950-1000℃, and the carbonization time is 10-12h.

[0023] Preferably, in S2, the weight ratio of the modified graphene, the binder and the granular 2 is 0.1-0.15:1:9.

[0024] The tap density of the raw coke is ≤0.6g / cm 3 ; in S1, the graphitization temperature is preferably 2800-3000℃, and the graphitization time is preferably 7-8h.

[0025] The application also provides the use of the high-performance artificial graphite in a lithium ion battery negative electrode.

[0026] Advantages:

[0027] 1. The nanometer carbon black is grafted with a negative charge and a positively charged quaternary ammonium salt to modify the graphene oxide, which realizes electrostatic assembly in an aqueous solution, so that the nanometer carbon black is loaded on the surface of the graphene; this structure makes the carbon black uniformly dispersed, and the loading of the carbon black also avoids the agglomeration of the graphene, so that the graphene has good dispersibility with the binder, the granular 2 and other substances.

[0028] 2. The granular 1 and the tail fine powder with appropriate particle sizes are selected, the ratio of the two is adjusted, the tap density of the granular 2 is improved, then the modified graphene with good dispersibility is selected and combined with the binder and the granular 2, and through carbonization, the tap density of the artificial graphite is further improved; and the use of the tail fine powder can save costs.

[0029] 3. The modified graphene and the binder are heated and uniformly mixed, and due to the special microstructure of the modified graphene oxide, a complex chain structure is formed in the binder, which inhibits the volume expansion during carbonization, and the two effects cooperate with each other to improve the density of the artificial graphite, reduce the porosity, and further improve the tap density of the artificial graphite.

[0030] 4. Modified graphene is bonded to particles 2 with a binder. The modified graphene can be distributed in the gaps between particles 2, further improving the tap density. After carbonization, the modified graphene with a special structure forms an interactive network structure between the artificial graphite particles. On the one hand, it can increase the conductivity of artificial graphite. On the other hand, it can construct lithium-ion transport channels in the electrode material, thereby significantly improving the rate performance and cycle performance of the battery. It can also promote the interfacial bonding of carbon black, graphene, particles 2, and binder, improving the final graphitization degree and structural integrity. Detailed Implementation

[0031] The technical solution of the present invention will be described in detail below through specific embodiments. However, it should be clearly stated that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention.

[0032] Example 1

[0033] A high-performance artificial graphite, wherein modified graphene is uniformly distributed in the high-performance artificial graphite.

[0034] In the preparation of modified graphene, dodecyltrimethylammonium bromide-modified graphene oxide was uniformly dispersed in water, and then an aqueous dispersion of nano-carbon black was added. The mixture was ultrasonically stirred until homogeneous, allowed to stand at room temperature for 3 hours, filtered, washed with water, and dried at 60°C to obtain modified graphene. The weight ratio of dodecyltrimethylammonium bromide-modified graphene oxide to nano-carbon black was 1:0.5.

[0035] The preparation method of the above-mentioned high-performance artificial graphite includes the following steps:

[0036] S1, with a tap density ≤ 0.6 g / cm³ 3 Needle coke and petroleum asphalt were mixed and granulated at a weight ratio of 8:2 to obtain D. 50 Particle 1 has a diameter of 18.0 μm; Particle 1 is mixed with a material with a tap density of 0.42 g / cm³. 3 D 50 The tailings powder with a diameter of 3μm was mixed at a weight ratio of 100:3.5, heated to 950℃ for carbonization for 12h, shaped, and then heated to 3000℃ for graphitization for 7h to obtain particles 2.

[0037] S2. Modified graphene and petroleum asphalt are heated and mixed at 60°C, then mixed with particles 2 and granulated. The mixture is then heated to 950°C and carbonized for 12 hours to obtain high-performance artificial graphite. The weight ratio of modified graphene, petroleum asphalt and particles 2 is 0.1:1:9.

[0038] Example 2

[0039] A high-performance artificial graphite, wherein modified graphene is uniformly distributed in the high-performance artificial graphite.

[0040] In the preparation of modified graphene, hexadecyltrimethylammonium bromide-modified graphene oxide was uniformly dispersed in water, and then an aqueous dispersion of nano-carbon black was added. The mixture was ultrasonically stirred until homogeneous, allowed to stand at room temperature for 1 hour, filtered, washed with water, and dried at 60°C to obtain modified graphene. The weight ratio of hexadecyltrimethylammonium bromide-modified graphene oxide to nano-carbon black was 1:0.6.

[0041] The preparation method of the above-mentioned high-performance artificial graphite includes the following steps:

[0042] S1, with a tap density ≤ 0.6 g / cm³ 3 Needle coke and coal tar pitch were mixed and granulated at a weight ratio of 8.5:1.5 to obtain D. 50 Particle 1 has a diameter of 18.5 μm; Particle 1 is mixed with a tap density of 0.47 g / cm³. 3 D 50 The tailings powder with a thickness of 3.5 μm was mixed at a weight ratio of 100:3, heated to 1000℃ for carbonization for 10 h, shaped, and then heated to 2800℃ for graphitization for 8 h to obtain particles 2.

[0043] S2. Modified graphene and coal tar pitch are heated and mixed at 50°C, then mixed with particles 2 and granulated. The mixture is then heated to 1000°C and carbonized for 10 hours. The resulting material is shaped to obtain high-performance artificial graphite. The weight ratio of modified graphene, coal tar pitch and particles 2 is 0.15:1:9.

[0044] Example 3

[0045] A high-performance artificial graphite, wherein modified graphene is uniformly distributed in the high-performance artificial graphite.

[0046] In the preparation of modified graphene, dodecyltrimethylammonium bromide-modified graphene oxide was uniformly dispersed in water, and then an aqueous dispersion of nano-carbon black was added. The mixture was ultrasonically stirred until homogeneous, allowed to stand at room temperature for 2 hours, filtered, washed with water, and dried at 60°C to obtain modified graphene. The weight ratio of dodecyltrimethylammonium bromide-modified graphene oxide to nano-carbon black was 1:0.55.

[0047] The preparation method of the above-mentioned high-performance artificial graphite includes the following steps:

[0048] S1, with a tap density ≤ 0.6 g / cm³ 3 Needle coke and petroleum asphalt were mixed and granulated at a weight ratio of 8.3:1.7 to obtain D. 50 Particle 1 has a diameter of 18.3 μm; Particle 1 is mixed with a tap density of 0.45 g / cm³. 3 D 50The tailing fine powder with a size of 3.3 μm is mixed according to a weight ratio of 100:4, carbonized at 1000 ℃ for 11 h, shaped, graphitized at 2900 ℃ for 7.5 h to obtain granular 2;

[0049] S2, the modified graphene is mixed with petroleum pitch at 55 ℃, and then mixed with granular 2 to obtain a granule, carbonized at 1000 ℃ for 11 h, and shaped to obtain high-performance artificial graphite, wherein the weight ratio of the modified graphene, petroleum pitch and granular 2 is 0.13:1:9.

[0050] Comparative Example 1

[0051] The tailing fine powder is not added, and the other steps are the same as in Example 3.

[0052] Comparative Example 2

[0053] The modified graphene is not added, and the other steps are the same as in Example 3.

[0054] Comparative Example 3

[0055] The modified graphene is replaced by pure graphene, and the other steps are the same as in Example 3.

[0056] Comparative Example 4

[0057] The modified graphene is replaced by pure nano carbon black, and the other steps are the same as in Example 3.

[0058] Comparative Example 5

[0059] The modified graphene is replaced by “graphene and nano carbon black with a weight ratio of 1:0.55”, and the other steps are the same as in Example 3.

[0060] The artificial graphite prepared in Examples 1-3 and Comparative Examples 1-5 is taken to detect the tap density, and the performance of the lithium ion battery prepared from the artificial graphite is tested, and the results are shown in Table 1.

[0061] The preparation method of the lithium ion battery is as follows: the artificial graphite prepared in Examples 1-3 and Comparative Examples 1-5 is taken to prepare a negative electrode slurry according to a weight ratio of artificial graphite, conductive agent and binder of 94:1:5; the negative electrode slurry is uniformly coated on a copper foil, and dried in a vacuum at 60 ℃ to obtain a negative electrode sheet; a lithium sheet is used as a positive electrode, and a 1 mol / L LiPF6 solution is used as an electrolyte solution to assemble a lithium ion battery.

[0062] Table 1: Test results

[0063] Test item Tap density g / cm 3 ]] Specific capacity mAh / g First charge-discharge efficiency % Example 1 0.97 355 94.6 Example 2 1.01 358 95.0 Example 3 1.00 360 94.8 Comparative Example 1 0.90 333 90.8 Comparative Example 2 0.83 321 89.5 Comparative Example 3 0.92 342 91.5 Comparative Example 4 0.94 340 91.2 Comparative Example 5 0.94 345 91.6

[0064] As shown in Table 1, the artificial graphite prepared in the application has a high tap density, and has good electrochemical performance when used in a lithium ion battery.

[0065] The above description is only the preferred embodiment of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can make equivalent substitutions or changes according to the technical solution and the inventive concept of the present application within the technical range disclosed by the present application, which should be covered in the protection scope of the present application.

Claims

1. A method for preparing high-performance artificial graphite, characterized in that, Includes the following steps: S1. Take raw coke and binder and granulate to obtain particle 1; mix particle 1 with tailings fine powder, carbonize, shape and graphitize to obtain particle 2. S2. The modified graphene and binder are heated and mixed evenly, then mixed with particles 2 and granulated, carbonized, and shaped to obtain high-performance artificial graphite. In the preparation of modified graphene, quaternary ammonium salt grafted modified graphene oxide and nano carbon black are evenly dispersed in water, allowed to stand, and then separated into solid and liquid components to obtain modified graphene. The tailings fine powder is the fine powder remaining after screening and grading during the manufacture of artificial graphite; the weight ratio of particle 1 to tailings fine powder is 100:3-4. The tapped density of the tailings fine powder is 0.42-0.47 g / cm³. 3 D of the tailings fine powder 50 The particle size is 3-3.5 μm; the D of particle 1 50 It is 18-18.5μm.

2. The method for preparing high-performance artificial graphite according to claim 1, characterized in that, In the preparation of modified graphene, the weight ratio of quaternary ammonium salt grafted modified graphene oxide to nano carbon black is 1:0.5-0.6; and it is left to stand at room temperature for 1-3 hours.

3. The method for preparing high-performance artificial graphite according to claim 1, characterized in that, The raw material coke is at least one of needle coke and petroleum coke; the binder is at least one of coal tar pitch, petroleum pitch, mesophase pitch, and modified pitch.

4. The method for preparing high-performance artificial graphite according to claim 1, characterized in that, In S1, the weight ratio of raw coke to binder is 8-8.5:1.5-2.

5. The method for preparing high-performance artificial graphite according to claim 1, characterized in that, In S1 and S2, the carbonization temperature is 950-1000℃ and the carbonization time is 10-12h.

6. The method for preparing high-performance artificial graphite according to claim 1, characterized in that, In S2, the weight ratio of modified graphene, binder, and particles is 0.1-0.15:1:

9.

7. A high-performance artificial graphite, characterized in that, High-performance artificial graphite is prepared according to the method described in any one of claims 1-6.

8. An application of the high-performance artificial graphite as described in claim 7 in the negative electrode of a lithium-ion battery.