CN114497508A - Power type artificial graphite composite material and preparation method thereof - Google Patents

Abstract

The invention discloses a power type artificial graphite composite material and a preparation method thereof, wherein the power type artificial graphite composite material is of a core-shell structure and comprises an inner core and a shell coated on the surface of the inner core, wherein the inner core comprises graphite with the particle size of 0.5-2 mu m; the shell comprises a lithium vanadate lithium supplement agent, a conductive agent, a boron-containing compound and amorphous carbon thereof. The power type artificial graphite composite material provided by the invention utilizes the lithium vanadate lithium supplement agent to provide sufficient lithium ions, reduces the surface defects of the material, and provides sufficient lithium ions for the charge and discharge processes; and meanwhile, the synergistic effect between the conductive agent and the lithium vanadate lithium supplement agent is exerted, namely, the conductive agent improves the electronic conductivity and the ionic conductivity of the lithium vanadate lithium supplement agent, a conductive network is constructed between particles, and the power and the cycle performance of the material are improved.

Description

Power type artificial graphite composite material and preparation method thereof

Technical Field

The invention belongs to the field of preparation of lithium ion battery materials, and particularly relates to a power type artificial graphite composite material and a preparation method thereof.

Background

With the improvement of the energy density and the quick charge performance of the negative electrode material in the market, the graphite negative electrode material used for the lithium ion battery is required to have high energy density, and the quick charge performance of the material can also be improved. The main ideas for improving the quick charging performance of the high-energy graphite at present are to select raw materials with high isotropy, graphitize at high temperature, modify the surface and optimize a granulation process of the surface. For example, 1) granulation optimization: crushing the carbon material to a certain particle size, kneading to realize secondary granulation, and finally graphitizing to obtain a graphite cathode material with a secondary particle structure; the structure has the defects that the capacity and the quick charging performance are difficult to be considered; 2) surface modification: crushing a carbon material to a certain granularity, carrying out surface modification, and finally carbonizing to obtain a graphite negative electrode material with a primary particle structure; the structure has the defects that the capacity is difficult to improve without graphitization treatment; 3) surface coating: materials with high electronic and ionic conductivity, such as N-doped and beta-doped hard carbon materials, are coated, but this method has a limited range of rate enhancement of the materials. Although the method is improved in the aspects of improving the material power and the energy density thereof, the method has the problems of low efficiency for the first time and low diffusion speed of lithium ions, thereby causing the power performance deviation of the material.

The lithium supplement agent is a compound containing lithium ions, has the characteristics of high specific capacity (more than or equal to 1000mAh/g) and stable structure, and the substance generated after reaction is harmless to the performance of the battery, so that the surface defect of the material can be reduced, and the power performance of the material can be improved.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a power type artificial graphite composite material and a preparation method thereof, which can improve the power performance of a graphite material.

In order to solve the technical problems, the technical scheme provided by the invention is as follows:

a power type artificial graphite composite material is of a core-shell structure and comprises an inner core and a shell coated on the surface of the inner core, wherein the inner core comprises graphite with the particle size of 0.5-2 mu m; the shell comprises a lithium vanadate lithium supplement agent, a conductive agent, a boron-containing compound and amorphous carbon.

Further, the lithium vanadate lithium supplement agent is LiVO₃、Li₃VO₄、Li₂VO₃、LiV₃O₈、Li₄V₃O₈At least one of (1).

Further, the boron-containing compound is one or more of magnesium diboride, titanium diboride, zirconium diboride and tungsten boride, and the particle size is 50-500 nm.

Further, the conductive agent is an oil-based conductive agent solution.

Further, the oil-based conductive agent solution is a carbon nanotube conductive solution and/or a graphene conductive solution, the concentration of the carbon nanotube conductive solution and/or the graphene conductive solution is 0.5-5 wt%, and the solvent is N-methylpyrrolidone.

Further, the mass ratio of the lithium vanadate supplementing agent to the conductive agent to the boron-containing compound to the amorphous carbon is (1-5): 1-5: 0.5-2: 100.

further, the mass ratio of the inner core to the composite material is 1-10 wt%.

A preparation method of a power type artificial graphite composite material comprises the following steps:

preparing a resin organic solution with the mass concentration of 1-10 wt%, adding a conductive agent, a lithium supplement agent and a boron-containing compound, uniformly dispersing by ultrasonic, reacting for 1-6 h at the temperature of 150-250 ℃, filtering, freeze-drying at low temperature, and crushing to obtain a precursor composite material;

preparing a precursor composite material solution with the mass concentration of 1-10 wt%, adding a graphite material, performing spray drying, carbonizing for 1-6 hours in a fluorine/argon mixed gas at the temperature of 600-1000 ℃, and crushing to obtain the power type artificial graphite composite material.

Further, the mass ratio of the resin to the conductive agent to the lithium supplement agent to the auxiliary agent is 100: 1-5: 1-5: 0.5 to 2.

Further, the mass ratio of the precursor composite material to graphite is 1-10: 100.

the invention has the beneficial effects that:

1) the lithium vanadate lithium supplement agent has the advantages of high energy density, stable electrochemical structure, low expansion and the like, and is coated on the surface of graphite to release lithium ions in the charging and discharging process, so that the irreversible capacity of the graphite material is reduced, and the first efficiency is improved; on the other hand, lithium ions released from the material provide sufficient lithium ions for the processes of circulation and the like, and the performances of circulation and the like are improved;

2) the lithium vanadate lithium supplement agent has low self electronic conductivity, the electronic conductivity of the material is improved by adding the graphene, and the material is coated on the surface of graphite, so that the electronic and ionic conductivity of the material is improved, the multiplying power performance is improved, and the temperature rise is reduced;

3) according to the invention, the auxiliary agent is introduced into the lithium vanadate lithium supplement agent, and the auxiliary agent can catalyze the inorganic salt compound of lithium to release active lithium ions at a lower potential, so that the lithium supplement of the graphite material is realized, and the first efficiency of the material is improved.

Drawings

Fig. 1 is an SEM image of a power type artificial graphite composite material prepared in example 1 of the present invention.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Example 1

A preparation method of a power type artificial graphite composite material comprises the following steps:

s1, adding 100g of phenolic resin into 2000ml of carbon tetrachloride solution to prepare a resin organic solution with the mass concentration of 5 wt%; then, 500ml of a1 wt% carbon nanotube N-methylpyrrolidone solution and 5g of LiVO were added₃1g of magnesium diboride; after uniform ultrasonic dispersion, transferring the mixture into a high-pressure reaction kettle, reacting for 3 hours at the temperature of 200 ℃, filtering, freeze-drying at low temperature, and crushing to obtain a precursor composite material;

s2, adding 5g of the precursor composite material into 100ml of carbon tetrachloride, preparing a precursor composite material solution with the mass concentration of 5 wt%, adding 100g of artificial graphite material, carrying out spray drying, transferring to a tube furnace, introducing a fluorine/argon mixed gas (the volume ratio is 1:1), carbonizing for 3h at the temperature of 800 ℃, and crushing to obtain the power type artificial graphite composite material.

Example 2

A preparation method of a power type artificial graphite composite material comprises the following steps:

s1, adding 100g of epoxy resin into 10000ml of N-methyl pyrrolidone to prepare a resin organic solution with the mass concentration of 1 wt%, and then adding 200ml of graphene conductive agent solution with the mass concentration of 0.5 wt% and 1g of Li₃VO₄0.5g of titanium diboride, uniformly dispersing by ultrasonic, transferring to a high-pressure reaction kettle, reacting for 6 hours at the temperature of 150 ℃, filtering, freeze-drying at low temperature, and crushing to obtain a precursor composite material;

s2, adding 1g of precursor composite material into 100ml of N-methyl pyrrolidone to prepare a precursor composite material solution with the mass concentration of 1 wt%, adding 100g of artificial graphite material, carrying out spray drying, transferring to a tube furnace, introducing a fluorine gas/argon gas mixed gas (volume ratio, 1:1), carbonizing for 6 hours at the temperature of 600 ℃, and crushing to obtain the power type artificial graphite composite material.

Example 3

A preparation method of a power type artificial graphite composite material comprises the following steps:

s1, adding 100g of furfural resin into 1000ml of cyclohexane solution to prepare a resin organic solution with the mass concentration of 10 wt%, and then adding 100ml of 5 wt% carbon nanotube conductive agent solution and 5g of LiV₃O₈2g of zirconium diboride, uniformly dispersing by ultrasonic, transferring to a high-pressure reaction kettle, reacting for 1 hour at the temperature of 250 ℃, filtering, freeze-drying at low temperature, and crushing to obtain a precursor composite material;

s2, adding 10g of the precursor composite material into 100ml of cyclohexane solution to prepare a precursor composite material solution with the mass concentration of 10 wt%, adding 100g of artificial graphite material, carrying out spray drying, transferring to a tube furnace, introducing fluorine gas/argon gas mixed gas (the volume ratio is 1:1), carbonizing for 1h at the temperature of 1000 ℃, and crushing to obtain the power type artificial graphite composite material.

Comparative example

Adding 10g of phenolic resin into 200ml of carbon tetrachloride solution, preparing a resin organic solution with the mass concentration of 5 wt%, ultrasonically dispersing uniformly, adding 100g of artificial graphite material, spray-drying, transferring into a tubular furnace, introducing argon, carbonizing for 3 hours at the temperature of 800 ℃, and crushing to obtain the graphite composite material.

Examples of the experiments

1. Physical and chemical property test

1.1SEM test

The power type artificial graphite composite material prepared in example 1 was subjected to SEM test, and the test results are shown in fig. 1.

As can be seen from FIG. 1, the power type artificial graphite composite material prepared in example 1 is granular, has uniform size distribution, and has a particle size of 8-15 μm.

1.2 powder conductivity test:

the power type artificial graphite composite material prepared in examples 1 to 3 and the graphite composite material prepared in the comparative example were pressed into a block structure, and then the conductivity of the powder was tested using a four-probe tester. The test results are shown in table 1.

1.3 powder compaction Density test

Powder compaction density tests were performed on the power type artificial graphite composite materials prepared in examples 1 to 3 and the graphite composite material prepared in comparative example. During testing, a certain mass of the power type artificial graphite composite material prepared in examples 1 to 3 and the graphite composite material powder prepared in the comparative example were weighed and placed in a mold, and pressed by 2T pressure (by using a powder compaction densimeter, 1g of the powder was placed in a fixed kettle and then pressed by 2T pressure, and then held for 10S, and then the volume under pressing was calculated, and the compaction density was calculated), and the powder compaction density was calculated. Meanwhile, the test results are shown in Table 1 according to GB/T2433and 2019 graphite cathode materials for lithium ion batteries.

TABLE 1

Item	Example 1	Example 2	Example 3	Comparative example
					Resistivity of powder (. OMEGA. m)	8*10-8	5*10-8	6*10-8	8*10-7
Compacted density (g/cm) of powder3)	1.69	1.66	1.64	1.51
					Specific surface area (m)2/g)	1.82	1.77	1.68	1.21

As can be seen from table 1, the powder resistivity of the power type artificial graphite composite material prepared by the invention is obviously lower than that of the comparative example, because the surface of the negative electrode material is doped with graphene with high electronic conductivity, the electronic conductivity is reduced; meanwhile, the conductive agent has a lubricating effect, and the compaction density of the material is improved.

2. Button cell test

Button cells A1, A2, A3 and B1 were assembled by using the power type artificial graphite composite materials prepared in examples 1 to 3 and the graphite composite material prepared in comparative example as negative electrode materials, respectively. The assembling method comprises the following steps: the power type artificial graphite composite material prepared in examples 1 to 3 and the graphite composite material prepared in the comparative example were added with a binder, a conductive agent and a solvent, respectively, stirred to prepare a slurry, coated on a copper foil, dried and rolled to prepare a negative electrode sheet. The binder is LA132 binder, the conductive agent is SP, and the solvent is secondary distilled water. The proportion of each component is as follows: and (3) anode material: SP: LA 132: 95g of secondary distilled water: 1 g: 4 g: 220 mL; the electrolyte is LiPF₆/EC+DEC(LiPF₆The concentration of the lithium ion battery is 1.2mol/L, the volume ratio of EC to DEC is 1:1), the metal lithium sheet is used as a counter electrode, and the diaphragm is a Polyethylene (PE), polypropylene (PP) or polyethylene propylene (PEP) composite membrane. The button cell is assembled in a glove box filled with argon, and the electrochemical performance test is carried out on a Wuhan blue CT2001A type battery tester, wherein the charging and discharging voltage range is 0.005V-2.0V, and the charging and discharging multiplying power is 0.1C. The test results are shown in table 2.

And simultaneously taking the negative plate, and testing the liquid absorption and retention capacity of the negative plate.

TABLE 2

Item	Example 1/A1	Example 2/A2	Example 3/A3	Comparative example B1
					First discharge capacity (mAh/g)	368.3	367.4	365.5	350.4
First efficiency (%)	97.1	96.8	96.5	92.2
					Liquid suction capacity (mL/min)	9.8	9.3	8.8	5.4

As can be seen from table 2, the lithium ion batteries using the power type artificial graphite composite materials obtained in examples 1 to 3 as the negative electrode material had significantly higher first discharge capacity and first charge-discharge efficiency than the graphite composite materials prepared in the comparative examples. The lithium vanadate lithium supplement agent provides sufficient lithium ions for the first charge and discharge of the battery, the specific capacity and the conductivity of the material of the lithium vanadate lithium supplement agent are improved, the first efficiency is further improved, and meanwhile, the lithium vanadate lithium supplement agent has a high specific surface area and the liquid absorption capacity of the material is improved.

3. Pouch cell testing

The power type artificial graphite composite material prepared in examples 1 to 3 and the graphite composite material in the comparative example were used as negative electrode materials to prepare negative electrode sheets. With ternary materials (LiNi)_1/3Co_1/3Mn_1/3O₂) As the positive electrode, LiPF₆Solution (solvent EC + DEC, volume ratio 1:1, LiPF)₆Concentration of 1.3mol/L) is used as electrolyte, celegard2400 is used as a diaphragm, and 2Ah soft package batteries A10, A20, A30 and B10 are prepared. After which the soft pack power was testedThe cycle performance and the rate performance of the pool (1C/1C, 25 ℃, 2.8-4.2V).

Multiplying power performance test conditions: charging rate: 1C/2C/3C/5C, discharge multiplying power of 1C; voltage range: 2.8-4.2V. The test results are shown in Table 3.

TABLE 3

As can be seen from table 3, the pouch battery prepared from the power type artificial graphite composite material of the present invention has a better constant current ratio. The reason is that the lithium vanadate lithium supplement agent is coated on the surface of the power type artificial graphite composite material prepared in the embodiments 1 to 3, so that sufficient lithium ions are provided in the charging and discharging process, the quick charging performance of the material is improved, namely, the constant current ratio of the material is improved, and the cycle performance is improved.

The foregoing is only a preferred embodiment of the present invention, and many variations in the detailed description and the application range can be made by those skilled in the art without departing from the spirit of the present invention, and all changes that fall within the protective scope of the invention are therefore considered to be within the scope of the invention.

Claims (10)

1. The power type artificial graphite composite material is characterized by having a core-shell structure and comprising an inner core and a shell coated on the surface of the inner core, wherein the inner core comprises graphite with the particle size of 0.5-2 mu m; the shell comprises a lithium vanadate lithium supplement agent, a conductive agent, a boron-containing compound and amorphous carbon.

2. The power type artificial graphite composite material according to claim 1, wherein the lithium vanadate lithium supplement agent is LiVO₃、Li₃VO₄、Li₂VO₃、LiV₃O₈、Li₄V₃O₈At least one of (1).

3. The power type artificial graphite composite material according to claim 1, wherein the boron-containing compound is one or more of magnesium diboride, titanium diboride, zirconium diboride and tungsten boride, and the particle size is 50-500 nm.

4. The power type artificial graphite composite according to claim 1, wherein the conductive agent is an oil-based conductive agent solution.

5. The power type artificial graphite composite material according to claim 4, wherein the oil-based conductive agent solution is a carbon nanotube conductive solution and/or a graphene conductive solution, the concentration of the carbon nanotube conductive solution and/or the graphene conductive solution is 0.5-5 wt%, and the solvent is N-methylpyrrolidone.

6. The power type artificial graphite composite material according to claim 1, wherein the mass ratio of the lithium vanadate supplementing agent, the conductive agent, the boron-containing compound and the amorphous carbon is 1-5: 1-5: 0.5-2: 100.

7. the power type artificial graphite composite material according to any one of claims 1 to 6, wherein the inner core accounts for 1 to 10 wt% of the composite material.

8. The preparation method of the power type artificial graphite composite material is characterized by comprising the following steps:

preparing a resin organic solution with the mass concentration of 1-10 wt%, adding a conductive agent, a lithium supplement agent and a boron-containing compound, uniformly dispersing by ultrasonic, reacting for 1-6 h at the temperature of 150-250 ℃, filtering, freeze-drying at low temperature, and crushing to obtain a precursor composite material;

preparing a precursor composite material solution with the mass concentration of 1-10 wt%, adding a graphite material, performing spray drying, carbonizing for 1-6 hours in a fluorine/argon mixed gas at the temperature of 600-1000 ℃, and crushing to obtain the power type artificial graphite composite material.

9. The preparation method of the power type artificial graphite composite material according to claim 8, wherein the mass ratio of the resin, the conductive agent, the lithium supplement agent and the auxiliary agent is 100: 1-5: 1-5: 0.5 to 2.

10. The preparation method of the power type artificial graphite composite material according to claim 8, wherein the mass ratio of the precursor composite material to graphite is 1-10: 100.

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