CN115784225A - Modified artificial graphite negative electrode material and preparation method thereof - Google Patents
Modified artificial graphite negative electrode material and preparation method thereof Download PDFInfo
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- CN115784225A CN115784225A CN202211741264.3A CN202211741264A CN115784225A CN 115784225 A CN115784225 A CN 115784225A CN 202211741264 A CN202211741264 A CN 202211741264A CN 115784225 A CN115784225 A CN 115784225A
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- 238000002360 preparation method Methods 0.000 title claims abstract description 12
- 239000007773 negative electrode material Substances 0.000 title description 18
- 238000010438 heat treatment Methods 0.000 claims abstract description 61
- 239000000463 material Substances 0.000 claims abstract description 58
- 239000002994 raw material Substances 0.000 claims abstract description 56
- 238000001354 calcination Methods 0.000 claims abstract description 48
- 238000005087 graphitization Methods 0.000 claims abstract description 36
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 29
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention discloses a modified artificial graphite cathode material and a preparation method thereof. The preparation method comprises the following steps: (1) calcining: calcining the raw material coke to prepare an artificial graphite raw material; the calcining temperature is 400-1100 ℃; (2) modification: carrying out first heat treatment on a mixture A of a modifier and an artificial graphite raw material; the modifier can modify the surface of the artificial graphite raw material; the residual carbon content of the modifier is 1-3%; (3) bonding: carrying out second heat treatment on the mixture B of the adhesive and the material obtained in the step (2); (4) graphitization: and (4) carrying out graphitization treatment on the material obtained in the step (3). According to the invention, through low-temperature calcination and modification, the growth of graphite microcrystals is promoted, the bonding performance is improved, the graphitization degree is high, the particle strength of the prepared modified artificial graphite anode material is high, the dynamic performance is improved, and the modified artificial graphite anode material has more stable long-cycle performance when being applied to a battery.
Description
Technical Field
The invention relates to a modified artificial graphite negative electrode material and a preparation method thereof.
Background
With the rapid development of the current industry, the storage quantity of the traditional energy resources is at risk. In addition, the use of traditional energy sources brings global environmental pollution, and the living environment is seriously tested due to the emission of greenhouse gases, so that the development of new energy sources is particularly important.
In 1990, sony corporation commercializes the lithium ion battery cathode carbon material for the first time, and the carbon material has the characteristics of high energy density, long circulation, no memory effect, green environmental protection and the like, and is widely applied to 3C electronic portable products, new energy automobiles and other fields. As the main components of lithium ion batteries, the negative electrode materials already have systems such as natural graphite, artificial graphite, hard carbon, soft carbon, graphene, carbon nanotubes and the like; the artificial graphite is used as a negative electrode material, and has the advantages of good cycle performance and rate capability, good selectivity to electrolyte and the like. With the development of power automobiles, the preparation of artificial graphite with long cycle performance has become a hot research direction.
Disclosure of Invention
The invention aims to provide a new direction for preparing an artificial graphite cathode material with long cycle performance, and provides a modified artificial graphite cathode material and a preparation method thereof. According to the invention, through low-temperature calcination and modification, the growth of graphite microcrystals is promoted, the surface activity performance is improved, the adhesion performance is further improved, the material is easy to graphitize, the graphitization degree is high, and the prepared modified artificial graphite cathode material has improved dynamic performance and more stable long-cycle performance. The modified artificial graphite cathode material prepared by the invention has high particle strength, and can realize better long-cycle performance under the condition of excellent first discharge capacity and first efficiency when being applied to a battery.
The invention solves the technical problems through the following technical scheme.
The invention provides a preparation method of a modified artificial graphite negative electrode material, which comprises the following steps:
(1) And (3) calcining: calcining the raw coke to obtain an artificial graphite raw material; the calcining temperature is 400-1100 ℃;
(2) Modification: carrying out first heat treatment on a mixture A of a modifier and the artificial graphite raw material; the modifier can modify the surface of the artificial graphite raw material; the carbon residue of the modifier is 1-3%;
(3) Bonding: carrying out second heat treatment on the mixture B of the adhesive and the material obtained in the step (2);
(4) Graphitization: and (4) carrying out graphitization treatment on the material obtained in the step (3).
In the step (1), the raw coke may be one or more of petroleum raw coke, petroleum raw needle coke, petroleum calcined raw coke, petroleum calcined needle coke, coal-based raw needle coke, coal-based calcined raw coke and coal-based calcined needle coke, and is preferably one or more of petroleum raw needle coke, petroleum raw coke and coal-based raw needle coke.
In step (1), the volatile matter of the raw coke may be 18% or less, preferably 6 to 13%, for example 6 to 10%. Volatile components refer to the mass loss of coal after moisture correction by heating the coal under specified conditions without air.
In the step (1), the ash content of the raw coke can be less than or equal to 1.0%, and preferably less than or equal to 0.5%. Ash is the residue of a series of physical and chemical changes at high temperature, the organic components are volatilized and dissipated, and the inorganic components (mainly inorganic salts and oxides) remain.
In step (1), the calcining equipment can be a calcining device conventional in the art, and is preferably one or more of a shuttle kiln, a tunnel kiln and a rotary kiln, such as a shuttle kiln.
In step (1), the temperature of the calcination is preferably 400 to 1000 ℃, for example 400 ℃ or 900 ℃. The proper calcination temperature can discharge the volatile components of the raw coke and promote the growth of microcrystals, so that the first discharge capacity of the finally prepared battery is improved.
In step (1), the calcination time may be 4 to 8 hours, for example, 6 hours.
In the step (1), the volatile component of the artificial graphite raw material can be 1 to 6 percent, and preferably 1 to 3 percent.
In the step (1), after the calcination, a pulverization operation may be further included.
Wherein the equipment for comminuting may be conventional in the art, preferably is one or more of a mechanical mill, a roll mill and a jet mill, for example a roll mill.
In the step (1), the particle diameter D50 of the artificial graphite raw material may be 6 to 11 μm, for example, 6 to 10 μm.
In the step (2), the modifier is preferably a substance having a polar group. Polar groups refer to groups in which the positive and negative charge centers are not coincident. Such as one or more of coal tar, ethylene tar, pitch, monosaccharides, and polysaccharides. The polysaccharide is preferably starch. The modifier is uniformly covered and solidified on the surface of the material, so that the surface of the material particle has abundant active sites, but the adhesiveness of the modifier is poor.
In the step (2), the carbon residue of the modifier is preferably 1%, 2% or 3%. The residual carbon content generally refers to the ratio of the weight of the residual residue to the mass of the fuel oil sample, wherein the fuel oil sample is heated without supplementing air, and the fuel oil is gradually decomposed and coked to obtain a residual residue without volatility.
In the step (2), the amount of the modifier can be 2-15%, preferably 2%, 5%, 10% or 15%, and the% refers to the mass percentage of the modifier in the raw material of the artificial graphite.
In the step (2), the temperature of the first heat treatment may be 300 to 650 ℃, for example, 300 ℃ or 550 ℃.
In the step (2), the time of the first heat treatment may be 2 to 6 hours, for example, 2 hours or 4 hours.
In step (2), the equipment for the first heat treatment may be conventional in the art, such as an electrically heated V-shaped reaction vessel.
In the step (3), the binder may be a polymer material conventionally used in the art, and is preferably one or more of petroleum asphalt, coal asphalt and resin.
In the step (3), the amount of the adhesive may be 2 to 8%, for example, 5% or 8%,% being the mass percentage of the adhesive in the mixture B.
In the step (3), the temperature of the second heat treatment may be 450 to 700 ℃, for example, 630 ℃.
In the step (3), the time of the second heat treatment may be 2 to 6 hours, for example, 4 hours.
In the step (3), the adhesive has rich active groups and is combined with the active sites in the material obtained in the step (2), so that the bonding degree is increased. The bonding process causes the material to bond firmly from the primary particles to the secondary particles.
In the step (3), after the second heat treatment, an operation of depolymerization may be further included. Depolymerization opens the excessively bonded portion, adjusts the particle size distribution, improves the tap density of the material, and increases the rear end recovery.
In step (3), after the second heat treatment, the D50 of the material may be 13 to 18 μm, for example, 14.1 μm, 14.9 μm, 15.9 μm, 16.2 μm, 16.8 μm or 18 μm.
In step (4), the temperature of the graphitization treatment may be conventional in the art, and is preferably 2300 to 2600 ℃, for example 2400 ℃ or 2500 ℃. Since the calcination process allows the graphite crystallites to grow to some extent already, the graphitization temperature according to the present invention can be lower with the same graphitization degree.
In the step (4), the graphitization treatment time can be 36-60 h, such as 48h.
The invention also provides a modified artificial graphite negative electrode material which is prepared by the preparation method.
In the present invention, the modified artificial graphite anode material may have a graphitization degree of 91 to 93%, for example, 91.2%, 92.2%, 92.3%, 92.4%, 92.5%, or 92.6%.
In the present invention, the particle strength of the modified artificial graphite anode material may be 74 to 92%, for example, 74.2%, 80.4%, 85.3%, 86.1%, 90.2%, 90.3%, or 91.9%.
On the basis of the common knowledge in the field, the above preferred conditions can be combined randomly to obtain the preferred embodiments of the invention.
The reagents and starting materials used in the present invention are commercially available.
The positive progress effects of the invention are as follows:
according to the invention, in the preparation process of conventional secondary particles, the modified artificial graphite negative electrode material is calcined at low temperature before bonding treatment, so that the growth of graphite microcrystals is promoted, modification is carried out, the surface activity performance is improved, the bonding performance is further improved, the material is easy to graphitize, the graphitization degree is high, and the dynamic performance of the prepared modified artificial graphite negative electrode material is improved.
Furthermore, the method can perform graphitization at a low temperature, and complete development of the whole graphite microcrystal can be completed at a low temperature; the graphitization degree of the material can be adjusted through low-temperature graphitization, the interlayer distance is increased, the stability of rapid insertion and extraction of lithium ions is utilized, and the long cycle performance is more stable.
The modified artificial graphite cathode material prepared by the invention has high particle strength, and can realize better long-cycle performance under the condition of excellent first discharge capacity and first efficiency when being applied to a battery.
Drawings
Fig. 1 is an SEM image of the modified artificial graphite anode material prepared in example 1.
Detailed Description
The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention. The experimental methods without specifying specific conditions in the following examples were selected according to the conventional methods and conditions, or according to the commercial instructions.
In the following examples and comparative examples, the residual carbon amount = coking value added amount.
The coking value test method comprises the following steps: weighing 1.0000g of dry sample with the granularity of 1-3 mm, placing the dry sample into a 20mL porcelain crucible with constant weight, covering the porcelain crucible, placing the porcelain crucible into a 100mL porcelain crucible or a graphite crucible which is paved with 10mm thick coke particles in advance, filling the gap between the two crucibles with the coke particles, completely burying the crucibles into the coke particles, and covering an outer crucible cover. The crucible is placed on a nickel-chromium wire bracket and placed into a muffle furnace at 550 +/-l 0 ℃, and the bottom of the crucible is 25mm away from the bottom of the furnace. After the sample is put in, the furnace temperature must be recovered to a constant temperature within 10min, the heating is continued for 2h, the crucible is taken out and cooled in the air for about 15min, the inner crucible is taken out, the coke powder attached to the outside of the crucible is swept, the crucible is put in a dryer, the temperature is cooled to the room temperature, and the weighing is carried out. The coking value is calculated as follows:
in the formula, K is the coking value of asphalt,%; m is the sample mass, g; m1 is the inner crucible mass, g; m2 is the inner crucible and residue mass, g.
Example 1
(1) Calcining petroleum raw needle coke with the volatile component of 6-10 percent and the ash content of less than or equal to 0.5 percent in a shuttle kiln, and crushing in a rolling mill to obtain an artificial graphite raw material with the volatile component of 1-3 percent and the D50 of 6-10 mu m; the calcining temperature is 900 ℃ and the time is 6 hours;
(2) Mixing an artificial graphite raw material with 5% of coal tar (the residual carbon content is 1%), stirring and heating by an electric heating V-shaped reaction kettle to enable active components to cover the surface of the raw material like a network; the heating temperature is 550 ℃ and the time is 4 hours;
(3) Drying the material obtained in the step (2), mixing with 5% coal pitch for granulation and depolymerization to densify the material, and obtaining secondary particles with D50 of 16.2 microns; during granulation, the heating temperature is 630 ℃ and the time is 4 hours;
(4) Graphitizing the material obtained in the step (3) at 2400 ℃ for 48 hours to obtain the modified artificial graphite cathode material. Fig. 1 is an SEM image of the modified artificial graphite negative electrode material.
The D50 of the modified artificial graphite cathode material is 16.2 mu m, and the tap density is 1.01g/cm 3 ，BET 1.42m 2 The graphitization degree is 92.6 percent and the particle strength is 90.2 percent.
Example 2
(1) Calcining coal-based raw needle coke with the volatile component of 6-10% and the ash content of less than or equal to 0.5% in a shuttle kiln, and crushing in a rolling mill to obtain an artificial graphite raw material with the volatile component of 1-3% and the D50 of 6-10 mu m; the calcining temperature is 900 ℃ and the time is 6 hours;
(2) Mixing an artificial graphite raw material with 15% of starch (the residual carbon content is 3%), stirring and heating the mixture by an electric heating V-shaped reaction kettle to enable active components to cover the surface of the raw material like a network; the heating temperature is 550 ℃, and the time is 4h;
(3) Drying the material obtained in the step (2), mixing 8% petroleum asphalt, granulating and depolymerizing to densify the material, and obtaining secondary particles with the D50 of 16.8 mu m; during granulation, the heating temperature is 630 ℃ and the time is 4 hours;
(4) Graphitizing the material obtained in the step (3) at 2400 ℃ for 48h to obtain the modified artificial graphite cathode material.
The D50 of the modified artificial graphite cathode material is 16.8 mu m, and the tap density is 0.99g/cm 3 ，BET1.53m 2 The graphitization degree is 92.3 percent and the particle strength is 90.3 percent.
Example 3
(1) Calcining petroleum raw coke with the volatile component of 6-10% and the ash content of less than or equal to 0.5% in a shuttle kiln, and crushing in a rolling mill to obtain an artificial graphite raw material with the volatile component of 1-3% and the D50 of 6-10 mu m; the calcining temperature is 900 ℃ and the time is 6 hours;
(2) Mixing artificial graphite raw material with 10% ethylene tar (residual carbon content is 2%), stirring and heating by an electric heating V-shaped reaction kettle to enable active components to cover the surface of the raw material like a network; the heating temperature is 550 ℃ and the time is 4 hours;
(3) Drying the material obtained in the step (2), mixing with 5% resin, granulating, depolymerizing to densify the material, and obtaining secondary particles with D50 of 15.9 μm; during granulation, the heating temperature is 630 ℃ and the time is 4 hours;
(4) Graphitizing the material obtained in the step (3) at 2500 ℃ for 48h to obtain the modified artificial graphite cathode material.
The D50 of the modified artificial graphite anode material is 15.9 mu m, and the tap density is 1.04g/cm 3 ，BET1.41m 2 The graphitization degree is 92.5 percent and the particle strength is 91.9 percent.
Example 4
(1) Calcining petroleum raw needle coke with the volatile component of 6-10% and the ash content of less than or equal to 0.5% in a shuttle kiln, and crushing in a rolling mill to obtain an artificial graphite raw material with the volatile component of 1-3% and the D50 of 6-10 mu m; the calcining temperature is 400 ℃ and the time is 6 hours;
(2) Mixing an artificial graphite raw material with 5% of coal tar (the residual carbon content is 1%), stirring and heating the mixture by an electric heating V-shaped reaction kettle to enable active components to cover the surface of the raw material like a network; the heating temperature is 550 ℃, and the time is 4h;
(3) Drying the material obtained in the step (2), mixing with 5% coal pitch, granulating, and depolymerizing to densify the material to obtain secondary particles with D50 of 15.9 μm; during granulation, the heating temperature is 630 ℃ and the time is 4 hours;
(4) Graphitizing the material obtained in the step (3) at 2500 ℃ for 48h to obtain the modified artificial graphite cathode material.
The D50 of the modified artificial graphite anode material is 15.9 mu m, and the tap density is 1.04g/cm 3 ，BET 1.52m 2 (ii)/g, the degree of graphitization was 91.2%, and the particle strength was 86.1%.
Example 5
(1) Calcining petroleum raw needle coke with the volatile component of 6-10% and the ash content of less than or equal to 0.5% in a shuttle kiln, and crushing in a rolling mill to obtain an artificial graphite raw material with the volatile component of 1-3% and the D50 of 6-10 mu m; the calcining temperature is 900 ℃ and the time is 6 hours;
(2) Mixing an artificial graphite raw material with 2% of asphalt (the residual carbon content is 1%), stirring and heating by an electric heating V-shaped reaction kettle to enable active components to cover the surface of the raw material like a network; the heating temperature is 550 ℃ and the time is 4 hours;
(3) Drying the material obtained in the step (2), mixing with 5% coal pitch, granulating, and depolymerizing to densify the material to obtain secondary particles with D50 of 18.0 μm; during granulation, the heating temperature is 630 ℃ and the time is 4 hours;
(4) Graphitizing the material obtained in the step (3) at 2500 ℃ for 48h to obtain the modified artificial graphite cathode material.
The D50 of the modified artificial graphite cathode material is 18.0 mu m, and the tap density is 0.94g/cm 3 ，BET1.34m 2 The graphitization degree is 92.2 percent and the particle strength is 80.4 percent.
Example 6
(1) Calcining petroleum raw needle coke with the volatile component of 6-10% and the ash content of less than or equal to 0.5% in a shuttle kiln, and crushing in a rolling mill to obtain an artificial graphite raw material with the volatile component of 1-3% and the D50 of 6-10 mu m; the calcining temperature is 900 ℃ and the time is 6 hours;
(2) Mixing an artificial graphite raw material with 5% of coal tar (the residual carbon content is 1%), stirring and heating the mixture by an electric heating V-shaped reaction kettle to enable active components to cover the surface of the raw material like a network; heating at 300 deg.C for 4 hr;
(3) Drying the material obtained in the step (2), mixing with 5% coal pitch for granulation and depolymerization to densify the material, and obtaining secondary particles with D50 of 14.1 mu m; during granulation, the heating temperature is 630 ℃ and the time is 4 hours;
(4) Graphitizing the material obtained in the step (3) at 2500 ℃ for 48h to obtain the modified artificial graphite cathode material.
The D50 of the modified artificial graphite cathode material is 14.1 mu m, and the tap density is 0.98g/cm 3 ，BET1.64m 2 The graphitization degree is 92.4%, and the particle strength is 74.2%.
Example 7
(1) Calcining petroleum raw needle coke with the volatile component of 6-10% and the ash content of less than or equal to 0.5% in a shuttle kiln, and crushing in a rolling mill to obtain an artificial graphite raw material with the volatile component of 1-3% and the D50 of 6-10 mu m; the calcining temperature is 900 ℃ and the time is 6 hours;
(2) Mixing an artificial graphite raw material with 5% of coal tar (the residual carbon content is 1%), stirring and heating the mixture by an electric heating V-shaped reaction kettle to enable active components to cover the surface of the raw material like a network; the heating temperature is 550 ℃ and the time is 2 hours;
(3) Drying the material obtained in the step (2), mixing with 5% coal pitch, granulating, and depolymerizing to densify the material to obtain secondary particles with D50 of 14.9 μm; during granulation, the heating temperature is 630 ℃ and the time is 4 hours;
(4) Graphitizing the material obtained in the step (3) at 2500 ℃ for 48h to obtain the modified artificial graphite cathode material.
The D50 of the modified artificial graphite cathode material is 14.9 mu m, and the tap density is 1.00g/cm 3 ，BET1.51m 2 Per gram, graphitization degree 92.3%The particle strength was 85.3%.
Comparative example 1
(1) Crushing petroleum raw needle coke with the volatile component of 6-10 percent and the ash content of less than or equal to 0.5 percent in a rolling mill to obtain an artificial graphite raw material with the D50 of 6-10 mu m;
(2) Mixing an artificial graphite raw material with 7% of ethylene tar (the residual carbon content is 1%), stirring and heating by an electric heating V-shaped reaction kettle to enable active components to cover the surface of the raw material like a network; the heating temperature is 550 ℃ and the time is 4 hours;
(3) Drying the material obtained in the step (2), mixing 7% of resin, granulating and depolymerizing to densify the material, and obtaining secondary particles with the D50 of 16 microns; during granulation, the heating temperature is 630 ℃ and the time is 4 hours;
(4) Graphitizing the material obtained in the step (3) at 2500 ℃ for 48h to obtain the modified artificial graphite cathode material.
The D50 of the modified artificial graphite cathode material is 16 mu m, and the tap density is 1.04g/cm 3 ，BET1.67m 2 The graphitization degree is 90.5 percent and the particle strength is 70.4 percent.
Comparative example 2
(1) Calcining petroleum raw coke with the volatile component of 6-10% and the ash content of less than or equal to 0.5% in a shuttle kiln, and crushing in a rolling mill to obtain an artificial graphite raw material with the volatile component of 1-3% and the D50 of 6-10 mu m; the calcining temperature is 900 ℃ and the time is 6 hours;
(2) Mixing an artificial graphite raw material with 2% of ethylene tar (the residual carbon content is 0.4%), stirring and heating by an electric heating V-shaped reaction kettle to enable active components to cover the surface of the raw material like a network; the heating temperature is 550 ℃ and the time is 4 hours;
(3) Drying the material obtained in the step (2), mixing with 1% resin, granulating, depolymerizing to densify the material, and obtaining secondary particles with D50 of 14.4 μm; during granulation, the heating temperature is 630 ℃ and the time is 4 hours;
(4) Graphitizing the material obtained in the step (3) at 2500 ℃ for 48h to obtain the modified artificial graphite cathode material.
The D50 of the modified artificial graphite negative electrode material is 14.4 mu m, and the tap density is 0.94g/cm 3 ，BET1.72m 2 (iv)/g, the degree of graphitization was 92.4%, and the particle strength was 82.7%.
Comparative example 3
(1) Calcining petroleum raw needle coke with the volatile component of 6-10 percent and the ash content of less than or equal to 0.5 percent in a shuttle kiln, and crushing in a rolling mill to obtain an artificial graphite raw material with the volatile component of 1-3 percent and the D50 of 6-10 mu m; the calcining temperature is 900 ℃ and the time is 6h;
(2) Mixing an artificial graphite raw material with 1% of ethylene tar (the residual carbon content is 0.2%), stirring and heating by an electric heating V-shaped reaction kettle to enable active components to cover the surface of the raw material like a network; the heating temperature is 550 ℃ and the time is 4 hours;
(3) Drying the material obtained in the step (2), mixing with 10% coal pitch, granulating, and depolymerizing to densify the material to obtain secondary particles with D50 of 15.1 μm; during granulation, the heating temperature is 630 ℃ and the time is 4 hours;
(4) Graphitizing the material obtained in the step (3) at 2500 ℃ for 48h to obtain the modified artificial graphite cathode material.
The D50 of the modified artificial graphite anode material is 15.1 mu m, and the tap density is 1.01g/cm 3 ，BET1.6m 2 (ii)/g, the degree of graphitization is 92.2%, and the particle strength is 80.6%.
Comparative example 4
(1) Calcining coal-based raw needle coke with the volatile component of 6-10% and the ash content of less than or equal to 0.5% in a shuttle kiln, and crushing in a rolling mill to obtain an artificial graphite raw material with the volatile component of 1-3% and the D50 of 6-10 mu m; the calcining temperature is 900 ℃ and the time is 6 hours;
(2) Mixing an artificial graphite raw material with 20% of ethylene tar (the residual carbon content is 4%), stirring and heating by an electric heating V-shaped reaction kettle to enable active components to cover the surface of the raw material like a network; the heating temperature is 550 ℃, and the time is 4h;
(3) Drying the material obtained in the step (2), mixing with 10% resin, granulating, and depolymerizing to densify the material to obtain secondary particles with D50 of 20.3 μm; during granulation, the heating temperature is 630 ℃ and the time is 4 hours;
(4) Graphitizing the material obtained in the step (3) at 2500 ℃ for 48h to obtain the modified artificial graphite cathode material.
The D50 of the modified artificial graphite anode material is 20.3 mu m, and the tap density is 0.83g/cm 3 ，BET1.42m 2 (ii)/g, the degree of graphitization was 92.6%, and the particle strength was 71.2%.
Comparative example 5
(1) Calcining coal-based raw needle coke with the volatile component of 6-10% and the ash content of less than or equal to 0.5% in a shuttle kiln, and crushing in a rolling mill to obtain an artificial graphite raw material with the volatile component of 1-3% and the D50 of 6-10 mu m; the calcining temperature is 1300 ℃ and the time is 6 hours;
(2) Mixing 20% of ethylene tar (the residual carbon content is 4%) with an artificial graphite raw material, stirring and heating the mixture by an electric heating V-shaped reaction kettle to enable active components to cover the surface of the raw material like a network; the heating temperature is 550 ℃, and the time is 4h;
(3) Drying the material obtained in the step (2), mixing with 10% resin, granulating, depolymerizing to densify the material, and obtaining secondary particles with D50 of 16.3 μm; during granulation, the heating temperature is 630 ℃ and the time is 4 hours;
(4) Graphitizing the material obtained in the step (3) at 2500 ℃ for 48h to obtain the modified artificial graphite cathode material.
The D50 of the modified artificial graphite cathode material is 16.3 mu m, and the tap density is 0.96g/cm 3 ，BET1.65m 2 (ii)/g, graphitization degree of 93.6%, and particle strength of 81.2%.
Comparative example 6
(1) Calcining petroleum raw needle coke with the volatile component of 6-10 percent and the ash content of less than or equal to 0.5 percent in a shuttle kiln, and crushing in a rolling mill to obtain an artificial graphite raw material with the volatile component of 1-3 percent and the D50 of 6-10 mu m; the calcining temperature is 1300 ℃ and the time is 6 hours;
(2) Mixing an artificial graphite raw material with 5% of coal tar (the residual carbon content is 1%), stirring and heating the mixture by an electric heating V-shaped reaction kettle to enable active components to cover the surface of the raw material like a network; the heating temperature is 550 ℃ and the time is 4 hours;
(3) Drying the material obtained in the step (2), mixing with 5% coal pitch for granulation and depolymerization to densify the material, and obtaining secondary particles with D50 of 16.2 microns; during granulation, the heating temperature is 630 ℃ and the time is 4 hours;
(4) Graphitizing the material obtained in the step (3) at 2500 ℃ for 48h to obtain the modified artificial graphite cathode material.
The D50 of the modified artificial graphite cathode material is 15.0 mu m, and the tap density is 0.97g/cm 3 ，BET1.46m 2 (ii)/g, graphitization degree of 93.3%, and particle strength of 75.4%.
Comparative example 7
(1) Calcining petroleum raw needle coke with the volatile component of 6-10% and the ash content of less than or equal to 0.5% in a shuttle kiln, and crushing in a rolling mill to obtain an artificial graphite raw material with the volatile component of 1-3% and the D50 of 6-10 mu m; the calcining temperature is 900 ℃ and the time is 6 hours;
(2) Drying the material obtained in the step (2), mixing 5% coal pitch for granulation and depolymerization to densify the material, and obtaining secondary particles with D50 of 12.5 microns; during granulation, the heating temperature is 630 ℃ and the time is 4 hours;
(3) Graphitizing the material obtained in the step (3) at 2500 ℃ for 48h to obtain the modified artificial graphite cathode material.
The D50 of the modified artificial graphite cathode material is 12.5 mu m, and the tap density is 0.98g/cm 3 ，BET1.43m 2 The graphitization degree is 92.1% and the particle strength is 70.4%.
Effects of the embodiment
1. Degree of graphitization
The test conditions are as follows: mixing the modified artificial graphite negative electrode material and 99.9% silicon powder in a mass ratio of 2: (1.0-1.3), testing the diffraction peak of the modified artificial graphite negative electrode material by an X-ray diffractometer, recording the peak intensity value of the crystallite characteristic peak (D002) of the modified artificial graphite negative electrode material, and calculating the graphitization degree according to the following calculation formula.
2. Strength of the granules
The test conditions are as follows: the modified artificial graphite negative electrode material is placed on a sample table, is subjected to pressure maintaining for 5 seconds under the pressure of 2T, is tested for particle size, and is calculated through the following calculation formula to obtain the particle strength. Particle strength = modified artificial graphite anode material particle diameter D50 after pressure holding/modified artificial graphite anode material particle diameter D50 before pressure holding.
3. Electrochemical performance
The preparation method of the half cell comprises the following steps: the modified artificial graphite negative electrode material prepared in the above embodiment and comparative example, a conductive agent (conductive carbon black SP), sodium carboxymethylcellulose (CMC) and Styrene Butadiene Rubber (SBR) are weighed according to a mass ratio of 95. And putting the pole piece into a vacuum drying oven at the temperature of 110 ℃ for vacuum drying for 4 hours, and pressing the pole piece to prepare the negative pole. The modified artificial graphite negative electrode material prepared in the above way is used as an electrode, a metal lithium sheet is used as a counter electrode, a CR-2430 type button cell is assembled in a German Braun glove box filled with argon, and an electrolyte comprises 1M LiPF6 and a solvent (the solvent comprises Ethylene Carbonate (EC), ethyl Methyl Carbonate (EMC) and dimethyl carbonate (DMC) in a volume ratio of 1. The capacity retention rate was tested at 24 ℃ for 500 weeks at 1C charge and discharge.
The particle size, tap density, BET, graphitization degree, and particle strength of the modified artificial graphite negative electrode materials prepared in examples 1 to 4 and comparative examples 1 to 3, as well as the first discharge capacity, first coulombic efficiency, and 500-cycle capacity retention rate of the half cell were measured, and the results are shown in table 1.
TABLE 1
According to examples 1 to 7, it is understood that the modified artificial graphite anode material obtained by fluctuation within the limited range has similar particle size and high particle strength, and realizes good long cycle performance with a 500-cycle capacity retention rate of 97.5 to 98.6% under the condition of excellent primary discharge capacity and primary efficiency.
As can be seen from examples 1 to 7 and comparative example 1, if the calcination treatment is not performed, the graphitization degree is low, the first discharge capacity, the first efficiency, and the long cycle performance are all reduced, and the cycle capacity retention rate at 500 weeks is reduced by 20% or more.
As can be seen from the comparison between example 1 and comparative example 6, the long cycle performance was greatly reduced and the 500-cycle capacity retention rate was reduced by 20% or more in both cases where the modifier was used in an excessively high or excessively low amount.
As can be seen from example 1 and comparative example 6, when the firing temperature was too high, up to 1300 ℃, the first discharge capacity and the first efficiency were both slightly improved, but the long cycle performance was greatly reduced, and the 500-cycle capacity retention rate was reduced from 98.6% to 78.3%.
As is clear from examples 1 to 7 compared with comparative example 7, if the calcined product is directly bonded without modification, the long cycle performance is greatly reduced, and the 500-cycle capacity retention rate is reduced by 30% or more.
Claims (10)
1. The preparation method of the modified artificial graphite anode material is characterized by comprising the following steps of:
(1) And (3) calcining: calcining the raw coke to obtain an artificial graphite raw material; the calcining temperature is 400-1100 ℃;
(2) Modification: carrying out first heat treatment on a mixture A of a modifier and the artificial graphite raw material; the modifier can modify the surface of the artificial graphite raw material; the carbon residue of the modifier is 1-3%;
(3) Bonding: carrying out second heat treatment on the mixture B of the adhesive and the material obtained in the step (2);
(4) Graphitizing: and (4) graphitizing the material obtained in the step (3).
2. The method for preparing the modified artificial graphite anode material according to claim 1, wherein in the step (1), the calcining temperature is 400-1000 ℃;
and/or in the step (1), the calcining time is 4-8 h;
and/or, in the step (2), the carbon residue of the modifier is 1%, 2% or 3%.
3. The method for preparing the modified artificial graphite anode material according to claim 1, wherein in the step (1), the raw coke is one or more of petroleum raw coke, petroleum raw needle coke, petroleum calcined raw coke, petroleum calcined needle coke, coal raw coke, coal calcined needle coke and coal calcined needle coke, preferably one or more of petroleum raw coke, petroleum raw coke and coal raw needle coke;
and/or, in the step (1), the volatile content of the raw coke is less than or equal to 18 percent, preferably 6 to 13 percent, such as 6 to 10 percent;
and/or in the step (1), the ash content of the raw coke is less than or equal to 1.0 percent, and is preferably less than or equal to 0.5 percent.
4. The method for preparing the modified artificial graphite anode material according to claim 1, wherein in the step (1), the volatility of the artificial graphite raw material is 1 to 6%, preferably 1 to 3%;
and/or in the step (1), after the calcination, the operation of crushing is also included;
and/or, in the step (1), the particle size D50 of the artificial graphite raw material is 6-11 μm, for example, 6-10 μm.
5. The method for preparing the modified artificial graphite anode material according to claim 1, wherein in the step (2), the modifier is a substance containing polar groups, such as one or more of coal tar, ethylene tar, pitch, monosaccharide and polysaccharide; the polysaccharide is preferably starch;
and/or in the step (2), the using amount of the modifier is 2-15%; % is the mass percentage of the modifier in the artificial graphite raw material.
6. The method for preparing the modified artificial graphite anode material according to claim 1, wherein in the step (2), the temperature of the first heat treatment is 300 to 650 ℃;
and/or in the step (2), the time of the first heat treatment is 2-6 h.
7. The method for preparing the modified artificial graphite anode material according to claim 1, wherein in the step (3), the binder is one or more of petroleum asphalt, coal asphalt and resin;
and/or in the step (3), the dosage of the adhesive is 2-8%, and the% refers to the mass percentage of the adhesive in the mixture B;
and/or in the step (3), the temperature of the second heat treatment is 450-700 ℃;
and/or in the step (3), the time of the second heat treatment is 2-6 h;
and/or, in the step (3), after the second heat treatment, the operation of depolymerization is also included;
and/or in the step (3), after the second heat treatment, the D50 of the material is 13-18 μm.
8. The method for preparing the modified artificial graphite anode material according to claim 1, wherein in the step (4), the graphitization treatment temperature is 2300 to 2600 ℃;
and/or in the step (4), the graphitization treatment time is 36-60 h.
9. A modified artificial graphite anode material, characterized in that it is produced by the method for producing a modified artificial graphite anode material according to any one of claims 1 to 8.
10. The modified artificial graphite anode material according to claim 9, wherein the degree of graphitization of the modified artificial graphite anode material is 91 to 93%;
and/or the particle strength of the modified artificial graphite anode material is 74-92%.
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