CN113233451A - Modified artificial graphite material, preparation method and application thereof, and lithium ion battery - Google Patents
Modified artificial graphite material, preparation method and application thereof, and lithium ion battery Download PDFInfo
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- 229910021383 artificial graphite Inorganic materials 0.000 title claims abstract description 135
- 239000007770 graphite material Substances 0.000 title claims abstract description 54
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- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 26
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- 239000011248 coating agent Substances 0.000 claims abstract description 33
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- 239000002253 acid Substances 0.000 claims abstract description 21
- 229910021385 hard carbon Inorganic materials 0.000 claims abstract description 16
- 239000002994 raw material Substances 0.000 claims abstract description 16
- 238000001035 drying Methods 0.000 claims abstract description 10
- 238000006386 neutralization reaction Methods 0.000 claims abstract description 7
- 239000007773 negative electrode material Substances 0.000 claims abstract description 5
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- 238000010000 carbonizing Methods 0.000 claims abstract description 3
- 239000002245 particle Substances 0.000 claims description 40
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 36
- 239000000243 solution Substances 0.000 claims description 30
- 238000003763 carbonization Methods 0.000 claims description 19
- 238000007254 oxidation reaction Methods 0.000 claims description 19
- 230000003647 oxidation Effects 0.000 claims description 18
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical group [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 17
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 17
- 238000005087 graphitization Methods 0.000 claims description 17
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- 238000000034 method Methods 0.000 claims description 12
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- 239000012670 alkaline solution Substances 0.000 description 1
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- 239000003153 chemical reaction reagent Substances 0.000 description 1
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- 229910052751 metal Inorganic materials 0.000 description 1
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/20—Graphite
- C01B32/205—Preparation
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/20—Graphite
- C01B32/21—After-treatment
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
-
- 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 material, a preparation method and application thereof, and a lithium ion battery. The preparation method comprises the following steps: s1, carrying out heat treatment on the artificial graphite raw material to obtain an artificial graphite A material; s2, graphitizing the artificial graphite A material to obtain an artificial graphite B material; s3, oxidizing the artificial graphite B material by using an acid solution, and drying after neutralization to obtain an artificial graphite C material; s4, coating the artificial graphite C material by adopting a hard carbon source to obtain an artificial graphite D material; and S5, carbonizing the artificial graphite D material, and performing post-treatment to obtain the artificial graphite D material. The preparation method is simple and controllable, the prepared modified artificial graphite material has rich microporous structures, is beneficial to rapid de-intercalation of lithium ions, and a lithium ion battery taking the modified artificial graphite material as a negative electrode material has the advantages of good rapid charging performance, long cycle life, high safety performance and excellent comprehensive performance.
Description
Technical Field
The invention relates to a modified artificial graphite material, a preparation method and application thereof, and a lithium ion battery.
Background
Lithium ion secondary batteries are rapidly developing as an energy storage device in today's society. Lithium ion secondary batteries are widely used at the present stage: in portable electronic products such as smart phones, tablet computers, digital cameras and the like, power lithium ion batteries are rapidly developed with the subsequent rapid development requirements of electric vehicles. From the direction of the future market for lithium ion batteries: the fast charging type lithium ion battery will become an important direction of the lithium ion battery. Improving the quick charge performance of the artificial graphite cathode material is an important research direction for improving the quick charge performance of the lithium ion battery. The current solution of the quick charging technology is mainly as follows: (1) regulating and controlling a desolvation process of lithium ions; (2) reducing the particle size of graphite; (3) constructing an ion channel on the surface of graphite; (4) opening up an embedded point in the graphite; (5) and (5) optimizing the material structure. Among these solutions, the construction of graphite surface ion channels is currently a major desired strategy for downstream enterprises. At present, the main method for constructing the surface ion channel is an oxidation method, and the mature oxidation process comprises air oxidation and alkali oxidation. The air oxidation has the defects of uncontrollable oxidation and uncontrollable oxidation degree, so that an ideal graphite surface ion channel cannot be constructed. The drawback of alkaline oxidation is that after mixing the alkali with the artificial graphite, the oxidation step needs to be carried out at a higher temperature and the preparation conditions are harsh.
Disclosure of Invention
The invention provides a modified artificial graphite material, a preparation method and application thereof and a lithium battery, aiming at solving the defect of poor quick charging performance of an artificial graphite cathode material in the prior art. The preparation method of the modified artificial graphite material is simple and controllable, the prepared modified artificial graphite material has rich microporous structures, is beneficial to rapid de-intercalation of lithium ions, and a lithium ion battery taking the modified artificial graphite material as a negative electrode material has the advantages of good quick charge performance, long cycle life, high safety performance and excellent comprehensive performance.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a preparation method of a modified artificial graphite material, which comprises the following steps:
s1, carrying out heat treatment on the artificial graphite raw material to obtain an artificial graphite A material; the temperature of the heat treatment is 400-700 ℃;
s2, graphitizing the artificial graphite A material to obtain an artificial graphite B material;
s3, oxidizing the artificial graphite B material by using an acid solution, and drying after neutralization to obtain an artificial graphite C material;
s4, coating the artificial graphite C material by adopting a hard carbon source to obtain an artificial graphite D material;
and S5, carbonizing the artificial graphite D material, and performing post-treatment to obtain the artificial graphite D material.
In the present invention, in step S1, the artificial graphite raw material may be a raw material conventionally used in the art for preparing artificial graphite, for example, petroleum green coke, calcined petroleum coke, crude needle coke or calcined needle coke, preferably petroleum green coke, and the volatile content of the petroleum green coke may be 10-13%.
In step S1, it is preferable that the artificial graphite raw material is pulverized and shaped before the heat treatment.
Wherein, the pulverization can be carried out by a pulverizer which is conventional in the field, and is preferably a mechanical mill, such as a mechanical mill 150 or a mechanical mill 500. The pulverization yield of the pulverization is preferably 60.0 to 80.0%. Preferably, the particle size D50 of the crushed artificial graphite raw material is 6.5-8.5 μm.
Wherein the shaping can be performed using a shaping machine conventional in the art, such as a batch shaping machine 800. The shaping aims to remove fine powder and improve the sphericity of the raw material. Preferably, the particle size of the artificial graphite raw material after shaping satisfies the following conditions: the minimum particle diameter Dmin is more than or equal to 1.0 μm, and the particle diameter D50 is 7.0-9.0 μm.
In step S1, the heat treatment may be performed as is conventional in the art, and may be performed by holding at a certain temperature. The purpose of heat-treating the raw material for the artificial graphite is to bind the pellets by the volatile components of the material itself. The volatile component of the artificial graphite A material is preferably 6-8%. The particle diameter D50 of the artificial graphite A material is preferably 15.0-17.0 μm, such as 16.0 μm.
In step S1, the heat-preserving time of the heat treatment may be 2 to 9 hours, preferably 3 to 8 hours, for example 6 hours.
In step S1, the heat treatment is preferably performed under an inert gas atmosphere, which may be, for example, a nitrogen gas atmosphere or an inert gas atmosphere.
In step S1, the heat treatment may be performed in a heat treatment apparatus conventional in the art, preferably a horizontal coating kettle, such as a horizontal coating kettle WHR-8m3Or WHR-10m3. When the heat treatment is performed in a horizontal coating kettle, the rotation speed of the horizontal coating kettle may be 10 to 30Hz, for example, 25 Hz.
In the present invention, in step S2, the graphitization treatment may be performed conventionally in the art, and generally includes that the material to be graphitized is heated by applying electricity, and after a certain temperature (graphitization temperature) is reached, the electricity is stopped to naturally cool the material (heat preservation process), so as to graphitize the material. The graphitization treatment may be performed in a graphitization furnace conventional in the art, such as a graphitization crucible furnace.
The graphitization temperature of the graphitization treatment can be 2800-3200 ℃, and preferably 2900 ℃.
The heat preservation time of the graphitization treatment can be 12-30 days, and preferably 15 days or 20 days.
The power transmission time of the graphitization treatment can be 16-40 h.
In step S2, the artificial graphite B is secondary graphite particles. The particle size D50 of the artificial graphite B material is preferably 16.0-18 μm, for example 17.0 μm.
In the invention, in step S3, the oxidation treatment of the artificial graphite B material with an acid solution can form a rich microporous structure on the surface of the material. The acid solution may be an acid solution having an oxidizing ability, which is conventional in the art. The acid solution can be nitric acid, sulfuric acid or a mixed solution of the nitric acid and the sulfuric acid, and is preferably a mixed solution of the nitric acid and the sulfuric acid; alternatively, the acid solution may be a mixed solution of potassium permanganate and sulfuric acid. Wherein the molar concentration of the nitric acid can be 10-14.4 mol/L, for example, 8mol/L or 14 mol/L. The molar concentration of the sulfuric acid can be 10-18.4 mol/L, such as 16 mol/L. The molar concentration here is the molar concentration of nitric acid or sulfuric acid before mixing. When the acid solution is a mixed solution of the nitric acid and the sulfuric acid, a volume ratio of the nitric acid to the sulfuric acid may be 1: (0.05-20), preferably 1: 1.
In step S3, the volume ratio of the artificial graphite B material to the acid solution may be 1: (1-5), preferably 1: 2.
In step S3, the oxidation treatment may be performed at normal temperature.
In step S3, the time of the oxidation treatment may be 5 to 20 hours, preferably 10 hours.
In step S3, the oxidation treatment may be performed in a pickling tank conventional in the art.
In step S3, the neutralization may be conventional in the art and generally involves transferring the oxidatively treated material to an alkaline solution. The alkali solution used for the neutralization may be an alkali metal hydroxide solution, such as KOH solution. Wherein, the molar concentration of the KOH solution is preferably 1 mol/L.
In step S3, the drying may be performed using equipment conventional in the art, such as a push plate type carbonization furnace. The drying temperature can be 100-300 ℃, and preferably 120 ℃. The drying time can be 5-15 h.
In the present invention, in step S4, the coating process may be performed as conventional in the art, and generally includes mixing the artificial graphite C material and the hard carbon source, and then performing a heat treatment to uniformly coat the hard carbon source on the surface of the artificial graphite C material.
In step S4, the hard carbon source may be a biomass polymer material or a synthetic polymer material, preferably starch, which is conventional in the art.
In step S4, the mass ratio of the artificial graphite C material to the hard carbon source may be 100: (2-10), preferably 100: 5.
In step S4, the coating treatment may be performed by a coating apparatus conventional in the art, such as a horizontal coating kettle, e.g., a horizontal coating kettle WHR-8m3Or WHR-10m3. When the coating is performed in the horizontal coating kettle, the rotating speed of the horizontal coating kettle can be 10-30 Hz, such as 25 Hz.
Wherein the mixing time is preferably 30-90 min. The rotating speed of the mixed materials is preferably 50 r/min.
Wherein the temperature of the heat treatment in the coating treatment may be 200 to 700 ℃, preferably 200 to 500 ℃. The time of the heat treatment can be 3-9 h, such as 7 h.
In step S4, the particle diameter D50 of the artificial graphite D material is preferably 14.5 to 16.5 μm, for example, 15.5 μm.
In the present invention, in step S5, the carbonization process may be performed as conventional in the art, and generally includes maintaining the temperature at a certain temperature to carbonize the hard carbon source coated on the surface of the artificial graphite D. The external hard carbon source is carbonized to form a uniform hard carbon shell, and the inner layer is uniformly coated, so that the specific surface area of the material can be further improved.
In step S5, the carbonization treatment may be performed by using a carbonization furnace conventional in the art, such as a roller-type carbonization furnace.
In step S5, the carbonization treatment is preferably performed under an inert atmosphere.
In step S5, the temperature of the carbonization treatment may be 900-1300 ℃, preferably 1150-1200 ℃. The carbonization treatment time can be 6-20 h. For example, the carbonization treatment is carried out at a constant temperature of 900 for 10 hours.
In step S5, the post-treatment may be performed by operations conventional in the art, and generally includes mixing, sieving, and demagnetizing. Preferably, the post-processing comprises one-time mixing, one-time screening and one-time demagnetizing.
Wherein the mixing and sieving may be performed using equipment conventional in the art, preferably a ribbon blender, such as a CDLW-8000 ribbon blender.
Wherein the rotating speed of the equipment during mixing is 10-30 HZ, such as 20 HZ. The mixing time can be 0.5-3 h, such as 50min or 2 h.
Wherein, the demagnetization can be carried out by adopting the method and the equipment which are conventional in the field, such as a domestic demagnetization machine. The purpose of said demagnetization is to further remove magnetic substances that may be present in the material, such as magnetic substances introduced in the coating process.
The invention provides a modified artificial graphite material, which is prepared by the preparation method of the modified artificial graphite.
In the invention, the particles of the modified artificial graphite material are of a core-shell structure and comprise a graphite core and a hard carbon shell, wherein the graphite core is of a microporous structure.
In the invention, the particle size D50 of the modified artificial graphite material is preferably 14.0-16.0 μm. The particle size D10 of the modified artificial graphite material is preferably 7.0-9.0 μm. The particle size D90 of the modified artificial graphite material is preferably 25.0-36.0 μm.
In the invention, the tap density of the modified artificial graphite material is more than or equal to 0.95g/cm3Preferably ≥ 1.0g/cm3。
In the invention, the specific surface area BET of the modified artificial graphite material is more than or equal to 2.0m2Per g, preferably BET ≥ 4.0m2/g。
The invention also provides a lithium ion battery, and the negative electrode of the lithium ion battery comprises the modified artificial graphite material.
The invention also provides application of the modified artificial graphite material as a negative electrode material in a lithium ion battery.
In the invention, the lithium ion battery is preferably used for a power battery of a passenger car.
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:
the invention provides a simple and controllable preparation method of a modified artificial graphite material, which is characterized in that the artificial graphite is oxidized and modified at normal temperature to construct an ion channel on the surface of the graphite, and the rich microporous structure and the hard carbon coating synergistic effect on the surface of the artificial graphite are utilized, so that the material has a larger specific surface area compared with the conventional artificial graphite, a large number of lithium ion channels are arranged on the surface, the rapid de-intercalation of lithium ions is facilitated, the permeation of electrolyte is facilitated, and the characteristic of high rapid charging can be achieved when the material is applied to a lithium ion battery. Specifically, the method comprises the following steps:
(1) the modified artificial graphite material has large specific surface area (BET is more than or equal to 2.0 m)2Per g, preferably BET ≥ 4.0m2(g), narrow particle size distribution (D50 is 14.0-16.0 μm); high tap density (not less than 0.95 g/cm)3)。
(2) The lithium ion battery using the modified artificial graphite material as the negative electrode material has the advantages of good quick charge performance, high discharge capacity (more than or equal to 350mAh/g), high first coulombic efficiency (more than or equal to 91%), long cycle life (more than 85% of capacity retention rate in 500 weeks), high safety performance and excellent comprehensive performance.
Drawings
Fig. 1 is an SEM image of a modified artificial graphite material of example 1 of the present invention.
Figure 2 is a malvern particle size volume distribution plot of the modified artificial graphite material of example 1 of the present invention.
Fig. 3 is a charge/discharge curve diagram of a half cell according to example 1 in example 3, which is an effect of the present invention.
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.
Materials or equipment used in the following examples, comparative examples and effect examples are shown in table 1.
TABLE 1
Example 1
A preparation method of a modified artificial graphite material comprises the following specific steps:
s1, crushing the massive petroleum coke (the average grain diameter D50 is 8.5 mu m) by a mechanical mill 500, wherein the crushing efficiency is 70%; then, a batch type shaping machine 800 is adopted to carry out shaping and fine powder removal to obtain an artificial graphite raw material (the average particle size D50 is 8.0 mu m, and the minimum particle size Dmin is 1.2 mu m);
adding the artificial graphite raw material into a horizontal coating kettle with a heat preservation section at 400 ℃, and preserving heat for 6 hours in a nitrogen atmosphere to obtain an artificial graphite A material with the average particle size D50 of 16.0 mu m.
S2, adding the artificial graphite A material obtained in the step S1 into a graphitization crucible furnace, electrifying and heating to 2900 ℃, electrifying for 40h, then stopping electrifying, and keeping the temperature for 30 days to obtain an artificial graphite B material (secondary graphite particles) with the average particle size D50 of 14.0 μm.
S3, adding the artificial graphite B material obtained in the step S2 and an acid solution into a pickling tank, treating at normal temperature for 10 hours, and oxidizing the artificial graphite B material; wherein the acid solution is a mixed solution of nitric acid (14mol/L) and sulfuric acid (16mol/L), the volume ratio of the nitric acid to the sulfuric acid is 1:1, and the volume ratio of the artificial graphite B material to the acid solution is 1: 2;
transferring the material obtained by oxidation into KOH solution (1mol/L) for neutralization, and then adding the neutralized material into a push plate type carbonization furnace for drying in an air atmosphere at 120 ℃ for 5 hours to obtain the artificial graphite C material.
S4, adding the artificial graphite C material obtained in the step S3 and starch into a horizontal coating kettle WHR-8m at a mass ratio of 100:53And coating at 700 deg.c for 7 hr at 30Hz to obtain artificial graphite D material with particle size D50 of 15.5 microns.
S5, adding the artificial graphite D material obtained in the step S4 into a roller-type carbonization furnace, and carrying out constant-temperature treatment at 900 ℃ for 10 hours under the protection of nitrogen atmosphere;
and (3) mixing the carbonized materials in a spiral belt type finished product mixer for 50min, then screening once, and then demagnetizing once by using a demagnetizing machine to obtain the modified artificial graphite material with the particle size D50 of 15.13 mu m.
Example 2
Example 2 differs from example 1 in that: in step S3, the molar concentration of nitric acid in the acid solution was 8mol/L, and the other conditions were not changed.
Example 3
Example 3 differs from example 1 in that: the mass ratio of the artificial graphite C material to the starch in the step S4 is 100: 10, other conditions were unchanged.
Example 4
Example 4 differs from example 1 in that: in step S3, the acid solution was nitric acid (14mol/L), and the other conditions were unchanged.
Example 5
Example 5 differs from example 1 in that: in step S3, the acid solution was sulfuric acid (16mol/L), and the other conditions were unchanged.
Comparative example 1
Comparative example 1 differs from example 1 in that: step S4 is performed directly using the artificial graphite B material obtained in step S2 without step S3.
Effect example 1
The modified artificial graphite material prepared in example 1 was characterized by an electron scanning electron microscope, and the SEM image obtained is shown in fig. 1. It is apparent that example 1 produces a modified artificial graphite material having a typical secondary particle structure.
Effect example 2
The modified artificial graphite materials obtained in the examples and comparative examples were respectively tested for particle size, tap density, specific surface area, etc. according to methods conventional in the art, and the results are shown in Table 2.
The name and model of the instrument used for the test are as follows:
particle size, laser particle size distribution instrument MS 3000;
tap density, vibrometer TF-100B;
specific surface area, specific surface area determinator NOVATouch 2000;
as can be seen from Table 2, the present inventionThe specific surface area of the modified artificial graphite material prepared in each example is large (BET is more than or equal to 2.0 m)2In g) higher than in comparative example 1. Comparative example 1 does not carry out acid oxidation treatment, and cannot reach the structural design characteristics of the invention, namely, the material surface has no microporous structure and can only reach the indexes of a conventional artificial graphite clad product. Although examples 4 and 5 were also acid-oxidation-treated, the oxidation ability of nitric acid and sulfuric acid alone was relatively weak and the BET was relatively small, as compared with examples 1 to 3.
In addition, the particle size distribution of the modified artificial graphite materials prepared in the examples is narrow (D50 is 14.0-16.0 μm). Figure 2 is a malvern particle size volume distribution plot of the modified artificial graphite material obtained in example 1, and it is evident that the particle size distribution is narrow, with no fines and large particles, which corresponds to the SEM results. In addition, the modified artificial graphite material prepared in each example has high tap density (not less than 0.95 g/cm)3) And the processing performance is good.
Effect example 3
The modified artificial graphite materials in each example and comparative example were compared by half-cell test methods for discharge capacity, first coulombic efficiency, and 1C/1C 500-cycle retention rate tests.
Preparing a half cell: weighing the modified artificial graphite material, the conductive carbon black SP, the CMC and the SBR according to a mass ratio of 96:1:1:2, uniformly stirring in water to prepare negative electrode slurry, uniformly coating the two sides of the negative electrode slurry on copper foil by using a coater, putting the coated electrode piece into a vacuum drying oven at 100 ℃ for vacuum drying for 12 hours, and pressing the electrode piece to prepare the electrode, wherein the compaction density is 1.6-1.8 g/cm3And the compacted density is the surface density/(the thickness of the rolled pole piece-the thickness of the current collector).
The electrode is taken as a negative electrode, a metal lithium sheet is taken as a counter electrode, and the electrolyte is 1M LiPF6+ EC: EMC: DMC 1:1 (volume ratio), and CR-2430 button cell type batteries were assembled in an argon-filled German Braun glove box.
Electrochemical performance tests were performed on an electrochemical test cabinet (blue cell) with a charge-discharge voltage range of 0.005V to 2.0V and a charge-discharge rate of 0.1C, and the test results are shown in table 2.
TABLE 2
As can be seen from the electrical property test results in Table 2, the modified artificial graphite materials prepared in the examples have high discharge capacity (350 mAh/g or more) and first coulombic efficiency (91% or more), and show excellent cycling stability of not less than 85.0% in 500 cycles of 1C charging and discharging. Fig. 3 shows the charge/discharge curve of the half cell according to example 1.
Effect example 4
The modified artificial graphite materials in the examples and the comparative examples were subjected to a rate discharge test by a half-cell test method, and the test procedure was as follows:
discharging to 5mV with a constant current of 0.6mA in the first period, then discharging at a constant voltage, wherein the cut-off current is 0.06mA, and charging to 2V at a constant current of 0.1C; a constant current of 0.1C was discharged to 5mV (representing a capacity of "0.1C constant") and then discharged at constant voltage (representing a capacity of "0.1C total"), with a cutoff current of 0.06mA, with a 0.2C constant current charge to 2V; then multiplying power discharge current is 0.2C, 0.5C, 1C, 2C and 3C; after 3C, the current returns to 0.2C, and the multiplying power charging current is 0.1C.
Table 3 shows the rate performance test results, i.e., constant current ratio, i.e., constant current charging capacity ("constant")/total charging capacity ("total"), where the total charging capacity is constant current charging capacity + constant voltage charging capacity, at different rates of discharge current. It can be seen visually that each example has excellent rate capability, the capacity retention rate of 3C/0.1C of the example is more than 8%, and the capacity retention rate of 3C/0.1C of the preferred examples 1-3 is more than 16%, which is consistent with the structural design.
TABLE 3
Claims (10)
1. A preparation method of a modified artificial graphite material comprises the following steps:
s1, carrying out heat treatment on the artificial graphite raw material to obtain an artificial graphite A material; the temperature of the heat treatment is 400-700 ℃;
s2, graphitizing the artificial graphite A material to obtain an artificial graphite B material;
s3, oxidizing the artificial graphite B material by using an acid solution, and drying after neutralization to obtain an artificial graphite C material;
s4, coating the artificial graphite C material by adopting a hard carbon source to obtain an artificial graphite D material;
and S5, carbonizing the artificial graphite D material, and performing post-treatment to obtain the artificial graphite D material.
2. The preparation method of the modified artificial graphite material according to claim 1, wherein in step S1, the artificial graphite raw material is petroleum raw coke, calcined petroleum coke, raw needle coke or calcined needle coke, preferably petroleum raw coke, and the volatile content of the petroleum raw coke is preferably 10-13%;
and/or, in step S1, before the heat treatment, crushing and shaping the artificial graphite raw material;
wherein, the pulverizer used for pulverizing is preferably a mechanical mill, such as a mechanical mill 150 or a mechanical mill 500; the pulverizing yield of the pulverization is preferably 60.0-80.0%; the particle size D50 of the crushed artificial graphite raw material is preferably 6.5-8.5 μm;
the shaping machine used for shaping is preferably an intermittent shaping machine 800; the particle size of the shaped artificial graphite raw material preferably satisfies: the minimum particle size Dmin is more than or equal to 1.0 mu m, and the particle size D50 is 7.0-9.0 mu m;
and/or in the step S1, the volatile matter of the artificial graphite A material is 6-8%;
and/or in step S1, the particle size D50 of the artificial graphite A material is 15.0-17.0 μm, such as 16.0 μm;
and/or in step S1, the heat treatment is carried out for 2-9 h, preferably 3-8 h, for example 6 h;
and/or, in step S1, the heat treatment is performed under an inert gas atmosphere, such as a nitrogen gas atmosphere or an inert gas atmosphere;
and/or, in step S1, the heat treatment equipment for the heat treatment is a horizontal coating kettle, such as a horizontal coating kettle WHR-8m3Or WHR-10m3(ii) a When the heat treatment is performed in a horizontal coating kettle, the rotation speed of the horizontal coating kettle is preferably 10 to 30Hz, for example, 25 Hz.
3. The method for producing a modified artificial graphite material according to claim 1, wherein in step S2, the graphitization treatment is performed in a graphitization furnace, preferably a graphitization crucible furnace;
and/or in step S2, the graphitization temperature of the graphitization treatment is 2800-3200 ℃;
and/or in step S2, the heat preservation time of the graphitization treatment is 12-30 days, preferably 15 days or 20 days;
and/or in step S2, the power transmission time of the graphitization treatment is 16-40 h;
and/or in step S2, the particle size D50 of the artificial graphite B material is 16.0-18 μm, such as 17.0 μm.
4. The method for preparing a modified artificial graphite material according to claim 1, wherein in step S3, the acid solution is nitric acid, sulfuric acid or a mixed solution of both, preferably a mixed solution of nitric acid and sulfuric acid; or the acid solution is a mixed solution of potassium permanganate and sulfuric acid;
wherein the molar concentration of the nitric acid is preferably 10-14.4 mol/L, such as 8mol/L or 14 mol/L; the molar concentration of the sulfuric acid is preferably 10-18.4 mol/L, such as 16 mol/L; when the acid solution is a mixed solution of the nitric acid and the sulfuric acid, the volume ratio of the nitric acid to the sulfuric acid is preferably 1: (0.05-20), preferably 1: 1;
and/or in step S3, the volume ratio of the artificial graphite B material to the acid solution is 1: (1-5), preferably 1: 2;
and/or, in step S3, the oxidation treatment may be performed at normal temperature;
and/or in step S3, the time of the oxidation treatment is 5 to 20 hours, preferably 10 hours;
and/or, in step S3, the alkali solution used for neutralization is an alkali metal hydroxide solution, such as a KOH solution; wherein, the molar concentration of the KOH solution is preferably 1 mol/L;
and/or in step S3, the drying equipment is a push plate type carbonization furnace; the drying temperature is 100-300 ℃, and preferably 120 ℃; the drying time is 5-15 h.
5. The method for preparing a modified artificial graphite material according to claim 1, wherein the coating treatment comprises mixing the artificial graphite C material and the hard carbon source and then performing heat treatment in step S4;
and/or, in step S4, the hard carbon source is a biomass polymer material or a synthetic polymer material, preferably starch;
and/or in step S4, the mass ratio of the artificial graphite C material to the hard carbon source is 100: (2-10), preferably 100: 5;
and/or in step S4, the coating equipment for coating treatment is a horizontal coating kettle, such as a horizontal coating kettle WHR-8m3Or WHR-10m3(ii) a When the coating is carried out in the horizontal coating kettle, the rotating speed of the horizontal coating kettle is preferably 10-30 Hz, such as 25 Hz;
wherein the mixing time is preferably 30-90 min; the rotating speed of the mixed material is preferably 50 r/min;
wherein the temperature of the heat treatment in the coating treatment is preferably 200 to 700 ℃, more preferably 200 to 500 ℃; the time of the heat treatment is preferably 3 to 9 hours, such as 7 hours;
and/or in the step S4, the particle size D50 of the artificial graphite D material is 14.5-16.5 μm, such as 15.5 μm.
6. The method for preparing a modified artificial graphite material according to claim 1, wherein in step S5, the carbonization furnace used in the carbonization treatment is a roller bed type carbonization furnace;
and/or, in step S5, the carbonization treatment is performed under an inert atmosphere;
and/or in step S5, the temperature of the carbonization treatment is 900-1300 ℃, preferably 1150-1200 ℃; the carbonization treatment time is 6-20 h; preferably, the carbonization treatment is carried out for 10 hours at the constant temperature of 900 ℃;
and/or in step S5, the post-processing comprises mixing, screening and demagnetizing; preferably, the post-processing comprises one-time mixing, one-time screening and one-time demagnetizing.
7. A modified artificial graphite material produced by the method for producing modified artificial graphite according to any one of claims 1 to 6.
8. The modified artificial graphite material according to claim 7, wherein the particles of the modified artificial graphite material are of a core-shell structure comprising a graphite core and a hard carbon shell, the graphite core having a microporous structure;
and/or the particle size D50 of the modified artificial graphite material is 14.0-16.0 μm;
and/or the particle size D10 of the modified artificial graphite material is 7.0-9.0 μm;
and/or the particle size D90 of the modified artificial graphite material is 25.0-36.0 μm;
and/or the tap density of the modified artificial graphite material is more than or equal to 0.95g/cm3Preferably ≥ 1.0g/cm3；
And/or the specific surface area BET of the modified artificial graphite material is more than or equal to 2.0m2Per g, preferably BET ≥ 4.0m2/g。
9. A lithium ion battery having a negative electrode comprising the modified artificial graphite material of claim 7 or 8.
10. Use of the modified artificial graphite material of claim 7 or 8 as a negative electrode material in a lithium ion battery.
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