CN115215335A - Modified graphite and preparation method and application thereof - Google Patents

Modified graphite and preparation method and application thereof Download PDF

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CN115215335A
CN115215335A CN202211054746.1A CN202211054746A CN115215335A CN 115215335 A CN115215335 A CN 115215335A CN 202211054746 A CN202211054746 A CN 202211054746A CN 115215335 A CN115215335 A CN 115215335A
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graphite
modified graphite
modified
carbon dioxide
purified
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岳敏
王露琪
杜宁
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Zhejiang Coyi New Energy Co ltd
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    • C—CHEMISTRY; METALLURGY
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    • C01B32/00—Carbon; Compounds thereof
    • C01B32/20—Graphite
    • C01B32/21—After-treatment
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H01G11/32—Carbon-based
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0224—Electrodes
    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • 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
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • 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
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/96—Carbon-based electrodes
    • 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 provides modified graphite and a preparation method and application thereof, wherein the preparation method comprises the following steps: sintering the purified graphite for 12-20 h at 1200-2000 ℃ in the atmosphere of carbon dioxide to obtain the modified graphite. According to the preparation method of the modified graphite, the purified graphite is sintered in the carbon dioxide atmosphere, so that the surface of the purified graphite is provided with holes, and lithium insertion sites are increased, thereby being beneficial to improving the capacity of a lithium ion battery; the preparation method improves the pH value of the purified graphite, and avoids using a washing mode to improve the pH value, thereby avoiding the discharge of a large amount of acid liquor, saving the production cost and improving the production efficiency; meanwhile, compared with sintering in an oxygen atmosphere, sintering in a carbon dioxide atmosphere does not cause the increase of the specific surface area of the spherical graphite, so that the loss of the cycle performance of the battery is not caused.

Description

Modified graphite and preparation method and application thereof
Technical Field
The invention belongs to the technical field of lithium ion batteries, relates to a preparation method of modified graphite, and particularly relates to the modified graphite and the preparation method and application thereof.
Background
The lithium ion battery has the advantages of high working voltage, large specific energy, light weight, small volume, long cycle life, no memory effect, quick charge and discharge, no environmental pollution and the like, and is widely applied to various devices. Currently, commercial lithium ion battery negative electrode materials are mainly various carbon-based materials. The graphite material as the negative electrode material of the lithium ion battery has the advantages of high specific capacity, low price, rich sources and the like. Therefore, the lithium ion battery anode material is considered to be a promising lithium ion battery anode material, and the market amount is continuously increased. The composite material has a good laminated structure, low embedding potential, excellent embedding/de-embedding performance and a good voltage platform.
Although the existing graphite purification methods are more, HF and HNO are introduced in the purification process of most of the existing graphite purification methods 3 The HCl is a large amount of strong acid, so that the carbon content of the natural graphite is increased, and the problem that the pH value of the purified natural graphite is low is caused; in order to solve the problem, the purified natural graphite needs to be oxidized or washed by a large amount of deionized water, a large amount of acid water is additionally generated besides the increase of the production cost, the requirement of environmental protection is not met, the additionally generated sewage needs to be discharged after reaching the standard, and the cost of a large amount of sewage treatment and the time cost are increased.
CN103318871B discloses a preparation method for synthesizing a graphitized porous carbon material by using activated carbon as a raw material, and relates to a preparation method for synthesizing a graphitized porous carbon material. The invention aims to solve the technical problems of poor conductivity, small pore diameter, complex preparation process, high synthesis temperature and unsuitability for large-scale production of the existing activated carbon material. The preparation method of the invention is as follows: 1. dispersing activated carbon; 2. coordination bonding of activated carbon and catalyst; 3. curing the complex; 4. heat treatment; 5. and (4) acid treatment. However, in the method for preparing a synthetic graphitized porous carbon material, the carbon material obtained by the acid reflux method is washed with distilled water to a pH of 6 to 7, which not only increases the production cost, but also generates a large amount of acid water.
CN105375030B discloses a preparation method of a graphite negative electrode material of a low-temperature high-rate power battery, which comprises the following steps: the porous graphite secondary particle agglomerate is obtained by agglomerating and granulating by using a simple and efficient spray drying method, and then secondary surface coating is carried out to obtain the low-temperature graphite cathode material for the lithium ion battery. In the structure of the negative electrode material, graphite modified by a micro-expansion technology is prefabricated with a certain pre-expansion space in particles, so that the damage of a core-shell structure caused by graphite expansion is effectively inhibited in the charging and discharging processes, the core-shell structure is better maintained, and particularly, the graphite has better cycle stability under the condition of quick charging and discharging. After the micron graphite is granulated, the small primary graphite particles are agglomerated into secondary particles in a porous carbon matrix in the core, the isotropy degree of the secondary particles is high, unidirectional expansion and shrinkage caused by charge and discharge are small, and therefore the low-temperature lithium intercalation performance and rate performance of the low-temperature high-rate graphite negative electrode material are greatly improved. Similarly, the preparation method of the graphite negative electrode material of the low-temperature high-rate power battery also enables the pH to reach 6.8-7.2 by washing, and the treatment cost of the generated acid water is high.
CN113363447A discloses a preparation method of a hard carbon composite graphite negative electrode material, which comprises the following steps: mixing mesocarbon microbeads and a digesting agent to obtain a component A, digesting at the temperature of 100-300 ℃ for 1-10 h, repeatedly washing to ensure that the pH = 6-7 of the digested mixed material, and then drying in a drying oven at the temperature of 100 ℃ for 5h to prepare carbon skeleton spherical graphite; step two, mixing the hard carbon precursor with the carbon skeleton obtained in the step one, then transferring the mixture into high-temperature fusion equipment with the temperature of 300-800 ℃ and under the protection of inert atmosphere for fusion for 1-5 h, and cooling the mixture to obtain a component B; and step three, putting the component B into carbonization equipment, introducing inert atmosphere, carbonizing at 850-1400 ℃ for 1-10 h, cooling to room temperature, and sieving to obtain the hard carbon composite graphite cathode material. Similarly, in the method for producing the hard carbon composite graphite negative electrode material, the pH is adjusted to 6 to 7 by washing, and acid water is also generated at a high treatment cost.
The preparation methods of the modified graphite disclosed at present have certain defects, and have the problems of high production cost, generation of a large amount of acid water which is difficult to treat and complex production process. Therefore, development and design of a novel modified graphite and a preparation method thereof are of great importance.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide modified graphite and a preparation method and application thereof, wherein the preparation method of the modified graphite provided by the invention sinters the purified graphite in a carbon dioxide atmosphere, so that the surface of the purified graphite is provided with holes, and lithium insertion sites are increased, thereby being beneficial to improving the capacity of a lithium ion battery; the preparation method improves the pH value of the purified graphite, and avoids using a washing mode to improve the pH value, thereby avoiding the discharge of a large amount of acid liquor, saving the production cost and improving the production efficiency; meanwhile, compared with sintering in an oxygen atmosphere, sintering in a carbon dioxide atmosphere does not cause the increase of the specific surface area of the spherical graphite, so that the loss of the cycle performance of the battery is not caused.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a method for preparing modified graphite, comprising the steps of:
sintering the purified graphite for 12-20 h at 1200-2000 ℃ in carbon dioxide atmosphere to obtain the modified graphite.
The sintering temperature in the present invention is 1200 to 2000 ℃, and may be, for example, 1200 ℃, 1250 ℃, 1300 ℃, 1350 ℃, 1400 ℃, 1450 ℃, 1500 ℃, 1550 ℃, 1600 ℃, 1650 ℃, 1700 ℃, 1750 ℃, 1800 ℃, 1850 ℃, 1900 ℃, 1950 ℃ or 2000 ℃, but is not limited to the values listed, and other values not listed in the numerical range are also applicable.
The sintering time in the present invention is 12 to 20 hours, and for example, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours or 20 hours may be used, but the present invention is not limited to the above-mentioned values, and other values not shown in the above-mentioned range are also applicable.
According to the preparation method of the modified graphite, the purified graphite is sintered in the carbon dioxide atmosphere, so that holes are formed on the surface of the purified graphite, and lithium insertion sites are increased, thereby being beneficial to improving the capacity of the lithium ion battery; the preparation method improves the pH value of the purified graphite, and avoids using a washing mode to improve the pH value, thereby avoiding the discharge of a large amount of acid liquor, saving the production cost and improving the production efficiency; meanwhile, compared with sintering in an oxygen atmosphere, sintering in a carbon dioxide atmosphere does not cause the increase of the specific surface area of the spherical graphite, so that the loss of the cycle performance of the battery is not caused.
Preferably, the gas in the carbon dioxide atmosphere comprises carbon dioxide and oxygen.
Preferably, the carbon dioxide content of the carbon dioxide atmosphere is not less than 95%, for example, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5% or 99.9%, but is not limited to the recited values, and other values not recited in the range of the values are also applicable.
Preferably, the carbon content of the purified graphite is not less than 95 wt.%, and may be, for example, 95 wt.%, 95.5 wt.%, 96 wt.%, 96.5 wt.%, 97 wt.%, 97.5 wt.%, 98 wt.%, 98.5 wt.%, 99 wt.%, 99.5 wt.%, or 99.9 wt.%, although not limited to the recited values, and other non-recited values within this range are equally applicable.
Preferably, the purified graphite is spherical graphite.
Preferably, the purified graphite has a D50 particle size of 5 to 25 μm, and may be, for example, 5 μm, 7 μm, 9 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm, 22 μm or 25 μm, but is not limited to the values listed, and other values not listed in the numerical range are also applicable.
Preferably, the purified graphite has a porosity of 30 to 40%, and may be, for example, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, or 40%, but is not limited to the recited values, and other values not recited within the range are also applicable.
Preferably, the pH of the purified graphite is 3 to 5, and may be, for example, 3, 3.2, 3.4, 3.6, 3.8, 4, 4.2, 4.4, 4.6 or 4.8, but is not limited to the recited values, and other values not recited within this range are also applicable.
Preferably, the graphite is natural graphite, and the purification mode is acid treatment.
Preferably, the acid in the acid treatment comprises any one or a combination of at least two of hydrofluoric acid, nitric acid, hydrochloric acid, or sulfuric acid, and typical but non-limiting combinations include combinations of hydrofluoric acid and nitric acid, nitric acid and hydrochloric acid, hydrochloric acid and sulfuric acid, hydrofluoric acid, nitric acid, and hydrochloric acid, or hydrofluoric acid, nitric acid, hydrochloric acid, and sulfuric acid.
Preferably, the preparation method further comprises heating before sintering.
Preferably, the temperature rise rate is 1 to 15 ℃/min, for example, 1 ℃/min, 2 ℃/min, 3 ℃/min, 4 ℃/min, 5 ℃/min, 6 ℃/min, 7 ℃/min, 8 ℃/min, 9 ℃/min, 10 ℃/min, 11 ℃/min, 12 ℃/min, 13 ℃/min, 14 ℃/min, or 15 ℃/min, but is not limited to the recited values, and other values within the range of values are also applicable.
Preferably, the sintering temperature is 1300 to 1500 ℃, for example 1300 ℃, 1350 ℃, 1400 ℃, 1450 ℃ or 1500 ℃, but is not limited to the recited values, and other values not recited in the range of values are equally applicable.
Preferably, the sintering time is 13 to 15 hours, for example 13 hours, 13.5 hours, 14 hours, 14.5 hours, or 15 hours, but is not limited to the recited values, and other values not recited within the range of values are also applicable.
Preferably, the sintering process further comprises the steps of scattering, grading, demagnetizing and packaging.
Preferably, the carbon content in the modified graphite is not less than 99.9 wt.%, and may be, for example, 99.91 wt.%, 99.92 wt.%, 99.93 wt.%, 99.94 wt.%, 99.95 wt.%, 99.96 wt.%, 99.97 wt.%, 99.98 wt.%, or 99.99 wt.%, although not limited to the recited values, and other non-recited values within this range are equally applicable.
Preferably, the modified graphite is spherical graphite.
Preferably, the modified graphite has a D50 particle diameter of 5 to 25 μm, and may be, for example, 5 μm, 7 μm, 9 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm, 22 μm or 25 μm, but is not limited to the values listed, and other values not listed in the numerical range are also applicable.
Preferably, the modified graphite has a porosity of 45 to 50%, for example 45%, 46%, 47%, 49% or 50%, but not limited to the recited values, and other values not recited in this range are also applicable.
Preferably, the modified graphite has a pH of 6.5 to 7, and may be, for example, 6.5, 6.65, 6.7, 6.75, 6.8, 6.85, 6.9, 6.95 or 7, but is not limited to the recited values, and other values not recited within the range of values are also applicable.
As a preferable embodiment of the preparation method of the first aspect, the preparation method comprises the steps of:
heating the natural graphite subjected to acid treatment to 1200-2000 ℃ at a heating rate of 1-15 ℃/min and sintering for 12-20 h in a carbon dioxide atmosphere with the carbon dioxide content of not less than 95% to obtain the modified graphite;
the natural graphite after acid treatment is spherical graphite, the carbon content is not less than 95wt%, the D50 particle size is 5-25 mu m, the porosity is 30-40%, and the pH value is 3-5;
the modified graphite is spherical graphite, the carbon content is not lower than 99.9wt%, the D50 particle size is 5-25 mu m, the porosity is 45-50%, and the pH value is 6.5-7.
In a second aspect, the present invention provides a modified graphite obtained by the preparation method of the first aspect.
In a third aspect, the present invention provides a modified graphite anode material comprising the modified graphite of the second aspect.
In a fourth aspect, the present invention provides a negative electrode sheet comprising the modified graphite negative electrode material according to the third aspect.
In a fifth aspect, the present invention provides an electrochemical energy storage device comprising the modified graphite anode material according to the third aspect or the anode sheet according to the fourth aspect.
Preferably, the electrochemical energy storage device is selected from one of a lithium ion battery, a sodium ion battery, a supercapacitor, a fuel cell or a solar cell.
Compared with the prior art, the invention has the following beneficial effects:
(1) According to the preparation method of the modified graphite, the purified graphite is sintered in the carbon dioxide atmosphere, so that the surface of the purified graphite is provided with holes, and lithium insertion sites are increased, thereby being beneficial to improving the capacity of a lithium ion battery;
(2) The preparation method of the modified graphite improves the pH value of the purified graphite, and avoids using a washing mode to improve the pH value, thereby avoiding the discharge of a large amount of acid liquor, saving the production cost and improving the production efficiency;
(3) Compared with sintering in an oxygen atmosphere, the preparation method of the modified graphite does not cause the increase of the specific surface area of the spherical graphite when sintering is carried out in a carbon dioxide atmosphere, so that the loss of the cycle performance of the battery is avoided.
Drawings
FIG. 1 is a scanning electron micrograph of the modified graphite obtained in example 1.
Detailed Description
The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitation of the present invention.
Example 1
The embodiment provides a preparation method of modified graphite, which comprises the following steps:
(1) Treating and purifying natural graphite by hydrofluoric acid to obtain purified spherical graphite, wherein the carbon content is 98wt%, the D50 particle size is 15 mu m, the porosity is 35%, and the pH value is 3.8;
(2) And in a carbon dioxide atmosphere with the carbon dioxide content of 99 percent and the oxygen content of 1 percent, heating the purified spherical graphite to 1600 ℃ at the heating rate of 8 ℃/min, and sintering for 14 hours to obtain the modified graphite.
The scanning electron microscope was used to test the obtained modified graphite, and the scanning electron microscope image shown in fig. 1 of the modified graphite was obtained, and it was found that the modified graphite was spherical graphite.
Example 2
The embodiment provides a preparation method of modified graphite, which comprises the following steps:
(1) Purifying natural graphite by nitric acid treatment to obtain purified spherical graphite, wherein the carbon content is 96wt%, the D50 particle size is 19 mu m, the porosity is 32%, and the pH value is 4.5;
(2) And in a carbon dioxide atmosphere with the carbon dioxide content of 98 percent and the oxygen content of 2 percent, heating the purified spherical graphite to 1400 ℃ at the heating rate of 12 ℃/min and sintering for 16h to obtain the modified graphite.
Example 3
The embodiment provides a preparation method of modified graphite, which comprises the following steps:
(1) Treating and purifying natural graphite by adopting hydrofluoric acid to obtain purified spherical graphite, wherein the carbon content is 99wt%, the D50 particle size is 21 mu m, the porosity is 38%, and the pH value is 3.4;
(2) And in a carbon dioxide atmosphere with the carbon dioxide content of 96% and the oxygen content of 4%, heating the purified spherical graphite to 1800 ℃ at the heating rate of 5 ℃/min, and sintering for 18h to obtain the modified graphite.
Example 4
The embodiment provides a preparation method of modified graphite, which comprises the following steps:
(1) Purifying natural graphite by hydrochloric acid treatment to obtain purified spherical graphite, wherein the carbon content is 99.9wt%, the D50 particle size is 5 mu m, the porosity is 30%, and the pH value is 3;
(2) And in a carbon dioxide atmosphere with the carbon dioxide content of 95% and the oxygen content of 5%, heating the purified spherical graphite to 2000 ℃ at the heating rate of 15 ℃/min, and sintering for 12h to obtain the modified graphite.
Example 5
The embodiment provides a preparation method of modified graphite, which comprises the following steps:
(1) Purifying natural graphite by adopting sulfuric acid treatment to obtain purified spherical graphite, wherein the carbon content is 95wt%, the D50 particle size is 20 mu m, the porosity is 40%, and the pH value is 5;
(2) And in a carbon dioxide atmosphere with the carbon dioxide content of 99.9 percent and the oxygen content of 0.1 percent, heating the purified spherical graphite to 1200 ℃ at the heating rate of 1 ℃/min, and sintering for 20h to obtain the modified graphite.
Example 6
This example provides a method for preparing modified graphite, which is the same as that of example 1 except that the carbon dioxide content in the carbon dioxide atmosphere in step (2) is 92% and the oxygen content is 8%.
Example 7
This example provides a method for producing modified graphite, which is the same as in example 1 except that the temperature increase rate in step (2) is 0.5 ℃/min.
Example 8
This example provides a method for producing modified graphite, which is the same as in example 1 except that the temperature increase rate in step (2) is 18 ℃/min.
Comparative example 1
This comparative example provides a modified graphite preparation method, which is the same as that of example 1 except that the carbon dioxide atmosphere having a carbon dioxide content of 99% and an oxygen content of 1% in step (2) was replaced with the oxygen atmosphere having an oxygen content of 100%.
Comparative example 2
This comparative example provides a process for producing modified graphite, which was the same as in example 1 except that the carbon dioxide atmosphere having a carbon dioxide content of 99% and an oxygen content of 1% in step (2) was replaced with an argon atmosphere having an argon content of 99% and an oxygen content of 1%.
Comparative example 3
This comparative example provides a process for producing modified graphite, which is the same as in example 1 except that the sintering temperature in step (2) was 1000 ℃.
Comparative example 4
This comparative example provides a process for producing modified graphite, which is the same as in example 1 except that the sintering temperature in step (2) was 2400 ℃.
Comparative example 5
This comparative example provides a process for producing modified graphite, which is the same as in example 1 except that the sintering time in step (2) was 10 hours.
Comparative example 6
This comparative example provides a process for producing modified graphite, which is the same as in example 1 except that the sintering time in step (2) was 24 hours.
Carrying out carbon content test and particle size test, porosity test and pH value test on the obtained modified graphite, wherein the test results are shown in table 1;
the carbon content test method comprises the following steps: sintering 3g of modified graphite in a muffle furnace at 900 ℃ for 7min, testing the residual mass as the impurity mass, and dividing the mass lost in sintering by the total mass of the modified graphite before sintering as the carbon content;
the particle size test method comprises the following steps: carrying out wet test on the modified graphite by using a Malvern 3000 particle size analyzer to obtain the particle size of the modified graphite;
the porosity test method comprises the following steps: testing the porosity of the modified graphite by using a mercury intrusion method;
the pH value test method comprises the following steps: testing by using a Wantong 914pH meter according to GB/T243357-2019 to obtain the pH value of the modified graphite;
assembling the obtained modified graphite into a lithium ion battery according to GB/31241-2014, and carrying out a battery capacity test and a battery cycle performance test, wherein the test results are shown in Table 2;
the method for testing the battery capacity comprises the following steps: the modified graphite obtained in the above embodiments and comparative examples, S66 binder, CMC and conductive agent SP are compounded into a negative electrode plate in a mass ratio of 96.7.
TABLE 1
Figure BDA0003824503210000111
Figure BDA0003824503210000121
TABLE 2
First discharge capacity (mAh/g) Capacity retention (%) at 1000 cycles at ordinary temperature
Example 1 371.5 99.4
Example 2 370.6 99.7
Example 3 370.8 99.6
Example 4 371.8 99.7
Example 5 370.2 99.6
Example 6 364.0 95.0
Example 7 364.2 95.4
Example 8 363.3 95.4
Comparative example 1 364.3 95.3
Comparative example 2 364.0 95.7
Comparative example 3 364.1 95.4
Comparative example 4 364.2 95.4
Comparative example 5 363.9 95.6
Comparative example 6 363.9 96.0
From tables 1 and 2, it can be seen that:
(1) The modified graphite obtained by the preparation method of the modified graphite in the embodiments 1 to 5 has higher porosity, the pH value is also improved, and the lithium ion battery prepared from the obtained modified graphite has higher first discharge capacity and capacity retention rate; according to the preparation method of the modified graphite, the purified graphite is sintered in the carbon dioxide atmosphere, so that the surface of the purified graphite is provided with holes, and lithium insertion sites are increased, thereby being beneficial to improving the capacity of a lithium ion battery; the preparation method improves the pH value of the purified graphite, and avoids using a washing mode to improve the pH value, thereby avoiding the discharge of a large amount of acid liquor, saving the production cost and improving the production efficiency; meanwhile, compared with sintering in an oxygen atmosphere, sintering in a carbon dioxide atmosphere does not cause the increase of the specific surface area of the spherical graphite, so that the loss of the cycle performance of the battery is avoided;
(2) As can be seen from the comparison between the embodiment 1 and the embodiment 6, the content of carbon dioxide in the carbon dioxide atmosphere in the invention can affect the performance of the modified graphite, thereby affecting the performance of the lithium ion battery; when the content of carbon dioxide in the carbon dioxide atmosphere is low and the content of impurity gases is high, residual acid on the surface of the purified graphite cannot be sufficiently removed, so that the pH value of the modified graphite is low;
(3) As can be seen from the comparison between example 1 and examples 7 and 8, the temperature increase rate of the temperature increase during the sintering in the present invention affects the performance of the modified graphite, and thus the performance of the lithium ion battery; when the heating rate of heating is low, the sintering time is too long, the holes are too large, the specific surface area of the modified graphite is increased, the cycle performance is reduced, the gas cost is increased, and the energy consumption is increased; when the temperature rise rate of the temperature rise is higher, the sintering time is too short, acid liquor on the surface of the purified graphite cannot be sufficiently removed, and the pH value of the modified graphite is lower;
(4) As can be seen from the comparison of example 1 with comparative examples 1 and 2, the sintering atmosphere in the present invention affects the performance of the modified graphite, and thus the performance of the lithium ion battery; in the invention, carbon dioxide is used as the sintering atmosphere, so that the pH value of the modified graphite can be increased, the purified graphite surface is provided with holes, and the number and the size of the holes are easy to control; when the sintering atmosphere is oxygen, the purified graphite surface can be opened and the pH value of the modified graphite can be increased, but excessive pores are easily caused, so that the specific surface area of the modified graphite is increased, and the cycle performance is reduced; when the sintering atmosphere is argon, the pH value of the modified graphite can be increased, but the purified graphite surface cannot be provided with holes.
(5) As can be seen from the comparison of example 1 with comparative examples 3 and 4, the sintering temperature in the present invention affects the performance of the modified graphite, and thus the performance of the lithium ion battery; when the sintering temperature is low, residual acid on the surface of the purified graphite cannot be sufficiently removed, so that the pH value of the modified graphite is low; when the sintering temperature is too high, the pores of the purified graphite are too large, so that the specific surface area of the modified graphite is increased, the cycle performance is reduced, and the energy consumption is increased;
(6) As can be seen from the comparison of example 1 with comparative examples 5 and 6, the sintering time in the present invention affects the performance of the modified graphite, and thus the performance of the lithium ion battery; when the sintering time is shorter, the acid solution on the surface of the purified graphite cannot be sufficiently removed, so that the pH value of the modified graphite is lower; when the sintering time is too long, the pores of the purified graphite are too large, so that the specific surface area of the modified graphite is increased, the cycle performance is reduced, and the energy consumption is increased;
in conclusion, in the preparation method of the modified graphite, the purified graphite is sintered in the carbon dioxide atmosphere, so that the surface of the purified graphite is provided with holes, and lithium insertion sites are increased, thereby being beneficial to improving the capacity of the lithium ion battery; the preparation method of the modified graphite improves the pH value of the purified graphite, and avoids using a washing mode to improve the pH value, thereby avoiding the discharge of a large amount of acid liquor, saving the production cost and improving the production efficiency; compared with sintering in an oxygen atmosphere, the preparation method of the modified graphite does not cause the increase of the specific surface area of the spherical graphite when sintering is carried out in a carbon dioxide atmosphere, so that the loss of the cycle performance of the battery is not caused.
The above description is only for the specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are within the protection scope and the disclosure of the present invention.

Claims (10)

1. A preparation method of modified graphite is characterized by comprising the following steps:
sintering the purified graphite for 12-20 h at 1200-2000 ℃ in the atmosphere of carbon dioxide to obtain the modified graphite.
2. The method according to claim 1, wherein the gas in the carbon dioxide atmosphere comprises carbon dioxide and oxygen;
the content of carbon dioxide in the carbon dioxide atmosphere is not less than 95%.
3. The method of claim 1 or 2, wherein the carbon content in the purified graphite is not less than 95wt%;
preferably, the purified graphite is spherical graphite;
preferably, the D50 particle size of the purified graphite is 5-25 μm;
preferably, the porosity of the purified graphite is 30 to 40%;
preferably, the pH value of the purified graphite is 3-5;
preferably, the graphite is natural graphite, and the purification mode is acid treatment;
preferably, the acid in the acid treatment comprises any one of hydrofluoric acid, nitric acid, hydrochloric acid or sulfuric acid, or a combination of at least two thereof.
4. The production method according to any one of claims 1 to 3, characterized by further comprising a temperature rise before sintering;
preferably, the heating rate of the heating is 1-15 ℃/min;
preferably, the sintering temperature is 1300-1500 ℃;
preferably, the sintering time is 13 to 15 hours.
5. The production method according to any one of claims 1 to 4, wherein the carbon content in the modified graphite is not less than 99.9wt%;
preferably, the modified graphite is spherical graphite;
preferably, the D50 particle size of the modified graphite is 5-25 μm;
preferably, the porosity of the modified graphite is 45-50%;
preferably, the modified graphite has a pH of 6.5 to 7.
6. The production method according to any one of claims 1 to 5, characterized by comprising the steps of:
heating the natural graphite subjected to acid treatment to 1200-2000 ℃ at a heating rate of 1-15 ℃/min and sintering for 12-20 h in a carbon dioxide atmosphere with the carbon dioxide content of not less than 95% to obtain the modified graphite;
the natural graphite after acid treatment is spherical graphite, the carbon content is not lower than 95wt%, the D50 particle size is 5-25 mu m, the porosity is 30-40%, and the pH value is 3-5;
the modified graphite is spherical graphite, the carbon content is not lower than 99.9wt%, the D50 particle size is 5-25 mu m, the porosity is 45-50%, and the pH value is 6.5-7.
7. A modified graphite obtained by the production method according to any one of claims 1 to 6.
8. A modified graphite anode material, characterized in that it comprises the modified graphite of claim 7.
9. A negative electrode sheet, characterized in that the negative electrode sheet comprises the modified graphite negative electrode material according to claim 8.
10. An electrochemical energy storage device comprising the modified graphite anode material of claim 8 or the anode sheet of claim 9;
preferably, the electrochemical energy storage device is selected from one of a lithium ion battery, a sodium ion battery, a supercapacitor, a fuel cell or a solar cell.
CN202211054746.1A 2022-08-31 2022-08-31 Modified graphite and preparation method and application thereof Pending CN115215335A (en)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005008810A1 (en) * 2003-07-22 2005-01-27 Byd Company Limited Improved graphite granules and their method of fabrication
CN102275904A (en) * 2011-05-31 2011-12-14 黑龙江科技学院 Method of preparing high-purity graphite by using chemical liquid-phase method
CN111392723A (en) * 2020-03-26 2020-07-10 浙江锂宸新材料科技有限公司 Preparation method of porous graphite, product and application thereof
CN114068923A (en) * 2020-07-30 2022-02-18 湖南中科星城石墨有限公司 Modification method of graphite and application of graphite in lithium ion battery

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005008810A1 (en) * 2003-07-22 2005-01-27 Byd Company Limited Improved graphite granules and their method of fabrication
CN102275904A (en) * 2011-05-31 2011-12-14 黑龙江科技学院 Method of preparing high-purity graphite by using chemical liquid-phase method
CN111392723A (en) * 2020-03-26 2020-07-10 浙江锂宸新材料科技有限公司 Preparation method of porous graphite, product and application thereof
CN114068923A (en) * 2020-07-30 2022-02-18 湖南中科星城石墨有限公司 Modification method of graphite and application of graphite in lithium ion battery

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