CN115224255A - Method for preparing high-performance lithium ion battery negative electrode material from artificial graphite - Google Patents

Method for preparing high-performance lithium ion battery negative electrode material from artificial graphite Download PDF

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CN115224255A
CN115224255A CN202210803601.0A CN202210803601A CN115224255A CN 115224255 A CN115224255 A CN 115224255A CN 202210803601 A CN202210803601 A CN 202210803601A CN 115224255 A CN115224255 A CN 115224255A
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artificial graphite
lithium ion
ion battery
graphite
temperature
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林雄超
岳彦龙
张续春
王彩红
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China University of Mining and Technology Beijing CUMTB
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    • H—ELECTRICITY
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    • H01M10/00—Secondary cells; Manufacture thereof
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    • 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
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    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
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Abstract

The invention provides a preparation method of an isotropic artificial graphite lithium ion battery cathode material, belonging to the field of secondary resource utilization. The method takes artificial graphite recovered from a graphite electrode as a raw material, and utilizes the methods of chemical treatment, surface coating and high-temperature granulation to obtain the lithium ion battery cathode material with better electrochemical performance. The method comprises the following steps: the artificial graphite is crushed and screened to obtain micron-sized artificial graphite particles, and the micron-sized artificial graphite particles are respectively purified and subjected to pore-forming by acid leaching and oxidation methods. And after washing and drying, placing the graphite into high-temperature equipment filled with inert gas for treatment, mixing the obtained artificial graphite into a solution dissolved with a carbon precursor, stirring, performing ultrasonic treatment and solvent removal, and continuously performing high-temperature treatment on the obtained black solid mixture in an inert atmosphere to obtain the high-performance lithium ion battery cathode material. The preparation method has the advantages of no damage to equipment, environmental protection, simple operation and excellent electrochemical performance of the battery cathode material.

Description

Method for preparing high-performance lithium ion battery negative electrode material from artificial graphite
Technical Field
The invention belongs to the field of secondary resource utilization, and discloses a method for preparing a high-performance lithium ion battery cathode material by using artificial graphite.
Background
According to statistics, the global consumption of graphite is huge nowadays, the demand of the graphite is increased greatly in the aspect of energy storage of electric automobiles and the like, and with the development of technical processes, the consumption of the graphite in high-end markets in the aspects of energy storage, new energy and the like is estimated to reach 40-50% of the total consumption of the graphite in 2030 years. But the capability of obtaining high added value of the high-grade graphite products in China is insufficient, and the chain length period of the whole industry in the middle and downstream of the graphite is in the position of low and middle-end raw material supply countries. Artificial graphite and natural graphite with low added values are used for preparing graphite crucibles, graphite electrodes, refractory materials and the like, and high-value utilization of graphite resources cannot be realized.
Lithium ion batteries are a novel renewable energy storage device, and under the background of global transfer of fossil energy to renewable energy gradually, because of their characteristics of high energy density, long endurance time, and low self-discharge potential, they are widely used in energy storage devices, such as: electronic equipment, electric automobile, future home distribution and communication base station, etc. High theoretical specific capacity (about 372mAhg -1 ) The lithium ion battery has the characteristics of good cycle stability and lower lithium storage potential as the negative electrode material of the lithium ion battery. The graphite negative electrode materials mainly comprise artificial graphite, natural graphite and the like, the artificial graphite and the natural graphite are easy to have a solvent coinsertion reaction with an organic Propylene Carbonate (PC) solvent of an electrolyte, so that lithium salt between graphite layers is deposited, the electrolyte is continuously and irreversibly decomposed, the graphite layers are enlarged, pulverized and dropped, and an SEI film is secondarily recombined; and the active sites at the edge of the graphene layer are exposed in the process of forming the intercalation compound, the electrolyte reacts with the graphene layer again, and the SEI film is recombined to reduce the lithium storage capacity of the graphite and cause the reversible capacity loss of the lithium ion battery; and natural graphite and artificial graphite belong to anisotropy and cannot achieve the high rate capability and high specific capacity of the isotropic spherical graphite negative electrode material. The amorphous carbon coating layer is formed on the surface of the graphite layer, and the isotropic artificial graphite is formed by utilizing asphalt carbonization and graphite recombination at high temperature, so that the situations can be effectively inhibited, the circulation stability of the artificial graphite is improved, and the performances such as specific capacity, first coulombic efficiency, charging and discharging multiplying power and the like are improved.
Compared with natural graphite, the artificial graphite has better cycle stability, higher safety, more excellent charge-discharge rate performance and high specific capacity, is widely applied to the fields of medium-high-end EV, 3C and the like, and is the mainstream of the current lithium ion battery cathode material. However, the artificial graphite needs to consume a large amount of energy in the graphitization process, the cost required by the energy consumption caused by the graphitization process is as high as half of the cost of the artificial graphite, and with the continuous increase of the market of the artificial graphite, how to achieve the artificial graphite capable of being applied to high and medium-end uses with less energy consumption becomes more important. When the primary artificial graphite product is used for the graphite cathode material of the lithium ion battery, the requirement of higher specific capacity cannot be met, the rate capability is low, the cycle stability is poor, the first coulombic efficiency is low, and the primary artificial graphite product cannot be used for the graphite cathode material of the lithium ion battery. The invention takes the middle-low end artificial graphite for manufacturing the graphite crucible and the graphite electrode as raw materials, utilizes a chemical method, a surface modification method and a high-temperature granulation method to improve the quality of the artificial graphite, greatly improves the cycle performance and the rate capability of the artificial graphite, increases the application of the artificial graphite in the lithium ion battery graphite cathode material, and expands the application market of the artificial graphite in the lithium ion battery graphite cathode material.
Disclosure of Invention
In order to solve the problems of poor rate performance, poor cycle stability, low specific capacity and the like of the artificial graphite, the invention provides a method for modifying the artificial graphite by using a chemical method and surface modification, forming isotropic artificial graphite by using asphalt and the artificial graphite for granulation at high temperature, and preparing a high-performance lithium ion battery cathode material by forming the isotropic artificial graphite with a stable amorphous carbon layer through graphite surface oxidation, asphalt coating and high-temperature granulation. The method comprises the following specific steps:
(1) And crushing the artificial graphite, and screening by using a screen to obtain micron-sized artificial graphite particles.
(2) Weighing artificial graphite particles with a certain mass, adding a certain amount of acid solution, mixing, purifying, adding a certain amount of oxidant into the mixture, stirring at a certain temperature, and performing acid leaching and oxidation treatment;
(3) Washing, centrifuging and drying the graphite treated in the step 2 for multiple times by using deionized water, and then treating the graphite for 1 to 3 hours (preferably 2 hours) in high-temperature equipment with an inert body to obtain a product 1;
(4) Adding the product 1 into an organic solution in which asphalt is dissolved, stirring for 10-20 min (preferably 20 min), then ultrasonically dispersing for 20-40 min (preferably 40 min) to obtain a mixture with better dispersibility, recycling the organic solvent in an evaporation mode, and treating the mixture in high-temperature equipment filled with inert gas to obtain a final product.
Wherein, the artificial graphite particles in the step (1) need to be 300 meshes (54 micrometers) or less.
Wherein the acidic reagent in (2) is a weak acid (preferably citric acid) such as citric acid, boric acid, formic acid, acetic acid, etc.
Wherein, the solid-to-liquid ratio of the artificial graphite to the weak acid in the step (2) is 1:20 to 1:100 (preferably 1.
Wherein, the oxidant in (2) can be one or more of the following combinations: hydrogen peroxide, concentrated hydrochloric acid, concentrated sulfuric acid, concentrated nitric acid, and potassium permanganate (preferably hydrogen peroxide).
Wherein, the oxidant in the step (2) is added during acid leaching, the adding amount is 5-10% (preferably 8%) of the acid volume ratio, and after the adding, water bath is needed for 10-30min (preferably 30 min) at the temperature of 50-80 ℃ (preferably 70 ℃).
Wherein, the high-temperature equipment under the inert gas in the step (3) can be: a tube furnace.
Wherein, the inert gas in the step (3) is one or more of nitrogen, argon or helium.
Wherein, the temperature of the high-temperature equipment under the inert gas atmosphere in the step (3) is set as follows: the temperature is raised from room temperature at a heating rate of 5-10 ℃/min (preferably 5 ℃/min), is stabilized at 400-500 ℃ (preferably 500 ℃) for 30-60 min (preferably 30 min), is raised to 800-1200 ℃ (preferably 1000 ℃) at a heating rate of 5-10 ℃/min (preferably 5 ℃/min), and is kept for 2-5 h (preferably 2 h).
Wherein the asphalt Softening Point (SP) in the (4) is required to be 250 ℃ to 280 ℃ (preferably 275 ℃). The Coking Value (CV) is required to be 70-85% (preferably 85%), the quinoline insolubles is required to be 0-20% (preferably 10%),
wherein, the organic solvent in (4) can be toluene, tetrahydrofuran, pyridine, quinoline, N-methyl pyrrolidone (tetrahydrofuran is preferred).
Wherein, the method for separating the organic solvent in (4) can be rotary evaporation, reduced pressure distillation and vacuum drying, and the organic solvent separated by the first two methods can be used as a circulating solvent for dissolving asphalt.
Wherein, when the organic solvent is separated in the step (4), the solvent with low boiling point can be evaporated by adopting a rotary evaporator, a vacuum drying oven and other equipment, and the solvent with high boiling point can be continuously and stably evaporated by adopting a reduced pressure distillation mode in the magnetic stirring process.
Wherein, the rotary evaporator in the step (4) is in water bath or oil bath, the vacuum degree is controlled between 0.05Mpa and-0.1 Mpa (preferably 0.08 Mpa), the temperature is between 50 ℃ and 160 ℃ (preferably 80 ℃),
wherein, the vacuum degree of the reduced pressure distillation equipment in the step (4) is controlled between 0.08Mpa and-0.1 Mpa (preferably-0.1 Mpa), and the temperature is between 100 ℃ and 180 ℃ (preferably 160 ℃).
Wherein, the high temperature equipment of the step (4) is the same as the above, the mixture of the evaporated solvent is stabilized at 300 ℃ to 450 ℃ (preferably 350 ℃) for 30 to 60min, and then is raised to 800 ℃ to 1000 ℃ (preferably 800 ℃) for 1 to 4h (preferably 2 h).
The invention also provides the lithium ion battery cathode material prepared by the preparation method of the lithium ion battery cathode material.
The invention also provides a lithium ion battery which comprises the lithium ion battery cathode material.
The lithium ion battery is a lithium ion button battery.
The invention has the following beneficial technical effects:
the invention aims to form isotropic artificial graphite particles with a core-shell structure by using the artificial graphite with poor electrochemical performance by a chemical method, a surface modification method and a high-temperature granulation method on the basis that the artificial graphite has better lithium storage conditions, so that the electrochemical performance of the artificial graphite is improved, the advantage of high theoretical specific capacity of the artificial graphite is exerted, and the artificial graphite is applied to a lithium ion battery graphite cathode material. Removing impurities from micron-sized artificial graphite by acid leaching, oxidizing and high-temperature treatment, forming nano and micron-sized holes on the surface, adding lithium storage sites of the graphite, dispersing and uniformly mixing the pitch with pore-forming and purified graphite by using high softening point and high coking value dissolved in an organic solvent, calcining the pitch in a tube furnace at high temperature after the solvent is removed, forming a uniform and compact amorphous carbon layer on the graphite surface at high temperature, and recombining and granulating part of the pitch insoluble in the organic solvent and the artificial graphite at high temperature to form isotropic artificial graphite with a coating layer. The coating layer can effectively wrap graphite, so that the graphite layer is prevented from being crushed and falling off due to the co-insertion of an organic solvent of the electrolyte and lithium ions, the secondary recombination of an SEI film is prevented, the stability of the formed SEI film is improved to a certain extent, and the first charge-discharge specific capacity, the first coulombic efficiency and the cycling stability of the graphite cathode material are improved; the re-granulated isotropic artificial graphite can increase the rate capability of the negative electrode material on the basis of improving the specific capacity.
The organic solution in the step 4 of the invention can be recovered by rotary evaporation and reduced pressure distillation and recycled as a solvent.
The method disclosed by the invention is simple to operate, the modification period is short, the required reagent is a conventional cheap reagent, the corrosion of weak acid to the equipment pipeline is small, part of organic solvent can be recycled, the whole process is green and environment-friendly, the operability is strong, the method is an effective means for realizing the high-added-value application of the artificial graphite, the high-grade utilization of the artificial graphite can be increased while the energy loss is reduced, the defects of poor cycle stability, poor rate capability and the like of graphite cathode materials are improved, and the method has a very wide application prospect.
Drawings
Fig. 1 is a Scanning Electron Microscope (SEM) photograph of the artificial graphite electrode materials prepared in comparative example, example 1, example 2, and example 3.
FIG. 2 is a process scheme of the present invention.
Fig. 3 is a graph of the cycling performance and coulombic efficiency and rate performance of the sample of the comparative example.
Fig. 4 is a graph of cycling performance and coulombic efficiency and rate performance for the samples of example 1.
Fig. 5 is a graph of cycling performance and coulombic efficiency and rate performance for the samples of example 2.
Fig. 6 is a graph of cycling performance and coulombic efficiency and rate performance for the samples of example 3.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Comparative example
a) Crushing the blocky artificial graphite by using a crusher, and sieving by using a 300-mesh sieve to obtain artificial graphite particles with the particle size of 54 micrometers or less;
b) The artificial graphite particles obtained in the step a) are directly used as a lithium ion battery cathode material, a metal lithium sheet is used as a counter electrode, celgard2325 is used as a diaphragm, 1mol/L LiPF6 (solvent is a mixed solution of ethylene carbonate EC and diethyl carbonate DEC with the volume ratio of 1).
And assembling the semi-button cell, and performing cyclic charge and discharge test and rate capability test by using a blue cell test system of Wuhan blue electron Limited. Set the current density at 500mAg -1 The voltage range is 0.005-2V, the assembled button cell is subjected to 110-circle constant-current charging and discharging under the constant temperature condition (25 ℃), and the charging and discharging current density is 200mAg -1 、500mAg -1 、1000mAg -1 、2000mAg -1 、5000mAg -1 、200mAg -1 The rate capability was tested at 100mAg -1 The material was activated 3 times at current density and then subjected to the above-mentioned 10 cycles at different current densities to carry out the test rate charge-discharge test.
The material is 500mAg -1 Current density down cycleThe capacity of the ring after 110 circles is 327.2mAhg -1 The coulombic efficiency was 99.68%, and the discharge capacity exhibited at each current density was 298.2mAhg -1 、205.7mAhg -1 、128.4mAhg -1 、65.7mAhg -1 、31.2mAhg -1 Finally, the concentration of the mixed solution is kept at 290.3mAhg -1 After the charge and discharge with the multiplying power, the capacity retention rate is 98.95%, the specific capacity is low, the cycle stability in the process of charging and discharging for 110 circles is poor, and the multiplying power performance is poor, as shown in figure 1.
Example 1
a) Crushing the blocky artificial graphite by using a crusher, and sieving by using a 300-mesh sieve to obtain artificial graphite particles with the particle size of 54 micrometers or less;
b) The obtained 5g of particles are placed in a beaker, and 1 molar concentration of citric acid (solid-to-liquid ratio of artificial graphite to citric acid solution is 1:40 And stirring for 2 hours at room temperature by using a magnetic stirrer to fully disperse the graphite particles in the citric acid to form a suspension. Adding a 30% mass concentration H2O2 solution (the volume ratio of citric acid to the H2O2 solution is 100);
c) Separating graphite particles by using a centrifugal machine, washing the graphite particles to be neutral by using a large amount of deionized water, drying the graphite particles in a drying oven at the temperature of 120 ℃ for 12h, putting the dried graphite in a tubular furnace, setting the heating rate of 5 ℃/min, heating the graphite to 500 ℃ from the room temperature, keeping the temperature for 30min, heating the graphite to 1000 ℃ at the same heating rate, purifying the artificial graphite, keeping the temperature for 2h, and cooling the graphite to the room temperature by using the tubular furnace to obtain a product 1.
The product 1 prepared in the above way is directly used as a lithium ion battery cathode material, a metal lithium sheet is used as a counter electrode, celgard2325 is used as a diaphragm, 1mol/L LiPF6 (a solvent is a mixed solution of ethylene carbonate EC and diethyl carbonate DEC with a volume ratio of 1. A blue electricity battery testing system from Wuhan blue electricity electronic limited company is utilized to carry out cyclic charge-discharge testing and multiplying power performance testing. Set the current density to 500mAg -1 The voltage range is 0.005-2V, and the temperature is constant (25℃)) The assembled button cell is subjected to 110-turn constant current charge and discharge, and the charge and discharge current density is 200mAg -1 、500mAg -1 、1000mAg -1 、2000mAg -1 、5000mAg -1 、200mAg -1 The rate capability was tested at 100mAg -1 The material was activated 3 times at current density and then subjected to the above-mentioned 10 cycles at different current densities to carry out the test rate charge-discharge test.
The material is 500mAg -1 The capacity after circulating for 110 circles under the current density is 352.3mAhg -1 The coulombic efficiency was 99.73%, and the discharge capacity exhibited at each current density was 339.2mAhg -1 、327.1mAhg -1 、265.1mAhg -1 、85.4mAhg -1 、338.2mAhg -1 Finally, the concentration is kept at 334.6mAhg -1 The capacity retention rate after multiplying power charging and discharging is 99.34%, the high-capacity lithium ion battery shows good specific capacity, the charging and discharging process is stable and cyclic, and no obvious attenuation exists, and the high-capacity lithium ion battery is shown in an attached figure 2.
Example 2
a) Crushing the blocky artificial graphite by using a crusher, and sieving the blocky artificial graphite by using a 300-mesh sieve to obtain artificial graphite particles with the particle size of 54 microns or less;
b) 10g of the obtained granules were placed in a beaker, and 1 molar citric acid (solid-to-liquid ratio of artificial graphite to citric acid solution of 1:40 And stirring for 2 hours at room temperature by using a magnetic stirrer to fully disperse the graphite particles in the citric acid to form a suspension. Adding a 30% mass concentration H2O2 solution (the volume ratio of citric acid to the H2O2 solution is 100);
c) Separating graphite particles by using a centrifugal machine, washing the graphite particles to be neutral by using a large amount of deionized water, drying the graphite particles in a drying oven at the temperature of 120 ℃ for 12h, putting the dried graphite in a tubular furnace, setting the heating rate of 5 ℃/min, heating the graphite to 500 ℃ from the room temperature, keeping the temperature for 30min, heating the graphite to 1000 ℃ at the same heating rate, purifying the artificial graphite, keeping the temperature for 2h, and cooling the graphite to the room temperature by using the tubular furnace to obtain a product 1.
d) 1g of coal pitch having a softening point of 275 ℃, a coking value of 85% and a QI content of 10% was dissolved in 100ml of tetrahydrofuran solvent in a beaker, and the ratio of pitch to product 1 was selected to be 1:10, adding the product 1 into a tetrahydrofuran beaker of fully dissolved asphalt, stirring for 20min by using magnetic stirring, and then putting the beaker into an ultrasonic cleaning instrument for 40min to obtain a uniformly dispersed graphite and asphalt mixture;
e) Transferring the mixture in the beaker to a rotary evaporator, vacuumizing to water bath of 80 ℃ under 0.08Mpa until tetrahydrofuran is evaporated out, and keeping constant temperature until the solvent is completely evaporated out to the flask for recycling to obtain graphite and asphalt solid particles which are uniformly mixed;
f) And (3) putting the solid particles into a tubular furnace in a nitrogen atmosphere, keeping the temperature of the tubular furnace for 30min when the temperature rises to 350 ℃ at the temperature rise rate of 5 ℃/min, so that the asphalt is stably and uniformly adhered to the surface of the graphite, then rising the temperature to 800 ℃ at the temperature rise rate of 5 ℃/min, and keeping the temperature for 2 hours, so that the asphalt adhered to the surface of the graphite stably forms a uniform and compact carbon layer. And when the temperature of the tube furnace is reduced to room temperature, obtaining a final product.
The final product prepared above is directly used as a lithium ion battery cathode material, a metal lithium sheet is used as a counter electrode, celgard2325 is used as a diaphragm, 1mol/L LiPF6 (a solvent is a mixed solution of Ethylene Carbonate (EC) and diethyl carbonate (DEC) with a volume ratio of 1. A blue battery testing system from Wuhan blue electronic Limited company is utilized to carry out cyclic charge and discharge tests and rate capability tests. Set the current density to 500mAg -1 The voltage range is 0.005-2V, the assembled button cell is charged and discharged for 110 circles of constant current under the constant temperature condition (25 ℃), and the current density of charging and discharging is 200mAg -1 、500mAg -1 、1000mAg -1 、2000mAg -1 、5000mAg -1 、200mAg -1 The rate capability was tested at 100mAg -1 The material was activated 3 times at current density and then subjected to the above-mentioned 10 cycles at different current densities to carry out the test rate charge-discharge test.
The material is 500mAg -1 Current densityCapacity of 379.7mAhg after 110 cycles of lower circulation -1 The coulombic efficiency was 99.42%, and the discharge capacity exhibited at each current density was 392.4mAhg -1 、389.7mAhg -1 、376.2mAhg -1 、351.3mAhg -1 、266.8mAhg -1 Finally, the concentration is maintained at 380.1mAhg -1 The capacity retention rate after multiplying power charging and discharging is 99.21%, the specific capacity is good, the charging and discharging process is stable and cyclic, no obvious attenuation exists, and the multiplying power performance is good, as shown in figure 3.
Example 3
a) Crushing the blocky artificial graphite by using a crusher, and sieving the blocky artificial graphite by using a 300-mesh sieve to obtain artificial graphite particles with the particle size of 54 microns or less;
b) 10g of the obtained granules were placed in a beaker, and 1 molar citric acid (solid-to-liquid ratio of artificial graphite to citric acid solution of 1:40 And stirring for 2 hours at room temperature by using a magnetic stirrer to fully disperse the graphite particles in the citric acid to form a suspension. Adding a 30% mass concentration H2O2 solution (the volume ratio of citric acid to the H2O2 solution is 100);
c) Separating graphite particles by using a centrifugal machine, washing the graphite particles to be neutral by using a large amount of deionized water, drying the graphite particles in a drying oven at the temperature of 120 ℃ for 12 hours, putting the dried graphite in a tubular furnace, setting the heating rate of 5 ℃/min, heating the graphite from room temperature to 500 ℃, keeping the temperature for 30 minutes, heating the graphite to 1000 ℃ at the same heating rate, purifying the artificial graphite, keeping the temperature for 2 hours, and cooling the graphite in the tubular furnace to the room temperature to obtain a product 1.
d) 0.5g of coal pitch with a high softening point of 275 ℃, a high coking value of 85% and a QI content of 10% was dissolved in 50ml of tetrahydrofuran solvent in a beaker, the ratio of pitch to product 1 was chosen to be 1:12, adding the product 1 into a beaker of fully dissolved tetrahydrofuran soluble substances, stirring for 20min by using magnetic stirring, and then putting the beaker into an ultrasonic cleaning instrument for 40min to obtain a uniformly dispersed graphite and asphalt mixture;
e) Transferring the mixture in the beaker to a rotary evaporator, vacuumizing to 80 ℃ under 0.08Mpa in water bath until tetrahydrofuran is evaporated out, and keeping constant temperature until the solvent is completely evaporated out to the flask for recycling, so as to obtain graphite and asphalt solid particles which are uniformly mixed;
f) And (3) putting the solid particles into a tubular furnace in a nitrogen atmosphere, keeping the temperature of the tubular furnace for 30min when the temperature rises to 350 ℃ at the heating rate of 5 ℃/min, so that the asphalt is stably and uniformly adhered to the surface of the graphite, then heating to 800 ℃ at the heating rate of 5 ℃/min, and keeping the temperature for 2 hours, so that the asphalt adhered to the surface of the graphite stably forms a uniform and compact carbon layer. And when the temperature of the tube furnace is reduced to the room temperature, obtaining the final product.
The final product prepared above is directly used as a lithium ion battery cathode material, a metal lithium sheet is used as a counter electrode, celgard2325 is used as a diaphragm, 1mol/L LiPF6 (a solvent is a mixed solution of Ethylene Carbonate (EC) and diethyl carbonate (DEC) with a volume ratio of 1. A blue battery testing system from Wuhan blue electronic Limited company is utilized to carry out cyclic charge and discharge tests and rate capability tests. Set the current density to 500mAg -1 The voltage range is 0.005-2V, the assembled button cell is charged and discharged for 110 circles of constant current under the constant temperature condition (25 ℃), and the current density of charging and discharging is 200mAg -1 、500mAg -1 、1000mAg -1 、2000mAg -1 、5000mAg -1 、200mAg -1 The rate capability was tested at 100mAg -1 The material was activated 3 cycles at current density and then the different current densities described above were performed 10 cycles to perform a test rate charge and discharge test.
The material is 500mAg -1 The capacity after circulating for 110 circles under the current density is 451.5mAhg -1 The coulombic efficiency was 99.74%, and the discharge capacity exhibited at each current density was 468.1mAhg -1 、476.0mAhg -1 、453.4mAhg -1 、419.0mAhg -1 、291.9mAhg -1 Finally, the magnetic field strength is kept at 481.9mAhg -1 The capacity retention rate after the multiplying power charging and discharging is 96.65 percent, the high-performance lithium ion battery has good specific capacity, stable and cyclic charging and discharging process, no obvious attenuation and good multiplying power performance,as shown in fig. 4.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. This need not be, nor should it be exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.

Claims (11)

1. A method for preparing a high-performance lithium ion battery cathode material by using artificial graphite comprises the following steps:
(1) Crushing the artificial graphite, and screening by using a screen to obtain micron-sized artificial graphite particles of 300 meshes and below;
(2) Weighing the artificial graphite particles with a certain mass obtained in the step (1), adding a certain proportion of acid solution, mixing, purifying, adding a certain amount of oxidant into the mixture, stirring at a certain temperature, and performing acid leaching and oxidation treatment;
(3) Washing, centrifuging and drying the graphite treated in the step 2 for multiple times by using deionized water, and then treating the graphite in high-temperature equipment under an inert atmosphere for 1 to 3 hours to obtain a product 1;
(4) Adding the product 1 into an organic solution in which the coating asphalt is dissolved, stirring for 10-20 min, then performing ultrasonic dispersion for 20-40 min to obtain a mixture with better dispersibility, removing the organic solvent in an evaporation mode, recycling, and treating the mixture in high-temperature equipment under inert gas to obtain a final product serving as a lithium ion battery cathode material.
2. The method for preparing the high-performance lithium ion battery negative electrode material by using the artificial graphite as claimed in claim 1, wherein the particle size of the artificial graphite particles in the step (1) is 54 μm or less.
3. The method for preparing the high-performance lithium ion battery negative electrode material from the artificial graphite according to claim 1, wherein the acidic reagent in the step (2) is a weak acid such as citric acid, boric acid, formic acid, acetic acid and the like, and the solid-to-liquid ratio of the artificial graphite to the weak acid is 1:20 to 1:100, the content of the fixed carbon of the purified graphite is required to be more than 98%, and the oxidant can be one or a combination of more than one of the following components: hydrogen peroxide, concentrated hydrochloric acid, concentrated sulfuric acid, concentrated nitric acid, potassium permanganate and oxidant are added during acid leaching, the addition amount is 5-15% of the volume ratio of the acid, and after the addition, water bath is carried out for 30-60 min at the temperature of 50-80 ℃.
4. The method for preparing the negative electrode material of the high-performance lithium ion battery from the artificial graphite according to claim 1, wherein the high-temperature equipment under inert gas in the step (3) can be: in the tubular furnace, inert gas is one or more of nitrogen, argon or helium, the heating rate is 5-10 ℃/min, the temperature is stabilized at 400-500 ℃ for 30-60 min, the temperature is raised to 800-1200 ℃ at the same heating rate, and the high temperature time is controlled to be 2-5 h.
5. The method for preparing the high-performance lithium ion battery negative electrode material from the artificial graphite according to claim 1, wherein the asphalt Softening Point (SP) in the step (4) is required to be 250-280 ℃, the Coking Value (CV) is required to be 70-85%, and the quinoline insoluble is required to be 0-20%; the solid-liquid ratio of the asphalt to the organic solvent is 1:50 to 1:150, the organic solvent may be Toluene (Toluene), tetrahydrofuran (Tetrahydrofuran), pyridine (pyridine), quinoline (Quinoline), N-Methylpyrrolidone (N-Methylpyrrolidone).
6. The method for preparing a high-performance lithium ion battery negative electrode material by using artificial graphite as claimed in claim 1, wherein the method for separating the organic solvent in (4) can be rotary evaporation, reduced pressure distillation, vacuum drying, and the organic solvent separated by the first two methods can be recycled as a solvent for dissolving asphalt.
7. The method for preparing the negative electrode material of the high-performance lithium ion battery from the artificial graphite as claimed in claim 1, wherein (4) the rotary evaporator is a water bath or an oil bath, the vacuum degree is controlled to be 0.05Mpa to-0.1 Mpa, the temperature is controlled to be 50 ℃ to 160 ℃, the vacuum degree of the reduced pressure distillation equipment is controlled to be 0.08Mpa to-0.1 Mpa, and the temperature is controlled to be 100 ℃ to 180 ℃.
8. The method for preparing the high-performance lithium ion battery cathode material from the artificial graphite as claimed in claim 1, wherein the high-temperature equipment in (4) is a tube furnace of one or more inert gases in nitrogen, argon or helium, the mixture of the evaporated solvents is stabilized at 350-450 ℃ for 30-60 min, then is heated to 800-1000 ℃ and the time is controlled to be 2-5 h.
9. The lithium ion battery negative electrode material prepared by the preparation method of the lithium ion battery negative electrode material disclosed by the claims 1-8.
10. A lithium ion battery comprising the lithium ion battery negative electrode material of claim 9.
11. The lithium ion battery of claim 10, wherein the lithium ion battery is a button cell.
CN202210803601.0A 2022-07-07 2022-07-07 Method for preparing high-performance lithium ion battery negative electrode material from artificial graphite Pending CN115224255A (en)

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