CN107814383B - Modified microcrystalline graphite negative electrode material for lithium ion battery and preparation method and application thereof - Google Patents
Modified microcrystalline graphite negative electrode material for lithium ion battery and preparation method and application thereof Download PDFInfo
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Abstract
The invention relates to the technical field of lithium ion battery carbon cathode materials, in particular to a modified microcrystalline graphite cathode material for a lithium ion battery and a preparation method and application thereof. The prepared material has the following advantages: (1) the modified natural graphite cathode material with the core-shell structure, in which the artificial graphite is embedded in the natural graphite in situ and on the surface, is prepared, the overall structural characteristics of the natural microcrystalline graphite are reserved, and the artificial graphite is filled in the pores of the natural microcrystalline graphite and is coated on the outer surface. (2) Compared with the existing cathode material, the cathode material prepared by the method has good isotropy, and can inhibit and absorb the expansion generated by the electrode in the charging and discharging processes; the material prepared by the invention has high coulombic efficiency for the first time, long service life and good high-rate charge and discharge performance, and can replace artificial graphite to be prepared as the cathode material of the power battery, thereby greatly reducing the cost. (3) The method has the advantages of simple preparation process, low cost and high practicability.
Description
Technical Field
The invention relates to the technical field of lithium ion battery carbon cathode materials, in particular to a modified microcrystalline graphite cathode material for a lithium ion battery and a preparation method and application thereof.
Background
The lithium ion battery has a series of advantages of high specific capacity, high working voltage, good safety, no memory effect and the like, and is widely applied to the fields of 3C products, power devices, energy storage equipment and the like. With the popularization of new energy automobiles, the application range of the new energy automobiles is expanded to the fields of electric vehicles, automobiles and the like. In recent years, with the increasing demand for miniaturization, weight reduction, multifunction, and long-term driving of electronic products, vehicles, and energy storage devices, the demand for high energy density, high rate performance, and long cycle life of lithium ion batteries has been increasing.
The cathode material is one of the core components of the battery and plays a critical role in the comprehensive performance of the battery. At present, the negative electrode material of commercial lithium ion batteries is still the dominant graphite material, and although the artificial graphite has good cycle performance, the artificial graphite has low capacity and high price, so that the manufacturing cost of power batteries is increased. Natural graphite is widely used because of its high charge-discharge capacity, good charge-discharge plateau, wide sources and low cost. However, the conventional modified natural crystalline flake graphite has complete crystals, developed layer orientation and obvious anisotropy, and only allows lithium ions to be inserted and extracted along the boundary of the graphite, so that the lithium ions are long in insertion and extraction distance, unsuitable for large-current charging and discharging and poor in rapid charging and discharging performance. These drawbacks limit the further use of modified natural flake graphite in high performance lithium ion batteries. The natural microcrystalline graphite is a mineral product with abundant reserves in China, and the negative electrode material prepared by the natural microcrystalline graphite has extremely excellent performances in two aspects of cycle life, quick charge and quick discharge due to the small crystal and the near-isotropic structure. However, the natural microcrystalline graphite has high impurity content, the carbon content is only 80-90%, and the purity of the graphite must be improved to more than 99.0% when the graphite is used as a lithium ion battery cathode material. CN1063958A and CN105977487A adopt crushing, pitch cladding, carbonization, graphitization preparation modified microcrystal graphite negative electrode material, utilize high temperature graphitization to remove the inside impurity of natural microcrystal graphite, when the impurity gets rid of the back, can leave a large amount of micropores in microcrystal graphite inside, can lead to defects such as the first charge-discharge efficiency is low and cycle life is short.
Disclosure of Invention
In order to solve the problems, the invention aims to provide a modified microcrystalline graphite negative electrode material for a lithium ion battery, and a preparation method and application thereof.
The invention provides a preparation method of a modified microcrystalline graphite negative electrode material, which comprises the following steps:
(1) coarsely crushing microcrystalline graphite, and purifying with an acidic aqueous solution;
(2) crushing, shaping and grading the material obtained in the step (1);
(3) putting the material obtained in the step (2) into a packaging bag, sealing, putting the packaging bag into an impregnation tank, vacuumizing, and heating the impregnation tank;
(4) injecting liquid asphalt into the impregnation tank under high pressure, stopping vacuumizing when the asphalt liquid exceeds the height of a packaging bag in the impregnation tank, and maintaining the pressure and the temperature for a period of time;
(5) after the heat preservation in the step (4) is finished, removing the asphalt from the impregnation tank, returning the asphalt to the melting tank for recycling, and after the packaging bag is taken out and cooled, crushing, washing, filtering and drying the obtained material;
(6) carbonizing the material obtained in the step (5);
(7) and (4) carrying out graphitization treatment on the material obtained in the step (6) to obtain the modified natural microcrystalline graphite negative electrode material.
According to the invention, the carbon content of the microcrystalline graphite in the step (1) can be 80-90%;
according to the invention, step (1) can be carried out under heating conditions, for example at a temperature of 85 to 95 ℃;
according to the invention, in step (1), the acidic aqueous solution is selected from a mixed aqueous solution of one or more inorganic acids such as HCl, HF, H in any proportion2SO4、H2S2O7、H3PO4Or HNO3E.g. H2SO4Mixed acid aqueous solution of HF and HCl;
according to the invention, in the step (1), the purity of the microcrystalline graphite is improved to more than 99.0%;
according to the invention, in the step (2), the pulverizer is selected from a low-speed impact type spheroidizing pulverizer, a gas flow vortex pulverizer, an ultrafine pulverizer or an ultrafine ball mill; the shaping machine is selected from a jet mill, a high-pressure mill or a rod type mechanical mill; the classifier is selected from an air flow classifier, a jet flow classifier, a submicron classifier or a submicron air flow classifier;
according to the invention, in the step (2), D of the crushed, shaped and classified material50Can be 8-20 μm;
according to the invention, in the step (3), the vacuum degree of the impregnation tank can be 0.07-0.09 MPa;
according to the invention, in the step (3), the heating temperature can be 300-350 ℃;
according to the invention, in the step (3), the package can be a flexible package;
according to the invention, in the step (4), the asphalt is selected from impregnated asphalt or asphalt with the softening point of 65-85 ℃ and the quinoline insoluble content of less than 1%;
according to the invention, in the step (4), the high pressure can be 30MPa to 50MPa, and the heat preservation time can be 1 to 3 hours;
according to the invention, in the step (4), the temperature of the melting tank can be 300-350 ℃;
according to the invention, the crushing in the step (5) is to crush the obtained material into coarse powder, and the particle size of the coarse powder can be 0.5-5 mm;
according to the present invention, the washing in step (5) may be washing with an organic solvent;
according to the invention, the crusher used in steps (1) and (5) is any device known in the art that can effect the crushing of the material, for example selected from the group consisting of a turbine crusher, a jaw crusher, a raymond mill, etc.;
according to the invention, in the step (5), the organic solvent is selected from one or more of washing oil, kerosene, benzene derivatives, oleic acid and quinoline;
according to the invention, in the step (5), the washing is preferably carried out under heating and stirring conditions; preferably, the heating temperature can be 60-120 ℃, and the stirring speed can be 200-700 r/min, for example 300-500 r/min;
according to the invention, in the step (5), the washing times and the washing time are not particularly limited, and the redundant asphalt coated on the surface of the asphalt can be cleaned, for example, the washing times are 1-3 times, and the washing time is 5-10 hours;
according to the invention, in the step (5), the drying can be carried out at 160-200 ℃ under a vacuum condition;
according to the invention, in the step (6), the temperature of the carbonization treatment is preferably 800-1200 ℃, and the carbonization time is preferably 4-10 hours;
according to the invention, in the step (6), when the filling rate of the carbonized microcrystalline graphite is less than 98%, the steps (3), (4), (5) and (6) need to be repeated;
according to the invention, in the step (7), the graphitization treatment method and conditions can be those conventional in the art, and the temperature of the graphitization treatment is preferably 2800-3000 ℃;
the invention also provides a modified natural microcrystalline graphite cathode material, which is prepared by the method;
according to the invention, D of said material509 to 21 μm.
The invention also provides a modified natural microcrystalline graphite cathode material, which has a core-shell structure, wherein the core is natural graphite filled with artificial graphite in pores, and the shell is artificial graphite;
according to the invention, the filling rate of the artificial graphite in the natural microcrystalline graphite pores is more than or equal to 98 percent;
according to the invention, D of the negative electrode material509 to 21 μm;
according to the invention, the mass fraction of the artificial graphite in the negative electrode material accounts for 7-10%, and more preferably 8%;
according to the invention, the tap density of the negative electrode material is 1.1-1.25 g/cm3。
The invention also provides application of the modified natural microcrystalline graphite negative electrode material in preparation of a negative electrode of a lithium ion power battery.
The invention also provides a negative electrode of the lithium ion power battery, which comprises the modified natural microcrystalline graphite negative electrode material.
The invention also provides a lithium ion power battery which comprises the negative electrode of the lithium ion power battery.
Advantageous effects
(1) The invention impregnates the natural microcrystalline graphite powder with the asphalt under high temperature and high pressure, can completely ensure that the asphalt fills the pores in the graphite particles in a liquid state, forms an asphalt coating layer on the surface of the asphalt coating layer, obtains the modified natural graphite cathode material with the core-shell structure, wherein the artificial graphite is embedded in the natural graphite in situ and on the surface of the natural graphite, retains the integral structural characteristic of the natural microcrystalline graphite, and fills the artificial graphite in the pores of the natural microcrystalline graphite and coats the outer surface of the natural microcrystalline graphite. The filling rate of the artificial graphite in the natural graphite pores is more than or equal to 98 percent, the particle surface is smooth, and the sphericity is high.
(2) Compared with the existing cathode material, the modified natural graphite cathode material prepared by the method has good isotropy, inhibits the electrode from expanding in the process of charging and discharging, and has the expansion rate less than or equal to 6 percent; the discharge capacity is more than or equal to 365mAh/g, the first coulombic efficiency is more than or equal to 96 percent, and the cycle life is obviously prolonged. The capacity retention rate of the material is more than or equal to 87% after 1C circulation at room temperature for 2000 weeks, particularly, the circulation performance of the whole material is obviously improved during high-rate charge and discharge, the large-current (3C-5C) charge and discharge performance is good, and the capacity retention rate is more than or equal to 86%.
(3) The method has the advantages of simple preparation process, low cost and high practicability.
Detailed Description
The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are only for illustrating the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that various changes or modifications can be made by those skilled in the art after reading the disclosure of the present invention, and such equivalents also fall within the scope of the invention.
Example 1
(1) Pulverizing microcrystalline graphite with carbon content of 85% to 100 mesh, and extracting with H at 95 deg.C2SO4HF and HCl (1:2:1.5) mixed acid water solution are purified, and the purity of the microcrystalline graphite is improved to 99.0 percent;
(2) crushing the material obtained in the step (1) by using a low-speed impact type spheroidizing crusher, shaping by using a jet mill, and finally classifying by using air flow to obtain D508 μm material;
(3) and (3) filling the material obtained in the step (2) into a soft packaging bag, sealing, putting the packaging bag into an impregnation tank, vacuumizing, and heating the impregnation tank to ensure that the vacuum degree reaches 0.07MPa and the temperature reaches 300 ℃.
(4) Injecting the asphalt in the melting tank (350 ℃) into the impregnation tank in the step (3) under the pressure of 30MPa, stopping vacuumizing when the asphalt liquid exceeds the height of a packaging bag in the impregnation tank, and preserving the heat for 1 hour under the pressure of 40 MPa;
(5) and (4) after the heat preservation in the step (4) is finished, removing the asphalt from the impregnation tank, returning the asphalt to the melting tank for recycling, taking out the soft packaging bag, cooling, crushing the obtained material into 3mm coarse powder in a Raymond mill, putting the obtained coarse powder into kerosene at the temperature of 60 ℃, stirring for 3 hours at the speed of 300r/min, filtering, washing the filtrate for 1 time again, and drying at the temperature of 160 ℃ under the vacuum condition.
(6) Carbonizing the material obtained in the step (5) at 1300 ℃ for 5 hours under the protection of nitrogen, and cooling to room temperature.
(7) And (4) carrying out graphitization high temperature (2800 ℃) treatment on the material obtained in the step (6) for 3 hours to obtain the modified natural microcrystalline graphite negative electrode material.
Example 2
(1) Pulverizing microcrystalline graphite with carbon content of 90% to 100 mesh, and adding H at 90 deg.C2SO4HF and HCl (1:1.5:1) mixed acid aqueous solution are purified, and the purity of the microcrystalline graphite is improved to 99.2 percent;
(2) crushing the material obtained in the step (1) by using an airflow vortex micronizer, shaping by using a high-pressure pulverizer, and finally obtaining D by using a jet type classifier5012 μm material;
(3) and (3) filling the material obtained in the step (2) into a soft packaging bag, sealing, putting the packaging bag into an impregnation tank, vacuumizing, and heating the impregnation tank to ensure that the vacuum degree reaches 0.08MPa and the temperature reaches 300 ℃.
(4) Injecting the asphalt in the melting tank (300 ℃) into the impregnation tank in the step (3) under 50MPa, stopping vacuumizing when the asphalt liquid exceeds the height of a packaging bag in the impregnation tank, and preserving heat for 2 hours under 50 MPa;
(5) and (4) after the heat preservation in the step (4) is finished, removing the asphalt from the impregnation tank, returning the asphalt to the melting tank for recycling, taking out the soft packaging bag, cooling, crushing the obtained material into 2mm coarse powder in a turbine type crusher, putting the obtained coarse powder into xylene at the temperature of 120 ℃, stirring for 2 hours at the speed of 500r/min, and filtering. The filtrate was rewashed 2 times and dried under vacuum at 200 ℃.
(6) Carbonizing the material obtained in the step (5) at 1000 ℃ for 8 hours under the protection of nitrogen, and cooling to room temperature.
(7) And (4) carrying out graphitization high temperature (2800 ℃) treatment on the material obtained in the step (6) for 5 hours to obtain the modified natural microcrystalline graphite negative electrode material.
Example 3
(1) Pulverizing microcrystalline graphite with carbon content of 80% to 100 mesh, and extracting with H at 95 deg.C2SO4HF and HCl (1:2.5:2) mixed acid aqueous solution are purified, and the purity of the microcrystalline graphite is improved to 99.4 percent;
(2) crushing the material obtained in the step (1) by using an ultrafine crusher, then using a rod type mechanical crusher, and finally using an ultrafine rice airflow classifier to obtain D5016 μm material;
(3) and (3) filling the material obtained in the step (2) into a soft packaging bag, sealing, putting the packaging bag into an impregnation tank, vacuumizing, and heating the impregnation tank to ensure that the vacuum degree reaches 0.09MPa and the temperature reaches 330 ℃.
(4) Injecting the asphalt in the melting tank (330 ℃) into the impregnation tank in the step (3) under 50MPa, stopping vacuumizing when the asphalt liquid exceeds the height of a packaging bag in the impregnation tank, and preserving the heat for 3 hours under 50 MPa;
(5) and (4) after the heat preservation in the step (4) is finished, removing the asphalt from the impregnation tank, returning the asphalt to the melting tank for recycling, taking out the soft packaging bag, cooling, crushing the obtained material into 1mm coarse powder in a Raymond mill, putting the obtained coarse powder into washing oil at the temperature of 100 ℃, stirring for 2 hours at the speed of 400r/min, and filtering. The filtrate was rewashed 1 time and dried under vacuum at 200 ℃.
(6) Carbonizing the material obtained in the step (5) at 1200 ℃ for 8 hours under the protection of nitrogen, and cooling to room temperature.
(7) And (4) carrying out graphitization high temperature (3000 ℃) treatment on the material obtained in the step (6) for 5 hours to obtain the modified natural microcrystalline graphite negative electrode material.
Example 4
(1) Pulverizing microcrystalline graphite with carbon content of 85% to 100 mesh, and adding H at 90 deg.C2SO4HF and HCl (1:2.5:2) mixed acid aqueous solution are purified, and the purity of the microcrystalline graphite is improved to 99.0 percent;
(2) crushing the material obtained in the step (1) by using an ultrafine ball mill, then using a rod type mechanical crusher, and finally using a submicron classifier to obtain D5020 μm in mass.
(3) And (3) filling the material obtained in the step (2) into a soft packaging bag, sealing, putting the packaging bag into an impregnation tank, vacuumizing, and heating the impregnation tank to ensure that the vacuum degree reaches 0.09MPa and the temperature reaches 320 ℃.
(4) Injecting the asphalt in the melting tank (320 ℃) into the impregnation tank in the step (3) under 45MPa, stopping vacuumizing when the asphalt liquid exceeds the height of a packaging bag in the impregnation tank, and preserving the heat for 3 hours under 45 MPa;
(5) and (4) after the heat preservation in the step (4) is finished, removing the asphalt from the impregnation tank, returning the asphalt to the melting tank for recycling, taking out the soft packaging bag, cooling, crushing the obtained material into 1mm coarse powder in a Raymond mill, putting the obtained coarse powder into kerosene at the temperature of 60 ℃, stirring for 2 hours at the speed of 300r/min, and filtering. The filtrate was washed 3 times again and dried under vacuum at 160 ℃.
(6) Carbonizing the material obtained in the step (5) at 1000 ℃ for 10 hours under the protection of nitrogen, and cooling to room temperature.
(7) And (4) carrying out graphitization high temperature (2800 ℃) treatment on the material obtained in the step (6) for 8 hours to prepare the modified natural microcrystalline graphite cathode material.
Comparative example 1
(1) Pulverizing microcrystalline graphite with carbon content of 85% to 100 mesh, and sievingAt 95 ℃ with H2SO4HF and HCl (1:2:1.5) mixed acid water solution are purified, and the purity of the microcrystalline graphite is improved to 99.0 percent;
(2) crushing the material obtained in the step (1) by using a low-speed impact type spheroidizing crusher, shaping by using a jet mill, and finally classifying by using air flow to obtain D50The material is 8 μm.
(3) And (3) uniformly mixing the material obtained in the step (2) and asphalt (the content of quinoline insoluble is 0.5%) according to the mass ratio of 100:30, and filling the mixture into a graphite crucible. Putting the graphite crucible into a muffle furnace, heating to 300 ℃, keeping the temperature for 3 hours, and then cooling to room temperature along with the furnace after power failure;
(4) crushing the material obtained in the step (3) into 3mm coarse powder in a Raymond mill, putting the obtained coarse powder into 60 ℃ kerosene, stirring for 3 hours at the speed of 300r/min, filtering, and drying at 160 ℃ under vacuum condition.
(5) Carbonizing the material obtained in the step (4) at 1300 ℃ for 5 hours under the protection of nitrogen, and cooling to room temperature.
(6) And (3) carrying out graphitization high temperature (2800 ℃) treatment on the material obtained in the step (5) for 3 hours to prepare the modified natural microcrystalline graphite cathode material.
Comparative example 2
(1) Average particle diameter D50Natural crystalline flake graphite of 20 μm is packed in a soft packing bag and sealed, the packing bag is put in a dipping tank, vacuumized and heated to make the vacuum degree reach 0.07MPa and the temperature reach 300 ℃.
(2) Injecting asphalt in a melting tank (350 ℃) into an impregnation tank under the pressure of 30MPa, stopping vacuumizing when asphalt liquid exceeds the height of a packaging bag in the impregnation tank, and preserving heat for 1 hour under the pressure of 40 MPa;
(3) and (3) after the heat preservation in the step (2) is finished, removing the asphalt from the impregnation tank, and returning the asphalt to the melting tank for recycling. After the soft packaging bag is taken out and cooled, the obtained material is crushed into 3mm coarse powder in a Raymond mill, the obtained coarse powder is put into kerosene with the temperature of 60 ℃, the mixture is stirred for 3 hours at the speed of 300r/min, then the filtering is carried out, the filtered substance is washed for 1 time again, and the dried substance is dried at the temperature of 160 ℃ under the vacuum condition.
(4) Carbonizing the material obtained in the step (3) at 1300 ℃ for 5 hours under the protection of nitrogen, and cooling to room temperature.
(5) And (4) carrying out graphitization high temperature (2800 ℃) treatment on the material obtained in the step (4) for 3 hours to prepare the modified natural microcrystalline graphite cathode material.
Examples and comparative examples Performance testing
The modified natural graphite negative electrode materials prepared by the graphitization treatment of the examples 1-4 and the comparative examples 1-2 are respectively taken, and the weight percentages of the modified natural graphite negative electrode materials are as follows: polyvinylidene fluoride (PVDF): conductive graphite 93: 5:2, placing the mixture in a high-speed dispersion machine to stir to prepare active slurry, and coating the active slurry on an aluminum foil to obtain the negative pole piece.
The lithium ion battery is obtained by assembling the negative electrode plate and the lithium positive electrode, and the first reversible capacity, the first coulombic efficiency, the cycle capacity retention rate and the electrode expansion rate of the modified natural graphite are respectively tested, and specific results are shown in table 1.
TABLE 1 electrochemical Performance test results
As can be seen from Table 1, the modified natural microcrystalline graphite negative electrode material has good cycle performance and rate capability, and can be used for replacing artificial graphite to prepare a negative electrode material of a lithium ion power battery. Compared with the existing natural graphite cathode material, the modified natural graphite cathode material has the first coulombic efficiency of more than or equal to 96 percent, the capacity retention rate of more than or equal to 87 percent at room temperature and 1C cycle of 2000 weeks and the expansion rate of less than or equal to 6 percent, and particularly when the material is charged and discharged at high rate, the cycle performance of the whole material is obviously improved, the large-current (3C-5C) charging and discharging performance is good, and the capacity retention rate is more than or equal to 86 percent, so that the material prepared by the invention is very suitable for manufacturing lithium ion power batteries.
The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (12)
1. The preparation method of the modified microcrystalline graphite negative electrode material is characterized by comprising the following steps of:
(1) coarsely crushing microcrystalline graphite, and purifying with an acidic aqueous solution;
(2) crushing, shaping and grading the material obtained in the step (1);
(3) putting the material obtained in the step (2) into a packaging bag, sealing, putting the packaging bag into an impregnation tank, vacuumizing, and heating the impregnation tank;
the vacuum degree of the impregnation tank is 0.07-0.09 MPa, and the heating temperature is 300-350 ℃;
the package is a soft package;
(4) injecting liquid asphalt into the impregnation tank under high pressure, stopping vacuumizing when the asphalt liquid exceeds the height of a packaging bag in the impregnation tank, and maintaining the pressure and the temperature for a period of time;
the high pressure is 30MPa to 50MPa, and the heat preservation time is 1 to 3 hours;
the asphalt is selected from impregnated asphalt or asphalt with the softening point of 65-85 ℃ and the content of quinoline insoluble substances of less than 1%;
(5) after the heat preservation in the step (4) is finished, removing the asphalt from the impregnation tank, returning the asphalt to the melting tank for recycling, and after the packaging bag is taken out and cooled, crushing, washing, filtering and drying the obtained material;
(6) carbonizing the material obtained in the step (5);
(7) and (4) carrying out graphitization treatment on the material obtained in the step (6) to obtain the modified natural microcrystalline graphite negative electrode material.
2. The preparation method according to claim 1, wherein the carbon content of the microcrystalline graphite in the step (1) is 80-90%;
the step (1) is carried out under the heating condition, wherein the heating temperature is 85-95 ℃;
in the step (1), the acidic aqueous solution is selected from one or more mixed aqueous solutions of inorganic acids in any proportion, and the inorganic acids are selected from HCl,HF、H2SO4、H2S2O7、H3PO4Or HNO3；
In the step (1), the purity of the purified microcrystalline graphite is improved to more than 99.0 percent;
in the step (2), the pulverizer for pulverizing is selected from a low-speed impact type spheroidizing pulverizer, a gas flow vortex pulverizer, an ultrafine pulverizer or an ultrafine ball mill; the shaping machine for shaping is selected from a jet mill, a high-pressure mill or a rod type mechanical mill; the classifier for classification is selected from an air flow classifier, a jet flow classifier, a submicron classifier or a submicron air flow classifier;
in the step (2), D of the crushed, shaped and classified material508 to 20 μm.
3. The method according to claim 2, wherein in the step (1), the inorganic acid is H2SO4And mixed acid aqueous solution of HF and HCl.
4. The production method according to claim 1 or 2,
in the step (5), the temperature of the melting tank is 300-350 ℃;
crushing the obtained material into coarse powder with the particle size of 0.5-5 mm in the step (5);
washing in the step (5) by using an organic solvent; the organic solvent is selected from one or more of washing oil, kerosene, benzene derivatives, oleic acid and quinoline;
the crusher used in the steps (1) and (5) is selected from a turbine crusher, a jaw crusher and a Raymond machine;
in the step (5), the washing is carried out under the condition of heating and stirring; the heating temperature is 60-120 ℃, and the stirring speed is 200-700 r/min;
in the step (5), the washing times and the washing time are the time for cleaning the redundant asphalt coated on the surface of the asphalt;
in the step (5), the drying is carried out at 160-200 ℃ under a vacuum condition.
5. The method according to claim 4, wherein in the step (5), the stirring speed is 300 to 500r/min, the washing times are 1 to 3 times, and the washing time is 5 to 10 hours.
6. The method according to claim 1 or 2, wherein in the step (6), the temperature of the carbonization treatment is 800 to 1200 ℃, and the time of the carbonization is 4 to 10 hours;
in the step (6), when the filling rate of the carbonized microcrystalline graphite is less than 98%, the steps (3), (4), (5) and (6) need to be repeated.
7. The method according to claim 1 or 2, wherein the graphitization treatment in the step (7) is performed at a temperature of 2800 to 3000 ℃.
8. Modified natural microcrystalline graphite negative electrode material obtained by the method of any of claims 1-7, characterized in that D of the material is50The thickness of the modified natural microcrystalline graphite negative electrode material is 9-21 mu m, the modified natural microcrystalline graphite negative electrode material has a core-shell structure, the core is natural graphite with artificial graphite filled in pores, and the shell is artificial graphite;
the filling rate of the artificial graphite in the natural microcrystalline graphite pores is more than or equal to 98 percent;
the mass fraction of the artificial graphite in the negative electrode material accounts for 7-10% of that of the negative electrode material;
the tap density of the negative electrode material is 1.1-1.25 g/cm3。
9. The negative electrode material of claim 8,
the mass fraction of the artificial graphite in the negative electrode material accounts for 8 percent.
10. Use of the anode material according to claim 8 or 9 for the preparation of an anode for a lithium ion power cell.
11. A negative electrode for a lithium ion power cell comprising the modified natural microcrystalline graphite negative electrode material of claim 8 or 9.
12. A lithium ion power cell comprising the negative electrode of the lithium ion power cell of claim 11.
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| CN111244398A (en) * | 2018-11-28 | 2020-06-05 | 上海杉杉科技有限公司 | Composite graphite negative electrode material, lithium ion battery, preparation method and application |
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