CN110642247B - Artificial graphite negative electrode material, preparation method thereof and lithium ion battery - Google Patents
Artificial graphite negative electrode material, preparation method thereof and lithium ion battery Download PDFInfo
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Abstract
The invention discloses a preparation method of a high-energy-density multiplying artificial graphite cathode material, which comprises the following steps: directly coarsely crushing and grinding raw coke or coarsely crushing and grinding the raw coke after high-temperature modification, and shaping to obtain primary particles A; kneading the primary particles A and an organic carbon source, then performing dynamic thermal coating, and screening to obtain primary particles B; uniformly mixing the primary particles A with a binder, placing the mixture in a granulation reaction kettle for granulation, and screening to obtain secondary particles C; respectively carrying out graphitization treatment on the primary particles B and the secondary particles C, and screening to obtain graphitized primary particles B and graphitized secondary particles C; uniformly mixing the graphitized primary particles B and the graphitized secondary particles C in proportion, and screening to obtain a finished product. The preparation method has simple process and easily controlled quality; the artificial graphite cathode material prepared by the method is applied to a lithium ion battery, and the lithium ion battery has high capacity, good cycle and excellent quick charge performance.
Description
Technical Field
The invention relates to the technical field of lithium ion battery cathode materials, in particular to an artificial graphite cathode material, a preparation method thereof and a lithium ion battery.
Background
Lithium ion batteries have been used in the past twenty years as the most widely used driving force source for current mobile digital terminals (mobile phones, tablets, notebooks) and novel wearable devices. People are pursuing the ultra-long standby of mobile equipment and simultaneously have more and more strict requirements on the charging time of the mobile equipment. With the rapid development of electric vehicles, people desire that electric vehicles have long endurance and have rapid charging performance. Therefore, the demand for high-capacity high-rate lithium ion batteries has increased year by year.
For a long time, the improvement of the capacity, compaction, reduction of expansion and improvement of the comprehensive condition cycle performance of the artificial graphite are the key points of research and development. Most of graphite negative electrode materials applied to the current market are anisotropic graphite, and the high orientation of the graphite negative electrode materials limits the rapid charge and discharge performance and the cycle life of the lithium ion battery. The surface of the pure artificial graphite has more active end faces, so that the side reaction of the electrolyte can be accelerated in the charging and discharging processes, the irreversible capacity is increased, and the circulation stability is weakened. At present, methods for improving the rate capability of graphite cathode materials mainly include surface modification, particle size reduction and particle compounding. The secondary particle coating carbonization can obtain a high-capacity high-rate material, but has the problems of poor coating uniformity, remarkable secondary bonding phenomenon, low yield and the like, and the processing performance of the material is seriously influenced.
In order to solve the above problems, patent 201710683450.9 discloses a fast-charging graphite negative electrode material and a preparation method thereof, in which a graphite precursor is mixed with a coating material, and the mixture is subjected to low-temperature treatment and high-temperature graphitization treatment, but a secondary granulation process and a surface modification process are not required, so that the improvement effects of an ion diffusion path and an interface are limited, the energy density is not high, and the fast-charging performance is not significantly improved. Patent 201711333907.X discloses a preparation method of a composite graphite anode material with high capacity and high rate, wherein a graphite precursor and mesocarbon microbeads are mixed and then granulated and graphitized, so that although the dynamic level of the material is improved, the energy density is low, and the preparation cost is high. Patent 201810939161.5 discloses a method for preparing a high-rate fast-charging graphite cathode material, which comprises the steps of firstly pulverizing a graphite precursor, graphitizing, and then fusing and carbonizing with a binder.
According to the problems in the industry, how to more reasonably optimize and structurally combine the graphite structure is the direction of the primary consideration in the production of high-end artificial graphite cathodes. In view of this, there is a need to develop a fast-charging graphite anode material and a preparation method thereof.
Therefore, a multiplying power type artificial graphite negative electrode material with high capacity, high compaction density and long service life and a preparation method thereof are provided.
Disclosure of Invention
The invention mainly aims to provide an artificial graphite cathode material and a preparation method thereof, and the artificial graphite cathode material has the advantages of high capacity, good cycle and excellent quick charging performance.
In order to achieve the purpose, the invention provides a preparation method of a high-energy density multiplying factor type artificial graphite negative electrode material, which comprises the following steps:
s1, directly coarsely crushing and grinding raw coke or coarsely crushing and grinding raw coke after high-temperature modification, and shaping to obtain primary particles A;
s2, kneading the primary particles A and an organic carbon source, performing dynamic thermal coating, and screening to obtain primary particles B;
s3, uniformly mixing the primary particles A with the binder, placing the mixture into a granulation reaction kettle for granulation, and screening to obtain secondary particles C;
s4, performing graphitization treatment on the primary particles B and the secondary particles C respectively, and screening to obtain graphitized primary particles B and graphitized secondary particles C;
and S5, uniformly mixing the graphitized primary particles B and the graphitized secondary particles C in proportion, and screening to obtain a finished product.
Preferably, in S1, when the raw coke is green coke with a volatile content of more than 3%, the raw coke is coarsely broken, is subjected to high-temperature modification treatment and then is ground into powder; when the raw coke is calcined coke with the volatile component not more than 3%, directly coarsely crushing and grinding into powder; the raw coke can be 1 or the combination of at least 2 of needle coke, common coke and asphalt coke;
wherein, the coarse crushing adopts a jaw crusher or a back hammer crusher, and the size of crushed particles is controlled to be less than 5 meshes; the ground powder is crushed by a mechanical mill or a roller mill; the high-temperature modification temperature is 800-1400 ℃, and the reaction time is 1-8 hours; the shaping adopts a physical grinding method shaping machine; the primary particles A have an average particle diameter D50 of 5 to 15 [ mu ] m and an aspect ratio of 0.5 to 2. Preferably, the primary particles A have an average particle diameter D50 of 7 to 10 μm and an aspect ratio of 0.7 to 1.5.
Preferably, in S2, the organic carbon source is composed of at least 4 elements of carbon, hydrogen, oxygen and nitrogen, wherein the oxygen content by mass is not less than 3%, preferably 5% to 10%, and the organic carbon source is 1 or a combination of at least 2 of low-temperature asphalt, soluble starch, monosaccharide, soluble polysaccharide, aromatic hydrocarbon pyrolysis oil, ethylene tar or liquid resin with a softening point of less than 30 ℃; the mass ratio of the primary particles A to the organic carbon source is 100: 5-15. Preferably, the mass ratio of the primary particles A to the organic carbon source is 100: 7-10.
Preferably, in S2, the kneading is performed using a vacuum kneader; kneading is carried out in 2 sections, the kneading temperature of the first section is 100-150 ℃, and the kneading time is 1-4 hours; the kneading temperature of the second stage is 180-280 ℃, the kneading time is 2-4 hours, and the vacuum degree is not higher than 10 kPa; the dynamic thermal coating is carried out in a vertical reaction kettle or a horizontal reaction kettle with a stirring device under the protection of inert gas at the temperature of 450-700 ℃ for 1-10 hours, and the stirring speed is 5-50 rpm; the inert gas is 1 or the combination of at least 2 of nitrogen, helium and argon; the average particle size D50 of the primary particles B is 5-15 mu m, the thickness of a coating layer of amorphous carbon on the surfaces of the primary particles B is 0.1-1 mu m, and the atomic ratio concentration of oxygen atoms on the surfaces of the primary particles B is 2-5%.
Preferably, in S3, the binder is asphalt and/or petroleum resin, wherein the asphalt is coal asphalt and/or petroleum asphalt; the softening point range of the binder is 120-280 ℃, the average particle size D50 is 2-50 μm, and the content of oxygen is lower than 5%; the mass ratio of the primary particles A to the binder is 100: 2-20; preferably, the average particle diameter D50 is 5-10 μm, and the mass ratio of the binder is 100: 5-7.
Preferably, in S3, a stirring mixer is adopted for mixing, the stirring speed is 20-100 rpm, and the mixing time is 1-3 hours; the granulation is carried out in a reactor with a stirring device or self rotation of a tank body under the protection of inert gas, the granulation reaction temperature is 400-650 ℃, the granulation reaction time is 2-8 hours, and the stirring speed is controlled at 15-40 rpm; the secondary particles C have an average particle diameter D50 of 12-20 μm. Preferably, the granulation reaction time is 4-6 hours, and the stirring speed is controlled at 25-30 rpm.
Preferably, in S4, the graphitization temperature is 2600-3000 ℃, and the graphitization time is 24-48 hours.
Preferably, in S5, the graphitized primary particles B and the graphitized secondary particles C are mixed in a mass ratio of 30-300: 100.
Preferably, the heating rate in the high-temperature modification, thermal coating and granulation processes is 0.5-20 ℃/min.
Preferably, the sieve meshes in S2, S3, S4 and S5 are all larger than 200 meshes.
The artificial graphite cathode material is prepared by the preparation method; the graphite cathode material of the artificial graphite cathode material has an average particle size of 10-30 mu m, a true density of more than 2.2g/cm3 and a specific surface area of 1-3 m2Per g, powder compaction greater than 1.8g/cm3The first reversible capacity is not less than 360mAh/g, the first coulombic efficiency is more than 92.5%, the capacity retention rate of 3C/0.2C is not less than 68%, and the capacity retention rate is more than 99% after circulation at 45 ℃ for 100 weeks (0.1C).
The negative electrode material of the lithium ion battery comprises the artificial graphite negative electrode material.
Compared with the prior art, the invention has the following beneficial effects: the invention provides a preparation method and a material of a graphite cathode material with high multiplying power, quick charge and high energy density through a way of compounding a primary particle coated graphitized product and a secondary particle graphitized product, and realizes the purpose of improving the energy density and multiplying power performance together, wherein the appearance of a primary particle body is specially shaped and optimized, a uniform thin layer coated hard carbon component is arranged on the surface of the primary particle body, and a graphitized coating layer has a more stable nano-micro structure while meeting the requirement of quick charge, and is beneficial to improving the stability of high-temperature circulation of the material; the secondary particles are reasonably granulated and regulated on the basis of the shaped primary particles, and the secondary particles have the characteristics of regular particle morphology and reasonable powder distribution. The problem of high anisotropy degree of a single component can be obviously improved after the two particle structures are combined. The preparation method has the advantages of simple process and easy quality control, can be used for large-scale commercial production, and the prepared graphite cathode has excellent electrochemical performance and good safety.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
And (3) crushing and shaping needle coke with the volatile component of 0.5% by adopting a rolling and grinding-shaping all-in-one machine to obtain primary particles A, and controlling the average particle size D50 of the primary particles A to be 8 mu m. Putting part of the primary particles A and a pyrolysis oil coating agent into a vacuum kneader according to the mass ratio of 100:8, kneading for 2 hours at the normal pressure of 120 ℃, then transferring into a vacuum mode of 250 ℃ for kneading for 4 hours, putting the kneaded material into a vertical reaction kettle, heating to 400 ℃ at the speed of 5 ℃/min under the protection of nitrogen, preserving heat for 2 hours, then heating to 550 ℃ at the speed of 3 ℃/min, preserving heat for 4 hours, cooling and screening to obtain primary particles B; uniformly mixing part of the primary particles A with petroleum asphalt with the softening point of 250 ℃ and the average particle size of 7 mu m according to the mass ratio of 100:10, then putting the mixture into a roller furnace, heating to 600 ℃ at the speed of 5 ℃/min under the protection of nitrogen, preserving the heat for 4 hours for granulation reaction, cooling and screening to obtain secondary particles C. And carrying out graphitization reaction on the primary particles B and the secondary particles C for 24 hours at 2800 ℃, and screening to obtain the graphitized primary particles B and the graphitized secondary particles C. Uniformly mixing the graphitized primary particles B and the graphitized secondary particles C according to the mass ratio of 30:70, and sieving again to obtain the high-energy-density multiplying power type artificial graphite product.
Example 2
And (3) crushing and shaping the needle coke with the volatile component of 1% by adopting a rolling and grinding-shaping all-in-one machine to obtain primary particles A, and controlling the average particle size D50 of the primary particles A to be 8 mu m. Putting part of the primary particles A and the sucrose coating agent into a vacuum kneader according to the mass ratio of 100:5, kneading for 2 hours at the normal pressure of 120 ℃, then transferring to a vacuum mode of 250 ℃ for kneading for 4 hours, putting the kneaded material into a vertical reaction kettle, heating to 400 ℃ at the speed of 5 ℃/min under the protection of nitrogen, preserving heat for 2 hours, then heating to 600 ℃ at the speed of 3 ℃/min, preserving heat for 2 hours, cooling and screening to obtain primary particles B; uniformly mixing part of the primary particles A with petroleum asphalt with the softening point of 150 ℃ and the average particle size of 7 mu m according to the mass ratio of 100:15, putting the mixture into a roller furnace, heating to 600 ℃ at the speed of 5 ℃/min under the protection of nitrogen, preserving the heat for 4 hours for granulation reaction, cooling and screening to obtain secondary particles C. And carrying out graphitization reaction on the primary particles B and the secondary particles C for 24 hours at 2800 ℃, and screening to obtain the graphitized primary particles B and the graphitized secondary particles C. Uniformly mixing the graphitized primary particles B and the graphitized secondary particles C according to the mass ratio of 40:60, and sieving again to obtain the high-energy-density multiplying-power artificial graphite product.
Example 3
Coarsely crushing needle coke with the volatile content of 5% to below 5 meshes, modifying at 900 ℃ for 4 hours, crushing and shaping by adopting a rolling mill-shaping integrated machine to obtain primary particles A, and controlling the average particle size D50 of the primary particles A to be 8 mu m. Putting part of the primary particles A and the phenolic resin oil coating agent into a vacuum kneader according to the mass ratio of 100:8, kneading for 2 hours at the normal pressure of 120 ℃, then transferring into a vacuum mode of kneading for 4 hours at the temperature of 250 ℃, putting the kneaded material into a vertical reaction kettle, heating to 400 ℃ at the speed of 5 ℃/min under the protection of nitrogen, preserving heat for 2 hours, then heating to 600 ℃ at the speed of 3 ℃/min, preserving heat for 2 hours, cooling and screening to obtain primary particles B; uniformly mixing part of the primary particles A with petroleum resin with the softening point of 150 ℃ and the average particle size of 9 mu m according to the mass ratio of 100:12, then putting the mixture into a roller furnace, heating to 550 ℃ at the speed of 5 ℃/min under the protection of nitrogen, preserving the heat for 4 hours for granulation reaction, cooling and screening to obtain secondary particles C. And carrying out graphitization reaction on the primary particles B and the secondary particles C for 24 hours at 2800 ℃, and screening to obtain the graphitized primary particles B and the graphitized secondary particles C. Uniformly mixing the graphitized primary particles B and the graphitized secondary particles C according to the mass ratio of 50:50, and sieving again to obtain the high-energy-density multiplying-power artificial graphite product.
Example 4
Coarsely crushing needle coke with the volatile content of 7% to below 5 meshes, modifying at the high temperature of 900 ℃ for 4 hours, crushing and shaping by adopting a rolling mill-shaping integrated machine to obtain primary particles A, and controlling the average particle size D50 of the primary particles A to be 8.5 mu m. Putting part of the primary particles A and a pyrolysis oil coating agent into a vacuum kneader according to the mass ratio of 100:8, kneading for 2 hours at the normal pressure of 120 ℃, then transferring into a vacuum mode of 250 ℃ for kneading for 4 hours, putting the kneaded material into a vertical reaction kettle, heating to 400 ℃ at the speed of 5 ℃/min under the protection of nitrogen, preserving heat for 2 hours, then heating to 550 ℃ at the speed of 3 ℃/min, preserving heat for 4 hours, cooling and screening to obtain primary particles B; uniformly mixing part of the primary particles A with petroleum asphalt with the softening point of 150 ℃ and the average particle size of 7 mu m according to the mass ratio of 100:13, putting the mixture into a roller furnace, heating to 600 ℃ at the speed of 5 ℃/min under the protection of nitrogen, preserving the heat for 4 hours for granulation reaction, cooling and screening to obtain secondary particles C. And carrying out graphitization reaction on the primary particles B and the secondary particles C for 24 hours at 2800 ℃, and screening to obtain the graphitized primary particles B and the graphitized secondary particles C. Uniformly mixing the graphitized primary particles B and the graphitized secondary particles C according to the mass ratio of 40:60, and sieving again to obtain the high-energy-density multiplying-power artificial graphite product.
Example 5
Coarsely crushing needle coke with the volatile content of 7% to below 5 meshes, modifying at the high temperature of 1000 ℃ for 4 hours, crushing and shaping by adopting a rolling mill-shaping integrated machine to obtain primary particles A, and controlling the average particle size D50 of the primary particles A to be 8.5 mu m. Putting part of the primary particles A and the sucrose coating agent into a vacuum kneader according to the mass ratio of 100:5, kneading for 2 hours at the normal pressure of 120 ℃, then transferring to a vacuum mode of 250 ℃ for kneading for 4 hours, putting the kneaded material into a vertical reaction kettle, heating to 400 ℃ at the speed of 5 ℃/min under the protection of nitrogen, preserving heat for 2 hours, then heating to 600 ℃ at the speed of 3 ℃/min, preserving heat for 2 hours, cooling and screening to obtain primary particles B; uniformly mixing part of the primary particles A with petroleum asphalt with the softening point of 250 ℃ and the average particle size of 7 mu m according to the mass ratio of 100:8, putting the mixture into a roller furnace, heating to 600 ℃ at the speed of 5 ℃/min under the protection of nitrogen, preserving the heat for 4 hours for granulation reaction, cooling and screening to obtain secondary particles C. And carrying out graphitization reaction on the primary particles B and the secondary particles C for 24 hours at 2800 ℃, and screening to obtain the graphitized primary particles B and the graphitized secondary particles C. Uniformly mixing the graphitized primary particles B and the graphitized secondary particles C according to the mass ratio of 50:50, and sieving again to obtain the high-energy-density multiplying-power artificial graphite product.
Example 6
Coarsely crushing needle coke with the volatile component of 9% to below 5 meshes, modifying at the high temperature of 1000 ℃ for 4 hours, crushing and shaping by adopting a rolling mill-shaping integrated machine to obtain primary particles A, and controlling the average particle size D50 of the primary particles A to be 8 mu m. Putting part of the primary particles A and a pyrolysis oil coating agent into a vacuum kneader according to the mass ratio of 100:8, kneading for 2 hours at the normal pressure of 120 ℃, then transferring into a vacuum mode of 250 ℃ for kneading for 4 hours, putting the kneaded material into a vertical reaction kettle, heating to 400 ℃ at the speed of 5 ℃/min under the protection of nitrogen, preserving heat for 2 hours, then heating to 550 ℃ at the speed of 3 ℃/min, preserving heat for 4 hours, cooling and screening to obtain primary particles B; uniformly mixing part of the primary particles A with petroleum resin with the softening point of 150 ℃ and the average particle size of 9 mu m according to the mass ratio of 100:12, then putting the mixture into a roller furnace, heating to 550 ℃ at the speed of 5 ℃/min under the protection of nitrogen, preserving the heat for 4 hours for granulation reaction, cooling and screening to obtain secondary particles C. And carrying out graphitization reaction on the primary particles B and the secondary particles C for 24 hours at 2800 ℃, and screening to obtain the graphitized primary particles B and the graphitized secondary particles C. Uniformly mixing the graphitized primary particles B and the graphitized secondary particles C according to the mass ratio of 50:50, and sieving again to obtain the high-energy-density multiplying-power artificial graphite product.
Comparative example 1
Coarsely crushing needle coke with the volatile content of 7% to below 5 meshes, modifying at the high temperature of 900 ℃ for 4 hours, crushing and shaping by adopting a rolling mill-shaping integrated machine to obtain primary particles A, and controlling the average particle size D50 of the primary particles A to be 8.5 mu m. Putting the primary particles A and a pyrolysis oil coating agent into a vacuum kneader according to the mass ratio of 100:8, kneading for 2 hours at the normal pressure of 120 ℃, then transferring to a vacuum mode of 250 ℃ for kneading for 4 hours, putting the kneaded material into a vertical reaction kettle, heating to 400 ℃ at the speed of 5 ℃/min under the protection of nitrogen, preserving heat for 2 hours, then heating to 550 ℃ at the speed of 3 ℃/min, preserving heat for 4 hours, cooling and screening to obtain primary particles B; the primary particles B were graphitized at 2800 ℃ for 24 hours and sieved to obtain comparative graphite material 1.
Comparative example 2
Coarsely crushing needle coke with the volatile content of 7% to below 5 meshes, modifying at the high temperature of 900 ℃ for 4 hours, crushing and shaping by adopting a rolling mill-shaping integrated machine to obtain primary particles A, and controlling the average particle size D50 of the primary particles A to be 8.5 mu m. Uniformly mixing the primary particles A with petroleum asphalt with the softening point of 150 ℃ and the average particle size of 7 mu m according to the mass ratio of 100:13, putting the mixture into a roller furnace, heating to 600 ℃ at the speed of 5 ℃/min under the protection of nitrogen, preserving the heat for 4 hours to carry out granulation reaction, cooling and screening to obtain secondary particles C. The secondary particles C were graphitized at 2800℃ for 24 hours and sieved to obtain comparative graphite material 2.
Comparative example 3
And (3) crushing and shaping needle coke with the volatile component of 0.5% by adopting a rolling and grinding-shaping all-in-one machine to obtain primary particles A, and controlling the average particle size D50 of the primary particles A to be 8 mu m. Uniformly mixing part of the primary particles A with petroleum asphalt with the softening point of 250 ℃ and the average particle size of 7 mu m according to the mass ratio of 100:10, then putting the mixture into a roller furnace, heating to 600 ℃ at the speed of 5 ℃/min under the protection of nitrogen, preserving the heat for 4 hours for granulation reaction, cooling and screening to obtain secondary particles C. And carrying out graphitization reaction on the primary particles A and the secondary particles C for 24 hours at 2800 ℃, and screening to obtain the graphitized primary particles A and the graphitized secondary particles C. Uniformly mixing the graphitized primary particles A and the graphitized secondary particles C according to the mass ratio of 30:70, and sieving again to obtain the comparative graphite material 3.
The graphite negative electrode materials of examples 1 to 6 and comparative examples 1 to 3 were tested for particle size, true density, specific surface area and compacted density, respectively, and the results are shown in table 1. The name and model of the instrument used for the test are as follows: the particle size test adopts a Malvern laser particle size analyzer MS 3000; the real density test adopts a kangta UltraPYC 1200e type full-automatic real density analyzer; the specific surface area test adopts an American MicTriStar type II specific surface area tester; the compaction density test employed an electronic pressure tester UTM 7305.
The graphite anode materials in examples 1 to 6 and comparative examples 1 to 3 were subjected to first specific capacity, first coulombic efficiency, rate and high-temperature cycle performance tests by using a half-cell test method, which comprises the following steps: preparing 7% polyvinylidene fluoride solution by taking N-methyl pyrrolidone as a solvent, uniformly mixing a graphite negative electrode material, polyvinylidene fluoride and a conductive agent Super-P according to the mass ratio of 91:7:2, coating the mixture on a copper foil, and putting the coated pole piece into a vacuum drying oven at the temperature of 100 ℃ for vacuum drying for 4 hours for later use. Then assembling the semi-cell into a CR2032 type button cell in an argon-filled German Michelona glove box, taking a three-component mixed solvent of 1mol/L LiPF6 as an electrolyte and a metal lithium sheet as a counter electrode according to a mixed liquid of EC: DMC: EMC ═ 1:1:1 (volume ratio), and carrying out electrochemical performance test on the assembled semi-cell on a blue-electricity cell test system, wherein the charging and discharging voltage range is 5mV to 2.0V. The resulting half-cell performance parameters are shown in table 1.
TABLE 1
By combining the electrical property data of the graphite cathode materials in examples 1 to 6, it can be known that the type of the graphitized primary particle coating agent has a large influence on the quick charging capability of the final graphite cathode. As is clear from Table 1, the graphite negative electrode materials obtained in examples 1 to 6 had an average particle diameter of 10 to 30 μm, a true density of more than 2.2g/cm3, and a specific surface area of 1 to 3m2(iv)/g, powder compaction (standard 5 ton pressure) greater than 1.8g/cm3The first reversible capacity is not less than 360mAh/g, the first coulombic efficiency is more than 92.5%, the capacity retention rate of 3C/0.2C is not less than 68%, the capacity retention rate is more than 99% after circulation at 45 ℃ for 100 weeks (0.1C), and excellent quick charge and circulation performances are shown.
In contrast, comparative example 1 and comparative example 2 are single-component compositions, which are respectively insufficient in capacity and rate fast-charging, and the fast-charging performance is seriously weakened because the primary particles in comparative example 3 are not coated. By combining the sample of the embodiment, the primary particles are coated and then compounded with the secondary particles, so that the interface stability of the material can be obviously improved, and the comprehensive electrical property of the material can be improved.
The invention also provides a lithium ion battery, and the negative electrode material of the lithium ion battery adopts the artificial graphite negative electrode material, so that the lithium ion battery has high capacity, good cycle and excellent quick charge performance.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.
Claims (9)
1. A preparation method of a high-energy density multiplying artificial graphite negative electrode material is characterized by comprising the following steps:
s1, directly coarsely crushing and grinding raw coke or coarsely crushing and grinding raw coke after high-temperature modification, and shaping to obtain primary particles A;
s2, kneading the primary particles A and an organic carbon source, performing dynamic thermal coating, and screening to obtain primary particles B; the kneading adopts a vacuum kneading machine; kneading is carried out in 2 sections, the kneading temperature of the first section is 100-150 ℃, and the kneading time is 1-4 hours; the kneading temperature of the second stage is 180-280 ℃, the kneading time is 2-4 hours, and the vacuum degree is not higher than 10 kPa; the dynamic thermal coating is carried out in a vertical reaction kettle or a horizontal reaction kettle with a stirring device under the protection of inert gas at the temperature of 450-700 ℃ for 1-10 hours, and the stirring speed is 5-50 rpm; the inert gas is 1 or the combination of at least 2 of nitrogen, helium and argon; the average particle size D50 of the primary particles B is 5-15 mu m, the thickness of a coating layer of amorphous carbon on the surfaces of the primary particles B is 0.1-1 mu m, and the atomic ratio concentration of oxygen atoms on the surfaces of the primary particles B is 2-5%;
s3, uniformly mixing the primary particles A with the binder, placing the mixture into a granulation reaction kettle for granulation, and screening to obtain secondary particles C;
s4, performing graphitization treatment on the primary particles B and the secondary particles C respectively, and screening to obtain graphitized primary particles B and graphitized secondary particles C;
and S5, uniformly mixing the graphitized primary particles B and the graphitized secondary particles C in proportion, and screening to obtain a finished product.
2. The method for preparing the artificial graphite anode material according to claim 1, characterized in that: in S1, when the raw coke is green coke with a volatile content of more than 3%, coarsely breaking, modifying at high temperature, and grinding into powder; when the raw coke is calcined coke with the volatile component not more than 3%, directly coarsely crushing and grinding into powder; the raw coke can be 1 or the combination of at least 2 of needle coke, common coke and asphalt coke;
wherein, the coarse crushing adopts a jaw crusher or a back hammer crusher, and the size of crushed particles is controlled to be less than 5 meshes; the ground powder is crushed by a mechanical mill or a roller mill; the high-temperature modification temperature is 800-1400 ℃, and the reaction time is 1-8 hours; the shaping adopts a physical grinding method shaping machine; the primary particles A have an average particle diameter D50 of 5 to 15 [ mu ] m and an aspect ratio of 0.5 to 2.
3. The method for preparing the artificial graphite anode material according to claim 1, characterized in that: s2, the organic carbon source at least consists of 4 elements of carbon, hydrogen, oxygen and nitrogen, wherein the oxygen mass ratio content is not less than 3%, and the organic carbon source is 1 or at least 2 of low-temperature asphalt, monosaccharide, soluble polysaccharide, aromatic hydrocarbon pyrolysis oil, ethylene tar or liquid resin with the softening point lower than 30 ℃; the mass ratio of the primary particles A to the organic carbon source is 100: 5-15.
4. The method for preparing the artificial graphite anode material according to claim 1, characterized in that: s3, the binder is asphalt and/or petroleum resin, wherein the asphalt is coal asphalt and/or petroleum asphalt; the softening point range of the binder is 120-280 ℃, the average particle size D50 is 2-50 μm, and the content of oxygen is lower than 5%; the mass ratio of the primary particles A to the binder is 100: 2-20.
5. The method for preparing the artificial graphite anode material according to claim 1, characterized in that: in S3, a stirring mixer is adopted for mixing, the stirring speed is 20-100 rpm, and the mixing time is 1-3 hours; the granulation is carried out in a reactor with a stirring device or self rotation of a tank body under the protection of inert gas, the granulation reaction temperature is 400-650 ℃, the granulation reaction time is 2-8 hours, and the stirring speed is controlled at 15-40 rpm; the secondary particles C have an average particle diameter D50 of 12-20 μm.
6. The method for preparing the artificial graphite anode material according to claim 1, characterized in that: in S4, the graphitization temperature is 2600-3000 ℃, and the graphitization time is 24-48 hours.
7. The method for preparing the artificial graphite anode material according to claim 1, characterized in that: in S5, the graphitized primary particles B and the graphitized secondary particles C are mixed according to the mass ratio of 30-300: 100.
8. An artificial graphite negative electrode material, characterized in that the artificial graphite negative electrode material is prepared by the preparation method according to any one of claims 1 to 7; the graphite cathode material of the artificial graphite cathode material has an average particle size of 10-30 mu m, a true density of more than 2.2g/cm3 and a specific surface area of 1-3 m2Per g, powder compaction greater than 1.8g/cm3The first reversible capacity is not less than 360mAh/g, the first coulombic efficiency is more than 92.5%, the capacity retention rate of 3C/0.2C is not less than 68%, and the capacity retention rate is more than 99% after 100-week circulation at 45 ℃ under 0.1C.
9. A lithium ion battery, wherein the lithium ion battery negative electrode material comprises the artificial graphite negative electrode material according to claim 8.
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