CN117776171A - Coal-based graphite anode material and preparation method and application thereof - Google Patents
Coal-based graphite anode material and preparation method and application thereof Download PDFInfo
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- RHZUVFJBSILHOK-UHFFFAOYSA-N anthracen-1-ylmethanolate Chemical compound C1=CC=C2C=C3C(C[O-])=CC=CC3=CC2=C1 RHZUVFJBSILHOK-UHFFFAOYSA-N 0.000 description 1
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Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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Abstract
The invention provides a coal-based graphite anode material, and a preparation method and application thereof, wherein the preparation method comprises the following steps: (1) Crushing and shaping a coal raw material, and then performing graphitization treatment to obtain a first matrix; (2) Mixing asphalt with carbon-based particles to obtain a second matrix, wherein the carbon-based particles are graphene and/or carbon nanotubes; (3) Mixing the second matrix with resin to obtain a third matrix; (4) And mixing the first matrix with the third matrix, carbonizing at high temperature, sieving, and performing demagnetizing treatment to obtain the coal-based graphite anode material. According to the technical scheme, the problems that the graphite anode material in the prior art is complex in processing process and high in cost, and expansion and falling of a coating structure cannot be considered while the capacity and multiplying power performance of the material are ensured can be solved.
Description
Technical Field
The invention relates to the technical field of negative electrode materials, in particular to a coal-based graphite negative electrode material, and a preparation method and application thereof.
Background
At present, in the lithium ion battery industry, graphite materials are commonly used for the negative electrode of a battery due to the excellent capacity and multiplying power performance, and although the graphite negative electrode is very mature, a plurality of problems still exist in the practical application process.
In the prior art, in order to improve the quick charging performance of the graphite material, soft carbon or hard carbon is generally used to coat the graphite outer layer. However, in practical industrialized application, various performance indexes of the material are considered, so that factors such as capacity, initial effect, expansion, multiplying power performance, cost and the like of the material are considered, and the problems of capacity reduction, expansion and falling and the like caused by coating cannot be effectively solved by the existing technical scheme.
As disclosed in patent CN103346294B, a preparation method of an artificial graphite negative electrode material is disclosed, which comprises the steps of crushing, spheroidizing and shaping artificial graphite, coating the crushed artificial graphite and a superfine coating material in a mechanical fusion machine, and then roasting and graphitizing the crushed artificial graphite to obtain the artificial graphite negative electrode material. The invention can improve the multiplying power performance of the anode material, but because a large amount of asphalt is used, a soft carbon embedded object is formed, so that the capacity of the anode material is reduced.
As further disclosed in patent CN117012936a, a high energy density fast-charging graphite negative electrode material, a preparation method thereof, a negative electrode sheet and a battery thereof, the graphite particles are granulated by using modified asphalt to obtain secondary particles formed by bonding a hard carbon/soft carbon composite amorphous carbon crosslinked structure, the secondary particles are coated by using a mixture of resin and asphalt to form a layer of hard carbon/soft carbon composite amorphous carbon coating layer, and the graphitization degree of the hard carbon/soft carbon composite amorphous carbon is between that of soft carbon and hard carbon, so that the obtained graphite negative electrode material has high energy density and fast charging performance. The invention can improve the multiplying power performance of the anode material, but requires the double coating of the soft carbon/hard carbon composite material, and also provides requirements on the size of primary particles.
Disclosure of Invention
The invention provides a coal-based graphite anode material, a preparation method and application thereof, which are used for solving the problems that the processing process of the graphite anode material in the prior art is complex, the cost is high, and the expansion and falling of a coating structure can not be considered while the capacity and the multiplying power performance of the material are ensured.
According to one aspect of the invention, there is provided a method for preparing a coal-based graphite anode material, the method comprising the steps of:
(1) Crushing and shaping a coal raw material, and then performing graphitization treatment to obtain a first matrix;
(2) Mixing asphalt with carbon-based particles to obtain a second matrix, wherein the carbon-based particles are graphene and/or carbon nanotubes;
(3) Mixing the second matrix with resin to obtain a third matrix;
(4) And mixing the first matrix with the third matrix, carbonizing at high temperature, sieving, and performing demagnetizing treatment to obtain the coal-based graphite anode material.
Further, in the step (1), the pulverized and shaped coal raw material is subjected to graphitization treatment satisfying the following conditions: the vitrinite reflectance of the crushed and shaped coal raw material is more than or equal to 1.5%, the volatile component is less than or equal to 15wt% and the ash content is less than or equal to 15wt%; and/or the graphitization treatment temperature is 2800 ℃ to 3200 ℃, preferably 3000 ℃.
Further, in the step (1), the obtained substrate needs to satisfy the following conditions: the graphitization degree of the first matrix is 80-95; and/or the matrix-particle size D50 is between 5 and 20 μm; and/or Lc is less than or equal to 30nm and less than or equal to 70nm, la is less than or equal to 50nm and less than or equal to 120nm.
Further, in the step (1), the coal raw material is crushed by any one or more of roll grinding, impact grinding, rotary wheel grinding or air flow grinding, and the crushed coal raw material is shaped by a horizontal shaping machine and/or a vertical shaping machine.
Further, in the step (2), the asphalt is high-temperature coated asphalt or mesophase asphalt, and the asphalt needs to meet the following conditions: the softening point of the bitumen is between 120 ℃ and 300 ℃, preferably 260 ℃; and/or the coking value of the asphalt is more than or equal to 50%, preferably 56%; and/or the ash content of the asphalt is less than or equal to 0.5wt%, preferably 0.3wt%; and/or the quinoline insoluble content of the asphalt is less than or equal to 0.5wt%, preferably 0.2wt%.
Further, in step (2), the graphene needs to satisfy the following conditions: the graphene content of the graphene layers with the number of 1-3 is more than or equal to 80wt%, preferably 85%; and/or the aspect ratio of the graphene is greater than or equal to 300, preferably 500; and/or, the conductivity of the graphene is more than or equal to 0.5X10) 5 s/m, preferably 1X 10 5 s/m。
Further, in the step (2), the carbon nanotubes are single-walled carbon nanotubes or multi-walled carbon nanotubes, and the following conditions are required to be satisfied: the diameter of the carbon nano tube is less than or equal to 20nm, preferably 10nm; and/or the aspect ratio of the carbon nanotubes is greater than 100:1 and less than 1000:1, preferably 150:1; and/or the conductivity of the carbon nano tube is greater than or equal to 0.1 multiplied by 10 5 s/m, preferably 0.5X10 5 s/m。
Further, in the step (2), the weight ratio of the matrix asphalt to the graphene to the carbon nano tube is (1-0.95): 0-0.025; preferably, the carbon-based particles are a mixture of graphene and carbon nanotubes, and the weight ratio of the graphene to the carbon nanotubes is 1-1.2.
Further, in the step (3), the resin is one or more of phenolic resin, urea resin, epoxy resin, polyurethane resin, polyester resin and polyacrylic resin, and the ratio of the second matrix to the resin is preferably (90-50): 10-50.
Further, in the step (3), the second matrix and the resin are mixed by one or more of VC, coulter or ribbon to obtain a third matrix.
Further, in the step (4), the mixing mode of the first matrix and the third matrix is one or more of VC mixing, coulter mixing or spiral belt mixing, and the mixing ratio of the first matrix to the third matrix is (1-0.9) (0.02-0.1).
Further, in the step (4), the following conditions are required for high-temperature carbonization: the high-temperature carbonization temperature is 950-1500 ℃, preferably 1100 ℃; and/or the heating rate in the high-temperature carbonization process is 1-10 ℃/min, preferably 10 ℃/min; and/or the high temperature carbonization time is 5 to 20 hours, preferably 10 hours.
According to another aspect of the invention, a coal-based graphite anode material is provided, and the coal-based graphite anode material is prepared by the preparation method.
Further, the coal-based graphite anode material comprises a substrate 10 and a coating layer 20, wherein the coating layer 20 is coated on the outer surface of the substrate 10, the coating layer 20 is prepared from a substrate III, and the thickness of the coating layer 20 is 5-150 nm.
According to still another aspect of the present invention, a use of the coal-based graphite anode material described above as an electrode material.
By applying the technical scheme of the invention, the coating layer of the coal-based graphite anode material comprises a soft carbon structure formed by asphalt and a hard carbon structure formed by graphene and carbon nanotubes, so that the gram capacity and the quick charge performance of the anode material after coating can be ensured, meanwhile, the graphite anode material only needs to be coated once, the synthesis process is simple, after coating, the carbon nanotubes and the graphene in the matrix III still maintain the original structure, the pole piece falling phenomenon caused by charging and expanding the material can be effectively relieved, the compaction density of the material can be properly improved, and the problem that the anode material is expanded and falls after multiple cycles is solved.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention. In the drawings:
fig. 1 shows a schematic structural diagram of a coal-based graphite anode material provided according to an embodiment of the present invention.
Wherein the above figures include the following reference numerals:
10. a base;
20. a coating layer;
21. a soft carbon structure;
22. a hard carbon structure;
23. a graphene;
24. carbon nanotubes.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. The following description of at least one exemplary embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
According to the description in the background section of the invention, the prior art is used for coating graphite to improve the electrochemical performance of a graphite anode material, and meanwhile, the capacity and the multiplying power performance of the material cannot be considered. Aiming at the problems, the invention provides a preparation method of a coal-based graphite anode material, which comprises the following steps: (1) Crushing and shaping a coal raw material, and then performing graphitization treatment to obtain a first matrix; (2) Mixing asphalt with carbon-based particles to obtain a second matrix, wherein the carbon-based particles are graphene and/or carbon nanotubes; (3) Mixing the second matrix with resin to obtain a third matrix; (4) And mixing the first matrix with the third matrix, carbonizing at high temperature, sieving, and performing demagnetizing treatment to obtain the coal-based graphite anode material.
Although the carbon coating layer is formed on the surface of the graphite raw material, the quick charge performance of the graphite negative electrode material can be improved, the soft carbon embedding substance formed by using a large amount of asphalt coating layer can cause the gram capacity of the graphite negative electrode to be reduced; the asphalt is modified by the modifier and the resin, the structural consistency and uniformity of the coated carbon layer can be improved by wrapping soft carbon and hard carbon, the isotropy of the material is improved, the multiplying power performance and gram capacity of the material are improved, the graphite particles are required to be coated for a plurality of times, the specific surface area of the material is reduced, the multiplying power performance and gram capacity are ensured, the requirement on the granularity of the graphite particles is high in the mode, the preparation process is complex, and the cost is high. The application creatively adds carbon-based particles into asphalt, and mixes and coats the asphalt with resin on a matrix, wherein the carbon-based particles are selected from one or more of carbon nano tubes or graphene. On one hand, the carbon-based particle material has micropores and mesopores, the specific surface area is higher, the electrolyte has higher transmission rate in the negative electrode material provided by the application, the electrochemical performance of the graphite negative electrode material can be improved, and the problem of capacity reduction of the negative electrode material caused by soft carbon chimeric is solved; on the other hand, the resin of the coating matrix III in the application becomes hard carbon after carbonization, so that the quick charge performance of the material can be effectively improved, the gram capacity of the material can also be improved, the original structure of the carbon-based granular material after high-temperature carbonization can be still maintained, the pole piece falling phenomenon caused by charging expansion of the material can be relieved, and the compaction density of the material can be properly improved. Therefore, the graphite anode material provided by the application only needs to be coated once during preparation, the synthesis process is simple, the gram capacity and the quick charge performance of the coated anode material can be ensured, and the problem that the anode material is expanded and falls off after multiple cycles is solved.
Further, in the step (1), the pulverized and shaped coal raw material is subjected to graphitization treatment satisfying the following conditions: the vitrinite reflectance of the crushed and shaped coal raw material is more than or equal to 1.5%, the volatile component is less than or equal to 15wt% and the ash content is less than or equal to 15wt%, so as to ensure the coal quality degree of the coal raw material and reduce the impurities in the first matrix; the graphitization treatment temperature is 2800-3200 ℃, preferably 3000 ℃, so as to reduce the interlayer spacing of graphite, thereby further improving the quick charging performance of the coal raw material matrix. The vitrinite reflectance of the crushed coal raw material is measured by a measuring method in the national standard GB/T40485-2021, and the volatile matters and ash are measured by a measuring method in the national standard GB/T212-2008.
Further, in the step (1), in order to ensure the conductivity of the first substrate, the first substrate needs to be graphitized to 80-95; to ensure an average particle size of matrix one, matrix one particle size D50 is between 5-20 μm to ensure an average matrix one particle size; in order to further improve the conductivity of the coal raw material matrix, the width of the graphite particles in the direction a is La, the width of the graphite particles in the direction c is Lc, and the width of the graphite particles in the direction a is La, wherein Lc is 30nm or less and 70nm or less, and La is 50nm or less and 120nm or less.
In order to ensure the uniformity of crushing and decomposing the coal raw material, in the step (1), the coal raw material is crushed by any one or more of rolling mill, impact mill, rotary wheel mill or air flow mill, and the crushed coal raw material is shaped by a horizontal shaper and/or a vertical shaper to ensure the specific surface area of the first matrix.
In order to further improve the compatibility of the graphite anode material with the electrolyte, in the step (2), the asphalt is high-temperature coated asphalt or mesophase asphalt, preferably high-temperature coated asphalt; in order to ensure the high temperature performance of the graphite anode material, the softening point of the asphalt is between 120 ℃ and 300 ℃, preferably 260 ℃; in order to ensure the thermal stability of the graphite anode material, the coking value of asphalt is more than or equal to 50%, preferably 56%; in order to reduce the influence of impurities in the asphalt on the conductivity of the anode material, the ash content of the asphalt is less than or equal to 0.5wt percent, preferably 0.3wt percent; in order to further reduce the effect of impurities, the quinoline insoluble content of the asphalt is less than or equal to 0.5wt%, preferably 0.2wt%.
In order to ensure the conductivity of the graphite anode material, in the step (2), the graphene is required to meet the requirement that the graphene content of 1-3 layers is more than or equal to 80wt%, preferably 85%; in order to further improve the conductivity of the graphite anode material, the diameter-thickness ratio of the graphene is more than or equal to 300, preferably 500; in order to further ensure the conductivity of the cathode material, the conductivity of graphene is more than or equal to 0.5X10 5 s/m, preferably 1X 10 5 s/m。
In order to ensure uniform conductivity of the carbon-based particles, in the step (2), the carbon nanotubes are single-walled carbon nanotubes or multi-walled carbon nanotubes, preferably single-walled carbon nanotubes: in order to ensure the conductivity of the carbon nanotubes, the diameter of the carbon nanotubes is less than or equal to 20nm, preferably 10nm; when the aspect ratio of the carbon nanotube is small, the transportation of electrons in the carbon nanotube is affected by the end of the carbon nanotube, and when the length of the carbon nanotube is longerWhen the ratio is large, the transportation of electrons in the carbon nanotubes is influenced by the side walls of the carbon nanotubes, and in order to ensure the efficiency of transporting electrons by the carbon nanotubes, the length-diameter ratio of the carbon nanotubes is set to be more than 100:1 and less than 1000:1, preferably 150:1; in order to ensure the conductivity of the graphite anode material, the conductivity of the carbon nano tube is more than or equal to 0.1 multiplied by 10 5 s/m, preferably 0.5X10 5 s/m。
Further, in order to ensure gram capacity and capacity retention rate of the graphite anode material, in the step (2), the weight ratio of the matrix asphalt to the graphene to the carbon nano tube is (1-0.95): (0-0.025), preferably, the carbon-based particles are a mixture of the graphene and the carbon nano tube, and the weight ratio of the graphene to the carbon nano tube is 1-1.2.
Further, in order to form the coating layer into a composite coating layer of soft carbon and hard carbon, in the step (3), a resin material is added to enable the resin material to form a hard carbon structure after high-temperature carbonization, so that the quick charge performance of the anode material is improved, the resin is one or more of phenolic resin, urea-formaldehyde resin, epoxy resin, polyurethane resin, polyester resin and polyacrylic resin, preferably phenolic resin, and the ratio of the second matrix to the resin is (90-50) (10-50).
In order to ensure that the second matrix and the resin can be fully mixed, in the step (3), the second matrix and the resin are mixed by one or more of VC, coulter or ribbon mixing to obtain the third matrix.
In order to ensure that the matrix III and the matrix III can be fully mixed, in the step (4), the mixing mode of the matrix I and the matrix III is one or more of VC mixing, coulter mixing or spiral belt mixing, and the mixing proportion of the matrix I and the matrix III is (1-0.9) (0.02-0.1).
Further, in the step (4), in order to ensure that the high-temperature carbonization can decompose the unstable substances of the first matrix and the third matrix, the high-temperature carbonization temperature is 950-1500 ℃, preferably 1100 ℃; in order to decompose three unstable substances of the first substrate and the second substrate as much as possible and reduce the content of impurities in the graphite anode material, the temperature rising rate in the high-temperature carbonization process is 1-10 ℃/min, preferably 10 ℃/min; in order to further reduce the influence of impurities in the graphite anode material on the overall material performance, the high-temperature carbonization time is 5-20 hours, preferably 10 hours, so as to improve the carbonization degree.
The invention further provides a coal-based graphite anode material, which is prepared by the preparation method.
Further, as shown in fig. 1, the coal-based graphite anode material comprises a substrate 10 and a coating layer 20, wherein the coating layer 20 is coated on the outer surface of the substrate 10, the coating layer 20 is prepared from a substrate III, and the thickness of the coating layer 20 is 5-150 nm so as to ensure the gram capacity of the coal-based graphite anode material. According to the coal-based graphite anode material provided by the invention, the substrate 10 can be coated by the soft carbon structure 21 formed by asphalt, the graphene 23, the carbon nano tube 24 and the hard carbon structure 22 formed by resin, so that the gram capacity and the multiplying power performance of the coated coal-based graphite anode material are improved, the coal-based graphite anode material only needs to be coated once, the synthesis process is simple, meanwhile, the phenomenon that the electrode piece falls off can be relieved by the graphene 23 and the carbon nano tube 24, and the problem that the coal-based graphite anode material expands and falls off after multiple cycles is solved.
In the embodiment of the invention, by setting the thickness of the coating layer 20 to be 5-150 nm, when the thickness of the coating layer 20 is less than 5nm, the coating layer 20 has limited improvement on gram capacity of the anode material; when the thickness of the coating layer 20 is greater than 150nm, the first efficiency and gram capacity of the anode material are obviously reduced as the thickness of the coating layer 20 is continuously increased, and the first efficiency of the anode material can be ensured while the gram capacity and the capacity retention rate of the anode material are improved by setting the thickness of the coating layer 20 to 5-150 nm.
The invention also provides an application of the coal-based graphite anode material, and the coal-based graphite anode material is used as an electrode material.
The present application is described in further detail below in conjunction with specific embodiments, which should not be construed as limiting the scope of the claims.
Example 1
The preparation method of the coal-based graphite anode material comprises the following steps:
(1) Pulverizing anthracite raw materials by roll milling, shaping the pulverized coal raw materials by a horizontal shaping machine to obtain raw material particles with vitrinite reflectivity of 4.5%, volatile matter of 7% and ash content of 3%, and graphitizing the raw material particles at 3000 ℃ to obtain a first matrix, wherein the graphitization degree of the first matrix is 90, the granularity D50 is 8.1 mu m, the width La of graphite particles in the a direction is 70nm, and the width Lc of the graphite particles in the c direction is 42nm.
(2) Mixing the coated asphalt, graphene and carbon nanotubes to obtain a second matrix, wherein the coated asphalt has a softening point of 260 ℃, a coking value of 56%, ash content of 0.3wt%, quinoline insoluble content of 0.3wt%, graphene content of 1-3 layers in the graphene of 85wt%, diameter-thickness ratio of 500, and conductivity of 1.0×10 5 s/m, the carbon nano tube is a single-walled carbon nano tube, the diameter of the single-walled carbon nano tube is 10nm, the length-diameter ratio is 150:1, and the conductivity is 0.5X10 5 s/m, the weight ratio of asphalt, graphene and carbon nano tube is 95:2.5:2.5.
(3) Mixing the second matrix with phenolic resin through VC to obtain a third matrix, wherein the mass ratio of the second matrix to the phenolic resin is 9:1.
(4) Mixing the first matrix and the third matrix in a mass ratio of 9:1, carbonizing at a high temperature for 10 hours, sieving, and performing demagnetizing treatment to obtain the coal-based graphite anode material, wherein the high-temperature carbonization temperature is 110 ℃, and the heating rate is 10 ℃/min.
Example 2
The only difference from example 1 is that: in the step (4), the mass ratio of the first substrate to the third substrate is 10:1.
Example 3
The only difference from example 1 is that: in the step (4), the mass ratio of the first substrate to the third substrate is 45:1.
Example 4
The only difference from example 1 is that: in the step (4), the mass ratio of the first substrate to the third substrate is 50:1.
Example 5
The only difference from example 1 is that: in the step (4), the mass ratio of the first substrate to the third substrate is 100:1.
Example 6
The only difference from example 1 is that: in the step (2), the weight ratio of the matrix asphalt to the graphene to the carbon nano tubes is 94.75:2.5:2.75.
Example 7
The only difference from example 1 is that: in the step (2), the weight ratio of the matrix asphalt to the graphene to the carbon nanotubes is 94.5:2.5:3.
Comparative example 1
(1) Crushing an ultra-high power graphite joint with granularity smaller than 4mm, and spheroidizing the crushed ultra-high power graphite joint by an automatic spheroidizing system consisting of 4 stages of 90kw airflow vortex ultra-micro crushers, 8 stages of 70kw airflow vortex ultra-micro crushers and 8 stages of 30kw airflow vortex ultra-micro crushers which are connected in series, wherein the median diameter of the spheroidized artificial graphite particles is 22 mu m, and the specific surface area is 4.3m 2 Per gram, tap density of 0.95g/m 3 ；
(2) Crushing the mesophase pitch by using an air flow crusher, wherein the median diameter of the crushed mesophase pitch is 3.6 mu m;
(3) Weighing 30kg of graphite micropowder in the step (1), 3.5kg of asphalt micropowder in the step (2), placing the mixture in a conical mixer for coarse mixing for 10min, discharging, placing the coarse mixed material in a mechanical fusion machine, starting the mechanical fusion machine, and fusing at a rotating speed of 800r/min for 15min to coat asphalt on the surface of graphite, and discharging;
(4) Filling the graphite powder coated with asphalt prepared in the step (3) into a graphite crucible, placing the graphite crucible into a ring type roasting furnace for roasting, wherein the highest temperature of the roasting is 1200 ℃, and preserving heat for 20 hours at the highest temperature;
(5) And (3) loading the baked graphite powder obtained in the step (4) into a graphite crucible, and graphitizing at 2800 ℃ to obtain the graphite anode material.
Comparative example 2
(1) Drying the raw petroleum needle coke raw material in a vacuum drying oven, coarsely crushing the raw petroleum needle coke raw material in a roll mill, and crushing the raw petroleum needle coke raw material in a mechanical mill until the D50 is 8-10 mu m; wherein, the volatile component of the petroleum needle coke raw material is 8 percent and the ash content is 0.2 percent.
(2)Carrying out high-temperature graphitization treatment on the crushed raw material of the petroleum raw needle coke in a crucible furnace for 48 hours at 3000 ℃ to obtain artificial graphite A, wherein the granularity of the artificial graphite A is 1-45 mu m, the D50 is 8-10 mu m, and the tap density is more than or equal to 1.0g/cm 3 ，BET≤2.5m 2 And/g, the capacity is larger than or equal to 352mAh/g.
(3) Mixing the artificial graphite A, the phosphoric acid solution and the boric acid solution according to the mass ratio of 100:5:5, and carrying out heat treatment for 4 hours in a horizontal coating kettle at 550 ℃ to obtain artificial graphite B; wherein the concentration of the phosphoric acid solution is 30%, the concentration of the boric acid solution is 27%, and the mass ratio of the artificial graphite A to the phosphoric acid to the boric acid is 100:1.5:1.35; the D50 of the artificial graphite B is 8-10 mu m.
(4) Mixing the artificial graphite B and polyvinylpyrrolidone in a mass ratio of 100:12, carrying out heat treatment for 2 hours at 550 ℃ in a horizontal coating kettle, and carbonizing for 6 hours at 1150 ℃ in a roller kiln to obtain the phosphorus-boron modified carbon coated artificial graphite anode material.
The results of the tests of gram capacity, 2C/0.2C capacity retention and first time efficiency of the graphite anode materials obtained in examples 1 to 7 and comparative examples 1 to 3 are shown in Table 1.
Table 1 various indices of the graphite anode materials of the different examples and comparative examples
Through example 1 and comparative example 1 contrast, when carrying out cladding transformation artificial graphite negative pole material, use a large amount of pitch to carry out cladding to graphite, can effectively promote the multiplying power performance of negative pole material, but owing to used more pitch, pitch can form soft carbon gomphosis thing after pitch graphitization, and the gram capacity of negative pole material can reduce, carries out the cladding to coal-based graphite through pitch and carbon-based particle mixture in this application, has effectively improved the gram capacity of negative pole material.
Compared with comparative example 2, when the phosphorus-boron modified carbon coated artificial graphite negative electrode material is used, the application of the phosphorus-boron modified negative electrode material to a lithium ion battery can enable the coating of a subsequent high polymer to be more compact, alleviate the pole piece falling phenomenon caused by charging expansion of the material, improve the rate capability, but can lead to the reduction of gram capacity of the negative electrode material and the obvious reduction of high-temperature performance of the material.
By comparing example 1 with comparative example 3, when the coal raw material was not coated, both the gram capacity and the capacity retention rate of the prepared graphite negative electrode material were reduced.
By comparing example 1 with examples 2 to 5, when the mass ratio of the third matrix in the anode material, that is, the mass ratio of the coating layer is improved, the gram capacity and the capacity retention rate of the anode material can be improved, and the quick charge performance of the anode material can be improved. However, as the mass proportion of the matrix III is gradually reduced, the thickness of the coating layer is gradually reduced, and the specific surface area of the synthesized negative electrode material is increased and then reduced, so that the first efficiency of the battery of the coal-based graphite negative electrode material is also increased and then reduced.
By comparing example 1 with examples 6 to 7, when the mass ratio of carbon nanotubes in the carbon-based particles is raised, the first efficiency of the anode material can be raised, and the cycle life of the anode material can be improved, but the gram capacity and the capacity retention rate of the anode material can be reduced.
According to table 1, it can be seen that the gram capacity and the capacity retention rate of the graphite anode material obtained by adopting the technical scheme of the application are higher, the first matrix is still kept to be the coal-based graphite material through high-temperature carbonization, the coal-based graphite material has quick charging characteristics, asphalt in the third matrix is changed into soft carbon in the coating layer, the quick charging performance of the material can be further improved, resin in the third matrix is changed into hard carbon after carbonization, the quick charging performance of the material can be effectively improved, meanwhile, the gram capacity of the material can be improved, the carbon nano tube and graphene in the third matrix still keep the original structure after high-temperature carbonization, the connection strength between the asphalt and the graphene can be improved, the structural strength of the coating layer is further improved, the compaction density of the material is properly improved, and after the anode material is circulated for many times, the expansion proportion of the coating layer is reduced, and then the pole piece falling phenomenon caused when the material is charged and expanded is relieved.
By applying the technical scheme of the invention, the coating layer of the coal-based graphite anode material comprises a soft carbon structure formed by asphalt and a hard carbon structure formed by graphene and carbon nanotubes, so that the gram capacity and the quick charge performance of the anode material after coating can be ensured, meanwhile, the graphite anode material only needs to be coated once, the synthesis process is simple, after coating, the carbon nanotubes and the graphene in the matrix III still maintain the original structure, the pole piece falling phenomenon caused by charging and expanding the material can be effectively relieved, the compaction density of the material can be properly improved, and the problem that the anode material is expanded and falls after multiple cycles is solved.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments in accordance with the present application. As used herein, the singular is also intended to include the plural unless the context clearly indicates otherwise, and furthermore, it is to be understood that the terms "comprises" and/or "comprising" when used in this specification are taken to specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof.
The relative arrangement of the components and steps, numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless it is specifically stated otherwise. Meanwhile, it should be understood that the sizes of the respective parts shown in the drawings are not drawn in actual scale for convenience of description. Techniques, methods, and apparatus known to one of ordinary skill in the relevant art may not be discussed in detail, but should be considered part of the specification where appropriate. In all examples shown and discussed herein, any specific values should be construed as merely illustrative, and not a limitation. Thus, other examples of the exemplary embodiments may have different values. It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further discussion thereof is necessary in subsequent figures.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (15)
1. The preparation method of the coal-based graphite anode material is characterized by comprising the following steps of:
(1) Crushing and shaping a coal raw material, and then performing graphitization treatment to obtain a first matrix;
(2) Mixing asphalt with carbon-based particles to obtain a second matrix, wherein the carbon-based particles are graphene and/or carbon nanotubes;
(3) Mixing the second matrix with resin to obtain a third matrix;
(4) And mixing the first matrix with the third matrix, and then carrying out high-temperature carbonization, sieving and demagnetizing treatment to obtain the coal-based graphite anode material.
2. The production method according to claim 1, wherein in the step (1), graphitizing the pulverized and shaped coal raw material satisfies the following conditions:
the vitrinite reflectance of the crushed and shaped coal raw material is more than or equal to 1.5%, the volatile component is less than or equal to 15wt% and the ash content is less than or equal to 15wt%;
and/or the graphitization treatment temperature is 2800 ℃ to 3200 ℃, preferably 3000 ℃.
3. The method according to claim 1, wherein in step (1), the substrate obtained is required to satisfy the following conditions:
the graphitization degree of the first matrix is 80-95;
and/or the matrix-particle size D50 is between 5 and 20 μm;
and/or Lc is less than or equal to 30nm and less than or equal to 70nm, la is less than or equal to 50nm and less than or equal to 120nm.
4. The method according to claim 1, wherein in the step (1), the coal raw material is crushed by any one or more of roll mill, impact mill, rotary wheel mill, and air flow mill, and the crushed coal raw material is shaped by a horizontal shaper and/or a vertical shaper.
5. The method according to any one of claims 1 to 4, wherein in step (2), the asphalt is a high-temperature coated asphalt or a mesophase asphalt, and the asphalt is required to satisfy the following conditions:
the softening point of the bitumen is between 120 ℃ and 300 ℃, preferably 260 ℃;
and/or the coking value of the asphalt is more than or equal to 50%, preferably 56%;
and/or the ash content of the asphalt is less than or equal to 0.5wt%, preferably 0.3wt%;
and/or the quinoline insoluble content of the asphalt is less than or equal to 0.5wt percent, preferably 0.2wt percent.
6. The method according to any one of claims 1 to 4, wherein in step (2), the graphene is required to satisfy the following conditions:
the graphene content of the graphene with the number of 1-3 layers is more than or equal to 80wt%, preferably 85%;
and/or the diameter-to-thickness ratio of the graphene is greater than or equal to 300, preferably 500;
and/or the conductivity of the graphene is more than or equal to 0.5X10 5 s/m, preferably 1X 10 5 s/m。
7. The method according to any one of claims 1 to 4, wherein in the step (2), the carbon nanotubes are single-walled carbon nanotubes or multi-walled carbon nanotubes, and the following conditions are required for the carbon nanotubes:
the diameter of the carbon nanotubes is less than or equal to 20nm, preferably 10nm;
and/or the aspect ratio of the carbon nanotubes is greater than 100:1 and less than 1000:1, preferably 150:1;
and/or the conductivity of the carbon nano tube is greater than or equal to 0.1 multiplied by 10 5 s/m, preferably 0.5X10 5 s/m。
8. The method according to any one of claims 1 to 4, wherein in the step (2), the weight ratio of the matrix pitch, the graphene, and the carbon nanotubes is (1 to 0.95): 0 to 0.025; preferably, the carbon-based particles are a mixture of the graphene and the carbon nanotubes, and the weight ratio of the graphene to the carbon nanotubes is 1-1.2.
9. The method according to any one of claims 1 to 4, wherein in the step (3), the resin is one or more of a phenol resin, a urea resin, an epoxy resin, a urethane resin, a polyester resin and a polyacrylic resin, and preferably the ratio of the second substrate to the resin is (90 to 50): (10 to 50).
10. The method according to any one of claims 1 to 4, wherein in the step (3), the second substrate and the resin are mixed by one or more of VC, coulter, and ribbon.
11. The method according to any one of claims 1 to 4, wherein in the step (4), the mixing mode of the first substrate and the third substrate is one or more of VC mixing, coulter mixing or ribbon mixing, and the mixing ratio of the first substrate and the third substrate is (1 to 0.9): 0.02 to 0.1.
12. The method according to any one of claims 1 to 4, wherein in step (4), the high-temperature carbonization is required to satisfy the following conditions:
the high-temperature carbonization temperature is 950-1500 ℃, preferably 1100 ℃;
and/or the heating rate in the high-temperature carbonization process is 1-10 ℃/min, preferably 10 ℃/min;
and/or the high temperature carbonization time is 5 to 20 hours, preferably 10 hours.
13. A coal-based graphite anode material, characterized in that the coal-based graphite anode material is produced by the production method according to any one of claims 1 to 12.
14. The coal-based graphite anode material according to claim 13, wherein the coal-based graphite anode material comprises a substrate (10) and a coating layer (20), the coating layer (20) is coated on the outer surface of the substrate (10), the coating layer (20) is prepared from a substrate three, and the thickness of the coating layer (20) is 5-150 nm.
15. Use of a coal-based graphite anode material as claimed in claim 13 as an electrode material.
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