CN116022782B - Graphite negative electrode material, preparation method and application - Google Patents
Graphite negative electrode material, preparation method and application Download PDFInfo
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- CN116022782B CN116022782B CN202111245140.1A CN202111245140A CN116022782B CN 116022782 B CN116022782 B CN 116022782B CN 202111245140 A CN202111245140 A CN 202111245140A CN 116022782 B CN116022782 B CN 116022782B
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 136
- 229910002804 graphite Inorganic materials 0.000 title claims abstract description 113
- 239000010439 graphite Substances 0.000 title claims abstract description 113
- 238000002360 preparation method Methods 0.000 title claims abstract description 23
- 239000007773 negative electrode material Substances 0.000 title claims description 30
- 239000002245 particle Substances 0.000 claims abstract description 69
- 239000007790 solid phase Substances 0.000 claims abstract description 66
- 238000002156 mixing Methods 0.000 claims abstract description 65
- 239000010426 asphalt Substances 0.000 claims abstract description 30
- 239000000463 material Substances 0.000 claims abstract description 30
- 238000010008 shearing Methods 0.000 claims abstract description 28
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 19
- 230000009471 action Effects 0.000 claims abstract description 10
- 238000000034 method Methods 0.000 claims description 29
- 238000001125 extrusion Methods 0.000 claims description 14
- 238000003763 carbonization Methods 0.000 claims description 12
- 229910021382 natural graphite Inorganic materials 0.000 claims description 9
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 8
- 229910001416 lithium ion Inorganic materials 0.000 claims description 8
- 229910021383 artificial graphite Inorganic materials 0.000 claims description 6
- 239000011247 coating layer Substances 0.000 claims description 6
- 239000003208 petroleum Substances 0.000 claims description 6
- 239000003245 coal Substances 0.000 claims description 5
- 238000012545 processing Methods 0.000 claims description 4
- 239000007787 solid Substances 0.000 claims description 2
- 239000011248 coating agent Substances 0.000 abstract description 60
- 238000000576 coating method Methods 0.000 abstract description 38
- 239000010405 anode material Substances 0.000 abstract description 26
- 230000000694 effects Effects 0.000 abstract description 25
- 230000001976 improved effect Effects 0.000 abstract description 14
- 239000000203 mixture Substances 0.000 abstract description 8
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- 238000012986 modification Methods 0.000 description 5
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 4
- 239000003822 epoxy resin Substances 0.000 description 4
- 229910052744 lithium Inorganic materials 0.000 description 4
- 239000011295 pitch Substances 0.000 description 4
- 229920000647 polyepoxide Polymers 0.000 description 4
- 229910021384 soft carbon Inorganic materials 0.000 description 4
- 239000010406 cathode material Substances 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 238000012216 screening Methods 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 238000005054 agglomeration Methods 0.000 description 2
- 230000002776 aggregation Effects 0.000 description 2
- 239000007833 carbon precursor Substances 0.000 description 2
- 239000011300 coal pitch Substances 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 239000012467 final product Substances 0.000 description 2
- 239000007770 graphite material Substances 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 238000009830 intercalation Methods 0.000 description 2
- 230000002687 intercalation Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
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- 238000003860 storage Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 230000003313 weakening effect Effects 0.000 description 2
- KXGFMDJXCMQABM-UHFFFAOYSA-N 2-methoxy-6-methylphenol Chemical compound [CH]OC1=CC=CC([CH])=C1O KXGFMDJXCMQABM-UHFFFAOYSA-N 0.000 description 1
- DPXJVFZANSGRMM-UHFFFAOYSA-N acetic acid;2,3,4,5,6-pentahydroxyhexanal;sodium Chemical compound [Na].CC(O)=O.OCC(O)C(O)C(O)C(O)C=O DPXJVFZANSGRMM-UHFFFAOYSA-N 0.000 description 1
- 230000003213 activating effect Effects 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000001768 carboxy methyl cellulose Substances 0.000 description 1
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- 238000007796 conventional method Methods 0.000 description 1
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- 230000000977 initiatory effect Effects 0.000 description 1
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- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 1
- 238000005580 one pot reaction Methods 0.000 description 1
- 239000011301 petroleum pitch Substances 0.000 description 1
- 229920001568 phenolic resin Polymers 0.000 description 1
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- 239000002243 precursor Substances 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 238000004537 pulping Methods 0.000 description 1
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- 238000000197 pyrolysis Methods 0.000 description 1
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- 150000003384 small molecules Chemical class 0.000 description 1
- 235000019812 sodium carboxymethyl cellulose Nutrition 0.000 description 1
- 229920001027 sodium carboxymethylcellulose Polymers 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 229920003048 styrene butadiene rubber Polymers 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
Classifications
-
- 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 graphite anode material, a preparation method and application thereof. The preparation method comprises the steps of mixing graphite with solid-phase coated particles for the first time, then mixing the mixture for the second time under the action of shearing force, and carbonizing the mixture to obtain the graphite anode material, wherein the solid-phase coated particles are asphalt materials, and the softening point of the asphalt materials is 40-300 ℃. According to the invention, the device with a strong shearing effect is adopted, the relatively soft solid-phase coating agent particles and the graphite particles are rubbed and fully mixed, the surface thin layers of the solid-phase coating agent particles gradually fall off due to the strong shearing friction effect, and the graphite and the coating particles are well soaked and adhered to the surface of the graphite, so that the coating effect of the solid-phase coating agent on the graphite is greatly improved, the carbon layer is compactly and uniformly coated, the first effect and the multiplying power performance of the graphite anode material are further improved, and meanwhile, the quick charging performance of the graphite anode material is also improved.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and relates to a graphite anode material, a preparation method and application thereof.
Background
In the 80 th century, the concept of rocking chair batteries suggests that a carbon negative electrode lithium ion battery starts to sprout later, graphite is different from a low-temperature carbonized negative electrode material, and the graphite negative electrode material has fewer hetero atoms and defects after high-temperature treatment, so that the coulomb efficiency is over 90 percent, and the higher graphitization degree is added, so that the lithium storage mechanism of the graphite negative electrode is intercalation, the discharge platform is wide, and the product use is facilitated. The theoretical capacity of the natural graphite and artificial graphite anode materials is 372mAh/g, and the capacity of the currently commercially available excellent graphite anode materials can reach 365mAh/g, so that the graphite becomes an anode material with excellent performance in a lithium battery.
However, the graphite negative electrode material using intercalation as the main lithium storage mechanism has poor rate performance because the lithium ion deintercalation of the graphite negative electrode material can only be along the direction of a graphite sheet layer, and the rate of the graphite negative electrode material in a button cell is generally not more than 3 ℃. In contrast, coating agent is used to carry out coating modification on the surface of graphite, so that an isotropic thin carbon layer is constructed, the way of lithium ions entering the graphite is increased, and the method becomes a modification means of graphite negative electrode materials which are mainstream in the market.
In industrial production, solid phase coating with simple process and extremely high production efficiency is the most common coating means, but the conventional solid phase coated product has poor uniformity and general coating effect, and the produced product has poor performance stability.
CN102255076a discloses a graphite material with a carbon layer coated on the surface, a preparation method and application as a negative electrode material of a lithium ion battery. The method comprises the steps of A, fully and uniformly mixing a carbon source serving as a coating and graphite powder in a mass ratio of 10:100, wherein the carbon source serving as the coating is phenolic resin crushed powder and petroleum asphalt powder in a mass ratio of 1:1, the graphite powder is natural graphite powder subjected to spherical treatment, the temperature of the mixture is controlled to be increased to 120 ℃, stirring is maintained for 3 hours at the temperature, B, the product of the step A is fully carbonized for 12 hours under the condition of 1100 ℃ under the protection of argon, the obtained product is crushed and graded, the product with the granularity D50 of 20 microns is sieved, and C, the product of the step B is graphitized for 72 hours under the condition of 2400 ℃. In the conventional method for coating graphite by solid-phase carbon in the document, the condition that the uniformity of a coated product is poor, the coating effect is general, and the performance stability of the produced product is poor can occur.
CN103647055A discloses a negative electrode material of epoxy resin modified graphite and a preparation method thereof, by grinding, high-temperature curing, carbonizing and crushing the organosilicon modified epoxy resin and the natural graphite, the material of the epoxy resin modified natural graphite is obtained, although the co-embedding of large-volume solvent molecules can be prevented, the co-embedding is easy to agglomerate by high-temperature pyrolysis, the coating effect can be damaged by crushing, the phenomenon that the coating on the surface of the graphite is uneven and the coating layer is damaged can not be realized finally.
Therefore, how to uniformly and densely coat the carbon layer on the surface of the graphite material, so as to improve the electrochemical performance of the graphite negative electrode material is a technical problem to be solved.
Disclosure of Invention
Aiming at the defects existing in the prior art, the invention aims to provide a graphite anode material, a preparation method and application thereof. According to the invention, the device with a strong shearing effect is adopted, the relatively soft solid-phase coating agent particles and the graphite particles are rubbed and fully mixed, the surface thin layers of the solid-phase coating agent particles gradually fall off due to the strong shearing friction effect, and the graphite and the coating particles are well soaked and adhered to the surface of the graphite, so that the coating effect of the solid-phase coating agent on the graphite is greatly improved, the carbon layer is compactly and uniformly coated, the first effect and the multiplying power performance of the graphite anode material are further improved, and meanwhile, the quick charging performance of the graphite anode material is also obviously improved.
To achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a method for preparing a graphite anode material, the method comprising:
mixing graphite with solid phase coated particles for the first time, then mixing the graphite with the solid phase coated particles for the second time under the action of shearing force, and carbonizing to obtain the graphite anode material;
The solid phase coating particles are made of a material with a softening point of 40-300 ℃, for example, the softening point can be 40 ℃, 50 ℃, 100 ℃, 150 ℃, 200 ℃, 250 or 300 ℃.
The invention adopts the equipment with strong shearing action, the relative soft solid phase coating agent particles and the graphite particles are rubbed and fully mixed, the surface thin layer of the solid phase coating particles gradually drops off due to the strong shearing friction action, and the graphite and the coating particles are adhered on the surface of the graphite due to good wettability, so that the coating effect of the solid phase coating agent on the graphite is greatly improved, the carbon layer is compactly and uniformly coated, the first effect and the multiplying power performance of the graphite cathode material are further improved, and the preparation method provided by the invention can realize continuous production, and has higher production efficiency compared with the traditional one-pot solid phase coating process.
According to the invention, solid-phase coated particles with the softening point of 40-300 ℃ are selected, and the effect of strong shearing force is used, so that the solid-phase coated particles can be better stripped and attached to the surface of graphite, the softening point is more than or equal to 40 ℃ so as not to be molten into a liquid state in the processing process, if the softening point is less than 40 ℃, the solid-phase coated particles are softened due to friction heating, so that graphite agglomeration is caused, uniform dispersion of the solid-phase coated particles is not facilitated, and too high load is brought to a device driving motor, the softening point of the solid-phase coated particles is required to be further less than or equal to 300 ℃, so that the wettability of soft carbon precursors and graphite is weakened due to too few small molecular substances in the components, and the viscosity of a coating agent is high due to less small molecules in the carbonization process, and the coating agent is difficult to be paved on the surface of graphite.
In the invention, if only primary mixing is performed and secondary mixing is not performed, the solid-phase coated particles and the graphite are only in a simple mixing state, so that the solid-phase coated particles cannot uniformly coat the graphite even when being softened in the subsequent carbonization process, and if only secondary mixing is performed and primary mixing is not performed, the solid-phase coated particles are difficult to uniformly disperse in the graphite, so that the final product is a mutual blend of soft carbon and the graphite.
The preparation method provided by the invention has the preparation environment that the temperature is not higher than 40 ℃ and the humidity is less than 75%, and under the environment, the solid-phase coating agent can well maintain the appearance of the solid-phase coating agent. And when the temperature is higher, the solid phase coating agent is easy to be sticky and agglomerate, which is unfavorable for the preparation of the final product.
Preferably, the preparation method of the graphite anode material is carried out under a protective atmosphere or under a hot air condition.
Preferably, the solid phase coated particles are pitch materials.
Compared with other coating materials such as epoxy resin, the asphalt material has the advantages of simple raw material crushing, high carbon forming rate and regular carbide carbon layer, and the asphalt material is in a solid state in the processing process, so that the softening point of the asphalt material is more than or equal to 40 ℃ to avoid melting into a liquid state in the processing process, and if the softening point is less than 40 ℃, the solid phase coating particles are softened due to friction heating, so that graphite agglomeration is caused, uniform dispersion of the solid phase coating particles is not facilitated, and too high load is brought to a device driving motor, and the softening point of the asphalt material is required to be more than or equal to 300 ℃ to avoid weakening the wettability of a soft carbon precursor and graphite due to less small molecular substances, so that the viscosity of the coating agent is higher in the carbonization process, and the coating agent is difficult to be tiled on the surface of the graphite.
Preferably, the softening point of the solid phase coated particles is 50 to 150 ℃, for example 50 ℃, 60 ℃, 70 ℃, 80 ℃, 90 ℃, 100 ℃, 110 ℃, 120 ℃, 130 ℃, 140 ℃, 150 ℃ or the like.
Preferably, the solid phase coated particles have a median particle diameter of 2 to 10 μm, for example, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm, etc.
Preferably, the graphite comprises artificial graphite and/or natural graphite.
Preferably, the asphalt material comprises any one or a combination of at least two of petroleum asphalt, coal asphalt or synthetic asphalt.
Preferably, the mass ratio of the solid phase coated particles to the graphite is (5-20): (95-80), such as 5:95, 10:90, 15:85 or 20:80.
Preferably, the time of the primary mixing is 5-30 min, for example, 5min, 10min, 15min, 20min, 25min or 30min, etc.
In the invention, the uniform dispersion of the solid phase of the material can be better realized within the primary mixing time range.
Preferably, the primary mixing is performed by a mixing device.
In the present invention, the mixing apparatus includes, but is not limited to, a homogenizing dispersing barrel, a high-speed mixer, a gravity-free mixer, a V-type mixer, a VC high-efficiency mixer, or the like.
Preferably, the mixing frequency of the mixing device is 20-50 Hz, such as 20Hz, 25Hz, 30Hz, 35Hz, 40Hz, 45Hz or 50Hz, etc.
Preferably, the means for secondary mixing by the action of shear force comprises any one or a combination of at least two of high-speed stirring, kneading or screw extrusion, preferably screw extrusion.
In the invention, the shearing force effect is realized in a screw extrusion mode, so that the solid phase coated particles are more favorable for cohesive failure caused by strong shearing force, and are continuously stripped.
Preferably, the screw extrusion is performed by a mixing device with a screw.
Preferably, the rotation speed of the mixing device with the screw is 60-300 rpm, for example 60rpm, 80rpm, 100rpm, 130rpm, 150rpm, 180rpm, 200rpm, 230rpm, 250rpm, 280rpm or 300rpm, etc.
In the invention, if the rotating speed of the mixing equipment with the screw is too small, the shearing force applied to the solid-phase coated particles is small, the solid-phase coated particles cannot be effectively damaged, so that the coating is uneven, and if the rotating speed is too large, the service life of the equipment is influenced, the temperature in the mixing process is too high due to the too high rotating speed, the solid-phase coated particles are softened into a liquid state due to the too high temperature, graphite is agglomerated, the screw torque is increased rapidly, and the equipment is easy to damage.
Preferably, the mixing equipment with the screw comprises a feeding end, a compacting section, a shearing section and a discharging end in sequence.
The invention has the advantages that the thread interval of the feeding end is wider to ensure that materials can smoothly enter the equipment cavity, the thread interval of the compacting section is gradually shortened to ensure that the materials are tightly compacted, the shearing section is a stage of the mixing equipment which plays a main role of strong shearing and friction, the friction force between solid phase coated particles and graphite particles is gradually increased under the action of strong shearing friction, the surface layer and the inner layer of the soft solid phase coating agent are continuously peeled off and fall off due to larger shearing force, and the components of the solid phase coating agent are oleophilic and have good infiltration performance with graphite, so that the solid phase coating agent can be well attached to the uneven graphite surface to achieve the effect of uniformly coating the graphite surface, and the fourth section is the discharging end, wherein the screw interval of the section is gradually widened, so that the materials become fluffy under the external force of continuous stirring, and the materials are conveniently discharged.
Preferably, the thread pitch of the feed end is smaller than the thread pitch of the compaction section.
Preferably, the carbonization temperature is 900-1200 ℃, such as 900 ℃, 1000 ℃, 1100 ℃, 1200 ℃, or the like.
Preferably, the carbonization time is 5-10 h, for example 5h, 6h, 7h, 8h, 9h or 10h, etc.
Preferably, after carbonization, depolymerizing and sieving are sequentially performed on the carbonized product, and the sieving equipment is one or more of an ultrasonic vibration sieve, a swinging sieve and a rotary vibration sieve, and the filter screen is selected to be 200-500 meshes, for example, 200-300 meshes, 400 meshes or 500 meshes, and the like.
As a preferred technical scheme, the preparation method comprises the following steps:
Mixing graphite and solid-phase coated particles for 5-30 min by mixing equipment at the mixing frequency of 20-50 Hz in a mass ratio of (95-80), then performing secondary mixing by a shearing force effect by a mixing equipment with a screw in a screw extrusion mode at the rotating speed of 60-300 rpm, and carbonizing for 5-10 h at 900-1200 ℃ to obtain the graphite anode material;
The solid phase coating particles are asphalt materials, the asphalt materials comprise any one or a combination of at least two of petroleum asphalt, coal asphalt and artificial asphalt, and the softening point of the asphalt materials is 50-150 ℃.
In a second aspect, the invention provides a graphite anode material, which is prepared by the preparation method of the graphite anode material in the first aspect, wherein the graphite anode material is formed by coating a carbon coating layer on the surface of graphite.
In a third aspect, the present invention also provides a lithium ion battery comprising a graphite anode material as described in the second aspect.
Compared with the prior art, the invention has the following beneficial effects:
according to the invention, equipment with a strong shearing effect is adopted, relatively soft solid-phase coating agent particles and graphite particles are rubbed and fully mixed, the surface thin layers of the solid-phase coating agent particles gradually fall off due to the strong shearing friction effect, and the graphite and the coating particles are well infiltrated and adhered to the surface of the graphite, so that the coating effect of the solid-phase coating agent on the graphite is greatly improved, the carbon layer is compactly and uniformly coated, the first effect and the rate capability of the graphite cathode material are further improved, meanwhile, the quick charge performance of the battery is obviously improved, the first effect of the battery is more than 87.32%, the quick charge performance of the battery of 2C/0.2C is more than 29%, and the rotating speed of screw extrusion is further adjusted, so that the quick charge performance of the battery of 2C/0.2C can reach more than 31% in a preferred range.
Detailed Description
The technical scheme of the invention is further described by the following specific examples. It will be apparent to those skilled in the art that the examples are merely to aid in understanding the invention and are not to be construed as a specific limitation thereof.
Example 1
The embodiment provides a preparation method of a graphite anode material, which comprises the following steps:
Mixing artificial graphite (median particle diameter of 16 μm) with petroleum pitch (softening point of 50 ℃ C., median particle diameter of 5 μm) at a mass ratio of 95:5 in a V-type mixer at a mixing frequency of 30Hz for 25min;
Then, carrying out secondary mixing by a mixing device with a pair of screws in a screw extrusion mode at a rotating speed of 60rpm, feeding the mixture after primary mixing into a device cavity at a feeding end of the mixing device with the pair of screws, compacting materials sequentially through a compacting section, then realizing coating of petroleum asphalt on artificial graphite in a shearing section, discharging the materials through a discharging end, carbonizing for 10 hours at a carbonization temperature of 1000 ℃, depolymerizing carbonized products, and screening by a screen mesh of 200 meshes to obtain the graphite anode material with the carbon coating layer coated on the surface.
Example 2
Mixing natural graphite (median particle diameter of 12 μm) with coal pitch (softening point of 150 ℃ C., median particle diameter of 9 μm) at a mass ratio of 80:20 in a homogenizing dispersion barrel at a mixing frequency of 50Hz for 10min;
then, carrying out secondary mixing by a mixing device with a pair of screws in a screw extrusion mode at a rotating speed of 300rpm, feeding the mixture after primary mixing into a device cavity at a feeding end of the mixing device with the pair of screws, compacting materials sequentially through a compacting section, then realizing the coating of coal tar pitch on natural graphite in a shearing section, discharging the materials through a discharging end, carbonizing for 5 hours at a carbonization temperature of 1200 ℃, depolymerizing carbonized products, and screening by a 500-mesh screen to obtain the graphite anode material with the carbon coating layer coated on the surface.
Example 3
Mixing artificial graphite (median particle diameter of 15 μm) with artificial pitch (softening point of 210 ℃ C., median particle diameter of 5 μm) at a mass ratio of 90:10 in a homogenizing dispersion barrel at a mixing frequency of 20Hz for 30min;
Then, carrying out secondary mixing by a mixing device with a pair of screws in a screw extrusion mode at a rotating speed of 180rpm, feeding the mixture after primary mixing into a device cavity at a feeding end of the mixing device with the pair of screws, compacting materials sequentially through a compacting section, then realizing the coating of coal asphalt on natural graphite in a shearing section, discharging the materials through a discharging end, carbonizing for 6 hours at a carbonization temperature of 900 ℃, depolymerizing carbonized products, and screening by a 300-mesh screen to obtain the graphite anode material with the carbon coating layer coated on the surface.
Example 4
The difference between this example and example 1 is that in this example, the rotational speed during screw extrusion was 500rpm.
The remaining preparation methods and parameters were consistent with example 1.
Comparative example 1
The difference between this comparative example and example 1 is that coal pitch, which has a softening point of 350℃and a median particle diameter of 5. Mu.m, is used in this comparative example.
The remaining preparation methods and parameters were consistent with example 1.
Comparative example 2
The difference between this comparative example and example 1 is that only one mixing was performed in this comparative example, i.e., the solid phase coated particles were mixed with graphite using a VC high efficiency mixer at a frequency of 40Hz for 30min without secondary mixing.
The remaining preparation methods and parameters were consistent with example 1.
Comparative example 3
The difference between this comparative example and example 1 is that in this comparative example, only secondary mixing was performed and primary mixing was not performed.
The remaining preparation methods and parameters were consistent with example 1.
(1) Preparing a test sample, namely preparing a graphite anode material provided in examples 1-4 and comparative examples 1-3, styrene-butadiene rubber, sodium carboxymethyl cellulose and conductive carbon black in a ratio of 94.5:2.5:1.5:1.5 to obtain an anode pole piece, wherein the anode material is a lithium piece, and then performing pulping, coating, pole piece baking, pole piece rolling, pole piece punching, pole piece weighing, assembling and activating to obtain a button cell for testing, and performing electrochemical performance testing;
(2) And (3) testing the first charge and discharge reversible capacity, namely testing the first charge and discharge performance of the button cell under the 0.02C multiplying power by using a arbin blue electric tester.
(3) First coulombic efficiency the ratio of the first discharge capacity to the first charge capacity was calculated from the test results in (2).
(4) Quick charge performance of 2C/0.2C after cycling the button cell for 2 weeks by using arbin blue tester, discharge performance under 0.2C and 2C multiplying power is tested successively, and the ratio of the latter to the former is calculated.
The results are shown in Table 1.
TABLE 1
From the data results of examples 1 and 4, it is known that the too high rotation speed in the secondary mixing process can cause the reduction of the feeding speed due to the prevention of the locking of the screw in the modification process, and finally the equipment cavity cannot be effectively filled, thereby reducing the shearing action of the solid phase coated particles and the graphite and weakening the coating effect.
From the data of example 1 and comparative example 1, it is apparent that the solid-phase coated particles have too high a softening point, which is disadvantageous in that the solid-phase coated particles are peeled off by a shearing force and effectively adhere to the graphite surface, and that the solid-phase coated particles have a large viscosity during the temperature rising process during carbonization, and have general spreadability, resulting in poor coating effect.
From the data provided in example 1 and comparative example 2, it is understood that the graphite anode material obtained by the preparation method provided by the invention has more excellent 2C/0.2C fast charge performance than the conventional solid phase coating method.
From the data of example 1 and comparative example 3, it is clear that in the present invention, only secondary mixing is performed, and there is a phenomenon that the carbonized precursor is unevenly mixed, which finally results in a carbonized product that is a simple blended product of soft carbon and graphite, and its initial effect and 2C/0.2C fast charge performance are low.
In summary, the invention adopts the equipment with strong shearing action to rub and fully mix the relatively soft solid phase coating agent particles and the graphite particles, the solid phase coating particles gradually fall off due to the strong shearing friction action, and the graphite and the coating particles are adhered on the surface of the graphite due to good wettability, so that the coating effect of the solid phase coating agent on the graphite is greatly improved, the carbon layer is compactly and uniformly coated, the initial efficiency and the multiplying power performance of the graphite cathode material are further improved, meanwhile, the quick charge performance of the battery is obviously improved, the initial efficiency of the battery is more than 87.32%, the quick charge performance of the battery of 2C/0.2C is more than 29%, and the rotating speed of screw extrusion is further adjusted, so that the quick charge performance of the battery of 2C/0.2C can be more than 31% within a preferred range.
While the foregoing is directed to embodiments of the present invention, other and further details of the invention may be had by the present invention, it should be understood that the foregoing description is merely illustrative of the present invention and that no limitations are intended to the scope of the invention, except insofar as modifications, equivalents, improvements or modifications are within the spirit and principles of the invention.
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