CN114156471A - Graphite negative electrode material and preparation method and application thereof - Google Patents
Graphite negative electrode material and preparation method and application thereof Download PDFInfo
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 103
- 229910002804 graphite Inorganic materials 0.000 title claims abstract description 101
- 239000010439 graphite Substances 0.000 title claims abstract description 101
- 238000002360 preparation method Methods 0.000 title claims abstract description 35
- 239000007773 negative electrode material Substances 0.000 title claims description 38
- 229910021382 natural graphite Inorganic materials 0.000 claims abstract description 73
- 238000000034 method Methods 0.000 claims abstract description 49
- 239000011230 binding agent Substances 0.000 claims abstract description 46
- 239000003054 catalyst Substances 0.000 claims abstract description 43
- 229910021383 artificial graphite Inorganic materials 0.000 claims abstract description 35
- 239000010406 cathode material Substances 0.000 claims abstract description 34
- 239000011248 coating agent Substances 0.000 claims abstract description 28
- 238000000576 coating method Methods 0.000 claims abstract description 28
- 239000011268 mixed slurry Substances 0.000 claims abstract description 24
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims abstract description 17
- 229910001416 lithium ion Inorganic materials 0.000 claims abstract description 17
- 239000000463 material Substances 0.000 claims abstract description 16
- 238000005087 graphitization Methods 0.000 claims abstract description 14
- 238000002156 mixing Methods 0.000 claims abstract description 12
- 239000002904 solvent Substances 0.000 claims abstract description 7
- 238000001694 spray drying Methods 0.000 claims abstract description 7
- 238000012216 screening Methods 0.000 claims abstract description 6
- 230000008569 process Effects 0.000 claims description 22
- 239000000203 mixture Substances 0.000 claims description 12
- 239000007787 solid Substances 0.000 claims description 11
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- 239000010405 anode material Substances 0.000 claims description 9
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- 238000007493 shaping process Methods 0.000 claims description 8
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 6
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 claims description 6
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 4
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 4
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 claims description 4
- 239000002105 nanoparticle Substances 0.000 claims description 4
- VZGDMQKNWNREIO-UHFFFAOYSA-N tetrachloromethane Chemical compound ClC(Cl)(Cl)Cl VZGDMQKNWNREIO-UHFFFAOYSA-N 0.000 claims description 4
- 238000004519 manufacturing process Methods 0.000 claims description 3
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 claims description 2
- CTQNGGLPUBDAKN-UHFFFAOYSA-N O-Xylene Chemical compound CC1=CC=CC=C1C CTQNGGLPUBDAKN-UHFFFAOYSA-N 0.000 claims description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 2
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 claims description 2
- 229910052796 boron Inorganic materials 0.000 claims description 2
- 239000003245 coal Substances 0.000 claims description 2
- 239000011280 coal tar Substances 0.000 claims description 2
- 239000000295 fuel oil Substances 0.000 claims description 2
- 229910052742 iron Inorganic materials 0.000 claims description 2
- 239000003208 petroleum Substances 0.000 claims description 2
- 238000004321 preservation Methods 0.000 claims description 2
- 229910052710 silicon Inorganic materials 0.000 claims description 2
- 239000010703 silicon Substances 0.000 claims description 2
- 239000011135 tin Substances 0.000 claims description 2
- 229910052718 tin Inorganic materials 0.000 claims description 2
- 239000008096 xylene Substances 0.000 claims description 2
- 239000003792 electrolyte Substances 0.000 abstract description 11
- 230000002035 prolonged effect Effects 0.000 abstract description 2
- 239000010410 layer Substances 0.000 description 23
- 239000007770 graphite material Substances 0.000 description 11
- 230000001070 adhesive effect Effects 0.000 description 9
- 238000010438 heat treatment Methods 0.000 description 9
- 239000000853 adhesive Substances 0.000 description 7
- 239000002994 raw material Substances 0.000 description 7
- 238000005253 cladding Methods 0.000 description 6
- 230000007547 defect Effects 0.000 description 6
- 230000014759 maintenance of location Effects 0.000 description 6
- 239000003607 modifier Substances 0.000 description 6
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 5
- 239000011300 coal pitch Substances 0.000 description 5
- 239000002131 composite material Substances 0.000 description 5
- 229910052744 lithium Inorganic materials 0.000 description 5
- 229910021384 soft carbon Inorganic materials 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 4
- 238000007086 side reaction Methods 0.000 description 4
- 239000011247 coating layer Substances 0.000 description 3
- 238000007599 discharging Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 230000006872 improvement Effects 0.000 description 3
- 239000003960 organic solvent Substances 0.000 description 3
- 238000009829 pitch coating Methods 0.000 description 3
- 239000011148 porous material Substances 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- 239000004698 Polyethylene Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 239000006258 conductive agent Substances 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 239000011889 copper foil Substances 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 239000011888 foil Substances 0.000 description 2
- 238000005470 impregnation Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- -1 polyethylene Polymers 0.000 description 2
- 229920000573 polyethylene Polymers 0.000 description 2
- QQONPFPTGQHPMA-UHFFFAOYSA-N propylene Natural products CC=C QQONPFPTGQHPMA-UHFFFAOYSA-N 0.000 description 2
- 125000004805 propylene group Chemical group [H]C([H])([H])C([H])([*:1])C([H])([H])[*:2] 0.000 description 2
- 238000001878 scanning electron micrograph Methods 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- 229910012820 LiCoO Inorganic materials 0.000 description 1
- 229910001290 LiPF6 Inorganic materials 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 239000012298 atmosphere Substances 0.000 description 1
- 239000003575 carbonaceous material Substances 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 239000011294 coal tar pitch Substances 0.000 description 1
- 239000011258 core-shell material Substances 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000009831 deintercalation Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000007598 dipping method Methods 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 238000001513 hot isostatic pressing Methods 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 238000009830 intercalation Methods 0.000 description 1
- 230000002687 intercalation Effects 0.000 description 1
- 238000011031 large-scale manufacturing process Methods 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000012982 microporous membrane Substances 0.000 description 1
- 239000011295 pitch Substances 0.000 description 1
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 1
- 239000007774 positive electrode material Substances 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/20—Graphite
- C01B32/205—Preparation
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/20—Graphite
- C01B32/21—After-treatment
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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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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- Engineering & Computer Science (AREA)
- Geology (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Materials Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Battery Electrode And Active Subsutance (AREA)
- Carbon And Carbon Compounds (AREA)
Abstract
The invention discloses a graphite cathode material and a preparation method and application thereof, wherein the graphite cathode material is prepared by the following method: mixing the flake graphite, a catalyst, a binder and a solvent to prepare mixed slurry, carrying out spray drying on the obtained mixed slurry, mixing the obtained binder and the catalyst, coating the material on the surface of the flake graphite with the mixed binder and the catalyst, carrying out crushing and spheroidizing, carrying out graphitization on the obtained spherical natural graphite with the inner and outer surfaces coated with the binder and the catalyst, and carrying out magnetic screening to obtain the graphite cathode material. According to the invention, the prepared graphite cathode material comprises spherical natural graphite, the inner surface and the outer surface of the graphite cathode material are uniformly coated with the artificial graphite layer, so that the contact between electrolyte and the natural graphite can be effectively prevented, the cycle performance of the material is improved, the graphitization degree is high, the graphite cathode material has the advantages of high capacity, good cycle performance and the like, a working electrode can be prepared to be used for preparing a lithium ion battery, the cycle life of the lithium ion battery can be obviously prolonged, and the graphite cathode material has very high use value and good application prospect.
Description
Technical Field
The invention belongs to the field of negative electrode materials, and relates to a graphite negative electrode material, and a preparation method and application thereof.
Background
The carbon material has the advantages of high capacity, good reversibility of lithium intercalation/deintercalation, low potential platform, excellent cycle performance and the like, is a main cathode material of 3C electronic products, is widely applied, and is gradually expanded to be a power supply for Electric Vehicles (EV) and Hybrid Electric Vehicles (HEV). Therefore, the development and application of high-performance electrode materials are crucial. At present, graphite materials are mainly used as negative electrode materials of lithium ion batteries, and the traditional graphite negative electrode materials have the problems of poor cycle performance, poor rate performance and the like in the cycle process.
Natural graphite is widely used because of its high charge-discharge capacity, good charge-discharge plateau, wide sources and low cost. However, natural graphite has the problems of unstable structure, high internal pore, easy solvent molecule co-insertion and the like, so that the problem of ply shedding and cracking of the natural graphite is easy to occur in the charging and discharging processes, more surface area capable of reacting with electrolyte is exposed, the reaction with the electrolyte is accelerated, and finally the defects of reduced charging and discharging efficiency, poor cycle performance, poor safety and the like of the battery are caused, and the cycle life of the lithium ion battery is directly shortened. In order to overcome the above disadvantages of natural graphite, a layer of soft carbon is usually coated on the surface of natural graphite or artificial graphite is formed by graphitizing the soft carbon. However, the existing preparation method is difficult to realize the complete coating of the artificial graphite on the natural graphite, and as a result, the method has the following advantages: in the battery circulation process, effective coating cannot be realized, so that the natural graphite negative electrode material and the electrolyte can generate side reaction, and the circulation performance of the battery is poor. Based on this, the person skilled in the art has proposed a strategy by increasing the amount of soft carbon or artificial graphite coating, however, the actual use cases are: the method for improving the coating amount of the soft carbon or the artificial graphite can prevent the natural graphite from reacting with the electrolyte to a certain extent, but inevitably reduces the capacity of the natural graphite, so that the energy density of the material cannot meet the use requirement. In addition, in the existing preparation method of the graphite negative electrode material, for example: (1) chinese patent publication No. CN 103241731B discloses a method for preparing a composite graphite material for a secondary lithium ion battery, which comprises the following steps: putting natural graphite, a binder and a graphite catalyst which are used as raw materials into a roller furnace, and keeping a roller in a rotating state during the raw material putting process; the binder is a material capable of forming artificial graphite after graphitization, natural graphite is coated by stirring the binder, and the core-shell structure graphite is bonded after coating; heating the raw materials in the furnace by adopting a gradual heating temperature rise mode, wherein the roller furnace keeps rotating in the heating process; after the raw materials in the furnace are heated, naturally cooling to normal temperature; carrying out graphitization treatment on the raw material; after the treatment, the binder is treated to form the artificial graphite, and the artificial graphite coats the natural graphite particles. In the patent technology, the defects are as follows: the inside of natural graphite can't be filled to the binder in mixing process, leads to the graphitization in-process can't form artificial graphite coating in natural graphite is inside, therefore in battery cycle process, owing to can't realize the effective cladding to natural graphite is inside for natural graphite cathode material can take place the side reaction with electrolyte, leads to the cyclicity of battery to worsen. (2) Chinese patent publication No. CN 107814382 a discloses a long-life modified natural graphite negative electrode material, and a preparation method and use thereof, wherein the preparation method comprises the following steps: mixing natural graphite and asphalt particles, putting the mixture into a hot isostatic pressing machine, dipping the mixture under the conditions of high temperature and high pressure, washing the obtained material with an organic solvent, and further performing graphitization treatment to obtain the modified natural graphite cathode material. In the patent technology, the defects are as follows: the impregnation of the asphalt is realized under the conditions of high temperature and high pressure, and the defects of complex preparation process, high energy consumption, high production cost and the like exist; simultaneously, because the pitch coating on organic solvent drip washing surface has been adopted in the preparation process, this makes the pitch layer of surface cladding washed easily, lead to natural graphite surface pitch coating thin even no pitch coating, and then make artificial graphite layer be difficult to effective cladding on the natural graphite surface, it is same, the inside hole of natural graphite of adoption has the obturator or the hole is too little, also can make the cladding effect of natural graphite internal surface artificial graphite relatively poor, be difficult to realize the effective cladding of artificial graphite layer to the natural graphite internal surface, therefore in battery circulation process, owing to fail to realize the effective cladding to the internal and external surface of natural graphite, make natural graphite cathode material can take place the side reaction with electrolyte, lead to the circulation performance variation of battery. (3) Chinese patent publication No. CN 108832091 a discloses a long-cycle modified graphite-based composite material, a preparation method thereof, and a lithium ion battery comprising the material, wherein the preparation method comprises the following steps: mixing a graphite material and a coating modifier; loading the mixture into a self-pressurization reaction device, transferring the mixture into heating equipment to perform a self-pressurization impregnation experiment, controlling the rising temperature, gradually liquefying the coated modifier after the coated modifier reaches a softening point, and fully impregnating the graphite material under the action of self-pressurization force and distributing the impregnated graphite material on the surface of the graphite material; the coating modifier distributed on the surface of the graphite material can be re-solidified on the surface of the graphite material in the cooling process; and carrying out heat treatment under an inert atmosphere to obtain the modified graphite-based composite material. In the patent technology, the defects are as follows: the obtained natural graphite cathode material has poor cycle performance, and the reason may be that firstly, because closed pores or pores exist in the natural graphite and are too small, effective filling of the coating modifier in the natural graphite is difficult to realize by a self-pressurization method, so that the inner surface of the natural graphite is difficult to be uniformly coated by the coating modifier, the coating effect of the artificial graphite layer on the inner surface of the natural graphite is poor, the possibility that the inner surface of the natural graphite is exposed is high, secondly, after heat treatment, the material is crushed and graded, and the operation is easy to cause the falling of a soft carbon coating layer, so that the natural graphite is exposed; meanwhile, the method requires high-temperature and high-pressure equipment, which is not beneficial to industrialization. Therefore, how to obtain the graphite cathode material with high capacity and good cycle performance has very important significance for prolonging the cycle life of the lithium ion battery.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a graphite cathode material with high capacity and good cycle performance as well as a preparation method and application thereof.
In order to solve the technical problems, the invention adopts the technical scheme that:
a preparation method of a graphite negative electrode material comprises the following steps:
s1, mixing the flake graphite, the catalyst, the binder and the solvent to prepare mixed slurry;
s2, spray drying the mixed slurry obtained in the step S1 to obtain a material in which a binder and a catalyst are mixed and coated on the surface of the flake graphite;
s3, mixing the binder and the catalyst obtained in the step S2 and coating the mixture on the material on the surface of the flake graphite, and crushing and spheroidizing the mixture to obtain spherical natural graphite with the inner surface and the outer surface both coated with the binder and the catalyst;
and S4, graphitizing the spherical natural graphite with the inner and outer surfaces coated with the binder and the catalyst obtained in the step S3, and performing magnetic screening to obtain the graphite cathode material.
In the preparation method, the solid content of the mixed slurry is 5-20% in step S1.
In the step S1, the mass ratio of the crystalline flake graphite, the catalyst and the binder in the mixed slurry is 60-94: 1-10: 5-30.
In the preparation method, the average particle size of the flake graphite is 3-45 μm; the catalyst is one or more of carbide or oxide of silicon, iron, tin or boron; the average particle size of the catalyst is 1-5 mu m; the binder is one or more of petroleum asphalt, coal asphalt, mesophase asphalt, coal tar or heavy oil.
In a further improvement of the above preparation method, in step S1, the solvent is one or more of acetone, diethyl ether, xylene, carbon tetrachloride, n-hexane or ethanol.
In a further improvement of the above preparation method, in step S3, the spheroidization is performed in a continuous shaping system formed by connecting 2 to 15 micro-nano particle shaping and coating systems in series; the spheroidizing process parameters are as follows: the feeding amount is 50 kg-200 kg/h, the rotating speed is 100 rpm-9000 rpm, and the time is 5 min-45 min.
In a further improvement of the above preparation method, in step S4, the graphitization is performed at a temperature of 2800 to 3200 ℃; the heat preservation time in the graphitization process is 4-20 h.
As a general technical concept, the present invention also provides a graphite negative electrode material prepared by the above preparation method.
In the graphite negative electrode material, the graphite negative electrode material comprises spherical natural graphite; the inner surface and the outer surface of the spherical natural graphite are coated with artificial graphite layers, so that an inner coating structure and an outer coating structure which are the artificial graphite layers, the natural graphite layers and the artificial graphite layers in sequence from inside to outside are formed.
As a general technical concept, the invention also provides an application of the graphite cathode material in the preparation of a lithium ion battery.
Compared with the prior art, the invention has the advantages that:
(1) the invention provides a preparation method of a graphite cathode material, which is characterized in that flake graphite, a catalyst, a binder and a solvent are used as raw materials to prepare mixed slurry, the binder and the catalyst are uniformly coated on the surface of the flake graphite by a spray drying method, the flake graphite mutually bonded is dispersed by crushing, then the flake graphite coated with the binder and the catalyst is spheroidized to form spherical natural graphite, the inner surface and the outer surface of the spherical natural graphite are uniformly coated with the binder and the catalyst, namely the spherical natural graphite with the inner surface and the outer surface both coated with the binder and the catalyst is prepared, and finally, the graphite cathode material is prepared by graphitization and demagnetizing screening. In the invention, a method combining spray drying, crushing and spheroidizing is adopted, so that the inside and outside surfaces of the spherical natural graphite can be uniformly coated with the binder and the catalyst; based on this, after graphitization, even artificial graphite coating layers are formed on the inner and outer surfaces of the spherical natural graphite, so that an inner and outer surface coating structure comprising an artificial graphite layer, a natural graphite layer and an artificial graphite layer in sequence from inside to outside is formed, and in the graphite negative electrode material, because the inner and outer surfaces of the spherical natural graphite are uniformly coated with the artificial graphite layer, the contact between electrolyte and the natural graphite can be effectively prevented, the cycle performance of the material is improved, meanwhile, in the graphitization process, the binder coated on the inner and outer surfaces of the spherical natural graphite is catalyzed by a catalyst, the graphitization degree of the coated artificial graphite is improved, a high-capacity negative electrode material is obtained, the energy density of the graphite negative electrode material is obviously improved, and the application range of the graphite negative electrode material is widened. Compared with the conventional natural graphite material, the graphite cathode material prepared by the preparation method disclosed by the invention has the advantages of high capacity, good cycle performance and the like, and meanwhile, when the graphite cathode material is prepared into a working electrode for preparing a lithium ion battery, the cycle life of the lithium ion battery can be obviously prolonged, and the graphite cathode material has high use value and good application prospect.
(2) In the preparation method, the solid content of the mixed slurry is optimized to be 5-20%, and the mixed slurry with proper viscosity is obtained by optimizing the solid content of the mixed slurry, so that the adhesive and the catalyst can be coated on the surface of the flake graphite more stably, and the adhesive has strong adhesive action because the adhesive is not cured at high temperature, so that the adhesive and the catalyst cannot fall off in the spray drying, crushing and spheroidizing processes, and the coating of the adhesive and the catalyst cannot be damaged, which is the key point for preparing the artificial graphite layer uniformly coated on the inner surface and the outer surface. Meanwhile, the mass ratio of the flake graphite, the catalyst and the binder in the mixed slurry is optimized to be 60-94: 1-10: 5-30, the mixed slurry with moderate binder content is obtained by optimizing the solid content of the mixed slurry and the dosage ratio of the raw materials, and a coating layer of the binder and the catalyst with proper thickness is favorably formed on the surface of the flake graphite, so that a compact artificial graphite layer with proper thickness is favorably formed on the inner surface and the outer surface of the spherical natural graphite, and finally, the graphite cathode material with higher capacity and better cycle performance is obtained, because if the content of the binder is too low, the thickness of the artificial graphite layer generated in the graphite process is too thin and the thickness uniformity is poor, so that the artificial graphite layer can not be completely and effectively coated on the inner surface and the outer surface of the natural graphite, the coating effect is poor, and the performance cycle of the graphite cathode material is poor due to side reaction between the natural graphite and the electrolyte, if the content of the binder is too high, complete catalysis of the binder may not be achieved because the content of the catalyst is relatively small, resulting in a decrease in product capacity.
(3) The preparation method has the advantages of simple process, convenient operation, low cost, low energy consumption and the like, does not need to adopt organic solvent to wash off redundant binder on the surface of the natural graphite, does not need high-temperature and high-pressure equipment to heat and pressurize, is suitable for large-scale production, and is beneficial to industrialized application.
Drawings
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention.
Fig. 1 is a flow chart of the preparation of the graphite negative electrode material in example 1 of the present invention.
Fig. 2 is an SEM image of the graphite negative electrode material prepared in example 1 of the present invention.
Detailed Description
The invention is further described below with reference to the drawings and specific preferred embodiments of the description, without thereby limiting the scope of protection of the invention.
The materials and equipment used in the following examples are commercially available. In the examples of the present invention, unless otherwise specified, the processes used were conventional processes, the equipment used were conventional equipment, and the data obtained were average values of three or more experiments.
Example 1
A preparation method of a graphite anode material is shown in a preparation flow chart of fig. 1 and comprises the following steps:
(1) adding the crystalline flake graphite with the average particle size of 35 mu m, the SiC (catalyst) with the average particle size of 1.5 mu m and the coal pitch (binder) into acetone according to the mass ratio of the crystalline flake graphite, the catalyst and the binder of 80: 5: 15, controlling the solid content to be 15%, and fully stirring and ultrasonically treating to obtain mixed slurry.
(2) And (2) carrying out spray drying on the mixed slurry obtained in the step (1) to obtain a material in which coal pitch and SiC are mixed and coated on the surface of the crystalline flake graphite, namely the material in which the binder and the catalyst are mixed and coated on the surface of the crystalline flake graphite.
(3) And (3) crushing the material which is obtained in the step (2) and is mixed with the SiC and coated on the surface of the flake graphite, so that each flake graphite is dispersed. The adhesive is not cured at high temperature and has strong adhesive effect, so that the adhesive and the catalyst cannot fall off in the crushing process; meanwhile, due to the existence of the binder, the binder and the catalyst can be uniformly coated on the surface of the crystalline flake graphite.
(4) Spheroidizing the crushed product in the step (3), specifically: the crushed product is put into a continuous shaping system (developed by Zhexin New energy Co., Ltd.) consisting of 8 micro-nano particle shaping and coating systems connected in series at a feeding amount of 100kg/h, the crushed product is shaped (spheroidized) at the rotation speed of a host machine of 4000rpm for 10min, the flaky graphite is curled into spherical natural graphite in the spheroidizing process, and at the moment, the mixture of a binder and a catalyst is uniformly coated on the inner surface and the outer surface of the spherical natural graphite to obtain the spherical natural graphite with the inner surface and the outer surface both coated with the coal tar pitch and the SiC, namely the spherical natural graphite with the inner surface and the outer surface both coated with the binder and the catalyst.
(5) Graphitizing the spherical natural graphite with the inner and outer surfaces coated with the coal pitch and SiC obtained in the step (4), heating to 3000 ℃, and preserving the temperature for 12 hours, wherein in the graphitizing process, the coal pitch coated on the inner and outer surfaces of the spherical natural graphite is catalyzed by SiC to form compact artificial graphite, and the artificial graphite is uniformly coated on the inner and outer surfaces of the spherical natural graphite, so that the spherical natural graphite with the inner and outer surfaces coated with the artificial graphite layer is formed, and the graphite cathode material is obtained by magnetic screening.
In this embodiment, the prepared graphite cathode material includes spherical natural graphite, wherein both the inner and outer surfaces of the spherical natural graphite are coated with an artificial graphite layer, thereby forming an inner and outer coating structure that is an artificial graphite layer, a natural graphite layer, and an artificial graphite layer in sequence from inside to outside.
Fig. 2 is an SEM image of the graphite negative electrode material prepared in example 1 of the present invention. As can be seen from FIG. 2, the preparation method of the present application obtains a dense artificial graphite layer uniformly coated on the surface of the spherical natural graphite.
An application of a graphite cathode material in preparing a lithium ion battery, in particular to a button cell assembled by making the graphite cathode material into a working electrode of the lithium ion battery, which comprises the following steps:
the graphite negative electrode material prepared in example 1, CMC and SBR were uniformly mixed at a mass ratio of 96.5: 1.5: 2 to prepare a slurry, which was coated on a copper foil, and then dried, rolled and punched to prepare a working electrode. The button cell is assembled in a glove box filled with argon, a metal lithium foil is taken as a counter electrode, a diaphragm is a polyethylene/propylene composite microporous membrane, and electrolyte is 1M LiPF6/(EC：EMC)(3︰7)。
An application of a graphite negative electrode material in preparing a lithium ion battery, in particular to a full battery which is assembled by making the graphite negative electrode material into a working electrode of the lithium ion battery, comprising the following steps:
and mixing the graphite negative electrode material, the conductive agent (SP), the CMC and the SBR according to the mass ratio of 95: 1.5: 2, and coating the mixture on a copper foil to obtain a negative electrode pole piece. Mixing LiCoO as positive electrode active material at a mass ratio of 96.5: 2: 1.52And uniformly mixing the conductive agent (SP) and the PVDF, and coating the mixture on an aluminum foil to obtain the positive pole piece. The electrolyte is 1molThe film is a polyethylene/propylene composite microporous film. They are assembled into a battery.
Electrochemical performance of the button cell was tested on a battery tester with a charge-discharge rate of 0.1C and a voltage range of 0.005-2V, as shown in table 1.
And (3) carrying out normal-temperature charging and discharging at the multiplying power of 1C, testing the cycle performance of the full cell within the voltage range of 3.0-4.2V, and showing in table 1.
The results show that: the button cell assembled by the graphite cathode material prepared in the embodiment 1 has the first lithium removal capacity of 369.1mAh/g and the coulombic efficiency of 95.8 percent; the capacity retention rate of the full cell assembled by the graphite cathode material prepared in the embodiment 1 is up to 94.5% at 500 cycles at room temperature and 1C, and the capacity retention rate of the full cell assembled by the graphite cathode material at 1500 cycles at room temperature and 1C is up to 88.2%.
Comparative example 1
Button cells and full cells were prepared in the same manner as in example 1, except that the negative electrode material prepared in example 1 was replaced with the graphite negative electrode material in example 1 as described in chinese patent document CN 107814382 a, and the electrochemical performance results are shown in table 1.
Electrochemical performance test results show that the first lithium removal capacity is 368.6mAh/g, and the coulombic efficiency is 96.8%. The capacity retention rate of 500 weeks of room temperature 1C circulation is up to 92.8%, and the capacity retention rate of 1500 weeks of room temperature 1C circulation is up to 84.8%.
Comparative example 2
A preparation method of a graphite negative electrode material comprises the following steps:
(1) flake graphite with an average particle size of 35 μm, coal pitch and SiC with an average particle size of 1.5 μm were mixed in a mass ratio of 80: 15: 5 to obtain a mixture.
(2) And (2) graphitizing the mixed product obtained in the step (1), heating to 3000 ℃, and keeping the temperature for 12 h. And (4) demagnetizing and screening the product to obtain the graphite cathode material.
Button cells and full cells were prepared from the graphite negative electrode material prepared in comparative example 2 by the method of example 1, and the electrochemical performance results are shown in table 1.
The results show that: in the comparative example 2, the first lithium removal capacity is 367.5mAh/g, the coulombic efficiency is 95.5%, the capacity retention rate is 80.2% at most after 500 cycles at room temperature and 1C, and the capacity retention rate is 66.3% at most after 1500 cycles at room temperature and 1C.
Example 2
A method for preparing a graphite anode material, which is substantially the same as that in example 1, except that: in step (1) of example 2, the solid content of the mixed slurry was 1%.
Button cells and full cells were prepared from the graphite negative electrode material prepared in example 2 by the method of example 1, and the electrochemical performance results are shown in table 1.
Example 3
A method for preparing a graphite anode material, which is substantially the same as that in example 1, except that: in step (1) of example 3, the solid content of the mixed slurry was 5%.
Button cells and full cells were prepared from the graphite negative electrode material prepared in example 3 by the method of example 1, and the electrochemical performance results are shown in table 1.
Example 4
A method for preparing a graphite anode material, which is substantially the same as that in example 1, except that: in step (1) of example 4, the solid content of the mixed slurry was 10%.
Button cells and full cells were prepared from the graphite negative electrode material prepared in example 4 by the method of example 1, and the electrochemical performance results are shown in table 1.
Example 5
A method for preparing a graphite anode material, which is substantially the same as that in example 1, except that: in step (1) of example 5, the solid content of the mixed slurry was 20%.
Button cells and full cells were prepared from the graphite negative electrode material prepared in example 5 by the method of example 1, and the electrochemical performance results are shown in table 1.
Example 6
A method for preparing a graphite anode material, which is substantially the same as that in example 1, except that: in step (1) of example 6, the solid content of the mixed slurry was 25%.
Button cells and full cells were prepared from the graphite negative electrode material prepared in example 6 by the method of example 1, and the electrochemical performance results are shown in table 1.
Example 7
A method for preparing a graphite anode material, which is substantially the same as that in example 1, except that: in the step (1) of example 7, the mass ratio of the crystalline flake graphite, the catalyst and the binder is 72: 8: 20.
And the spheroidizing process parameters in the step (4) are as follows: the crushed product is put into a continuous shaping system formed by connecting 8 micro-nano particle shaping and coating systems in series under the feeding quantity of 100kg/h, and is shaped (spheroidized) at the rotating speed of a main machine of 5000rpm for 15 min.
Button cells and full cells were prepared from the graphite negative electrode material prepared in example 7 by the method of example 1, and the electrochemical performance results are shown in table 1.
Example 8
A method for preparing a graphite anode material, which is substantially the same as that in example 1, except that: in the step (1) of example 8, the mass ratio of the crystalline flake graphite, the catalyst and the binder is 72: 8: 20.
And (5) graphitizing and heating to 3100 ℃, and keeping the temperature for 15 h.
Button cells and full cells were prepared from the graphite negative electrode material prepared in example 8 by the method of example 1, and the electrochemical performance results are shown in table 1.
TABLE 1 electrochemical Performance test results for button cells and full cells made of different graphite materials
From the results, compared with the conventional natural graphite material, the graphite cathode material prepared by the method has the advantages of high capacity, good cycle performance and the like, can obviously prolong the cycle life of a lithium ion battery when being used as the cathode material of a working electrode for preparing the lithium ion battery, and has high use value and good application prospect.
The above examples are merely preferred embodiments of the present invention, and the scope of the present invention is not limited to the above examples. All technical schemes belonging to the idea of the invention belong to the protection scope of the invention. It should be noted that modifications and embellishments within the scope of the invention may be made by those skilled in the art without departing from the principle of the invention, and such modifications and embellishments should also be considered as within the scope of the invention.
Claims (10)
1. The preparation method of the graphite negative electrode material is characterized by comprising the following steps of:
s1, mixing the flake graphite, the catalyst, the binder and the solvent to prepare mixed slurry;
s2, spray drying the mixed slurry obtained in the step S1 to obtain a material in which a binder and a catalyst are mixed and coated on the surface of the flake graphite;
s3, mixing the binder and the catalyst obtained in the step S2 and coating the mixture on the material on the surface of the flake graphite, and crushing and spheroidizing the mixture to obtain spherical natural graphite with the inner surface and the outer surface both coated with the binder and the catalyst;
and S4, graphitizing the spherical natural graphite with the inner and outer surfaces coated with the binder and the catalyst obtained in the step S3, and performing magnetic screening to obtain the graphite cathode material.
2. The method according to claim 1, wherein in step S1, the solid content of the mixed slurry is 5% to 20%.
3. The preparation method according to claim 2, wherein in step S1, the mass ratio of the flake graphite, the catalyst and the binder in the mixed slurry is 60-94: 1-10: 5-30.
4. The production method according to claim 3, wherein the average particle size of the flake graphite is 3 to 45 μm; the catalyst is one or more of carbide or oxide of silicon, iron, tin or boron; the average particle size of the catalyst is 1-5 mu m; the binder is one or more of petroleum asphalt, coal asphalt, mesophase asphalt, coal tar or heavy oil.
5. The method according to claim 2, wherein in step S1, the solvent is one or more of acetone, diethyl ether, xylene, carbon tetrachloride, n-hexane, or ethanol.
6. The preparation method according to any one of claims 1 to 5, wherein in step S3, the spheroidization is performed in a continuous shaping system composed of 2 to 15 micro-nano particle shaping and coating systems connected in series; the spheroidizing process parameters are as follows: the feeding amount is 50 kg-200 kg/h, the rotating speed is 100 rpm-9000 rpm, and the time is 5 min-45 min.
7. The production method according to any one of claims 1 to 5, wherein in step S4, the graphitization is performed at a temperature of 2800 ℃ to 3200 ℃; the heat preservation time in the graphitization process is 4-20 h.
8. A graphite negative electrode material, which is prepared by the preparation method of any one of claims 1 to 7.
9. The graphitic negative electrode material according to claim 8, characterized in that it comprises spheroidal natural graphite; the inner surface and the outer surface of the spherical natural graphite are coated with artificial graphite layers, so that an inner coating structure and an outer coating structure which are the artificial graphite layers, the natural graphite layers and the artificial graphite layers in sequence from inside to outside are formed.
10. Use of the graphite anode material of claim 8 or 9 for the preparation of a lithium ion battery.
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