CN110817855B - Preparation method of modified natural graphite negative electrode material - Google Patents
Preparation method of modified natural graphite negative electrode material Download PDFInfo
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- CN110817855B CN110817855B CN201911135142.8A CN201911135142A CN110817855B CN 110817855 B CN110817855 B CN 110817855B CN 201911135142 A CN201911135142 A CN 201911135142A CN 110817855 B CN110817855 B CN 110817855B
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- 229910021382 natural graphite Inorganic materials 0.000 title claims abstract description 93
- 238000002360 preparation method Methods 0.000 title claims abstract description 23
- 239000007773 negative electrode material Substances 0.000 title claims description 22
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 55
- 239000011248 coating agent Substances 0.000 claims abstract description 34
- 238000000576 coating method Methods 0.000 claims abstract description 23
- 239000007787 solid Substances 0.000 claims abstract description 21
- 238000000034 method Methods 0.000 claims abstract description 14
- 238000007493 shaping process Methods 0.000 claims abstract description 14
- 238000001816 cooling Methods 0.000 claims abstract description 13
- 238000001035 drying Methods 0.000 claims abstract description 11
- 238000001914 filtration Methods 0.000 claims abstract description 11
- 238000005406 washing Methods 0.000 claims abstract description 11
- 230000001590 oxidative effect Effects 0.000 claims abstract description 7
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 claims description 24
- 229910002804 graphite Inorganic materials 0.000 claims description 18
- 239000010439 graphite Substances 0.000 claims description 18
- 238000002156 mixing Methods 0.000 claims description 18
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 15
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 15
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 claims description 12
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 claims description 12
- BDAGIHXWWSANSR-UHFFFAOYSA-N methanoic acid Natural products OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 0.000 claims description 12
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 10
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims description 10
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 claims description 10
- 229910017604 nitric acid Inorganic materials 0.000 claims description 10
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 9
- WQZGKKKJIJFFOK-GASJEMHNSA-N Glucose Natural products OC[C@H]1OC(O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-GASJEMHNSA-N 0.000 claims description 9
- 238000003763 carbonization Methods 0.000 claims description 9
- 239000008367 deionised water Substances 0.000 claims description 9
- 229910021641 deionized water Inorganic materials 0.000 claims description 9
- 239000008103 glucose Substances 0.000 claims description 9
- 238000010438 heat treatment Methods 0.000 claims description 9
- 239000002245 particle Substances 0.000 claims description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 9
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 8
- 229910052799 carbon Inorganic materials 0.000 claims description 8
- 239000007800 oxidant agent Substances 0.000 claims description 8
- 238000005507 spraying Methods 0.000 claims description 8
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 7
- KXGFMDJXCMQABM-UHFFFAOYSA-N 2-methoxy-6-methylphenol Chemical compound [CH]OC1=CC=CC([CH])=C1O KXGFMDJXCMQABM-UHFFFAOYSA-N 0.000 claims description 6
- OSWFIVFLDKOXQC-UHFFFAOYSA-N 4-(3-methoxyphenyl)aniline Chemical compound COC1=CC=CC(C=2C=CC(N)=CC=2)=C1 OSWFIVFLDKOXQC-UHFFFAOYSA-N 0.000 claims description 6
- 239000002202 Polyethylene glycol Substances 0.000 claims description 6
- CZMRCDWAGMRECN-UGDNZRGBSA-N Sucrose Chemical compound O[C@H]1[C@H](O)[C@@H](CO)O[C@@]1(CO)O[C@@H]1[C@H](O)[C@@H](O)[C@H](O)[C@@H](CO)O1 CZMRCDWAGMRECN-UGDNZRGBSA-N 0.000 claims description 6
- 229930006000 Sucrose Natural products 0.000 claims description 6
- 239000010426 asphalt Substances 0.000 claims description 6
- 235000019253 formic acid Nutrition 0.000 claims description 6
- 230000003647 oxidation Effects 0.000 claims description 6
- 238000007254 oxidation reaction Methods 0.000 claims description 6
- 239000005011 phenolic resin Substances 0.000 claims description 6
- 229920001568 phenolic resin Polymers 0.000 claims description 6
- 229920001223 polyethylene glycol Polymers 0.000 claims description 6
- 239000005720 sucrose Substances 0.000 claims description 6
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims description 5
- 239000001307 helium Substances 0.000 claims description 5
- 229910052734 helium Inorganic materials 0.000 claims description 5
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 claims description 5
- 238000000746 purification Methods 0.000 claims description 5
- QAOWNCQODCNURD-UHFFFAOYSA-N sulfuric acid Substances OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 5
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 claims description 5
- 229910052786 argon Inorganic materials 0.000 claims description 4
- WQZGKKKJIJFFOK-VFUOTHLCSA-N beta-D-glucose Chemical compound OC[C@H]1O[C@@H](O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-VFUOTHLCSA-N 0.000 claims description 4
- 239000003795 chemical substances by application Substances 0.000 claims description 4
- 239000000138 intercalating agent Substances 0.000 claims description 4
- 238000009830 intercalation Methods 0.000 claims description 4
- 230000002687 intercalation Effects 0.000 claims description 4
- 235000006408 oxalic acid Nutrition 0.000 claims description 4
- 235000011054 acetic acid Nutrition 0.000 claims description 3
- 229910052757 nitrogen Inorganic materials 0.000 claims description 3
- 235000011007 phosphoric acid Nutrition 0.000 claims description 3
- 230000035484 reaction time Effects 0.000 claims description 3
- 239000002904 solvent Substances 0.000 claims description 3
- 239000010406 cathode material Substances 0.000 abstract description 19
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 abstract description 6
- 229910001416 lithium ion Inorganic materials 0.000 abstract description 6
- 238000009776 industrial production Methods 0.000 abstract description 4
- 239000000126 substance Substances 0.000 abstract description 2
- 238000010000 carbonizing Methods 0.000 abstract 1
- 239000010410 layer Substances 0.000 description 12
- 230000000052 comparative effect Effects 0.000 description 8
- 238000003756 stirring Methods 0.000 description 8
- 238000006243 chemical reaction Methods 0.000 description 5
- 239000003792 electrolyte Substances 0.000 description 5
- 230000007547 defect Effects 0.000 description 4
- 239000007789 gas Substances 0.000 description 4
- 229910021645 metal ion Inorganic materials 0.000 description 4
- 239000011247 coating layer Substances 0.000 description 3
- 230000007797 corrosion Effects 0.000 description 3
- 238000005260 corrosion Methods 0.000 description 3
- 229910001873 dinitrogen Inorganic materials 0.000 description 3
- 238000007599 discharging Methods 0.000 description 3
- 230000014759 maintenance of location Effects 0.000 description 3
- 238000004146 energy storage Methods 0.000 description 2
- 229910013872 LiPF Inorganic materials 0.000 description 1
- 101150058243 Lipf gene Proteins 0.000 description 1
- 229910003481 amorphous carbon Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000003139 buffering effect Effects 0.000 description 1
- 210000004027 cell Anatomy 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 210000001787 dendrite Anatomy 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000011229 interlayer Substances 0.000 description 1
- 150000007522 mineralic acids Chemical class 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000005416 organic matter Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
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- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/15—Nano-sized carbon materials
- C01B32/182—Graphene
- C01B32/194—After-treatment
- C01B32/196—Purification
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- 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
- C01B32/15—Nano-sized carbon materials
- C01B32/182—Graphene
- C01B32/194—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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- 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
- H01M4/362—Composites
- H01M4/366—Composites as layered products
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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
- H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
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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
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- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
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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
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Abstract
The invention discloses a preparation method of a modified natural graphite cathode material, and belongs to the technical field of preparation of lithium ion battery cathode materials. The preparation method comprises the steps of simultaneously purifying and oxidizing and expanding layers of natural graphite, separating and filtering solid substances, washing and drying, shaping the natural graphite to obtain spheroidal graphite powder, coating an organic coating agent on the surface of the spheroidal graphite powder, cooling to room temperature, taking out, carbonizing at high temperature under the protection of inert atmosphere, and cooling to room temperature to obtain the modified natural graphite. The preparation method can effectively improve the high-rate charge-discharge performance and the first coulombic efficiency of the natural graphite cathode material, and has the advantages of simple and easily-controlled process, low cost and easy industrial production.
Description
Technical Field
The invention relates to the technical field of preparation of lithium ion battery cathode materials, in particular to a preparation method of a modified natural graphite cathode material.
Background
The lithium ion battery is widely applied to the fields of 3C products, power energy storage and the like, and the graphite micropowder is mainly used as a negative electrode material of the lithium ion battery at present and is a key factor influencing the performance of the lithium ion battery. The natural graphite has the characteristics of high specific capacity, good charge and discharge platform, wide source, low cost and the like, but the large-scale application of the natural graphite is limited by the defects of poor compatibility with battery electrolyte, low rate performance, poor charge and discharge cycle performance and the like. Therefore, the modification of the natural graphite to improve the electrical property and the energy storage property of the natural graphite becomes a key for the popularization and application of the natural graphite in the high-end lithium ion battery cathode material.
The Chinese patent CN108832124A discloses that the surface of natural graphite is coated with a mesoporous graphite structure after purification, the surface structure and chemical properties of natural graphite are improved, the first coulombic efficiency and cycle performance of natural graphite are improved, but the defects of natural graphite such as anisotropy and small interlayer spacing are not improved, so that the large-current charge and discharge performance of modified natural graphite is limited. CN108751187A utilizes inorganic acid to oxidize natural graphite to improve its cycle stability, but the defect and active site exposed after oxidation limit the promotion of first coulomb efficiency. CN104505491B utilizes metal ions to carry out surface amorphous carbon coating after the metal ions are subjected to layer expanding, the multiplying power performance and the cycle performance of the natural graphite are improved, but the metal ions existing in the structure gradually migrate to the surface of the negative electrode along with the charging and discharging and possibly form dendrites, and the safety of the battery is seriously influenced.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide the preparation method of the modified natural graphite cathode material, which can effectively improve the high-rate charge-discharge performance and the first coulombic efficiency of the natural graphite cathode material, has a simple and easily-controlled process, and is easy for industrial production.
In order to solve the problems, the technical scheme adopted by the invention is as follows:
a preparation method of a modified natural graphite negative electrode material comprises the following steps:
s1, purification and oxidation layer expansion: mixing natural graphite with an oxidant, an intercalating agent and hydrofluoric acid, purifying and expanding at 0-50 ℃ for 30-120 min, separating and filtering out a solid, washing the solid to a pH value of 5-7, and drying for later use;
s2, shaping: shaping the natural graphite processed in the step S1 into spheroidal graphite powder with D50 particle size of 5-30 μm;
s3, surface coating: placing the natural graphite treated in the step S2 into a cavity of fluidized bed equipment, spraying a solution containing an organic coating agent into a fluidized bed for coating, wherein the coating reaction time is 0.5-2 h, and taking out the natural graphite for later use after cooling to room temperature;
s4, high-temperature carbonization: and (5) heating the spheroidal graphite powder obtained in the step (S3) to 600-1200 ℃ under the protection of inert atmosphere, preserving heat for 1-6 h, and taking out after cooling to room temperature to obtain the modified natural graphite.
In a preferred embodiment of the present invention, in step S1, the mass ratio of the natural graphite to the oxidizing agent, the intercalating agent, and the hydrofluoric acid is 1:0.03 to 1.5:0.1 to 15: 0.05.
In a preferred embodiment of the present invention, the natural graphite in step S1 is at least one of high-carbon graphite, high-purity graphite, and spherical graphite.
In a preferred embodiment of the present invention, the oxidizing agent in step S1 is at least one of concentrated nitric acid, concentrated sulfuric acid, and hydrogen peroxide.
As a preferred embodiment of the present invention, the intercalation agent in step S1 is at least one of concentrated nitric acid, phosphoric acid, formic acid, acetic acid and oxalic acid.
In a preferred embodiment of the present invention, the mass ratio of the organic coating agent to the spheroidal graphite powder in step S3 is 0.001 to 0.1: 1
In a preferred embodiment of the present invention, the organic coating agent-containing solution in step S3 is present in an amount of 1 to 65% by mass.
In a preferred embodiment of the present invention, the organic coating agent in step S3 is at least one of glucose, sucrose, phenolic resin, polyethylene glycol, and asphalt; the solvent used in step S3 is at least one of deionized water, methanol, ethanol, and tetrahydrofuran.
In a preferred embodiment of the present invention, the temperature of the gas supplied to the fluidized bed in step S3 is 60 to 150 ℃.
As a preferred embodiment of the present invention, the inert atmosphere in step S4 is nitrogen, argon or helium.
Compared with the prior art, the invention has the beneficial effects that:
(1) the preparation method of the invention synchronously carries out the purification process and the oxidation layer expanding process of the natural graphite, simplifies the process, increases the types of the raw materials of the natural graphite which can be processed, and enlarges the universality of the preparation process;
(2) according to the invention, the organic matter or inorganic acid radical is used for expanding the graphite sheet layer, so that the high-rate charge and discharge capacity of the graphite cathode material is improved; compared with the method of using metal ions to expand the layer, the method improves the safety of the modified natural graphite as the cathode, and can also use inorganic acid radical decomposition products to dope the graphite, thereby changing the electron density of the graphite sheet layer and further improving the electrochemical performance;
(3) compared with the traditional coating process, the novel coating process of the fluidized bed can realize the uniform coating of an extremely thin coating layer, avoid the corrosion of electrolyte to graphite layers caused by nonuniform coating and improve the circulation stability;
in conclusion, the preparation method provided by the invention can effectively improve the high-rate charge-discharge performance and the first coulombic efficiency of the natural graphite negative electrode material, and is simple and easy to control in process, low in cost and easy for industrial production.
Detailed Description
The present invention will be described in further detail with reference to specific embodiments.
A preparation method of a modified natural graphite negative electrode material comprises the following steps:
s1, purification and oxidation layer expansion: mixing natural graphite with an oxidant, an intercalating agent and hydrofluoric acid according to a mass ratio of 1: 0.03-1.5: 0.1-15: 0.05, purifying and expanding at 0-50 ℃ for 30-120 min, separating and filtering out a solid, washing the solid to a pH value of 5-7, and drying for later use;
s2, shaping: shaping the natural graphite processed in the step S1 into spheroidal graphite powder with D50 particle size of 5-30 μm;
s3, surface coating: placing the natural graphite treated in the step S2 into a cavity of fluidized bed equipment, spraying a solution containing an organic coating agent into a fluidized bed for coating, wherein the air inlet temperature of the fluidized bed is 60-150 ℃, the coating reaction time is 0.5-2 h, and taking out the natural graphite for later use after cooling to room temperature;
s4, high-temperature carbonization: and (5) heating the natural graphite obtained in the step (S3) to 600-1200 ℃ under the protection of inert atmosphere, preserving heat for 1-6 h, and taking out the natural graphite after cooling to room temperature to obtain the modified natural graphite.
In the above step, the natural graphite in step S1 is at least one of high-carbon graphite, high-purity graphite, and spherical graphite, and when the spherical graphite is used as the natural graphite, the shaping process in step S2 does not need to be performed on the natural graphite. The oxidant is at least one of concentrated nitric acid, concentrated sulfuric acid and hydrogen peroxide, and the intercalation agent is at least one of concentrated nitric acid, phosphoric acid, formic acid, acetic acid and oxalic acid.
In the step S3, the mass ratio of the organic coating agent to the spheroidal graphite powder is 0.001-0.1: 1; the mass fraction of the solution containing the organic coating agent is 1-65%. Specifically, the organic coating agent is at least one of glucose, sucrose, phenolic resin, polyethylene glycol and asphalt; the solvent is at least one of deionized water, methanol, ethanol and tetrahydrofuran.
The inert atmosphere in step S4 is nitrogen or argon or helium.
Example 1:
a preparation method of a modified natural graphite negative electrode material comprises the following steps:
s1, mixing high-carbon natural graphite, concentrated nitric acid, formic acid and hydrofluoric acid according to a solute mass ratio of 1: 0.03: 15:0.05 stirring and mixing for 30min at 0 ℃, separating and filtering out solid matters, washing the solid matters until the pH value is 5-7, and drying;
s2, shaping the natural graphite obtained in the step S1 into spheroidal graphite powder with the particle size of D50 being 5 mu m;
s3, placing the spheroidal graphite powder obtained in the step S2 in a fluidized bed, adjusting the air inlet temperature to 120 ℃, spraying a deionized water solution of glucose into the fluidized bed, carrying out coating reaction for 0.5h, cooling to room temperature, and taking out; wherein the mass of the glucose is 0.1 percent of that of the spheroidal graphite powder, and the mass fraction of the deionized water solution of the glucose is 1 percent;
and S4, under the protection of nitrogen gas, carrying out carbonization heat treatment on the spheroidal graphite powder obtained in the step S3 at 600 ℃ for 6 hours to obtain the modified natural graphite cathode material.
Example 2:
a preparation method of a modified natural graphite negative electrode material comprises the following steps:
s1, mixing high-carbon natural graphite, 30% hydrogen peroxide solution, phosphoric acid and hydrofluoric acid according to a solute mass ratio of 1: 1.5: 0.1: 0.05 stirring and mixing for 120min at 20 ℃, separating and filtering out solid matters, washing the solid matters until the pH value is 5-7, and drying;
s2, shaping the natural graphite obtained in the step S1 into spheroidal graphite powder with the D50 grain diameter of 10 mu m;
s3, placing the spheroidal graphite powder obtained in the step S2 in a fluidized bed, adjusting the air inlet temperature to 80 ℃, spraying an ethanol solution of phenolic resin into the fluidized bed, carrying out coating reaction for 2 hours, cooling to room temperature, and taking out; wherein the mass of the phenolic resin is 10 percent of that of the spheroidal graphite powder, and the mass fraction of the ethanol solution of the phenolic resin is 10 percent;
and S4, under the protection of argon gas, carrying out carbonization heat treatment on the spheroidal graphite powder obtained in the step S3 at 800 ℃ for 4h to obtain the modified natural graphite cathode material.
Example 3:
a preparation method of a modified natural graphite negative electrode material comprises the following steps:
s1, mixing high-purity natural graphite, concentrated sulfuric acid, acetic acid and hydrofluoric acid according to a solute mass ratio of 1: 1: 0.5: 0.05 stirring and mixing for 60min at 50 ℃, separating and filtering out solid matters, washing the solid matters until the pH value is 5-7, and drying;
s2, shaping the natural graphite obtained in the step S1 into spheroidal graphite powder with the particle size of D50 being 30 mu m;
s3, placing the spheroidal graphite powder obtained in the step S2 in a fluidized bed, adjusting the air inlet temperature to 150 ℃, spraying a deionized water solution of sucrose into the fluidized bed, carrying out coating reaction for 1 hour, cooling to room temperature, and taking out; wherein the mass of the sucrose is 5 percent of that of the spheroidal graphite powder, and the mass fraction of the deionized water solution of the sucrose is 65 percent;
and S4, under the protection of helium gas, carrying out carbonization heat treatment on the spheroidal graphite powder obtained in the step S3 at 1000 ℃ for 2h to obtain the modified natural graphite cathode material.
Example 4:
a preparation method of a modified natural graphite negative electrode material comprises the following steps:
s1, mixing spherical natural graphite, concentrated nitric acid, oxalic acid and hydrofluoric acid according to a solute mass ratio of 1: 0.1: 10: 0.05 stirring and mixing for 60min at 30 ℃, separating and filtering out solid matters, washing the solid matters until the pH value is 5-7, and drying;
s2, placing the spherical graphite powder obtained in the step S1 in a fluidized bed, adjusting the air inlet temperature to 60 ℃, spraying a methanol solution of polyethylene glycol into the fluidized bed, carrying out coating reaction for 2 hours, cooling to room temperature, and taking out; wherein the mass of the polyethylene glycol is 8 percent of that of the spheroidal graphite powder, and the mass fraction of the methanol solution of the polyethylene glycol is 40 percent;
and S4, under the protection of helium gas, carrying out carbonization heat treatment on the spherical graphite powder obtained in the step S2 at 1200 ℃ for 1h to obtain the modified natural graphite cathode material.
Example 5:
a preparation method of a modified natural graphite negative electrode material comprises the following steps:
s1, mixing high-purity natural graphite, concentrated sulfuric acid, phosphoric acid and hydrofluoric acid according to a solute mass ratio of 1: 0.6: 4: 0.05 stirring and mixing for 60min at 50 ℃, separating and filtering out solid matters, washing the solid matters until the pH value is 5-7, and drying;
s2, shaping the natural graphite obtained in the step S1 into spheroidal graphite powder with the particle size of D50 being 15 mu m;
s3, placing the spheroidal graphite powder obtained in the step S2 in a fluidized bed, adjusting the air inlet temperature to 80 ℃, spraying a tetrahydrofuran solution of asphalt into the fluidized bed, carrying out coating reaction for 1 hour, cooling to room temperature, and taking out; wherein the mass of the asphalt is 2 percent of that of the spheroidal graphite powder, and the mass fraction of the tetrahydrofuran solution of the asphalt is 10 percent;
and S4, under the protection of nitrogen gas, carrying out carbonization heat treatment on the spheroidal graphite powder obtained in the step S3 at 1200 ℃ for 2h to obtain the modified natural graphite cathode material.
Comparative example 1:
the high-carbon natural graphite used in example 1 was shaped into graphite powder having a particle size of 10 μm of D50, which was used as comparative example 1.
Comparative example 2:
a preparation method of a modified natural graphite negative electrode material comprises the following steps:
s1, mixing high-carbon natural graphite, concentrated nitric acid, formic acid and hydrofluoric acid according to a solute mass ratio of 1: 0.03: 15:0.05 stirring and mixing for 30min at 0 ℃, separating and filtering out solid matters, washing the solid matters until the pH value is 5-7, and drying;
s2, shaping the natural graphite obtained in the step S1 into graphite powder with the particle size of D50 being 10 mu m, and obtaining a modified natural graphite cathode material;
comparative example 3:
a preparation method of a modified natural graphite negative electrode material comprises the following steps:
s1, mixing high-carbon natural graphite, concentrated nitric acid, formic acid and hydrofluoric acid according to a solute mass ratio of 1: 0.03: 15:0.05 stirring and mixing for 30min at 0 ℃, separating and filtering out solid matters, washing the solid matters until the pH value is 5-7, and drying;
s2, shaping the natural graphite obtained in the step S1 into graphite powder with the particle size of D50 being 10 mu m;
s3, mixing the graphite powder obtained in the step S2 with glucose and deionized water, stirring and evaporating to dryness; wherein the mass of the glucose is 0.1 percent of that of the graphite powder, and the mass of the glucose is 1 percent of that of the deionized water;
and S4, under the protection of nitrogen gas, carrying out carbonization heat treatment on the graphite powder obtained in the step S3 at 600 ℃ for 6h to obtain the modified natural graphite cathode material.
Performance comparison experiment:
the modified natural graphite negative electrode materials prepared in the five embodiments and the modified natural graphite negative electrode materials of the three comparative examples are respectively made into pole pieces and used as working electrodes, and LiPF is used6The method comprises the steps of assembling a button cell by using/DMC + EC + DEC (1: 1: 1) as an electrolyte, carrying out charging and discharging until the voltage is 0.01-0.8V, and measuring the first charging specific capacity, the first coulombic efficiency and the 50-week cycle retention rate, wherein the results are shown in Table 1.
TABLE 1 comparison of initial specific charge capacity, initial coulombic efficiency, 50 cycle retention
As can be seen from table 1, compared with the unmodified natural graphite negative electrode material in comparative example 1 and the natural graphite negative electrode material modified only by layer expansion in comparative example 2, the first charge specific capacity, the first coulombic efficiency, the 50-cycle retention rate, and the rate of the modified natural graphite negative electrode material prepared in the five embodiments of the present invention are all greatly improved, which indicates that the electrochemical performance of the natural graphite can be improved by oxidation layer expansion and surface coating. In addition, compared with the modified natural graphite cathode material in the comparative example 3, the modified natural graphite cathode material prepared in the five examples shows that the uniform coating layer prepared by the fluidized bed can avoid the corrosion of the electrolyte to the graphite layers, improve the first coulombic efficiency, and simultaneously play a role in storage and buffering in the large-current charging and discharging process, eliminate the anisotropy of the natural graphite and improve the rate capability.
In conclusion, the preparation method disclosed by the invention is simple and easy to control in process, low in cost and easy for industrial production, can realize uniform coating of an extremely thin coating layer, avoids corrosion of an electrolyte to graphite layers caused by nonuniform coating, and improves the cycle stability, so that the high-rate charge and discharge performance and the first coulombic efficiency of a natural graphite cathode material can be effectively improved.
The above embodiments are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited thereby, and any insubstantial changes and substitutions made by those skilled in the art based on the present invention are within the protection scope of the present invention.
Claims (4)
1. A preparation method of a modified natural graphite negative electrode material is characterized by comprising the following steps: the method comprises the following steps:
s1, purification and oxidation layer expansion: mixing natural graphite with an oxidant, an intercalating agent and hydrofluoric acid, purifying and expanding at 0-50 ℃ for 30-120 min, separating and filtering out a solid, washing the solid to a pH value of 5-7, and drying for later use; wherein the mass ratio of the natural graphite to the oxidant, the intercalation agent and the hydrofluoric acid is 1: 0.03-1.5: 0.1-15: 0.05; the oxidant is at least one of concentrated nitric acid, concentrated sulfuric acid and hydrogen peroxide, and the intercalation agent is at least one of concentrated nitric acid, phosphoric acid, formic acid, acetic acid and oxalic acid;
s2, shaping: shaping the natural graphite processed in the step S1 into spheroidal graphite powder with D50 particle size of 5-30 μm;
s3, surface coating: placing the spheroidal graphite powder treated in the step S2 in a cavity of fluidized bed equipment, spraying a solution containing an organic coating agent into a fluidized bed for coating, wherein the coating reaction time is 0.5-2 h, the air inlet temperature of the fluidized bed is 60-150 ℃, and taking out the spheroidal graphite powder for later use after cooling to room temperature; wherein the mass fraction of the solution containing the organic coating agent is 1-65%, and the mass ratio of the organic coating agent to the spheroidal graphite powder is 0.001-0.1: 1;
s4, high-temperature carbonization: and (5) heating the natural graphite obtained in the step (S3) to 600-1200 ℃ under the protection of inert atmosphere, preserving heat for 1-6 h, and taking out after cooling to room temperature to obtain the modified natural graphite.
2. The method for preparing the modified natural graphite negative electrode material according to claim 1, characterized in that: the natural graphite in the step S1 is at least one of high-carbon graphite, high-purity graphite, and spherical graphite.
3. The method for preparing the modified natural graphite negative electrode material according to claim 1, characterized in that: the organic coating agent in the step S3 is at least one of glucose, sucrose, phenolic resin, polyethylene glycol and asphalt; the solvent used in step S3 is at least one of deionized water, methanol, ethanol, and tetrahydrofuran.
4. The method for preparing the modified natural graphite negative electrode material according to claim 1, characterized in that: the inert atmosphere in step S4 is nitrogen, argon or helium.
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| CN113130876A (en) * | 2021-04-19 | 2021-07-16 | 合肥国轩高科动力能源有限公司 | Preparation method and application of acid-modified spherical natural graphite negative electrode material |
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