CN114843483B - Hard carbon composite material and preparation method and application thereof - Google Patents
Hard carbon composite material and preparation method and application thereof Download PDFInfo
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- CN114843483B CN114843483B CN202210567487.6A CN202210567487A CN114843483B CN 114843483 B CN114843483 B CN 114843483B CN 202210567487 A CN202210567487 A CN 202210567487A CN 114843483 B CN114843483 B CN 114843483B
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- 229910021385 hard carbon Inorganic materials 0.000 title claims abstract description 81
- 239000002131 composite material Substances 0.000 title claims abstract description 44
- 238000002360 preparation method Methods 0.000 title claims description 29
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 37
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 37
- 239000007833 carbon precursor Substances 0.000 claims abstract description 33
- 229910018068 Li 2 O Inorganic materials 0.000 claims abstract description 31
- 239000000654 additive Substances 0.000 claims abstract description 31
- 230000000996 additive effect Effects 0.000 claims abstract description 31
- UIIMBOGNXHQVGW-UHFFFAOYSA-M Sodium bicarbonate Chemical compound [Na+].OC([O-])=O UIIMBOGNXHQVGW-UHFFFAOYSA-M 0.000 claims abstract description 30
- 230000001502 supplementing effect Effects 0.000 claims abstract description 28
- 235000013162 Cocos nucifera Nutrition 0.000 claims abstract description 22
- 244000060011 Cocos nucifera Species 0.000 claims abstract description 22
- 239000000843 powder Substances 0.000 claims abstract description 20
- 238000002156 mixing Methods 0.000 claims abstract description 16
- 229910000030 sodium bicarbonate Inorganic materials 0.000 claims abstract description 15
- 235000017557 sodium bicarbonate Nutrition 0.000 claims abstract description 15
- 239000007822 coupling agent Substances 0.000 claims abstract description 12
- 239000003054 catalyst Substances 0.000 claims abstract description 11
- 229910021384 soft carbon Inorganic materials 0.000 claims abstract description 7
- 239000000725 suspension Substances 0.000 claims abstract description 7
- 238000000197 pyrolysis Methods 0.000 claims abstract description 6
- 239000000203 mixture Substances 0.000 claims abstract description 5
- 239000002253 acid Substances 0.000 claims description 24
- VZGDMQKNWNREIO-UHFFFAOYSA-N tetrachloromethane Chemical compound ClC(Cl)(Cl)Cl VZGDMQKNWNREIO-UHFFFAOYSA-N 0.000 claims description 20
- ZMANZCXQSJIPKH-UHFFFAOYSA-N Triethylamine Chemical compound CCN(CC)CC ZMANZCXQSJIPKH-UHFFFAOYSA-N 0.000 claims description 12
- 239000003960 organic solvent Substances 0.000 claims description 10
- 238000000034 method Methods 0.000 claims description 9
- 238000001694 spray drying Methods 0.000 claims description 8
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 7
- 238000000498 ball milling Methods 0.000 claims description 7
- 238000003763 carbonization Methods 0.000 claims description 7
- VHYFNPMBLIVWCW-UHFFFAOYSA-N 4-Dimethylaminopyridine Chemical compound CN(C)C1=CC=NC=C1 VHYFNPMBLIVWCW-UHFFFAOYSA-N 0.000 claims description 6
- 238000003756 stirring Methods 0.000 claims description 6
- XDTMQSROBMDMFD-UHFFFAOYSA-N Cyclohexane Chemical compound C1CCCCC1 XDTMQSROBMDMFD-UHFFFAOYSA-N 0.000 claims description 5
- 238000010306 acid treatment Methods 0.000 claims description 5
- 239000002245 particle Substances 0.000 claims description 5
- 239000012298 atmosphere Substances 0.000 claims description 4
- FWDBOZPQNFPOLF-UHFFFAOYSA-N ethenyl(triethoxy)silane Chemical compound CCO[Si](OCC)(OCC)C=C FWDBOZPQNFPOLF-UHFFFAOYSA-N 0.000 claims description 4
- 239000007773 negative electrode material Substances 0.000 claims description 4
- IMNIMPAHZVJRPE-UHFFFAOYSA-N triethylenediamine Chemical compound C1CN2CCN1CC2 IMNIMPAHZVJRPE-UHFFFAOYSA-N 0.000 claims description 4
- KYVBNYUBXIEUFW-UHFFFAOYSA-N 1,1,3,3-tetramethylguanidine Chemical compound CN(C)C(=N)N(C)C KYVBNYUBXIEUFW-UHFFFAOYSA-N 0.000 claims description 3
- CTQNGGLPUBDAKN-UHFFFAOYSA-N O-Xylene Chemical compound CC1=CC=CC=C1C CTQNGGLPUBDAKN-UHFFFAOYSA-N 0.000 claims description 3
- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical compound CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 claims description 3
- BFXIKLCIZHOAAZ-UHFFFAOYSA-N methyltrimethoxysilane Chemical compound CO[Si](C)(OC)OC BFXIKLCIZHOAAZ-UHFFFAOYSA-N 0.000 claims description 3
- 238000010000 carbonizing Methods 0.000 claims description 2
- 239000000463 material Substances 0.000 abstract description 39
- FUJCRWPEOMXPAD-UHFFFAOYSA-N lithium oxide Chemical compound [Li+].[Li+].[O-2] FUJCRWPEOMXPAD-UHFFFAOYSA-N 0.000 abstract description 7
- 229910001947 lithium oxide Inorganic materials 0.000 abstract description 7
- 239000002994 raw material Substances 0.000 abstract description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical group [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 abstract description 2
- 239000002028 Biomass Substances 0.000 abstract 1
- 239000010406 cathode material Substances 0.000 abstract 1
- 230000000052 comparative effect Effects 0.000 description 15
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 12
- 238000012360 testing method Methods 0.000 description 12
- 238000001816 cooling Methods 0.000 description 10
- 238000010438 heat treatment Methods 0.000 description 10
- 239000007787 solid Substances 0.000 description 8
- 239000003792 electrolyte Substances 0.000 description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 6
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 6
- 238000001035 drying Methods 0.000 description 6
- 229910001416 lithium ion Inorganic materials 0.000 description 6
- 238000002791 soaking Methods 0.000 description 6
- 239000010405 anode material Substances 0.000 description 5
- 239000008367 deionised water Substances 0.000 description 5
- 229910021641 deionized water Inorganic materials 0.000 description 5
- 238000005406 washing Methods 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 239000007788 liquid Substances 0.000 description 4
- 239000002904 solvent Substances 0.000 description 4
- 238000010521 absorption reaction Methods 0.000 description 3
- 229910052786 argon Inorganic materials 0.000 description 3
- 239000003575 carbonaceous material Substances 0.000 description 3
- 239000011248 coating agent Substances 0.000 description 3
- 238000000576 coating method Methods 0.000 description 3
- 230000014759 maintenance of location Effects 0.000 description 3
- -1 polyethylene Polymers 0.000 description 3
- 230000000630 rising effect Effects 0.000 description 3
- 239000013589 supplement Substances 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- 101150058243 Lipf gene Proteins 0.000 description 2
- 239000004698 Polyethylene Substances 0.000 description 2
- 239000004743 Polypropylene Substances 0.000 description 2
- 239000012300 argon atmosphere Substances 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 239000011229 interlayer Substances 0.000 description 2
- 239000010410 layer Substances 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- WYTZZXDRDKSJID-UHFFFAOYSA-N (3-aminopropyl)triethoxysilane Chemical compound CCO[Si](OCC)(OCC)CCCN WYTZZXDRDKSJID-UHFFFAOYSA-N 0.000 description 1
- LZMNXXQIQIHFGC-UHFFFAOYSA-N 3-[dimethoxy(methyl)silyl]propyl 2-methylprop-2-enoate Chemical compound CO[Si](C)(OC)CCCOC(=O)C(C)=C LZMNXXQIQIHFGC-UHFFFAOYSA-N 0.000 description 1
- UUEWCQRISZBELL-UHFFFAOYSA-N 3-trimethoxysilylpropane-1-thiol Chemical compound CO[Si](OC)(OC)CCCS UUEWCQRISZBELL-UHFFFAOYSA-N 0.000 description 1
- XDLMVUHYZWKMMD-UHFFFAOYSA-N 3-trimethoxysilylpropyl 2-methylprop-2-enoate Chemical compound CO[Si](OC)(OC)CCCOC(=O)C(C)=C XDLMVUHYZWKMMD-UHFFFAOYSA-N 0.000 description 1
- 229910013870 LiPF 6 Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 150000001721 carbon Chemical class 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- NKSJNEHGWDZZQF-UHFFFAOYSA-N ethenyl(trimethoxy)silane Chemical compound CO[Si](OC)(OC)C=C NKSJNEHGWDZZQF-UHFFFAOYSA-N 0.000 description 1
- ZLNAFSPCNATQPQ-UHFFFAOYSA-N ethenyl-dimethoxy-methylsilane Chemical compound CO[Si](C)(OC)C=C ZLNAFSPCNATQPQ-UHFFFAOYSA-N 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 239000007770 graphite material Substances 0.000 description 1
- 238000009830 intercalation Methods 0.000 description 1
- 230000002687 intercalation Effects 0.000 description 1
- 230000002427 irreversible effect Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 239000007774 positive electrode material Substances 0.000 description 1
- 238000009656 pre-carbonization Methods 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000008096 xylene Substances 0.000 description 1
Classifications
-
- 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
-
- 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
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
-
- 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
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
-
- 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
-
- 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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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Inorganic Chemistry (AREA)
- Composite Materials (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The embodiment of the invention discloses a hard carbon composite material, which takes coconut shells as raw materials, a porous hard carbon precursor is prepared by mixing and pyrolyzing the coconut shells, a coupling agent, sodium bicarbonate and a catalyst, li 2 O powder and Ag powder are mixed and ball-milled to obtain a lithium supplementing additive, a suspension of the lithium supplementing additive and the porous hard carbon precursor are mixed, spray-dried and carbonized to obtain a soft carbon coated hard carbon composite material of the lithium supplementing additive. The hard carbon composite material prepared by the invention is used as a battery cathode material, and under the actions of sodium bicarbonate pyrolysis, a coupling agent, a catalyst and biomass, the hard carbon forms a material with high specific surface area, stable structure, high specific capacity and low impedance; the outer layer is coated with Li 2 O/Ag, lithium is supplemented on the surface of the material, the first efficiency of the material is improved, the electronic conductivity of lithium oxide is improved, the power performance is improved, and the performance of the material can be flexibly adjusted by adjusting the composition of a lithium supplementing additive and the proportion of the lithium supplementing additive to hard carbon.
Description
Technical Field
The invention belongs to the field of lithium ion batteries, and particularly relates to a hard carbon composite material and a preparation method and application thereof.
Background
Along with the improvement of the low-temperature and quick-charging requirements of the lithium ion battery, the lithium ion battery cathode is required to have high energy density, quick-charging and low-temperature performances. The theoretical specific capacity of the currently marketed graphite material is only 372Ah/g, and the low-temperature performance deviation can only meet the charging capacity of less than or equal to 4C, and cannot meet the requirements of high energy density, quick charge and low temperature in the future. The hard carbon material has the following characteristics: (1) isotropic structure, (2) large interlayer spacing; (3) small stress variation; (4) high lithium intercalation capacity; (5) high voltage plateau; the advantages enable the hard carbon to be used as the negative electrode material and have excellent low-temperature performance and rate capability; however, the high-temperature storage performance is poor, the specific capacity is low, the first efficiency is low, the exertion of the energy density is influenced, the specific capacity of the material can be improved through doping the material, the first efficiency of the material is still low (82%), the exertion of the gram capacity of the positive electrode material is reduced, and the energy density of the full battery cannot be improved.
Disclosure of Invention
In order to solve the defects in the prior art, the invention provides a hard carbon composite anode material which is prepared by coating porous hard carbon with soft carbon, and has higher first-time efficiency, energy density and excellent cycle performance.
In order to achieve the technical purpose, the invention adopts the following technical scheme:
the technical purpose of the first aspect of the invention is to provide a preparation method of a hard carbon composite material, which comprises the following steps:
Preparing a porous hard carbon precursor: the coconut shell is treated by acid and then dried, and is evenly mixed with an organic solvent solution of a coupling agent, sodium bicarbonate and a catalyst, spray-dried, pyrolyzed at 500-1300 ℃, and cooled to obtain a porous hard carbon precursor; wherein the catalyst is at least one selected from triethylamine, 4-dimethylaminopyridine, tetramethylguanidine and triethylenediamine;
Preparing a lithium supplementing additive: mixing Li 2 O powder and Ag powder according to the mass ratio of 2-5:1, and ball milling to obtain a Li 2 O/Ag lithium supplementing additive;
Preparation of the composite material: dispersing the lithium supplementing additive into a suspension with the mass concentration of 1% -10% by using an organic solvent, adding the prepared porous hard carbon precursor, uniformly stirring, spray-drying and carbonizing to obtain the soft carbon coated hard carbon composite material of the lithium supplementing additive.
In the preparation method, the mass ratio of the mixture of the coconut shell after the acid treatment, the coupling agent, the sodium bicarbonate and the catalyst is 100 (1-5): 0.5-2.
In the above preparation method, the coupling agent is at least one selected from vinyltriethoxysilane, methyltrimethoxysilane, tetraethoxysilane, vinyltrimethoxysilane, methylvinyldimethoxysilane, γ -methacryloxypropyl trimethoxysilane, methacryloxypropyl methyldimethoxysilane, γ -aminopropyl triethoxysilane, and γ -mercaptopropyl trimethoxysilane.
In the above preparation method, the organic solvent is at least one selected from carbon tetrachloride, N-methylpyrrolidone, xylene and cyclohexane.
In the above preparation method, the pyrolysis is heated to 500-1300 ℃ at a heating rate of 1-10 ℃/min, preferably to 700-1000 ℃ at a heating rate of 2-5 ℃/min.
In the above preparation method, the pyrolysis time is 1-6 hours.
In the preparation method, the acid treatment is to soak the coconut shells with an acid solution, wherein the acid solution is sulfuric acid or hydrochloric acid, the mass concentration of the acid solution is 10-30%, and the soaking time is 12-72h.
In the preparation method, the acid-treated dry drying is carried out at 80-140 ℃ for 1-48h.
In the above preparation method, the particle size of the Li 2 O powder and the Ag powder is 1-5:1, and the particle size of the Li 2 O powder is 0.5-2 μm.
In the above preparation method, the ball milling is performed at a speed of 100-1000 rpm for 1-24 hours.
In the preparation method, when the composite material is prepared, the lithium supplementing additive and the porous hard carbon precursor are mixed according to the mass ratio of 1-10:100.
In the preparation method, the carbonization is carried out for 1-6 hours at 800-1200 ℃ under inert atmosphere.
The technical object of the second aspect of the present invention is to provide a hard carbon composite material prepared by the above method.
The technical object of the third aspect of the present invention is to provide an application of the hard carbon composite material as a battery anode material.
The hard carbon composite material prepared by the invention has the advantages that sodium bicarbonate is added into the raw materials in the preparation process of the hard carbon, the sodium bicarbonate is decomposed in the pyrolysis process, nano and micron cavities are reserved for the hard carbon material, and the material is endowed with higher specific capacity; the coupling agent is adopted in the preparation process, and a reticular structure is formed in the material in the reaction process, so that the material has better structural stability, and the lithium supplement additive Li 2 O/Ag is coated on the outer layer, so that the material has higher first efficiency.
The implementation of the embodiment of the invention has the following beneficial effects:
(1) The hard carbon composite material is internally provided with hard carbon, the outer layer is lithium supplement additive Li 2 O/Ag, raw material sodium bicarbonate is added in the preparation process of the hard carbon, the hard carbon is decomposed in the pyrolysis process, nano and micron holes are left in the hard carbon, and a certain amount of holes are generated by the reaction of the raw materials under the catalysis of a catalyst, so that lithium storage active points of the material are improved, and the material has higher specific capacity; in addition, the coupling agent is added to form a net structure inside the material, so that the structural stability of the material is improved, and the porous hard carbon precursor material obtained through sintering has the advantages of high specific capacity, low impedance and the like.
(2) According to the composite anode material, the lithium supplement additive Li 2 O/Ag is coated on the surface of the hard carbon, lithium oxide reduces active points on the surface of the material, and lithium is supplemented on the surface of the material, so that the first efficiency of the material is improved, the improvement rate of the first efficiency is closely related to the amount of the coated lithium oxide, and meanwhile, the electronic conductivity of the lithium oxide is improved by adding the metal silver powder, and the power performance is improved; the performance of the material can be flexibly adjusted by adjusting the composition of the lithium supplementing additive and the proportion of the lithium supplementing additive to the hard carbon.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Wherein:
fig. 1 is an SEM image of the hard carbon composite material prepared in example 1.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Hard carbon composites were prepared in examples 1-3:
Example 1
S1, preparing a porous hard carbon precursor:
coconut shell: acid solution 10g: mixing 100mL, soaking the acid solution with sulfuric acid with the mass concentration of 20% for 24 hours, washing with deionized water, drying at 100 ℃ for 24 hours, and naturally cooling to room temperature; and then the coconut shell is treated by acid: vinyl triethoxysilane: sodium bicarbonate: placing triethylamine in carbon tetrachloride according to the mass ratio of 100:3:3:1, uniformly mixing, adding carbon tetrachloride solvent according to the proportion of 1 g/1 mL of carbon tetrachloride in the coconut shell subjected to acid treatment, and carrying out spray drying; and then pyrolyzing the dry solid at the temperature rising rate of 5 ℃/min at 800 ℃ for 3 hours, and naturally cooling the dry solid in a furnace to room temperature to obtain the porous hard carbon precursor.
S2, preparing a lithium supplementing additive:
Mixing Li 2 O powder and Ag powder according to a mass ratio of 3:1, and ball-milling for 12 hours at a speed of 500 revolutions per minute to obtain the lithium supplementing additive of Li 2 O/Ag.
S3, preparation of a composite material:
Adding a Li 2 O/Ag lithium supplementing additive into a carbon tetrachloride organic solvent to prepare a suspension with the mass concentration of Li 2 O/Ag of 5wt%, adding the porous hard carbon precursor prepared in the step S1 according to the mass ratio of Li 2 O/Ag to the porous hard carbon precursor of 5:100, uniformly stirring, spray-drying, and heating to 1000 ℃ in an argon inert atmosphere for carbonization for 3 hours to obtain the soft carbon coated hard carbon composite material.
Example 2
S1, preparing a porous hard carbon precursor:
Coconut shell: acid solution 10g: mixing 100mL, soaking the acid solution with sulfuric acid with the mass concentration of 10% for 72h, washing with deionized water, drying at 80 ℃ for 48h, and naturally cooling to room temperature; and then the coconut shell is treated by acid: methyltrimethoxysilane: sodium bicarbonate: placing the 4-dimethylaminopyridine in N-methylpyrrolidone according to the mass ratio of 100:1:1:0.5, and uniformly mixing, wherein the coconut shell is treated according to acid: n-methylpyrrolidone was added at a ratio of 1g to 1mL, and spray-dried; and then pyrolyzing the dried solid at the temperature rising rate of 1 ℃/min of 500 ℃ for 6 hours, and naturally cooling the dried solid in a furnace to room temperature to obtain the porous hard carbon precursor.
S2, preparing a lithium supplementing additive:
Mixing Li 2 O powder and Ag powder according to a mass ratio of 2:1, and ball-milling for 24 hours at a speed of 100 revolutions per minute to obtain the lithium supplementing additive of Li 2 O/Ag.
S3, preparation of a composite material:
Adding a Li 2 O/Ag lithium supplementing additive into an N-methylpyrrolidone organic solvent to prepare a suspension with the mass concentration of Li 2 O/Ag of 1wt%, adding the porous hard carbon precursor prepared in the step S1 according to the mass ratio of Li 2 O/Ag to the porous hard carbon precursor of 1:100, uniformly stirring, spray-drying, and heating to 800 ℃ in an inert argon atmosphere for carbonization for 6 hours to obtain the soft carbon coated hard carbon composite material.
Example 3
S1, preparing a porous hard carbon precursor:
Coconut shell: acid solution 10g: mixing 100mL, soaking the acid solution with sulfuric acid with the mass concentration of 30% for 12h, washing with deionized water, drying for 1h at 140 ℃, and naturally cooling to room temperature; and then the coconut shell is treated by acid: tetraethoxysilane: sodium bicarbonate: the tetramethylguanidine is placed in cyclohexane to be uniformly mixed according to the mass ratio of 100:5:5:2, wherein the coconut shell is treated according to acid: cyclohexane was added in a ratio of 1g to 1mL, and spray-dried; and then pyrolyzing the dried solid at 1300 ℃ at a heating rate of 10 ℃/min for 1h, and naturally cooling the dried solid to room temperature in a furnace to obtain the porous hard carbon precursor.
S2, preparing a lithium supplementing additive:
Mixing Li 2 O powder and Ag powder according to a mass ratio of 5:1, and ball-milling for 1h at a speed of 1000 revolutions per minute to obtain the lithium supplementing additive of Li 2 O/Ag.
S3, preparation of a composite material:
Adding a Li 2 O/Ag lithium supplementing additive into a cyclohexane organic solvent to prepare suspension with the mass concentration of Li 2 O/Ag of 10wt%, adding the porous hard carbon precursor prepared in the step S1 according to the mass ratio of Li 2 O/Ag to the porous hard carbon precursor of 10:100, uniformly stirring, spray-drying, and heating to 1200 ℃ in an inert argon atmosphere for carbonization for 1h to obtain the soft carbon coated hard carbon composite material.
Comparative example 1
The preparation procedure was the same as in S1 of example 1, to obtain a porous hard carbon material.
Comparative example 2
S1, step S1 of example 1
S2, adding 100g of the porous hard carbon precursor prepared in the embodiment 1 into a ball mill for ball milling, transferring into a tube furnace, heating to 200 ℃ for pre-carbonization for 1h, heating to 800 ℃ for carbonization for 3h, and crushing and grading to obtain the hard carbon composite material.
Comparative example 3
S1, preparing a hard carbon precursor:
Coconut shell: acid solution 10g: mixing 100mL, soaking the acid solution with sulfuric acid with the mass concentration of 30% for 24 hours, washing with deionized water, drying at 80 ℃ for 48 hours, and naturally cooling to room temperature; and then the coconut shell is treated by acid: the sodium bicarbonate is placed in N-methyl pyrrolidone according to the mass ratio of 100:1 and uniformly mixed, wherein the coconut shell is treated according to acid: n-methylpyrrolidone was added at a ratio of 1g to 1mL, and spray dried; then pyrolyzing for 6 hours at the heating rate of 500 ℃ at the speed of 1 ℃/min, and naturally cooling to room temperature in a furnace to prepare a hard carbon precursor;
S2, preparing a lithium supplementing additive:
Step S2 is the same as in example 2.
S3, preparation of a composite material:
the hard carbon is prepared by using the hard carbon precursor prepared in step S1 of this example, and the other steps are the same as in step S3 of example 2, to obtain a hard carbon composite material.
Comparative example 4
S1, preparing a hard carbon precursor:
coconut shell: acid solution 10g: mixing 100mL, soaking the acid solution with sulfuric acid with the mass concentration of 30% for 24 hours, washing with deionized water, drying at 100 ℃ for 24 hours, and naturally cooling to room temperature; and then the coconut shell is treated by acid: vinyl triethoxysilane: placing triethylamine in carbon tetrachloride according to the mass ratio of 100:3:1, uniformly mixing, adding carbon tetrachloride solvent according to the proportion of 1g carbon tetrachloride to 1mL of coconut shell subjected to acid treatment, and carrying out spray drying; and then pyrolyzing the dry solid at the temperature rising rate of 5 ℃/min at 800 ℃ for 3 hours, and naturally cooling the dry solid in a furnace to room temperature to prepare the hard carbon precursor.
S2, preparing a lithium supplementing additive:
Step S2 in example 1 is the same.
S3, preparation of a composite material:
The hard carbon is prepared by using the hard carbon precursor prepared in step S1 of this example, and the other operations are the same as in step S3 of example 1, to obtain a hard carbon composite material.
Comparative example 5
S1, preparing a hard carbon precursor:
Step S1 is the same as in example 1.
S2, preparing a composite material:
Adding Li 2 O powder into carbon tetrachloride organic solvent to prepare suspension with the mass concentration of Li 2 O of 5wt%, adding the hard carbon precursor prepared in S1 according to the mass ratio of Li 2 O to hard carbon precursor of 5:100, stirring uniformly, spray drying, and heating to 1000 ℃ under argon inert atmosphere for carbonization for 3 hours to obtain the hard carbon composite material.
Performance testing of the materials prepared in the above examples and comparative examples:
(1) SEM test
The composite material prepared in example 1 was subjected to SEM test, and the test results are shown in fig. 1.
As can be seen from FIG. 1, the hard carbon composite material prepared in example 1 is in the form of particles having a particle diameter D50 of between (5 and 10) μm.
(2) Physical and chemical properties and button cell testing
The composite materials prepared in examples 1 to 3 and comparative examples 1 to 5 were subjected to measurement of interlayer spacing (D002), specific surface area and tap density. The method is tested according to the national standard GBT-24533-2019 lithium ion battery graphite anode material. The test results are shown in Table 1.
The hard carbon composite materials in examples 1-3 and comparative examples 1-5 are used as negative electrode materials of lithium ion batteries to be assembled into button batteries, and the specific preparation method of the negative electrode materials is as follows: according to the hard carbon composite material: CMC: SBR: SP: mixing H 2 O with the mass ratio of 95:2.5:1.5:1:150 to prepare a negative plate; the lithium sheet is used as a positive electrode; the electrolyte adopts LiPF 6/EC+DEC, liPF 6 in the electrolyte is electrolyte, the mixture of EC and DEC with the volume ratio of 1:1 is solvent, and the electrolyte concentration is 1.3mol/L; the diaphragm adopts a composite film of polyethylene PE, polypropylene PP and polyethylene propylene PEP. The button cell assembly was performed in an argon filled glove box. Electrochemical performance was carried out on a wuhan blue electric CT2001A type battery tester, the charge-discharge voltage range was 0.00V to 2.0V, the charge-discharge rate was 0.1C, and the first discharge capacity and first efficiency of the button cell were tested. The test results are shown in Table 1.
TABLE 1
As can be seen from table 1, the hard carbon composite material of the embodiment is superior to the comparative example in tap density and specific surface area, and the reason is that the coating effect and the compactness of the material are improved by adopting the lithium oxide and the nano silver thereof, so that the binding force between the materials is improved, and the tap density of the material is improved. Meanwhile, the lithium oxide and the nano silver are coated on the surface of the material, so that the irreversible capacity of the material is reduced, the first efficiency and the impedance of the material are improved, and the gram capacity of the material is improved. Meanwhile, compared with comparative example 3, the coupling agent and the catalyst are added, the binding force between materials is improved by virtue of the effect of the coupling agent, the electric conductivity of powder is obviously improved, and meanwhile, the catalyst has a pore-forming effect, so that the specific capacity and the first efficiency of the materials are further improved. In example 1, sodium bicarbonate was added as compared with comparative example 4 to form a pore structure, the tap density was slightly reduced, the pore structure increased the lithium storage function, and the specific capacity and the first efficiency were improved. Example 1 increased silver powder compared to comparative example 5, increased the electron conductivity and tap density of the material, thereby increasing the activity of the material during charge and discharge, increasing gram capacity exertion of the material and its first efficiency.
(3) Soft package battery test:
The hard carbon composite materials in examples 1 to 3 and comparative examples 1 to 5 were subjected to slurry mixing and coating to prepare a negative electrode sheet, NCM622 was used as a positive electrode, EC/DEC/PC (volume ratio EC: DEC: PC=1:1:1) was used as a solvent, liPF 6 was used as an electrolyte, the concentration was 1.2mol/L, and Celgard2400 was used as a separator to prepare a 5Ah soft-pack battery.
The liquid absorption capacity and the liquid retention rate (24 h electrolyte amount/0 h electrolyte amount) of the negative plate are tested.
Testing the cycle performance: the charge and discharge current is 2.0C/2.0C, the voltage range is 2.5-4.2V, and the cycle number is 500.
Testing rate performance: and testing the constant current ratio of the soft package battery under the initial cycle DCR and 2C charging conditions.
The test results are shown in Table 2.
TABLE 2
As can be seen from Table 2, the liquid absorption and retention capacities of the negative electrode sheets in examples 1 to 3 are significantly better than those in comparative examples 1,2 and 4, and the analysis is that: sodium bicarbonate is added when the hard carbon anode material is prepared, and the prepared material has high specific surface area and improves the liquid absorption and retention capacity of the material. Compared with comparative examples 1,2 and 5, the batteries prepared by the materials of examples 1-3 have the advantages that the surfaces of the batteries are coated with Li 2 O/Ag, lithium oxide provides sufficient lithium ions for the charge and discharge processes, the cycle performance of the batteries is improved, and the impedance of the batteries is reduced; the material is doped and coated with the conductive high-nano silver, so that the impedance of the material is further reduced, and the charging constant current ratio of the material is improved.
The foregoing disclosure is illustrative of the present invention and is not to be construed as limiting the scope of the invention, which is defined by the appended claims.
Claims (6)
1. A preparation method of a hard carbon composite material comprises the following steps:
Preparing a porous hard carbon precursor: the coconut shell is treated by acid and then dried, and is evenly mixed with an organic solvent solution of a coupling agent, sodium bicarbonate and a catalyst, spray-dried, pyrolyzed at 500-1300 ℃, and cooled to obtain a porous hard carbon precursor; wherein the catalyst is at least one selected from triethylamine, 4-dimethylaminopyridine, tetramethylguanidine and triethylenediamine;
Preparing a lithium supplementing additive: mixing Li 2 O powder and Ag powder according to the mass ratio of 2-5:1, and ball milling to obtain a Li 2 O/Ag lithium supplementing additive;
Preparation of the composite material: dispersing the lithium supplementing additive into a suspension with the mass concentration of 1% -10% by using an organic solvent, adding the prepared porous hard carbon precursor, uniformly stirring, spray-drying and carbonizing to obtain a soft carbon coated hard carbon composite material of the lithium supplementing additive;
the coupling agent is at least one of vinyl triethoxysilane, methyl trimethoxy silane and tetraethoxysilane;
The organic solvent is at least one selected from carbon tetrachloride, N-methyl pyrrolidone, dimethylbenzene and cyclohexane;
When the composite material is prepared, the lithium supplementing additive and the porous hard carbon precursor are mixed according to the mass ratio of 1-10:100;
the carbonization is carried out for 1-6 hours at 800-1200 ℃ under inert atmosphere.
2. The preparation method according to claim 1, wherein the mass ratio of the mixture of the coconut shell after the acid treatment, the coupling agent, the sodium bicarbonate and the catalyst is 100:1-5:1-5:0.5-2.
3. The method of claim 1, wherein the pyrolysis is performed at a rate of 1-10 ℃/min to 500-1300 ℃.
4. The method according to claim 1, wherein the mass ratio of the Li 2 O powder to the Ag powder is 2 to 5:1, and the particle size of the Li 2 O powder is 0.5 to 2 μm.
5. A hard carbon composite material prepared by the method of any one of claims 1-4.
6. The use of the hard carbon composite material of claim 5 as a battery negative electrode material.
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