CN114843483A - 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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- CN114843483A CN114843483A CN202210567487.6A CN202210567487A CN114843483A CN 114843483 A CN114843483 A CN 114843483A CN 202210567487 A CN202210567487 A CN 202210567487A CN 114843483 A CN114843483 A CN 114843483A
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- 229910021385 hard carbon Inorganic materials 0.000 title claims abstract description 79
- 239000002131 composite material Substances 0.000 title claims abstract description 44
- 238000002360 preparation method Methods 0.000 title claims description 26
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 34
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 34
- 238000002156 mixing Methods 0.000 claims abstract description 34
- 239000007833 carbon precursor Substances 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
- 239000000654 additive Substances 0.000 claims abstract description 30
- 230000000996 additive effect Effects 0.000 claims abstract description 30
- 239000013589 supplement Substances 0.000 claims abstract description 29
- 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
- 229910000030 sodium bicarbonate Inorganic materials 0.000 claims abstract description 15
- 235000017557 sodium bicarbonate Nutrition 0.000 claims abstract description 15
- 238000001694 spray drying Methods 0.000 claims abstract description 14
- 239000003054 catalyst Substances 0.000 claims abstract description 12
- 239000007822 coupling agent Substances 0.000 claims abstract description 12
- 238000000498 ball milling Methods 0.000 claims abstract description 8
- 239000000203 mixture Substances 0.000 claims abstract description 7
- 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
- 238000010000 carbonizing Methods 0.000 claims abstract description 3
- VZGDMQKNWNREIO-UHFFFAOYSA-N tetrachloromethane Chemical compound ClC(Cl)(Cl)Cl VZGDMQKNWNREIO-UHFFFAOYSA-N 0.000 claims description 20
- 239000002253 acid Substances 0.000 claims description 18
- ZMANZCXQSJIPKH-UHFFFAOYSA-N Triethylamine Chemical compound CCN(CC)CC ZMANZCXQSJIPKH-UHFFFAOYSA-N 0.000 claims description 12
- 238000000034 method Methods 0.000 claims description 10
- 238000001035 drying Methods 0.000 claims description 9
- 239000003960 organic solvent Substances 0.000 claims description 8
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 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
- 239000007773 negative electrode material Substances 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
- FWDBOZPQNFPOLF-UHFFFAOYSA-N ethenyl(triethoxy)silane Chemical compound CCO[Si](OCC)(OCC)C=C FWDBOZPQNFPOLF-UHFFFAOYSA-N 0.000 claims description 4
- 238000004519 manufacturing process Methods 0.000 claims description 4
- 239000002245 particle 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
- 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
- WYTZZXDRDKSJID-UHFFFAOYSA-N (3-aminopropyl)triethoxysilane Chemical compound CCO[Si](OCC)(OCC)CCCN WYTZZXDRDKSJID-UHFFFAOYSA-N 0.000 claims description 2
- 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 claims description 2
- UUEWCQRISZBELL-UHFFFAOYSA-N 3-trimethoxysilylpropane-1-thiol Chemical compound CO[Si](OC)(OC)CCCS UUEWCQRISZBELL-UHFFFAOYSA-N 0.000 claims description 2
- 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 claims description 2
- CTQNGGLPUBDAKN-UHFFFAOYSA-N O-Xylene Chemical compound CC1=CC=CC=C1C CTQNGGLPUBDAKN-UHFFFAOYSA-N 0.000 claims description 2
- NKSJNEHGWDZZQF-UHFFFAOYSA-N ethenyl(trimethoxy)silane Chemical compound CO[Si](OC)(OC)C=C NKSJNEHGWDZZQF-UHFFFAOYSA-N 0.000 claims description 2
- ZLNAFSPCNATQPQ-UHFFFAOYSA-N ethenyl-dimethoxy-methylsilane Chemical compound CO[Si](C)(OC)C=C ZLNAFSPCNATQPQ-UHFFFAOYSA-N 0.000 claims description 2
- 239000008096 xylene Substances 0.000 claims description 2
- 239000000463 material Substances 0.000 abstract description 59
- 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
- 229910018068 Li 2 O Inorganic materials 0.000 abstract description 6
- 239000010406 cathode material Substances 0.000 abstract description 4
- 239000002994 raw material Substances 0.000 abstract description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical group [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 abstract description 2
- 230000009471 action Effects 0.000 abstract description 2
- 239000002028 Biomass 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
- 238000010306 acid treatment Methods 0.000 description 11
- 238000010438 heat treatment Methods 0.000 description 11
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 10
- 238000001816 cooling Methods 0.000 description 10
- 239000003792 electrolyte Substances 0.000 description 7
- 239000007787 solid Substances 0.000 description 7
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 6
- 229910001416 lithium ion Inorganic materials 0.000 description 6
- 238000002791 soaking Methods 0.000 description 6
- 229910052786 argon Inorganic materials 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
- 238000007599 discharging Methods 0.000 description 4
- 239000002904 solvent Substances 0.000 description 4
- -1 Polyethylene Polymers 0.000 description 3
- 239000003575 carbonaceous material Substances 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 238000003860 storage Methods 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- 229910013872 LiPF Inorganic materials 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
- 238000006243 chemical reaction Methods 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 230000004907 flux Effects 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 239000011229 interlayer Substances 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 229920000573 polyethylene Polymers 0.000 description 2
- 229920001155 polypropylene Polymers 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 229910013870 LiPF 6 Inorganic materials 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000010405 anode material Substances 0.000 description 1
- 239000010426 asphalt Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 150000001721 carbon Chemical class 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000001739 density measurement Methods 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 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
- 239000010410 layer Substances 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000003208 petroleum 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
Images
Classifications
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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
-
- 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
Abstract
The embodiment of the invention discloses a hard carbon composite material, which takes coconut shells as raw materials, prepares a porous hard carbon precursor by mixing and pyrolyzing the coconut shells, a coupling agent, sodium bicarbonate and a catalyst, and prepares Li 2 Mixing O powder and Ag powder, ball-milling to obtain a lithium supplement additive, mixing the suspension of the lithium supplement additive with the porous hard carbon precursor, spray-drying, and carbonizing to obtain the soft carbon-coated hard carbon composite material of the lithium supplement additive. The hard carbon composite material prepared by the invention is used as a battery cathode material, and the hard carbon forms a material with high specific surface area and stable structure under the action of sodium bicarbonate pyrolysis, a coupling agent, a catalyst and biomass, and has high specific capacity and low impedance; outer layer coated with Li 2 O/Ag, surface repairingLithium, the first-time 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 the lithium supplement additive and the proportion of the lithium supplement 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
With the improvement of the lithium ion battery in low temperature and fast charge requirements, the lithium ion battery cathode is required to have high energy density, fast charge and low temperature performance. The theoretical specific capacity of the graphite material on the market at present is only 372Ah/g, and the low-temperature performance deviation can only meet the charging capacity of less than or equal to 4C, and can not meet the requirements of high energy density, quick charging and low temperature in the future. The hard carbon material has the following characteristics: (1) isotropic structure, (2) the interlayer spacing is larger; (3) the stress change is small; (4) the lithium intercalation capacity is high; (5) the voltage platform is high; the advantages enable the hard carbon as the cathode material to have excellent low-temperature performance and rate capability; but the high-temperature storage performance, specific capacity and first efficiency of the material are poor, the exertion of the energy density is influenced, although the specific capacity of the material can be improved by doping the material, the first efficiency of the material is still low (82%), the gram capacity exertion of the anode material is reduced, and the energy density of the full battery cannot be improved.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention provides the hard carbon composite negative electrode material which adopts soft carbon to coat porous hard carbon and has higher first efficiency, energy density and excellent cycle performance.
In order to achieve the technical purpose, the technical scheme adopted by the invention is as follows:
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: treating coconut shells with acid, drying, uniformly mixing with an organic solvent solution of a coupling agent, sodium bicarbonate and a catalyst, spray-drying, pyrolyzing at 1300 ℃ of 500-; wherein the catalyst is selected from at least one of triethylamine, 4-dimethylamino pyridine, tetramethyl guanidine and triethylene diamine;
preparing a lithium supplement additive: mixing Li 2 Mixing O powder and Ag powder according to the mass ratio of 2-5:1, and performing ball milling to obtain Li 2 Lithium supplement additive of O/Ag;
preparing a composite material: dispersing the lithium supplement additive into 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 supplement additive.
In the preparation method, the weight ratio of the coconut shell after acid treatment, the coupling agent, the sodium bicarbonate and the catalyst is 100 (1-5) to (0.5-2).
In the above preparation method, the coupling agent is at least one selected from the group consisting of vinyltriethoxysilane, methyltrimethoxysilane, tetraethoxysilane, vinyltrimethoxysilane, methylvinyldimethoxysilane, gamma-methacryloxypropyltrimethoxysilane, methacryloxypropylmethyldimethoxysilane, gamma-aminopropyltriethoxysilane, and gamma-mercaptopropyltrimethoxysilane.
In the above production method, the organic solvent is at least one selected from the group consisting of 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 preparation method, the pyrolysis time is 1-6 h.
In the preparation method, the acid treatment is to soak the coconut shells by using 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 12-72 h.
In the preparation method, the dry drying after the acid treatment is drying for 1-48h at the temperature of 80-140 ℃.
In the above production method, the Li 2 The grain diameter of O powder and Ag powder is 1-5:1, Li 2 The particle size of the O powder is 0.5-2 μm.
In the preparation method, the ball milling is carried out at the speed of 100-.
In the preparation method, when the composite material is prepared, the lithium supplement 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 1-6h at 800-1200 ℃ under inert atmosphere.
It is a technical object of the second aspect of the present invention to provide a hard carbon composite material prepared by the above method.
The technical purpose of the third aspect of the invention is to provide the application of the hard carbon composite material as a battery negative electrode material.
According to the hard carbon composite material prepared by the invention, sodium bicarbonate is added into the raw material of the internal hard carbon during preparation, and the internal hard carbon is decomposed during pyrolysis to leave nano and micron cavities for the hard carbon material, so that the material is endowed with higher specific capacity; the coupling agent is adopted in the preparation process, a net structure is formed in the material in the reaction process, so that the material has better structural stability, and the outer layer is coated with the lithium supplement additive Li 2 O/Ag, so that the catalyst has higher first efficiency.
The embodiment of the invention has the following beneficial effects:
(1) the hard carbon composite material of the invention has hard carbon inside and lithium supplement additive Li outside 2 O/Ag, the raw material sodium bicarbonate is added in the preparation process of the hard carbon, the sodium bicarbonate is decomposed in the pyrolysis process, nano and micro holes are left in the hard carbon, and under the catalytic action of a catalyst, a certain amount of holes are generated by the reaction of the raw materials, so that the lithium storage active points of the material are improved, and the material has higher specific capacity; in addition, the addition of the coupling agent enables the interior of the material to form a net-shaped structure, 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) The composite cathode material of the invention coats the lithium supplement additive Li on the surface of hard carbon 2 O/Ag, the lithium oxide reduces active points on the surface of the material, lithium is supplemented on the surface of the material, 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 metal silver powder is added to improve the electronic conductivity of the lithium oxide and improve the power performance; the performance of the material can be flexibly adjusted by adjusting the composition of the lithium supplement additive and the proportion of the lithium supplement additive to the hard carbon.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Wherein:
fig. 1 is an SEM image of a hard carbon composite prepared in example 1.
Detailed Description
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, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Hard carbon composites were prepared in examples 1-3:
example 1
S1, preparing a porous hard carbon precursor:
mixing coconut shells: acid solution 10 g: mixing the materials in a proportion of 100mL, soaking the materials in an acid solution which is sulfuric acid with the mass concentration of 20% for 24 hours, washing the materials with deionized water, drying the materials for 24 hours at the temperature of 100 ℃, and naturally cooling the materials to room temperature; then, according to the coconut shell after acid treatment: vinyltriethoxysilane: sodium bicarbonate: placing triethylamine in carbon tetrachloride in a mass ratio of 100:3:3:1, uniformly mixing, wherein a carbon tetrachloride solvent is added according to a ratio of 1g to 1mL of acid-treated coconut shell to carbon tetrachloride, and performing spray drying; and then pyrolyzing the dried solid for 3h at the temperature rise rate of 800 ℃ at 5 ℃/min, and naturally cooling the dried solid in a furnace to room temperature to obtain the porous hard carbon precursor.
S2, preparing a lithium supplement additive:
mixing Li 2 Mixing O powder and Ag powder according to the mass ratio of 3:1, and ball-milling for 12 hours at the speed of 500 revolutions per minute to obtain Li 2 O/Ag lithium supplement additive.
S3, preparation of the composite material:
mixing Li 2 O/Ag lithium supplement additiveAdding into carbon tetrachloride organic solvent to prepare Li 2 Suspension with a mass concentration of O/Ag of 5 wt%, then according to Li 2 Adding the porous hard carbon precursor prepared in S1 into O/Ag and the porous hard carbon precursor in a mass ratio of 5:100, uniformly stirring, spray-drying, and then heating to 1000 ℃ for carbonization for 3h under an argon inert atmosphere to obtain the soft carbon-coated hard carbon composite material.
Example 2
S1, preparing a porous hard carbon precursor:
mixing coconut shells: acid solution 10 g: mixing the materials in a proportion of 100mL, soaking the materials for 72h in an acid solution which is sulfuric acid with the mass concentration of 10%, washing the materials with deionized water, drying the materials for 48h at the temperature of 80 ℃, and naturally cooling the materials to room temperature; then, according to the coconut shell after acid treatment: methyltrimethoxysilane: sodium bicarbonate: the 4-dimethylamino pyridine is placed into N-methyl pyrrolidone to be uniformly mixed according to the mass ratio of 100:1:1:0.5, wherein the weight ratio of coconut shells after acid treatment is as follows: adding N-methyl pyrrolidone in a ratio of 1g to 1mL, and performing spray drying; and then pyrolyzing the dried solid for 6h at the heating rate of 1 ℃/min of 500 ℃, and naturally cooling to room temperature in the furnace to obtain the porous hard carbon precursor.
S2, preparing a lithium supplement additive:
mixing Li 2 Mixing O powder and Ag powder according to the mass ratio of 2:1, and ball-milling for 24 hours at the speed of 100 revolutions per minute to obtain Li 2 O/Ag lithium supplement additive.
S3, preparation of the composite material:
mixing Li 2 Adding O/Ag lithium-supplementing additive into N-methyl pyrrolidone organic flux to prepare Li 2 Suspension with a mass concentration of O/Ag of 1 wt%, then according to Li 2 Adding the porous hard carbon precursor prepared in S1 into O/Ag and the porous hard carbon precursor in a mass ratio of 1:100, uniformly stirring, spray-drying, and then heating to 800 ℃ for carbonization for 6 hours under an argon inert atmosphere to obtain the soft carbon-coated hard carbon composite material.
Example 3
S1, preparing a porous hard carbon precursor:
mixing coconut shells: acid solution 10 g: mixing 100mL of the components, soaking the components in an acid solution which is sulfuric acid with the mass concentration of 30% for 12 hours, washing the components with deionized water, drying the components for 1 hour at the temperature of 140 ℃, and naturally cooling the components to room temperature; then, according to the coconut shell after acid treatment: tetraethoxysilane: sodium bicarbonate: placing the tetramethylguanidine into cyclohexane in a mass ratio of 100:5:5:2, and uniformly mixing, wherein the weight ratio of the coconut shell after acid treatment is as follows: adding cyclohexane in a ratio of 1g to 1mL, and performing spray drying; and then, pyrolyzing the dried solid for 1h at the heating rate of 1300 ℃ at 10 ℃/min, and naturally cooling the dried solid in a furnace to room temperature to obtain the porous hard carbon precursor.
S2, preparing a lithium supplement additive:
mixing Li 2 Mixing O powder and Ag powder according to the mass ratio of 5:1, and ball-milling for 1h at the speed of 1000 r/min to obtain Li 2 O/Ag lithium supplement additive.
S3, preparation of the composite material:
mixing Li 2 Adding O/Ag lithium-supplementing additive into cyclohexane organic flux to prepare Li 2 Suspension with a mass concentration of O/Ag of 10 wt%, then according to Li 2 Adding the porous hard carbon precursor prepared in S1 into the mixture with the mass ratio of O/Ag to the porous hard carbon precursor of 10:100, uniformly stirring, spray-drying, and then heating to 1200 ℃ for carbonization for 1h under the inert atmosphere of argon 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, same as step S1 of example 1
S2, adding 100g of the porous hard carbon precursor prepared in the embodiment 1 and 5g of petroleum asphalt into a ball mill for ball milling, transferring the mixture into a tube furnace, firstly heating to 200 ℃ for pre-carbonization for 1h, then heating to 800 ℃ for carbonization for 3h, and crushing and grading to obtain the hard carbon composite material.
Comparative example 3
S1, preparation of hard carbon precursor:
mixing coconut shells: acid solution 10 g: mixing the materials in a proportion of 100mL, soaking the materials in an acid solution which is sulfuric acid with the mass concentration of 30% for 24 hours, washing the materials with deionized water, drying the materials for 48 hours at the temperature of 80 ℃, and naturally cooling the materials to room temperature; then, according to the coconut shell after acid treatment: and (2) placing the sodium bicarbonate into N-methyl pyrrolidone according to the mass ratio of 100:1, and uniformly mixing, wherein the weight ratio of the coconut shell after acid treatment is as follows: adding N-methyl pyrrolidone in a proportion of 1g to 1mL, and spray drying; then pyrolyzing for 6h at the heating rate of 1 ℃/min of 500 ℃, and naturally cooling to the room temperature in the furnace to prepare a hard carbon precursor;
s2, preparing a lithium supplement additive:
the same as step S2 in example 2.
S3, preparation of the composite material:
hard carbon using the hard carbon precursor prepared in step S1 of this example, a hard carbon composite material was obtained in the same manner as in step S3 of example 2.
Comparative example 4
S1, preparing a hard carbon precursor:
mixing coconut shells: acid solution 10 g: mixing the materials in a proportion of 100mL, soaking the materials in an acid solution which is sulfuric acid with the mass concentration of 30% for 24 hours, washing the materials with deionized water, drying the materials for 24 hours at the temperature of 100 ℃, and naturally cooling the materials to room temperature; then according to the coconut shell after acid treatment: vinyltriethoxysilane: placing triethylamine in carbon tetrachloride in a mass ratio of 100:3:1, and uniformly mixing, wherein a carbon tetrachloride solvent is added according to a ratio of 1g to 1mL of acid-treated coconut shell to carbon tetrachloride, and spray drying is carried out; and then pyrolyzing the dried solid for 3h at the temperature rise rate of 800 ℃ at 5 ℃/min, and naturally cooling the dried solid in a furnace to room temperature to obtain the hard carbon precursor.
S2, preparing a lithium supplement additive:
the same as step S2 in example 1.
S3, preparing the composite material:
hard carbon using the hard carbon precursor prepared in step S1 of this example, a hard carbon composite material was obtained in the same manner as in step S3 of example 1.
Comparative example 5
S1, preparing a hard carbon precursor:
the same as step S1 in example 1.
S2, preparing a composite material:
mixing Li 2 Adding O powder into carbon tetrachloride organic solvent to prepare Li 2 A suspension with an O mass concentration of 5 wt.%, after which according to Li 2 Adding the hard carbon precursor prepared in S1 into the mixture with the mass ratio of O to the hard carbon precursor of 5:100, uniformly stirring, spray-drying, and then heating to 1000 ℃ for carbonization for 3h under the inert atmosphere of argon 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 was in the form of particles having a particle size D50 of (5-10) μm.
(2) Physicochemical Properties and button cell test
The composite materials prepared in examples 1 to 3 and comparative examples 1 to 5 were subjected to interlayer spacing (D002), specific surface area, and tap density measurement. Testing according to the method of national standard GBT-2433and 2019 graphite cathode material for lithium ion batteries. The test results are shown in table 1.
The hard carbon composite materials in the examples 1-3 and the comparative examples 1-5 are used as the negative electrode materials of the lithium ion batteries to assemble the button batteries, and the specific preparation method of the negative electrode materials comprises the following steps: according to the weight percentage of the hard carbon composite material: CMC: SBR: SP: h 2 Mixing the materials according to the mass ratio of 95:2.5:1.5:1:150 to prepare a negative plate; a lithium sheet is used as a positive electrode; LiPF is adopted as electrolyte 6 EC + DEC, LiPF in electrolyte 6 The electrolyte is a mixture of EC and DEC with the volume ratio of 1:1 as a solvent, and the electrolyte concentration is 1.3 mol/L; the diaphragm adopts a composite film of Polyethylene (PE), polypropylene (PP) and polyethylene propylene (PEP). Button cell assembly was performed in an argon-filled glove box. The electrochemical performance is carried out on a Wuhan blue electricity CT2001A type battery tester, the charging and discharging voltage range is 0.00V to 2.0V, the charging and discharging rate is 0.1C, and the first discharging capacity and the first efficiency of the button cell are tested. The test results are shown in table 1.
TABLE 1
As can be seen from table 1, the tap density and the specific surface area of the hard carbon composite material in the examples are superior to those of the comparative examples in that the lithium oxide and the nano silver thereof are used for coating to improve the coating effect and the density of the material, thereby improving the binding force between the materials and improving the tap density of the material. Meanwhile, the lithium oxide and the nano silver are coated on the surface, so that the irreversible capacity of the material is reduced, the first efficiency of the material is improved, the impedance is reduced, and the gram capacity exertion of the material is improved. Meanwhile, compared with the comparative example 3, the embodiment 2 has the advantages that the coupling agent and the catalyst are added, the bonding force between the materials is improved under the action of the coupling agent, the powder conductivity 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. Compared with the comparative example 4, the embodiment 1 adds the sodium bicarbonate to form a pore structure, the tap density is slightly reduced, the pore structure increases the lithium storage function, and the specific capacity and the first efficiency are improved. Compared with the comparative example 5, the silver powder is added in the example 1, so that the electronic conductivity and tap density of the material are improved, the activity of the material in the charge and discharge process is improved, the gram capacity exertion of the material is improved, and the first efficiency of the material is improved.
(3) Testing the soft package battery:
the hard carbon composite materials in examples 1 to 3 and comparative examples 1 to 5 were combined and coated to prepare a negative electrode sheet, the NCM622 was used as a positive electrode, the solvent was EC/DEC/PC (volume ratio EC: DEC: PC: 1:1), the electrolyte was used, and the solute was LiPF 6 And the concentration is 1.2mol/L, a Celgard2400 membrane is used as a diaphragm, and the 5Ah flexible package battery is prepared.
The negative electrode sheet was tested for liquid-absorbing capacity and liquid-retaining rate (24h electrolyte amount/0 h electrolyte amount).
Testing the cycle performance: the charging and discharging current is 2.0C/2.0C, the voltage range is 2.5-4.2V, and the cycle times are 500 times.
Testing rate performance: the pouch cells were tested for initial cycle DCR, constant current ratio under 2C charging conditions.
The test results are shown in table 2.
TABLE 2
As can be seen from table 2, the liquid absorbing and retaining capabilities of the negative electrode sheets in examples 1 to 3 are significantly better than those of comparative examples 1, 2 and 4, and the reason for the analysis is that: the sodium bicarbonate is added when the hard carbon negative electrode material is prepared, and the prepared material has a high specific surface area and improves the liquid absorption and retention capacity of the material. In comparison with comparative examples 1, 2 and 5, the batteries prepared from the materials of examples 1 to 3 were coated with Li on the surfaces thereof 2 O/Ag, lithium oxide provides sufficient lithium ions for the charge and discharge process, improves the cycle performance and reduces the impedance; the material is doped and coated with 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 above disclosure is only for the purpose of illustrating the preferred embodiments of the present invention, and it is therefore to be understood that the invention is not limited by the scope of the appended claims.
Claims (10)
1. A preparation method of a hard carbon composite material comprises the following steps:
preparing a porous hard carbon precursor: treating coconut shells with acid, drying, uniformly mixing with an organic solvent solution of a coupling agent, sodium bicarbonate and a catalyst, spray-drying, pyrolyzing at 1300 ℃ of 500-; wherein the catalyst is selected from at least one of triethylamine, 4-dimethylamino pyridine, tetramethyl guanidine and triethylene diamine;
preparing a lithium supplement additive: mixing Li 2 Mixing O powder and Ag powder according to the mass ratio of 2-5:1, and performing ball milling to obtain Li 2 Lithium supplement additive of O/Ag;
preparing a composite material: dispersing the lithium supplement additive into 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 supplement additive.
2. The preparation method according to claim 1, wherein the weight ratio of the mixture of the acid-treated coconut shell, the coupling agent, the sodium bicarbonate and the catalyst is 100:1-5:1-5: 0.5-2.
3. The method according to claim 1, wherein the coupling agent is at least one member selected from the group consisting of vinyltriethoxysilane, methyltrimethoxysilane, tetraethoxysilane, vinyltrimethoxysilane, methylvinyldimethoxysilane, gamma-methacryloxypropyltrimethoxysilane, methacryloxypropylmethyldimethoxysilane, gamma-aminopropyltriethoxysilane, and gamma-mercaptopropyltrimethoxysilane.
4. The production method according to claim 1, wherein the organic solvent is at least one selected from the group consisting of carbon tetrachloride, N-methylpyrrolidone, xylene, and cyclohexane.
5. The method as claimed in claim 1, wherein the pyrolysis is carried out at a temperature rise rate of 1-10 ℃/min to 500-1300 ℃.
6. The production method according to claim 1, wherein the Li is 2 The grain diameter of O powder and Ag powder is 1-5:1, Li 2 The particle size of the O powder is 0.5-2 μm.
7. The preparation method according to claim 1, wherein the lithium supplement additive is mixed with the porous hard carbon precursor in a mass ratio of 1-10:100 when preparing the composite material.
8. The method as claimed in claim 1, wherein the carbonization is carried out at 800-1200 ℃ for 1-6h under an inert atmosphere.
9. A hard carbon composite prepared by the method of any one of claims 1 to 8.
10. Use of the hard carbon composite of claim 9 as a battery negative electrode material.
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