CN110611078B - Lithium titanate-carbon nanotube composite material and preparation method thereof - Google Patents
Lithium titanate-carbon nanotube composite material and preparation method thereof Download PDFInfo
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- CN110611078B CN110611078B CN201810615416.2A CN201810615416A CN110611078B CN 110611078 B CN110611078 B CN 110611078B CN 201810615416 A CN201810615416 A CN 201810615416A CN 110611078 B CN110611078 B CN 110611078B
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- 239000002041 carbon nanotube Substances 0.000 title claims abstract description 79
- 229910021393 carbon nanotube Inorganic materials 0.000 title claims abstract description 77
- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 72
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 71
- 238000002360 preparation method Methods 0.000 title claims abstract description 14
- 239000002131 composite material Substances 0.000 title description 7
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 44
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims abstract description 35
- 239000007772 electrode material Substances 0.000 claims abstract description 25
- 239000000203 mixture Substances 0.000 claims abstract description 20
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- 238000002156 mixing Methods 0.000 claims abstract description 7
- 238000003756 stirring Methods 0.000 claims abstract description 7
- 150000002642 lithium compounds Chemical class 0.000 claims abstract description 6
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- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims abstract description 4
- 238000006116 polymerization reaction Methods 0.000 claims abstract description 4
- 239000011268 mixed slurry Substances 0.000 claims abstract description 3
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 claims description 24
- 238000000034 method Methods 0.000 claims description 17
- VXUYXOFXAQZZMF-UHFFFAOYSA-N titanium(IV) isopropoxide Chemical compound CC(C)O[Ti](OC(C)C)(OC(C)C)OC(C)C VXUYXOFXAQZZMF-UHFFFAOYSA-N 0.000 claims description 7
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 6
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- 239000002904 solvent Substances 0.000 claims description 6
- 238000006243 chemical reaction Methods 0.000 claims description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 4
- 150000001298 alcohols Chemical class 0.000 claims description 4
- 150000001299 aldehydes Chemical class 0.000 claims description 4
- 150000001408 amides Chemical class 0.000 claims description 4
- 150000001412 amines Chemical class 0.000 claims description 4
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- 229930195733 hydrocarbon Natural products 0.000 claims description 4
- 150000002430 hydrocarbons Chemical class 0.000 claims description 4
- 150000002576 ketones Chemical class 0.000 claims description 4
- 239000007788 liquid Substances 0.000 claims description 4
- -1 n-propyl titanate Chemical compound 0.000 claims description 4
- 239000010936 titanium Substances 0.000 claims description 4
- 239000011261 inert gas Substances 0.000 claims description 3
- 229910052757 nitrogen Inorganic materials 0.000 claims description 3
- DNIAPMSPPWPWGF-VKHMYHEASA-N (+)-propylene glycol Chemical compound C[C@H](O)CO DNIAPMSPPWPWGF-VKHMYHEASA-N 0.000 claims description 2
- DNIAPMSPPWPWGF-GSVOUGTGSA-N (R)-(-)-Propylene glycol Chemical compound C[C@@H](O)CO DNIAPMSPPWPWGF-GSVOUGTGSA-N 0.000 claims description 2
- YPFDHNVEDLHUCE-UHFFFAOYSA-N 1,3-propanediol Substances OCCCO YPFDHNVEDLHUCE-UHFFFAOYSA-N 0.000 claims description 2
- 229940035437 1,3-propanediol Drugs 0.000 claims description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-M Bicarbonate Chemical compound OC([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-M 0.000 claims description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 claims description 2
- 229910052786 argon Inorganic materials 0.000 claims description 2
- FPCJKVGGYOAWIZ-UHFFFAOYSA-N butan-1-ol;titanium Chemical compound [Ti].CCCCO.CCCCO.CCCCO.CCCCO FPCJKVGGYOAWIZ-UHFFFAOYSA-N 0.000 claims description 2
- 150000007942 carboxylates Chemical class 0.000 claims description 2
- 239000001307 helium Substances 0.000 claims description 2
- 229910052734 helium Inorganic materials 0.000 claims description 2
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 claims description 2
- DNIAPMSPPWPWGF-UHFFFAOYSA-N monopropylene glycol Natural products CC(O)CO DNIAPMSPPWPWGF-UHFFFAOYSA-N 0.000 claims description 2
- 229910052754 neon Inorganic materials 0.000 claims description 2
- GKAOGPIIYCISHV-UHFFFAOYSA-N neon atom Chemical compound [Ne] GKAOGPIIYCISHV-UHFFFAOYSA-N 0.000 claims description 2
- 229920000166 polytrimethylene carbonate Polymers 0.000 claims description 2
- 229960004063 propylene glycol Drugs 0.000 claims description 2
- 235000013772 propylene glycol Nutrition 0.000 claims description 2
- 229910052719 titanium Inorganic materials 0.000 claims description 2
- JMXKSZRRTHPKDL-UHFFFAOYSA-N titanium ethoxide Chemical compound [Ti+4].CC[O-].CC[O-].CC[O-].CC[O-] JMXKSZRRTHPKDL-UHFFFAOYSA-N 0.000 claims description 2
- 229910002651 NO3 Inorganic materials 0.000 claims 1
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 claims 1
- IOVCWXUNBOPUCH-UHFFFAOYSA-M Nitrite anion Chemical compound [O-]N=O IOVCWXUNBOPUCH-UHFFFAOYSA-M 0.000 claims 1
- 150000002009 diols Chemical class 0.000 claims 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 claims 1
- 150000002736 metal compounds Chemical class 0.000 claims 1
- 230000035484 reaction time Effects 0.000 claims 1
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 abstract description 9
- 238000006460 hydrolysis reaction Methods 0.000 abstract description 3
- 239000000463 material Substances 0.000 description 25
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 description 6
- 238000007599 discharging Methods 0.000 description 6
- 229910001416 lithium ion Inorganic materials 0.000 description 6
- 239000002245 particle Substances 0.000 description 6
- HLLICFJUWSZHRJ-UHFFFAOYSA-N tioxidazole Chemical compound CCCOC1=CC=C2N=C(NC(=O)OC)SC2=C1 HLLICFJUWSZHRJ-UHFFFAOYSA-N 0.000 description 6
- 229910002986 Li4Ti5O12 Inorganic materials 0.000 description 5
- 239000007773 negative electrode material Substances 0.000 description 5
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 4
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 239000011148 porous material Substances 0.000 description 4
- 239000002033 PVDF binder Substances 0.000 description 3
- 229910003087 TiOx Inorganic materials 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- 229910021389 graphene Inorganic materials 0.000 description 3
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- 229910009866 Ti5O12 Inorganic materials 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 238000000498 ball milling Methods 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000003990 capacitor Substances 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 239000004020 conductor Substances 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 150000007524 organic acids Chemical class 0.000 description 2
- 235000005985 organic acids Nutrition 0.000 description 2
- 239000000047 product Substances 0.000 description 2
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- 239000000126 substance Substances 0.000 description 2
- 238000003786 synthesis reaction Methods 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910001290 LiPF6 Inorganic materials 0.000 description 1
- 150000004649 carbonic acid derivatives Chemical class 0.000 description 1
- 239000010406 cathode material Substances 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 239000013065 commercial product Substances 0.000 description 1
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- 238000001816 cooling Methods 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 239000011267 electrode slurry Substances 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 239000008151 electrolyte solution Substances 0.000 description 1
- 238000005562 fading Methods 0.000 description 1
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- 238000001914 filtration Methods 0.000 description 1
- 150000004679 hydroxides Chemical class 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- FUJCRWPEOMXPAD-UHFFFAOYSA-N lithium oxide Chemical class [Li+].[Li+].[O-2] FUJCRWPEOMXPAD-UHFFFAOYSA-N 0.000 description 1
- 229910001947 lithium oxide Inorganic materials 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
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- 238000001878 scanning electron micrograph Methods 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
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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
- H01M4/48—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
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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
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
- H01M4/625—Carbon or graphite
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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 novel lithium titanate-carbon nanotube electrode material, which comprises the following steps: s1: mixing an NMP mixture containing 4 wt% of carbon nano tubes, dihydric alcohol and titanate, adding the mixture into a homogeneous reactor, stirring the mixture to perform polymerization reaction to form polymer mixed slurry A with the carbon nano tubes, performing suction filtration on the slurry A, and washing the slurry A with a methanol solution to obtain a polymer M with the carbon nano tubes; s2: mixing the polymer M with the carbon nano tube and a lithium compound, dissolving the mixture in water, then placing the mixture in a homogeneous reactor, stirring the mixture to perform hydrolysis reaction to obtain mixture slurry B, performing suction filtration on the slurry B, and washing the slurry B with a methanol solution to obtain a solid N; s3: and sintering the solid N in a high-temperature furnace in an inert atmosphere to obtain the lithium titanate-carbon nanotube electrode material. The lithium titanate-carbon nanotube electrode material prepared by the preparation method can realize charge and discharge under large current, and solves the problems of capacity attenuation and poor rate capability during charge and discharge under large current.
Description
Technical Field
The invention relates to a lithium titanate-carbon nanotube serving as a negative electrode material of a lithium ion battery and having high capacity and deep charge and discharge capacity and a preparation method thereof.
Background
Lithium titanate negative electrode material (Li) in commercial market at present4Ti5O12) It has the advantages of high safety, good high-rate charge-discharge performance, excellent cycle performance, stable charge-discharge voltage, etc., however, Li4Ti5O12The electron conductivity (and lithium ion mobility) of the material is low, so that the capacitance attenuation is large during large-current charge and discharge, and the rate capability is poor.
In the prior art, lithium titanate and a conductive agent with excellent conductive performance, such as graphene, activated carbon and the like, are mainly subjected to composite doping to prepare an electrode material so as to make up for the defect of insufficient conductive capability of the lithium titanate material. Generally, the lithium titanate-activated carbon composite electrode material prepared can cause pore channel blockage, reduce the pore volume of activated carbon and the specific surface area of the composite material, and is not favorable for full exertion of adsorption performance. In the preparation process of the lithium titanate-graphene composite electrode, due to the limitation of the preparation method, the graphene is difficult to be uniformly dispersed in the slurry, and the battery capacity, the charge-discharge rate and other performances of the prepared electrode are not ideal.
Disclosure of Invention
The invention aims to provide a novel preparation method of a lithium titanate-carbon nanotube electrode material aiming at the defects in the prior art, which comprises the following steps:
s1: mixing and adding a carbon nano tube, dihydric alcohol, titanate and a dispersing agent into a homogeneous reactor, stirring to perform polymerization reaction to form polymer mixed slurry A with the carbon nano tube, performing suction filtration on the slurry A, and washing with a washing solvent to obtain a polymer M with the carbon nano tube;
the dispersant in S1 is an organic substance that is liquid at room temperature, other than water and organic acids, such as at least one of alcohols, ethers, aldehydes, ketones, esters, amines, amides, and hydrocarbons, but is not limited to these types of solvents.
The washing solvent in S1 is an organic substance that is liquid at room temperature, excluding water and organic acids, such as at least one of alcohols, ethers, aldehydes, ketones, esters, amines, amides, and hydrocarbons, but is not limited to these types of solvents.
S2: mixing the polymer M with the carbon nano tube and a lithium compound, mixing the mixture with water, putting the mixture into a homogeneous reactor, stirring the mixture to perform hydrolysis reaction to obtain mixture slurry B, and performing suction filtration on the slurry B to obtain a solid N;
s3: and sintering the solid N in a high-temperature furnace in an inert atmosphere to obtain the lithium titanate-carbon nanotube electrode material.
Preferably, the glycol in step S1 is at least one selected from the group consisting of ethylene glycol, 1, 3-propanediol and 1, 2-propanediol.
Preferably, the titanate in step S1 is at least one selected from butyl titanate, isopropyl titanate, n-propyl titanate, ethyl titanate and methyl titanate.
Preferably, the weight ratio X of the dihydric alcohol to the carbon nanotubes in the step S1 is selected from 100:0.1 to 1:1, preferably from 50:1 to 10: 1.
Preferably, in the step S1, the weight ratio Y of the titanate to the carbon nanotube is 5:1 to 100: 1.
Preferably, the compound of lithium in step S2 is selected from: lithium oxides, hydroxides, carbonates, bicarbonates, nitrates, nitrites, organic carboxylates, organometallic compounds or mixtures of these compounds.
Preferably, the ratio Z of the number of lithium (Li) atoms to the number of titanium (Ti) atoms of the titanate in step S1 and the lithium compound in step S2 is selected from 3:5 to 6: 5.
Preferably, the temperature of the homogeneous reactor in the steps S1 and S2 is set to 50 to 250 ℃, preferably 100 to 200 ℃.
Preferably, the mixture slurry in steps S1 and S2 is reacted in the homogeneous reactor for 0.2-15 h.
Preferably, the sintering temperature in step S3 is selected from 300-800 deg.C, and the preferred temperature is 400 deg.C to 750 deg.C.
Preferably, the inert gas in step S3 is at least one of nitrogen, argon, helium and neon.
Compared with the prior art, the invention has the beneficial effects that:
in the preparation process of the lithium titanate-carbon nanotube electrode material, the carbon nanotubes are uniformly distributed in the lithium titanate particle phase by reasonably setting the preparation steps and the process parameters.
In the lithium titanate-carbon nanotube lithium battery cathode material prepared by the preparation method, the crystal size of lithium titanate is nanoscale, the diffusion distance of lithium ions in the crystal is reduced, but the performance of lithium titanate is not changed, the addition of the carbon nanotube improves the performance of a conductor of the material, and the increased pore structure (the interface pore of CNT and lithium titanate is beneficial to the entering of an electrolyte solution) is beneficial to Li+Migration of (2), reduction of Li+The transfer impedance of the capacitor enables the capacitor to realize charging and discharging under large current, and solves the problems of capacity attenuation and poor rate capability during charging and discharging under large current.
Lithium metal is added into the lithium titanate-carbon nanotube material as the positive electrodeIn the test of the button cell prepared for the cathode, the measured specific capacity is 221mAh/g (much higher than Li) under the condition of charging and discharging with the current density of 300mA/g4Ti5O12175mAh/g) and no capacity fading after 500 charges and discharges.
Drawings
Fig. 1 is a synthesis principle of the lithium titanate-carbon nanotube electrode material prepared in example 1, where MOF is a polymer formed by polymerization of isopropyl titanate and ethylene glycol, and CNT is a carbon nanotube.
Fig. 2 is an SEM photograph of the lithium titanate-carbon nanotube material prepared in example 1.
FIG. 3 is an XRD pattern of lithium titanate and lithium titanate-carbon nanotube material prepared in example 1, LTO-CNTs representing lithium titanate-carbon nanotube negative electrode material, LTO representing lithium titanate Li4Ti5O12。
FIG. 4 is a graph of the AC impedance of lithium titanate-carbon nanotube material prepared in example 1, LTO-CNTs for lithium titanate-carbon nanotube material, pure LTO for lithium titanate Li4Ti5O12。
FIG. 5 is a cycle curve of a charge and discharge test of the lithium titanate-carbon nanotube material of example 1 at a current density of 300 mA/g.
Fig. 6 is a multiplying power cycle diagram of the lithium titanate-carbon nanotube material and the lithium titanate in example 1 under different current densities, wherein the charging and discharging tests are performed at current densities of 100mA/g, 200mA/g, 300mA/g, 400mA/g and 500mA/g, and after 20 cycles at each current density, the cycle is returned to the current density of 100mA/g for 20 cycles, and the test is ended.
Fig. 7 is a multiplying power cycle diagram of lithium titanate-carbon nanotube material of example 2 under different current densities, wherein the charging and discharging tests are performed at current densities of 100mA/g, 200mA/g, 300mA/g, 400mA/g and 500mA/g, and after 20 cycles at each current density, the test is ended after returning to the current density of 100mA/g for 20 cycles.
Fig. 8 is a multiplying power cycle diagram of the lithium titanate-carbon nanotube material of example 3 under different current densities, wherein the charging and discharging tests are performed at current densities of 100mA/g, 200mA/g, 300mA/g, 400mA/g and 500mA/g, and after 20 cycles at each current density, the test is ended after the current density returns to the current density of 100mA/g and the cycle is performed for 20 times.
Detailed Description
The lithium titanate-carbon nanotube electrode material and the preparation method thereof according to the technical scheme of the present invention are further described in detail below with reference to specific embodiments and accompanying drawings.
Example one
Weighing 3.1251g of carbon nano tube (dispersed in NMP and having the content of 4wt percent), the NMP mixture and 12.5062g of ethylene glycol, adding the mixture into a 100mL reaction kettle, and then adding 4.457g of isopropyl titanate into a glove box; after ventilation, the mixture is placed in a homogeneous reactor at 200 ℃ and reacts for 12 hours at the rotating speed of 10r/min to obtain slurry A;
cooling the slurry A, then carrying out suction filtration, washing with 10mL of methanol, putting 2.0190g of product into a reaction kettle, adding 5.0746g of lithium hydroxide aqueous solution (1.0mol/L), and then placing the mixture into a 200 ℃ homogeneous reactor to react for 12 hours at the rotating speed of 10 r/min; obtaining slurry B;
(III) filtering the slurry B to separate out solids, taking the solids and placing the solids in a tube furnace at 700 ℃ N2Sintering for 4 hours in the atmosphere to obtain a lithium titanate electrode material;
placing the lithium titanate electrode material, a PVDF NMP solution (3 wt%) and conductive carbon black in a ball milling tank according to the mass ratio of 8:1:1, and carrying out ball milling for 30min to obtain electrode slurry;
the above materials, PVDF (3% PVDF in N-methylpyrrolidone solution), and conductive carbon black were mixed at a mass ratio of 8:1:1 to prepare a slurry. Coating the slurry on copper foil, drying for 2h at 120 ℃ in nitrogen, taking the prepared pole piece as a positive electrode, taking a metal Li piece as a negative electrode and taking 1.0M LiPF6And (3) preparing a half cell by using the carbonate solution as an electrolyte.
The attached drawings in the specification can analyze that the lithium titanate-carbon nanotube negative electrode material has several remarkable characteristics:
the synthesis principle of the lithium titanate-carbon nanotube electrode material in fig. 1 can be known as follows:
firstly, carbon nano-tube is preparedThe (CNT), the isopropyl titanate and the glycol are put into a homogeneous reactor to be fully stirred and then react, the isopropyl titanate and the glycol can be polymerized to generate a polymer (MOF), and the Carbon Nano Tube (CNT) is uniformly wrapped in the polymer (MOF) structure generated by the reaction of the isopropyl titanate and the glycol. Separating the polymer with CNT, adding lithium hydroxide aqueous solution, continuously stirring and reacting for a certain time, carrying out on-site hydrolysis reaction on the solid polymer around the CNT to form TiOx (OH) y. mLiOH, uniformly wrapping the periphery of the CNT to obtain a solid product (TiOx (OH) y. mLiOH-CNT), and finally sintering the solid product (TiOx (OH) y. mLiOH-CNT) at high temperature in an inert gas atmosphere to obtain an electrode material, thereby realizing uniform distribution of carbon nanotubes in a lithium titanate particle phase and fully conducting Li with good lithium titanate+The ionic characteristics and the CNT electron conductors are combined, so that the capacitance, the charge and discharge rate and the stability of the electrode material are effectively improved.
As can be seen from the SEM image of the lithium titanate-carbon nanotube electrode material in fig. 2, the lithium titanate particles and the carbon nanotubes are uniformly and densely dispersed between each other, and the particles have a uniform size at the nanometer level, and they are agglomerated with each other to form aggregates having a size of about 1 μm, and have a stable framework structure, and at this time, the lithium titanate-carbon nanotube negative electrode material also exhibits the highest capacity.
From the XRD patterns of the lithium titanate and lithium titanate-carbon nanotube material in FIG. 3, there are no other impurity peaks in comparison with the standard spectrum, which indicates that the product prepared by using example 1 is relatively pure lithium titanate crystal Li4Ti5O12And carbon nanotubes.
As can be seen from the ac impedance diagram of the lithium titanate-carbon nanotube material in fig. 4, the comparison between the resistance value in the high frequency region and the pure lithium titanate shows that the addition of the carbon nanotube significantly increases the conductivity of the lithium titanate material and reduces the charge transfer impedance. The slope of the straight line of the low-frequency region of the composite material is also greater than that of the straight line of the pure lithium titanate material, which shows that Li is reduced+Diffusion resistance of ions in the material.
FIG. 4 shows that the charge-discharge cycle was carried out at 0.01V to 2.00V, and at a current density of 100mA/g, the charge-discharge stable cycle capacity was 260mAh/g, and the first charge-discharge cycle efficiency was 86%, indicating that the material had high lithium ion reversibility.
It can be seen from the above examples that the lithium titanate-carbon nanotube material prepared by the method of the present invention has a particle size of mostly nano-scale, the lithium titanate particles are uniformly and densely dispersed in the carbon nanotubes, and the lithium titanate-carbon nanotube material prepared by the method of example 1 has high purity and only has a lithium titanate phase. The circulating capacity measured under the current density of 300mA/g is 221mAh/g (much higher than the theoretical 175mAh/g), no attenuation is generated after 500 times of charge and discharge, and the circulating capacity of 200mAh/g is reached under the current density of 500mA/g when the multiplying power performance is tested, so that the material shows good multiplying power performance.
Example two
The difference between the second embodiment and the first embodiment is that the sintering temperature in the step (three) in the second embodiment is changed to 400 ℃, and the rest is the same as that in the first embodiment, and is not described herein.
EXAMPLE III
The difference between the third embodiment and the first embodiment is that the sintering temperature in the third step in the second embodiment is changed to 500 ℃, and the rest is the same as that in the first embodiment, and is not described herein.
As can be understood from the drawings attached to the specification, FIGS. 7 and 8, in the comparison between the second and third examples, the material sintered at 500 ℃ has a higher capacity than that sintered at 400 ℃ in comparison with the second and third examples at different sintering temperatures, and the capacity is 0.4 A.g-1The former is 250mAh/g and the latter is 200mAh/g at the current density. The capacity of the lithium titanate-carbon nanotube material prepared by sintering at 500 ℃ can also maintain 250mAh/g under high rate current density, the attenuation is reduced, and the lithium titanate-carbon nanotube material is prepared in the existing commercial product Li4Ti5O12Above all, only about 170mAh/g or even less can be achieved at 1C.
Claims (16)
1. A preparation method of a lithium titanate-carbon nanotube electrode material is characterized by comprising the following steps:
s1: mixing and adding a carbon nano tube, dihydric alcohol, titanate and a dispersing agent into a reactor, stirring to perform polymerization reaction to form polymer mixed slurry A with the carbon nano tube, separating the slurry A, and washing with a washing solvent to obtain a polymer M with the carbon nano tube;
s2: mixing the polymer M with the carbon nano tube, the lithium compound and water, then placing the mixture in a reactor, stirring and reacting to obtain mixture slurry B, and performing suction filtration on the slurry B to obtain solid N;
s3: and sintering the solid N in a high-temperature furnace in an inert atmosphere to obtain the lithium titanate-carbon nanotube electrode material.
2. The method of claim 1, wherein in step S1, the diol is at least one selected from the group consisting of ethylene glycol, 1, 3-propanediol, and 1, 2-propanediol.
3. The method of claim 1, wherein the titanate in step S1 is at least one selected from butyl titanate, isopropyl titanate, n-propyl titanate, ethyl titanate, and methyl titanate.
4. The method of claim 1, wherein the dispersant in step S1 is at least one selected from the group consisting of organic alcohols, ethers, aldehydes, ketones, esters, amines, amides, and hydrocarbons that are liquid at room temperature.
5. The method of claim 1, wherein the washing solvent in step S1 is at least one selected from the group consisting of organic alcohols, ethers, aldehydes, ketones, esters, amines, amides, and hydrocarbons that are liquid at room temperature.
6. The method for preparing a lithium titanate-carbon nanotube electrode material as claimed in claim 1, wherein in step S1, the weight ratio X of the glycol to the carbon nanotube is selected from 100:0.1 to 1: 1.
7. The preparation method of the lithium titanate-carbon nanotube electrode material according to claim 6, wherein in the step S1, the weight ratio X of the glycol to the carbon nanotube is selected from 50:1 to 10: 1.
8. The method for preparing a lithium titanate-carbon nanotube electrode material as claimed in claim 1, wherein the weight ratio Y of the titanate to the carbon nanotube in step S1 is selected from 5:1 to 100: 1.
9. The method of claim 1, wherein the lithium compound in step S2 is selected from the group consisting of: at least one of an oxide, hydroxide, carbonate, bicarbonate, nitrate, nitrite, organic carboxylate, and organic metal compound of lithium.
10. The method for preparing a lithium titanate-carbon nanotube electrode material as claimed in claim 1, wherein the atomic ratio Z of lithium (Li) to titanium (Ti) of the titanate in step S1 and the lithium compound in step S2 is selected from 3:5 to 6: 5.
11. The method for preparing a lithium titanate-carbon nanotube electrode material as claimed in claim 1, wherein the reaction temperature in steps S1 and S2 is 50-250 ℃.
12. The method of preparing a lithium titanate-carbon nanotube electrode material as claimed in claim 11, wherein the reaction temperature in steps S1 and S2 is 100-200 ℃.
13. The method of claim 1, wherein the reaction time of the mixture slurry in steps S1 and S2 is 0.2-15 h.
14. The method as claimed in claim 1, wherein the sintering temperature in step S3 is selected from 300-800 ℃.
15. The method of preparing a lithium titanate-carbon nanotube electrode material as claimed in claim 14, wherein the sintering temperature in step S3 is 400 ℃ to 750 ℃.
16. The method of claim 1, wherein the inert gas in step S3 is at least one of nitrogen, argon, helium, and neon.
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