CN114551858A - Lithium titanate composite material and preparation method thereof - Google Patents
Lithium titanate composite material and preparation method thereof Download PDFInfo
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- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 129
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 122
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 title claims abstract description 119
- 239000002131 composite material Substances 0.000 title claims abstract description 97
- 238000002360 preparation method Methods 0.000 title claims abstract description 25
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 29
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical group [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 claims abstract description 24
- 229910001928 zirconium oxide Inorganic materials 0.000 claims abstract description 24
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 17
- 239000011258 core-shell material Substances 0.000 claims abstract description 7
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 34
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 claims description 28
- 238000000034 method Methods 0.000 claims description 28
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical group O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 20
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 claims description 18
- 238000000151 deposition Methods 0.000 claims description 18
- 229910052684 Cerium Inorganic materials 0.000 claims description 17
- 229910052757 nitrogen Inorganic materials 0.000 claims description 17
- 238000006243 chemical reaction Methods 0.000 claims description 15
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical group [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 claims description 12
- 229910052808 lithium carbonate Inorganic materials 0.000 claims description 12
- 239000011248 coating agent Substances 0.000 claims description 11
- 238000000576 coating method Methods 0.000 claims description 11
- 238000007740 vapor deposition Methods 0.000 claims description 11
- 238000001354 calcination Methods 0.000 claims description 10
- 239000004408 titanium dioxide Substances 0.000 claims description 10
- 239000011230 binding agent Substances 0.000 claims description 9
- VYLVYHXQOHJDJL-UHFFFAOYSA-K cerium trichloride Chemical group Cl[Ce](Cl)Cl VYLVYHXQOHJDJL-UHFFFAOYSA-K 0.000 claims description 9
- 230000008021 deposition Effects 0.000 claims description 9
- 239000010426 asphalt Substances 0.000 claims description 8
- 239000006258 conductive agent Substances 0.000 claims description 8
- 238000002156 mixing Methods 0.000 claims description 8
- 239000010936 titanium Substances 0.000 claims description 8
- 229910052719 titanium Inorganic materials 0.000 claims description 8
- 229910021389 graphene Inorganic materials 0.000 claims description 7
- PAYRUJLWNCNPSJ-UHFFFAOYSA-N Aniline Chemical compound NC1=CC=CC=C1 PAYRUJLWNCNPSJ-UHFFFAOYSA-N 0.000 claims description 6
- 238000003763 carbonization Methods 0.000 claims description 6
- 238000010438 heat treatment Methods 0.000 claims description 6
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 claims description 5
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 4
- KAESVJOAVNADME-UHFFFAOYSA-N Pyrrole Chemical compound C=1C=CNC=1 KAESVJOAVNADME-UHFFFAOYSA-N 0.000 claims description 4
- YTPLMLYBLZKORZ-UHFFFAOYSA-N Thiophene Chemical compound C=1C=CSC=1 YTPLMLYBLZKORZ-UHFFFAOYSA-N 0.000 claims description 4
- 239000002041 carbon nanotube Substances 0.000 claims description 4
- 229910021393 carbon nanotube Inorganic materials 0.000 claims description 4
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 4
- 239000004202 carbamide Substances 0.000 claims description 3
- 229910021529 ammonia Inorganic materials 0.000 claims description 2
- 239000002134 carbon nanofiber Substances 0.000 claims description 2
- YNQRWVCLAIUHHI-UHFFFAOYSA-L dilithium;oxalate Chemical compound [Li+].[Li+].[O-]C(=O)C([O-])=O YNQRWVCLAIUHHI-UHFFFAOYSA-L 0.000 claims description 2
- 229930192474 thiophene Natural products 0.000 claims description 2
- 239000000463 material Substances 0.000 abstract description 23
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 abstract description 7
- 229910001416 lithium ion Inorganic materials 0.000 abstract description 7
- 238000004519 manufacturing process Methods 0.000 abstract description 4
- 239000000126 substance Substances 0.000 abstract description 3
- 239000010410 layer Substances 0.000 description 39
- 230000000052 comparative effect Effects 0.000 description 18
- 239000007773 negative electrode material Substances 0.000 description 14
- -1 modified lithium titanate Chemical class 0.000 description 13
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical group [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 10
- 239000000203 mixture Substances 0.000 description 9
- 239000002245 particle Substances 0.000 description 7
- 239000002904 solvent Substances 0.000 description 7
- 239000003792 electrolyte Substances 0.000 description 6
- 239000007789 gas Substances 0.000 description 6
- 229910052786 argon Inorganic materials 0.000 description 5
- 238000000498 ball milling Methods 0.000 description 5
- 230000008569 process Effects 0.000 description 5
- 238000012360 testing method Methods 0.000 description 5
- 238000007599 discharging Methods 0.000 description 4
- 230000014759 maintenance of location Effects 0.000 description 4
- VZGDMQKNWNREIO-UHFFFAOYSA-N tetrachloromethane Chemical compound ClC(Cl)(Cl)Cl VZGDMQKNWNREIO-UHFFFAOYSA-N 0.000 description 4
- 229910001290 LiPF6 Inorganic materials 0.000 description 3
- 229910003481 amorphous carbon Inorganic materials 0.000 description 3
- BCZWPKDRLPGFFZ-UHFFFAOYSA-N azanylidynecerium Chemical compound [Ce]#N BCZWPKDRLPGFFZ-UHFFFAOYSA-N 0.000 description 3
- 238000005137 deposition process Methods 0.000 description 3
- 230000004927 fusion Effects 0.000 description 3
- XDTMQSROBMDMFD-UHFFFAOYSA-N Cyclohexane Chemical compound C1CCCCC1 XDTMQSROBMDMFD-UHFFFAOYSA-N 0.000 description 2
- 239000004743 Polypropylene Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000011247 coating layer Substances 0.000 description 2
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- 229920001155 polypropylene Polymers 0.000 description 2
- 239000011343 solid material Substances 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical group O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910013872 LiPF Inorganic materials 0.000 description 1
- 229910001228 Li[Ni1/3Co1/3Mn1/3]O2 (NCM 111) Inorganic materials 0.000 description 1
- 101150058243 Lipf gene Proteins 0.000 description 1
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 1
- 229910009866 Ti5O12 Inorganic materials 0.000 description 1
- 235000011114 ammonium hydroxide Nutrition 0.000 description 1
- 230000003139 buffering effect Effects 0.000 description 1
- 239000006229 carbon black Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000013065 commercial product Substances 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 238000009831 deintercalation Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 238000009830 intercalation Methods 0.000 description 1
- 230000002687 intercalation 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
- 125000004433 nitrogen atom Chemical group N* 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
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- 238000007086 side reaction Methods 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 229910052723 transition metal Inorganic materials 0.000 description 1
- 150000003624 transition metals Chemical class 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—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
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
- H01M4/625—Carbon or graphite
-
- 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)
- Battery Electrode And Active Subsutance (AREA)
- Inorganic Compounds Of Heavy Metals (AREA)
Abstract
The invention relates to a lithium titanate composite material and a preparation method thereof, belonging to the technical field of lithium ion battery materials. The lithium titanate composite material is of a core-shell structure, the core is cerium-nitrogen-doped lithium titanate, the shell comprises an inner layer and an outer layer, the inner layer is a conductive carbon layer, and the outer layer is a zirconium oxide layer. The core of the lithium titanate composite material is cerium-nitrogen-doped lithium titanate, the lithium titanate composite material has high electronic conductivity and large specific capacity, the carbon layer in the shell has good conductivity, and the zirconium oxide layer in the shell has good chemical stability and conductivity, so that the gas production problem of the lithium titanate composite material can be improved, and the rate capability of the lithium titanate composite material can be improved.
Description
Technical Field
The invention relates to a lithium titanate composite material and a preparation method thereof, belonging to the technical field of lithium ion battery materials.
Background
Lithium titanate (Li)4Ti5O12) The composite oxide is a composite oxide of metallic lithium and low-potential transition metal titanium, and has the greatest characteristic of zero strain property. By "zero strain" is meant that the crystal has substantially no change in lattice constant and volume during intercalation or deintercalation of lithium ions. In the charge-discharge cycle, the zero-strain property can avoid the damage of the structure caused by the back-and-forth expansion of the electrode material, thereby improving the cycle performance and the service life of the electrode, reducing the specific capacity attenuation caused by the cycle, and having very good multiplying power and cycle performance thereof. But at the same time, lithium titanate negative electrode material is storedThe lithium titanate material obtained in the traditional sintering process is easy to generate side reaction and generate gas in the charging and discharging process because lithium titanate is directly contacted with electrolyte, and meanwhile, the electron conductivity of the lithium titanate is poor, so that the temperature rise of the battery is increased rapidly in the large-rate charging and discharging process, and the decomposition of low-boiling-point flux in the electrolyte generates gas, so that the safety performance deviation of the battery is caused. Although researchers have solved the problem of gas generation of batteries by coating the surface of lithium titanate material, this method causes problems such as reduction in rate capability, poor consistency of material due to conventional liquid phase coating, and the like. For example, chinese patent document CN107910498B discloses a modified lithium titanate negative electrode material, a preparation method thereof, and a lithium titanate battery, wherein the modified lithium titanate negative electrode material has a particle structure, and an outer layer of the particle is graphene composite al (oh)3Secondary coating layer, graphene composite Al (OH)3The secondary coating layer coats the secondary lithium titanate particles, the secondary lithium titanate particles are formed by agglomerating a plurality of graphene-coated primary lithium titanate particles, although the conductivity and the high-temperature performance of the obtained modified lithium titanate negative electrode material are improved, the processing performance is not improved, meanwhile, the uniformity and the consistency of the material obtained by coating by adopting a liquid phase method are poor, the electrochemical performance of the modified lithium titanate negative electrode material is influenced, and in addition, due to Al (OH)3The impedance of the lithium titanate is high, so that the rate capability of the prepared modified lithium titanate negative electrode material is low.
Disclosure of Invention
The invention aims to provide a lithium titanate composite material, which is used for solving the problem that the rate capability of a lithium titanate material is reduced when the gas production problem of the lithium titanate material is solved by coating the surface of the lithium titanate material at present.
The invention also aims to provide a preparation method of the lithium titanate composite material.
In order to achieve the above object, the lithium titanate composite material of the present invention adopts the following technical scheme:
a lithium titanate composite material is of a core-shell structure, the core is cerium-nitrogen-doped lithium titanate, the shell comprises an inner layer and an outer layer, the inner layer is a conductive carbon layer, and the outer layer is a zirconium oxide layer.
The lithium titanate composite material has a core-shell structure, the core is cerium-nitrogen-doped lithium titanate, the electronic conductivity and the specific capacity are high, the carbon layer in the shell has a good conductive effect, an additional storage effect of lithium ions and a buffering effect of lithium titanate expansion, and the zirconium oxide layer in the shell has good chemical stability and conductive performance, so that the gas production problem of the lithium titanate composite material can be solved, and the rate capability of the lithium titanate composite material can be improved.
The preparation method of the lithium titanate composite material adopts the technical scheme that:
a preparation method of a lithium titanate composite material comprises the following steps: firstly, coating a carbon layer on the surface of cerium-nitrogen-doped lithium titanate to obtain a composite material A, and then coating a zirconium oxide layer on the surface of the composite material A.
According to the preparation method of the lithium titanate composite material, cerium and nitrogen-doped lithium titanate are used as the inner core, nitrogen atoms can improve the electronic conductivity of the lithium titanate composite material, cerium atoms can improve the specific capacity and the structural stability of the lithium titanate composite material, the carbon layer coated on the surface of the cerium and nitrogen-doped lithium titanate has good conductivity, and the zirconium oxide layer coated on the surface of the carbon layer can improve the gas production problem of the lithium titanate composite material and can also improve the rate capability of the lithium titanate composite material.
Preferably, the cerium-nitrogen doped lithium titanate is obtained by a preparation method comprising the following steps: uniformly mixing a titanium source, a lithium source, a cerium source and a nitrogen source, and calcining; the titanium source is titanium dioxide; the lithium source is lithium carbonate and/or lithium oxalate.
Preferably, the lithium source is lithium carbonate.
Preferably, the cerium source is cerium chloride. Preferably, the nitrogen source is selected from one or any combination of ammonia, aniline, urea, pyrrole and thiophene. Preferably, the molar ratio of the titanium dioxide to the lithium carbonate is (4-6): (6-8). Further preferably, the molar ratio of titanium dioxide to lithium carbonate is 5.75: 7.3. Preferably, the cerium source is cerium chloride; the ratio of the mass of the cerium chloride to the mass of the nitrogen source to the sum of the mass of the titanium dioxide and the lithium carbonate is (1-5): 0.5-2): 100.
Preferably, the calcining temperature is 750-900 ℃ and the calcining time is 6-8 h. For example, the temperature of the calcination is 800 ℃ and the time of the calcination is 6 hours.
In order to uniformly mix the titanium source, the lithium source, the cerium source and the nitrogen source, the titanium source, the lithium source, the cerium source and the nitrogen source may be mixed with an appropriate amount of solvent, and then ball-milled by a ball mill. Preferably, the solvent is selected from one or any combination of N-methyl pyrrolidone, carbon tetrachloride and cyclohexane. Preferably, the solvent is used in an amount of 500mL per 46g of the titanium source. Preferably, the time of the ball milling treatment is 24 h.
Preferably, the method for coating the surface of the cerium-nitrogen-doped lithium titanate with the carbon layer comprises the following steps: uniformly mixing cerium, nitrogen-doped lithium titanate, a binder and a conductive agent, and carrying out carbonization treatment; the binder is asphalt.
Preferably, the mass ratio of the cerium to the nitrogen-doped lithium titanate to the binder to the conductive agent is 100 (10-20) to (1-5).
Preferably, the softening point of the asphalt is (50-300) DEG C. For example, the softening point of the asphalt is (50-200) DEG C. Preferably, the conductive agent is selected from one or any combination of conductive carbon black, carbon nanotubes, graphene and vapor grown carbon fibers. Preferably, the conductive carbon black is the commercial product Super P. Preferably, the carbonization treatment is performed under an inert atmosphere. Preferably, the inert atmosphere is argon. Preferably, the temperature of the carbonization treatment is (150-300) DEG C. Preferably, the carbonization treatment time is (1-2) h.
Preferably, the carbonization treatment is performed in a fusion machine. Preferably, the fusion machine is a vertical roller furnace.
Preferably, the zirconia layer is formed by an atomic vapor deposition method. The zirconium oxide layer deposited on the surface of the composite material A by an atomic vapor deposition (ALD) method has the characteristics of high density, good consistency and the like, and the zirconium oxide has low impedance, so that the power and the cycle performance of the lithium titanate composite material can be obviously improved; meanwhile, the atomic vapor deposition (ALD) method can enable the coated zirconia layer to be more compact, is beneficial to avoiding the contact between the electrolyte and the inner core of the lithium titanate composite material, and reduces the occurrence of the secondary reaction of the inner core of the lithium titanate composite material.
Preferably, the atomic vapor deposition method comprises the steps of:
s1, transferring the composite material A to a reaction cavity deposition position;
s2, vacuumizing the evaporator to (10-100) toor, heating the evaporator to (100-600) DEG C, and gasifying the zirconium oxide in the evaporator under the condition;
s3, allowing the gasified zirconia to enter a reaction chamber with a vacuum degree of (5-20) toor in a pulse mode at a flow rate of 50sccm under the driving of nitrogen, adsorbing the zirconia on the surface of the composite material A, and depositing for (1-10) min;
s4, repeating step S3 (1-10) times.
Further preferably, the atomic vapor deposition method comprises the steps of:
s1, transferring the composite material A to a reaction cavity deposition position;
s2, vacuumizing the evaporator to (10-100) toor, heating the evaporator to (100-600) DEG C, and gasifying the zirconium oxide in the evaporator under the condition;
s3, allowing the gasified zirconia to enter a reaction chamber with a vacuum degree of (5-20) toor in a pulse mode at a flow rate of 50sccm under the driving of nitrogen, adsorbing the zirconia on the surface of the composite material A, and depositing for (1-5) min;
s4, repeating step S3 (5-10) times.
Drawings
Fig. 1 is a graph of the rate cycle curves of pouch cells using lithium titanate composites prepared in example 4, example 5, example 6 and comparative example as negative electrode materials.
Detailed Description
The technical solution of the present invention is further described below with reference to specific examples.
The specific embodiment of the lithium titanate composite material of the invention is as follows:
example 1
The lithium titanate composite material is of a core-shell structure, the core is cerium-nitrogen-doped lithium titanate, the shell comprises an inner layer and an outer layer, the inner layer is a carbon layer, the carbon layer comprises amorphous carbon and carbon nanotubes, and the outer layer is a zirconium oxide layer.
Example 2
The lithium titanate composite material is of a core-shell structure, the core is cerium-nitrogen-doped lithium titanate, the shell comprises an inner layer and an outer layer, the inner layer is a carbon layer, the carbon layer comprises amorphous carbon and graphene, and the outer layer is a zirconium oxide layer.
Example 3
The lithium titanate composite material is of a core-shell structure, the core is cerium-nitrogen-doped lithium titanate, the shell comprises an inner layer and an outer layer, the inner layer is a carbon layer, the carbon layer comprises amorphous carbon and super carbon black, and the outer layer is a zirconium oxide layer.
Secondly, the specific embodiment of the preparation method of the lithium titanate composite material of the invention is as follows:
example 4
The preparation method of the lithium titanate composite material provided by the embodiment specifically comprises the following steps:
1) preparation of cerium and nitrogen doped lithium titanate:
adding 46g (0.575mol) of titanium dioxide, 54g (0.731mol) of lithium carbonate, 3g of cerium chloride, 1g of aniline and 500 mLN-methyl pyrrolidone into a ball mill, carrying out ball milling and mixing for 24h to obtain a mixture, and then calcining the mixture at 800 ℃ for 6h to obtain the cerium and nitrogen doped lithium titanate.
2) Preparation of composite material A:
100g of cerium-nitrogen-doped lithium titanate, 15g of high-temperature asphalt (softening point 200 ℃) and 3g of carbon nano tubes are uniformly mixed to obtain a pre-fused material, the pre-fused material is transferred to a vertical roller furnace, then argon is introduced into the vertical roller furnace, and the pre-fused material is fused for 1 hour at 200 ℃ to obtain the composite material A.
3) Preparing a lithium titanate composite material:
and transferring the composite material A to a deposition position of a reaction cavity, and depositing zirconium oxide on the surface of the fusion material by an atomic vapor deposition (ALD) method to obtain the lithium titanate composite material. The deposition process was as follows:
s1, transferring the composite material A to a reaction cavity deposition position;
s2, vacuumizing the evaporator to 50toor, heating the evaporator to 300 ℃, and gasifying the zirconium oxide in the evaporator under the condition;
s3, allowing the gasified zirconia to enter a reaction cavity with a vacuum degree of 10toor in a pulse mode at a flow rate of 50sccm under the carrying of nitrogen, adsorbing the zirconia on the surface of the composite material A, and depositing for 5 min;
s4, repeat step S3 5 times.
Example 5
The preparation method of the lithium titanate composite material provided by the embodiment specifically comprises the following steps:
1) preparation of cerium-nitrogen-doped lithium titanate:
adding 46g (0.575mol) of titanium dioxide, 54g (0.731mol) of lithium carbonate, 1g of cerium chloride, 0.5g of urea and 500mL of carbon tetrachloride into a ball mill, carrying out ball milling and mixing for 24h to obtain a mixture, and then calcining the mixture at 800 ℃ for 6h to obtain the cerium-nitrogen doped lithium titanate.
2) Preparation of composite material A:
100g of cerium-nitrogen-doped lithium titanate, 10g of medium-temperature asphalt (softening point 150 ℃) and 1g of graphene are uniformly mixed to obtain a pre-fused material, the pre-fused material is transferred to a vertical roller furnace, then argon is introduced into the vertical roller furnace, and the pre-fused material is fused for 2 hours at 150 ℃ to obtain a composite material A.
3) Preparing a lithium titanate composite material:
transferring the fused material to a deposition position of a reaction cavity, and depositing zirconium oxide on the surface of the fused material by an atomic vapor deposition (ALD) method to obtain the lithium titanate composite material. The deposition process was as follows:
s1, transferring the composite material A to a reaction cavity deposition position;
s2, vacuumizing the evaporator to 10toor, heating the evaporator to 100 ℃, and gasifying the zirconium oxide in the evaporator under the condition;
s3, allowing the gasified zirconia to enter a reaction cavity with a vacuum degree of 5toor in a pulse mode at a flow rate of 50sccm under the driving of nitrogen, adsorbing the zirconia on the surface of the composite material A, and depositing for 1 min;
s4, repeat step S3 10 times.
Example 6
The preparation method of the lithium titanate composite material provided by the embodiment specifically comprises the following steps:
1) preparation of cerium and nitrogen doped lithium titanate:
adding 46g (0.575mol) of titanium dioxide, 54g (0.731mol) of lithium carbonate, 5g of cerium chloride, 20g of ammonia water with the mass fraction of 10% and 500mL of cyclohexane into a ball mill, carrying out ball milling and mixing for 24h to obtain a mixture, and then calcining the mixture at 800 ℃ for 6h to obtain the cerium-nitrogen doped lithium titanate.
2) Preparation of composite material A:
100g of cerium, nitrogen-doped lithium titanate, 20g of medium-temperature asphalt (softening point 50 ℃) and 5g of conductive carbon black (Super P) are uniformly mixed to obtain a pre-fused material, the pre-fused material is transferred to a vertical roller furnace, then argon is introduced into the vertical roller furnace, and the pre-fused material is fused for 2 hours at 300 ℃ to obtain the composite material A.
3) Preparing a lithium titanate composite material:
transferring the fused material to a deposition position of a reaction cavity, and depositing zirconium oxide on the surface of the fused material by an atomic vapor deposition (ALD) method to obtain the lithium titanate composite material. The deposition process was as follows:
s1, transferring the composite material A to a reaction cavity deposition position;
s2, vacuumizing the evaporator to 100toor, heating the evaporator to 600 ℃, and gasifying the zirconium oxide in the evaporator under the condition;
s3, allowing the gasified zirconia to enter a reaction cavity with a vacuum degree of 20toor in a pulse mode at a flow rate of 50sccm under the driving of nitrogen, adsorbing the zirconia on the surface of the composite material A, and depositing for 1 min;
s4, repeat step S3 10 times.
Comparative example
The preparation method of the lithium titanate composite material of the comparative example comprises the following steps:
adding 46g (0.575mol) of titanium dioxide, 54g (0.731mol) of lithium carbonate and 500 mLN-methyl pyrrolidone into a ball mill, carrying out ball milling and mixing for 24h to obtain a mixture, and then calcining the mixture at 800 ℃ for 6h to obtain the lithium titanate composite material.
Examples of the experiments
1. Physical and chemical properties
The lithium titanate composite materials prepared in examples 4 to 6 and the comparative example were respectively pressed into a block under the same conditions, and then the resistivity of the lithium titanate composite material pressed into the block was tested using a four-probe tester. The lithium titanate composites prepared in examples 4, 5, 6 and comparative examples, which were pressed into a block, had resistivity of 18.9, 18.3, 19.5 and 245.3S/cm, respectively, and the results showed that the lithium titanate composites prepared in examples 4-6 had lower resistance and higher conductivity.
1g of the lithium titanate composite material prepared in the embodiment 4, the embodiment 5, the embodiment 6 or the comparative example is placed in a kettle for testing a powder compaction density instrument, then the pressure is adopted for 2t for pressing, the kettle is kept still for 10s, a compacted solid material is obtained, the volume of the compacted solid material is calculated, and finally the compaction density is calculated. The compacted densities of the lithium titanate composites prepared in example 4, example 5, example 6 and comparative example were 1.01, 0.94, 0.91 and 0.75g/cm, respectively3. The results show that the lithium titanate composite materials prepared in examples 4-6 have higher compacted density and can improve the energy density of the battery.
The lithium titanate composite materials prepared in examples 4 to 6 and comparative example were tested according to the specifications of GBT 243334-2009 graphite-based negative electrode material for lithium ion batteries, and the test results are shown in table 1.
TABLE 1 particle diameter, tap density, specific surface area, specific first discharge capacity and first coulombic efficiency of lithium titanate composites prepared in examples 4 to 6 and comparative example
| Item | Example 4 | Example 5 | Example 6 | Comparative example |
| Particle size (D50, μm) | 8.6 | 8.9 | 9.5 | 10.1 |
| Tap density (g/cm)3) | 0.91 | 0.85 | 0.81 | 0.72 |
| Specific surface area (m)2/g) | 7.9 | 7.5 | 7.7 | 4.9 |
| Specific capacity of first discharge (mAh/g) | 156 | 158 | 154 | 148 |
| Initial coulomb efficiency (%) | 93.3 | 93.1 | 92.8 | 90.4 |
As can be seen from table 1, compared with the lithium titanate composite material prepared by the comparative example, the first discharge specific capacity of the lithium titanate composite material prepared by the example is improved to a certain extent, and the first coulombic efficiency is greatly improved.
2. Practicality of use
2.1 button cell
The lithium titanate composite materials prepared in examples 4-6 and comparative example are applied to button cells as negative electrode materials, and the electrochemical performance of the button cells is tested. The button cell consists of a negative pole piece, a counter electrode, electrolyte and a diaphragm, and is assembled in a glove box filled with argon. The button cell has metal lithium sheet as counter electrode, composite polypropylene (PP) membrane as diaphragm and LiPF as electrolyte6Solution (solvent composed of EC and DEC in a volume ratio of 1:1, LiPF6Concentration of (1 mol/L). The preparation method of the negative pole piece comprises the following steps: and adding a binder, a conductive agent and a solvent into the lithium titanate composite material prepared in the embodiment 4, the embodiment 5, the embodiment 6 or the comparative example, stirring and pulping, coating the prepared pulp on a copper foil, and then drying and rolling to obtain the negative pole piece of the button cell. The binder used in the preparation of the button cell negative electrode plate is LA132 binder, the conductive agent is SP, the solvent is secondary distilled water, and the mass ratio of the lithium titanate composite material, the LA132 binder, the conductive agent SP and the secondary distilled water is 95:4:1: 220.
The electrochemical performance (rate capability and cycle capability) of the button cell prepared by the Wuhan blue CT2001A battery tester is tested, the charging and discharging voltage range in the testing process is 1.5V-2.8V, and the charging and discharging rate is 0.1C. The rate performance (2C/0.1C) and cycle performance (0.2C/0.2C, 200 times) of the button cells using the lithium titanate composite materials prepared in example 4, example 5, example 6 and comparative example as the negative electrode material are shown in table 2.
Table 2 electrochemical performance of button cell using lithium titanate composite materials prepared in example 4, example 5, example 6 and comparative example as negative electrode material
| Item | Example 4 | Example 5 | Example 6 | Comparative example |
| Multiplying power performance (2C/0.1C) | 97.6 | 97.1 | 95.9 | 90.4 |
| Cycle performance (battery capacity retention,%) | 94.8 | 93.7 | 92.3 | 89.3 |
As can be seen from table 2, the lithium titanate composite materials prepared in examples 4 to 6 have excellent rate capability, particularly good high-rate charging capability, can be used for fast-charging batteries, and have good cycle performance, and can maintain a capacity retention rate of 90% or more after 200 cycles.
2.2 laminate polymer battery
The lithium titanate composite materials prepared in examples 4 to 6 and the comparative example were applied to a pouch battery (2Ah) as a negative electrode material, and the cycle performance (battery capacity retention rate) of the pouch battery prepared was tested, and the test results are shown in fig. 1 and table 3. The positive electrode of the soft package battery is made of LiNi1/3Co1/3Mn1/3O2The diaphragm is celegard2400, and the electrolyte in the soft package battery is LiPF6Solution (solvent composed of EC and DEC in a volume ratio of 1:1, LiPF6Concentration of (1.3 mol/L). The test conditions for the cycle performance of the pouch cell were as follows: the voltage range is 1.5-2.8V, the charge and discharge multiplying power is 5C/5C, the temperature is 25 +/-3 ℃, the cycle time is 500 times, and the charge and discharge depth is 80% SOC. The battery capacity retention rate is equal to the percentage of the capacity of the soft package battery after 500 times of circulation to the initial capacity.
TABLE 3 cycling performance of pouch cells
As can be seen from table 3, the cycle performance of the pouch cells using the lithium titanate composites prepared in examples 4 to 6 as the negative electrode material was significantly better than that of the pouch cells using the lithium titanate composites prepared in the comparative example as the negative electrode material for the following reasons: the SEI film formed in the cycle process of the lithium battery consumes lithium ions, so that the internal resistance of the battery is increased, and the zirconium oxide deposited by the atomic vapor deposition method has the characteristics of high lithium ion conductivity and stable structure, so that the cycle performance of the battery can be improved. Meanwhile, the cerium chloride doped in the core is beneficial to improving the structural stability and the electronic conductivity of the lithium titanate composite material, so that the cycle performance of the soft package battery is improved.
Claims (10)
1. A lithium titanate composite material is characterized in that the lithium titanate composite material is of a core-shell structure, the core is cerium-nitrogen-doped lithium titanate, the shell comprises an inner layer and an outer layer, the inner layer is a conductive carbon layer, and the outer layer is a zirconium oxide layer.
2. A preparation method of a lithium titanate composite material is characterized by comprising the following steps: firstly, coating a carbon layer on the surface of cerium-nitrogen-doped lithium titanate to obtain a composite material A, and then coating a zirconium oxide layer on the surface of the composite material A.
3. The method of preparing a lithium titanate composite material according to claim 2, wherein the cerium, nitrogen-doped lithium titanate is obtained by a preparation method comprising the steps of: uniformly mixing a titanium source, a lithium source, a cerium source and a nitrogen source, and calcining; the titanium source is titanium dioxide; the lithium source is lithium carbonate and/or lithium oxalate.
4. The method for preparing a lithium titanate composite material according to claim 3, wherein the nitrogen source is selected from one or any combination of ammonia, aniline, urea, pyrrole and thiophene.
5. The method of preparing a lithium titanate composite material according to claim 4, wherein the cerium source is cerium chloride; the lithium source is lithium carbonate; the ratio of the mass of the cerium chloride to the mass of the nitrogen source to the sum of the mass of the titanium dioxide and the lithium carbonate is (1-5): 0.5-2): 100.
6. The method for preparing a lithium titanate composite material as claimed in any one of claims 2 to 5, wherein the method for coating a carbon layer on the surface of cerium-nitrogen-doped lithium titanate comprises the steps of: uniformly mixing cerium, nitrogen-doped lithium titanate, a binder and a conductive agent, and carrying out carbonization treatment; the binder is asphalt.
7. The method for preparing a lithium titanate composite material according to claim 6, wherein the asphalt has a softening point of (50 to 300 ℃ C.).
8. The method for preparing a lithium titanate composite material according to claim 6, wherein the conductive agent is selected from one or any combination of conductive carbon black, carbon nanotubes, graphene and vapor grown carbon fibers.
9. The method of preparing a lithium titanate composite material according to any one of claims 2 to 5, wherein the zirconium oxide layer is formed by an atomic vapor deposition method.
10. A method of preparing a lithium titanate composite material as claimed in claim 9, characterized in that the atomic vapor deposition method includes the steps of:
s1, transferring the composite material A to a reaction cavity deposition position;
s2, vacuumizing the evaporator to (10-100) toor, heating the evaporator to (100-600) DEG C, and gasifying the zirconium oxide in the evaporator under the condition;
s3, allowing the gasified zirconia to enter a reaction cavity with a vacuum degree of (5-20) toor in a pulse mode at a flow rate of 50sccm under the driving of nitrogen, adsorbing the zirconia on the surface of the composite material A, and depositing for (1-10) min;
s4, repeating step S3 (1-10) times.
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