CN117317179A - Preparation method of carbon-coated lithium titanate - Google Patents
Preparation method of carbon-coated lithium titanate Download PDFInfo
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- CN117317179A CN117317179A CN202311391023.5A CN202311391023A CN117317179A CN 117317179 A CN117317179 A CN 117317179A CN 202311391023 A CN202311391023 A CN 202311391023A CN 117317179 A CN117317179 A CN 117317179A
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- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 85
- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 85
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 title claims abstract description 84
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 72
- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 67
- 238000002360 preparation method Methods 0.000 title claims abstract description 16
- 238000005245 sintering Methods 0.000 claims abstract description 38
- 239000007787 solid Substances 0.000 claims abstract description 37
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims abstract description 35
- 238000000227 grinding Methods 0.000 claims abstract description 21
- 238000010438 heat treatment Methods 0.000 claims abstract description 10
- 239000003960 organic solvent Substances 0.000 claims abstract description 7
- 239000002904 solvent Substances 0.000 claims abstract description 6
- 238000001035 drying Methods 0.000 claims abstract description 4
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 claims description 31
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 30
- 238000000034 method Methods 0.000 claims description 22
- 238000003756 stirring Methods 0.000 claims description 20
- 239000000843 powder Substances 0.000 claims description 19
- KXGFMDJXCMQABM-UHFFFAOYSA-N 2-methoxy-6-methylphenol Chemical compound [CH]OC1=CC=CC([CH])=C1O KXGFMDJXCMQABM-UHFFFAOYSA-N 0.000 claims description 15
- 239000003822 epoxy resin Substances 0.000 claims description 15
- 229920001568 phenolic resin Polymers 0.000 claims description 15
- 229920000647 polyepoxide Polymers 0.000 claims description 15
- 239000005011 phenolic resin Substances 0.000 claims description 9
- 238000002604 ultrasonography Methods 0.000 claims description 5
- 239000006185 dispersion Substances 0.000 claims description 4
- 238000003763 carbonization Methods 0.000 abstract description 9
- 239000011248 coating agent Substances 0.000 abstract description 8
- 238000000576 coating method Methods 0.000 abstract description 8
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 abstract description 5
- 230000000694 effects Effects 0.000 abstract description 5
- 229910001416 lithium ion Inorganic materials 0.000 abstract description 5
- 239000011247 coating layer Substances 0.000 abstract description 4
- 239000011148 porous material Substances 0.000 abstract description 3
- 239000000463 material Substances 0.000 description 30
- 238000001816 cooling Methods 0.000 description 16
- 238000009210 therapy by ultrasound Methods 0.000 description 15
- 239000002243 precursor Substances 0.000 description 11
- 230000008569 process Effects 0.000 description 8
- 239000005007 epoxy-phenolic resin Substances 0.000 description 6
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 5
- 230000005611 electricity Effects 0.000 description 5
- 239000011521 glass Substances 0.000 description 5
- 239000007788 liquid Substances 0.000 description 5
- 238000003760 magnetic stirring Methods 0.000 description 5
- 230000014759 maintenance of location Effects 0.000 description 5
- 239000004570 mortar (masonry) Substances 0.000 description 5
- 229910002804 graphite Inorganic materials 0.000 description 4
- 239000010439 graphite Substances 0.000 description 4
- 230000009471 action Effects 0.000 description 3
- 238000009831 deintercalation Methods 0.000 description 3
- 238000002156 mixing Methods 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 2
- 239000002033 PVDF binder Substances 0.000 description 2
- 239000010406 cathode material Substances 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 238000009830 intercalation Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- -1 polypropylene Polymers 0.000 description 2
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 2
- 238000005303 weighing Methods 0.000 description 2
- XOJVVFBFDXDTEG-UHFFFAOYSA-N Norphytane Natural products CC(C)CCCC(C)CCCC(C)CCCC(C)C XOJVVFBFDXDTEG-UHFFFAOYSA-N 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- 239000006230 acetylene black Substances 0.000 description 1
- 239000011149 active material Substances 0.000 description 1
- 238000013019 agitation Methods 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 230000002238 attenuated effect Effects 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000005253 cladding Methods 0.000 description 1
- 239000006258 conductive agent Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 210000001787 dendrite Anatomy 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 230000002687 intercalation Effects 0.000 description 1
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 description 1
- 229910052808 lithium carbonate Inorganic materials 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000002441 reversible effect Effects 0.000 description 1
- 239000000523 sample Substances 0.000 description 1
- 238000004513 sizing Methods 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 238000003746 solid phase reaction Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000001291 vacuum drying Methods 0.000 description 1
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
- H01M4/366—Composites as layered products
-
- 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)
- Composite Materials (AREA)
- Inorganic Chemistry (AREA)
- Inorganic Compounds Of Heavy Metals (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The application relates to the field of lithium ion batteries and discloses a preparation method of carbon-coated lithium titanate. According to the preparation method, lithium titanate, a carbon source and conductive carbon black are uniformly dispersed in an organic solvent, and the solvent is volatilized by heating to form gel-like solid; and then drying, grinding and sintering the gel-like solid to obtain the carbon-coated lithium titanate. When the preparation method is used for carbon coating of lithium titanate, the conductive carbon black is used for assisting carbonization of a carbon source, so that the carbon coating effect is improved, more pores of the carbon coating layer are formed, and the carbonization is more complete; the prepared carbon-coated lithium titanate can have higher performance at a high multiplying power of 5C, reduce capacity attenuation and have higher conductivity.
Description
Technical Field
The application relates to the field of lithium ion batteries, in particular to a preparation method of carbon-coated lithium titanate.
Background
Lithium ion batteries are currently widely used in electronic products and power automobiles. Currently, the most widely used cathode material is graphite, but the graphite cathode has a low charge-discharge voltage platform, so that defects such as lithium dendrites can be generated to pierce through a diaphragm, thereby bringing about a safety problem, and researchers are actively developing new cathode materials to replace the graphite cathode.
Compared with graphite, lithium titanate has great advantages that the deintercalation of lithium ions in lithium titanate is reversible, and the crystal form of lithium ions is not changed in the process of intercalating and deintercalating lithium titanate, and the volume change is less than 1%, so the lithium titanate is also called as a zero strain material. Due to the zero strain property of the lithium titanate, the lithium titanate can avoid the structural damage caused by the back and forth expansion of the electrode material in the charge and discharge cycle, thereby improving the cycle performance and the service life of the electrode.
However, since lithium titanate has low conductivity, it has serious heavy current discharge electrode, and has poor performance at high magnification, and lithium titanate has rapid specific capacity decay.
Disclosure of Invention
In view of the foregoing, an object of the present application is to provide a method for preparing carbon-coated lithium titanate, so that the carbon-coated lithium carbonate prepared by the process has higher performance at high magnification, and reduces capacity fade.
In order to solve the above technical problems/achieve the above objects or at least partially solve the above technical problems/achieve the above objects, there is provided a method for preparing carbon-coated lithium titanate, comprising:
uniformly dispersing lithium titanate, a carbon source and conductive carbon black in an organic solvent, and heating to volatilize the solvent to form gel-like solid;
and drying, grinding and sintering the gel-like solid to obtain the carbon-coated lithium titanate.
Alternatively, the conductive carbon black is used in an amount of 1.0 to 2.3% based on the total weight of lithium titanate and carbon source.
Optionally, the mass ratio of the lithium titanate to the carbon source is more than or equal to 5:1.
Further alternatively, the carbon source includes an epoxy resin and a phenolic resin.
Optionally, the organic solvent comprises isopropanol and/or ethanol.
Optionally, the uniform dispersion is achieved by ultrasound and/or stirring.
Optionally, the sintering comprises two stages of low temperature pre-sintering and high temperature sintering; further optionally, grinding the solid powder formed by the presintered material after the low-temperature presintering.
Optionally, the low temperature pre-sintering temperature is 300-500 ℃.
Optionally, the high temperature sintering temperature is 700-900 ℃.
When the preparation method is used for carbon coating of lithium titanate, the conductive carbon black is used for assisting carbonization of a carbon source, so that the carbon coating effect is improved, more pores of the carbon coating layer are formed, and the carbonization is more complete; the prepared carbon-coated lithium titanate can have higher performance at a high multiplying power of 5C, reduce capacity attenuation and have higher conductivity.
Drawings
FIG. 1 shows the resistivity comparison of pole pieces prepared from the carbon coated lithium titanate material of example 1 and the original lithium titanate material; lto+c represents the carbon-coated lithium titanate material of example 1, LTO represents the original lithium titanate material;
FIG. 2 shows the comparative charge gram capacity at 5C rate for the buckling electricity prepared from the carbon-coated lithium titanate material of example 1 and the original lithium titanate material; lto+c represents the carbon-coated lithium titanate material of example 1, LTO represents the original lithium titanate material;
FIG. 3 shows the comparative charge gram capacity at 10C rate for the buckling electricity prepared from the carbon-coated lithium titanate material of example 1 and the original lithium titanate material; lto+c represents the carbon-coated lithium titanate material of example 1, LTO represents the original lithium titanate material;
FIG. 4 is a graph showing the capacity comparison of the buckling electricity prepared from the carbon-coated lithium titanate material of example 1 and the original lithium titanate material after 100 weeks of 5C current charge-discharge cycle; lto+c represents the carbon-coated lithium titanate material of example 1, LTO represents the original lithium titanate material.
Detailed Description
The application discloses a preparation method of carbon-coated lithium titanate, and a person skilled in the art can refer to the content of the application and appropriately improve the technological parameters. It is expressly noted that all such similar substitutions and modifications will be apparent to those skilled in the art, and are deemed to be included herein. The products, processes and applications described herein have been described in terms of preferred embodiments, and it will be apparent to those skilled in the relevant art that variations and suitable alterations and combinations of the preparation methods described herein can be made to practice and use the technology without departing from the spirit and scope of the application. It will be apparent that the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are within the scope of the present application based on the embodiments herein.
It should be noted that, in this document, relational terms such as "first" and "second," "step 1" and "step 2," and "(1)" and "(2)" and the like, if any, are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element. Meanwhile, the embodiments and features in the embodiments in the present application may be combined with each other without conflict.
In this application, to the relatively poor problem of present lithium titanate performance under high multiplying power condition, adopt conductive carbon black to carry out supplementary carbonization to the carbon source, and then improve the structure of carbon coating, promote the electrochemical performance of carbon cladding lithium titanate material, specifically include:
uniformly dispersing lithium titanate, a carbon source and conductive carbon black in an organic solvent, and heating to volatilize the solvent to form gel-like solid;
and drying, grinding and sintering the gel-like solid to obtain the carbon-coated lithium titanate.
In certain embodiments of the present application, the conductive carbon black is present in an amount of 1.0 to 2.3% based on the total weight of lithium titanate and carbon source; the treated group using conductive carbon black remained at a capacity retention of 90% or more after 100 weeks of 5C cycle, compared to the treated group without conductive carbon black; in other embodiments of the present application, the conductive carbon black is used in an amount of 1.5 to 1.7%, for example 1.67%, based on the total weight of lithium titanate and carbon source. The capacity retention was higher than 95% after a 5C cycle of 100 weeks in the treatment group at this ratio range, with higher performance and lower resistivity than in the treatment group at other ratio ranges.
In certain embodiments of the application, ash detection results after high-temperature sintering of the conductive carbon black prove that the conductive carbon black does not participate in the carbonization process of a carbon source in an experiment, but only plays a role in carbonization assistance, so that the carbon coating effect is improved.
In certain embodiments of the present application, the mass ratio of lithium titanate to carbon source is ≡5:1, such as 5:1, 6:1, 7:1, 10:1, etc. In other embodiments of the present application, the carbon source comprises an epoxy resin and a phenolic resin in a mass ratio of (1-5): (1-5), e.g., 1:1, 2:1, 1:2, 3:2, 2:3, 1:5, 5:1, etc.
In certain embodiments of the present application, the organic solvent comprises isopropyl alcohol and/or ethanol. In other embodiments of the present application, in order to obtain a more uniform carbon coating layer, the preparation method comprises mixing and dispersing isopropyl alcohol and lithium titanate, then adding conductive carbon black and ethanol, mixing and dispersing, and finally adding a solution of epoxy resin and phenolic resin in a mass ratio of 1:1 dropwise.
In certain embodiments of the present application, the uniform dispersion is achieved by ultrasound and/or agitation, so as to further increase the dispersion state of each material and improve the final carbon coating effect. In other embodiments of the present application, the frequency of the ultrasound is 50-150Hz and the ultrasound time is 1-30min, such as 100Hz and 10min; the stirring may be performed manually or by using a magnetic stirrer at a stirring speed of 100-500r/min for 10-60min, such as 300r/min and 400r/min, and 10min and 30min.
In certain embodiments of the present application, the solvent is volatilized by heating to 80 ℃ with stirring until a gelatinous solid is formed.
In certain embodiments of the present application,in order to fully ensure the solid phase reaction of the raw materials, the sintering comprises two stages of low-temperature pre-sintering and high-temperature sintering; wherein the low temperature pre-sintering temperature is 300-500 ℃, such as 300 ℃, 350 ℃,400 ℃, 450 ℃,500 ℃ and the like, and the pre-sintering time is usually 1-5h, such as 3h and the like. In other embodiments of the present application, to ensure the sufficiency and uniformity of high temperature sintering, the solid powder (Li 4 Ti 5 O 12 /C precursor) is milled.
In certain embodiments of the present application, the high temperature sintering is at a temperature of 700-900 ℃, e.g., 700 ℃, 750 ℃,800 ℃, 850 ℃,900 ℃, etc., and the high temperature sintering is typically performed for a time of 5-10 hours, e.g., 6 hours, etc.
Compared with the original lithium titanate, the conductivity of the carbon-coated lithium titanate prepared by the preparation method is improved by 12%, the discharge capacity of the electricity-buckling 5C is improved by 27%, the discharge capacity of the 10C is improved by 130%, and the retention rate of the 5C in 100 weeks is improved by 140%.
In each of the comparative experiments provided herein, unless specifically indicated otherwise, other experimental conditions, materials, etc. were consistent for comparison, except for the differences noted in each group. The experimental materials and reagents used in the examples were obtained from commercial sources unless otherwise specified.
The following further describes a preparation method of the carbon-coated lithium titanate provided in the present application.
Example 1:
15+ -0.0005 g of lithium titanate, 3+ -0.0005 g of a 1:1 solution of epoxy resin and phenolic resin, 0.3+ -0.0005 g (1.67%) of conductive carbon black (SP), 30g of isopropanol and 200g of ethanol are weighed;
taking a 400mL beaker, adding 30g of isopropanol, adding 15g of lithium titanate into an ultrasonic cleaner, performing 100Hz ultrasonic treatment for 10min, and stirring by using a glass rod;
0.3g of conductive carbon black is added, ultrasonic treatment is carried out for 10min, 200g of ethanol is added, and ultrasonic treatment is continued for 10min.
Adding a rotor, placing the beaker into a constant-temperature magnetic stirring pot, rotating for 10min at 400r/min, reducing the speed to 300r/min after 10min, and dropwise adding 3g of the solution of the epoxy resin and the phenolic resin into the solution;
stirring for 30min after the liquid adding is completed;
heating to 80deg.C, stirring until the solution is substantially volatilized, and forming gel solid;
transferring the gel solid to a surface dish, baking at 100deg.C for 6 hr to dry, and cooling to room temperature;
transferring the dried solid powder into agate, and grinding for 1h;
transferring the ground solid powder into a muffle furnace, presintering for 3h at 400 ℃, and cooling to room temperature;
the solid powder after pre-sintering (Li 4 Ti 5 O 12 C, transferring the precursor to a mortar for secondary grinding for 30min;
and then Li after secondary grinding 4 Ti 5 O 12 Transferring the precursor/C into a muffle furnace, sintering at 800 ℃ for 6 hours, and cooling to room temperature to obtain the carbon-coated lithium titanate.
Example 2:
15+ -0.0005 g of lithium titanate, 3+ -0.0005 g of a 1:1 solution of epoxy resin and phenolic resin, 0.2+ -0.0005 g (1.11%) of conductive carbon black (SP), 30g of isopropanol and 200g of ethanol are weighed;
taking a 400mL beaker, adding 30g of isopropanol, adding 15g of lithium titanate into an ultrasonic cleaner, performing 100Hz ultrasonic treatment for 10min, and stirring by using a glass rod;
0.2g of conductive carbon black is added, ultrasonic treatment is carried out for 10min, 200g of ethanol is added, and ultrasonic treatment is continued for 10min.
Adding a rotor, placing the beaker into a constant-temperature magnetic stirring pot, rotating for 10min at 400r/min, reducing the speed to 300r/min after 10min, and dropwise adding 3g of the solution of the epoxy resin and the phenolic resin into the solution;
stirring for 30min after the liquid adding is completed;
heating to 80deg.C, stirring until the solution is substantially volatilized, and forming gel solid;
transferring the gel solid to a surface dish, baking at 100deg.C for 6 hr to dry, and cooling to room temperature;
transferring the dried solid powder into agate, and grinding for 1h;
transferring the ground solid powder into a muffle furnace, presintering for 3h at 400 ℃, and cooling to room temperature;
the solid powder after pre-sintering (Li 4 Ti 5 O 12 C, transferring the precursor to a mortar for secondary grinding for 30min;
and then Li after secondary grinding 4 Ti 5 O 12 Transferring the precursor/C into a muffle furnace, sintering at 800 ℃ for 6 hours, and cooling to room temperature to obtain the carbon-coated lithium titanate.
Example 3:
15+ -0.0005 g of lithium titanate, 3+ -0.0005 g of a 1:1 solution of epoxy resin and phenolic resin, 0.4+ -0.0005 g (2.22%) of conductive carbon black (SP), 30g of isopropanol and 200g of ethanol are weighed;
taking a 400mL beaker, adding 30g of isopropanol, adding 15g of lithium titanate into an ultrasonic cleaner, performing 100Hz ultrasonic treatment for 10min, and stirring by using a glass rod;
0.4g of conductive carbon black is added, ultrasonic treatment is carried out for 10min, 200g of ethanol is added, and ultrasonic treatment is continued for 10min.
Adding a rotor, placing the beaker into a constant-temperature magnetic stirring pot, rotating for 10min at 400r/min, reducing the speed to 300r/min after 10min, and dropwise adding 3g of the solution of the epoxy resin and the phenolic resin into the solution;
stirring for 30min after the liquid adding is completed;
heating to 80deg.C, stirring until the solution is substantially volatilized, and forming gel solid;
transferring the gel solid to a surface dish, baking at 100deg.C for 6 hr to dry, and cooling to room temperature;
transferring the dried solid powder into agate, and grinding for 1h;
transferring the ground solid powder into a muffle furnace, presintering for 3h at 400 ℃, and cooling to room temperature;
the solid powder after pre-sintering (Li 4 Ti 5 O 12 C, transferring the precursor to a mortar for secondary grinding for 30min;
and then Li after secondary grinding 4 Ti 5 O 12 Transferring the precursor/C into a muffle furnace, sintering at 800 ℃ for 6 hours, and cooling to room temperature to obtain the carbon-coated lithium titanate.
Example 4:
15+ -0.0005 g of lithium titanate, 3+ -0.0005 g of a 1:1 solution of epoxy resin and phenolic resin, 0.27+ -0.0005 g (1.5%) of conductive carbon black (SP), 30g of isopropanol and 200g of ethanol are weighed;
taking a 400mL beaker, adding 30g of isopropanol, adding 15g of lithium titanate into an ultrasonic cleaner, performing 100Hz ultrasonic treatment for 10min, and stirring by using a glass rod;
0.27g of conductive carbon black is added, the ultrasonic treatment is carried out for 10min, 200g of ethanol is added, and the ultrasonic treatment is continued for 10min.
Adding a rotor, placing the beaker into a constant-temperature magnetic stirring pot, rotating for 10min at 400r/min, reducing the speed to 300r/min after 10min, and dropwise adding 3g of the solution of the epoxy resin and the phenolic resin into the solution;
stirring for 30min after the liquid adding is completed;
heating to 70deg.C, stirring until the solution is substantially volatilized to obtain gel solid;
transferring the gel solid to a surface dish, baking at 100deg.C for 6 hr to dry, and cooling to room temperature;
transferring the dried solid powder into agate, and grinding for 1h;
transferring the ground solid powder into a muffle furnace, presintering for 5h at 300 ℃, and cooling to room temperature;
the solid powder after pre-sintering (Li 4 Ti 5 O 12 C, transferring the precursor to a mortar for secondary grinding for 30min;
and then Li after secondary grinding 4 Ti 5 O 12 Transferring the precursor/C into a muffle furnace, sintering at 700 ℃ for 10 hours, and cooling to room temperature to obtain the carbon-coated lithium titanate.
Example 5:
15+ -0.0005 g of lithium titanate, 3+ -0.0005 g of a 1:1 solution of epoxy resin and phenolic resin, 0.306+ -0.0005 g (1.7%) of conductive carbon black (SP), 30g of isopropanol and 200g of ethanol are weighed;
taking a 400mL beaker, adding 30g of isopropanol, adding 15g of lithium titanate into an ultrasonic cleaner, performing 100Hz ultrasonic treatment for 10min, and stirring by using a glass rod;
0.306g of conductive carbon black is added, ultrasonic treatment is carried out for 10min, 200g of ethanol is added, and ultrasonic treatment is continued for 10min.
Adding a rotor, placing the beaker into a constant-temperature magnetic stirring pot, rotating for 10min at 400r/min, reducing the speed to 300r/min after 10min, and dropwise adding 3g of the solution of the epoxy resin and the phenolic resin into the solution;
stirring for 30min after the liquid adding is completed;
heating to 85deg.C, and stirring until the solution is substantially volatilized to obtain gel solid;
transferring the gel solid to a surface dish, baking at 100deg.C for 6 hr to dry, and cooling to room temperature;
transferring the dried solid powder into agate, and grinding for 1h;
transferring the ground solid powder into a muffle furnace, presintering for 2h at 500 ℃, and cooling to room temperature;
the solid powder after pre-sintering (Li 4 Ti 5 O 12 C, transferring the precursor to a mortar for secondary grinding for 30min;
and then Li after secondary grinding 4 Ti 5 O 12 Transferring the precursor/C into a muffle furnace, sintering at 900 ℃ for 5 hours, and cooling to room temperature to obtain the carbon-coated lithium titanate.
Comparative example:
on the basis of example 1, 200g of ethanol was directly added without adding 0.3g of conductive carbon black (SP) and sonicated, the rest of the procedure was identical to example 1.
Experimental example:
1. conductive carbon black high-temperature sintering ash detection
Taking two crucibles, weighing the two crucibles respectively to be m0, adding m1 (1-2) g of conductive carbon black into the crucibles, sintering at a high temperature of 800 ℃ for 6 hours, cooling to room temperature, weighing the two crucibles to be m2, and calculating ash content (m 2-m 0)/m1×100%, wherein the result is shown in the following table 1:
TABLE 1
| m0/g | m1/g | m2/g | Ash% |
| 20.08263 | 1.68246 | 20.08259 | -0.2％ |
| 21.24616 | 1.06538 | 21.24614 | -0.2％ |
As is clear from the results in table 1, although the conductive carbon black belongs to the conductive agent, the conductive carbon black does not participate in the carbon source during the high-temperature sintering, but only plays an auxiliary role in carbonization, improves the carbon coating effect, changes the conductive carbon black into carbon dioxide at high temperature, forms gas exhaust, increases the pores of the carbon coating layer of the epoxy resin and the phenolic resin, facilitates the intercalation and deintercalation of lithium titanate, and enables the carbonization to be more sufficient.
2. Comparison of electrochemical Properties of examples and comparative examples
And (5) buckling and assembling: mixing the prepared powder material (90 wt%) acetylene black (5 wt%) and polyvinylidene fluoride (PVDF, 5 wt%) and dripping a proper amount of N-methyl pyrrolidone (NMP) solvent, using a double planetary mixer, grinding for at least 40min at 300r/min to obtain uniform black slurry; then black sizing agent is obtained and evenly coated on the aluminum foil current collector; vacuum drying at 80deg.C for 12 hr; finally, the negative plate with the active material loading of 1-2 mg/cm is cut.
And a lithium sheet is used as an anode, a conventional polypropylene diaphragm is used as a diaphragm, lithium hexafluorophosphate is used as electrolyte, and the prepared anode sheet and the CR2032 button half battery are assembled under the condition of a glove box.
Electrochemical properties are shown in table 2:
TABLE 2
As can be seen from the results in table 2, the addition of the conductive carbon black during the preparation process can improve the capacity retention rate of the carbon-coated lithium titanate material at high magnification, avoiding larger capacity attenuation; particularly, when the addition amount of the conductive carbon black is 1.5-1.7% (accounting for the total weight of the lithium titanate and the carbon source), the capacity retention rate is more than 95%, and the specific resistance of the pole piece is lower and the conductivity is better.
3. Example 1 comparison of electrochemical Properties of carbon-coated lithium titanate (LTO+C) and pristine Lithium Titanate (LTO)
According to the above-mentioned electricity buckling assembly mode, the carbon-coated lithium titanate material prepared in example 1 and the original lithium titanate material are assembled into electricity buckling for a plurality of electrochemical performance comparisons, and the results are shown in fig. 1-4;
FIG. 1 shows that the resistivity of the pole piece is tested by a four-probe tester, the resistivity of the pole piece prepared by the material of the example 1 is lower than 8 omega cm, and the resistivity of the original lithium titanate is higher than 8.5 omega cm, which proves that the conductivity of the carbon-coated lithium titanate material prepared by the process of the application is higher;
the results of fig. 2 and 3 show the charge gram capacity results of the buckling at 5C/10C, respectively, and it can be clearly seen from the results of the accompanying drawings that the buckling of the material assembly of example 1 is significantly superior to the original lithium titanate in charge gram capacity;
the results of FIG. 4 show that the buckling current of 5C is used for charging and discharging, the capacity after 100 weeks of circulation, and the results show that the buckling current assembled by the material of example 1 still keeps the capacity above 140mAh/g after 100 weeks of circulation, and the capacity of the original lithium titanate assembled Maillard buckling current is attenuated to about 60mAh/g after 100 weeks of circulation.
The foregoing is merely a specific embodiment of the application to enable one skilled in the art to understand or practice the application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. A method for preparing carbon-coated lithium titanate, comprising:
uniformly dispersing lithium titanate, a carbon source and conductive carbon black in an organic solvent, and heating to volatilize the solvent to form gel-like solid;
and drying, grinding and sintering the gel-like solid to obtain the carbon-coated lithium titanate.
2. The method of claim 1, wherein the conductive carbon black is used in an amount of 1.0 to 2.3% based on the total weight of lithium titanate and carbon source.
3. The preparation method according to claim 1, wherein the mass ratio of the lithium titanate to the carbon source is not less than 5:1.
4. A method of preparation according to any one of claims 1 to 3 wherein the carbon source comprises an epoxy resin and a phenolic resin.
5. The method of claim 1, wherein the organic solvent comprises isopropyl alcohol and/or ethanol.
6. The preparation method according to claim 1, wherein the uniform dispersion is achieved by ultrasound and/or stirring.
7. The method of claim 1, wherein the sintering comprises two stages, low temperature pre-sintering and high temperature sintering.
8. The method according to claim 7, wherein the solid powder formed by the pre-sintering is ground after the low-temperature pre-sintering.
9. The method of claim 7, wherein the low temperature pre-sintering temperature is 300-500 ℃.
10. The method of claim 7, wherein the high temperature sintering is at a temperature of 700-900 ℃.
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