CN114744185A - Graphene-coated ternary material and preparation method and application thereof - Google Patents
Graphene-coated ternary material and preparation method and application thereof Download PDFInfo
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 132
- 229910021389 graphene Inorganic materials 0.000 title claims abstract description 130
- 239000000463 material Substances 0.000 title claims abstract description 120
- 238000002360 preparation method Methods 0.000 title claims abstract description 30
- 239000002904 solvent Substances 0.000 claims abstract description 24
- 238000001354 calcination Methods 0.000 claims abstract description 19
- 239000011259 mixed solution Substances 0.000 claims abstract description 9
- 238000000034 method Methods 0.000 claims description 32
- 238000002156 mixing Methods 0.000 claims description 15
- 239000002243 precursor Substances 0.000 claims description 14
- 238000005245 sintering Methods 0.000 claims description 13
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 11
- 229910001416 lithium ion Inorganic materials 0.000 claims description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 10
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 5
- 229910003002 lithium salt Inorganic materials 0.000 claims description 5
- 159000000002 lithium salts Chemical class 0.000 claims description 5
- 238000001132 ultrasonic dispersion Methods 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 claims 1
- 239000011248 coating agent Substances 0.000 abstract description 11
- 238000000576 coating method Methods 0.000 abstract description 11
- 239000007791 liquid phase Substances 0.000 abstract description 6
- 238000003860 storage Methods 0.000 abstract description 5
- 230000000052 comparative effect Effects 0.000 description 18
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 description 10
- 239000002994 raw material Substances 0.000 description 9
- 239000000126 substance Substances 0.000 description 7
- 229910015872 LiNi0.8Co0.1Mn0.1O2 Inorganic materials 0.000 description 6
- 239000007774 positive electrode material Substances 0.000 description 6
- 239000002002 slurry Substances 0.000 description 5
- 238000012360 testing method Methods 0.000 description 5
- 238000013329 compounding Methods 0.000 description 3
- 238000001035 drying Methods 0.000 description 3
- 125000000524 functional group Chemical group 0.000 description 3
- 239000013543 active substance Substances 0.000 description 2
- 238000007580 dry-mixing Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000003792 electrolyte Substances 0.000 description 2
- 229910000000 metal hydroxide Inorganic materials 0.000 description 2
- 150000004692 metal hydroxides Chemical class 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- -1 polyethylene Polymers 0.000 description 2
- 229910021503 Cobalt(II) hydroxide Inorganic materials 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 1
- 229910013716 LiNi Inorganic materials 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000010406 cathode material Substances 0.000 description 1
- SEVNKUSLDMZOTL-UHFFFAOYSA-H cobalt(2+);manganese(2+);nickel(2+);hexahydroxide Chemical compound [OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[Mn+2].[Co+2].[Ni+2] SEVNKUSLDMZOTL-UHFFFAOYSA-H 0.000 description 1
- ASKVAEGIVYSGNY-UHFFFAOYSA-L cobalt(ii) hydroxide Chemical compound [OH-].[OH-].[Co+2] ASKVAEGIVYSGNY-UHFFFAOYSA-L 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 230000005672 electromagnetic field Effects 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 230000008570 general process Effects 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 239000011572 manganese Substances 0.000 description 1
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 125000004430 oxygen atom Chemical group O* 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 1
- 235000013570 smoothie Nutrition 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
- H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
-
- 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
-
- 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
- H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
- H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
-
- 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
-
- 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
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/028—Positive electrodes
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention provides a graphene-coated ternary material and a preparation method and application thereof, wherein the preparation method comprises the following steps: and dissolving the graphene oxide and the ternary material calcined product in a solvent, and calcining the obtained mixed solution to obtain the ternary material coated by the graphene. According to the invention, the graphene oxide and the ternary material calcined product are dispersed in a liquid phase, and after calcination, the graphene oxide is reduced to graphene and uniformly coated on the surface of the ternary material to form the graphene-coated ternary material, so that the problem of nonuniform graphene coating caused by poor graphene dispersibility is solved, and the performances of the ternary material such as rate capability, high-temperature cycle and high-temperature storage are obviously improved.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, relates to a ternary material, and particularly relates to a graphene-coated ternary material and a preparation method and application thereof.
Background
Lithium ion battery positive electrodeResearch and improvement of pole materials have been the focus of research on lithium ion batteries, among which ternary materials (NCM, LiNi)1-x-yCoxMnyO2) The lithium ion battery has the advantages of high discharge capacity, good cycle performance, good thermal stability, good safety and low price, is particularly applied to electric vehicles and large-scale high-capacity and high-power lithium ion batteries for energy storage, and has great significance for solving the problem of energy shortage and environmental pollution. However, the electrochemical performance of the ternary material still needs to be further improved, and in the prior art, the ion conductivity of the ternary material is improved by coating graphene, so that the electrochemical performance of the battery is improved.
CN 110311136a discloses a graphene-coated lithium ion battery ternary positive electrode material, which comprises a solvent, a positive electrode active substance and a slurry containing graphene as raw materials; wherein the weight ratio of the graphene-containing slurry to the positive electrode active material is (0.01-8): the method comprises the following steps of 1, uniformly dispersing graphene among ternary positive electrode material particles, wherein the graphene on the surface of the ternary positive electrode plays a role in fixing O atoms on the surface of the material, so that the structure of the material is stabilized, the decomposition of electrolyte on the surface of the ternary positive electrode is inhibited, and the cycle performance, especially the high-temperature cycle performance, of the material is improved. However, in the disclosed preparation method, graphene is easy to agglomerate and is difficult to uniformly disperse on the surface of the cathode material, and the electrochemical performance of the ternary material cannot be improved on the contrary.
CN 110311113a discloses a graphene-coated lithium ion battery positive electrode material, which is prepared from raw materials including graphene, a lithium source and a precursor of a metal hydroxide; the precursor of the metal hydroxide is a precursor of nickel-cobalt-manganese hydroxide and/or a precursor of cobalt hydroxide, a primary sintered product is prepared by firstly compounding the precursor of the positive electrode material with lithium salt, then the primary sintered product is mixed with graphene, and the graphene is wrapped by adopting a compounding machine compounding mode, but the graphene effective wrapping efficiency of the disclosed method is not high.
CN 110311137a discloses a directional graphene-coated lithium ion battery positive electrode material, which is prepared by mixing and drying a fluorine-containing organic substance, an organic solvent, graphene and a positive electrode active substance mainly by a solvent method mixing and an electromagnetic field drying method.
Based on the above research, a graphene-coated ternary material needs to be provided, and the preparation method of the graphene-coated ternary material can solve the problem of graphene dispersibility, improve the coating effect of graphene on the ternary material, improve the ionic conductivity of the graphene-coated ternary material, and further improve the rate performance, high-temperature cycle, high-temperature storage performance and other performances of the ternary material.
Disclosure of Invention
The invention aims to provide a graphene-coated ternary material and a preparation method and application thereof.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a preparation method of a graphene-coated ternary material, including the following steps:
and dissolving the graphene oxide and the ternary material calcined product in a solvent, and calcining the obtained mixed solution to obtain the ternary material coated by the graphene.
According to the method, the graphene oxide and the ternary material calcined product are dispersed through a liquid phase, so that the graphene oxide and the ternary material calcined product can be uniformly dispersed in a mixed solution, a solvent volatilizes after a liquid phase mixture is calcined, the graphene oxide is reduced into graphene, and the graphene oxide is uniformly coated on the surface of the ternary material calcined product to form the graphene-coated ternary material; by adopting the liquid phase mixing and calcining method, the problem of uneven coating caused by poor graphene dispersibility is solved, and the rate performance, high-temperature circulation, high-temperature storage and other performances of the ternary material are obviously improved.
Preferably, the means of dissolving in the solvent comprises ultrasonic dispersion.
Preferably, the solvent comprises water and/or N-methylpyrrolidone, preferably water.
Preferably, the graphene oxide is prepared by a Hummer method.
The preparation method of graphene oxide in the field is generally a Brodie method, a Staudenmaier method and a Hummer method, and the graphene oxide prepared by different methods has different types and contents of functional groups.
The graphene oxide prepared by the Hummer method has multiple types of functional groups, is simple and easy to prepare, and has a good combination effect when being compounded with a ternary material.
Preferably, the calcination temperature is 100-900 deg.C, such as 100 deg.C, 200 deg.C, 300 deg.C, 400 deg.C, 500 deg.C, 600 deg.C, 700 deg.C, 800 deg.C or 900 deg.C, but not limited to the recited values, and other values not recited in the range of values are equally applicable.
Preferably, the calcination is carried out for a period of time of 1 to 48 hours, for example, 1 hour, 10 hours, 15 hours, 20 hours, 25 hours, 30 hours, 35 hours, 40 hours, 45 hours or 48 hours, but not limited to the recited values, and other values not recited in the numerical ranges are also applicable.
Preferably, the mass ratio of the total mass of the ternary material calcined product and the graphene oxide to the solvent is (0.001-90): (10-99.999), and may be, for example, 0.001:99.999, 10:90, 30:70, 50:50 or 90:10, but is not limited to the enumerated values, and other values not enumerated within the numerical range are equally applicable, preferably (45-90): (10-55).
Preferably, the mass ratio of the ternary material calcined product to the graphene oxide is (60-99.9999): (0.0001-40), for example, 60:40, 70:30, 80:20, 90:10 or 99.9999:0.0001, but not limited to the enumerated values, and other non-enumerated values in the numerical range are also applicable, preferably (60-85): (15-40).
Preferably, the ternary material calcined product is obtained by mixing a ternary material precursor and a lithium salt and sintering.
Preferably, the sintering temperature is 600-1200 deg.C, and may be, for example, 600 deg.C, 700 deg.C, 800 deg.C, 900 deg.C, 1000 deg.C, 1100 deg.C or 1200 deg.C, but is not limited to the recited values, and other values not recited within the range of values are equally applicable.
Preferably, the sintering time is 2-24h, for example, 2h, 5h, 10h, 15h, 20h or 24h, but not limited to the recited values, and other values not recited in the range of values are also applicable.
Preferably, the ternary material smoothie comprises any one of Ni33, Ni50, Ni60, Ni70, Ni80, Ni90 or Ni99 types or a combination of at least two thereof, typical but non-limiting combinations including a combination of Ni33 and Ni50, a combination of Ni60 and Ni70, or a combination of Ni33 and Ni 90.
The Ni33 refers to the ternary material-calcined product, the Ni content is 33%, and other types of ternary material-calcined products have the same principle.
As a preferable technical scheme of the preparation method, the preparation method comprises the following steps:
ultrasonically dissolving graphene oxide and a ternary material calcined product into a solvent, and calcining the obtained mixed solution at the temperature of 100-900 ℃ for 1-48h to obtain the graphene-coated ternary material;
the solvent comprises water, and the graphene oxide is prepared by a Hummer method;
the mass ratio of the total mass of the ternary material calcined product and the graphene oxide to the solvent is (45-90) to (10-65), and the mass ratio of the ternary material calcined product to the graphene oxide is (60-85) to (15-40);
the ternary material primary sintered product is obtained by mixing a ternary material precursor with lithium salt and sintering at 600-1200 ℃ for 2-24 h.
In a second aspect, the invention provides a graphene-coated ternary material, which is obtained by using the preparation method of the first aspect.
In a third aspect, the present invention provides a lithium ion battery comprising the graphene-coated ternary material according to the second aspect.
Compared with the prior art, the invention has the following beneficial effects:
according to the preparation method, the graphene oxide and the ternary material calcined product are used as preparation raw materials, the liquid phase mixing and calcining method is adopted to prepare the ternary material coated by the graphene, the problem of uneven coating caused by poor graphene dispersibility can be solved, the graphene is uniformly and tightly coated on the surface of the ternary material, and the multiplying power performance, high-temperature circulation, high-temperature storage performance and the like of the ternary material are obviously improved.
Detailed Description
The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
Example 1
The embodiment provides a preparation method of a graphene-coated ternary material, which comprises the following steps:
ultrasonically dissolving graphene oxide and a ternary material calcined product in water, and calcining the obtained mixed solution at 500 ℃ for 30 hours to obtain the ternary material coated by the graphene;
the graphene oxide is prepared by a Hummer method;
the mass ratio of the total mass of the ternary material primary burned product and the graphene oxide to the solvent is 50:50, and the mass ratio of the ternary material primary burned product to the graphene oxide is 70: 30;
the ternary material primary sintered product is obtained by mixing a ternary material precursor and LiOH according to the formula amount and sintering at 900 ℃ for 15 hours; the chemical formula of the ternary material calcined product is LiNi0.8Co0.1Mn0.1O2。
Example 2
The embodiment provides a preparation method of a graphene-coated ternary material, which comprises the following steps:
ultrasonically dissolving graphene oxide and a ternary material calcined product in water, and calcining the obtained mixed solution for 48 hours at 100 ℃ to obtain the ternary material coated by the graphene;
the graphene oxide is prepared by a Hummer method;
the mass ratio of the total mass of the ternary material primary burned product and the graphene oxide to the solvent is 90:10, and the mass ratio of the ternary material primary burned product to the graphene oxide is 85: 15;
the ternary material primary sintered product is obtained by mixing a ternary material precursor and LiOH according to the formula amount and sintering at 1200 ℃ for 2 h; the chemical formula of the ternary material calcined product is LiNi0.8Co0.1Mn0.1O2。
Example 3
The embodiment provides a preparation method of a graphene-coated ternary material, which comprises the following steps:
ultrasonically dissolving graphene oxide and a ternary material calcined product in N-methyl pyrrolidone, and calcining the obtained mixed solution at 900 ℃ for 1h to obtain the graphene-coated ternary material;
the graphene oxide is prepared by a Hummer method;
the mass ratio of the total mass of the ternary material primary burned product and the graphene oxide to the solvent is 45:55, and the mass ratio of the ternary material primary burned product to the graphene oxide is 60: 40;
the ternary material primary sintered product is obtained by mixing a ternary material precursor and LiOH according to the formula amount and sintering at 600 ℃ for 24 hours; the chemical formula of the ternary material calcined product is LiNi0.8Co0.1Mn0.1O2。
Example 4
The embodiment provides a preparation method of a graphene-coated ternary material, which is the same as that in embodiment 1 except that the solvent is dissolved by stirring.
Example 5
The embodiment provides a preparation method of a graphene-coated ternary material, which is the same as that in embodiment 1 except that the water and the like are replaced by absolute ethyl alcohol.
Example 6
This example provides a preparation method of a graphene-coated ternary material, which is the same as in example 1 except that the same mass of water is replaced by N-methylpyrrolidone.
Example 7
The embodiment provides a preparation method of a graphene-coated ternary material, which is the same as that in embodiment 1 except that the same mass of graphene oxide prepared by the Hummer method is replaced by that of graphene oxide prepared by the Brodie method.
Comparative example 1
This comparative example provides a ternary material, which is not graphene coated, having the chemical formula LiNi0.8Co0.1Mn0.1O2。
Comparative example 2
The comparative example provides a preparation method of a graphene-coated ternary material, and the method is the same as that in example 1 except that graphene oxide and the like are replaced by graphene.
Comparative example 3
The present comparative example provides a method for preparing a graphene-coated ternary material, the method comprising the steps of:
after the graphene oxide and the ternary material calcined product are dry-mixed, calcining the mixture for 30 hours at 500 ℃ to obtain the ternary material coated by the graphene;
the graphene oxide is prepared by a Hummer method;
the mass ratio of the ternary material primary fired product to the graphene oxide is 70: 30;
the ternary material primary sintered product is obtained by mixing a ternary material precursor and LiOH according to the formula amount and sintering at 900 ℃ for 15 hours; the chemical formula of the ternary material calcined product is LiNi0.8Co0.1Mn0.1O2。
Comparative example 4
The present comparative example provides a method for preparing a graphene-coated ternary material, the method comprising the steps of:
after the graphene and the ternary material calcined product are dry-mixed, calcining for 30 hours at 500 ℃ to obtain the ternary material coated by the graphene;
the mass ratio of the ternary material calcined product to the graphene is 70: 30;
the ternary material primary sintered product is obtained by mixing a ternary material precursor and LiOH according to the formula amount and sintering at 900 ℃ for 15 hours; the chemical formula of the ternary material calcined product is LiNi0.8Co0.1Mn0.1O2。
Mixing the graphene-coated ternary material, the conductive carbon black, the conductive carbon tube and the polyvinylidene fluoride obtained in the above examples and comparative examples in a mass ratio of 97.5:1:0.5:1, adding an N-methylpyrrolidone solvent to prepare a slurry, coating the slurry on an aluminum foil, and drying the slurry to obtain a positive plate; and assembling the positive plate, the graphite negative plate, the polyethylene diaphragm and the lithium hexafluorophosphate electrolyte into the soft package battery according to the general process of the lithium ion battery.
The soft package battery is subjected to specific capacity test under the conditions of 0.33C and 4.3V; testing the rate performance under the condition of 3C/0.33C; testing the direct current internal resistance of discharge under the conditions of 25 ℃, 50% SOC and 30s 4C; the results of the above tests were compared with the uncoated ternary material provided in comparative example 1, and the amount of increase in various properties (increase ═ increase/value of comparative example 1 × 100%) was calculated, where negative values in the following table represent the amount of decrease in direct current internal resistance.
The test results are shown in table 1:
TABLE 1
| Specific capacity boost (%) | Multiplying factor increasing amount (%) | DC internal resistance increase (%) | |
| Example 1 | 4.6 | 10.5 | -15.9 |
| Example 2 | 3.9 | 8.1 | -11.5 |
| Example 3 | 3.5 | 7.6 | -10.2 |
| Example 4 | 3.8 | 6.9 | -8.4 |
| Example 5 | 4.3 | 9.5 | -14.7 |
| Example 6 | 4.5 | 9.8 | -14.1 |
| Example 7 | 4.2 | 8.3 | -10.6 |
| Comparative example 1 | / | / | / |
| Comparative example 2 | 2.1 | 5.5 | -7.5 |
| Comparative example 3 | 3.3 | 8.0 | -9.1 |
| Comparative example 4 | 1.8 | 4.7 | -7.2 |
From table 1, the following points can be seen:
(1) as can be seen from examples 1 to 7, the electrochemical performance of the graphene-coated ternary material provided by the present invention can be improved compared to that before coating; from the embodiment 1 and the embodiment 4, the dispersion uniformity of the graphene oxide and the ternary material can be improved by performing ultrasonic dispersion, so that the coating uniformity of the graphene is improved, and the electrochemical performance of the battery is improved; from the examples 1 and 5 to 6, it is known that the solubility of the raw materials in different solvents is different, and the performance of the graphene oxide and the ternary material-calcined product dispersed solvent is affected; as can be seen from examples 1 and 7, the content of functional groups in the graphene oxide prepared by different methods is different, so that the bonding strength between the graphene oxide and the ternary material is different, thereby affecting the electrochemical performance of the battery.
(2) As can be seen from example 1 and comparative example 2, the graphene is used as a substitute for the graphene in the preparation of the raw material, such as graphene oxide, because the graphene has poor dispersibility and is prone to agglomeration, and the graphene is used as the raw material, the coating uniformity of the graphene is reduced, so that the electrochemical performance is significantly reduced compared with that of example 1; as can be seen from example 1 and comparative example 3, the dispersibility of the graphene oxide is reduced compared to example 1 by dry mixing and then calcining the raw materials, which affects the coating uniformity of the graphene, and reduces the electrochemical performance compared to example 1; from example 1 and comparative example 4, dry mixing using graphene as a raw material also has a problem of poor dispersibility.
In summary, the preparation method of the ternary material coated with graphene provided by the invention is characterized in that graphene oxide and a ternary material calcined product are used as preparation raw materials, and a liquid phase mixing and calcining method is adopted to prepare the ternary material coated with graphene, so that the problem of uneven coating caused by poor graphene dispersibility can be solved, graphene is uniformly and tightly coated on the surface of the ternary material, and the performances of the ternary material such as rate capability, high-temperature cycle and high-temperature storage are obviously improved.
The above description is only for the specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are within the protection scope and the disclosure of the present invention.
Claims (10)
1. A preparation method of a graphene-coated ternary material is characterized by comprising the following steps:
and dissolving the graphene oxide and the ternary material calcined product in a solvent, and calcining the obtained mixed solution to obtain the ternary material coated by the graphene.
2. The method of claim 1, wherein the solvent-dissolving means comprises ultrasonic dispersion;
preferably, the solvent comprises water and/or N-methylpyrrolidone, preferably water.
3. The preparation method according to claim 1 or 2, wherein the graphene oxide is prepared by a Hummer method.
4. The method according to any one of claims 1 to 3, wherein the temperature of the calcination is 100-900 ℃;
preferably, the calcination time is 1 to 48 h.
5. The method according to any one of claims 1 to 4, wherein the mass ratio of the total mass of the ternary material calcined product and graphene oxide to the solvent is (0.001-90): (10-99.999), preferably (45-90): (10-55);
preferably, the mass ratio of the ternary material calcined product to the graphene oxide is (60-99.9999): (0.0001-40), preferably (60-85): (15-40).
6. The preparation method according to any one of claims 1 to 5, wherein the ternary material calcined product is obtained by mixing a ternary material precursor with a lithium salt and sintering;
preferably, the sintering temperature is 600-1200 ℃;
preferably, the sintering time is 2-24 h.
7. The method of any one of claims 1-6, wherein the ternary material-fired product comprises any one of Ni33, Ni50, Ni60, Ni70, Ni80, Ni90, or Ni99 types, or a combination of at least two thereof.
8. The production method according to any one of claims 1 to 7, characterized by comprising the steps of:
ultrasonically dissolving graphene oxide and a ternary material calcined product into a solvent, and calcining the obtained mixed solution at the temperature of 100-900 ℃ for 1-48h to obtain the graphene-coated ternary material;
the solvent comprises water, and the graphene oxide is prepared by a Hummer method;
the mass ratio of the total mass of the ternary material calcined product and the graphene oxide to the solvent is (45-90) to (10-65), and the mass ratio of the ternary material calcined product to the graphene oxide is (60-85) to (15-40);
the ternary material primary sintered product is obtained by mixing a ternary material precursor with lithium salt and sintering at the temperature of 600-1200 ℃ for 2-24 h.
9. The graphene-coated ternary material is characterized by being prepared by the preparation method according to any one of claims 1 to 8.
10. A lithium ion battery comprising the graphene-coated ternary material of claim 9.
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