CN114335534A - Lithium cobaltate positive electrode material coated and modified by zirconium lithium phosphate fast ion conductor and preparation method and application thereof - Google Patents
Lithium cobaltate positive electrode material coated and modified by zirconium lithium phosphate fast ion conductor and preparation method and application thereof Download PDFInfo
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- CN114335534A CN114335534A CN202111546529.XA CN202111546529A CN114335534A CN 114335534 A CN114335534 A CN 114335534A CN 202111546529 A CN202111546529 A CN 202111546529A CN 114335534 A CN114335534 A CN 114335534A
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- NPDXHCPLBBTVKX-UHFFFAOYSA-K [Zr+4].P(=O)([O-])([O-])[O-].[Li+] Chemical compound [Zr+4].P(=O)([O-])([O-])[O-].[Li+] NPDXHCPLBBTVKX-UHFFFAOYSA-K 0.000 title claims abstract description 53
- 239000010416 ion conductor Substances 0.000 title claims abstract description 48
- 239000007774 positive electrode material Substances 0.000 title claims abstract description 46
- 238000002360 preparation method Methods 0.000 title claims abstract description 22
- 229910052744 lithium Inorganic materials 0.000 title claims description 94
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims description 86
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims abstract description 15
- 229910001416 lithium ion Inorganic materials 0.000 claims abstract description 14
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 18
- 239000007787 solid Substances 0.000 claims description 18
- 239000000843 powder Substances 0.000 claims description 17
- 150000001875 compounds Chemical class 0.000 claims description 12
- IIPYXGDZVMZOAP-UHFFFAOYSA-N lithium nitrate Chemical compound [Li+].[O-][N+]([O-])=O IIPYXGDZVMZOAP-UHFFFAOYSA-N 0.000 claims description 12
- 239000011248 coating agent Substances 0.000 claims description 11
- 238000000576 coating method Methods 0.000 claims description 11
- 238000003756 stirring Methods 0.000 claims description 11
- 238000000034 method Methods 0.000 claims description 10
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims description 9
- 238000010438 heat treatment Methods 0.000 claims description 9
- 239000000203 mixture Substances 0.000 claims description 9
- 229910052698 phosphorus Inorganic materials 0.000 claims description 9
- 239000011574 phosphorus Substances 0.000 claims description 9
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 claims description 8
- 238000005245 sintering Methods 0.000 claims description 8
- 229910052726 zirconium Inorganic materials 0.000 claims description 8
- 239000002245 particle Substances 0.000 claims description 7
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 claims description 6
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 6
- LFVGISIMTYGQHF-UHFFFAOYSA-N ammonium dihydrogen phosphate Chemical compound [NH4+].OP(O)([O-])=O LFVGISIMTYGQHF-UHFFFAOYSA-N 0.000 claims description 6
- 229910000387 ammonium dihydrogen phosphate Inorganic materials 0.000 claims description 6
- 239000003792 electrolyte Substances 0.000 claims description 6
- 235000019837 monoammonium phosphate Nutrition 0.000 claims description 6
- 239000002904 solvent Substances 0.000 claims description 6
- 239000000725 suspension Substances 0.000 claims description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 6
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 claims description 5
- 239000003960 organic solvent Substances 0.000 claims description 5
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 claims description 4
- 239000004743 Polypropylene Substances 0.000 claims description 4
- OERNJTNJEZOPIA-UHFFFAOYSA-N zirconium nitrate Chemical compound [Zr+4].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O OERNJTNJEZOPIA-UHFFFAOYSA-N 0.000 claims description 4
- 239000002033 PVDF binder Substances 0.000 claims description 3
- 229910052782 aluminium Inorganic materials 0.000 claims description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 3
- 239000006258 conductive agent Substances 0.000 claims description 3
- 239000011888 foil Substances 0.000 claims description 3
- -1 polypropylene Polymers 0.000 claims description 3
- 229920001155 polypropylene Polymers 0.000 claims description 3
- MNNHAPBLZZVQHP-UHFFFAOYSA-N diammonium hydrogen phosphate Chemical compound [NH4+].[NH4+].OP([O-])([O-])=O MNNHAPBLZZVQHP-UHFFFAOYSA-N 0.000 claims description 2
- 229910000388 diammonium phosphate Inorganic materials 0.000 claims description 2
- 235000019838 diammonium phosphate Nutrition 0.000 claims description 2
- 238000000227 grinding Methods 0.000 claims description 2
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 claims description 2
- 229910052808 lithium carbonate Inorganic materials 0.000 claims description 2
- 229910001386 lithium phosphate Inorganic materials 0.000 claims description 2
- INHCSSUBVCNVSK-UHFFFAOYSA-L lithium sulfate Inorganic materials [Li+].[Li+].[O-]S([O-])(=O)=O INHCSSUBVCNVSK-UHFFFAOYSA-L 0.000 claims description 2
- 239000011259 mixed solution Substances 0.000 claims description 2
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 2
- RBTVSNLYYIMMKS-UHFFFAOYSA-N tert-butyl 3-aminoazetidine-1-carboxylate;hydrochloride Chemical compound Cl.CC(C)(C)OC(=O)N1CC(N)C1 RBTVSNLYYIMMKS-UHFFFAOYSA-N 0.000 claims description 2
- TWQULNDIKKJZPH-UHFFFAOYSA-K trilithium;phosphate Chemical compound [Li+].[Li+].[Li+].[O-]P([O-])([O-])=O TWQULNDIKKJZPH-UHFFFAOYSA-K 0.000 claims description 2
- DUNKXUFBGCUVQW-UHFFFAOYSA-J zirconium tetrachloride Chemical compound Cl[Zr](Cl)(Cl)Cl DUNKXUFBGCUVQW-UHFFFAOYSA-J 0.000 claims description 2
- ZXAUZSQITFJWPS-UHFFFAOYSA-J zirconium(4+);disulfate Chemical compound [Zr+4].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O ZXAUZSQITFJWPS-UHFFFAOYSA-J 0.000 claims description 2
- 238000002156 mixing Methods 0.000 claims 2
- 229910001290 LiPF6 Inorganic materials 0.000 claims 1
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 claims 1
- 239000010406 cathode material Substances 0.000 abstract description 17
- 230000014759 maintenance of location Effects 0.000 abstract description 12
- 150000002641 lithium Chemical class 0.000 abstract description 7
- 230000009286 beneficial effect Effects 0.000 abstract 1
- 239000000243 solution Substances 0.000 description 20
- 239000003153 chemical reaction reagent Substances 0.000 description 17
- 230000000052 comparative effect Effects 0.000 description 14
- 239000010405 anode material Substances 0.000 description 7
- 239000013078 crystal Substances 0.000 description 5
- 238000009792 diffusion process Methods 0.000 description 5
- 238000011065 in-situ storage Methods 0.000 description 4
- WXKDNDQLOWPOBY-UHFFFAOYSA-N zirconium(4+);tetranitrate;pentahydrate Chemical compound O.O.O.O.O.[Zr+4].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O WXKDNDQLOWPOBY-UHFFFAOYSA-N 0.000 description 4
- 238000002441 X-ray diffraction Methods 0.000 description 3
- 238000011031 large-scale manufacturing process Methods 0.000 description 3
- 230000001351 cycling effect Effects 0.000 description 2
- 239000008367 deionised water Substances 0.000 description 2
- 229910021641 deionized water Inorganic materials 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 230000000630 rising effect Effects 0.000 description 2
- 238000007086 side reaction Methods 0.000 description 2
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 1
- 238000003917 TEM image Methods 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910017052 cobalt Inorganic materials 0.000 description 1
- 239000010941 cobalt Substances 0.000 description 1
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 239000002803 fossil fuel Substances 0.000 description 1
- SNKMVYBWZDHJHE-UHFFFAOYSA-M lithium;dihydrogen phosphate Chemical compound [Li+].OP(O)([O-])=O SNKMVYBWZDHJHE-UHFFFAOYSA-M 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 238000001757 thermogravimetry curve Methods 0.000 description 1
- 238000011282 treatment Methods 0.000 description 1
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Abstract
The invention discloses a zirconium phosphate lithium fast ion conductor coated and modified lithium cobaltate cathode material, and relates to the technical field of lithium ion battery cathode materials. The invention also provides a preparation method and application of the cathode material. The invention has the beneficial effects that: the positive electrode material has excellent rate performance and circulation stability under the condition of higher charging voltage of 4.6V, the first discharge capacity can reach 217.5mAh/g under the conditions of 3.0-4.6V and 0.1C, and the capacity retention rate can reach 77.8 percent after circulation for 40 circles; under 0.5C, the first discharge capacity can reach 214.9mAh/g, and after 100 cycles, the capacity retention rate reaches 75.1%.
Description
Technical Field
The invention relates to the technical field of lithium ion battery anode materials, in particular to a zirconium phosphate lithium fast ion conductor coated and modified lithium cobaltate anode material and a preparation method and application thereof.
Background
The lithium ion battery is a light, rechargeable and high-energy-density battery, and is widely applied to mobile phones, notebook computers and electric vehicles. They can also be used to store energy sources such as solar and wind, making it possible to withdraw fossil fuels from modern society. The positive electrode material is one of the main factors limiting the specific capacity and energy density of the lithium ion battery. Lithium cobaltate is one of the main anode materials, and has the advantages of high discharge platform, large specific capacity, high energy density, simple synthesis process and the like. However, the charging voltage of the conventional lithium cobaltate is limited to 4.3V, and as the demands of various electronic devices and electric vehicles on the capacity and energy density are continuously increased, the upper cut-off voltage of the lithium cobaltate is increased to achieve better performance. However, as the cut-off voltage on lithium cobaltate increases, the capacity decays rapidly during cycling of the cell. Specifically, lithium cobaltate undergoes a harmful phase change during charging, a volume change increases, so that crystal grains are stressed and deformed, and a side reaction occurs between the surface of lithium cobaltate and an electrolyte, resulting in dissolution of cobalt and an increase in resistance. In order to improve the cycling stability of lithium cobaltate under high pressure, strategies such as ion doping and surface coating can be adopted. The surface coating can directly inhibit the contact of the lithium cobaltate surface and the electrolyte, inhibit side reaction and improve the circulation stability.
The fast ion conductor modified lithium ion battery positive electrode material lithium cobaltate as in patent application publication No. CN 101969110 a, but its charging voltage is limited to 4.4V and the first capacity is only 166.5 mAh/g.
Disclosure of Invention
The invention aims to provide a zirconium phosphate lithium fast ion conductor coated and modified lithium cobaltate cathode material with good cycle stability and rate capability under high charging voltage, a preparation method and application thereof.
The invention solves the technical problems through the following technical means:
the lithium cobaltate positive electrode material is modified by coating a zirconium lithium phosphate fast ion conductor, the zirconium lithium phosphate fast ion conductor is coated on the surface of the lithium cobaltate positive electrode material and forms particles, the mass of the zirconium lithium phosphate fast ion conductor is 0.5-5 wt%, the particle size range of the positive electrode material is 6-8 mu m, and the shape of the positive electrode material is similar to a sphere.
The principle of the invention is as follows: the zirconium phosphate lithium is a fast ion conductor and has high ion conductivity and electronic conductivity, the zirconium phosphate lithium is coated on the surface of the lithium cobaltate to improve the diffusion rate of lithium ions, so that the lithium ions can be rapidly embedded and separated, the multiplying power performance of the lithium cobaltate under 4.6V is improved, the zirconium phosphate lithium is coated on the surface of the lithium cobaltate to inhibit the corrosion of electrolyte to the lithium cobaltate, and the impedance of the lithium cobaltate in the circulation process is reduced. The volume change of lithium cobaltate in the circulation process is reduced by coating with the lithium zirconium phosphate, the stress among crystal grains is reduced, the generation of cracks is inhibited, the structural stability is maintained, and the circulation stability is greatly increased.
Has the advantages that: compared with the prior art, the cathode material has excellent rate performance and circulation stability under a higher charging voltage of 4.6V, the first discharge capacity can reach 217.5mAh/g under 3.0-4.6V and 0.1C, and the capacity retention rate can reach 77.8% after circulation for 40 circles; under 0.5C, the first discharge capacity can reach 214.9mAh/g, and after 100 cycles, the capacity retention rate reaches 75.1%.
The preparation method of the lithium cobaltate positive electrode material coated and modified by the zirconium phosphate lithium fast ion conductor comprises the following steps:
(1) dissolving a lithium source compound, a zirconium source compound and a phosphorus source compound in an organic solvent or water according to a molar ratio, and slowly stirring until the solid is completely dissolved to form a milky suspension; adding lithium cobaltate powder, stirring and heating until the solvent is volatilized to leave a solid agglomerate;
(2) grinding the solid agglomerate obtained in the step (1) to obtain black and uniform powder;
(3) and (3) sintering the powder obtained in the step (2) at a high temperature to obtain the lithium cobaltate positive electrode material coated by the zirconium phosphate lithium fast ion conductor.
Has the advantages that: the method has low cost and simple preparation process, and is suitable for large-scale production.
The invention can reduce the influence of water on the battery performance by adopting the organic solvent without introducing water.
Preferably, the lithium source compound is selected from one or more of lithium sulfate, lithium carbonate, lithium nitrate and lithium hydroxide; the zirconium source compound is selected from one or more of zirconium chloride, zirconium nitrate and zirconium sulfate; the phosphorus source compound is selected from one or more of diammonium hydrogen phosphate, ammonium dihydrogen phosphate and lithium phosphate.
Has the advantages that: compared with the prior art that lithium is wasted due to the fact that lithium dihydrogen phosphate is used as a phosphorus source, the lithium-ion battery can solve the problem.
Preferably, the organic solvent is one or more of methanol, ethanol, ethylene glycol and isopropanol.
Preferably, the mass ratio of the zirconium phosphate lithium fast ion conductor to the lithium cobaltate powder is 0.1-5: 100.
Has the advantages that: at this ratio, the coating effect is best.
Preferably, the stirring and heating temperature is 50-100 ℃, and the stirring time is 2-8 h.
Preferably, the temperature rise rate of the sintering is 1-5 ℃/min, the temperature is raised to 600-1000 ℃, the temperature is kept for 2-8 h, and the sintering atmosphere is air.
Has the advantages that: the temperature rising rate and the sintering time were controlled so that the lithium zirconium phosphate could be successfully coated on the surface of the lithium cobaltate without changing the crystal structure inside the lithium cobaltate.
Preferably, the temperature is increased to 800-1000 ℃.
The lithium cobaltate cathode material coated and modified by the zirconium phosphate lithium fast ion conductor is applied to a lithium ion battery.
Has the advantages that: the lithium cobaltate anode material coated by the zirconium lithium phosphate fast ionic conductor and the metallic lithium cathode are assembled into a half-cell, the first discharge capacity can reach 217.5mAh/g under 3.0-4.6V and 0.1C, and the capacity retention rate can reach 77.8 percent after 40 cycles; the first discharge capacity can reach 214.9mAh/g under 0.5C, and after circulation for 100 circles, the capacity retention rate can reach 75.1%; under the multiplying power of 0.1C, 0.5C, 1C, 2C and 5C respectively, the first discharge capacity can reach 212.3mAh/g, 195.1mAh/g, 170.7mAh/g, 141.5mAh/g and 80.7mAh/g respectively, which shows that the lithium cobaltate anode material coated by the zirconium lithium phosphate fast ion conductor also has excellent cycle stability and multiplying power performance under the high pressure of 4.6V.
Preferably, the positive electrode material, the conductive agent and the polyvinylidene fluoride are mixed and coated on an aluminum foil to prepare a positive electrode plate, lithium metal is used as a negative electrode, polypropylene is used as a diaphragm, and LiPF is added6And dissolving the mixture in a mixed solution of EC, DMC and EMC in a volume ratio of 1:1:1 to form an electrolyte, and assembling the battery.
The invention has the advantages that: the cathode material has excellent rate performance and circulation stability under 4.6V, and the first discharge capacity can reach 217.5mAh/g under 3.0-4.6V and 0.1C.
The method has low cost and simple preparation process, and is suitable for large-scale production.
When the mass ratio of the zirconium lithium phosphate fast ion conductor to the lithium cobaltate powder is 0.1-5: 100, the coating effect is best.
The temperature rising rate and the sintering time were controlled so that the lithium zirconium phosphate could be successfully coated on the surface of the lithium cobaltate without changing the crystal structure inside the lithium cobaltate.
The lithium cobaltate anode material coated by the zirconium lithium phosphate fast ionic conductor and the metallic lithium cathode are assembled into a half-cell, the first discharge capacity can reach 217.5mAh/g under 3.0-4.6V and 0.1C, and the capacity retention rate can reach 77.8 percent after 40 cycles; the first discharge capacity can reach 214.9mAh/g under 0.5C, and after circulation for 100 circles, the capacity retention rate can reach 75.1%; under the multiplying power of 0.1C, 0.5C, 1C, 2C and 5C respectively, the first discharge capacity can reach 212.3mAh/g, 195.1mAh/g, 170.7mAh/g, 141.5mAh/g and 80.7mAh/g respectively, which shows that the lithium cobaltate anode material coated by the zirconium lithium phosphate fast ion conductor also has excellent cycle stability and multiplying power performance under the high pressure of 4.6V.
Drawings
FIG. 1 is an XRD diagram of a lithium cobaltate cathode material coated with a zirconium phosphate lithium fast ion conductor obtained in example 2 of the present invention;
FIG. 2 is SEM images of the lithium cobaltate positive electrode material coated with the zirconium phosphate lithium fast ion conductor and the uncoated lithium cobaltate positive electrode material obtained in example 2 of the present invention;
FIG. 3 is a TEM image of the lithium cobaltate positive electrode material coated with the zirconium phosphate lithium fast ion conductor and the uncoated lithium cobaltate positive electrode material obtained in example 2 of the present invention;
FIG. 4 is a graph comparing the capacity cycles at 0.2C for a half-cell assembled from example 2 of the present invention and uncoated lithium cobaltate positive electrode material and lithium metal negative electrode, respectively;
FIG. 5 is a charge-discharge curve at 0.2C for a half-cell assembled by an uncoated lithium cobaltate positive electrode material and a lithium metal negative electrode;
fig. 6 is a charge-discharge curve of a half-cell assembled by a lithium cobaltate positive electrode material coated by a zirconium phosphate lithium fast ion conductor obtained in example 2 of the present invention and a lithium metal negative electrode at 0.2C;
FIG. 7 is a graph comparing the capacity cycles at 0.5C for half-cells assembled from example 2 of the present invention and uncoated lithium cobaltate positive electrode material and lithium metal negative electrode, respectively;
FIG. 8 is a graph comparing the rate performance of half cells assembled from the uncoated lithium cobaltate positive electrode material and the lithium metal negative electrode in example 2 of the present invention at different current densities (0.1C, 0.5C, 1C, 2C, 5C);
fig. 9 is an in-situ XRD pattern during the cycle of the positive electrode materials in example 2 of the present invention and comparative example 1; in the figure, a is the in-situ XRD heat map of comparative example 1 and the change of the (003) peak and the (004) peak during the first charge and discharge; b is the in situ XRD thermogram of example 2 and the variation of the (003) and (004) peaks during the first charge and discharge;
FIG. 10 is a GITT graph of the positive electrode materials of example 2 of the present invention and comparative example 1 and a diffusion coefficient calculated from the GITT; in the figure, a-d respectively represent the GITT diagrams of comparative example 1; GITT profile of example 2; comparative example 1 and example 2 are plots of lithium ion diffusion coefficient during charging; comparative example 1 and example 2 are graphs comparing lithium ion diffusion coefficients during discharge.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The experimental materials and reagents used in the following examples are commercially available unless otherwise specified.
The specific techniques or conditions not specified in the examples can be performed according to the techniques or conditions described in the literature in the field or according to the product specification.
Example 1
The preparation method of the zirconium phosphate lithium fast ion conductor coated modified lithium cobaltate positive electrode material specifically comprises the following steps:
(1) 0.06894g (0.001mol) of lithium nitrate (68.94 relative molecular mass) is weighed and transferred into a 250ml reagent bottle, 0.85864g (0.002mol) of zirconium nitrate pentahydrate (429.32 relative molecular mass) is weighed and transferred into the reagent bottle, 0.34509g (0.003mol) of ammonium dihydrogen phosphate (115.03 relative molecular mass) is weighed and transferred into the reagent bottle, 100ml of ethanol is added into the reagent bottle, and the mixture is slowly stirred until the solid is dissolved and a milky white suspension is formed. The molar ratio of lithium, zirconium and phosphorus is 1: 2: 3 (under the condition, 0.5ml of solution is required for 0.5 wt% coating, 1ml of solution is required for 1 wt% coating, and the rest coating is repeated, so that the solution is prepared for facilitating the subsequent operation).
(2) 0.5ml of the solution in the step (1) is sucked by a pipette gun, 50ml of ethanol is added, and the mixture is slowly and uniformly stirred.
(3) 0.47431g of lithium cobaltate is weighed and added into the solution (2), the solution is stirred for 6 hours at 80 ℃ until the solvent is volatilized to leave a solid agglomerate, the solid agglomerate is ground into powder and then is transferred into a muffle furnace, and the powder is heated to 800 ℃ at the heating rate of 1 ℃/min in the air atmosphere and is kept warm for 4 hours to obtain the lithium cobaltate cathode material coated by the zirconium lithium phosphate fast ion conductor.
Example 2
The preparation method of the zirconium phosphate lithium fast ion conductor coated modified lithium cobaltate positive electrode material specifically comprises the following steps:
(1) 0.06894g (0.001mol) of lithium nitrate (68.94 relative molecular mass) is weighed and transferred into a 250ml reagent bottle, 0.85864g (0.002mol) of zirconium nitrate pentahydrate (429.32 relative molecular mass) is weighed and transferred into the reagent bottle, 0.34509g (0.003mol) of ammonium dihydrogen phosphate (115.03 relative molecular mass) is weighed and transferred into the reagent bottle, 100ml of ethanol is added into the reagent bottle, and the mixture is slowly stirred until the solid is dissolved and a milky white suspension is formed. The molar ratio of lithium, zirconium and phosphorus is 1: 2: 3.
(2) sucking 1ml of the solution in the step (1) by using a pipette gun, adding 50ml of ethanol, and slowly and uniformly stirring.
(3) 0.47431g of lithium cobaltate is weighed and added into the solution (2), the solution is stirred for 6 hours at 80 ℃ until the solvent is volatilized to leave a solid agglomerate, the solid agglomerate is ground into powder and then is transferred into a muffle furnace, and the powder is heated to 800 ℃ at the heating rate of 1 ℃/min in the air atmosphere and is kept warm for 4 hours to obtain the lithium cobaltate cathode material coated by the zirconium lithium phosphate fast ion conductor.
Example 3
The preparation method of the zirconium phosphate lithium fast ion conductor coated modified lithium cobaltate positive electrode material specifically comprises the following steps:
(1) 0.06894g (0.001mol) of lithium nitrate (68.94 relative molecular mass) is weighed and transferred into a 250ml reagent bottle, 0.85864g (0.002mol) of zirconium nitrate pentahydrate (429.32 relative molecular mass) is weighed and transferred into the reagent bottle, 0.34509g (0.003mol) of ammonium dihydrogen phosphate (115.03 relative molecular mass) is weighed and transferred into the reagent bottle, 100ml of ethanol is added into the reagent bottle, and the mixture is slowly stirred until the solid is dissolved and a milky white suspension is formed. The molar ratio of lithium, zirconium and phosphorus is 1: 2: 3.
(2) sucking 2ml of the solution in the step (1) by using a pipette gun, adding 50ml of ethanol, and slowly and uniformly stirring.
(3) 0.47431g of lithium cobaltate is weighed and added into the solution (2), the solution is stirred for 6 hours at 80 ℃ until the solvent is volatilized to leave a solid agglomerate, the solid agglomerate is ground into powder and then is transferred into a muffle furnace, and the powder is heated to 800 ℃ at the heating rate of 1 ℃/min in the air atmosphere and is kept warm for 4 hours to obtain the lithium cobaltate cathode material coated by the zirconium lithium phosphate fast ion conductor.
Example 4
The preparation method of the zirconium phosphate lithium fast ion conductor coated modified lithium cobaltate positive electrode material specifically comprises the following steps:
(1) 0.06894g (0.001mol) of lithium nitrate (68.94 relative molecular mass) is weighed and transferred into a 250ml reagent bottle, 0.85864g (0.002mol) of zirconium nitrate pentahydrate (429.32 relative molecular mass) is weighed and transferred into the reagent bottle, 0.34509g (0.003mol) of ammonium dihydrogen phosphate (115.03 relative molecular mass) is weighed and transferred into the reagent bottle, 100ml of deionized water is added into the reagent bottle, and the mixture is slowly stirred until the solid is dissolved and a milky white suspension is formed. The molar ratio of lithium, zirconium and phosphorus is 1: 2: 3.
(2) and (3) sucking 1ml of the solution in the step (1) by using a pipette gun, adding 50ml of deionized water, and slowly and uniformly stirring.
(3) 0.47431g of lithium cobaltate is weighed and added into the solution (2), the solution is stirred for 6 hours at 80 ℃ until the solvent is volatilized to leave a solid agglomerate, the solid agglomerate is ground into powder and then is transferred into a muffle furnace, and the powder is heated to 800 ℃ at the heating rate of 1 ℃/min in the air atmosphere and is kept warm for 4 hours to obtain the lithium cobaltate cathode material coated by the zirconium lithium phosphate fast ion conductor.
Comparative example 1
Comparative example 1 differs from example 2 only in that: except for the uncoated lithium cobaltate, i.e. the lithium cobaltate in step (3). The treatments of steps (1), (2) and (3) were not conducted as comparative examples.
Fig. 1 is an XRD pattern of the cathode material prepared in example 2, fig. 2 is an SEM pattern of the cathode materials in example 2 and comparative example 1, and fig. 3 is a TEM pattern of the cathode materials in example 2 and comparative example 1 of the present invention, and it can be seen that lithium zirconium phosphate particles are coated on the surface of lithium cobaltate.
Assembling the battery: balance0.028g of the obtained lithium cobaltate positive electrode material is taken, 0.008g of Super C65 as a conductive agent and 0.004g of PVDF (polyvinylidene fluoride) as a binder are added, the mixture is uniformly mixed and coated on an aluminum foil to prepare a positive electrode plate, lithium metal is taken as a negative electrode, PP (polypropylene) is taken as a diaphragm, and 1mol/L LiPF (lithium ion plasma fluoride) is taken6The electrolyte is dissolved in EC: DMC: EMC (volume ratio is 1:1: 1) to form the CR2016 button cell.
As shown in fig. 4-8, the uncoated lithium cobaltate is assembled into a battery, the first discharge capacity is 221.51mAh/g in a voltage interval of 3.0-4.6V at 0.1C rate, and the capacity retention rate is 60% after 40 cycles; at 0.5C, the first discharge capacity is 220.57mAh/g, and after 100 cycles, the capacity retention rate is 37.8%. The first discharge capacity is respectively 212.3mAh/g, 173.2mAh/g, 130.6mAh/g, 85.1mAh/g and 9.1mAh/g under the multiplying power of 0.1C, 0.5C, 1C, 2C and 5C.
The battery is assembled by lithium cobaltate coated by the zirconium phosphate lithium fast ion conductor, the first discharge capacity can reach 217.5mAh/g within a voltage range of 3-4.6V and under 0.1C multiplying power, and after circulation is carried out for 40 circles, the capacity retention rate can reach 77.8%; under 0.5C, the first discharge capacity can reach 214.9mAh/g, and after 100 cycles, the capacity retention rate can reach 75.1%; under the multiplying power of 0.1C, 0.5C, 1C, 2C and 5C respectively, the first discharge capacity can reach 212.3mAh/g, 195.1mAh/g, 170.7mAh/g, 141.5mAh/g and 80.7mAh/g respectively.
Fig. 9 is an in-situ XRD pattern during the cycle of the cathode materials of example 2 and comparative example 1, and it can be concluded that the structure of the coated sample is more stable and the volume change is smaller during the cycle because the change of the (003) peak represents the change of the c-axis in the crystal.
Fig. 10 is a GITT graph of the positive electrode materials of example 2 and comparative example 1, and the results show that example 2 has a lithium ion diffusion coefficient about twice that of comparative example 1, so example 2 has excellent rate performance.
In conclusion, the method successfully coats the zirconium phosphate lithium fast ion conductor on the surface of the lithium cobaltate positive electrode to form particles, wherein the particle size of the positive electrode material is 6-8 mu m, and the shape of the positive electrode material is similar to a sphere. Compared with uncoated lithium cobaltate, the zirconium phosphate lithium fast ion conductor coating improves the cycle performance of the lithium cobaltate under the high voltage of 4.6V, and the coated lithium cobaltate cathode material has the advantages of good cycle stability, good rate capability, stable structure and the like. The method has low cost and simple preparation process, and is suitable for large-scale production.
The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. A lithium cobaltate positive electrode material coated and modified by a zirconium phosphate lithium fast ion conductor is characterized in that: the zirconium phosphate lithium fast ion conductor is coated on the surface of a lithium cobaltate positive electrode material to form particles, the mass of the zirconium phosphate lithium fast ion conductor is 0.5-5 wt%, the particle size range of the positive electrode material is 6-8 mu m, and the shape of the positive electrode material is similar to a sphere.
2. The preparation method of the lithium cobaltate positive electrode material coated and modified by the zirconium phosphate lithium fast ion conductor according to claim 1, characterized in that: the method comprises the following steps:
(1) dissolving a lithium source compound, a zirconium source compound and a phosphorus source compound in an organic solvent or water according to a molar ratio, and slowly stirring until the solid is completely dissolved to form a milky suspension; adding lithium cobaltate powder, stirring and heating until the solvent is volatilized to leave a solid agglomerate;
(2) grinding the solid agglomerate obtained in the step (1) to obtain black and uniform powder;
(3) and (3) sintering the powder obtained in the step (2) at a high temperature to obtain the lithium cobaltate positive electrode material coated by the zirconium phosphate lithium fast ion conductor.
3. The preparation method of the lithium cobaltate positive electrode material coated and modified by the zirconium phosphate lithium fast ion conductor according to claim 2, characterized in that: the lithium source compound is selected from one or more of lithium sulfate, lithium carbonate, lithium nitrate and lithium hydroxide; the zirconium source compound is selected from one or more of zirconium chloride, zirconium nitrate and zirconium sulfate; the phosphorus source compound is selected from one or more of diammonium hydrogen phosphate, ammonium dihydrogen phosphate and lithium phosphate.
4. The preparation method of the lithium cobaltate positive electrode material coated and modified by the zirconium phosphate lithium fast ion conductor according to claim 2, characterized in that: the organic solvent is one or more of methanol, ethanol, glycol and isopropanol.
5. The preparation method of the lithium cobaltate positive electrode material coated and modified by the zirconium phosphate lithium fast ion conductor according to claim 2, characterized in that: the mass ratio of the zirconium lithium phosphate fast ion conductor to the lithium cobaltate powder is 0.1-5: 100.
6. The preparation method of the lithium cobaltate positive electrode material coated and modified by the zirconium phosphate lithium fast ion conductor according to claim 2, characterized in that: the stirring and heating temperature is 50-100 ℃, and the stirring time is 2-8 h.
7. The preparation method of the lithium cobaltate positive electrode material coated and modified by the zirconium phosphate lithium fast ion conductor according to claim 6, wherein the preparation method comprises the following steps: the temperature rise rate of the sintering is 1-5 ℃/min, the temperature is raised to 600-1000 ℃, the temperature is kept for 2-8 hours, and the sintering atmosphere is air.
8. The preparation method of the lithium cobaltate positive electrode material coated and modified by the zirconium phosphate lithium fast ion conductor according to claim 7, wherein the preparation method comprises the following steps: heating to 800-1000 ℃.
9. The application of the lithium cobaltate positive electrode material coated and modified by the lithium zirconium phosphate fast ion conductor according to claim 1 in a lithium ion battery.
10. The application of the lithium cobaltate positive electrode material coated and modified by the zirconium phosphate lithium fast ion conductor in the lithium ion battery according to claim 9 is characterized in that: mixing the positive electrode material, conductive agent and polyvinylidene fluoride, coating the mixture on an aluminum foil to prepare a positive plate, taking lithium metal as a negative electrode and polypropylene as a diaphragm, and mixing LiPF6And dissolving the mixture in a mixed solution of EC, DMC and EMC in a volume ratio of 1:1:1 to form an electrolyte, and assembling the battery.
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