Preparation method of metal mixed oxide coated lithium cobalt oxide positive electrode material

Abstract

The invention belongs to the field of lithium ion battery positive electrode materials, and particularly relates to a preparation method of a metal mixed oxide coated lithium cobalt oxide positive electrode material. The method comprises the following steps: firstly, taking a certain amount of cobalt source, lithium source and fused salt according to a preset salt material mass ratio, uniformly mixing the three sources, pouring the mixture into an alumina crucible, and then putting the alumina crucible into a muffle furnace for sintering; and after the reaction is finished, washing with deionized water to remove residual salt and impurities, and carrying out suction filtration and drying to obtain lithium cobalt oxide powder with a certain particle size. And then adding a certain amount of aluminum source, magnesium source, titanium source and zinc source into the powder, and roasting in a muffle furnace to form an oxide layer coated with lithium cobalt oxide, thereby finally obtaining the powder of the lithium cobalt oxide coated with the metal mixed oxide. The lithium cobalt oxide positive electrode material obtained by the preparation method has the advantages of controllable particle size, adjustable oxide layer thickness, variable material composition and the like, and the structural stability, the specific capacity, the cut-off voltage and the cycle life of the positive electrode of the lithium ion battery under high voltage can be remarkably improved.

Description

Technical Field

[0001] The invention belongs to the field of lithium-ion battery materials, and in particular relates to a method for preparing a metal mixed oxide-coated lithium cobalt oxide positive electrode material. Background Art

[0002] Lithium cobalt oxide batteries are mainly used in consumer electronic products. In recent years, with the vigorous development of 5G technology, people's demand for small electronic devices such as mobile phones, notebooks, MP3 / 4, etc. has continued to increase. The capacity of lithium cobalt oxide positive electrode materials that can actually participate in stable cycles is often less than 160 mAh / g. In addition, under high voltage operation, lithium cobalt oxide positive electrode materials have irreversible phase changes, cobalt ion dissolution, material surface structure degradation, and uneven lithium ion embedding and extraction, which makes their cycle stability poor. Lithium cobalt oxide positive electrode materials are often prepared by solid phase reaction method. The extremely high synthesis temperature makes the positive electrode material particle size uneven, excessive growth occurs, it is difficult to form a stable positive electrode / electrolyte interface, and the battery cycle performance decreases. To this end, solving the above problems of lithium cobalt oxide positive electrode materials can greatly drive the update and iteration of consumer electronic products and improve people's quality of life. Summary of the invention

[0003] The purpose of the present invention is to solve the problems mentioned above, and to this end, a method for preparing a metal mixed oxide coated lithium cobalt oxide positive electrode material is provided, which specifically adopts the following technical scheme: The cobalt source, lithium source and molten salt are uniformly mixed in a certain proportion, poured into an alumina crucible, and placed in a muffle furnace for sintering at a certain temperature; The product obtained after sintering in step (1) is washed with deionized water to remove residual salt and impurities, and then filtered and dried to obtain lithium cobalt oxide powder with a certain particle size; The lithium cobalt oxide powder obtained in step (2) is uniformly mixed with an aluminum source, a magnesium source, a titanium source and a zinc source in a certain proportion, poured into an alumina crucible, and placed in a muffle furnace for sintering at a certain temperature to obtain a lithium cobalt oxide positive electrode material coated with a metal mixed oxide (Al-Ti-Zn-Mg).

[0004] In the step (1), the cobalt source includes at least one of cobalt oxide, cobalt hydroxide, cobalt nitrate, cobalt sulfate, cobalt oxalate, cobalt halide, and cobalt phosphate; in the step (1), the lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium chloride, lithium molybdate, lithium oxalate, and lithium fluoride; In the step (1), the molten salt includes at least one of alkali metal, alkaline earth metal halide, sulfate, nitrate, carbonate and nitrite.

[0005] In the step (1), the sintering temperature of the muffle furnace is 100-2000°C, the heating rate is 1-50°C / min, and the holding time is 0-30h.

[0006] In the step (1), the mass ratio of the cobalt source, the lithium source and the molten salt is (1-10): (1-10): (5-50).

[0007] In the step (2), the particle size of the lithium cobalt oxide powder is 50nm~500nm.

[0008] In the step (3), the aluminum source includes at least one of aluminum oxides, aluminum chlorides and hydroxides, aluminum salts, and aluminum metal; The magnesium source includes at least one of magnesium-containing oxides, chlorides and hydroxides, magnesium-containing salts, and magnesium metal; The titanium source includes at least one of titanium-containing oxides, chlorides and hydroxides, titanium-containing salts, and titanium metal; The zinc source includes at least one of zinc-containing oxides, chlorides and hydroxides, zinc-containing salts, and zinc metal element.

[0009] In the step (3), the mass ratio of lithium cobalt oxide, aluminum source, magnesium source, titanium source and zinc source is (5-20): (1-10): (1-5): (1-12): (2-10).

[0010] In the step (3), the sintering temperature of the muffle furnace is 150-1700°C, the heating rate is 1-50°C / min, and the holding time is 1-30h.

[0011] In the step (3), the thickness of the obtained metal mixed oxide coating layer is 90nm~450nm.

[0012] The technical solution of the present invention has the following advantages: The molten salt method is used to prepare lithium cobalt oxide powder, which significantly reduces the synthesis temperature and preparation cycle of the material, while inhibiting the excessive growth of grains.

[0013] By controlling the heating rate and holding time during the sintering process in step (1), lithium cobalt oxide powder with controllable particle size can be obtained.

[0014] By controlling the heating rate, holding time, and mass ratio of the aluminum source, magnesium source, titanium source, and zinc source during the sintering process in step (3), the thickness and composition of the metal mixed oxide layer can be controlled.

[0015] The present invention provides a method for preparing a metal mixed oxide-coated lithium cobalt oxide positive electrode material, which has simple steps. A molten salt method is used to uniformly mix a titanium source, a magnesium source, an aluminum source, and a zinc source at a high temperature, and a tightly integrated Al-Ti-Zn-Mg mixed metal oxide coating layer can be formed on the surface of the lithium cobalt oxide powder. The presence of the coating layer can significantly inhibit the degradation of the surface of the lithium cobalt oxide material and reduce the structural instability, while improving the transmission efficiency of lithium ions, thereby significantly improving the structural stability of the electrode, the specific capacity of the battery, the cut-off voltage and the cycle life. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The present invention is a schematic diagram of the preparation process of a metal mixed oxide-coated lithium cobalt oxide positive electrode material. DETAILED DESCRIPTION

[0017] Figure 1 The following is a schematic diagram of the preparation process of a metal mixed oxide coated lithium cobalt oxide positive electrode material of the present invention. The following examples are provided for a better understanding of the present invention, but are not limited to the best implementation mode, and do not limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0018] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially. Example 1

[0019] This embodiment provides a method for preparing a metal mixed oxide coated lithium cobalt oxide positive electrode material, which specifically includes the following steps: (1) Cobalt hydroxide, lithium chloride and sodium chloride were uniformly mixed in a mass ratio of 2:1:5, poured into an alumina crucible, and sintered in a muffle furnace at 800°C with a heating rate of 5°C / min and a holding time of 5 h; (2) washing the product obtained after sintering in step (1) with deionized water to remove residual salt and impurities, filtering and drying at 70° C. to obtain lithium cobalt oxide powder with a particle size of 100 to 350 nm; (3) The lithium cobalt oxide powder obtained in step (2) is uniformly mixed with aluminum oxide, magnesium oxide, elemental titanium and zinc chloride in a mass ratio of 5:3:2:2.5:4, poured into an alumina crucible, and sintered in a muffle furnace at 1200° C. with a heating rate of 5° C. / min and a holding time of 10 h to obtain a lithium cobalt oxide positive electrode material coated with a metal mixed oxide, wherein the thickness of the metal mixed oxide coating layer is 200-300 nm. Example 2

[0020] This embodiment provides a method for preparing a metal mixed oxide coated lithium cobalt oxide positive electrode material, which specifically includes the following steps: (1) Cobalt hydroxide, lithium hydroxide and sodium chloride were uniformly mixed in a mass ratio of 3:4:25, poured into an alumina crucible, and sintered in a muffle furnace at 800°C with a heating rate of 5°C / min and a holding time of 8 h; (2) washing the product obtained after sintering in step (1) with deionized water to remove residual salt and impurities, filtering and drying at 70° C. to obtain lithium cobalt oxide powder with a particle size of 150 to 200 nm; (3) The lithium cobalt oxide powder obtained in step (2) is uniformly mixed with aluminum chloride, magnesium oxide, titanium dioxide and zinc sulfate in a mass ratio of 10:3:2:5:9, poured into an alumina crucible, and sintered in a muffle furnace at 1200° C. with a heating rate of 5° C. / min and a holding time of 12 h to obtain a metal mixed oxide-coated lithium cobalt oxide positive electrode material, wherein the thickness of the metal mixed oxide coating layer is 300-450 nm. Example 3

[0021] This embodiment provides a method for preparing a metal mixed oxide coated lithium cobalt oxide positive electrode material, which specifically includes the following steps: (1) Cobalt trioxide, lithium hydroxide and sodium chloride were uniformly mixed in a mass ratio of 1.5:1:5, poured into an alumina crucible, and sintered in a muffle furnace at 600°C with a heating rate of 5°C / min and a holding time of 5 h; (2) washing the product obtained after sintering in step (1) with deionized water to remove residual salt and impurities, filtering and drying at 70° C. to obtain lithium cobalt oxide powder with a particle size of 350 to 450 nm; (3) The lithium cobalt oxide powder obtained in step (2) is uniformly mixed with aluminum chloride, magnesium oxide, titanium dioxide and elemental zinc in a mass ratio of 5:3:2:2.5:4, poured into an alumina crucible, and sintered in a muffle furnace at 1200° C. with a heating rate of 5° C. / min and a holding time of 10 h to obtain a lithium cobalt oxide positive electrode material coated with a metal mixed oxide, wherein the thickness of the metal mixed oxide coating layer is 200-350 nm. Example 4

[0022] This embodiment provides a method for preparing a metal mixed oxide coated lithium cobalt oxide positive electrode material, which specifically includes the following steps: (1) Cobalt nitrate, lithium chloride and potassium chloride were uniformly mixed in a mass ratio of 3:3:10, poured into an alumina crucible, and sintered in a muffle furnace at 800°C with a heating rate of 5°C / min and a holding time of 12 h; (2) washing the product obtained after sintering in step (1) with deionized water to remove residual salt and impurities, filtering and drying at 70° C. to obtain lithium cobalt oxide powder with a particle size of 350 to 500 nm; (3) The lithium cobalt oxide powder obtained in step (2) is uniformly mixed with elemental aluminum, magnesium chloride, elemental titanium and zinc nitrate in a mass ratio of 5:3:2:2.5:4, poured into an alumina crucible, and sintered in a muffle furnace at 1200° C. with a heating rate of 10° C. / min and a holding time of 2 h to obtain a lithium cobalt oxide positive electrode material coated with a metal mixed oxide, wherein the thickness of the metal mixed oxide coating layer is 100 to 180 nm. Example 5

[0023] This embodiment provides a method for preparing a metal mixed oxide coated lithium cobalt oxide positive electrode material, which specifically includes the following steps: (1) Cobalt hydroxide, lithium carbonate and potassium chloride were uniformly mixed in a mass ratio of 3:5:10, poured into an alumina crucible, and sintered in a muffle furnace at 800°C with a heating rate of 5°C / min and a holding time of 12 h; (2) washing the product obtained after sintering in step (1) with deionized water to remove residual salt and impurities, filtering and drying at 70° C. to obtain lithium cobalt oxide powder with a particle size of 150 to 300 nm; (3) The lithium cobalt oxide powder obtained in step (2) is uniformly mixed with aluminum oxide, magnesium chloride, titanium dioxide and zinc oxide in a mass ratio of 15:3:1:6:10, poured into an alumina crucible, and placed in a muffle furnace for sintering at 1500° C. at a heating rate of 10° C. / min and a holding time of 20 h to obtain a lithium cobalt oxide positive electrode material coated with a metal mixed oxide, wherein the thickness of the metal mixed oxide coating layer is 400-650 nm. Comparative Example 1

[0024] This comparative example provides a method for preparing a metal mixed oxide coated lithium cobalt oxide positive electrode material, which differs from Example 1 only in that in step (3), the lithium cobalt oxide powder obtained in step (2) is uniformly mixed with magnesium oxide in a mass ratio of 2:1, poured into an alumina crucible, and placed in a muffle furnace for sintering at 1200° C., with a heating rate of 5° C. / min and a holding time of 10 h, to obtain a single metal oxide coated lithium cobalt oxide positive electrode material. Comparative Example 2

[0025] This comparative example provides a method for preparing a metal mixed oxide-coated lithium cobalt oxide positive electrode material, which differs from Example 1 only in that in step (1), no molten salt is added, cobalt hydroxide and lithium chloride are uniformly mixed in a mass ratio of 1.5:1, poured into an alumina crucible, and placed in a muffle furnace for sintering at 800°C, with a heating rate of 5°C / min and a holding time of 5h.

[0026] Performance Testing The lithium cobalt oxide positive electrode materials prepared in Examples 1 to 5 and Comparative Examples 1 to 2 were mixed with conductive carbon black and PVDF (polytetrafluoroethylene) in a mass ratio of 7:1:1, and N-methylpyrrolidone was added as a dispersant to prepare a positive electrode slurry. The positive electrode slurry was evenly coated on an aluminum foil and placed in an oven at 80°C for 2 hours. A positive electrode sheet was obtained. A CR2032 button battery was assembled in the order of a negative electrode sheet, an electrolyte, a separator, an electrolyte, and a positive electrode sheet.

[0027] The assembled battery was tested for electrical performance using a blue power test system at room temperature. The test voltage range was 3.0-4.5V, and the battery was charged and discharged at a rate of 0.1C to obtain a discharge capacity of 0.1C. The battery was then charged and discharged at a rate of 1C to obtain a discharge capacity of 1C. The battery was then charged and discharged continuously at a rate of 1C for a total of 100 cycles. The battery was tested for cycle capacity retention after 100 cycles. The test results are shown in Table 1.

[0028] Table 1 It can be seen from Table 1 that the metal mixed oxide coated lithium cobalt oxide positive electrode material prepared by a specific method of the present invention has better discharge specific capacity and cycle capacity retention rate under high voltage (3.0-4.5V) conditions than the data of the comparative example of the present invention. It can be seen that the metal mixed oxide coated lithium cobalt oxide positive electrode material prepared by the present invention can significantly improve the electrochemical performance of the positive electrode material of lithium ion batteries under high voltage.

[0029] The above-mentioned embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention shall fall within the scope of protection required by the present invention.

Claims

1. A method for preparing a metal mixed oxide coated lithium cobalt oxide positive electrode material, characterized in that: The following steps are involved: The cobalt source, lithium source and molten salt are uniformly mixed in a certain proportion, poured into an alumina crucible, and placed in a muffle furnace for sintering at a certain temperature; The product obtained after sintering in step (1) is washed with deionized water to remove residual salt and impurities, and then filtered and dried to obtain lithium cobalt oxide powder with a certain particle size; The lithium cobalt oxide powder obtained in step (2) is uniformly mixed with an aluminum source, a magnesium source, a titanium source and a zinc source in a certain proportion, poured into an alumina crucible, and placed in a muffle furnace for sintering at a certain temperature to obtain a lithium cobalt oxide positive electrode material coated with a metal mixed oxide (Al-Ti-Zn-Mg).

2. The method for preparing a metal mixed oxide coated lithium cobalt oxide positive electrode material according to claim 1, characterized in that: In the step (1), the cobalt source includes at least one of cobalt oxide, cobalt hydroxide, cobalt nitrate, cobalt sulfate, cobalt oxalate, cobalt halide, and cobalt phosphate; In the step (1), the lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium chloride, lithium molybdate, lithium oxalate, and lithium fluoride; In the step (1), the molten salt includes at least one of alkali metal, alkaline earth metal halide, sulfate, nitrate, carbonate and nitrite.

3. The method for preparing a metal mixed oxide coated lithium cobalt oxide positive electrode material according to claim 1, characterized in that: In the step (1), the sintering temperature of the muffle furnace is 100-2000°C, the heating rate is 1-50°C / min, and the holding time is 0-30h.

4. The method for preparing a metal mixed oxide coated lithium cobalt oxide positive electrode material according to claim 1, characterized in that: In the step (1), the mass ratio of the cobalt source, the lithium source and the molten salt is (1-10): (1-10): (5-50).

5. The method for preparing a metal mixed oxide coated lithium cobalt oxide positive electrode material according to claim 1, characterized in that: In the step (2), the particle size of the lithium cobalt oxide powder is 50nm~500nm.

6. The method for preparing a metal mixed oxide coated lithium cobalt oxide positive electrode material according to claim 1, characterized in that: In the step (3), the aluminum source includes at least one of aluminum oxides, chlorides and hydroxides, aluminum salts, and aluminum metal; The magnesium source includes at least one of magnesium-containing oxides, chlorides and hydroxides, magnesium-containing salts, and magnesium metal; The titanium source includes at least one of titanium-containing oxides, chlorides and hydroxides, titanium-containing salts, and titanium metal; The zinc source includes at least one of zinc-containing oxides, chlorides and hydroxides, zinc-containing salts, and zinc metal element.

7. The method for preparing a metal mixed oxide coated lithium cobalt oxide positive electrode material according to claim 1, characterized in that: In the step (3), the mass ratio of lithium cobalt oxide, aluminum source, magnesium source, titanium source and zinc source is (5-20): (1-10): (1-5): (1-12): (2-10).

8. The method for preparing a metal mixed oxide coated lithium cobalt oxide positive electrode material according to claim 1, characterized in that: In the step (3), the sintering temperature of the muffle furnace is 150-1700°C, the heating rate is 1-50°C / min, and the holding time is 1-30h.

9. The method for preparing a metal mixed oxide coated lithium cobalt oxide positive electrode material according to claim 1, characterized in that: In the step (3), the thickness of the obtained metal mixed oxide coating layer is 90nm~450nm.

10. The present invention provides a method for preparing a metal mixed oxide-coated lithium cobalt oxide positive electrode material, characterized in that: Prepared by the preparation method described in any one of claims 1 to 9.

Images