A lithium cobalt oxide cathode material coated with high-entropy oxide and its preparation method

Abstract

The present invention provides a lithium cobalt oxide cathode material coated with high-entropy oxide and a preparation method thereof. The lithium cobalt oxide cathode material coated with high-entropy oxide of the present invention includes lithium cobalt oxide inside the material and a coating layer coated on the surface of the lithium cobalt oxide. The chemical formula of the lithium cobalt oxide located at the core is LiCo a Tm 1‑a O2, where 0.99 ≤ a ≤ 0.999, and Tm is at least one of Mg, Al, Ti, Sr, Zr, Mo, and Nb; the coating layer is a high-entropy oxide coating layer, and the chemical formula of the high-entropy oxide is MO x , where M includes at least 6 of Fe, Co, Ni, Mn, Al, Cr, Zn, and Si, 1

Description

Technical Field

[0001] The present invention relates to the field of battery materials, and particularly to a lithium cobalt oxide cathode material coated with high-entropy oxide and a preparation method thereof. Background Art

[0002] In recent years, some new consumer electronics have developed rapidly, such as electronic cigarettes, drones, and model aircraft. These application scenarios have put forward higher requirements for the rate performance of lithium cobalt oxide cathode materials.

[0003] Although in the prior art, the performance of the material is improved by coating lithium cobalt oxide with an oxide. For example, the invention patent 202310542447.0, "Porous Alumina-Doped Titanium Dioxide Nanotube Coated Lithium Cobalt Oxide Composite Material and Its Preparation Method, Lithium Ion Battery", discloses a porous alumina-doped titanium dioxide nanotube coated lithium cobalt oxide composite material and its preparation method. The preparation method of the porous alumina-doped titanium dioxide nanotube coated lithium cobalt oxide composite material includes the following steps: preparing TiO2 nanotubes doped with Al-MOF precursor by a solvothermal method, and then calcining it to obtain porous Al2O3-doped TiO2 nanotubes; mixing the porous Al2O3-doped TiO2 nanotubes and the lithium cobalt oxide material evenly, and obtaining a porous Al2O3-doped TiO2 nanotube coated lithium cobalt oxide composite material after high-temperature treatment. This composite material has excellent electrochemical performance, making the LiCoO2 battery with it as the positive active material have excellent discharge specific capacity, mass energy density, and cycle stability. However, the improvement of the performance of the lithium cobalt oxide cathode material is not obvious. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a lithium cobalt oxide cathode material coated with high-entropy oxide and a preparation method thereof.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is: a lithium cobalt oxide cathode material coated with high-entropy oxide, the lithium cobalt oxide cathode material coated with high-entropy oxide includes lithium cobalt oxide located inside the material and a coating layer coated on the surface of the lithium cobalt oxide. The chemical formula of the lithium cobalt oxide located at the core is LiCo a Tm 1-a O2, where 0.99 ≤ a ≤ 0.999, and Tm is at least one of Mg, Al, Ti, Sr, Zr, Mo, and Nb; the coating layer is a high-entropy oxide coating layer, and the chemical formula of the high-entropy oxide is MO x , where M includes at least 6 of Fe, Co, Ni, Mn, Al, Cr, Zn, and Si, 1 < x < 2 and satisfies that the total valence is zero.

[0006] The above-mentioned lithium cobalt oxide cathode material coated with high-entropy oxide is obtained by sintering and coating the lithium cobalt oxide material with high-entropy oxide, forming a lithium cobalt oxide cathode material with the lithium cobalt oxide material as the core and the high-entropy oxide as the coating layer. The chemical formula of the high-entropy oxide is MO x , where M includes at least 6 of Fe, Co, Ni, Mn, Al, Cr, Zn, and Si, which can not only improve the discharge capacity and cycling performance of the lithium cobalt oxide cathode material, but also significantly improve the rate performance of lithium cobalt oxide.

[0007] Preferably, the chemical formula of the high-entropy oxide is MO x , where M includes at least 6 of Fe, Co, Ni, Mn, Al, Cr, and Si.

[0008] Preferably, the chemical formula of the high-entropy oxide is MO x , where M includes at least 6 of Fe, Co, Ni, Mn, Al, Cr, Zn, and Si and necessarily includes Si.

[0009] The inventors found through research that for the lithium cobalt oxide cathode material formed with the high-entropy oxide as the coating layer, when Si is contained in the coating layer, the high-entropy oxide combined with other components can better improve the discharge capacity, cycling performance, and rate performance of the lithium cobalt oxide cathode material.

[0010] Preferably, the chemical formula of the high-entropy oxide is MO x , where M includes at least 6 of Fe, Co, Ni, Mn, Al, Cr, Zn, and Si and necessarily includes Si, Fe, Co, and Ni.

[0011] The inventors found through research that the above element combination of the high-entropy oxide can better improve the discharge capacity, cycling performance, and rate performance of the lithium cobalt oxide cathode material.

[0012] Preferably, the chemical formula of the high-entropy oxide is MO x , where M includes at least 6 of Fe, Co, Ni, Mn, Al, Cr, Zn, and Si and necessarily includes Fe, Co, Ni, Mn, Al, and Si.

[0013] The inventors found through research that the above element combination of the high-entropy oxide can better improve the discharge capacity, cycling performance, and rate performance of the lithium cobalt oxide cathode material.

[0014] Preferably, the thickness of the coating layer is 1 nm to 500 nm.

[0015] Preferably, the thickness of the coating layer is 5 nm to 100 nm.

[0016] Preferably, the content of the coating layer in the lithium cobalt oxide cathode material coated with high-entropy oxide is 0.1% to 1%.

[0017] The present invention also provides a method for preparing the lithium cobaltate cathode material coated with high-entropy oxide as described in any one of the above, and the method comprises the following steps:

[0018] (1) Weigh and mix a lithium source, a cobalt source, and a Tm source in a required stoichiometric ratio and then perform a first heat treatment to obtain a lithium cobaltate matrix material LiCo a Tm 1-a O2; the heat preservation temperature of the first heat treatment is 940°C to 1000°C, the heat preservation time is 8 to 16 hours, the heating rate is 3 to 5°C / min, and the sintering atmosphere is air;

[0019] (2) Mix the lithium cobaltate matrix material and the source material of MO x uniformly by mass and then perform a second heat treatment to obtain the lithium cobaltate cathode material coated with high-entropy oxide; the heat preservation temperature of the second heat treatment is 750°C to 850°C, the heat preservation time is 6 to 12 hours, the heating rate is 3 to 5°C / min, and the sintering atmosphere is air.

[0020] Preferably, the lithium source is one or two of lithium carbonate and lithium hydroxide; the cobalt source is one or two of its oxides and carbonates, and the particle size of the cobalt source satisfies 3.5μm ≤ D50 ≤ 5.5μm; the Tm source is one or more of its oxides, hydroxides, and carbonates.

[0021] Preferably, the M source is a nano-oxide of the corresponding element and the particle size satisfies D50 ≤ 2.0μm.

[0022] The present invention also provides a lithium ion secondary battery, and the lithium ion secondary battery comprises the lithium cobaltate cathode material coated with high-entropy oxide as described in any one of the above.

[0023] The beneficial effects of the present invention are as follows: The present invention provides a lithium cobaltate cathode material coated with high-entropy oxide and a method for preparing the same. The lithium cobaltate cathode material coated with high-entropy oxide of the present invention performs sintering coating on the lithium cobaltate material through high-entropy oxide to form a lithium cobaltate cathode material with the lithium cobaltate material as the core and the high-entropy oxide as the coating layer. The chemical formula of the high-entropy oxide is MO x, where M contains at least 6 of Fe, Co, Ni, Mn, Al, Cr, Zn, and Si, which can not only improve the discharge capacity and cycling performance of the lithium cobalt oxide cathode material, but also significantly improve the rate performance of the lithium cobalt oxide. The advantages of the high-entropy oxide-coated lithium cobalt oxide cathode material of the present invention are as follows: 1. The nanoscale high-entropy oxide coating layer can construct a fast lithium-ion channel on the surface of the lithium cobalt oxide matrix, thus greatly improving the rate performance of the material. 2. The nanoscale high-entropy oxide coating layer can form a dense layer on the surface of the lithium cobalt oxide matrix, isolating the direct contact between the electrolyte and the matrix material, thereby reducing side reactions. And the selection of the types of high-entropy oxide materials improves the first Coulomb efficiency and reduces the consumption of active lithium, thus ensuring excellent capacity performance and cycling performance. Description of the Drawings

[0024] Figure 1 It is a TEM image of the high-entropy oxide-coated lithium cobalt oxide cathode material of the embodiment of the present invention.

[0025] Figure 2 It is a HRTEM image of the high-entropy oxide-coated lithium cobalt oxide cathode material of the embodiment of the present invention.

[0026] Figure 3 It is a cycling retention rate graph of some embodiments and comparative examples of the present invention. Detailed Embodiments

[0027] To better illustrate the purpose, technical solution and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0028] Example 1

[0029] As a high-entropy oxide-coated lithium cobalt oxide cathode material of an embodiment of the present invention, the high-entropy oxide-coated lithium cobalt oxide cathode material includes lithium cobalt oxide located inside the material and a coating layer coated on the surface of the lithium cobalt oxide. The chemical formula of the lithium cobalt oxide located at the core is LiCo 0.9935 Mg 0.003 Ti 0.003 Sr 0.0002 Mo 0.0003 O2. The coating layer is a high-entropy oxide coating layer, and the chemical formula of the high-entropy oxide is MO x , where M contains Fe, Co, Ni, Mn, Al, Cr, Zn, and Si.

[0030] As a preparation method of the high-entropy oxide-coated lithium cobalt oxide cathode material of an embodiment of the present invention, it includes the following steps:

[0031] (1) Weigh lithium carbonate, cobalt tetroxide, magnesium hydroxide, titanium dioxide, molybdenum dioxide, and strontium carbonate according to the stoichiometric ratio to prepare LiCo 0.9935 Mg 0.003 Ti0.003 Sr 0.0002 Mo 0.0003 O2. After mixing all the raw materials evenly, keep them at 955 °C for 12 h, with a heating rate of 4 °C / min, and the sintering atmosphere is air;

[0032] (2) Weigh the lithium cobalt oxide material obtained in step (1) and nano-iron oxide, nano-cobalt ferrite, nano-nickel oxide, nano-manganese ferrite, nano-aluminum oxide, nano-chromium oxide, and nano-silicon dioxide in proportion to prepare lithium cobalt oxide material @ 0.1% (Fe 0.1 Co 0.2 Ni 0.2 Mn 0.2 Al 0.2 Cr 0.1 O x ) 0.5 ·(SiO2) 0.5 , where 1 < x < 2 and the total valence is zero;

[0033] After mixing all the raw materials evenly, keep them at 820 °C for 9 h. The heating rate is 3 °C / min, and the sintering atmosphere is air. 0.1% means (Fe 0.1 Co 0.2 Ni 0.2 Mn 0.2 Al 0.2 Cr 0.1 O x ) 0.5 ·(SiO2) 0.5 , that is, the mass content of the high-entropy oxide in the high-entropy oxide-coated lithium cobalt oxide cathode material.

[0034] Example 2

[0035] As a high-entropy oxide-coated lithium cobalt oxide cathode material according to an embodiment of the present invention, the only difference between this embodiment and Example 1 is that the mass content of the high-entropy oxide in the high-entropy oxide-coated lithium cobalt oxide cathode material is 0.5%.

[0036] Example 3

[0037] As a high-entropy oxide-coated lithium cobalt oxide cathode material according to an embodiment of the present invention, the only difference between this embodiment and Example 1 is that: the mass content of the high-entropy oxide in the high-entropy oxide-coated lithium cobalt oxide cathode material is 1%.

[0038] Example 4

[0039] As a high-entropy oxide-coated lithium cobalt oxide cathode material according to an embodiment of the present invention, the only difference between this embodiment and Example 1 is that: the mass content of the high-entropy oxide in the high-entropy oxide-coated lithium cobalt oxide cathode material is 0.5%, and the high-entropy oxide is (Fe 0.1 Co0.2 Ni 0.2 Mn 0.2 Al 0.2 Zn 0.1 O x ) 0.5 ·(SiO2) 0.5 , where 1 < x < 2 and the total valence is zero.

[0040] Example 5

[0041] As a lithium cobalt oxide cathode material coated with high-entropy oxide according to an embodiment of the present invention, the only difference between this embodiment and Example 4 is: (Fe 0.1 Co 0.2 Ni 0.2 Mn 0.1 Al 0.3 Zn 0.1 O x ) 0.5 ·(SiO2) 0.5 , where 1 < x < 2 and the total valence is zero.

[0042] Example 6

[0043] As a lithium cobalt oxide cathode material coated with high-entropy oxide according to an embodiment of the present invention, the only difference between this embodiment and Example 4 is: the high-entropy oxide is (Fe 0.1 Co 0.3 Ni 0.1 Mn 0.1 Al 0.3 Zn 0.1 O x ) 0.5 ·(SiO2) 0.5 , where 1 < x < 2 and the total valence is zero.

[0044] Example 7

[0045] As a lithium cobalt oxide cathode material coated with high-entropy oxide according to an embodiment of the present invention, the only difference between this embodiment and Example 4 is: the high-entropy oxide is (Fe 0.2 Co 0.2 Ni 0.2 Mn 0.2 Al 0.2 O x ) 0.5 ·(SiO2) 0.5 , where 1 < x < 2 and the total valence is zero.

[0046] Example 8

[0047] As a lithium cobalt oxide cathode material coated with high-entropy oxide according to an embodiment of the present invention, the only difference between this embodiment and Embodiment 4 is that the high-entropy oxide is (Co 0.2 Ni 0.2 Mn 0.2 Al 0.2 Zn 0.2 O x ) 0.5 ·(SiO2) 0.5 , where 1 < x < 2 and the total valence is zero.

[0048] Example 9

[0049] As a lithium cobalt oxide cathode material coated with high-entropy oxide according to an embodiment of the present invention, the only difference between this embodiment and Embodiment 4 is that the high-entropy oxide is (Fe 0.2 Co 0.2 Ni 0.2 Al 0.2 Cr 0.2 O x ) 0.5 ·(SiO2) 0.5 , where 1 < x < 2 and the total valence is zero.

[0050] Example 10

[0051] As a lithium cobalt oxide cathode material coated with high-entropy oxide according to an embodiment of the present invention, the only difference between this embodiment and Embodiment 4 is that the high-entropy oxide is (Fe 0.2 Co 0.2 Mn 0.2 Al 0.2 Zn 0.2 O x ) 0.5 ·(SiO2) 0.5 , where 1 < x < 2 and the total valence is zero.

[0052] Example 11

[0053] As a lithium cobalt oxide cathode material coated with high-entropy oxide according to an embodiment of the present invention, the only difference between this embodiment and Embodiment 4 is that the high-entropy oxide is (Fe 0.2 Co 0.2 Ni 0.2 Al 0.2 Zn 0.2 O x ) 0.5 ·(SiO2) 0.5 , where 1 < x < 2 and the total valence is zero.

[0054] Example 12

[0055] As a lithium cobalt oxide cathode material coated with high-entropy oxide according to an embodiment of the present invention, the only difference between this embodiment and Embodiment 4 is that the high-entropy oxide is (Fe 0.2 Mn 0.2 Ni 0.2 Al 0.2 Cr 0.2 O x ) 0.5 ·(SiO2) 0.5 , where 1 < x < 2 and the total valence is zero.

[0056] Embodiment 13

[0057] As a lithium cobalt oxide cathode material coated with high-entropy oxide according to an embodiment of the present invention, the only difference between this embodiment and Embodiment 4 is that the high-entropy oxide is (Fe 0.2 Co 0.2 Ni 0.2 Mn 0.2 Cr 0.2 O x ) 0.5 ·(SiO2) 0.5 , where 1 < x < 2 and the total valence is zero.

[0058] Comparative Example 1

[0059] As a lithium cobalt oxide cathode material coated with high-entropy oxide according to a comparative example of the present invention, the only difference between this comparative example and Embodiment 4 is that the high-entropy oxide is (Fe 0.25 Co 0.25 Ni 0.25 Mn 0.25 O x ) 0.5 ·(SiO2) 0.5 , where 1 < x < 2 and the total valence is zero.

[0060] Comparative Example 2

[0061] As a lithium cobalt oxide cathode material coated with high-entropy oxide according to a comparative example of the present invention, the only difference between this comparative example and Embodiment 4 is that the high-entropy oxide is (Fe 0.25 Co 0.25 Ni 0.25 Al 0.25 O x ) 0.5 ·(SiO2) 0.5 , where 1 < x < 2 and the total valence is zero.

[0062] Comparative Example 3

[0063] As a lithium cobalt oxide cathode material coated with high-entropy oxide in the comparative example of the present invention, the only difference between this comparative example and Example 4 is that the high-entropy oxide is (Fe 0.25 Co 0.25 Al 0.25 Mn 0.25 O x ) 0.5 ·(SiO2) 0.5 , where 1 < x < 2 and the total valence is zero.

[0064] Comparative Example 4

[0065] As a lithium cobalt oxide cathode material coated with high-entropy oxide in the comparative example of the present invention, the only difference between this comparative example and Example 4 is that the high-entropy oxide is (Fe 0.25 Al 0.25 Ni 0.25 Mn 0.25 O x ) 0.5 ·(SiO2) 0.5 , where 1 < x < 2 and the total valence is zero.

[0066] Comparative Example 5

[0067] As a lithium cobalt oxide cathode material coated with high-entropy oxide in the comparative example of the present invention, the only difference between this comparative example and Example 4 is that the high-entropy oxide is (Al 0.25 Co 0.25 Ni 0.25 Mn 0.25 O x ) 0.5 ·(SiO2) 0.5 , where 1 < x < 2 and the total valence is zero.

[0068] Comparative Example 6

[0069] As a lithium cobalt oxide cathode material coated with high-entropy oxide in the comparative example of the present invention, the only difference between this comparative example and Example 4 is that the high-entropy oxide is Fe 0.1 Co 0.2 Ni 0.2 Mn 0.2 Al 0.2 Cr 0.1 O x , where 1 < x < 2 and the total valence is zero.

[0070] Comparative Example 7

[0071] As a lithium cobalt oxide cathode material coated with high-entropy oxide in the comparative example of the present invention, the only difference between this comparative example and Example 4 is that the high-entropy oxide is Fe 0.1 Co 0.2 Ni0.2 Mn 0.2 Al 0.2 Zn 0.1 O x , where 1 < x < 2 and the total valence is zero.

[0072] Comparative Example 8

[0073] As a lithium cobalt oxide cathode material coated with a high-entropy oxide as a comparative example of the present invention, the only difference between this comparative example and Example 4 is that the high-entropy oxide is Fe 0.1 Co 0.2 Ni 0.2 Mn 0.2 Cr 0.2 Zn 0.1 O x , where 1 < x < 2 and the total valence is zero.

[0074] Comparative Example 9

[0075] As a lithium cobalt oxide cathode material coated with a high-entropy oxide as a comparative example of the present invention, the only difference between this comparative example and Example 4 is that the high-entropy oxide is Fe 0.1 Co 0.2 Ni 0.2 Al 0.2 Cr 0.2 Zn 0.1 O x , where 1 < x < 2 and the total valence is zero.

[0076] Comparative Example 10

[0077] As a lithium cobalt oxide cathode material coated with a high-entropy oxide as a comparative example of the present invention, the only difference between this comparative example and Example 4 is that the high-entropy oxide is Fe 0.1 Co 0.2 Mn 0.2 Al 0.2 Cr 0.2 Zn 0.1 O x , where 1 < x < 2 and the total valence is zero.

[0078] Comparative Example 11

[0079] As a lithium cobalt oxide cathode material coated with a high-entropy oxide as a comparative example of the present invention, the only difference between this comparative example and Example 4 is that the high-entropy oxide is Fe 0.1 Ni 0.2 Mn 0.2 Al 0.2 Cr 0.2 Zn 0.1 O x , where 1 < x < 2 and the total valence is zero.

[0080] Comparative Example 12

[0081] As a lithium cobaltate cathode material coated with high-entropy oxide as a comparative example of the present invention, the only difference between this comparative example and Example 4 is that the high-entropy oxide is Co 0.2 Ni 0.2 Mn 0.2 Al 0.2 Cr 0.1 Zn 0.1 O x , where 1 < x < 2 and the total valence is zero.

[0082] Experimental method

[0083] I. Material characterization

[0084] As Figure 1 is the TEM image of Example 6. It can be clearly seen from the figure that there is a continuous nano-coating layer on the surface of the matrix, and the thickness ranges from a few nanometers to several hundred nanometers. Figure 2 is the HRTEM image of Example 6. It can be clearly seen from the figure that the coating layer here is below 20 nm, continuous and dense, and the coating effect is good.

[0085] II. Electrochemical performance test uses a half-cell (3.0V - 4.3V), and the key parameters are as follows:

[0086] 1) Cathode material: SP:PVDF = 80:10:10

[0087] 2) Anode: Lithium foil

[0088] 3) Electrolyte: 1.0 M LiPF6 (DMC:EC:EMC = 1:1:1 Vol%)

[0089] The experimental results of the electrochemical performance are shown in Table 1.

[0090] Table 1 Performance of lithium cobaltate cathode material coated with high-entropy oxide

[0091]

[0092]

[0093] From Table 1 and Figure 3 the results show that the lithium cobaltate cathode material coated with high-entropy oxide of the present invention is obtained by sintering and coating the lithium cobaltate material with high-entropy oxide, forming a lithium cobaltate cathode material with the lithium cobaltate material as the core and the high-entropy oxide as the coating layer. The chemical formula of the high-entropy oxide is MO x, where M contains at least six of Fe, Co, Ni, Mn, Al, Cr, Zn, and Si, which can not only improve the discharge capacity and cycling performance of the lithium cobalt oxide cathode material, but also significantly improve the rate performance of the lithium cobalt oxide.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A high entropy oxide coated lithium cobalt oxide positive electrode material, characterized in that: The high entropy oxide coated lithium cobalt oxide positive electrode material includes lithium cobalt oxide located inside the material and a coating layer coated on the surface of the lithium cobalt oxide. The chemical formula of the lithium cobalt oxide located inside the material is LiCo a Tm 1-a O2, where 0.99≤a≤0.999, Tm is at least one of Mg, Al, Ti, Sr, Zr, Mo, and Nb; the coating layer is a high entropy oxide coating layer, and the chemical formula of the high entropy oxide is MO x , wherein M includes at least 6 of Fe, Co, Ni, Mn, Al, Cr, Zn, and Si and must include Si.

2. The high entropy oxide coated lithium cobalt oxide positive electrode material according to claim 1, characterized in that: The content of the coating layer in the high entropy oxide coated lithium cobalt oxide positive electrode material is 0.1% to 1%.

3. The high entropy oxide coated lithium cobalt oxide positive electrode material according to claim 1, characterized in that: Among them, M includes at least 6 of Fe, Co, Ni, Mn, Al, Cr, Zn, and Si and must include Si, Fe, Co, and Ni.

4. The high entropy oxide coated lithium cobalt oxide positive electrode material according to claim 1, characterized in that: The thickness of the coating layer is 1 nm to 500 nm.

5. The high entropy oxide coated lithium cobalt oxide positive electrode material according to claim 1, characterized in that: The thickness of the coating layer is 5 nm to 100 nm.

6. The high entropy oxide coated lithium cobalt oxide positive electrode material according to claim 1, characterized in that: The content of the coating layer in the high entropy oxide coated lithium cobalt oxide positive electrode material is 0.1% to 0.5%.

7. The method for preparing a high entropy oxide-coated lithium cobalt oxide positive electrode material according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: (1) The lithium source, the cobalt source, and the Tm source are weighed and mixed in the required stoichiometric ratio and then subjected to the first heat treatment to obtain the lithium cobalt oxide matrix material LiCo a Tm 1-a O2; the holding temperature of the first heat treatment is 940℃~1000℃, the holding time is 8~16 hours, the heating rate is 3~5℃ / min, and the sintering atmosphere is air; (2) Lithium cobalt oxide matrix material and MO x The source materials are mixed uniformly according to the mass ratio and then subjected to a second heat treatment to obtain a high entropy oxide-coated lithium cobalt oxide positive electrode material; the second heat treatment has a holding temperature of 750°C to 850°C, a holding time of 6 to 12 hours, a heating rate of 3 to 5°C / min, and an air sintering atmosphere.

8. The method for preparing a high entropy oxide-coated lithium cobalt oxide positive electrode material according to claim 7, characterized in that: The lithium source is one or both of lithium carbonate and lithium hydroxide; the cobalt source is one or both of its oxide and carbonate and the particle size of the cobalt source satisfies 3.5μm≤D50≤5.5μm; the Tm source is one or more of its oxide, hydroxide and carbonate.

9. The method for preparing a high entropy oxide-coated lithium cobalt oxide positive electrode material according to claim 7, characterized in that: The M source is a nano-oxide of a corresponding element and the particle size satisfies D50≤2.0 μm.

10. A lithium ion secondary battery, characterized in that: The lithium-ion secondary battery comprises the high-entropy oxide-coated lithium cobalt oxide positive electrode material as claimed in any one of claims 1 to 6.

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