Coated modified positive electrode material and preparation method therefor

Abstract

A coated modified positive electrode material and a preparation method therefor. The preparation method for the coated modified positive electrode material comprises the following steps: mixing a lithium source, a precursor and a compound containing M, and performing calcining, crushing and sieving to obtain a sintered product; and putting the obtained sintered product and a compound containing M' into a reaction kettle for stirring, and performing stepwise heating, continuous stirring and cooling to obtain the coated modified positive electrode material. The coated modified positive electrode material has a uniform surface coating, less floating powder and the like, simple and mild preparation conditions, significantly reduced manufacturing processes, more controllable quality stability, and low manufacturing cost, and is more environmentally friendly. The prepared lithium-ion battery interface is relatively more stable, and has advantages in performance such as service life and gas production without affecting capacity.

Description

A coated modified positive electrode material and preparation method thereof Technical Field

[0001] The present application belongs to the technical field of lithium-ion battery materials, and specifically relates to a coated modified positive electrode material and a preparation method thereof. Background Art

[0002] Since its commercialization, lithium-ion batteries have been widely used in portable devices, electric vehicles, and energy storage due to their high energy density, long cycle life, and environmental friendliness. As a key component of lithium-ion batteries, cathode materials have a crucial impact on their performance and account for the majority of their cost. The performance and price of cathode materials significantly impact the development and large-scale application of lithium-ion batteries.

[0003] Taking lithium cobalt oxide as an example, as the demand for energy density increases, the cut-off voltage of lithium cobalt oxide is also getting higher and higher. Increasing the upper limit voltage of charging (excessive delithiation) will bring a series of problems, such as material phase change, interface side reactions, cobalt metal dissolution, oxygen evolution, etc., which will lead to rapid degradation of material performance, especially cycle performance. The surface reaction activity of lithium cobalt oxide is higher than that of the bulk phase. During the charging process on its surface, the surface of lithium cobalt oxide first releases Li + , Li + After the release, the O atoms lose the cation barrier and repel each other, and the surface structure becomes unstable. + Continuous release of oxygen increases the activity of lattice oxygen on the surface to a certain extent, and oxygen evolution occurs. After oxygen evolution occurs, the stability of Co atoms on the surface deteriorates and dissolves. The high-valent element Co 4+ At the same time, it oxidizes the electrolyte, directly participates in the chemical reaction and dissolves into the electrolyte. Coating and modifying the surface of lithium cobalt oxide is an effective strategy to improve the cycle life. The current method of lithium cobalt oxide coating and modification is mainly solid-phase coating, that is, sintered lithium cobalt oxide is mixed with modified additives, and then calcined twice, and then crushed and batched to become the finished lithium cobalt oxide product. However, the energy consumption required for secondary calcination is high, the process is complex, and the secondary crushing is easy to damage the surface of the material, thereby affecting the stability and service life of lithium cobalt oxide.

[0004] Summary of the Invention

[0005] The present application aims to provide a coated modified positive electrode material and a preparation method thereof. The present application adopts a mechanochemical method to replace conventional nano-oxide additives and high-temperature solid-phase synthesis methods, overcoming the defects of the warm solid-phase synthesis method, such as high energy consumption, complex process, and poor stability of the prepared positive electrode material. The surface coating of the positive electrode material prepared by the present application is uniform, with less floating powder, etc., and the preparation conditions are simple and mild, the manufacturing process is significantly reduced, the quality stability is more controllable, and the manufacturing cost is low, and it is more environmentally friendly. The prepared lithium-ion battery interface is relatively more stable, and without affecting the capacity, the performance such as life and gas production has advantages.

[0006] In order to achieve the above-mentioned purpose, the present application adopts the following technical solution: a method for preparing a coated modified positive electrode material, comprising the following steps:

[0007] The lithium source, the precursor and the M-containing compound are mixed, calcined, crushed and sieved to obtain a sintered product;

[0008] The obtained sintered product and the compound containing M′ are placed in a reaction kettle, stirred, heated in steps, stirred continuously, and cooled to obtain the coated modified positive electrode material;

[0009] The precursor is an oxide, hydroxide or carbonate containing at least one element among nickel, cobalt and manganese;

[0010] The M-containing compound is at least one of a nano-scale oxide containing M and a hydroxide containing M, wherein M is at least one element selected from aluminum, magnesium, titanium, zirconium, lanthanum, yttrium, and tungsten;

[0011] The compound containing M' is a metal organic salt containing M', wherein M' is at least one element selected from aluminum, nickel, magnesium, titanium, zirconium, manganese, lanthanum, yttrium and selenium.

[0012] As an embodiment of the preparation method of the coated modified positive electrode material described in the present application, the molar ratio of Li in the lithium source, the element in the precursor, and the M element in the M-containing compound is (1.05-1.1):1:(0.01-0.05).

[0013] As an embodiment of the method for preparing the coated modified positive electrode material described in the present application, the lithium source includes at least one of lithium hydroxide and lithium carbonate.

[0014] As an embodiment of the method for preparing the coated modified positive electrode material described in the present application, the metal organic salt includes at least one of oxalate metal salt, acetate metal salt, and methanol metal salt.

[0015] As an embodiment of the method for preparing the coated modified positive electrode material described in the present application, the molar ratio of the sintered product to the compound containing M′ is 9-10.

[0016] In this application, a metal organic salt containing M′ is solid-phase mixed with a sintered material (lithium cobalt oxide). Under appropriate temperature conditions, the characteristics of weak molecular interaction, easy opening and low melting point in the organic metal salt are utilized to achieve rapid and uniform coating of the positive electrode material at a lower temperature.

[0017] As an embodiment of the method for preparing the coated modified positive electrode material described in the present application, the particle size of the sintered product is 2 to 24 μm.

[0018] As an embodiment of the method for preparing the coated modified positive electrode material described in the present application, the calcination temperature is 600-1200°C.

[0019] As an embodiment of the method for preparing the coated modified positive electrode material described in the present application, the stirring time is 0.5 to 2 hours.

[0020] As an embodiment of the preparation method of the coated modified positive electrode material described in this application, the step-by-step heating includes two heating stages; the temperature of the first stage is 200-300°C, and the heating rate is 3-5°C / min; the temperature of the second stage is 400-800°C, and the heating rate is 3-5°C / min.

[0021] The first heating stage reaches the thermal decomposition temperature of the metal organic salt, while the second heating stage reaches the reaction temperature between the metal ions and the cathode material surface. The heating rates of the two heating stages can be consistent or inconsistent. When the heating rates of the two heating stages are inconsistent, the heating rate of the first stage is slightly lower than that of the second stage. The heating rates of both heating stages increase from slow to fast.

[0022] As an embodiment of the method for preparing the coated modified positive electrode material described in the present application, the continuous stirring time is 2 to 8 hours.

[0023] The present invention's method for preparing a coated modified cathode material uses a compound containing M' to coat the sintered material. M' first decomposes upon heating to release the corresponding metal ions, which then solid-dissolve with the surface of the layered cathode material at relatively low temperatures, forming a uniform and smooth coating. This stabilizes the material interface, improves the cathode material's stability under high voltage, and inhibits phase transitions and metal dissolution at the interface under high voltage. This significantly improves the high-temperature cycling of lithium-ion batteries, as well as their high-temperature storage and gas production performance. Furthermore, XRD testing confirms that the bulk of the layered cathode material remains unchanged.

[0024] The present application also seeks to protect a coated modified positive electrode material prepared by the method for preparing the coated modified positive electrode material.

[0025] As an embodiment of the coated modified positive electrode material of the present application, the coated modified positive electrode material comprises a positive electrode material layer and a coating layer, wherein the chemical formula of the positive electrode material layer is Li1(Ni (1-m-n) Co n Mn m ) 1-a M a O2, wherein M is at least one element selected from aluminum, magnesium, titanium, zirconium, lanthanum, yttrium, and tungsten, 0≤m≤1, 0≤n≤1, 0<a≤0.1; the chemical formula of the coating layer is LiM′O2, wherein M′ is at least one element selected from aluminum, nickel, magnesium, titanium, zirconium, manganese, lanthanum, yttrium, and selenium.

[0026] As an embodiment of the coated modified positive electrode material of the present application, the LiM′O2 is a solid solution, uniformly and smoothly coated on the Li1(Ni (1-m-n) Co n Mn m ) 1-a M a O2 surface.

[0027] As an embodiment of the coated modified positive electrode material described in the present application, the molar ratio of the positive electrode material layer to the coating layer is (1-b):b, wherein 0<b≤0.1.

[0028] As an implementation of the coated modified positive electrode material described in the present application, the coating layer is a nano-scale island-shaped coating layer.

[0029] As an embodiment of the coated modified positive electrode material described in the present application, the particle size of the coated modified positive electrode material is 2 to 24 μm.

[0030] As an embodiment of the coated modified positive electrode material described in the present application, the M is at least one element selected from aluminum, titanium, lanthanum, yttrium, and tungsten.

[0031] As an embodiment of the coated modified positive electrode material described in the present application, the M′ is at least one element selected from aluminum, nickel, magnesium, titanium, manganese, and yttrium.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) The coated modified positive electrode material prepared in the present application, by introducing the M element, metal doping replaces the Co / Ni / Mn position in the positive electrode material, and utilizing its higher binding energy with oxygen, can effectively inhibit the change of the Co / Ni / Mn valence state, inhibit the escape of lattice oxygen and the dissolution of metal, and improve the stability of the positive electrode material under high voltage and high temperature.

[0034] (2) The coated modified positive electrode material prepared in the present application, through the introduction of M' element, combines with the residual lithium on the surface to generate LiM'O2 with higher reaction activity to replace the positive electrode material interface to react with the electrolyte, etc., and due to the introduction of higher valence elements, electron holes are formed in the highly delithiated state of the positive electrode material, which greatly increases the electronegativity, inhibits the escape of lattice oxygen at the material interface, and maintains the stability of the positive electrode material interface.

[0035] (3) The coated modified positive electrode material prepared in the present application uses metal organic salts instead of existing metal oxides and hydroxides for coating, and uses the intermolecular force in the metal organic salts as the main bonding method. It is easy to open under the combined action of low temperature and shear force, has low requirements for reaction conditions, is easier to react, and under the action of uninterrupted shear force, the material keeps rotating, the reaction is more uniform, and the coating layer is also more uniform.

[0036] (4) The preparation method of the coated modified positive electrode material of the present application has mild conditions, simple operation, short synthesis cycle, few steps, and is environmentally friendly. Moreover, since the reaction temperature of the synthetic material is low, there is no need for secondary sintering, secondary crushing and mixed batching, and the damage to the material surface is relatively small. While stabilizing the interface of lithium cobalt oxide and improving the cycle life and gas production performance of the positive electrode material, it can significantly reduce the manufacturing cost of the positive electrode material, achieve the purpose of energy saving and consumption reduction, cost reduction and efficiency improvement, and can be used in large-scale batches. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] FIG1 is a SEM image of the coated modified positive electrode material prepared in Example 1 of the present application.

[0038] FIG2 is a SEM image of the coated modified positive electrode material prepared in Example 2 of the present application.

[0039] FIG3 is a SEM image of the coated modified positive electrode material prepared in Example 3 of the present application.

[0040] FIG4 is an XRD diagram of the coated modified positive electrode material prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0041] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0042] In the Examples and Comparative Examples, the experimental methods used are conventional methods unless otherwise specified, and the materials and reagents used are commercially available unless otherwise specified.

[0043] Example 1

[0044] Lithium carbonate, cobalt trioxide, and nano-magnesium oxide were weighed in a ratio of 1.07:1:0.01, uniformly mixed, and placed in a box furnace. The mixture was heated to 1050°C at a heating rate of 3°C / min and kept at that temperature for 10 hours to obtain a sintered material. The sintered material was naturally cooled to room temperature, and then coarsely crushed and pulverized to obtain a lithium cobalt oxide semi-finished product with a particle size of 2 to 24 μm.

[0045] The lithium cobalt oxide semi-finished product and aluminum oxalate were weighed in a molar ratio of 1:0.01, and then put into a heating reactor. They were first mixed at a linear rate of 21 m / s for 30 minutes, and then the reactor was heated to 200°C at a rate of 3°C / min while keeping the stirring linear rate unchanged. The mixture was then stirred for 2 hours, and then the temperature was raised to 400°C at a heating rate of 5°C / min while keeping the stirring linear rate unchanged. After stirring for 3 hours, the material was discharged, cooled naturally to room temperature, and sieved to obtain the coated modified positive electrode material (lithium cobalt oxide finished product) with a particle size of 2 to 24 μm.

[0046] Example 2

[0047] Lithium hydroxide, nickel cobalt manganese hydroxide, nano-lanthanum oxide, and nano-zirconium oxide were weighed in a molar ratio of 1.05:1:0.01:0.01, mixed evenly, and then sintered in a box furnace. The temperature was raised to 900°C at a heating rate of 3°C / min and kept warm for 8 hours to obtain a sintered material. After naturally cooling to room temperature, the ternary semi-finished product with a particle size of 2 to 15 μm was obtained after coarse crushing and pulverization.

[0048] The ternary semi-finished material, titanium methylate and aluminum oxalate were weighed in a molar ratio of 1:0.01:0.01, and the weighed material was put into a heating reactor and mixed at a linear speed of 18 m / s for 1 hour. After completion, the reactor was heated and heated to 200°C at a rate of 3°C / min while keeping the stirring linear speed unchanged and stirring for 2 hours. The temperature was then raised to 600°C at a heating rate of 5°C / min while keeping the stirring linear speed unchanged and stirring for 3 hours. The material was then discharged, naturally cooled to room temperature in a dry environment, and sieved to obtain the coated modified positive electrode material (uniformly coated ternary positive electrode material finished product) with a particle size of 2 to 15 μm.

[0049] Example 3

[0050] The preparation method of the lithium cobalt oxide semi-finished product in this embodiment is the same as that in Example 1;

[0051] The lithium cobalt oxide semi-finished product obtained in Example 1 and titanium methoxide, aluminum oxalate, and magnesium acetate were weighed in a molar ratio of 1:0.01:0.01:0.005, and then put into a heating reactor. The mixture was first mixed at a linear rate of 21 m / s for 30 minutes, and then the reactor was heated to 200° C. at a rate of 3° C. / min while maintaining the stirring linear rate unchanged. The mixture was stirred for 2 hours, and then the temperature was raised to 600° C. at a heating rate of 5° C. / min while maintaining the stirring linear rate unchanged. After stirring for 3 hours, the material was discharged, naturally cooled to room temperature, and sieved to obtain a uniformly coated lithium cobalt oxide finished product with a particle size of 2 to 24 μm.

[0052] Example 4

[0053] Compared with Example 1, the only difference in this example is that the stirring time after the temperature is raised to 400° C. is 1 hour.

[0054] The preparation method is as in Example 1.

[0055] Example 5

[0056] Compared with Example 1, the only difference in this example is that the stirring time after the temperature is raised to 400° C. is 9 hours.

[0057] The preparation method is as in Example 1.

[0058] Comparative Example 1

[0059] Lithium carbonate, cobalt trioxide, and nano-magnesium oxide were weighed in a ratio of 1.07:1:0.01, uniformly mixed, and placed in a box furnace. The mixture was heated to 1050°C at a heating rate of 3°C / min and kept at that temperature for 10 hours to obtain a sintered material. The sintered material was naturally cooled to room temperature, and then coarsely crushed and pulverized to obtain a lithium cobalt oxide semi-finished product with a particle size of 2 to 24 μm.

[0060] The lithium cobalt oxide semi-finished product and aluminum oxalate were weighed in a molar ratio of 1:0.01, and then put into a heating reactor. They were first mixed at a linear rate of 21 m / s for 30 minutes, and then the reactor was heated to 400°C at a rate of 3°C / min, while the stirring linear speed was kept constant. After stirring for 3 hours, the material was discharged, cooled naturally to room temperature, and sieved to obtain the coated modified positive electrode material with a particle size of 2 to 24 μm.

[0061] Compared with Example 1, the only difference of this comparative example is that the heating process is directly heated to 400° C. at a rate of 3° C. / min.

[0062] Comparative Example 2

[0063] The preparation method of the lithium cobalt oxide semi-finished product is the same as that in Example 1;

[0064] The lithium cobalt oxide semi-finished product and nano-alumina were weighed in a molar ratio of 1:0.01, and then put into a heating reactor. They were first mixed at a linear rate of 21 m / s for 30 minutes, and then the reactor was heated to 400°C at a rate of 3°C / min, while the stirring linear speed was kept constant. After stirring for 3 hours, the material was discharged, cooled naturally to room temperature, and sieved to obtain the coated modified positive electrode material with a particle size of 2 to 24 μm.

[0065] Compared with Comparative Example 1, the difference of this comparative example is that nano-alumina is used for coating.

[0066] Comparative Example 3

[0067] The preparation method of the lithium cobalt oxide semi-finished product is the same as that in Example 1;

[0068] The lithium cobalt oxide semi-finished product and nano-alumina were weighed in a molar ratio of 1:0.01, then mixed in a common high-speed mixer, and then sintered for a second time according to a 5 kg potting amount. The temperature was raised to 800°C at a heating rate of 3°C / min, kept warm for 8 hours, cooled to room temperature, and then sieved to obtain the lithium cobalt oxide finished product.

[0069] Comparative Example 4

[0070] The preparation method of the ternary semi-finished product is the same as that of Example 2;

[0071] The ternary semi-finished product was weighed with nano-titanium oxide and nano-aluminum oxide in a molar ratio of 1:0.01:0.01, and then mixed in an ordinary high-speed mixer. Then, secondary sintering was performed according to a 5 kg potting amount. The temperature was raised to 600°C at a heating rate of 3°C / min, kept warm for 8 hours, cooled to room temperature, and the material was sieved to obtain the finished ternary positive electrode material.

[0072] Comparative Example 5

[0073] The preparation method of the lithium cobalt oxide semi-finished product is the same as that in Example 1;

[0074] The lithium cobalt oxide semi-finished product was weighed with nano-titanium oxide, nano-aluminum oxide and nano-magnesium oxide in a molar ratio of 1:0.01:0.01:0.005, and then mixed in a common high-speed mixer. Then, a secondary sintering was performed according to a 5 kg potting amount. The temperature was raised to 300° C. at a heating rate of 3° C. / min, kept warm for 4 hours, cooled to room temperature, and the material was sieved to obtain a lithium cobalt oxide finished product.

[0075] Comparative Example 6

[0076] Lithium carbonate, cobalt trioxide, nano-magnesium oxide, and aluminum oxalate were weighed in a ratio of 1.07:1:0.01:0.01, uniformly mixed, and placed in a box furnace. The mixture was heated to 1050°C at a heating rate of 3°C / min and kept at that temperature for 10 hours to obtain a sintered material. After naturally cooling to room temperature, the sintered material was coarsely crushed and pulverized to obtain a lithium cobalt oxide semi-finished product with a particle size of 2 to 24 μm.

[0077] The lithium cobalt oxide semi-finished product and aluminum oxalate were weighed in a molar ratio of 1:0.01, and then put into a heating reactor. They were first mixed at a linear rate of 21 m / s for 30 minutes, and then the reactor was heated to 200°C at a rate of 3°C / min while keeping the stirring linear rate unchanged. The mixture was then stirred for 2 hours, and then the temperature was raised to 400°C at a heating rate of 5°C / min while keeping the stirring linear rate unchanged. After stirring for 3 hours, the material was discharged and naturally cooled to room temperature. After sieving, a uniformly coated lithium cobalt oxide product with a particle size of 2 to 24 μm was obtained.

[0078] Performance Testing

[0079] 1. Electron microscopy was used to examine the structure of the cathode materials prepared in Examples 1-3 of the present application, and XRD analysis was also performed. The SEM images and XRD patterns of the cathode materials prepared in Examples 1-3 of the present application are shown in Figures 1-4.

[0080] As can be seen from Figures 1 to 4, the surface of the positive electrode material prepared in this application is smooth and flat, and the coating is uniform. The XRD diagram shows that the coated modified positive electrode material still has a clear lithium cobalt oxide structure, indicating that the coating material has not damaged the positive electrode material itself.

[0081] 2. The positive electrode materials, PVDF, and SuperP prepared in the embodiment and comparative example were mixed in a weight ratio of 94:3:3, and NMP was used as a solvent. The mixture was stirred and coated on aluminum foil, dried at 120°C, and then rolled to form a positive electrode sheet. Graphite was used as the negative electrode and coated on copper foil, which was wound to form a soft-pack battery cell. The capacity, cycle, storage, and gas production tests were carried out in a Xinwei test cabinet.

[0082] The performance test results are shown in Table 1.

[0083] Table 1

[0084] From the experimental data in Table 1, it can be seen that the coated modified positive electrode material prepared in the present application can achieve higher electrochemical performance, and at the same time has good cyclability and stability.

[0085] Comparison between Example 4 and Example 1 shows that when the reaction stirring time is short, the overall capacity of the material will be improved, but the circulation, storage, and gas production will deteriorate significantly; comparison between Example 5 and Example 1 shows that when the reaction stirring time is long, the overall capacity of the material will decrease, and there will be no obvious improvement in circulation, storage, and gas production, which indicates that too long or too short a reaction stirring time will have an adverse effect on the comprehensive performance of the material.

[0086] Comparative Example 1 adopts non-step temperature coating during the preparation process. The heating process is directly heated to 400°C at a rate of 3°C / min. The capacity of the positive electrode material obtained is equivalent to that of Example 1, but the circulation, gas production and storage performance are slightly worse. This shows that after the platform temperature of 200°C is cancelled, the metal organic oxide decomposes too quickly, and some of the substances produced affect the bonding between the metal and the material surface, and the modification effect is reduced.

[0087] In Comparative Example 2, nano-metal oxides were used for coating, and the performance of the obtained positive electrode material was significantly worse than that of the embodiment.

[0088] Comparative Example 3, compared to Example 1, Comparative Example 4, compared to Example 2, and Comparative Example 5, compared to Example 3, employ a conventional high-temperature solid-phase method for preparation. The resulting cathode materials exhibit substantially the same performance as in the Examples. This demonstrates that the mechanochemical method of the present application can achieve the same results as the currently commonly used high-temperature solid-phase method at lower temperatures, and that the preparation method of the present application employs more moderate conditions and a shorter cycle time.

[0089] Comparative Example 6 uses metal organic salt doping, and the performance of the prepared positive electrode material is worse than that of the embodiment.

Claims

1. A method for preparing a coated modified positive electrode material, characterized in that: The following steps are involved: The lithium source, the precursor and the compound containing M are mixed, calcined, crushed and sieved to obtain a sintered product; The obtained sintered product and the compound containing M′ are put into a reaction kettle, stirred, heated in steps, stirred continuously, and cooled to obtain the coated modified positive electrode material; The precursor is an oxide, hydroxide or carbonate containing at least one element of nickel, cobalt and manganese; The compound containing M is at least one of a nano-scale oxide containing M and a hydroxide containing M, wherein M is at least one element selected from aluminum, magnesium, titanium, zirconium, lanthanum, yttrium, and tungsten; The compound containing M' is a metal organic salt containing M', wherein M' is at least one element selected from aluminum, nickel, magnesium, titanium, zirconium, manganese, lanthanum, yttrium and selenium.

2. The method for preparing the coated modified positive electrode material according to claim 1, characterized in that: The molar ratio of Li in the lithium source, the element in the precursor, and the M element in the M-containing compound is (1.05-1.1):1:(0.01-0.05).

3. The method for preparing the coated modified positive electrode material according to claim 1, characterized in that: The molar ratio of the sintered product to the compound containing M' is 9-10.

4. The method for preparing the coated modified positive electrode material according to claim 1, characterized in that: The lithium source includes at least one of lithium hydroxide and lithium carbonate.

5. The method for preparing the coated modified positive electrode material according to claim 1, characterized in that: The metal organic salt includes at least one of metal oxalate, metal acetate and metal methanol.

6. The method for preparing the coated modified positive electrode material according to claim 1, characterized in that: The particle size of the sintered product is 2 to 24 μm.

7. The method for preparing the coated modified positive electrode material according to claim 1, characterized in that: The calcination temperature is 600-1200°C.

8. The method for preparing the coated modified positive electrode material according to claim 1, characterized in that: The stirring time is 0.5 to 2 hours.

9. The method for preparing the coated modified positive electrode material according to claim 1, characterized in that: The step-by-step heating includes two heating stages; the temperature of the first stage is 200-300°C, and the heating rate is 3-5°C / min; the temperature of the second stage is 400-800°C, and the heating rate is 3-5°C / min.

10. The method for preparing the coated modified positive electrode material according to claim 1, characterized in that: The continuous stirring time is 2 to 8 hours.

11. A coated modified positive electrode material obtained by the method for preparing a coated modified positive electrode material according to any one of claims 1 to 10.

12. The coated modified positive electrode material according to claim 11, characterized in that: The coated modified positive electrode material comprises a positive electrode material layer and a coating layer, and the chemical formula of the positive electrode material layer is Li1(Ni (1-m-n) Co n Mn m ) 1-a M a O2, wherein M is at least one element selected from aluminum, magnesium, titanium, zirconium, lanthanum, yttrium, and tungsten, 0≤m≤1, 0≤n≤1, 0<a≤0.1; the chemical formula of the coating layer is LiM′O2, wherein M′ is at least one element selected from aluminum, nickel, magnesium, titanium, zirconium, manganese, lanthanum, yttrium, and selenium.

13. The coated modified positive electrode material according to claim 12, characterized in that: The LiM'O2 is a solid solution, coated on Li1(Ni (1-m-n) Co n Mn m ) 1-a M a O2 surface.

14. The coated modified positive electrode material according to claim 13, characterized in that: The molar ratio of the positive electrode material layer to the coating layer is (1-b):b, wherein 0<b≤0.

1.

15. The coated modified positive electrode material according to claim 12, characterized in that: The coating layer is a nano-scale island-shaped coating layer.

16. The coated modified positive electrode material according to claim 13, characterized in that: At least one of the following (1) to (3): (1) The particle size of the coated modified positive electrode material is 2 to 24 μm; (2) M is at least one element selected from aluminum, titanium, lanthanum, yttrium and tungsten; (3) The M′ is at least one element selected from aluminum, nickel, magnesium, titanium, manganese and yttrium.

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