Coated modified positive electrode material and preparation method thereof

Abstract

The application discloses a coated modified positive electrode material and a preparation method thereof. The preparation method of the coated modified positive electrode material comprises the following steps: mixing a lithium source, a precursor and a compound containing M, calcining, crushing, sieving, and preparing a sintered product; and putting the obtained sintered product and a compound containing M' into a reaction kettle, stirring, performing stepwise heating, continuously stirring, cooling, and preparing the coated modified positive electrode material. The coated modified positive electrode material is uniformly coated on the surface, has less floating powder, and has simple and mild preparation conditions, obvious reduction of manufacturing procedures, more controllable quality stability, low manufacturing cost, and more environmental friendliness. The prepared lithium ion battery has a relatively stable interface, and has advantages in service life and gas production performance under the premise of not affecting capacity performance.

Description

Technical Field

[0001] This application belongs to the field of lithium-ion battery material technology, specifically relating to a coated modified cathode material and its preparation method. Background Technology

[0002] Since the commercialization of lithium-ion batteries, they have been widely used in portable devices, electric vehicles, and energy storage due to their advantages such as high energy density, long cycle life, and environmental friendliness. Cathode materials, as a key component of lithium-ion batteries, have a crucial impact on battery performance and also account for a major portion of the cost. Therefore, the performance and price of cathode materials have a significant influence on the development and large-scale application of lithium batteries.

[0003] Taking lithium cobalt oxide as an example, as the demand for energy density increases, the cutoff voltage of lithium cobalt oxide is also increasing. Raising the upper limit of the charging voltage (excessive lithium delithiation) will bring a series of problems, such as material phase transitions, interfacial side reactions, cobalt metal dissolution, and oxygen evolution, leading to a rapid decline in material performance, especially cycle performance. The surface reactivity of lithium cobalt oxide is higher than that of the bulk phase; during charging on its surface, Li₂ is preferentially delithiated from the surface of the lithium cobalt oxide. + Li + After extraction, the O atoms lose the cation barrier and repulsion occurs, causing the surface structure to become unstable, as Li... + As oxygen continues to be extracted, the activity of lattice oxygen at the surface increases to a certain level, leading to oxygen evolution. After oxygen evolution occurs, the stability of Co atoms on the surface deteriorates, causing dissolution, and the high-valence element Co... 4+ Simultaneously, it oxidizes the electrolyte and directly participates in the chemical reaction, dissolving into the electrolyte. Coating and modifying the surface of lithium cobalt oxide is currently an effective strategy for improving cycle life. The main method for coating and modifying lithium cobalt oxide is solid-phase coating, which involves mixing sintered lithium cobalt oxide with modifying additives, followed by secondary calcination, and then secondary pulverization and batching to obtain the finished lithium cobalt oxide product. However, secondary calcination requires high energy consumption, is complex, and can easily damage the material surface during secondary pulverization, thus affecting the stability and service life of lithium cobalt oxide. Summary of the Invention

[0004] This application aims to provide a coated modified cathode material and its preparation method. This application employs a mechanochemical method instead of conventional nano-oxide additives and high-temperature solid-state synthesis methods, overcoming the shortcomings of high energy consumption, complex processes, and poor stability of the cathode material obtained by high-temperature solid-state synthesis methods. The cathode material prepared by this application has a uniform surface coating, less floating powder, and the preparation conditions are simple and mild, significantly reducing manufacturing steps, resulting in more controllable quality stability, lower manufacturing costs, and greater environmental friendliness. The prepared lithium-ion battery has a relatively more stable interface, and without affecting capacity, it exhibits advantages in lifespan and gas production performance.

[0005] To achieve the above object, the application adopts the following technical scheme: a preparation method of a coated modified positive electrode material, comprising the following steps:

[0006] mixing a lithium source, a precursor, and a compound containing M, calcining, crushing, sieving, and obtaining a sintered product;

[0007] putting the obtained sintered product and a compound containing M' into a reaction kettle, stirring, performing stepwise heating, continuously stirring, cooling, and obtaining the coated modified positive electrode material;

[0008] the precursor is an oxide, hydroxide, or carbonate containing at least one of nickel, cobalt, and manganese;

[0009] the compound containing M is at least one of a nano-sized oxide containing M and a hydroxide containing M, wherein M is at least one of aluminum, magnesium, titanium, zirconium, lanthanum, yttrium, and tungsten;

[0010] the compound containing M' is a metal organic salt containing M', wherein M' is at least one of aluminum, nickel, magnesium, titanium, zirconium, manganese, lanthanum, yttrium, and selenium.

[0011] As an embodiment of the preparation method of the coated modified positive electrode material, the molar ratio of Li in the lithium source, the elements in the precursor, and the M elements in the compound containing M is (1.05-1.1):1:(0.01-0.05).

[0012] As an embodiment of the preparation method of the coated modified positive electrode material, the lithium source comprises at least one of lithium hydroxide and lithium carbonate.

[0013] As an embodiment of the preparation method of the coated modified positive electrode material, the metal organic salt comprises at least one of a metal oxalate, a metal acetate, and a metal methanolate.

[0014] As an embodiment of the preparation method of the coated modified positive electrode material, the molar ratio of the sintered product to the compound containing M' is 9-10.

[0015] In the application, the metal organic salt containing M' is mixed with the sintered product (lithium cobaltate) in solid phase, and under suitable temperature conditions, the metal organic salt is characterized by weak molecular force, easy opening, and low melting point, so that the positive electrode material can be quickly and uniformly coated at a low temperature.

[0016] As an embodiment of the preparation method of the coated modified positive electrode material, the particle size of the sintered product is 2-24 μm.

[0017] As an embodiment of the preparation method of the coated modified positive electrode material, the temperature of the calcination is 600-1200°C.

[0018] As an embodiment of the preparation method of the coated modified positive electrode material, the time of the stirring is 0.5-2 hours.

[0019] As an embodiment of the preparation method of the coated modified positive electrode material, the stepwise 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.

[0020] The first heating stage is the thermal decomposition temperature of the metal organic salt, and the second heating stage is the reaction temperature of the metal ion and the surface of the positive electrode material. 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 the two heating stages are both from low to high.

[0021] As an embodiment of the preparation method of the coated modified positive electrode material, the time of the continuous stirring is 2-8 hours.

[0022] In the preparation method of the coated modified positive electrode material, a compound containing M' is used to coat the sintered product. M' is first decomposed by heat to free corresponding metal ions, which can be solid-solved with the surface of the layered positive electrode material at a lower temperature to form a uniform and smooth coating layer, thereby stabilizing the material interface, improving the stability of the positive electrode material at high voltage, inhibiting the phase change and metal dissolution of the interface at high voltage, and significantly improving the high-temperature cycle of the lithium ion battery and the high-temperature storage and gas production performance. XRD test shows that the main body of the layered positive electrode material remains unchanged.

[0023] The application also claims a coated modified positive electrode material prepared by the preparation method of the coated modified positive electrode material.

[0024] As an embodiment of the coated modified positive electrode material, the coated modified positive electrode material includes 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 aO2, wherein M is at least one element selected from aluminum, magnesium, titanium, zirconium, lanthanum, yttrium and tungsten, 0≤m≤1, 0≤n≤1, 0

[0025] As an embodiment of the coated modified positive electrode material described in the present application, the LiM'O2 is a solid solution, uniformly and smoothly coated on the surface of the Li1(Ni (1-m-n) Co n Mn m ) 1-a M a O2 surface.

[0026] 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

[0027] As an embodiment of the coated modified positive electrode material described in the present application, the coating layer is an island-shaped coating layer at nanometer level.

[0028] 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 2-24 μm.

[0029] 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.

[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, nickel, magnesium, titanium, manganese and yttrium.

[0031] Compared with the prior art, the present application has the following beneficial effects:

[0032] (1) The coated modified positive electrode material prepared in the present application can effectively inhibit the change of Co / Ni / Mn valence, inhibit the escape of lattice oxygen and the dissolution of metal, and improve the stability of the positive electrode material at high voltage and high temperature, by introducing M element, metal doping and replacing Co / Ni / Mn site in the positive electrode material, and using the higher binding energy with oxygen.

[0033] (2) The coated modified positive electrode material prepared in the present application can generate LiM'O2 with higher reactivity to replace the reaction between the positive electrode material interface and electrolyte, and due to the introduction of higher valence elements, electron holes are formed at high delithiation state of the positive electrode material, greatly increasing the electronegativity, inhibiting the escape of lattice oxygen at the material interface, and maintaining the stability of the positive electrode material interface.

[0034] (3) The coated modified positive electrode material prepared in the application is coated with metal organic salt instead of existing metal oxide and hydroxide, and the intermolecular force in the metal organic salt is used as the main combination mode. Under the combined action of low temperature and shear force, it is easy to open, the requirement for reaction condition is lower, and it is easier to react. Under the action of uninterrupted shear force, the material keeps rotating, the reaction is more uniform, and the coating layer is more uniform.

[0035] (4) The preparation method of the coated modified positive electrode material has mild conditions, simple operation, short synthesis cycle, few steps, is friendly to the environment, and has low synthesis material reaction temperature, so that secondary sintering, secondary crushing and batch mixing are not required, the surface of the material is less damaged, the interface of stable lithium cobalt oxide is stabilized, the cycle life and gas production performance of the positive electrode material are improved, the manufacturing cost of the positive electrode material is significantly reduced, the purposes of energy saving and consumption reduction, cost reduction and benefit increase are achieved, and the material can be used in large batches. BRIEF DESCRIPTION OF DRAWINGS

[0036] Fig. 1 SEM image of the coated modified positive electrode material prepared in Example 1 of the application.

[0037] Fig. 2 SEM image of the coated modified positive electrode material prepared in Example 2 of the application.

[0038] Fig. 3 SEM image of the coated modified positive electrode material prepared in Example 3 of the application.

[0039] Fig. 4 XRD image of the coated modified positive electrode material prepared in Example 1 of the application. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the application will be described below in conjunction with the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0041] In the examples and comparative examples, the experimental methods used are conventional methods unless otherwise specified, and the materials, reagents, etc. used are commercially available unless otherwise specified.

[0042] Example 1

[0043] According to 1.07:1:0.01, lithium carbonate, cobalt oxide and nano magnesium oxide are weighed, mixed uniformly, and then placed in a box furnace, heated to 1050℃ at a heating rate of 3℃ / min, and kept for 10 hours to obtain a sintered material. After natural cooling to room temperature, coarse breaking and crushing are carried out to obtain a lithium cobaltate semi-product with a particle size of 2-24μm;

[0044] The lithium cobaltate semi-product and aluminum oxalate are weighed according to a molar ratio of 1:0.01, and then put into a heated reaction kettle. First, mixing is carried out at a linear speed of 21m / s for 30min, and then the reaction kettle is heated to 200℃ at a rate of 3℃ / min while keeping the stirring linear speed unchanged. Then stirring is carried out for 2 hours, and then the temperature is raised to 400℃ at a heating rate of 5℃ / min while keeping the stirring linear speed unchanged. After stirring for 3 hours, the material is discharged, naturally cooled to room temperature, and sieved to obtain the coated modified positive electrode material (lithium cobaltate product) with a particle size of 2-24μm.

[0045] Example 2

[0046] According to a molar ratio of 1.05:1:0.01:0.01, lithium hydroxide, nickel-cobalt-manganese hydroxide, nano lanthanum oxide and nano zirconium oxide are weighed, mixed uniformly, and then placed in a box furnace for sintering. The temperature is raised to 900℃ at a heating rate of 3℃ / min, and kept for 8 hours to obtain a sintered material. After natural cooling to room temperature, coarse breaking and crushing are carried out to obtain a ternary semi-product with a particle size of 2-15μm.

[0047] The ternary semi-product material and titanium methoxide, aluminum oxalate are weighed according to a molar ratio of 1:0.01:0.01, and then put into a heated reaction kettle. First, mixing is carried out at a linear speed of 18m / s for 1h, and then the reaction kettle is heated to 200℃ at a rate of 3℃ / min while keeping the stirring linear speed unchanged. Then stirring is carried out for 2 hours, and then the temperature is raised to 600℃ at a heating rate of 5℃ / min while keeping the stirring linear speed unchanged. After stirring for 3 hours, the material is 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 product) with a particle size of 2-15μm.

[0048] Example 3

[0049] The preparation method of the lithium cobaltate semi-product in this example is the same as that in Example 1;

[0050] The lithium cobaltate semi-product obtained in Example 1 and titanium methoxide, aluminum oxalate, magnesium acetate are weighed according to a molar ratio of 1:0.01:0.01:0.005, and then put into a heated reaction kettle. First, mixing is carried out at a linear rate of 21 m / s for 30 min, and then the reaction kettle is heated to 200℃ at a rate of 3℃ / min while keeping the stirring linear rate unchanged. Stirring is carried out for 2 hours, and then the temperature is raised to 600℃ at a rate of 5℃ / min while keeping the stirring linear rate unchanged. After stirring for 3 hours, the material is discharged, and then naturally cooled to room temperature. A uniformly coated lithium cobaltate product is obtained after sieving, and the particle size is 2-24 μm.

[0051] Example 4

[0052] Compared with Example 1, the only difference of this example is that the stirring time after the temperature is raised to 400℃ is 1 h.

[0053] The preparation method is referred to Example 1.

[0054] Example 5

[0055] Compared with Example 1, the only difference of this example is that the stirring time after the temperature is raised to 400℃ is 9 h.

[0056] The preparation method is referred to Example 1.

[0057] Comparative Example 1

[0058] Lithium carbonate, tricobalt tetraoxide and nano magnesium oxide are weighed according to a ratio of 1.07:1:0.01, uniformly mixed, and then put into a box furnace. The temperature is raised to 1050℃ at a rate of 3℃ / min, and then kept for 10 hours to obtain a sintered material. After naturally cooling to room temperature, the sintered material is coarsely broken and crushed to obtain a lithium cobaltate semi-product with a particle size of 2-24 μm.

[0059] The lithium cobaltate semi-product and aluminum oxalate are weighed according to a molar ratio of 1:0.01, and then put into a heated reaction kettle. First, mixing is carried out at a linear rate of 21 m / s for 30 min, and then the reaction kettle is heated to 400℃ at a rate of 3℃ / min while keeping the stirring linear rate unchanged. After stirring for 3 hours, the material is discharged, and then naturally cooled to room temperature. The coated modified positive electrode material is obtained after sieving, and the particle size is 2-24 μm.

[0060] Compared with Example 1, the only difference of this example is that the temperature is directly raised to 400℃ at a rate of 3℃ / min during the heating process.

[0061] Comparative Example 2

[0062] The preparation method of the lithium cobaltate semi-product is the same as that of Example 1.

[0063] The lithium cobaltate semi-product and nano-alumina are weighed according to a molar ratio of 1:0.01, and then put into a heated reaction kettle. First, mixing is carried out at a linear rate of 21 m / s for 30 min, and then the reaction kettle is heated at a rate of 3 ℃ / min to 400 ℃. The stirring speed is kept constant, and the material is discharged after stirring for 3 hours. After natural cooling to room temperature, the material is sieved to obtain the coated modified positive electrode material with a particle size of 2-24 μm.

[0064] Compared with Comparative Example 1, the difference of the present comparative example is that nano-alumina is selected for coating.

[0065] Comparative Example 3

[0066] The preparation method of the lithium cobaltate semi-product is the same as that of Example 1.

[0067] The lithium cobaltate semi-product and nano-alumina are weighed according to a molar ratio of 1:0.01, and then mixed in a general high-speed mixer. Then, according to a 5 kg bowl loading, secondary sintering is carried out at a heating rate of 3 ℃ / min to 800 ℃, and the temperature is kept constant for 8 hours. After cooling to room temperature, the material is sieved to obtain the lithium cobaltate product.

[0068] Comparative Example 4

[0069] The preparation method of the ternary semi-product is the same as that of Example 2.

[0070] The ternary semi-product, nano-titanium oxide and nano-alumina are weighed according to a molar ratio of 1:0.01:0.01, and then mixed in a general high-speed mixer. Then, according to a 5 kg bowl loading, secondary sintering is carried out at a heating rate of 3 ℃ / min to 600 ℃, and the temperature is kept constant for 8 hours. After cooling to room temperature, the material is sieved to obtain the ternary positive electrode material product.

[0071] Comparative Example 5

[0072] The preparation method of the lithium cobaltate semi-product is the same as that of Example 1.

[0073] The lithium cobaltate semi-product, nano-titanium oxide, nano-alumina and nano-magnesium oxide are weighed according to a molar ratio of 1:0.01:0.01:0.005, and then mixed in a general high-speed mixer. Then, according to a 5 kg bowl loading, secondary sintering is carried out at a heating rate of 3 ℃ / min to 300 ℃, and the temperature is kept constant for 4 hours. After cooling to room temperature, the material is sieved to obtain the lithium cobaltate product.

[0074] Comparative Example 6

[0075] According to 1.07:1:0.01:0.01, lithium carbonate, tricobalt tetraoxide, nano magnesium oxide and aluminum oxalate are weighed, uniformly mixed and placed in a box furnace, heated to 1050℃ at a heating rate of 3℃ / min, and kept for 10 hours to obtain a sintered material, which is naturally cooled to room temperature, coarsely broken and crushed to obtain a lithium cobaltate semi-product with a particle size of 2-24μm;

[0076] The lithium cobaltate semi-product and aluminum oxalate are weighed according to a molar ratio of 1:0.01, and then put into a heated reaction kettle. First, mix at a linear speed of 21m / s for 30min, then heat the reaction kettle to 200℃ at a rate of 3℃ / min while keeping the stirring linear speed unchanged, then stir for 2 hours, then increase the temperature to 400℃ at a rate of 5℃ / min while keeping the stirring linear speed unchanged, and then discharge the material after stirring for 3 hours. After natural cooling to room temperature, a uniformly coated lithium cobaltate product with a particle size of 2-24μm can be obtained by sieving.

[0077] Performance test

[0078] 1. The positive electrode material prepared in Examples 1-3 is subjected to structural detection by electron microscopy, and XRD detection is also performed. The SEM and XRD graphs of the positive electrode material prepared in Examples 1-3 are shown in FIGS. 1-3. Figs. 1-4 .

[0079] From the attached Figs. 1-4 It can be seen that the positive electrode material prepared in the present application has a smooth and uniform surface, and the XRD graph shows that the coated modified positive electrode material still has a clear lithium cobaltate structure, indicating that the coating substance does not damage the positive electrode material itself.

[0080] 2. The positive electrode material prepared in the examples and comparative examples, PVDF, Super P are mixed according to a weight ratio of 94:3:3, NMP is used as a solvent, and is stirred and coated on an aluminum foil, dried at 120℃, then rolled to prepare a positive electrode sheet. Graphite is used as a negative electrode and coated on a copper foil, then wound to prepare a soft package battery cell, and the capacity, cycle, storage and gas production are tested in a new Wei test cabinet.

[0081] The performance test results are shown in Table 1.

[0082] Table 1

[0083]

[0084]

[0085] 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 high electrochemical performance, and has good cycle performance and stability.

[0086] Example 4 compared with Example 1 shows that when the stirring time of the reaction is shorter, the overall capacity of the material will be improved, but the cycle, storage and gas production will be deteriorated obviously; Example 5 compared with Example 1 shows that when the stirring time of the reaction is longer, the overall capacity of the material will be decreased, and the cycle, storage and gas production will be deteriorated slightly, which indicates that too long or too short stirring time of the reaction will bring adverse effects on the comprehensive performance of the material.

[0087] Comparative Example 1 uses non-stepwise temperature coating in the preparation process, and the heating process is directly heated to 400℃ at a rate of 3℃ / min. The prepared positive electrode material has a capacity equivalent to that of Example 1, but the cycle, gas production and storage performance are slightly worse, which indicates that after canceling the platform temperature of 200℃, the metal organic oxide decomposes too fast, and part of the substances produced affect the combination of the metal and the surface of the material, so the modification effect is reduced.

[0088] In Comparative Example 2, nano metal oxide is used for coating, and the prepared positive electrode material has performance significantly worse than that of the examples.

[0089] Comparative Example 3 compared with Example 1, Comparative Example 4 compared with Example 2, and Comparative Example 5 compared with Example 3, the prepared positive electrode materials have performance basically consistent with the examples, which indicates that the mechanical chemical method at a lower temperature in the present application can achieve the same effect as the commonly used high-temperature solid-phase method, and the preparation method of the present application is more moderate and has a shorter cycle.

[0090] Comparative Example 6 uses metal organic salt doping, and the prepared positive electrode material has performance worse than that of the examples.

Claims

1. A method for producing a coated modified cathode material, characterized by, The method comprises the following steps: mixing a lithium source, a precursor, and a compound containing M, calcining, crushing, sieving, and obtaining a sintered product; putting the sintered product and a compound containing M' into a reactor, stirring, heating in a stepwise manner, continuously stirring, cooling, and obtaining the coated modified positive electrode material; the stepwise heating comprises two heating stages; the first stage is at a temperature of 200-300℃ and a heating rate of 3-5℃ / min; then stirring for 2 hours; the second stage is at a temperature of 400-800℃ and a heating rate of 3-5℃ / min; then stirring for 2-8 hours; the precursor is an oxide, hydroxide, or carbonate containing at least one of nickel, cobalt, and manganese; the compound containing M is at least one of a nano-sized oxide containing M and a hydroxide containing M, wherein M is at least one of 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 of aluminum, nickel, magnesium, titanium, zirconium, manganese, lanthanum, yttrium, and selenium; the metal organic salt comprises at least one of a metal oxalate and a metal methanol salt.

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

3. The method of claim 1, wherein the coating modification of the cathode material is performed by a method selected from the group consisting of a wet method, a dry method, and a combination thereof. the lithium source comprises at least one of lithium hydroxide and lithium carbonate.

4. The method of claim 1, wherein the coating modification of the cathode material is performed by a method selected from the group consisting of a wet method, a dry method, and a combination thereof. the particle size of the sintered product is 2-24μm.

5. The method for preparing the coated modified cathode material as described in claim 1, characterized in that, the calcining temperature is 600-1200℃.

6. The method for preparing the coated modified cathode material as described in claim 1, characterized in that, the stirring time before the stepwise heating is 0.5-2 hours.

7. A coated modified positive electrode material prepared by the method of any one of claims 1-6.

8. The coating-modified positive electrode material according to claim 7, wherein The modified cathode material includes a cathode material layer and a coating layer, wherein the chemical formula of the cathode 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.

9. The coated and modified cathode material as described in claim 8, characterized in that, The LiM'02 is a solid solution coated on the surface of Li1(Ni (1-m-n) Co n Mn m ) 1-a M a O2.

10. The coated and modified cathode material as described in claim 8, characterized in that, the coating layer is an island-shaped coating layer at a nano level.

11. The coated and modified cathode material as described in claim 9, characterized in that, at least one of the following (1)-(3): (1) the particle size of the coated modified positive electrode material is 2-24μm; (2) M is at least one of aluminum, titanium, lanthanum, yttrium, and tungsten; (3) M' is at least one of aluminum, nickel, magnesium, titanium, manganese, and yttrium.

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