Lithium-rich manganese-based positive electrode material, preparation method and lithium ion battery

Abstract

The invention discloses a lithium-rich manganese-based positive electrode material, a preparation method and a lithium ion battery, the lithium-rich manganese-based positive electrode material comprises a matrix and a coating layer, the matrix is a cobalt-free lithium-rich manganese-based positive electrode material, and the coating layer comprises an oxide and a compound containing the element and lithium. Due to the existence of the coating layer in the embodiment of the invention, the positive electrode material and the electrolyte can be physically blocked, high-valence metal cations and active oxygen species on the surface of the material are prevented from reacting with the electrolyte, and the erosion of HF in the electrolyte can also be inhibited; the coating layer contains a compound corresponding to metal and / or nonmetal and lithium, so that the interface impedance can be reduced, good lithium ion conductivity is achieved, lithium ion deintercalation can be accelerated, more lithium ions can participate in electrochemical reaction, and the rate capability of the material can be improved; in addition, active oxygen species generated by charging can be limited in the material due to existence of the coating layer, oxygen escape is prevented, and then the problems that the lithium-rich manganese-based material is low in first-circle coulombic efficiency, poor in rate capability and cycling stability and the like are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-rich manganese-based positive electrode materials, and in particular to a lithium-rich manganese-based positive electrode material, a preparation method and a lithium ion battery. Background Art

[0002] Layered lithium-rich manganese-based materials are environmentally friendly positive electrode materials with high specific energy and high specific capacity, and are increasingly receiving widespread attention and in-depth research. In order to improve the electronic conductivity and ion mobility of lithium-rich manganese-based materials, cobalt elements are usually introduced. However, due to the scarcity of cobalt resources and uneven resource distribution, the price of cobalt sources is relatively high and has a certain impact on the environment. Therefore, underestimating or even cobalt-free layered positive electrode materials is conducive to further reducing the cost of lithium-rich manganese-based materials. However, the defects of decobaltized binary lithium-rich manganese-based positive electrode materials such as poor electronic conductivity and slow lithium ion migration rate seriously affect their performance, which is mainly manifested in large irreversible capacity in the first cycle, poor rate performance and cycle stability, etc. Among them, the capacity decay of the material and the drop in working voltage during the cycle are relatively serious problems, which restricts the widespread application of cobalt-free layered lithium-rich manganese-based positive electrode materials.

[0003] In order to solve the problem of poor cycle performance of cobalt-free layered lithium-rich manganese-based positive electrode materials, the present invention is specially proposed. Summary of the invention

[0004] The object of the present invention is to provide a lithium-rich manganese-based positive electrode material, a preparation method and a lithium-ion battery, so as to improve the cycle performance of the lithium-rich manganese-based positive electrode material.

[0005] The present invention is achieved in that:

[0006] In a first aspect, the present invention provides a lithium-rich manganese-based positive electrode material, comprising a substrate and an oxide-containing coating layer attached to at least a portion of the surface of the substrate, wherein the substrate is a cobalt-free lithium-rich manganese-based positive electrode material, and the coating layer comprises at least one of a first oxide and a second oxide, wherein the first oxide is selected from at least one of magnesium oxide, zinc oxide and nickel oxide, and the second oxide is selected from at least one of tungsten oxide, aluminum oxide, iron oxide, titanium oxide, zirconium oxide, lanthanum pentoxide, molybdenum oxide, copper oxide, niobium oxide and silicon dioxide.

[0007] In an optional embodiment, the coating layer includes two or more oxide layers, and the atomic radius of the elements in the two or more oxide layers gradually increases from the inside to the outside;

[0008] Preferably, the oxide layered layers include a first oxide layered layer composed of a first oxide and a second oxide layered layer composed of a second oxide layered layer.

[0009] In an optional embodiment, the mass ratio of the coating layer to the substrate is less than 2%.

[0010] In an optional embodiment, the matrix molecular formula is Li a [Ni x Mn 1-x ]O 2+b , where 1.1≤a≤1.5, 0 <x<0.5;

[0011] And / or, the matrix is ​​secondary particles formed by agglomeration of primary particles, and the secondary particles are spherical or quasi-spherical polycrystalline in shape;

[0012] And / or, the D50 of the substrate is 2um-15um;

[0013] In a second aspect, the present invention provides a method for preparing the lithium-rich manganese-based positive electrode material described in the aforementioned embodiment, comprising: sintering a mixture of a matrix and an oxide to obtain the lithium-rich manganese-based positive electrode material.

[0014] In an optional embodiment, it includes:

[0015] Mixing the substrate and the oxide used for the coating layer to obtain the mixture, and sintering the mixture to obtain the lithium-rich manganese-based positive electrode material;

[0016] Alternatively, the two or more oxides used for the substrate and the coating layer are mixed in sequence, the mixed materials are sintered after each mixing, and then the next mixing is performed. After the last sintering, the lithium-rich manganese-based positive electrode material with more than two oxide layers is obtained.

[0017] In an optional embodiment, the oxide D50 is 10-300 nm.

[0018] In an optional embodiment, the sintering temperature is 200°C-900°C, and the holding time is 60min-600min;

[0019] and / or, the heating rate before sintering is 1°C / min-10°C / min;

[0020] and / or, the sintering atmosphere is an oxygen-containing atmosphere;

[0021] And / or, after sintering, the sintered steel is cooled to 15°C-30°C at a rate of 1°C / min-10°C / min or cooled to 15°C-30°C along with the furnace.

[0022] In an optional embodiment, the mixing step temperature is 20°C-150°C, the speed is 50r / min-5000r / min, and the time is 20min-60min;

[0023] Preferably, the mixing step includes one-stage mixing, two-stage mixing and three-stage mixing, the one-stage mixing speed is 50r / min-5000r / min, and the time is 2min-30min; the two-stage mixing speed is 100r / min-300r / min, and the time is 2min-30min; the three-stage mixing speed is 300r / min-5000r / min, and the time is 20min-60min.

[0024] In a third aspect, the present invention provides a lithium-ion battery comprising the lithium-rich manganese-based positive electrode material described in any one of the aforementioned embodiments.

[0025] The present invention has the following beneficial effects:

[0026] The presence of the coating layer in the lithium-rich manganese-based positive electrode material of the present invention can physically block the positive electrode material and the electrolyte, prevent high-valent metal cations and active oxygen species on the surface of the material from reacting with the electrolyte, and can also inhibit the corrosion of HF in the electrolyte; the coating layer contains compounds of corresponding metals and / or non-metals and lithium, which can reduce the interface impedance, have good lithium ion conductivity, can accelerate the deintercalation of lithium ions, ensure that more lithium ions participate in the electrochemical reaction, and can improve the rate performance of the material; the presence of the coating layer can also limit the active oxygen species generated by charging to the inside of the material, prevent oxygen from escaping, and thereby alleviate the problems of low first-cycle coulomb efficiency, poor rate performance and cycle stability of the lithium-rich manganese-based material. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0028] Figure 1 This is a SEM image of the lithium-rich manganese-based positive electrode material prepared in Example 1;

[0029] Figure 2 This is a SEM image of the lithium-rich manganese-based positive electrode material prepared in Example 2;

[0030] Figure 3 1 is a cycle curve of the lithium-rich manganese-based positive electrode material prepared in each embodiment. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0032] An embodiment of the present invention provides a lithium-rich manganese-based positive electrode material, including a substrate and an oxide-containing coating layer attached to at least a portion of the surface of the substrate, wherein the substrate is a cobalt-free lithium-rich manganese-based positive electrode material, and the coating layer includes at least one of a first oxide and a second oxide, wherein the first oxide is selected from at least one of magnesium oxide, zinc oxide and nickel oxide, and the second oxide is selected from at least one of tungsten oxide, aluminum oxide, iron oxide, titanium oxide, zirconium oxide, lanthanum pentoxide, molybdenum oxide, copper oxide, niobium oxide and silicon dioxide.

[0033] In the embodiment of the present invention, two or more elements with different atomic radii are used to synergistically modify the matrix to improve the stability of the lithium-rich manganese positive electrode material. In the coating layer, the non-oxygen elements derived from the second oxide with a smaller atomic radius are more likely to enter the shallow pores of the matrix or penetrate into the shallow surface of the matrix, which is beneficial to improve the diffusion rate of lithium ions on the one hand, and on the other hand, it is beneficial to improve the bonding strength between the coating layer and the matrix; in addition, the non-oxygen elements derived from the first oxide with a larger atomic radius have relatively greater difficulty in entering the shallow pores of the matrix or penetrating into the shallow surface of the matrix, and can form lithium-containing compounds with the lithium source on the surface of the matrix during the preparation process, thereby improving the stability of the coating layer interface.

[0034] The presence of the coating layer in the embodiment of the present invention can physically block the positive electrode material and the electrolyte, prevent the high-valent metal cations and active oxygen species on the surface of the material from reacting with the electrolyte, and also inhibit the corrosion of HF in the electrolyte; the coating layer contains compounds of corresponding metals and / or non-metals and lithium, which can reduce the interface impedance, have good lithium ion conductivity, can accelerate the deintercalation of lithium ions, ensure that more lithium ions participate in the electrochemical reaction, and can improve the rate performance of the material; the presence of the coating layer can also limit the active oxygen species generated by charging to the inside of the material, prevent oxygen from escaping, and thereby alleviate the problems of low first-cycle Coulomb efficiency, poor rate performance and cycle stability of lithium-rich manganese-based materials.

[0035] In an optional embodiment, the coating layer includes two or more oxide layers, and the atomic radius of the elements in the two or more oxide layers gradually increases from the inside to the outside;

[0036] Preferably, the oxide layered layers include a first oxide layered layer composed of a first oxide and a second oxide layered layer composed of a second oxide layered layer.

[0037] Compared with the coating layer formed by a relatively uniform mixture of two or more oxides, each oxide independently forms an oxide layer on the surface of the matrix, which is more conducive to improving the cycle performance of the lithium-rich manganese-based positive electrode material.

[0038] In an optional embodiment, the mass ratio of the coating layer to the substrate is less than 2%, specifically 0.01%, 0.1%, 0.2%, 0.5%, 1%, 1.5%, 2% or any value less than 2%. If the coating layer accounts for too much, it may cause a decrease in capacity.

[0039] In an optional embodiment, the matrix molecular formula is Li a [Ni x Mn 1-x ]O 2+b , where 1.1≤a≤1.5, 0 <x<0.5。

[0040] In an optional embodiment, the matrix is ​​secondary particles formed by agglomeration of primary particles, and the secondary particles have a spherical or quasi-spherical polycrystalline morphology; compared with single-crystal lithium-manganese-based positive electrode materials as matrix, the matrix primary particles in the present invention have more pores, which is beneficial to increase the diffusion rate of lithium ions.

[0041] In an optional embodiment, the D50 of the matrix is ​​2um-15um, specifically 2um, 4um, 6um, 8um, 10um, 12um, 14um, 15um or any value between 2um-15um. If the matrix particle size is too large, the difficulty of lithium ion insertion and extraction increases, which is not conducive to the improvement of capacity.

[0042] An embodiment of the present invention further provides a method for preparing the lithium-rich manganese-based positive electrode material described in the aforementioned embodiment, comprising: sintering a mixture of a matrix and a metal oxide to obtain the lithium-rich manganese-based positive electrode material.

[0043] During the sintering process, the oxide is coated on the substrate, and a small amount of elements such as tungsten will enter the transition metal layer inside the material, replacing the transition metal elements and further improving the cycle stability; at the same time, the nano-oxide can react with the residual lithium on the surface of the cobalt-free lithium-rich manganese-based positive electrode material, thereby reducing the residual lithium on the surface of the substrate and improving the air stability and cycle stability of the material.

[0044] In an optional embodiment, the method comprises: mixing the substrate and the oxide used for the coating layer to obtain the mixture, and sintering the mixture to obtain the lithium-rich manganese-based positive electrode material. This preparation method is simple and is conducive to improving preparation efficiency.

[0045] In an optional embodiment, it includes: mixing two or more oxides used for the substrate and the coating layer in sequence, sintering the mixed materials after each mixing, and then mixing again, and after the last sintering, the lithium-rich manganese-based positive electrode material with more than two oxide layers is obtained.

[0046] When two oxides are coated on the substrate, the substrate and the oxides of metals and / or non-metals with smaller atomic radius are first mixed and sintered for the first time, and then the product of the first sintering is mixed with the oxides of metals and / or non-metals with relatively larger atomic radius and sintered for the second time to obtain a lithium-rich manganese-based positive electrode material with two oxide layers. This method can also be used when the oxide layers are three or four layers or even more. Although it is beneficial to improve the cycle performance, the preparation process is increased. It should be noted that when coating more than three oxides, the substrate can be first mixed with two oxides or one oxide and then sintered; the sintered material is mixed with the remaining oxides again and sintered again to obtain the lithium-rich manganese-based positive electrode material, that is, the type of oxide and the oxide layer do not necessarily correspond one to one, and two or more oxides can form an oxide layer.

[0047] The purpose of batch mixing is to allow some oxides with small atomic radius to enter the bulk phase from the surface during the sintering process, and oxides with large atomic radius can coat the surface of cobalt-free lithium-rich manganese-based positive electrode materials.

[0048] In an optional embodiment, the oxide D50 is 10nm-300nm, specifically 10nm, 50nm, 80nm, 100nm, 120nm, 200nm, 250nm, 300nm or any value between 10nm-300nm. The oxide is nanometer-scale, and a smaller particle size is conducive to relatively uniform attachment of the oxide to the surface of the substrate; however, if the particle size of the oxide is too small, on the one hand, the cost is higher, and on the other hand, it is easy to agglomerate, thereby reducing the uniformity of the coating.

[0049] In an optional embodiment, the sintering temperature is 200°C-900°C, specifically 200°C, 400°C, 600°C, 800°C, 900°C or any value between 200°C-900°C; the holding time is 60min-600min, specifically 60min, 90min, 120min, 180min, 240min, 300min, 400min, 500min, 600min or any value between 60min-600min. The sintering temperature is related to the melting point of the oxide, and preferably the sintering temperature is 400°C-900°C.

[0050] In an optional embodiment, the heating rate before sintering is 1°C / min-10°C / min;

[0051] In an optional embodiment, the sintering atmosphere is an oxygen-containing atmosphere;

[0052] In an optional embodiment, after sintering, the steel is cooled to 15°C-30°C at a rate of 1°C / min-10°C / min or cooled to 15°C-30°C along with the furnace.

[0053] The heating and cooling rates before and after sintering will affect the release of internal stress in the positive electrode material, which in turn will affect the cycle performance.

[0054] In an optional embodiment, the mixing step temperature is 20° C.-150° C., the rotation speed is 50 r / min-5000 r / min, and the time is 20 min-60 min to ensure that the materials can be fully mixed.

[0055] In an optional embodiment, the mixing step includes one-stage mixing, two-stage mixing and three-stage mixing, wherein the first-stage mixing speed is 50r / min-5000r / min, and the time is 2min-30min; the second-stage mixing speed is 100r / min-300r / min, and the time is 2min-30min; the third-stage mixing speed is 300r / min-5000r / min, and the time is 20min-60min. Gradually increasing the mixing speed during the mixing process is beneficial to reducing the failure rate of the mixing equipment. In some embodiments, in order to avoid a sharp increase in the system temperature due to excessively high speed, cooling water can be set to cool the equipment.

[0056] An embodiment of the present invention further provides a lithium-ion battery, comprising the lithium-rich manganese-based positive electrode material described in any one of the aforementioned embodiments.

[0057] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0058] Example 1

[0059] This embodiment provides a method for preparing a lithium-rich manganese-based positive electrode material, comprising the following steps:

[0060] 500g of cobalt-free lithium-rich manganese-based positive electrode material (structural formula Li 1.3 [Ni 0.3 Mn 0.4 ]O 2) was mixed with 0.25g (0.05%) magnesium oxide and 0.25g (0.05%) tungsten oxide using a high-speed mixer. The high-speed mixer was first operated at 60r / min for 10min at room temperature for premixing, then mixed at 200r / min for 15min, and finally mixed at 800r / min. The mixed materials were placed in a sagger, heated to 600℃ at a heating rate of 3℃ / min in an air atmosphere, kept warm for 5h, and naturally cooled to room temperature to obtain a lithium-rich manganese positive electrode base material. The SEM image is shown in Figure 1 shown.

[0061] Example 2

[0062] This embodiment provides a method for preparing a lithium-rich manganese-based positive electrode material, comprising the following steps:

[0063] 500g of cobalt-free lithium-rich manganese-based positive electrode material (structural formula Li 1.3 [Ni 0.3 Mn 0.4 ]O 2 ) and 0.5g (0.1%) zinc oxide and 0.5g (0.1%) zirconium oxide were mixed with a high-speed mixer. The high-speed mixer was first operated at 60r / min for 10min at 30°C for premixing, then mixed at 200r / min for 15min, and finally mixed at 800r / min. The mixed materials were placed in a sagger, heated to 600°C at a heating rate of 3°C / min in an air atmosphere, kept warm for 5h, and naturally cooled to room temperature to obtain a lithium-rich manganese positive electrode base material.

[0064] Embodiment 3,

[0065] This embodiment provides a method for preparing a lithium-rich manganese-based positive electrode material, comprising the following steps:

[0066] 500g of cobalt-free lithium-rich manganese-based positive electrode material (structural formula Li 1.3 [Ni 0.3 Mn 0.4 ]O 2 ) was mixed with 0.25g (0.05%) magnesium oxide and 0.25g (0.05%) molybdenum oxide using a high-speed mixer. The high-speed mixer was first operated at 60r / min for 10min at 50°C for premixing. Then it was mixed at a speed of 200r / min for 15min, and finally mixed at a speed of 800r / min. The mixed material was placed in a sagger, heated to 600°C at a heating rate of 3°C / min in an air atmosphere, kept warm for 5h, and naturally cooled to room temperature to obtain a lithium-rich manganese positive electrode base material.

[0067] Embodiment 4,

[0068] This embodiment provides a method for preparing a lithium-rich manganese-based positive electrode material, comprising the following steps:

[0069] 500g of cobalt-free lithium-rich manganese-based positive electrode material (structural formula Li 1.3 [Ni 0.3 Mn 0.4 ]O 2 ) First, mix with 0.25g (0.05%) magnesium oxide and 0.25g (0.05%) titanium oxide using a high-speed mixer. The high-speed mixer is first operated at 60r / min for 10min at room temperature for premixing, then mixed at 200r / min for 15min, and finally mixed at 800r / min. The mixed material is placed in a sagger, heated to 600℃ at a heating rate of 3℃ / min in an air atmosphere, kept warm for 5h, and naturally cooled to room temperature. The obtained positive electrode material is then mixed with 0.5g tungsten oxide using a high-speed mixer, and the above mixing and sintering steps are repeated. The lithium-rich manganese positive electrode base material is obtained, and the SEM picture is as follows Figure 2 shown.

[0070] Embodiment 5,

[0071] This embodiment provides a method for preparing a lithium-rich manganese-based positive electrode material, which differs from Embodiment 4 only in that magnesium oxide, titanium oxide and tungsten oxide are sequentially mixed with a substrate and then sintered to obtain a lithium-rich manganese-based positive electrode material in which magnesium oxide, titanium oxide and tungsten oxide are sequentially coated on the substrate.

[0072] Embodiment 6,

[0073] This embodiment provides a method for preparing a lithium-rich manganese-based positive electrode material, which differs from Example 4 only in that a mixture of magnesium oxide, titanium oxide and tungsten oxide is mixed with a substrate and then sintered to obtain a lithium-rich manganese-based positive electrode material having a coating layer containing magnesium oxide, titanium oxide and tungsten oxide on the substrate.

[0074] Embodiment 7,

[0075] This embodiment provides a method for preparing a lithium-rich manganese-based positive electrode material, which differs from Embodiment 4 only in that tungsten oxide, titanium oxide and magnesium oxide are sequentially mixed with a substrate and then sintered to obtain a lithium-rich manganese-based positive electrode material in which tungsten oxide, titanium oxide and magnesium oxide are sequentially coated on the substrate.

[0076] Embodiment 8,

[0077] This embodiment provides a method for preparing a lithium-rich manganese-based positive electrode material, which differs from Embodiment 4 only in that: titanium oxide is not coated, magnesium oxide and tungsten oxide are sequentially mixed with a substrate and then sintered to obtain a lithium-rich manganese-based positive electrode material in which magnesium oxide and tungsten oxide are sequentially coated on the substrate.

[0078] Embodiment 9,

[0079] This embodiment provides a method for preparing a lithium-rich manganese-based positive electrode material, which differs from Example 4 only in that: magnesium oxide is not coated, titanium oxide and tungsten oxide are mixed with a substrate in sequence and then sintered to obtain a lithium-rich manganese-based positive electrode material in which titanium oxide and tungsten oxide are sequentially coated on the substrate.

[0080] Embodiment 10

[0081] This embodiment provides a method for preparing a lithium-rich manganese-based positive electrode material, which differs from Embodiment 4 only in that: tungsten oxide is not coated, magnesium oxide and titanium oxide are sequentially mixed with a substrate and then sintered to obtain a lithium-rich manganese-based positive electrode material in which magnesium oxide and titanium oxide are sequentially coated on the substrate.

[0082] Embodiment 11,

[0083] This embodiment provides a method for preparing a lithium-rich manganese-based positive electrode material, which is different from Embodiment 4 only in that the coating amounts of magnesium oxide, titanium oxide, and tungsten oxide are 0.125 g, 0.125 g, and 0.25 g, respectively.

[0084] Embodiment 12

[0085] This embodiment provides a method for preparing a lithium-rich manganese-based positive electrode material, which is different from Embodiment 4 only in that the coating amounts of magnesium oxide, titanium oxide, and tungsten oxide are 0.5 g, 0.5, and 1 g, respectively.

[0086] Embodiment 13

[0087] This embodiment provides a method for preparing a lithium-rich manganese-based positive electrode material, which is different from Embodiment 4 only in that titanium oxide is replaced by an equal mass of silicon dioxide.

[0088] Comparative Example 1

[0089] The substrate in Example 3 is used as the lithium-rich manganese-based positive electrode material.

[0090] Performance test: The obtained positive electrode material was mixed with conductive carbon black and polyvinylidene fluoride (PVDF) in a certain proportion in N-methylpyrrolidone, and the uniform mixture was coated on aluminum foil. After vacuum drying, it was cut into circular pole pieces and made into CR2025 button half-cells in a glove box filled with argon gas and tested in a Xinwei battery tester. The test conditions were: at 25°C, the current density of 0.1C, 0.33C and 0.5C was charged and discharged in the voltage range of 2.8-4.55V. The results are shown in Table 1 and Figure 3 shown.

[0091]

[0092]

[0093]

[0094] According to the above table, after multi-dimensional modification of the cobalt-free lithium-rich manganese-based material, the material's charge capacity increased from 263.3mAh / g to 272.58mAh / g, and the first charge and discharge efficiency increased to 83.9%. Therefore, multi-dimensional treatment of cobalt-free lithium-rich manganese-based materials can greatly improve the material's charge capacity and its first efficiency.

[0095] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A lithium-rich manganese-based positive electrode material, characterized in that: It includes a substrate and an oxide-containing coating layer attached to at least part of the surface of the substrate, wherein the substrate is a cobalt-free lithium-rich manganese-based positive electrode material, and the coating layer includes at least one of a first oxide and a second oxide, wherein the first oxide is selected from at least one of magnesium oxide, zinc oxide and nickel oxide, and the second oxide is selected from at least one of tungsten oxide, aluminum oxide, iron oxide, titanium oxide, zirconium oxide, lanthanum pentoxide, molybdenum oxide, copper oxide, niobium oxide and silicon dioxide.

2. The lithium-rich manganese-based positive electrode material according to claim 1, characterized in that: The coating layer includes two or more oxide layers, and the atomic radius of the elements in the two or more oxide layers gradually increases from the inside to the outside; Preferably, the oxide layered layers include a first oxide layered layer composed of a first oxide and a second oxide layered layer composed of a second oxide layered layer.

3. The lithium-rich manganese-based positive electrode material according to claim 1, characterized in that: The mass ratio of the coating layer to the substrate is less than 2%.

4. The lithium-rich manganese-based positive electrode material according to claim 1, characterized in that: The matrix molecular formula is Li a [Ni x Mn 1-x ]O 2+b , where 1.1≤a≤1.5, 0 <x<0.5; And / or, the matrix is ​​secondary particles formed by agglomeration of primary particles, and the secondary particles are spherical or quasi-spherical polycrystalline in shape; And / or, the D50 of the substrate is 2um-15um.

5. A method for preparing the lithium-rich manganese-based positive electrode material according to any one of claims 1 to 4, characterized in that: include: The mixture of the matrix and the oxide is sintered to obtain the lithium-rich manganese-based positive electrode material.

6. The method for preparing a lithium-rich manganese-based positive electrode material according to claim 5, characterized in that: include: Mixing the substrate and the oxide used for the coating layer to obtain the mixture, and sintering the mixture to obtain the lithium-rich manganese-based positive electrode material; Alternatively, the two or more oxides used for the substrate and the coating layer are mixed in sequence, the mixed materials are sintered after each mixing, and then the next mixing is performed. After the last sintering, the lithium-rich manganese-based positive electrode material with more than two oxide layers is obtained.

7. The method for preparing a lithium-rich manganese-based positive electrode material according to claim 5, characterized in that: The oxide D50 is 10-300nm.

8. The method for preparing a lithium-rich manganese-based positive electrode material according to claim 5, characterized in that: The sintering temperature is 200℃-900℃, and the holding time is 60min-600min; and / or, the heating rate before sintering is 1°C / min-10°C / min; and / or, the sintering atmosphere is an oxygen-containing atmosphere; And / or, after sintering, the sintered steel is cooled to 15°C-30°C at a rate of 1°C / min-10°C / min or cooled to 15°C-30°C along with the furnace.

9. The method for preparing a lithium-rich manganese-based positive electrode material according to claim 5, characterized in that: The mixing step temperature is 20°C-150°C, the speed is 50r / min-5000r / min, and the time is 20min-60min; Preferably, the mixing step includes one-stage mixing, two-stage mixing and three-stage mixing, the one-stage mixing speed is 50r / min-5000r / min, and the time is 2min-30min; the two-stage mixing speed is 100r / min-300r / min, and the time is 2min-30min; the three-stage mixing speed is 300r / min-5000r / min, and the time is 20min-60min.

10. A lithium ion battery, characterized in that: The invention comprises the lithium-rich manganese-based positive electrode material as described in any one of claims 1 to 4.

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