Lithium-rich manganese-based positive electrode material with hierarchical pore micro-nano structure and preparation method of lithium-rich manganese-based positive electrode material

Abstract

The preparation method comprises the following steps: dissolving lithium nitrate, manganous nitrate, cobalt nitrate, nickel nitrate, an organic fuel and an organic carbon source in deionized water to obtain a uniform mixed solution, atomizing the mixed solution to form carbon-containing fog drops, and preparing the lithium-rich manganese-based positive electrode material with the hierarchical pore micro-nano structure by taking nitrogen as a protective gas and a carrier gas, so as to obtain the lithium-rich manganese-based positive electrode material with the hierarchical pore micro-nano structure. Carrying out self-propagating combustion reaction on the carbon-containing fog drops at a certain ignition temperature to obtain combustion product powder; placing the combustion product in a crucible, and calcining in an inert atmosphere to obtain calcined powder; placing the calcined powder in a crucible, and calcining in an air atmosphere to remove carbon; and fully grinding the calcined product to obtain the lithium-rich manganese-based positive electrode powder with the hierarchical pore micro-nano structure. The lithium-rich manganese-based positive electrode material with the microporous-mesoporous hierarchical pore micro-nano structure is obtained, and the cycling stability of the lithium-rich manganese-based positive electrode material can be effectively prolonged. The method is simple and convenient in process, low in energy consumption, low in price and high in capacity preservation rate, and has a relatively good industrial application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and in particular, to a multi-porous micro-nano structured lithium-rich manganese-based cathode material and a preparation method thereof. Background Art

[0002] Lithium-ion batteries have the advantages of high specific energy, no memory effect, and long cycle life, injecting fresh blood into the development of the new energy field. As the "heart" of electric vehicles, high-energy-density lithium-ion batteries can effectively overcome the problem of insufficient mileage of electric vehicles. Lithium-rich manganese-based cathode materials have a high mass specific capacity under the coupling effect of the redox of transition metal cations and oxygen anions, and have become candidates for the next generation of high-energy-density cathode materials. However, the redox of oxygen anions in lithium-rich manganese-based cathode materials will cause irreversible lattice oxygen loss (O 2- →O2), which in turn induces irreversible migration and phase transformation of transition metals during the cycling process, ultimately leading to problems such as capacity decay, discharge voltage drop, and sluggish electrochemical reactions of lithium-rich manganese-based cathode materials.

[0003] Based on this, the applicant starts from the perspective of the structure / interface design of lithium-rich manganese-based cathode materials, and aims at the key scientific problems such as lattice oxygen loss, transition metal migration, irreversible phase transformation, and electrode / electrolyte interface side reactions of lithium-rich manganese-based cathode materials during the cycling process. Through bulk structure design and electrode / electrolyte interface optimization, the redox behavior of lattice oxygen, the structure transformation characteristics, and the evolution law of the electrode / electrolyte interface of lithium-rich manganese-based cathode materials during charge / discharge are regulated to alleviate problems such as capacity decay and voltage drop of lithium-rich manganese-based cathode materials during the cycling process.

[0004] The comprehensive performance of lithium-rich manganese-based cathode materials is closely related to their morphology and structure. Compared with introducing ion modification and surface coating, morphology control can ensure the purity of the material, and at the same time, the material synthesis has the properties of simplicity and convenience. In actual production, to improve the comprehensive performance of lithium-rich manganese-based cathode materials, lithium-rich manganese-based cathode materials are usually synthesized into solid micron-spherical morphology or nano-sized irregular geometric morphologies. These two types of materials can greatly shorten the diffusion paths of ions and electrons to ensure full contact between the material and the electrolyte interface, achieving the purpose of improving electrochemical performance.

[0005] The droplet combustion method has natural advantages in the field of preparing nano-sized metal oxide spherical powders and has been widely used. Carbon materials have excellent chemical stability, structural strength, barrier and other properties and have been widely used in aspects such as refining crystal grains. It is envisioned that if the synergistic advantages of the simple synthesis characteristics of droplet combustion and the crystal grain refinement characteristics of carbon can be utilized to construct a multi-porous micro-nano structured lithium-rich manganese-based cathode material, it is expected to meet the requirements of high-performance lithium-ion battery cathode materials. Summary of the Invention

[0006] The present invention aims to provide a multi-level porous micro-nanostructured lithium-manganese-rich positive electrode material and a preparation method thereof, so as to solve the technical problem that the comprehensive performance of the existing lithium-manganese-rich positive electrode materials is not ideal.

[0007] To achieve the above object, the present invention provides a method for preparing a multi-level porous micro-nanostructure lithium-rich manganese-based positive electrode material, the specific steps of which are as follows: (1) First, lithium nitrate, manganese nitrate, cobalt nitrate, nickel nitrate, organic fuel, and organic carbon source are dissolved in deionized water to obtain a uniform mixed solution, and then the mixed solution is atomized to form carbon-containing droplets, and nitrogen is used as a protective gas and a carrier gas to cause the carbon-containing droplets to undergo a self-propagating combustion reaction at a certain ignition temperature to obtain a combustion product powder; (2) placing the combustion product obtained in step (1) in a crucible and calcining in an inert atmosphere to obtain a calcined powder; (3) placing the calcined powder obtained in step (2) in a crucible and calcining in an air atmosphere to remove carbon; (4) fully grinding the calcined product obtained in step (3) to obtain a multi-level porous micro-nanostructured lithium-rich manganese-based positive electrode powder; Among them, the molar ratio of lithium nitrate, manganese nitrate, cobalt nitrate and nickel nitrate is 1.2:0.54:0.13:0.13; the ratio of the total molar amount of lithium nitrate, manganese nitrate, cobalt nitrate and nickel nitrate to the molar amount of organic fuel and organic carbon source is 1:0.5-3:0.5-6.

[0008] Preferably, in step (1), the organic fuel is selected from at least one of urea, glycine and alanine; and the organic carbon source is selected from at least one of sucrose, glucose, starch and citric acid.

[0009] Preferably, in step (1), the flow rate of nitrogen is 0.5 to 3 L / min.

[0010] Preferably, in step (1), the ignition temperature of the carbon-containing droplets is 600-1000°C.

[0011] Preferably, in step (2), the inert atmosphere is selected from nitrogen or argon.

[0012] Preferably, in step (2), the calcination process conditions are: calcination at 500-1000° C. for 0.5-5 hours.

[0013] Preferably, in step (3), the calcination process conditions are: calcination at 600-800° C. for 1-6 hours.

[0014] The present invention also provides a multi-level porous micro-nanostructure lithium-rich manganese-based positive electrode material, which is obtained by the above-mentioned preparation method.

[0015] The principle of the present invention is: In the present invention, an organic carbon source (such as glucose) is added to a mixed solution of an organic fuel (such as urea) and an oxidant (such as lithium nitrate, a nitrate). After achieving a uniform mixing of each raw material at the molecular level, the mixture is atomized to form tiny carbon-containing droplets. At a certain temperature, a self-propagating combustion reaction of the carbon-containing droplets is initiated, that is, an oxidation-reduction exothermic reaction occurs between the nitrate and the organic fuel. The organic carbon source absorbs heat and undergoes pyrolysis to form carbon particles. The released heat instantaneously converts the nitrate into corresponding metal oxide particles. At the same time, these metal oxide particles are mutually solid-solved into a metal composite oxide (i.e., a lithium-rich manganese-based cathode material), and are uniformly "embedded" in the carbon hollow sphere matrix formed by the pyrolysis and carbonization of glucose. The fine carbon particles play a very good role in dispersing and isolating the metal composite oxide particles, which is conducive to obtaining uniformly fine metal composite oxide nanoparticles. In addition, the product gases such as CO2, N2, and H2O released during combustion produce an impact effect, causing a large number of micropores to form between the metal composite oxide nanoparticles. Then, the carbon-based hollow sphere powder is calcined in an inert atmosphere, enabling these metal composite oxide nanoparticles to undergo sufficient solid solution and crystallization. The carbon particles continue to play a role in dispersing and isolating, preventing these metal composite oxide nanoparticles from sintering and aggregating. Then, the carbon-based hollow sphere powder is calcined in an air atmosphere, and the excess carbon particles are removed by the combustion reaction of carbon, retaining the hollow spheres formed by the solid-solved metal composite oxides. At the same time, mesopores are formed in the hollow spheres, obtaining micron-sized hollow spheres composed of solid-solved metal composite oxide nanoparticles, and preparing a lithium-rich manganese-based cathode material with a hierarchical pore micro-nano structure integrating micropores and mesopores.

[0016] The present invention has the following beneficial effects: All kinds of water-soluble raw materials in the initial solution are uniformly mixed at the atomic level. During the combustion reaction process, LiMnO2, LiNiO2, and LiCoO2 and the carbon hollow spheres are all formed in-situ, and the three metal composite oxides are uniformly embedded in the carbon hollow sphere matrix. In addition, due to the impact effect of a large amount of generated gas, a large number of micropores are formed between the metal composite oxides. The fine carbon particles can also play a very good role in dispersing and isolating, and uniformly dispersed nano-scale metal oxide particles can be obtained. Subsequently, calcination in an inert atmosphere enables these metal oxides to be in-situ solid-solved and converted into a lithium-rich manganese-based cathode powder material. The carbon particles continue to prevent the aggregation and growth of the solid-solved metal oxide particles. Finally, after calcination in an air atmosphere to remove carbon, a large number of uniform mesopores can also be formed in the micron-sized hollow spheres. The above-mentioned micropores, mesopores, and the morphology and uniformity of the micro-nano combined structure can be controlled by adjusting the raw material ratio and combustion parameters. Therefore, this method can solve the problems of precise regulation and preparation of the micro-mesoporous structure, obtain a lithium-rich manganese-based cathode material with a hierarchical pore micro-nano structure integrating micropores and mesopores, and can effectively extend the cycle stability of the lithium-rich manganese-based cathode material. The process of the present invention is simple, has low energy consumption, is inexpensive, has a high capacity retention rate, and has good industrial application prospects.

[0017] In addition to the purposes, features, and advantages described above, the present invention has other purposes, features, and advantages. The present invention will be further described in detail below with reference to the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings: Figure 1 is the SEM image of the hierarchical porous micro-nano structured lithium-rich manganese-based cathode material.

[0019] Figure 2 is the XRD of the hierarchical porous micro-nano structured lithium-rich manganese-based cathode material.

[0020] Figure 3 is the rate performance graph of the hierarchical porous micro-nano structured lithium-rich manganese-based cathode material.

[0021] Figure 4 is the 1C rate 100-cycle performance graph of the hierarchical porous micro-nano structured lithium-rich manganese-based cathode material. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The following describes in detail the embodiments of the present invention with reference to the drawings. However, the present invention can be implemented in many different ways defined and covered by the claims.

[0023] Embodiment 1 A hierarchical porous micro-nano structured lithium-rich manganese-based cathode material and its preparation method in this embodiment specifically include the following steps: (1) Dissolve lithium nitrate, manganese nitrate, cobalt nitrate, nickel nitrate, urea, and glucose in deionized water to obtain a mixed solution, where the molar ratio of lithium, manganese, cobalt, and nickel in the nitrates is 1.2:0.54:0.13:0.13, the molar ratio of the sum of lithium, manganese, cobalt, and nickel in the nitrates to glucose is 1:0.5, and the molar ratio of the sum of lithium, manganese, cobalt, and nickel in the nitrates to urea is 1:2. Atomize the solution to form carbon-containing droplets, and use nitrogen as a protective gas to cause the droplets to undergo self-propagating combustion at 700°C; (2) After calcining the powder obtained in step (1) in a nitrogen atmosphere at 700°C for 5 h, place it in a crucible and then calcine it in an air atmosphere at 650°C for 4 h; (3) Grind the powder obtained in step (2) thoroughly to obtain the hierarchical porous micro-nano structured lithium-rich manganese-based cathode material.

[0024] The SEM of the cathode material is shown in Figure 1 , and the XRD is shown in Figure 2 .

[0025] Example 2 The method for preparing a multi-level porous micro-nanostructure lithium-rich manganese-based positive electrode material described in this embodiment specifically includes the following steps: (1) dissolving lithium nitrate, manganese nitrate, cobalt nitrate, nickel nitrate, urea and glucose in deionized water to obtain a mixed solution, wherein the molar ratio of lithium, manganese, cobalt and nickel in the nitrate is 1.2:0.54:0.13:0.13, the molar ratio of the sum of lithium, manganese, cobalt and nickel in the nitrate to glucose is 1:3, and the molar ratio of the sum of lithium, manganese, cobalt and nickel in the nitrate to urea is 1:3, using nitrogen as a protective gas, burning carbon-containing droplets at 900° C. to obtain a combustion product powder; (2) the powder obtained in step (1) was calcined at 900°C in a nitrogen atmosphere for 1 h, placed in a crucible, and then calcined at 650°C in an air atmosphere for 1 h; (3) Grind the powder obtained in step (2) to obtain a multi-level porous micro-nanostructured lithium-manganese-rich positive electrode material.

[0026] Example 3 The method for preparing a multi-level porous micro-nanostructure lithium-rich manganese-based positive electrode material described in this embodiment specifically includes the following steps: (1) Lithium nitrate, manganese nitrate, cobalt nitrate, nickel nitrate, alanine and starch are dissolved in deionized water to obtain a mixed solution, wherein the molar ratio of lithium, manganese, cobalt and nickel in the nitrate is 1.2:0.54:0.13:0.13, the molar ratio of the sum of lithium, manganese, cobalt and nickel in the nitrate to starch is 1:6, and the molar ratio of the sum of lithium, manganese, cobalt and nickel in the nitrate to alanine is 1:3, and nitrogen is used as a protective gas to burn carbon-containing droplets at 1000° C. to obtain a combustion product powder; (2) The powder obtained in step (1) was calcined at 700°C in a nitrogen atmosphere for 5 h, placed in a crucible, and then calcined at 650°C in an air atmosphere for 0.5 h; (3) Grind the powder obtained in step (2) to obtain a multi-level porous micro-nanostructured lithium-manganese-rich positive electrode material.

[0027] Example 4 The method for preparing a multi-level porous micro-nanostructure lithium-rich manganese-based positive electrode material described in this embodiment specifically includes the following steps: (1) Lithium nitrate, manganese nitrate, cobalt nitrate, nickel nitrate, urea and sucrose are dissolved in deionized water to obtain a mixed solution, wherein the molar ratio of lithium, manganese, cobalt and nickel in the nitrate is 1.2:0.54:0.13:0.13, the molar ratio of the sum of lithium, manganese, cobalt and nickel in the nitrate to sucrose is 1:3, and the molar ratio of the sum of lithium, manganese, cobalt and nickel in the nitrate to urea is 1:6, and nitrogen is used as a protective gas, and carbon-containing droplets are burned at 900° C. to obtain a combustion product powder; (2) Calcinate the powder obtained in step (1) at 800 °C in a nitrogen atmosphere for 4 h, place it in a crucible, and then calcinate it at 650 °C in an air atmosphere for 4 h; (3) Grind the powder obtained in step (2) thoroughly to obtain a multi-porous micro-nano structured lithium-rich manganese-based cathode material.

[0028] Example 5 The preparation method of a multi-porous micro-nano structured lithium-rich manganese-based cathode material described in this example specifically includes the following steps: (1) Dissolve lithium nitrate, manganese nitrate, cobalt nitrate, nickel nitrate, glycine, and glucose in deionized water to obtain a mixed solution, where the molar ratio of lithium, manganese, cobalt, and nickel in the nitrates is 1.2:0.54:0.13:0.13, the molar ratio of the sum of lithium, manganese, cobalt, and nickel in the nitrates to glucose is 1:3, and the molar ratio of the sum of lithium, manganese, cobalt, and nickel in the nitrates to glycine is 1:6. Use nitrogen as a protective gas and conduct carbon-containing droplet combustion at 900 °C to obtain a combustion product powder; (2) Calcinate the powder obtained in step (1) at 700 °C in a nitrogen atmosphere for 1 h, place it in a crucible, and then calcinate it at 650 °C in an air atmosphere for 6 h; (3) Grind the powder obtained in step (2) thoroughly to obtain a multi-porous micro-nano structured lithium-rich manganese-based cathode material.

[0029] Comparative Example 1 A lithium-rich manganese-based cathode material and its preparation method specifically include the following steps: (1) Dissolve lithium nitrate, manganese nitrate, cobalt nitrate, nickel nitrate, urea, and glucose in deionized water to obtain a mixed solution, where the molar ratio of lithium, manganese, cobalt, and nickel in the nitrates is 1.2:0.5:0.15:0.15, the molar ratio of the sum of lithium, manganese, cobalt, and nickel in the nitrates to glucose is 1:3, and the molar ratio of the sum of lithium, manganese, cobalt, and nickel in the nitrates to urea is 1:2. Atomize the solution to form carbon-containing droplets, use nitrogen as a protective gas, and make the droplets undergo self-propagating combustion at 700 °C; (2) Calcinate the powder obtained in step (1) at 700 °C in a nitrogen atmosphere for 5 h, place it in a crucible, and then calcinate it at 650 °C in an air atmosphere for 0.5 h; (3) Grind the powder obtained in step (2) thoroughly to obtain a lithium-rich manganese-based cathode material.

[0030] Comparative Example 2 A lithium-rich manganese-based cathode material and its preparation method specifically include the following steps: (1) Dissolve lithium nitrate, manganese nitrate, cobalt nitrate, nickel nitrate, glycine, and glucose in deionized water to obtain a mixed solution. The molar ratio of lithium, manganese, cobalt, and nickel in the nitrate is 1.2:0.54:0.13:0.13. No organic carbon source is added to the mixed solution. The molar ratio of the sum of lithium, manganese, cobalt, and nickel in the nitrate to urea is 1:2. Atomize the solution to form carbon-containing droplets, and use nitrogen as the protective gas to cause the droplets to undergo self-propagating combustion at 700 °C. (2) After calcining the powder obtained in step (1) at 700 °C in a nitrogen atmosphere for 5 h, place it in a crucible and then calcine it at 650 °C in an air atmosphere for 0.5 h. (3) Grind the powder obtained in step (2) thoroughly to obtain a lithium-rich manganese-based cathode material.

[0031] Comparative Example 3 A lithium-rich manganese-based cathode material and its preparation method specifically include the following steps: (1) Dissolve lithium nitrate, manganese nitrate, cobalt nitrate, nickel nitrate, urea, and glucose in deionized water to obtain a mixed solution. The molar ratio of lithium, manganese, cobalt, and nickel in the nitrate is 1.2:0.54:0.13:0.13. The molar ratio of the sum of lithium, manganese, cobalt, and nickel in the nitrate to glucose is 1:0.5. The molar ratio of the sum of lithium, manganese, cobalt, and nickel in the nitrate to urea is 1:5. Atomize the solution to form carbon-containing droplets, and use nitrogen as the protective gas to cause the droplets to undergo self-propagating combustion at 700 °C. (2) After calcining the powder obtained in step (1) at 700 °C in a nitrogen atmosphere for 5 h, place it in a crucible and then calcine it at 650 °C in an air atmosphere for 4 h. (3) Grind the powder obtained in step (2) thoroughly to obtain a lithium-rich manganese-based cathode material.

[0032] Performance Evaluation Related tests: Using PVDF (polyvinylidene fluoride) as the binder and NMP (N-methylpyrrolidone) as the solvent, grind and mix the multi-porous micro-nano structured lithium-rich manganese-based cathode material, conductive carbon black, and PVDF evenly at a mass ratio of 8:1:1, pour it into 1.5 ml of NMP and stir for 12 h to obtain the cathode slurry. Coat the slurry evenly on the aluminum foil, place it in a vacuum oven at 100 °C and dry for 12 h, and then cut it into circular pieces with a diameter of 14 mm. Using the circular pieces prepared above as the cathode, a metal lithium sheet as the anode, and a polypropylene microporous membrane as the separator, and using a mixed solution prepared by dissolving 1 mol / L of LiPF6 in EC (ethylene carbonate) / DMC (dimethyl carbonate) / EMC (ethyl methyl carbonate) at a volume ratio of 1:1:1 as the electrolyte, assemble a CR2025 stainless steel button battery in a glove box filled with argon and with a water content lower than 0.1 ppm; after standing for 4 h, test its charge and discharge performance at room temperature.

[0033] The batteries provided by Example 1 and Example 2 prepared under the above conditions were subjected to performance tests. The test instrument was a Neware battery test system, and the test conditions were as follows: rate performance tests and cycle performance tests were carried out at voltages of 2.4 - 5V. Among them, for the rate performance, test conditions of 0.2C, 0.5C, 1C, 2C, 5C, 10C, and 0.2C were selected; for the cycle performance, a 0.1C rate was used to activate the battery, and then charge and discharge tests were carried out at a 1C rate cycle to obtain the capacity retention rate after 100 cycles. The test results are shown in Table 1. Figure 3 It is the rate performance graph of the hierarchical pore micro-nano structured lithium-rich manganese-based cathode materials of Example 1 and Example 2. Figure 4 It is the 1C rate 100-cycle performance graph of the hierarchical pore micro-nano structured lithium-rich manganese-based cathode materials of Example 1 and Example 2.

[0034] Table 1 From Figure 3 、 4 and Table 1, it can be obtained that: (1) For the lithium-ion batteries assembled with the hierarchical pore micro-nano structured lithium-rich manganese-based cathode materials provided in Examples 1 - 5, relatively balanced advantages are maintained in terms of the initial specific capacity, initial Coulomb efficiency, and capacity retention rate, showing high cycle stability; (2) By comparing Example 1 with Examples 2 and 3, it can be seen that the molar ratio of the sum of lithium, manganese, cobalt, and nickel in the nitrate to the organic carbon source in step (1) of the present invention will affect the performance of the lithium-ion battery; when the molar concentration ratio is 3, the lithium-ion battery has good cycle stability. This is because an appropriate amount of organic carbon source can construct uniform mesopores, and the obtained hierarchical pore micro-nano structured lithium-rich manganese-based cathode material can fully contact the electrolyte, affecting the electrochemical performance of the subsequent lithium battery. If too much organic carbon source is added, although the primary particles can be further refined, the too fine primary particles will exacerbate the side reactions during the charge and discharge process, which is not conducive to the cycle stability of the subsequent cathode material; (3) By comparing Example 2 with Example 4, it can be seen that the type of organic carbon source in step (1) of the present invention will affect the performance of the lithium-ion battery; when the organic carbon source is glucose, it can be seen from SEM that the primary particles of the prepared lithium-rich manganese-based cathode material are clearly demarcated, and at the same time, the voids on the spherical particles can be clearly seen, which is beneficial to the improvement of the cycle stability of the lithium-ion battery material; (4) It can be seen from the comparison between Example 2 and Example 5 that the type of organic fuel in step (1) of the present invention will affect the performance of the lithium-ion battery; when the type of organic fuel in the step is urea, the lithium-ion battery has better cycle stability, because more gases will be generated during the decomposition of urea in the droplet combustion reaction process, and the carbon / lithium-rich manganese-based composite oxide spherical particles formed by the gas impact can obtain a multi-stage pore micro-nano structure lithium-rich manganese-based cathode material with a suitable combination of micropores and mesopores; (5) It can be seen from the comparison between Example 2 and Comparative Examples 1 to 3 that the preparation method of the multi-stage pore micro-nano structure lithium-rich manganese-based cathode material provided by the present invention can conveniently and quickly construct a multi-stage pore micro-nano spherical structure, effectively increasing the contact area between the lithium-rich manganese-based cathode material and the electrolyte, and increasing the cycle stability of the lithium-ion battery; the preparation method of the multi-stage pore micro-nano structure lithium-rich manganese-based cathode material provided by the present invention has a simple process and low requirements for equipment, which is conducive to large-scale popularization and use.

[0035] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. 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 method for preparing a multi-level porous micro-nanostructure lithium-rich manganese-based positive electrode material, characterized in that: The specific steps are as follows: (1) First, lithium nitrate, manganese nitrate, cobalt nitrate, nickel nitrate, organic fuel, and organic carbon source are dissolved in deionized water to obtain a uniform mixed solution, and then the mixed solution is atomized to form carbon-containing droplets, and nitrogen is used as a protective gas and a carrier gas to cause the carbon-containing droplets to undergo a self-propagating combustion reaction at a certain ignition temperature to obtain a combustion product powder; (2) placing the combustion product obtained in step (1) in a crucible and calcining in an inert atmosphere to obtain a calcined powder; (3) placing the calcined powder obtained in step (2) in a crucible and calcining in an air atmosphere to remove carbon; (4) fully grinding the calcined product obtained in step (3) to obtain a multi-level porous micro-nanostructured lithium-rich manganese-based positive electrode powder; Among them, the molar ratio of lithium nitrate, manganese nitrate, cobalt nitrate and nickel nitrate is 1.2:0.54:0.13:0.13; the ratio of the total molar amount of lithium nitrate, manganese nitrate, cobalt nitrate and nickel nitrate to the molar amount of organic fuel and organic carbon source is 1:0.5-3:0.5-6.

2. The preparation method according to claim 1, characterized in that: In step (1), the organic fuel is selected from at least one of urea, glycine, and alanine; and the organic carbon source is selected from at least one of sucrose, glucose, starch, and citric acid.

3. The preparation method according to claim 1, characterized in that: In step (1), the flow rate of nitrogen is 0.5 to 3 L / min.

4. The preparation method according to claim 1, characterized in that: In step (1), the ignition temperature of the carbon-containing droplets is 600 to 1000°C.

5. The preparation method according to claim 1, characterized in that: In step (2), the inert atmosphere is selected from nitrogen or argon.

6. The preparation method according to claim 1, characterized in that: In step (2), the calcination process conditions are: calcination at 500-1000° C. for 0.5-5 hours.

7. The preparation method according to claim 1, characterized in that: In step (3), the calcination process conditions are: calcination at 600-800° C. for 1-6 hours.

8. A multi-level porous micro-nanostructured lithium-rich manganese-based positive electrode material, characterized in that: The invention is obtained by the preparation method according to any one of claims 1 to 7.

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