Fluorine-doped carbon coated-spinel heterostructure synergistically modified lithium-rich manganese-based positive electrode material and preparation method thereof

Abstract

The invention discloses a fluorine-doped carbon coated-spinel heterostructure synergistically modified lithium-rich manganese-based positive electrode material and a preparation method thereof, and belongs to the technical field of lithium ion battery positive electrode materials. The preparation method comprises the following steps: (1) preparing a lithium-rich manganese-based positive electrode base material; (2) using the lithium-rich manganese-based material as a matrix, providing a fluorine source and a carbon source through a single or composite medium, and sequentially forming an oxygen vacancy defect layer and a fluorine-doped carbon coating layer on the surface; and (3) uniformly stirring the fluorine source / carbon source-containing compound and the lithium-rich manganese-based positive electrode material in a high-temperature coating machine, and heating to a temperature above the melting point temperature of the fluorine source / carbon source for high-temperature melting. The invention proves that the modification effect is optimal when polyvinylidene fluoride is used as a fluorine / carbon co-doping source, the problems of poor cycling stability, poor rate capability, serious irreversible oxygen release and low electronic conductivity of the existing lithium-rich manganese-based material are solved, and the first-week coulombic efficiency, cycling stability and rate capability of the material can be remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a lithium-rich manganese-based cathode material with fluorine-doped carbon coating and spinel heterostructure synergistic modification and its preparation method. Background Technology

[0002] Developing high-energy-density lithium-ion battery technology is key to improving the driving range of electric vehicles and electric aircraft. Lithium-rich manganese-based cathode materials, which provide additional capacity through anion (oxygen) redox reactions, possess ultra-high specific capacity (≥250 mAh / g), potentially increasing battery energy density by over 30%, and are considered an ideal choice for next-generation lithium-ion battery cathode materials. However, the practical application of lithium-rich manganese-based materials faces several bottlenecks: First, the anion redox reaction easily leads to irreversible release of lattice oxygen, causing material structure collapse, irreversible capacity loss, and low initial coulombic efficiency; second, the material has poor electronic conductivity and slow lithium-ion diffusion kinetics, resulting in poor rate performance; third, the migration of transition metal ions and exacerbated interfacial side reactions during cycling significantly reduce cycle stability.

[0003] To solve the above problems, researchers have developed a variety of modification strategies, but their single modification effects have obvious limitations: (1) Single fluorine doping modification: Because fluorine atoms have high electronegativity and ionic radii close to oxygen atoms, they can optimize the crystal structure by replacing lattice oxygen and suppress irreversible oxygen release. However, fluorine itself does not have conductive properties and cannot solve the problem of poor electronic conductivity of materials, resulting in limited improvement in rate performance; (2) Single carbon coating modification: Carbon materials (such as carbon black and graphene) have high conductivity and can build a conductive network on the surface of the material to improve electron transport efficiency. At the same time, it can block the direct contact between the electrolyte and the material and reduce the interface side reaction. However, the carbon coating layer cannot regulate the internal lattice structure of the material and has a weak inhibitory effect on irreversible oxygen release and transition metal ion migration. The structure will still collapse during the cycle; (3) Single phosphorus doping modification: Phosphorus can optimize the lithium ion diffusion channel by adjusting the lattice spacing. However, single phosphorus doping has a limited effect on improving electronic conductivity and cannot effectively inhibit oxygen release. The first-cycle coulombic efficiency and cycle stability of the modified material are not significantly improved; (4) Composite modification technology: Step-by-step modification process (such as fluorine doping followed by carbon coating) is often used. Not only is the process complicated and the production cost high, but the bonding between each modified layer is not tight and it is easy to fall off during the cycle. It is difficult to achieve the synergistic effect of each modification mechanism and large-scale production is difficult.

[0004] Therefore, developing a simple, low-cost synergistic modification technology that can simultaneously integrate fluorine, phosphorus, and carbon to solve the three core problems of conductivity, structural stability, and oxygen release in lithium-rich manganese-based materials is of great significance for their commercial application. Summary of the Invention

[0005] One of the objectives of this invention is to provide a lithium-rich manganese-based cathode material with fluorine-doped carbon coating and spinel heterostructure synergistic modification, which solves the problems of poor cycle stability, poor rate performance, serious irreversible oxygen release, and low electronic conductivity of lithium-rich manganese-based cathode materials.

[0006] The second objective of this invention is to provide a method for preparing the above-mentioned lithium-rich manganese-based cathode material, which is simple in process and low in cost.

[0007] The third objective of this invention is to provide a lithium-ion battery comprising the above-mentioned positive electrode material.

[0008] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: In a first aspect, the present invention provides a lithium-rich manganese-based cathode material with fluorine-doped carbon coating-spinel heterostructure synergistic modification, comprising a lithium-rich manganese-based material matrix (core) and a coating layer; The lithium-rich manganese-based material matrix includes a layered lithium-rich bulk phase and an outer layer with an oxygen vacancy defect layer having a spinel heterostructure. The coating layer is a fluorine-doped carbon coating layer or a fluorine-phosphorus co-doped carbon coating layer.

[0009] The general structural formula of the lithium-rich manganese-based material matrix is ​​xLi2MnO3·(1-x)LiMO2, wherein 0.1≤x≤0.9, and M is selected from one or more of Ni, Co, Mn, Cr, Al, Mg, Mo, Ru, Nb, Zr and Sn, and includes at least Ni, Co and Mn.

[0010] Preferably, the thickness of the coating layer is 1~100 nm.

[0011] Preferably, the spinel heterostructure is of the LiMn2O4 type.

[0012] The fluorine-doped carbon coating layer can be incorporating phosphorus to form a fluorine-phosphorus co-doped carbon coating layer as needed. Phosphorus, in synergy with fluorine, regulates the crystal structure, further optimizing lithium-ion diffusion kinetics and suppressing irreversible oxygen release.

[0013] like Figure 1 As shown, the inner lithium-rich phase is responsible for providing high capacity; the middle spinel layer provides a three-dimensional lithium-ion diffusion channel and accommodates oxidized lattice oxygen, improving rate performance and suppressing gas generation; the outer fluorine-doped carbon layer enhances the electronic conductivity of the material and suppresses undesirable interfacial reactions, thereby improving the structural stability of the material.

[0014] Secondly, this invention provides a method for preparing a lithium-rich manganese-based cathode material with fluorine-doped carbon coating and spinel heterostructure synergistic modification, comprising the following steps: Using lithium-rich manganese-based materials as the matrix, a fluorine source, a carbon source, and an optional phosphorus source are provided through a single medium or a composite medium. After being mixed evenly, the mixture is heated to above the melting point temperature of the fluorine / carbon compound. Under the combined action of mechanical mixing and high-temperature melting, an oxygen vacancy defect layer and a coating layer are sequentially formed on the surface of the layered lithium-rich bulk phase, resulting in a lithium-rich manganese-based cathode material with fluorine-doped carbon coating and spinel heterostructure synergistic modification.

[0015] Preferably, the fluorine source and the carbon source are a combination of a single fluorine source and a single carbon source, or are from a carbon-fluorine co-doped source; The single carbon source is selected from at least one of glucose, sucrose, and carbon black; the single fluorine source is selected from at least one of ammonium fluoride, lithium fluoride, and sodium fluoride. The carbon-fluorine co-doped source is selected from any one or more of polyvinylidene fluoride, polytetrafluoroethylene, and perfluoroethylene propylene. Preferably, the phosphorus source is selected from at least one of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, sodium hypophosphite, and lithium phosphate.

[0016] The phosphorus source must be selected to match the melting point of the fluorine and carbon sources to ensure synchronous adhesion during high-temperature melting and achieve uniform doping of phosphorus.

[0017] Preferably, the total mass of the fluorine source, carbon source, and optional phosphorus source is 0.1%-10.0% of the mass of the lithium-rich manganese-based material.

[0018] Mechanical mixing and high-temperature melting are achieved using a high-temperature coating machine. This equipment can perform heating treatment simultaneously with mechanical stirring, achieving one-step coating and phase transformation through the synergistic effect of mechanical stirring and high-temperature melting. Specifically, the process includes the following steps: The selected fluorine / carbon compound and lithium-rich manganese-based material are premixed uniformly in the high-temperature coating machine at a speed of 500-1000 rpm, and then stirred at a speed of 1500-1800 rpm. Under an air atmosphere, the temperature is increased to above the melting point of the fluorine / carbon source at a heating rate of 1-10℃ / min. Stirring is maintained and the temperature is held for 2-8 hours before stirring is stopped, resulting in a lithium-rich manganese-based cathode material with fluorine-doped carbon coating and spinel heterostructure synergistic modification.

[0019] Preferably, the procedure specifically includes the following steps: (1) Preparation of lithium-rich manganese-based precursor: According to the general formula of lithium-rich manganese-based materials, lithium-rich manganese-based precursors are prepared by precipitation reaction using the corresponding soluble metal M salt, precipitant and water at a certain system temperature. (2) Preparation of lithium-rich manganese-based materials: The lithium-rich manganese-based precursor obtained in step (1) is uniformly mixed with lithium salt, and the lithium-rich manganese-based materials are obtained by pre-calcination and high-temperature sintering. (3) After mixing the lithium-rich manganese-based material, fluorine source, carbon source and optional phosphorus source evenly, heat it to a temperature above the melting point of fluorine / carbon compound (or fluorine / phosphorus / carbon compound). Under the action of mechanical mixing and high temperature melting, an oxygen vacancy defect layer and a coating layer are formed sequentially on the surface of the lithium-rich manganese-based material matrix to obtain a lithium-rich manganese-based cathode material with fluorine doping carbon coating-spinel heterostructure synergistic modification.

[0020] Preferably, in step (1), the soluble metal M salt is one or more of sulfates, acetates, and nitrates containing M.

[0021] Preferably, in step (1), the precipitant is one or more of sodium carbonate, potassium carbonate, sodium hydroxide, or potassium hydroxide.

[0022] Preferably, in step (2), the lithium salt is one or more of lithium hydroxide, lithium carbonate, lithium nitrate, lithium acetate, and lithium oxalate.

[0023] Preferably, in step (2), the pre-firing process is as follows: the temperature is increased to 400-700℃ at a heating rate of 1-10℃ / min and held for 3-12 hours; the high-temperature sintering process is as follows: the temperature is increased to 700-1000℃ at a heating rate of 1-10℃ / min and held for 10-20 hours.

[0024] Thirdly, the present invention provides a lithium-ion battery comprising a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode comprises the aforementioned lithium-rich manganese-based positive electrode material.

[0025] Beneficial effects: (1) The polyvinylidene fluoride preferred in this invention is a commercially available conventional material that is non-toxic and environmentally friendly, and does not require additional fluorine source, carbon source or catalyst.

[0026] (2) This invention utilizes a high-temperature coating machine to achieve liquid-phase coating by heating and melting while mechanically stirring. The entire process requires no complex equipment and is suitable for large-scale industrial production.

[0027] (3) Fluorine-doped carbon coating enhances electronic conductivity and blocks electrolyte erosion, thereby improving the rate performance and cycle stability of lithium-ion batteries. The spinel heterostructure provides 3D lithium-ion diffusion channels, enhancing the lithium-ion transport rate. Oxygen vacancies inhibit irreversible oxygen release. The synergistic effect of these three factors significantly improves the overall performance of the material.

[0028] The present invention has been described in detail above; however, the above embodiments are merely illustrative in nature and are not intended to limit the invention. Furthermore, this document is not limited to the foregoing prior art or the invention itself, or to any theory described in the following embodiments. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of the lithium-rich manganese-based cathode material of the present invention.

[0030] Figure 2 This is the SEM spectrum of Example 3 at 20,000x magnification.

[0031] Figure 3 These are the EPR spectra of Example 3 and Comparative Example 1. Detailed Implementation

[0032] The present invention will be further described below with reference to the embodiments. It should be noted that the following embodiments are provided for illustrative purposes only and do not constitute a limitation on the scope of protection of the present invention.

[0033] Unless otherwise specified, the raw materials, reagents, and methods used in the embodiments are all conventional raw materials, reagents, and methods in the art.

[0034] The melting point data of several carbon / fluorine / phosphorus compounds in the examples are shown in Table 1.

[0035] Table 1 Melting point temperatures of several carbon / fluorine-containing compounds

[0036] Example 1: (1) Take 1.0g sucrose (molecular weight 342), 1.0g ammonium fluoride, and 100.0g lithium-rich manganese-based matrix material (the lithium-rich manganese-based matrix material is prepared by conventional co-precipitation combined with high-temperature lithiation, see Comparative Example 1) and add them to the conical mixing tank of the high-temperature coating machine. Start the equipment and stir and premix evenly at a speed of 500rpm.

[0037] (2) Keep the equipment running, increase the stirring speed to 1500 rpm, and at the same time raise the temperature of the barrel to 300 ℃ through the barrel wall heating plate at a heating rate of 5 ℃ / min, and keep it warm for 5 hours.

[0038] (3) Stop heating, reduce the stirring speed to 500 rpm, and continue stirring until the material cools to room temperature to obtain the fluorine-doped carbon-coated spinel heterostructure synergistic modification lithium-rich manganese-based cathode material.

[0039] Example 2: (1) Take 1.0g glucose, 1.0g ammonium fluoride (the purity of the raw materials is greater than 99%) and 100.0g lithium-rich manganese-based matrix material (the lithium-rich manganese-based matrix material is prepared by conventional co-precipitation combined with high-temperature lithiation, see Comparative Example 1) and add them to the conical mixing tank of the high-temperature coating machine. Start the equipment and stir and premix evenly at a speed of 500rpm.

[0040] (2) Keep the equipment running, increase the stirring speed to 1500 rpm, and at the same time raise the temperature of the barrel to 300 ℃ through the barrel wall heating plate at a heating rate of 5 ℃ / min, and keep it warm for 5 hours.

[0041] (3) Stop heating, reduce the stirring speed to 500 rpm, and continue stirring until the material cools to room temperature to obtain the fluorine-doped carbon-coated spinel heterostructure synergistic modification lithium-rich manganese-based cathode material.

[0042] Example 3: (1) Take 2.0g of polyvinylidene fluoride (number average molecular weight 800,000) and 100.0g of lithium-rich manganese matrix material (the lithium-rich manganese matrix material is prepared by conventional co-precipitation combined with high-temperature lithiation, see Comparative Example 1) and add them to the conical mixing tank of the high-temperature coating machine. Start the equipment and stir and premix evenly at a speed of 500rpm.

[0043] (2) Keep the equipment running, increase the stirring speed to 1500 rpm, and at the same time raise the temperature of the barrel to 300 ℃ through the barrel wall heating plate at a heating rate of 5 ℃ / min, and keep it warm for 5 hours.

[0044] (3) Stop heating, reduce the stirring speed to 500 rpm, and continue stirring until the material cools to room temperature to obtain the fluorine-doped carbon-coated spinel heterostructure synergistic modified lithium-rich manganese-based cathode material. Scanning electron microscopy (SEM) testing was performed on it, and the results are as follows: Figure 2 As shown, the material exhibits a regular pore morphology and a dense, smooth coating layer on its surface. To further determine the structural changes in the material, electron paramagnetic resonance (EPR) testing was performed on the dried material. Figure 3 As shown, the characteristic signal at g=2.003 corresponds to oxygen vacancy defects in the material. The spectrum reveals that the signal intensity at g=2.003 in Example 3 (solid line) is significantly higher than that in Comparative Example 1 (dashed line). This is because during the high-temperature process, the fluoride ions released from the decomposition of polyvinylidene fluoride interact with the oxygen in the LRMC surface lattice. Simultaneously, the high-speed stirring in the high-temperature coating machine promotes the formation of micro-defects in the surface structure, generating more oxygen vacancy defects. These additional oxygen vacancies induce in-situ growth of the spinel heterostructure and further enhance structural stability.

[0045] Example 4: (1) Take 2.0g of polytetrafluoroethylene (number average molecular weight 1,500,000) and 100.0g of lithium-rich manganese matrix material (the lithium-rich manganese matrix material is prepared by conventional co-precipitation combined with high-temperature lithiation, see Comparative Example 1) and add them to the conical mixing tank of the high-temperature coating machine. Start the equipment and stir and premix evenly at a speed of 500rpm.

[0046] (2) Keep the equipment running, increase the stirring speed to 1500 rpm, and at the same time raise the temperature of the barrel to 500 ℃ through the barrel wall heating plate at a heating rate of 5 ℃ / min, and keep it warm for 5 hours.

[0047] (3) Stop heating, reduce the stirring speed to 500 rpm, and continue stirring until the material cools to room temperature to obtain the fluorine-doped carbon-coated spinel heterostructure synergistic modification lithium-rich manganese-based cathode material.

[0048] Example 5: (1) Take 1.0g sucrose, 1.0g ammonium fluoride, 0.5g ammonium dihydrogen phosphate (the purity of the raw materials is greater than 99%) and 100.0g lithium-rich manganese-based matrix material (the lithium-rich manganese-based matrix material is prepared by conventional co-precipitation combined with high-temperature lithiation, see Comparative Example 1) and add them to the conical mixing tank of the high-temperature coating machine. Start the equipment and stir and premix evenly at a speed of 500rpm.

[0049] (2) Keep the equipment running, increase the stirring speed to 1500 rpm, and at the same time raise the temperature of the barrel to 300℃ (higher than the melting point of sucrose, ammonium fluoride and ammonium dihydrogen phosphate) by heating the barrel wall heating plate at a heating rate of 5℃ / min, and keep it warm for 5h.

[0050] (3) Stop heating, reduce the stirring speed to 500 rpm, and continue stirring until the material cools to room temperature to obtain the lithium-rich manganese-based cathode material with fluorine-phosphorus co-doped carbon coating and spinel heterostructure synergistic modification.

[0051] Comparative Example 1: Comparative Example 1: The lithium-rich manganese-based cathode material was not modified. The precursor prepared by co-precipitation method has the chemical formula Mn. 0.50 Ni 0.48 Co 0.02 (OH)₂. The precursor and lithium carbonate were weighed according to stoichiometry and mixed evenly using a high-speed mixer before sintering. The pre-sintering regime was: heating to 600℃ at a rate of 5℃ / min and holding for 8 hours. The high-temperature sintering regime was: continuing to heat to 800℃ at a rate of 5℃ / min and holding for 12 hours to obtain lithium-rich manganese-based cathode material.

[0052] Comparative Example 2: (1) Take 2.0g of glucose and 100.0g of lithium-rich manganese-based matrix material (the lithium-rich manganese-based matrix material is prepared by conventional co-precipitation combined with high-temperature lithiation, see Comparative Example 1) and add them to the mixing tank of the high-temperature coating machine. Start the equipment and stir and premix evenly at a speed of 500rpm.

[0053] (2) Keep the equipment running, increase the stirring speed to 1500 rpm, and at the same time raise the temperature of the barrel to 300 ℃ through the barrel wall heating plate at a heating rate of 5 ℃ / min, and keep it warm for 5 hours.

[0054] (3) Stop heating, reduce the stirring speed to 500 rpm, and continue stirring until the material cools to room temperature to obtain carbon-coated modified lithium-rich manganese-based cathode material.

[0055] Comparative Example 3: (1) Take 2.0g of ammonium fluoride and 100.0g of lithium-rich manganese matrix material (the lithium-rich manganese matrix material is prepared by conventional co-precipitation combined with high-temperature lithiation, see Comparative Example 1) and add them to the mixing tank of the high-temperature coating machine. Start the equipment and stir and premix evenly at a speed of 500rpm.

[0056] (2) Keep the equipment running, increase the stirring speed to 1500 rpm, and at the same time raise the temperature of the barrel to 200°C at a heating rate of 5°C / min through the barrel wall heating plate, and keep it warm for 5 hours.

[0057] (3) Stop heating, reduce the stirring speed to 500 rpm, and continue stirring until the material cools to room temperature to obtain fluorine-doped modified lithium-rich manganese-based cathode material.

[0058] Comparative Example 4: (1) Take 1.0g glucose, 1.0g ammonium fluoride, and 100.0g lithium-rich manganese-based matrix material (the lithium-rich manganese-based matrix material is prepared by conventional co-precipitation combined with high-temperature lithiation, see Comparative Example 1), add 80mL deionized water, and ultrasonically disperse for 30min to obtain a suspension.

[0059] (2) Transfer the suspension to a 100mL polytetrafluoroethylene reactor, perform hydrothermal reaction at 180℃ for 24h, cool, filter, wash, and dry at 60℃ for 12h.

[0060] (3) Place the dried product in a tube furnace, keep it at 500°C for 2 hours under an argon atmosphere, and cool it naturally to obtain a fluorine-doped carbon-coated modified lithium-rich manganese-based cathode material prepared by hydrothermal method.

[0061] Lithium-ion battery manufacturing: The lithium-rich manganese-based cathode materials prepared in the examples and comparative examples were assembled into liquid half-cells. The assembly method is as follows: the prepared lithium-rich cathode material or modified lithium-rich cathode material, acetylene black, polyvinylidene fluoride and N-methylpyrrolidone were mixed in a ratio of 8:1:1 to form a slurry, which was uniformly coated on the surface of aluminum foil. The cathode sheet was obtained by coating, drying, stamping and rolling in sequence.

[0062] A lithium-ion battery was obtained by using lithium foil as the negative electrode and a high-voltage durable electrolyte (1 mol / L LiPF6, solvent EC / DEC / DMC=1:1:1, with 5 wt% fluoroethylene carbonate (FEC)) as the electrolyte and assembling it in a glove box.

[0063] The cycle performance of the lithium-ion battery was tested using an electrochemical testing instrument at a temperature of 25°C and a current density of 0.1C (1C = 150 mAg). -1 The charge / discharge voltage range is 2.5 to 4.4V. The initial charge / discharge performance and cycle performance of the battery are tested (Table 2).

[0064] Table 2 Initial charge / discharge performance and cycle performance

[0065] The performance test results of 500 cycles at 2C in the table further verify the effect of the modification strategy of this invention on improving the long-term cycling stability of the material. After 500 cycles at 2C rate, Example 3, with its more abundant oxygen vacancies and uniform coating structure, achieved the optimal balance in capacity, efficiency, and cycling stability, exhibiting the best electrochemical performance. Its first-cycle discharge specific capacity was 175.5 mAh / g, first-cycle efficiency was 94%, and capacity retention reached 93.4%, demonstrating excellent structural and interfacial stability. Comparative Example 1, which did not undergo the modification process of this invention, performed significantly worse than all other examples, indicating that the unmodified material is prone to structural degradation and interfacial side reactions during cycling.

[0066] Data demonstrates that the synergistic modification strategy of fluorine-doped carbon coating, spinel heterostructure, and oxygen vacancy defects, obtained through precise control of the high-temperature coating process, can effectively suppress problems such as electrolyte erosion, transition metal migration, and layered phase transition during cycling, thereby significantly improving the long-term cycle life of lithium-rich manganese-based cathode materials.

[0067] The above embodiments are merely illustrative of the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and substance defined by the claims of the present invention; and such modifications or substitutions are still within the scope defined by the claims of the present invention.

Claims

1. A fluorine-doped carbon-coated-spinel heterostructure synergistically modified lithium-rich manganese-based positive electrode material, characterized in that, The lithium-rich manganese-based material substrate includes a layered lithium-rich body phase and an outer layer formed oxygen vacancy defect layer with spinel heterostructure. The lithium-rich manganese-based material substrate includes a layered lithium-rich body phase and an outer layer formed oxygen vacancy defect layer with spinel heterostructure. The coating layer is a fluorine-doped carbon coating layer or a fluorine-phosphorus co-doped carbon coating layer. 2.The lithium-rich manganese-based cathode material of claim 1, characterized in that, The structure of the lithium-rich manganese-based material substrate has a general formula of xLi2MnO3·(1-x)LiMO2, wherein 0.1≤x≤0.9, M is selected from one or more of Ni, Co, Mn, Cr, Al, Mg, Mo, Ru, Nb, Zr and Sn, and at least includes Ni, Co and Mn.

3. The lithium-rich manganese-based cathode material with fluorine-doped carbon coating and spinel heterostructure synergistic modification according to claim 1, characterized in that, The thickness of the coating layer is 1-100 nm. 4.The lithium-rich manganese-based cathode material of claim 1, characterized in that, The spinel heterostructure is of LiMn2O4 type.

5. A method for preparing the fluorine-doped carbon-coated-spinel heterostructure synergistically modified lithium-rich manganese-based positive electrode material according to any one of claims 1-4, characterized in that, The method comprises the following steps: The lithium-rich manganese-based material is used as a substrate, a fluorine source, a carbon source and an optional phosphorus source are provided by a single medium or a composite medium, and after being uniformly mixed, the temperature is raised to above the melting point temperature of the fluorine / carbon compound, and under the action of mechanical mixing and high-temperature melting, an oxygen vacancy defect layer and a coating layer are sequentially formed on the surface of the layered lithium-rich body phase to obtain a lithium-rich manganese-based positive electrode material modified by fluorine-doped carbon coating and spinel heterostructure.

6. The production method according to claim 5, wherein The fluorine source and the carbon source are from a combination of a single fluorine source and a single carbon source, or from a carbon-fluorine co-doped source; The single carbon source is selected from at least one of glucose, sucrose and carbon black; and the single fluorine source is selected from at least one of ammonium fluoride, lithium fluoride and sodium fluoride. The carbon-fluorine co-doped source is selected from any one or more of polyvinylidene fluoride, polytetrafluoroethylene and polyperfluoroethylene. The phosphorus source is selected from at least one of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, sodium hypophosphite and lithium phosphate.

7. The preparation method according to claim 5, characterized in that, The total mass of the fluorine source, the carbon source and the optional phosphorus source is 0.1%-10.0% of the mass of the lithium-rich manganese-based material.

8. The preparation method according to claim 5, characterized in that, The mechanical mixing and high-temperature melting are realized by using a high-temperature coating machine.

9. The production method according to claim 8, characterized by, The method specifically comprises the following steps: The selected fluorine / carbon-containing compound and the lithium-rich manganese-based material are stirred in the high-temperature coating machine at a stirring speed of 500-1000 rpm for pre-mixing, and then stirred at a stirring speed of 1500-1800 rpm; the temperature is raised to above the melting point temperature of the fluorine / carbon source at a heating rate of 1-10 ℃ / min in an air atmosphere, stirring is stopped after maintaining the stirring and keeping the temperature for 2-8 h to obtain a lithium-rich manganese-based positive electrode material modified by fluorine-doped carbon coating and spinel heterostructure.

10. A lithium ion battery comprising a positive electrode, a negative electrode and an electrolyte, wherein the positive electrode comprises the lithium-rich manganese-based positive electrode material modified by fluorine-doped carbon coating and spinel heterostructure according to any one of claims 1-4 or prepared by the preparation method according to any one of claims 5-9.

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