Method for preparing sodium ion battery high-entropy oxide positive electrode material from red mud extract

Abstract

The invention discloses a method for preparing a sodium-ion battery high-entropy oxide positive electrode material from a red mud extract, and relates to the technical field of battery positive electrode material preparation. According to the method, the red mud is used as one of main raw material sources, aluminum, iron, titanium and magnesium elements naturally coexisting in the red mud are used as multi-metal component precursors, sodium, nickel and manganese elements are introduced as additional components, and a high-entropy oxide positive electrode material system is constructed through multi-element cooperative regulation and control. The preparation method comprises the steps of red mud pretreatment, uniform mixing with an external metal source, thermal activation treatment, sodium source introduction, mechanical ball milling, high-temperature sintering and the like, and the multi-component high-entropy oxide positive electrode material with the layered structure is prepared. In the material, various metal elements are distributed in crystal lattices in a highly disordered manner, a stable high-entropy structure is formed, phase separation and structural collapse are effectively inhibited, and the structural stability and electrochemical reaction kinetics performance of the material in the charging and discharging process are improved.

Description

Technical Field

[0001] This invention belongs to the technical field of battery material preparation and solid waste resource utilization, and specifically relates to the preparation of multi-metal oxide cathode materials, specifically a method for preparing high-entropy oxide cathode materials for sodium-ion batteries using red mud extract. Background Technology

[0002] Against the backdrop of accelerated global energy structure transformation and the continued advancement of "dual-carbon" goals, large-scale energy storage technology has become a key foundation for supporting the high proportion of renewable energy grid connection and stable operation. Among them, secondary batteries play an irreplaceable role in areas such as renewable energy power generation and consumption, grid peak shaving, and electric transportation due to their high energy conversion efficiency, fast response speed, and wide range of applications. With increasing resource constraints and cost pressures, developing novel battery cathode materials that are widely available, environmentally friendly, and have stable performance has become an important research direction in the field of energy materials.

[0003] Sodium-ion batteries are considered an important supplement or even replacement for lithium-ion batteries due to the abundance, wide distribution, and low cost of sodium resources. However, existing cathode materials generally suffer from limited specific capacity, insufficient structural stability, and rapid cycle life decay due to factors such as the large radius of sodium ions and slow electrochemical reaction kinetics. Especially during repeated charge-discharge cycles, cathode materials are prone to structural collapse and phase transitions, severely restricting the practical application of sodium-ion batteries. Therefore, constructing novel cathode material systems with stable structures, tunable compositions, and excellent electrochemical performance is crucial for improving the performance of sodium-ion batteries. In recent years, high-entropy materials have gradually attracted widespread attention in the field of battery materials due to their multi-principal component composition, high configurational entropy effect, and the resulting enhanced lattice stability and synergistic performance optimization. High-entropy oxide cathode materials, by introducing various metal elements into the disordered solid solution of the lattice, can effectively suppress structural phase transitions, improve ion diffusion channels, and enhance cycle stability. However, the preparation of existing high-entropy oxide cathode materials usually relies on a variety of high-purity metal oxides as raw materials, which not only has high preparation costs, but also has shortcomings in resource utilization efficiency and environmental friendliness, thus limiting their large-scale application.

[0004] Red mud is a large-scale solid waste generated during the Bayer process in the alumina industry. Rich in various metallic elements such as iron, aluminum, titanium, and magnesium, it has long faced the challenges of large stockpiles, high treatment costs, and significant environmental risks. Efficiently introducing the multi-metal components from red mud into battery cathode material systems would not only facilitate the high-value utilization of solid waste but also provide a new raw material source for the low-cost preparation of high-entropy materials. Therefore, developing a method for directly utilizing red mud extract as a multi-metal source to synergistically construct high-entropy oxide cathode materials has significant scientific and application value for reducing battery material costs, improving resource utilization efficiency, and promoting the sustainable development of green energy technologies. Summary of the Invention

[0005] This invention addresses the common problems in existing sodium-ion battery cathode materials, such as high raw material costs, heavy reliance on high-purity metal oxides in the preparation process, and insufficient utilization of solid waste resources. It provides a method for preparing high-entropy oxide cathode materials for sodium-ion batteries using red mud extract. This invention uses red mud extract as the primary multi-metal source and employs a multi-component synergistic construction method to build a high-entropy oxide structure for the battery cathode material. By directly introducing multiple metal elements abundant in red mud and synergistically adding a small amount of external metal sources to construct the high-entropy oxide structure, this method significantly reduces raw material costs while simultaneously improving the structural stability and electrochemical performance of the cathode material.

[0006] This invention is achieved through the following technical solution: A method for preparing high-entropy oxide cathode materials for sodium-ion batteries from red mud extract includes the following steps: (1) Take red mud raw material, wash it repeatedly with deionized water until the pH value of the washing liquid is less than 9, filter and dry it, and then heat and keep it in a muffle furnace in an air atmosphere. After that, it is naturally cooled to obtain red mud pretreated material.

[0007] Among them, water washing is used to remove residual free alkali and soluble impurities in red mud; roasting in a muffle furnace is used to stabilize the existing forms of metal elements such as aluminum, iron, titanium and magnesium in red mud and improve their subsequent solid-phase reaction activity.

[0008] (2) Weigh the red mud pretreated material obtained in step (1), which contains aluminum, iron, titanium and magnesium elements.

[0009] In the red mud pretreatment material, aluminum, iron, titanium and magnesium elements mainly exist in the form of oxides or composite oxides. The red mud pretreatment material is used as a source of multi-metal components to replace part of the single high-purity metal oxide raw materials, thereby reducing the preparation cost of cathode materials.

[0010] (3) Weigh out nickel oxide, manganese oxide and sodium carbonate as external metal sources and sodium sources.

[0011] The external metal sources include nickel oxide and manganese oxide, with nickel oxide being NiO and manganese oxide being MnO2. Sodium carbonate is also introduced as a sodium source, forming a multi-component high-entropy oxide precursor system containing Al, Fe, Ti, Mg, Na, Ni and Mn.

[0012] (4) Add the raw materials obtained in steps (2) and (3) into a glass sample bottle, add anhydrous ethanol as a dispersant, and obtain a mixed suspension.

[0013] Anhydrous ethanol is used as a dispersant to improve the dispersion uniformity between the red mud extract and the added metal source, reduce agglomeration, and thus facilitate the full mixing of multi-metal components during subsequent heat treatment and ball milling.

[0014] (5) Place the mixed suspension obtained in step (4) into a vortex oscillator for dispersion and mixing to achieve preliminary uniform dispersion of the multi-metal components.

[0015] The dispersion and mixing are achieved by a vortex oscillator. The vortex oscillation is used to promote full contact between the red mud extract and the added metal source under liquid phase conditions, so that the various metal components form a relatively uniform suspension system in the solvent system.

[0016] (6) Transfer the mixture after step (5) to a tube furnace, and heat and hold it in an air atmosphere, and then cool it naturally to obtain a preheated activated mixture.

[0017] The preheating activation treatment is carried out in a tube furnace under an air atmosphere to remove residual organic solvents from the dispersion process, while promoting the initial solid-phase reaction between the red mud extract and the added metal source, providing an active basis for subsequent high-energy ball milling and high-temperature sintering.

[0018] (7) Add the preheated and activated mixture obtained in step (6) into the ball mill jar of the planetary ball mill, add zirconia balls as grinding media, and add anhydrous ethanol as a ball milling dispersant.

[0019] Mechanical ball milling is used to achieve thorough mixing of multiple metal elements at the microscale to obtain a multi-metal mixed powder with uniform composition. Anhydrous ethanol is used as a ball milling dispersant to improve the dispersion uniformity between the red mud extract and the added metal source, reduce agglomeration, and thus facilitate thorough mixing of multi-metal components during subsequent heat treatment and ball milling.

[0020] (8) After ball milling, the resulting slurry is dried to remove the ethanol dispersant and obtain ball-milled mixed powder.

[0021] (9) The ball-milled mixed powder obtained in step (8) is placed in a muffle furnace and heated and kept warm in an air atmosphere. Then it is naturally cooled to obtain a layered high-entropy oxide cathode material.

[0022] The high-temperature sintering in the muffle furnace is used to promote the solid-phase reaction of various metal elements in the crystal lattice and achieve uniform solid solution, forming a high-entropy oxide cathode material with a layered crystal structure. In this cathode material, various metal elements are highly disordered and suitable as a cathode active material for sodium-ion batteries.

[0023] As a preferred technical solution of the present invention, in step (1), the red mud raw material is derived from the red mud solid waste generated during the Bayer process of alumina production; the heating in the muffle furnace is to raise the temperature to 500°C at a heating rate of 5°C / min and hold it at that temperature for 3 hours.

[0024] As a preferred technical solution of the present invention, in step (2), 4g of red mud pretreatment material is weighed. The aluminum, iron, titanium and magnesium elements in the red mud pretreatment material mainly exist in the form of oxides or composite oxides.

[0025] As a preferred technical solution of the present invention, in step (3), 1 g of nickel oxide, 1 g of manganese oxide and 2 g of sodium carbonate are weighed.

[0026] As a preferred technical solution of the present invention, in step (4), the amount of ethanol added is 30 mL.

[0027] As a preferred technical solution of the present invention, in step (5), the vortex oscillator is a Vortex-Genie 2 with an oscillation frequency of 70 Hz and an oscillation time of 60 min.

[0028] As a preferred technical solution of the present invention, in step (6), the heating in the tube furnace is heated to 400 ℃ at a heating rate of 5 ℃ / min and held at that temperature for 2 h.

[0029] As a preferred technical solution of the present invention, in step (7), the planetary ball mill is model QM-3SP4, the ball milling speed is adjustable in the range of 800–1200 r / min, the ball milling time is adjustable in the range of 8–24 h, and the amount of ethanol added is 20 mL.

[0030] As a preferred technical solution of the present invention, in step (8), the drying temperature is below 80 ℃.

[0031] As a preferred technical solution of the present invention, in step (9), the temperature in the muffle furnace is increased to 900 ℃ at a heating rate of 5 ℃ / min and held for 5 h.

[0032] Compared with the prior art, the beneficial effects of the present invention mainly include the following points: (1) This invention has significant advantages in terms of raw material system and resource utilization method. Traditional battery cathode materials mostly rely on high-purity metal oxides as precursors, which not only has high preparation cost, but also high energy consumption and heavy environmental burden in the resource acquisition process. This invention uses industrial red mud of alumina as the main metal source, and directly utilizes the Al, Fe, Ti and Mg elements enriched in it to construct a multi-component system, realizing the high-value utilization of industrial solid waste. While reducing raw material costs, it effectively alleviates the environmental risks caused by long-term stockpiling of red mud, and has obvious resource and environmental synergistic benefits.

[0033] (2) Compared with conventional single or few-component cathode materials, the high-entropy oxide cathode material constructed in this invention is more advanced in terms of structure and composition design. By introducing external metal elements such as Na, Ni and Mn, a high-entropy system is formed together with multiple metal components in the red mud extract. The highly disordered distribution of multiple cations in the lattice significantly increases the configurational entropy of the system, which is beneficial to stabilizing the layered structure and inhibiting phase separation and structural collapse, thereby providing an intrinsic guarantee for the structural stability of the material during the charging and discharging process.

[0034] (3) In terms of preparation process, the present invention has better process controllability and component uniformity compared with the prior art. Through the synergistic cooperation of steps such as water washing-calcination pretreatment, liquid phase dispersion, preheating activation, high-energy ball milling and high-temperature sintering, the complex red mud extract and the added metal source are fully mixed and uniformly dissolved at the microscale, which effectively avoids the common problems of component segregation and incomplete reaction in the direct solid-phase reaction of red mud, thereby ensuring the consistency and reproducibility of the composition and structure of the final product.

[0035] (4) From the perspective of electrochemical applications, the layered high-entropy oxide cathode material prepared in this invention has potential comprehensive performance advantages in sodium-ion battery systems. The synergistic effect of multiple metals not only helps to regulate the valence state distribution and electronic structure of transition metals, but also improves the intercalation / deintercalation kinetics of Na⁺ between layers, thereby enhancing the rate performance and cycle stability of the material. This method has the advantages of wide availability of raw materials, clear process route, and ease of scale-up, and has good prospects for engineering and industrial applications. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments of the present invention will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a scanning electron microscope image of the precursor of the mixture of red mud and added oxides preheated in the tubular furnace in Example 1.

[0038] Figure 2 This is a scanning electron microscope image of the sample after sintering in a muffle furnace following the addition of sodium carbonate in Example 1.

[0039] Figure 3 The image shows the XRD pattern and structural schematic diagram of the high-entropy oxide cathode material (NaNiFeMnAlMgTiO) prepared by the method in Example 1.

[0040] Figure 4 The image shows a transmission electron microscope-energy dispersive spectroscopy (TEM) image of the high-entropy oxide cathode material (NaNiFeMnAlMgTiO) prepared by the method in Example 1. Detailed Implementation

[0041] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0042] This invention provides a method for preparing high-entropy oxide cathode materials for sodium-ion batteries from red mud extract, specifically including the following steps: (1) First, red mud solid waste from the Bayer process of alumina production was selected as red mud raw material. The red mud raw material was washed multiple times with deionized water until the pH value of the washing liquid was less than 9, so as to effectively remove the free alkali and soluble salt impurities remaining in the red mud. Then, the washed red mud raw material was filtered, dried, and placed in a muffle furnace. The temperature was raised to 500 ℃ at a heating rate of 5 ℃ / min under air atmosphere and held for 3 h. The presence forms of metal elements such as aluminum, iron, titanium, and magnesium in the red mud raw material were stabilized by calcination to obtain red mud pretreated material.

[0043] (2) Weigh 4 g of the red mud pretreatment material obtained in step (1) as a source of multiple metals. The aluminum, iron, titanium and magnesium elements in the red mud pretreatment material are mainly in the form of oxides or composite oxides. The red mud pretreatment material is used to partially or completely replace traditional high-purity metal oxide raw materials, thereby reducing the preparation cost of cathode materials from the source.

[0044] (3) Based on the red mud pretreatment material, an external metal source is introduced to regulate the overall composition of the material. Specifically, 1 g of nickel oxide and 1 g of manganese oxide are weighed, and 2 g of sodium carbonate is added as a sodium source. The nickel oxide is NiO and the manganese oxide is MnO2 or Mn2O3, so that a multi-component high-entropy oxide precursor system containing Al, Fe, Ti, Mg, Na, Ni and Mn is formed in the system.

[0045] (4) The red mud pretreated material obtained in step (2) and the external metal source and sodium source obtained in step (3) are added together into a glass sample bottle. Anhydrous ethanol is added as a dispersant. The amount of ethanol added is 30 mL. The aggregation tendency between solid particles is reduced by the liquid phase environment, which provides conditions for subsequent uniform mixing.

[0046] (5) The above-mentioned mixture is placed in a vortex oscillator for dispersion and mixing. The preferred model of the vortex oscillator is Vortex-Genie 2. The oscillation frequency is set to 70 Hz and the oscillation time is 60 min. In the ethanol medium, the red mud extract and the added metal source are fully contacted, so that the multi-metal components form a relatively uniform and stable suspension system.

[0047] (6) The mixture after vortex oscillation is transferred to a tube furnace and heated to 400 ℃ at a heating rate of 5 ℃ / min in air atmosphere and held for 2 h. The residual ethanol dispersant is removed by preheating activation treatment, and the initial solid-phase reaction between the multi-metal components is induced to improve the overall reaction activity of the system, so as to obtain the preheated activated mixture.

[0048] (7) The preheated and activated mixture obtained in step (6) is added to the grinding jar of a planetary ball mill. Zirconia balls are added as grinding media, and anhydrous ethanol is added again as a ball milling dispersant. The amount of ethanol added is 20 mL. The particle size is further refined and the uniform mixing of the multi-metal components at the microscale is enhanced by wet ball milling. The ball milling process is carried out in a planetary ball mill. The preferred model of the planetary ball mill is QM-3SP4. The ball milling speed is adjustable in the range of 800–1200 r / min (800 r / min, 1000 r / min, 1200 r / min, etc. can be selected), and the ball milling time is adjustable in the range of 8–24 h (8h, 12h, 24h, etc. can be selected). Under the action of high-energy machinery, the various metal components are fully mixed and a homogeneous multi-metal mixed powder is formed.

[0049] (8) After ball milling, the resulting slurry is dried at 80 °C to remove the ethanol dispersant and obtain ball-milled mixed powder.

[0050] (9) The ball-milled mixed powder obtained in step (8) is placed in a muffle furnace and heated to 900 ℃ at a heating rate of 5 ℃ / min in air atmosphere and held for 5 h. Through high-temperature sintering, a variety of metal elements are fully dissolved in the crystal lattice, and finally a high-entropy oxide cathode material with a layered crystal structure and highly disordered distribution of metal elements is formed. This cathode material is suitable as a cathode active material for sodium-ion batteries.

[0051] This invention uses red mud as one of the main raw material sources, utilizing the naturally coexisting aluminum (Al), iron (Fe), titanium (Ti), and magnesium (Mg) elements in red mud as multi-metal precursors, and introducing sodium (Na), nickel (Ni), and manganese (Mn) elements as external components. A high-entropy oxide cathode material system is constructed through multi-element synergistic regulation. The invention includes steps such as red mud pretreatment, uniform mixing with external metal sources, thermal activation treatment, sodium source introduction, mechanical ball milling, and high-temperature sintering to prepare a multi-component high-entropy oxide cathode material with a layered structure. In this material, multiple metal elements are highly disordered in the crystal lattice, forming a stable high-entropy structure, effectively suppressing phase separation and structural collapse, and improving the structural stability and electrochemical reaction kinetics performance of the material during charge and discharge processes. Compared with existing preparation methods that use a single high-purity metal oxide raw material, this invention directly uses red mud extract to replace part of the traditional metal oxide raw material, realizing the resource utilization and high-value utilization of solid waste, reducing the preparation cost of cathode materials, and at the same time endowing the material with good cycle stability and rate performance. It has significant economic and environmental benefits and is suitable for the preparation and application of secondary battery cathode materials.

[0052] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and are therefore merely examples and should not be used to limit the scope of protection of the present invention. It should be noted that, unless otherwise stated, the technical or scientific terms used in this application should have the ordinary meaning understood by those skilled in the art to which this invention pertains. Example 1

[0053] A method for preparing high-entropy oxide cathode materials for sodium-ion batteries from red mud extract includes the following steps: (1) Select red mud solid waste from the Bayer process of alumina production as red mud raw material. Weigh an appropriate amount of red mud raw material, add deionized water and wash it multiple times until the pH value of the washing solution is less than 9, so as to remove the free alkali and soluble salt impurities remaining in the red mud raw material. After washing, filter and dry the red mud raw material.

[0054] (2) The dried red mud raw material is placed in a muffle furnace and heated to 500 ℃ at a heating rate of 5 ℃ / min in an air atmosphere and held for 3 h. Then it is naturally cooled to obtain the red mud pretreated material. This pretreatment process is used to stabilize the existence form of metal elements such as aluminum, iron, titanium and magnesium in the red mud.

[0055] (3) Weigh 4 g of the red mud pretreatment material obtained in step (2) as a multi-metal source material, wherein the aluminum, iron, titanium and magnesium elements in the red mud pretreatment material are mainly in the form of oxides or composite oxides.

[0056] (4) Based on the above-mentioned red mud pretreatment material, weigh out 1 g of nickel oxide, 1 g of manganese oxide and 2 g of sodium carbonate as external metal source and sodium source, wherein nickel oxide is NiO and manganese oxide is MnO2.

[0057] (5) Add the raw materials obtained in steps (3) and (4) together into a glass sample bottle, add anhydrous ethanol as a dispersant, and add 30 mL of ethanol to form a multi-metal suspension.

[0058] (6) The above-mentioned multi-metal suspension was placed in a vortex oscillator for dispersion and mixing. The vortex oscillator was a Vortex-Genie 2, the oscillation frequency was set to 70 Hz, and the oscillation time was 60 min, so as to promote the uniform dispersion of red mud extract and added metal source in the liquid phase system.

[0059] (7) The mixture after vortex oscillation is transferred to a tube furnace and heated to 400 °C at a heating rate of 5 °C / min in air atmosphere and held for 2 h. Then it is naturally cooled to obtain a preheated activated mixture.

[0060] The morphology of the obtained preheated and activated mixture was characterized, and the scanning electron microscopy results are as follows: Figure 1 As shown, the sample exhibits a blocky structure with a particle size of approximately 1 μm, indicating that the multi-metal components undergo preliminary solid-bonding during the preheating process.

[0061] (8) Add the above preheated and activated mixture to the ball mill jar of the planetary ball mill, add zirconia balls as grinding media, and add anhydrous ethanol as a ball milling dispersant. The amount of ethanol added is 20 mL. The preferred model of the planetary ball mill is QM-3SP4, the ball milling speed is 1000 r / min, and the ball milling time is 12 h.

[0062] (9) After ball milling, the resulting slurry is dried at 80 °C to remove the ethanol dispersant and obtain ball-milled mixed powder.

[0063] (10) The ball-milled mixed powder was placed in a muffle furnace and heated to 900 ℃ at a heating rate of 5 ℃ / min in air atmosphere and held for 5 h to finally form a high-entropy oxide cathode material with a layered crystal structure and highly disordered distribution of metal elements.

[0064] The scanning electron microscopy results of the obtained high-entropy oxide cathode material are as follows: Figure 2 As shown, the sample exhibits a layered structure with a single layer thickness of approximately 100 nm, indicating that the introduction of sodium carbonate is beneficial to the formation of the layered structure. Example 2

[0065] Based on Example 1, the crystal structure of the prepared high-entropy oxide cathode material was analyzed, as follows: The high-entropy oxide cathode material sample obtained after high-temperature sintering in Example 1 was subjected to X-ray diffraction (XRD) testing, and the test results are as follows: Figure 3 As shown. By Figure 3 It can be seen that the XRD diffraction peaks of this material are consistent with the typical layered oxide structure, indicating that the material has successfully formed a layered crystal structure.

[0066] Analysis of the structural diagram shows that multiple metal elements such as aluminum, iron, titanium, magnesium, nickel, manganese and sodium are synergistically dissolved in the crystal lattice in the prepared cathode material, constructing a high-entropy oxide structure with highly disordered distribution characteristics. This structure is beneficial to improving the insertion and extraction stability of sodium ions in the cathode material. Example 3

[0067] To further verify the distribution of multi-metal elements in the high-entropy oxide cathode material obtained in Example 1, transmission electron microscopy and energy dispersive spectroscopy were performed on the material, as detailed below: The high-entropy oxide cathode material sample prepared in Example 1 was subjected to transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS). The test results are as follows: Figure 4 As shown. By Figure 4 It can be seen that the sample has a uniform structure at the nanoscale. In the energy spectrum distribution of each element, Na, Ni, Fe, Mn, Al, Mg and Ti elements show a highly uniform distribution inside the particles.

[0068] The above results indicate that, by using the method described in this invention, with red mud extract as the main source of multiple metals and combined with a small amount of external metal sources, a uniform mixing and solid solution of multiple metal elements can be achieved at the microscale, thereby successfully constructing a high-entropy oxide cathode material with uniform composition and stable structure.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; 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 still 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; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A method for preparing high-entropy oxide cathode materials for sodium-ion batteries from red mud extract, characterized in that, Includes the following steps: (1) Take red mud raw material, wash it repeatedly with deionized water until the pH value of the washing liquid is less than 9, filter and dry it, and then heat and keep it in a muffle furnace in an air atmosphere. After that, it is naturally cooled to obtain red mud pretreated material. (2) Weigh the red mud pretreated material obtained in step (1), which contains aluminum, iron, titanium and magnesium elements; (3) Weigh out nickel oxide, manganese oxide and sodium carbonate as external metal sources and sodium sources; (4) Add the raw materials obtained in steps (2) and (3) into a glass sample bottle, add anhydrous ethanol as a dispersant, and obtain a mixed suspension; (5) Place the mixed suspension obtained in step (4) into a vortex shaker for dispersion and mixing to achieve preliminary uniform dispersion of the multi-metal components; (6) Transfer the mixture after step (5) to a tube furnace, heat and hold it in air atmosphere, and then cool it naturally to obtain a preheated activated mixture; (7) Add the preheated and activated mixture obtained in step (6) into the ball mill jar of the planetary ball mill, add zirconia balls as grinding media, and add anhydrous ethanol as a ball milling dispersant; (8) After ball milling, the resulting slurry is dried to remove the ethanol dispersant and obtain ball-milled mixed powder; (9) The ball-milled mixed powder obtained in step (8) is placed in a muffle furnace and heated and kept warm in an air atmosphere. Then it is naturally cooled to obtain a layered high-entropy oxide cathode material.

2. The method for preparing high-entropy oxide cathode material for sodium-ion batteries from red mud extract according to claim 1, characterized in that: In step (1), the red mud raw material comes from the red mud solid waste generated during the Bayer process of alumina production; the heating in the muffle furnace is to raise the temperature to 500 ℃ at a heating rate of 5 ℃ / min and hold it at that temperature for 3 h.

3. The method for preparing high-entropy oxide cathode material for sodium-ion batteries from red mud extract according to claim 2, characterized in that: In step (2), 4g of red mud pretreatment material is weighed out. The aluminum, iron, titanium and magnesium elements in the red mud pretreatment material mainly exist in the form of oxides or composite oxides.

4. The method for preparing high-entropy oxide cathode material for sodium-ion batteries from red mud extract according to claim 3, characterized in that: In step (3), weigh out 1 g of nickel oxide, 1 g of manganese oxide and 2 g of sodium carbonate.

5. The method for preparing high-entropy oxide cathode material for sodium-ion batteries from red mud extract according to claim 4, characterized in that: In step (4), the amount of ethanol added is 30 mL.

6. The method for preparing high-entropy oxide cathode material for sodium-ion batteries from red mud extract according to claim 5, characterized in that: In step (5), the vortex oscillator is a Vortex-Genie 2 with an oscillation frequency of 70 Hz and an oscillation time of 60 min.

7. The method for preparing high-entropy oxide cathode material for sodium-ion batteries from red mud extract according to claim 6, characterized in that: In step (6), the temperature in the tubular furnace is increased to 400 ℃ at a heating rate of 5 ℃ / min and held for 2 h.

8. The method for preparing high-entropy oxide cathode material for sodium-ion batteries from red mud extract according to claim 7, characterized in that: In step (7), the planetary ball mill model is QM-3SP4, the ball milling speed is 800–1200 r / min, the ball milling time is 8–24 h, and the amount of ethanol added is 20 mL.

9. The method for preparing high-entropy oxide cathode material for sodium-ion batteries from red mud extract according to claim 8, characterized in that: In step (8), the drying temperature is below 80 ℃.

10. The method for preparing high-entropy oxide cathode material for sodium-ion batteries from red mud extract according to claim 9, characterized in that: In step (9), the temperature in the muffle furnace is increased to 900 ℃ at a heating rate of 5 ℃ / min and held for 5 h.

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