A dual-phase high-entropy oxide sodium negative electrode material and a preparation method and application thereof

Abstract

The application provides a two-phase high-entropy oxide sodium electrode material and a preparation method and application thereof, and belongs to the technical field of preparation of sodium ion battery negative electrode materials. x Fe y Ni z Mn a M b Co c Sn d O2, the sodium ion battery negative electrode material is prepared by using a high-energy ball milling technology and organic acid post-treatment and a two-stage calcination process, the particle size, the specific surface area and the pore size range of the material are 1-2.5 mu m, 29.7-36.8 m 2 / g and 1-45 nm respectively. Under a 2.0-4.2 V charge-discharge voltage window, the retention rate of the battery is 77.55-83.26% after 200 cycles at a 1C rate; when 2C is switched to 0.1C, the capacity recovery rate is 91.08-95.32%; the high-entropy oxide sodium electrode material exhibits the characteristics of high initial coulombic efficiency, long cycle stability, reversibility and excellent rate performance.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery anode material preparation technology, specifically relating to a two-phase high-entropy oxide sodium-ion battery anode material, its preparation method, and its application. Background Technology

[0002] In recent years, lithium-ion batteries have been widely used in power batteries and energy storage. However, lithium resources are limited and unevenly distributed, and the future large-scale application will inevitably be constrained by raw material resources. Sodium-ion batteries, which have a similar working principle to lithium-ion batteries, are inexpensive, abundant, and have no resource limitations, making them a good fit for the growing demand for power and energy storage systems. However, compared to lithium-ion batteries... + In comparison, Na + Due to their large ionic radius and atomic mass, mature graphite anode materials are not suitable for sodium-ion batteries. Therefore, developing an anode material with high specific capacity and excellent rate performance is of great significance for sodium-ion batteries.

[0003] Traditional metal oxide anode materials possess high theoretical specific capacity, but these materials undergo significant volume changes during charge and discharge, easily leading to structural collapse, battery deformation, and rapid performance degradation. The poor electrochemical performance caused by volume expansion and deformation is a major problem in the development of sodium-ion battery anode materials, severely hindering their advancement. The introduction of high-entropy design concepts offers a new opportunity to solve these problems.

[0004] High-entropy oxides (HEOs) are typically solid solutions formed by the mutual solid-solution of five or more transition metal elements. They possess strong inductive effects and an endogenous framework structure, exhibiting good mechanical stability. This effectively mitigates volume changes during sodium insertion / extraction. Furthermore, their endogenous framework structure enhances phase stability during battery cycling, thereby improving the stability of the electrode material. In addition, the random and disordered distribution of elements in high-entropy materials, along with their synergistic effects, improves reaction kinetics, accelerates charge transfer, and enhances conductivity and coulombic efficiency.

[0005] Chinese invention patent document CN117199339A discloses a sodium-ion battery cathode material with nitrogen-stabilized high-entropy oxide oxygen vacancies and its preparation method. The method involves weighing sodium source, calcium carbonate, nickel oxide, iron oxide, titanium oxide, tin oxide, and manganese dioxide in a molar ratio, followed by dry ball milling and two calcinations to obtain the high-entropy oxide oxygen-vacancy sodium-ion battery cathode material. This patent does not address the control of the cooling rate during calcination; the natural cooling mode easily induces internal stress accumulation and phase transitions in the material, leading to structural instability. The high-entropy oxide oxygen-vacancy sodium-ion battery cathode material obtained by this method has an O3 phase rich in oxygen vacancies, exhibiting poor stability and rapid capacity decay.

[0006] Chinese invention patent document CN115064657A discloses a high-entropy layered metal oxide, its preparation method, and its applications. The method involves using metal oxides including Li... + Cu 2+ Ni 2+ Co 3+ Fe 3+ Al 3+ Mn 3+ Mn 4+ Ti 4+ Sn 4+ Sb 5+ At least five of the ingredients are mixed in molar amounts, then ball-milled, dried, pressed into tablets, calcined at high temperature once, and ground again to obtain a high-entropy layered oxide. This method requires drying after ball milling, increasing energy consumption, and also requires high-pressure pressing at 10 MPa, increasing the process flow and making it more complex. The need for grinding after high-pressure pressing further increases the complexity of the process. This preparation method only yields P2 or O3 type high-entropy oxides. This single structure is prone to structural changes during sodium insertion / extraction in anode applications, leading to performance degradation. Summary of the Invention

[0007] The purpose of this invention is to provide a two-phase high-entropy oxide sodium electrode anode material, its preparation method, and its application. The anode material prepared by this invention through acid etching and segmented calcination has high specific surface area, porous structure, structural stability, high capacity and initial coulombic efficiency, long cycle life, and excellent rate performance. The preparation method is simple, efficient, stable, time-saving, and energy-saving, making it suitable for industrial applications.

[0008] To achieve this objective, the technical solution of the present invention is as follows:

[0009] This invention provides a two-phase high-entropy oxide sodium electrode material, wherein the chemical formula of the sodium electrode material is Na. x Fe y Ni z Mn a M b Co c Sn d O2, wherein 0.75≤x≤0.95, 0.09≤y≤0.30, 0.10≤z≤0.31, 0.30≤a≤0.48, 0≤b≤0.2, 0.02≤c≤0.1, 0.02≤d≤0.1, y+z+a+b+c+d=1, and M is either Cu or Al; the particle size of the dual-phase high-entropy oxide sodium electrode anode material is 1-2.5μm, and the specific surface area is 29.7-36.8m². 2 / g, pore size range of 1-45nm; the dual-phase high-entropy oxide sodium electrode material is a P2 / O3 dual-phase structure.

[0010] This invention also provides a method for preparing a two-phase high-entropy sodium oxide anode material, comprising the following steps:

[0011] (1) Sodium source, ferric oxide, nickel oxide, manganese dioxide, oxide of M, cobalt oxide and tin oxide are mixed according to Na x Fe y Ni z Mn a M b Co c Sn d The molar ratios of each component in the chemical formula of O2 were weighed, mixed, and then transferred to a high-energy vibration ball mill. Solvent was added for wet ball milling to obtain the first precursor material.

[0012] (2) The first precursor material is stirred and reacted in an organic acid solution, and then centrifuged and vacuum dried to obtain the second precursor material;

[0013] (3) The second precursor material is calcined in stages. A first stage of high-temperature calcination is carried out under the protective atmosphere of argon or nitrogen, and then a second stage of low-temperature calcination is carried out under the protective atmosphere of argon or nitrogen to obtain the two-phase high-entropy sodium oxide anode material.

[0014] Furthermore, in step (1), the sodium source is one of sodium carbonate, sodium bicarbonate, sodium hydroxide, and sodium acetate; the oxide of M is copper oxide or aluminum oxide.

[0015] Further, in step (1), the solvent is one of deionized water, ethanol, and methanol; the amount of solvent used is 20-30% of the total mass of sodium source, ferric oxide, nickel oxide, manganese dioxide, oxide of M, cobalt oxide and tin oxide.

[0016] Further, in step (1), the wet ball milling conditions are: ball mill speed ≥ 1000 r / min, ball-to-material weight ratio 10-15:1, and ball milling time 1-5 h.

[0017] Further, in step (2), the organic acid solution is an aqueous solution of acetic acid or an aqueous solution of oxalic acid; the concentration of the organic acid solution is 0.1-1M.

[0018] Furthermore, in step (2), the ratio of the first precursor material to the organic acid solution is 1-6g:10mL.

[0019] Furthermore, in step (2), the stirring reaction conditions are: rotation speed 100-300 r / min, reaction temperature 20-30℃, and reaction time 0.5-2 h; the vacuum drying conditions are: drying temperature 60-100℃ and drying time 6-12 h.

[0020] Further, in step (3), the first stage of high-temperature roasting conditions are: heating rate 3-10℃ / min, temperature 800-1100℃, holding reaction time 9-15h, cooling rate 3-10℃ / min, and cooling down to room temperature; the second stage of low-temperature roasting conditions are: heating rate 1-5℃ / min, temperature 200-400℃, holding reaction time 3-7h, cooling rate 3-10℃ / min, and cooling down to room temperature.

[0021] Another objective of this invention is to provide an application of the biphase high-entropy oxide sodium anode material prepared by the above method in sodium-ion batteries, and to apply it to the anode of sodium-ion batteries.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] (1) The dual-phase high-entropy oxide sodium anode material provided by this invention combines the advantages of both P2 and O3 types, overcoming the limitations of traditional single-phase O3 type materials with slow diffusion speed leading to poor rate performance and cycle performance, and single-phase P2 type materials with low sodium content leading to poor capacity. This sodium anode material has higher effective capacity, rate performance, and cycle performance. The particle size is 1-2.5 μm, and the specific surface area is 29.7-36.8 m². 2 / g, pore size 1-45nm ， Small particle size and short ion and electron transport paths effectively reduce diffusion resistance during sodium ion insertion / extraction, contributing to improved material conductivity and thus enhancing battery rate performance. Large specific surface area provides more active sites, facilitating sodium ion storage and release, thereby increasing material capacity. Appropriate pore structure improves structural stability and mitigates volume expansion during charge / discharge processes.

[0024] (2) The preparation method of the dual-phase high-entropy sodium oxide anode material provided by the present invention uses a high-energy vibration ball mill for wet ball milling, which not only ensures the uniform distribution of each component at the microscale and prevents the material from forming fixed agglomerates during the extrusion and collision process, thus preventing insufficient grinding, but also allows for the production of anode materials with small particle size and uniform mixing in a short time by controlling the rotation speed and ball-to-material ratio. After subsequent high-temperature calcination, there is no need for further crushing and sieving, and the materials can be directly used for battery assembly, achieving the effect of saving time, reducing costs and saving energy. In addition, compared with the traditional hydrothermal method, no wastewater is generated during the ball milling process.

[0025] (3) The preparation method of the dual-phase high-entropy oxide sodium anode material provided by the present invention uses an organic acid solution that can etch the precursor to produce a multi-level porous structure. The organic acid remaining in the precursor will generate CO2 during the calcination process, which prevents the collapse of the porous structure and guides the precursor to produce a larger specific surface area, thus having the dual effect of increasing the specific surface area and pore size range.

[0026] (4) The preparation method of the biphase high-entropy oxide sodium anode material provided by the present invention adopts segmented calcination. High-temperature calcination is used to overcome the reaction energy barrier, accelerate the diffusion and rearrangement of atoms, promote the initial solid-phase reaction between precursors, and further form the framework and phase structure of high-entropy oxide. Low-temperature fine-tuning calcination is used to stabilize the formed structure, improve crystallinity, promote material surface reconstruction and the generation of active sites, and prepare a high-entropy oxide anode material with excellent electrochemical performance. In addition, slow cooling is used to avoid internal stress or phase transformation caused by rapid cooling of the material, prevent the collapse of the material structure, and thus improve the electrochemical performance of the material.

[0027] (5) The dual-phase high-entropy sodium oxide anode material provided by this invention exhibits multiple advantages in its application. First, the high-entropy effect of this dual-phase high-entropy sodium oxide anode material brings about a synergistic effect of multiple elements and lattice defects, which provides more active sites, thus improving conductivity and Na+. + The material exhibits several key advantages: firstly, it enhances the transport dynamics of sodium oxide; secondly, its inherent layered structure effectively buffers volume expansion, reducing structural damage during repeated sodium insertion / extraction and improving long-cycle stability. Furthermore, the multi-element effect of the sodium oxide anode material synergistically complements the hierarchical porous structure and high specific surface area obtained after organic acid treatment, further enhancing its electrochemical performance. Within a charge / discharge voltage window of 2.0-4.2V, the initial discharge specific capacity is 416.24-455.70 mAh / g, with an initial coulombic efficiency of 80.75-90.32%. At 1C rate, the battery retains 77.55-83.26% of its capacity after 200 cycles, compared to 68.59-72.60% at 0.1C and a recovery rate of 91.08-95.32% when switching from 2C to 0.1C. Therefore, dual-phase high-entropy oxide anode materials possess excellent electrochemical performance, including high capacity, high rate capability, high stability, and reversibility, and have broad prospects for industrialization. Attached Figure Description

[0028] Figure 1 The figures (a) N2 adsorption-desorption curve and (b) NLDFT model full pore size distribution diagram of the dual-phase high-entropy sodium oxide anode material obtained in Example 1 are derived from the N2 adsorption-desorption curve. Figure 2X-ray diffraction (XRD) structure diagrams of the biphase high-entropy sodium oxide anode materials obtained in Examples 1-4 and Comparative Examples 1, 3, and 4; Figure 3 The first charge-discharge curve at 0.1C is shown for the dual-phase high-entropy sodium oxide anode material obtained in Example 1.

[0029] Figure 4 The graph shows the cycling performance and coulombic efficiency of the dual-phase high-entropy sodium oxide anode material obtained in Example 1 at a 1C rate.

[0030] Figure 5 The image shows the performance of the dual-phase high-entropy sodium oxide anode material obtained in Example 1 at rates of 0.1-2C. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention, but the scope of protection of the present invention is not limited thereto.

[0032] Unless otherwise specified, all raw materials used in the embodiments of the present invention are commercially available materials; unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those skilled in the art.

[0033] In one specific embodiment of the present invention, a high-energy vibratory ball mill, model MH100, is used, with an output voltage of 200-240V, a vibration frequency of 60-2400r / min, a motor power of 400W, a maximum sample feed size of ≤8mm, and a grinding time of 8-10h. Example 1

[0034] (1) Weigh 0.45 mol Na2CO3, 0.1 mol Fe2O3, 0.2 mol NiO, 0.4 mol MnO2, 0.1 mol CuO, 0.05 mol CoO, and 0.05 mol SnO2, mix them, and transfer them to a high-energy vibrating ball mill. Add ethanol as a solvent. The amount of ethanol added is 25% of the total mass of the mixture. Control the ball milling speed of the high-energy vibrating ball mill to 2000 r / min, the ball-to-material weight ratio to 13:1, and the ball milling time to 3 h to obtain the first precursor material.

[0035] (2) 3.5g of the first precursor material was added to 10mL of acetic acid aqueous solution with a concentration of 0.5M, and stirred at 200r / min and 25℃ for 1h. After centrifugation and vacuum drying at 80℃ for 8h, the second precursor material was obtained.

[0036] (3) The second precursor material was subjected to segmented calcination. First, the temperature was increased from room temperature to 900℃ at a rate of 5℃ / min under an argon atmosphere, and the reaction was maintained at 900℃ for 12 hours. Then, the temperature was decreased to room temperature at a rate of 5℃ / min. Next, the temperature was increased to 300℃ at a rate of 3℃ / min under an argon atmosphere, and the reaction was maintained at 300℃ for 5 hours. Finally, the temperature was decreased to room temperature at a rate of 5℃ / min to obtain the sodium-ion battery anode material, named Na. 0.90 Fe 0.2 Ni 0.2 Mn 0.4 Cu 0.1 Co 0.05 Sn 0.05 O2.

[0037] The specific surface area and pore size of the sodium-ion battery anode material obtained in this embodiment were measured using a high-performance specific surface area and pore size analyzer (BSD-660). The test results are shown in [Figure number missing]. Figure 1 ,Depend on Figure 1 It can be seen that the specific surface area and pore size range are 36.8 m². 2 / g, 1-45nm, belonging to a multi-level porous structure of micropores and mesopores; the particle size was measured to be 2μm by a laser particle size analyzer (PSA1190LD).

[0038] The sodium-ion battery anode material obtained in this embodiment was subjected to X-ray diffraction (XRD) structural testing. The test results are shown in [Figure number missing]. Figure 2 ,Depend on Figure 2 It can be seen that the product crystallizes well, and the crystal structure of this material is a P2 / O3 dual-phase structure.

[0039] The sodium-ion battery anode material (Na) obtained in this embodiment is used in this example. 0.90 Fe 0.2 Ni 0.2 Mn 0.4 Cu 0.1 Co 0.05 Sn 0.05 O2 is used as the negative electrode in sodium-ion batteries. The specific method for testing sodium-ion batteries is as follows:

[0040] The obtained sodium-ion battery anode material was mixed with acetylene black, polyvinylidene fluoride (PVDF), and N-methylpyrrolidone (NMP) in a ratio of 8g:1g:1g:30mL. After thorough mixing, the mixture was coated onto a copper foil current collector and vacuum dried at 120℃ for 5 hours. The resulting material was then cut into circular pieces and stored in an inert atmosphere glove box for later use. The cathode was a metallic sodium sheet, the separator was a glass fiber membrane, and the electrolyte was a 1M NaPF6 solution dissolved in a mixture of propylene carbonate and ethylene carbonate (volume ratio 1:1). The resulting CR-2035 coin cells were assembled in a CT-4008-5A6V system. Electrochemical performance tests were conducted at 0.1C for the first charge-discharge cycle, 1C for cycling, and 0.1-2C for high-rate cycling. The test results are shown below. Figure 3 , Figure 4 , Figure 5 .Depend on Figure 3 It can be seen that under the conditions of 0.1C and 2-4.2V, the first charge specific capacity reaches 504.54mAh / g, the first discharge specific capacity reaches 455.70mAh / g, and the first round coulombic efficiency is 90.32%.

[0041] Depend on Figure 4 It can be seen that after 200 cycles at a 1C rate, the capacity retention rate reached 83.26%, indicating long-cycle stability.

[0042] Depend on Figure 5 It can be seen that under high charge-discharge rates of 0.1-2C, the capacities at 0.1C, 0.2C, 0.5C, 1C, and 2C reached 455.72mAh / g, 436.13mAh / g, 408.53mAh / g, 370.38mAh / g, and 330.85mAh / g, respectively. Compared with the 2C discharge rate of 0.1C, the capacity retention rate was 72.60%. When switching from 2C to 0.1C, the capacity reached 434.28mAh / g, and the recovery rate reached 95.30%, indicating that it has good rate performance and highly reversible electrochemical performance. Example 2

[0043] (1) Weigh 0.75 mol NaHCO3, 0.045 mol Fe2O3, 0.31 mol NiO, 0.48 mol MnO2, 0.02 mol CoO and 0.1 mol SnO2, mix them and transfer them to a high-energy vibrating ball mill, and add deionized water as a solvent. The amount of deionized water added is 20% of the total mass of the above mixture. Control the ball milling speed of the high-energy vibrating ball mill to 1000 r / min, the ball-to-material weight ratio to 10:1 and the ball milling time to 1 h to obtain the first precursor material;

[0044] (2) 1g of the first precursor material was added to 10mL of acetic acid aqueous solution with a concentration of 0.1M, and stirred at 100r / min and 20℃ for 2h. After centrifugation and vacuum drying at 60℃ for 12h, the second precursor material was obtained.

[0045] (3) The second precursor material was subjected to segmented calcination. First, the temperature was increased from room temperature to 800°C at a rate of 10°C / min under a nitrogen atmosphere and held for 15 h. Then, the temperature was decreased to room temperature at a rate of 10°C / min. Next, the temperature was increased to 200°C at a rate of 5°C / min under a nitrogen atmosphere and held for 7 h. Finally, the temperature was decreased to room temperature at a rate of 10°C / min to obtain the sodium-ion battery anode material, named Na. 0.75 Fe 0.09 Ni 0.31 Mn 0.48 Cu0Co 0.02 Sn 0.1 O2.

[0046] The specific surface area and pore size of the sodium-ion battery anode material obtained in this embodiment were measured using a high-performance specific surface area and pore size analyzer (BSD-660). The specific surface area and pore size ranges were 30.8 μm. 2 / g, 1-38nm, belongs to the hierarchical porous structure of micropores and mesopores; the particle size was measured to be 2.5μm by a laser particle size analyzer (PSA1190LD).

[0047] The sodium-ion battery anode material obtained in this embodiment was subjected to XRD structure testing, and the test results are shown in [Figure number missing]. Figure 2 ,Depend on Figure 2 It can be seen that the product crystallizes well, and the crystal structure of this material is a P2 / O3 dual-phase structure. The sodium-ion battery anode material (Na2O3) obtained in this embodiment... 0.75 Fe 0.09 Ni 0.31 Mn 0.48 Cu0Co 0.02 Sn 0.1 O2 was used as the negative electrode in sodium-ion batteries. The test method was the same as in Example 1, and the test results are shown in Table 1.

[0048] As shown in Table 1, within the 2.0-4.2V charge / discharge voltage window, the initial discharge specific capacity is 419.15 mAh / g, with a coulombic efficiency of 81.26%, demonstrating long-term cycling stability and high initial coulombic efficiency. After 200 cycles at 1C, the capacity retention rate reaches 79.07%, compared to 70.51% at 0.1C 2C discharge, exhibiting excellent rate performance. When switching from 2C to 0.1C, the capacity recovery rate reaches 92.50%, indicating highly reversible electrochemical performance. Example 3

[0049] (1) Weigh 0.95 mol NaOH, 0.15 mol Fe2O3, 0.1 mol NiO, 0.355 mol MnO2, 0.125 mol CuO, 0.1 mol CoO and 0.02 mol SnO2, mix them and transfer them to a high-energy vibrating ball mill, and add methanol as a solvent. The amount of methanol added is 30% of the total mass of the above mixture. The ball milling speed is 3000 r / min, the ball-to-material weight ratio is 15:1, and the ball milling time is 5h to obtain the first precursor material;

[0050] (2) 6g of the first precursor material was added to 10mL of oxalic acid aqueous solution with a concentration of 1M, and stirred at 300r / min and 30℃ for 0.5h. After centrifugation and vacuum drying at 100℃ for 6h, the second precursor material was obtained.

[0051] (3) The second precursor material was subjected to segmented calcination. First, the temperature was increased to 1100℃ at 3℃ / min under an argon atmosphere and held for 9 hours. Then, the temperature was decreased to room temperature at a rate of 3℃ / min. Next, the temperature was increased to 400℃ at 1℃ / min under a nitrogen atmosphere and held for 3 hours. Finally, the temperature was decreased to room temperature at a rate of 3℃ / min to obtain the sodium-ion battery anode material, named Na. 0.95 Fe 0.3 Ni 0.1 Mn 0.355 Cu 0.125 Co 0.1 Sn 0.02 O2.

[0052] The specific surface area and pore size of the sodium-ion battery anode material obtained in this embodiment were measured using a high-performance specific surface area and pore size analyzer (BSD-660). The specific surface area and pore size ranges were 35.4 μm. 2 / g, 1-43nm, belongs to the hierarchical porous structure of micropores and mesopores; the particle size was measured to be 1.0μm by a laser particle size analyzer (PSA1190LD).

[0053] The sodium-ion battery anode material obtained in this embodiment was subjected to XRD structure testing, and the test results are shown in [Figure number missing]. Figure 2 ,Depend on Figure 2 It can be seen that the product crystallizes well, and the crystal structure of this material is a P2 / O3 dual-phase structure.

[0054] The sodium-ion battery anode material (Na) obtained in this embodiment is used in this example. 0.95 Fe 0.3 Ni 0.1 Mn 0.355 Cu 0.125 Co 0.1 Sn0.02 O2 was used as the negative electrode in sodium-ion batteries. The test method was the same as in Example 1, and the test results are shown in Table 1.

[0055] As shown in Table 1, within the 2.0-4.2V charge / discharge voltage window, the initial discharge specific capacity is 447.71 mAh / g, and the coulombic efficiency reaches 85.72%, demonstrating long-term cycling stability and high initial coulombic efficiency. After 200 cycles at 1C, the capacity retention rate reaches 82.73%, compared to 72.60% at 0.1C, exhibiting excellent rate performance. When switching from 2C to 0.1C, the capacity recovery rate reaches 94.74%, indicating highly reversible electrochemical performance. Example 4

[0056] (1) Weigh 0.9 mol CH3COONa, 0.1 mol Fe2O3, 0.2 mol NiO, 0.3 mol MnO2, 0.1 mol Al2O3, 0.05 mol CoO, and 0.05 mol SnO2, mix them, and then transfer them to a high-energy vibrating ball mill. Add ethanol as a solvent. The amount of ethanol added is 27% of the total mass of the above mixture. The ball milling speed is 2000 r / min, the ball-to-material weight ratio is 13:1, and the ball milling time is 3h to obtain the first precursor material.

[0057] (2) Add 5g of the first precursor material to 10mL of acetic acid aqueous solution with a concentration of 0.15M, stir and react for 2h at a speed of 200r / min and 20℃, centrifuge and vacuum dry at 90℃ for 10h to obtain the second precursor material;

[0058] (3) The second precursor material was subjected to segmented calcination. First, the temperature was increased to 850°C at 8°C / min under an argon atmosphere and held for 10 h. Then, the temperature was decreased to room temperature at a rate of 8°C / min. Next, the temperature was increased to 250°C at 4°C / min under a nitrogen atmosphere and held for 4 h. Finally, the temperature was decreased to room temperature at a rate of 8°C / min to obtain the sodium-ion battery anode material, named Na. 0.90 Fe 0.2 Ni 0.2 Mn 0.3 Al 0.2 Co 0.05 Sn 0.05 O2.

[0059] The specific surface area and pore size of the sodium-ion battery anode material obtained in this embodiment were measured using a high-performance specific surface area and pore size analyzer (BSD-660). The specific surface area and pore size ranges were 29.7 μm. 2 / g, 1-37nm, belongs to the hierarchical porous structure of micropores and mesopores; the particle size was measured to be 2.2μm by a laser particle size analyzer (PSA1190LD).

[0060] The sodium-ion battery anode material obtained in this embodiment was subjected to XRD structure testing, and the test results are shown in [Figure number missing]. Figure 2 ,Depend on Figure 2 It can be seen that the product crystallizes well, and the crystal structure of this material is a P2 / O3 dual-phase structure.

[0061] The sodium-ion battery anode material (Na) obtained in this embodiment is used in this example. 0.90 Fe 0.2 Ni 0.2 Mn 0.3 Al 0.2 Co 0.05 Sn 0.05 O2 was used as the negative electrode in sodium-ion batteries. The test method was the same as in Example 1, and the test results are shown in Table 1.

[0062] As shown in Table 1, within the 2.0-4.2V charge / discharge voltage window, the initial discharge specific capacity is 416.24 mAh / g, with a coulombic efficiency of 80.75%, demonstrating long-term cycling stability and high initial coulombic efficiency. After 200 cycles at 1C, the capacity retention rate reaches 77.55%, compared to 68.59% at 0.1C 2C discharge, exhibiting excellent rate performance. When switching from 2C to 0.1C, the capacity recovery rate reaches 91.08%, indicating highly reversible electrochemical performance. Comparative Example 1

[0063] The difference between Comparative Example 1 and Example 1 is that the amount of sodium source used in step (1) is different. 0.45 mol Na2CO3 is replaced with 0.5 mol Na2CO3, while the other steps remain unchanged, and sodium-ion battery anode material is obtained.

[0064] The obtained sodium-ion battery anode material was subjected to XRD structure testing, and the test results are shown in the figure. Figure 2 ,Depend on Figure 2 It can be seen that the crystal structure of this material is the O3 phase, with no diffraction peaks for other phases. Therefore, when the molar ratio of sodium source exceeds 0.95, the O3 single phase will appear, and the amount of sodium source should be properly controlled.

[0065] The obtained sodium-ion battery anode material was used as the anode in a sodium-ion battery and tested using the same method as in Example 1. The test results are shown in Table 1.

[0066] As shown in Table 1, within the 2.0-4.2V charge / discharge voltage window, the first-cycle discharge specific capacity is 369.18 mAh / g, the coulombic efficiency is 72.53%, and the capacity retention rate after 200 cycles at 1C is 66.70%. Compared to the 61.40% capacity retention rate at 2C discharge (0.1C), and the 84.42% capacity recovery rate when switching from 2C to 0.1C, the discharge specific capacity, first-cycle coulombic efficiency, cycle stability, rate performance, and reversibility are far lower than those of Example 1. This indicates that the single-phase structure is prone to harmful phase transitions, leading to material structural damage and performance degradation. Comparative Example 2

[0067] The difference between Comparative Example 2 and Example 2 lies in the different ball milling apparatus in step (1). The high-energy vibration ball milling apparatus is replaced with a traditional ball mill (drum ball mill, model M373802). The ball milling conditions of the traditional ball milling apparatus are a ball milling speed of 1000 r / min, a ball-to-material weight ratio of 10:1, and a ball milling time of 1 h. Other steps remain unchanged, and sodium-ion battery anode material is obtained.

[0068] The specific surface area and pore size of the obtained sodium-ion battery anode material were measured using a high-performance specific surface area and pore size analyzer (BSD-660). The specific surface area and pore size ranges were 26.0 μm. 2 The particle size is 2-38 nm, belonging to the mesoporous pore structure; the particle size was measured to be 8 μm by a laser particle size analyzer (PSA1190LD).

[0069] The obtained sodium-ion battery anode material was used as the anode in a sodium-ion battery and tested using the same method as in Example 1. The test results are shown in Table 1.

[0070] As shown in Table 1, within the 2.0-4.2V charge / discharge voltage window, the initial discharge specific capacity is 325.14 mAh / g, the coulombic efficiency is 65.08%, and the capacity retention rate after 200 cycles at 1C is 58.48%. Compared to the 55.31% capacity retention rate at 0.1C and the 81.13% capacity recovery rate when switching from 2C to 0.1C, the discharge specific capacity, initial coulombic efficiency, cycle stability, rate performance, and reversibility are significantly lower than in Example 2. This indicates that the product obtained using a conventional ball mill has a larger particle size and a smaller pore size range. Larger particle sizes reduce the surface area of ​​the electrode material, thus reducing the contact area with the electrolyte, meaning fewer active sites for electrochemical reactions, leading to a decrease in battery discharge capacity. A smaller pore size range is also detrimental to Na+. + Intercalation and deintercalation of particles and electrolyte penetration lead to a decrease in battery capacity. Furthermore, larger particles are more prone to volume changes during battery charging and discharging, resulting in increased interparticle stress, which accelerates particle decomposition and detachment, ultimately shortening the battery's cycle life. Comparative Example 3

[0071] The difference between Comparative Example 3 and Example 1 is that there is no two-stage calcination in step (3). The calcination conditions are: heating from room temperature to 900°C at 5°C / min under an argon atmosphere, holding at 900°C for 12 hours, and then cooling to room temperature at a rate of 5°C / min. Other steps remain unchanged to obtain sodium-ion battery anode material.

[0072] The sodium-ion battery anode material obtained in this embodiment was subjected to XRD structure testing, and the test results are shown in [Figure number missing]. Figure 2 ,Depend on Figure 2 It can be seen that the weak peak intensity indicates poor product crystallization, but the crystal structure of this material is still a P2 / O3 dual-phase structure.

[0073] The obtained sodium-ion battery anode material was used as the anode in a sodium-ion battery and tested using the same method as in Example 1. The test results are shown in Table 1.

[0074] As shown in Table 1, within the 2.0-4.2V charge / discharge voltage window, the first-cycle discharge specific capacity is 361.25 mAh / g, the coulombic efficiency is 74.52%, and the capacity retention rate after 200 cycles at 1C is 63.26%. Compared to the 64.33% capacity retention rate at 2C discharge (0.1C), and the 89.82% capacity recovery rate when switching from 2C to 0.1C, the discharge specific capacity, first-cycle coulombic efficiency, cycle stability, rate performance, and reversibility are far lower than those of Example 1. This indicates that the single-stage calcination method is prone to causing local overheating or uneven heating, affecting the uniformity and stability of the product, thus resulting in poor electrochemical performance. Comparative Example 4

[0075] The difference between Comparative Example 4 and Example 1 is that the amount of sodium source used in step (1) is different. 0.45 mol Na2CO3 is replaced with 0.35 mol Na2CO3, while the other steps remain unchanged, and sodium-ion battery anode material is obtained.

[0076] The obtained sodium-ion battery anode material was subjected to XRD structure testing, and the test results are shown in the figure. Figure 2 ,Depend on Figure 2 It can be seen that the crystal structure of this material is a P2 phase, with no diffraction peaks for other phases. Therefore, a single P2 phase will appear when the molar ratio of sodium source is below 0.75, and the amount of sodium source should be appropriately controlled.

[0077] The obtained sodium-ion battery anode material was used as the anode in a sodium-ion battery and tested using the same method as in Example 1. The test results are shown in Table 1.

[0078] As shown in Table 1, within the 2.0-4.2V charge / discharge voltage window, the first-cycle discharge specific capacity is 349.53 mAh / g, the coulombic efficiency is 79.57%, and the capacity retention rate after 200 cycles at 1C is 75.75%. Compared to the 65.41% capacity retention rate at 0.1C and the 86.57% capacity recovery rate when switching from 2C to 0.1C, the discharge specific capacity, first-cycle coulombic efficiency, cycle stability, rate performance, and reversibility are far lower than those of Example 1. This indicates that the single-phase structure is prone to harmful phase transitions, leading to material structure damage and performance degradation. Comparative Example 5

[0079] The difference between Comparative Example 5 and Example 1 is that the cooling rate during the segmented calcination in step (3) is different. The cooling rate of 5℃ / min to room temperature is changed to natural cooling to room temperature, while other factors remain unchanged, and sodium-ion battery anode material is obtained.

[0080] The obtained sodium-ion battery anode material was used as the anode in a sodium-ion battery and tested using the same method as in Example 1. The test results are shown in Table 1.

[0081] As shown in Table 1, within the 2.0-4.2V charge / discharge voltage window, the first-cycle discharge specific capacity is 369.50 mAh / g, the coulombic efficiency reaches 78.26%, and the capacity retention rate after 200 cycles at 1C rate reaches 74.31%. Compared with the 64.51% capacity retention rate at 0.1C and 86.06% when switching from 2C to 0.1C, the discharge specific capacity, first-cycle coulombic efficiency, cycle stability, rate performance, and reversibility are far lower than those of Example 1. This indicates that the internal stress or phase transition of the sodium-ion battery anode material caused by rapid cooling leads to the collapse of the material structure, resulting in poor material performance. Comparative Example 6

[0082] The difference between Comparative Example 6 and Example 1 is that the organic acid solution treatment in step (2) is omitted, while the other steps remain unchanged, resulting in a sodium-ion battery anode material.

[0083] The specific surface area and pore size of the obtained sodium-ion battery anode material were measured using a high-performance specific surface area and pore size analyzer (BSD-660). The specific surface area and pore size ranges were 19.3 μm. 2 / g, 2-25nm, belongs to the mesoporous pore structure.

[0084] The obtained sodium-ion battery anode material was used as the anode in a sodium-ion battery and tested using the same method as in Example 1. The test results are shown in Table 1.

[0085] As shown in Table 1, within the 2.0-4.2V charge / discharge voltage window, the first-cycle discharge specific capacity is 332.56 mAh / g, the coulombic efficiency reaches 74.23%, and the capacity retention rate after 200 cycles at 1C rate reaches 70.24%. Compared with the 62.49% capacity retention rate at 0.1C and 83.72% capacity recovery rate when switching from 2C to 0.1C, the discharge specific capacity, first-cycle coulombic efficiency, cycle stability, rate performance, and reversibility are much lower than those of Example 1. This indicates that the treatment with organic acid solution increases the specific surface area and pore size range of the material, and the specific surface area and pore size range affect battery performance. Comparative Example 7

[0086] The difference between Comparative Example 7 and Example 1 is that step (2) includes the addition of deionized water and ethanol washing steps, while other steps remain unchanged, to obtain sodium-ion battery anode material. The specific operation of step (2) is as follows: 3.5g of the first precursor material is added to 10mL of acetic acid aqueous solution with a concentration of 0.5M, and stirred at 200r / min and 25℃ for 1h. After the reaction is completed, the mixture is centrifuged, washed three times with deionized water and ethanol respectively, and vacuum dried at 80℃ for 8h to obtain the second precursor material.

[0087] The specific surface area and pore size of the obtained sodium-ion battery anode material were measured using a high-performance specific surface area and pore size analyzer (BSD-660). The specific surface area and pore size ranges were 30.3 μm. 2 / g, 2-37nm, belongs to the mesoporous pore structure.

[0088] As shown in Table 1, within the 2.0-4.2V charge / discharge voltage window, the first-cycle discharge specific capacity is 392.92 mAh / g, the coulombic efficiency reaches 82.80%, and the capacity retention rate after 200 cycles at 1C rate reaches 77.09%. Compared with the 68.51% capacity retention rate at 0.1C 2C discharge, the capacity recovery rate reaches 87.08% when switching from 2C to 0.1C. The discharge specific capacity, first-cycle coulombic efficiency, cycle stability, rate performance, and reversibility are much lower than those of Example 1, indicating that the CO2 generated by the residual organic acid during calcination will increase the specific surface area and pore size range of the material. The specific surface area and pore size range will affect the battery performance. Comparative Example 8

[0089] The difference between Comparative Example 8 and Example 1 is that no solvent is added in step (1), while the other steps remain unchanged, resulting in a sodium-ion battery anode material.

[0090] The specific surface area and pore size of the obtained sodium-ion battery anode material were measured using a high-performance specific surface area and pore size analyzer (BSD-660). The specific surface area and pore size ranges were 28.0 μm. 2 / g, 2-40nm, belongs to the mesoporous pore structure; the particle size was measured to be 6μm by a laser particle size analyzer (PSA1190LD).

[0091] The obtained sodium-ion battery anode material was used as the anode in a sodium-ion battery and tested using the same method as in Example 1. The test results are shown in Table 1.

[0092] As shown in Table 1, within the 2.0-4.2V charge / discharge voltage window, the initial discharge specific capacity is 335.83 mAh / g, the coulombic efficiency is 66.33%, and the capacity retention rate after 200 cycles at 1C is 58.82%. Compared to the 55.70% capacity retention rate at 0.1C and the 81.55% capacity recovery rate when switching from 2C to 0.1C, the discharge specific capacity, initial coulombic efficiency, cycle stability, rate performance, and reversibility are significantly lower than in Example 1. This indicates that the product obtained by dry ball milling has a larger particle size and a smaller pore size range. Larger particle sizes reduce the surface area of ​​the electrode material, thus reducing the contact area with the electrolyte, meaning fewer active sites for electrochemical reactions, leading to a decrease in battery discharge capacity. A smaller pore size range is unfavorable for Na... + Intercalation and deintercalation of particles and electrolyte penetration lead to a decrease in battery capacity. Furthermore, larger particles are more prone to volume changes during battery charging and discharging, resulting in increased interparticle stress, which accelerates particle decomposition and detachment, ultimately shortening the battery's cycle life. Comparative Example 9

[0093] The difference between Comparative Example 9 and Example 1 is that SnO2 was not added in step (1) and organic acid solution treatment was not performed in step (2). Other steps remained unchanged, and sodium-ion battery anode material was obtained.

[0094] The specific surface area and pore size of the obtained sodium-ion battery anode material were measured using a high-performance specific surface area and pore size analyzer (BSD-660). The specific surface area and pore size ranges were 19.0 μm. 2 / g, 2-23nm, belongs to the mesoporous pore structure.

[0095] The obtained sodium-ion battery anode material was used as the anode in a sodium-ion battery and tested using the same method as in Example 1. The test results are shown in Table 1.

[0096] As shown in Table 1, within the 2.0-4.2V charge / discharge voltage window, the first-cycle discharge specific capacity is 322.80 mAh / g, the coulombic efficiency reaches 70.52%, and the capacity retention rate after 200 cycles at 1C rate reaches 67.53%, compared to 58.49% at 0.1C 2C discharge. When switching from 2C to 0.1C, the capacity recovery rate reaches 79.46%. The discharge specific capacity, first-cycle coulombic efficiency, cycle stability, rate performance, and reversibility are far lower than those of Example 1 and Comparative Example 6, indicating that the multi-element effect of high-entropy materials affects the battery performance and has a synergistic effect with the hierarchical porous structure and high specific surface area obtained after organic acid solution treatment, jointly affecting the battery performance. Comparative Example 10

[0097] The difference between Comparative Example 10 and Example 1 lies in the different ball-to-material weight ratio and ball milling time in step (1). The ball-to-material weight ratio was adjusted to 20:1 and the ball milling time was adjusted to 10h, while other parameters remained unchanged, to obtain sodium-ion battery anode material.

[0098] The specific surface area and pore size of the obtained sodium-ion battery anode material were measured using a high-performance specific surface area and pore size analyzer (BSD-660). The specific surface area and pore size ranges were 41.8 μm. 2 / g, 1-45nm, belonging to a hierarchical porous structure of micropores and mesopores; the particle size was measured to be 0.5μm by a laser particle size analyzer (PSA1190LD).

[0099] The obtained sodium-ion battery anode material was used as the anode in a sodium-ion battery and tested using the same method as in Example 1. The test results are shown in Table 1.

[0100] As shown in Table 1, within the 2.0-4.2V charge / discharge voltage window, the first-cycle discharge specific capacity is 458.50 mAh / g, the coulombic efficiency is 90.05%, and the capacity retention rate after 200 cycles at 1C is 70.5%. Compared to the 52.45% capacity retention rate at 0.1C and the 80.3% capacity recovery rate when switching from 2C to 0.1C, the cycle stability, rate performance, and reversibility are far lower than in Example 1. This indicates that increasing the ball-to-material weight ratio and extending the ball milling time will affect the particle size. However, the smaller the particle size, the lower the cycle stability, rate performance, and reversibility are compared to Example 1. This may be because small particles of sodium-ion battery anode material agglomerate or detach during charge and discharge, leading to a reduction in active material and a decrease in cycle stability, rate performance, and reversibility. Combined with Comparative Example 8, it can be seen that particle size is one of the key factors affecting sodium-ion battery anode materials, namely, the ball-to-material weight ratio and ball milling time have a significant impact.

[0101] Table 1. Cyclic stability tests of Examples 1-4 and Comparative Examples 1-9 at 1C and high-rate tests at 0.1-2C.

[0102]

[0103] Comparing Comparative Examples 1 and 4 with Example 1, it is evident that when the molar ratio of sodium source exceeds 0.95 or falls below 0.75, a single-phase structure of O3 or P2 is formed. This single-phase structure is prone to harmful phase transitions during electrochemical testing, leading to material structure damage and performance degradation, resulting in battery performance far lower than that of a two-phase structure. Comparing Comparative Examples 2, 8, and 10 with Examples 1-2, it is clear that both excessively large and small particle sizes affect battery performance. Using traditional ball mills or solvent-free dry ball milling results in larger particle sizes, leading to a reduction in the pore size range and specific surface area after organic acid post-treatment, thus causing a decrease in battery performance. This is mainly due to two reasons: firstly, larger particle sizes reduce the surface area of ​​the electrode material, thus reducing the contact area with the electrolyte, meaning fewer active sites participate in the electrochemical reaction, resulting in a lower battery discharge capacity; secondly, a smaller pore size range is unfavorable for Na… + The deintercalation and electrolyte penetration of the electrolyte lead to a decrease in battery capacity, resulting in a performance degradation. This embodiment employs high-energy vibration ball milling technology, using high-frequency vibration to generate intense impact, friction, and shear forces between the grinding beads and the material, obtaining ultra-fine battery materials. After particle size reduction, the specific surface area of ​​the battery material increases, increasing the number of active sites and shortening the Na+ ionization time. +Transport pathways within the material. Comparing Comparative Example 3 with Example 1, it is evident that single-stage calcination leads to poor crystallinity, resulting in decreased battery performance. A two-stage calcination process improves heating uniformity and stabilizes the material structure, yielding a P2 / O3 dual-phase structure that combines the advantages of both P2 and O3 phases, allowing for mutual support and stability. Comparing Comparative Example 5 with Example 1, it is clear that rapid cooling can cause internal stress or phase transitions, leading to structural collapse and poor electrochemical performance. Therefore, it is crucial to appropriately control the cooling rate. Comparing Comparative Examples 6 and 7 with Example 1, it is evident that organic acid solutions and residual organic acids affect the specific surface area and pore size range of the material. Post-treatment of the organic acid solution and the absence of a rinsing step are key factors in obtaining a high specific surface area and a wide pore size range. Comparing Comparative Example 9 with Example 1, it is evident that the multi-element effect of high-entropy materials influences battery performance and has a synergistic effect with the hierarchical porous structure and high specific surface area obtained after organic acid solution treatment, jointly impacting battery performance. Furthermore, the synergistic effect of multiple elements during charge and discharge accelerates the rapid transport and insertion / extraction of sodium ions. Therefore, the dual-phase high-entropy oxide sodium anode material exhibits superior electrochemical performance, far exceeding that of materials prepared by single-phase structures, traditional ball milling, and single-stage calcination methods.

[0104] The above embodiments are intended to illustrate the essential content of the present invention, but are not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of protection of the present invention.

Claims

1. A dual-phase high-entropy sodium oxide anode material, characterized in that, The chemical formula of the high-entropy oxide is Na. x Fe y Ni z Mn a M b Co c Sn d O2, wherein 0.75≤x≤0.95, 0.09≤y≤0.30, 0.10≤z≤0.31, 0.30≤a≤0.48, 0≤b≤0.2, 0.02≤c≤0.1, 0.02≤d≤0.1, y+z+a+b+c+d=1, and M is Cu or Al; the dual-phase high-entropy oxide sodium electrode anode material has a P2 / O3 dual-phase structure; the particle size is 1-2.5μm, and the specific surface area is 29.7-36.8m². 2 / g, with a pore size of 1-45nm; it has a hierarchical pore structure of micropores and mesopores.

2. The method for preparing the dual-phase high-entropy sodium oxide anode material according to claim 1, characterized in that, Includes the following steps: (1) Sodium source, ferric oxide, nickel oxide, manganese dioxide, oxide of M, cobalt oxide and tin oxide are mixed according to Na x Fe y Ni z Mn a M b Co c Sn d Weigh out the molar ratios of each component in the chemical formula of O2, mix them, add solvent, and perform wet ball milling to obtain the first precursor material. (2) The first precursor material obtained in step (1) is stirred and reacted in an organic acid solution, and then centrifuged and vacuum dried to obtain the second precursor material; (3) The second precursor material obtained in step (2) is calcined in stages under the protective atmosphere of argon or nitrogen to obtain a two-phase high-entropy sodium oxide anode material. In step (1), a high-energy vibration ball mill is used for wet ball milling. The wet ball milling conditions are: ball mill speed ≥ 1000 r / min, ball-to-material weight ratio 10-15:1, and ball milling time 1-5h. In step (3), the segmented roasting is a first-stage high-temperature roasting with the following conditions: heating rate 3-10℃ / min, temperature 800-1100℃, holding reaction time 9-15h, cooling rate 3-10℃ / min, and temperature reduced to room temperature; the second-stage low-temperature roasting conditions are: heating rate 1-5℃ / min, temperature 200-400℃, holding reaction time 3-7h, cooling rate 3-10℃ / min, and temperature reduced to room temperature.

3. The method for preparing the dual-phase high-entropy sodium oxide anode material according to claim 2, characterized in that, In step (1), the sodium source is one of sodium carbonate, sodium bicarbonate, sodium hydroxide, and sodium acetate; the oxide of M is copper oxide or aluminum oxide.

4. The method for preparing the dual-phase high-entropy sodium oxide anode material according to claim 2, characterized in that, In step (1), the solvent is one of deionized water, ethanol, and methanol; the amount of solvent used is 20-30% of the total mass of sodium source, ferric oxide, nickel oxide, manganese dioxide, oxide of M, cobalt oxide, and tin oxide.

5. The method for preparing the dual-phase high-entropy sodium oxide anode material according to claim 2, characterized in that, In step (2), the organic acid solution is an aqueous solution of acetic acid or an aqueous solution of oxalic acid; the concentration of the organic acid solution is 0.1-1M.

6. The method for preparing the dual-phase high-entropy sodium oxide anode material according to claim 2, characterized in that, In step (2), the mass-to-volume ratio of the first precursor material to the organic acid solution is 1-6 g: 10 mL.

7. The method for preparing the dual-phase high-entropy sodium oxide anode material according to claim 2, characterized in that, In step (2), the stirring reaction conditions are: stirring speed of 100-300 r / min, temperature of 20-30℃, and time of 0.5-2 h; the vacuum drying conditions are: temperature of 60-100℃ and drying time of 6-12 h.

8. The application of the dual-phase high-entropy oxide sodium anode material as described in claim 1, characterized in that, The dual-phase high-entropy oxide sodium electrode material is applied to the anode of sodium-ion batteries.

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