Medium-entropy sodium ion battery positive electrode material and preparation method thereof
By constructing a medium-entropy sodium-ion battery cathode material NaxFeaMnbMcO2 and employing entropy regulation and Cu/Mg co-doping, the problems of low specific capacity, insufficient rate performance, and poor cycle stability of layered transition metal oxide sodium-ion batteries were solved, enabling stable applications at high energy density and high current density.
Patent Information
- Application Number
- CN202511195836.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-26
- Publication Date
- 2025-11-28
AI Technical Summary
Existing layered transition metal oxide sodium-ion batteries suffer from low specific capacity, insufficient rate performance, and poor cycle stability, which limits their application at high energy density and high current density.
By constructing a medium-entropy sodium-ion battery cathode material NaxFeaMnbMcO2, entropy regulation and transition metal element synthesis were employed to optimize the crystal plane ratio and perform Cu and Mg co-doping, thereby improving the structural stability and electrochemical performance of the material.
It significantly improves the rate performance and cycle life of sodium-ion batteries, extends the structural stability of materials during charge and discharge, and maintains high specific capacity and electrochemical performance.
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Figure CN121035178A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of sodium ion batteries, and particularly relates to a medium-entropy sodium ion battery positive electrode material and a preparation method thereof. BACKGROUND
[0002] In recent years, sodium ion batteries have shown broad application prospects in energy storage and network electronics due to their abundant resources, low cost, high safety, and good electrochemical performance. Currently, the positive electrode materials of sodium ion batteries are mainly divided into three categories: layered transition metal oxides, polyanion compounds, and prussian blue compounds. Among them, layered oxides are considered to be the most commercially potential positive electrode material because of their high energy density, high voltage platform, excellent rate performance, and simple synthesis process.
[0003] However, in practical applications, layered transition metal oxides still face the following key challenges:
[0004] (1) Low specific capacity: Compared with lithium ion batteries, the specific capacity of sodium ion batteries is lower, which makes it difficult to provide enough energy under the same mass or volume, limiting its application in high energy density demand scenarios.
[0005] (2) Poor rate performance: Under high current density (such as 1000 mA / g), the material is prone to crystal structure damage and voltage decay, leading to rapid capacity decline and poor charge-discharge stability.
[0006] (2) Poor cycle stability: Sodium ions are prone to interlayer slip and irreversible phase transition during intercalation / deintercalation, causing material structure degradation, which in turn leads to rapid capacity decay, low coulombic efficiency, and short cycle life.
[0007] Therefore, how to optimize the crystal structure stability and electrochemical performance of layered transition metal oxides through material design to improve their rate performance and cycle life is the key to promoting the commercialization process of sodium ion batteries. SUMMARY
[0008] To solve the above technical problems, the application provides a P2-phase medium-entropy sodium ion battery positive electrode material and a preparation method thereof. By adjusting the entropy value of layered transition metal oxides, a medium-entropy material is constructed to reasonably control the crystal plane ratio, ultimately improving the structural stability (phase transition) and enhancing the electrochemical performance. In addition, by selecting appropriate transition metal elements to synthesize the material, a medium-entropy layered composite metal oxide positive electrode material is formed, which has higher phase transition resistance compared to high-entropy materials and better cycle life compared to low-entropy materials.
[0009] The first object of the application is to provide a medium-entropy sodium ion battery positive electrode material, the chemical formula of which is Na xFe a Mn b M c O2; wherein M is Cu, Zn, Ni, Cr, Co, Ti, Sn and Mg, 0.5≤x≤1, 0.2≤a≤0.5, 0.3≤b≤0.8, 0<c≤0.2, a+b+c=1, the values of x, a, b, c satisfy the charge balance of the chemical formula.
[0010] A second object of the present application is to provide a preparation method of the medium-entropy sodium-ion battery positive electrode material, comprising the following steps: mixing a sodium source, an iron source, a manganese source, a copper source and a magnesium source according to the stoichiometric ratio, and obtaining the medium-entropy sodium-ion battery positive electrode material through ball milling, tabletting and calcination.
[0011] In an embodiment of the present application, the sodium source is selected from one or more of sodium carbonate, sodium chloride, sodium fluoride, sodium nitrate and sodium acetate.
[0012] In an embodiment of the present application, the iron source is selected from one or more of diiron trioxide, ferrous oxide, ferrous carbonate, ferrous nitrate, iron acetate and iron chloride.
[0013] In an embodiment of the present application, the manganese source is selected from one or more of manganese dioxide, dimanganese trioxide, manganese carbonate, manganese sulfate and manganese nitrate.
[0014] In an embodiment of the present application, the copper source is selected from one or more of copper oxide, copper acetate, copper sulfate, copper nitrate and copper chloride.
[0015] In an embodiment of the present application, the magnesium source is selected from one or more of magnesium oxide, magnesium carbonate, magnesium sulfate, magnesium acetate and magnesium chloride.
[0016] In an embodiment of the present application, the rotation speed of the ball milling is 200r / min-600r / min, and the time is 2h-8h.
[0017] In an embodiment of the present application, the pressure of the tabletting is 9.8MPa-10.2MPa; and the thickness of the material after tabletting is 4.8mm-5.2mm, and the diameter is 12mm-14mm.
[0018] In an embodiment of the present application, the temperature of the calcination is 500℃-1000℃, and the time is 8h-12h.
[0019] The technical solution of the present application has the following advantages compared with the prior art:
[0020] (1) The medium-entropy sodium ion battery positive electrode material described in the application optimizes the crystal face structure through entropy regulation, so that the (010) crystal face ratio is higher than that of low-entropy materials to accelerate the sodium ion transmission rate and improve the rate performance, and the (001) crystal face ratio is higher than that of high-entropy materials to delay the phase change process, slow down the phase change degree and enhance the structural stability; further, Cu and Mg are co-doped, wherein the high electronegativity Cu forms a strong covalent bond with oxygen, and Mg acts as a support, both of which synergistically improve the structural stability, energy density and cycle life of the material; finally, through the synergistic effect of entropy regulation and double metal doping, the crystal structure is highly stable in the charging and discharging process, the cycle life is significantly prolonged, and the specific capacity and excellent rate performance are maintained, which shows good practical application potential.
[0021] (2) The preparation method described in the application can significantly improve the structural stability and electrochemical performance of sodium ion batteries by adjusting the types and proportions of metal oxide raw materials in the positive electrode material; on this basis, further selecting metals with different characteristics for entropy value regulation helps to expand the practical scenarios of sodium ion batteries in commercial applications. BRIEF DESCRIPTION OF DRAWINGS
[0022] In order to make the content of the application more easily understood, the application will be further described in detail below according to specific embodiments of the application and in conjunction with the drawings, in which:
[0023] Figure 1 SEM images of the sodium ion battery positive electrode materials prepared for the application example 1 and the comparative examples 1-2;
[0024] Figure 2 X-ray energy spectrum analysis images of the sodium ion battery positive electrode materials prepared for the application example 1 and the comparative examples 1-2;
[0025] Figure 3 XPS test images of the sodium ion battery positive electrode materials prepared for the application example 1 and the comparative examples 2-4;
[0026] Figure 4 X-ray diffraction images of the sodium ion batteries prepared for the application example 1 and the comparative examples 1-2;
[0027] Figure 5 The first cycle electrochemical curves of the sodium ion batteries prepared for the application example 1 and the comparative example 2 at 0.2C;
[0028] Figure 6 Cycle performance graphs of the sodium ion batteries prepared for the application example 1 and the comparative example 2 at 0.2C;
[0029] Figure 7Rate capability plots of sodium-ion batteries prepared for Inventive Example 1 and Comparative Example 2 at 0.1C-8C;
[0030] Figure 8 Cycle performance plots and first six cycles dQ / dV plots of sodium-ion batteries prepared for Inventive Example 1 and Comparative Examples 2-4 at 0.1C. DETAILED DESCRIPTION
[0031] The present application will be further described with reference to the drawings and specific examples, so that those skilled in the art can better understand the present application and implement it.
[0032] Example 1
[0033] The medium-entropy sodium-ion battery cathode material Na 0.67 Fe 0.2 Mn 0.65 Cu 0.12 Mg 0.03 O2(NFMCM) and a preparation method thereof, specifically comprising the following steps:
[0034] S1, Na2CO3, Fe2O3, MnO2, CuO and MgO are weighed according to the stoichiometric ratio, and after being fully ground with a mortar and pestle, the powders are mixed with zirconia grinding balls and 10 mL of ethanol is added to obtain a precursor;
[0035] S2, the precursor is placed in a ball mill jar and ball milled in a planetary ball mill at a speed of 400 r / min for 8 h, and then dried at 80°C for 12 h to obtain a uniformly mixed powder;
[0036] S3, the mixed powder is scraped off and ground, and then a powder tablet press is used to press it into a circular tablet with a diameter of 13 mm under a pressure of 10 MPa;
[0037] S4, the circular tablet is first calcined in a muffle furnace at 900°C for 8 h under an air atmosphere, and after calcination, a quenching treatment is carried out immediately, and after complete cooling, it is fully ground and stored in an argon-filled glove box to avoid moisture and air pollution, to obtain the medium-entropy sodium-ion battery cathode material Na 0.67 Fe 0.2 Mn 0.65 Cu 0.12 Mg 0.03 O2(NFMCM).
[0038] Comparative Example 1
[0039] The high-entropy sodium-ion battery cathode material Na 0.67 Fe 0.2 Mn 0.5 Cu0.12 Mg 0.03 Ti 0.10 Zn 0.05 O2(NFMCMTZ) and a preparation method thereof, specifically comprising the following steps:
[0040] S1, Na2CO3, Fe2O3, MnO2, CuO, MgO, TiO2 and ZnO are weighed according to the stoichiometric ratio, and then are fully ground with a mortar and pestle, and then the powders are mixed with zirconia grinding balls and 10 mL of ethanol is added to obtain a precursor;
[0041] S2, the precursor is placed in a ball mill jar and ball milled in a planetary ball mill at a speed of 400 r / min for 8 h, and then dried at 80°C for 12 h to obtain a uniformly mixed mixed powder;
[0042] S3, the mixed powder is scraped off and ground, and then a powder tablet press is used to press into a circular tablet with a diameter of 13 mm under a pressure of 10 MPa;
[0043] S4, the circular tablet is first calcined in a muffle furnace at 900°C for 8 h under an air atmosphere, and then is quickly transferred for quenching treatment, and after complete cooling, is fully ground and stored in an argon-filled glove box to avoid moisture and air pollution, to obtain a high-entropy sodium-ion battery positive electrode material Na 0.67 Fe 0.2 Mn 0.5 Cu 0.12 Mg 0.03 Ti 0.10 Zn 0.05 O2(NFMCMTZ).
[0044] Comparative Example 2
[0045] The low-entropy sodium-ion battery positive electrode material Na 0.67 Fe 0.5 Mn 0.5 O2(NFM) and a preparation method thereof, specifically comprising the following steps:
[0046] S1, Na2CO3, Fe2O3 and MnO2 are weighed according to the stoichiometric ratio, and then are fully ground with a mortar and pestle, and then the powders are mixed with zirconia grinding balls and 10 mL of ethanol is added to obtain a precursor;
[0047] S2, the precursor is placed in a ball mill jar and ball milled in a planetary ball mill at a speed of 400 r / min for 8 h, and then dried at 80°C for 12 h to obtain a uniformly mixed mixed powder;
[0048] S3, the mixed powder is scraped off and ground, and then a powder tablet press is used to press into a circular tablet with a diameter of 13 mm under a pressure of 10 MPa;
[0049] S4, the wafer is calcined at 900℃ for 8h in a muffle furnace under air atmosphere, and then is quickly transferred for quenching treatment. After complete cooling, it is fully ground and stored in an argon-filled glove box to avoid moisture and air pollution, to obtain the low-entropy sodium-ion battery cathode material Na 0.67 Fe 0.5 Mn 0.5 O2(NFM) and a preparation method thereof, specifically comprising the following steps:
[0050] Comparative Example 3
[0051] The medium-entropy sodium-ion battery cathode material Na 0.67 Fe 0.2 Mn 0.65 Cu 0.15 O2(NFMC) and a preparation method thereof, specifically comprising the following steps:
[0052] S1, Na2CO3, Fe2O3, MnO2 and CuO are weighed according to the stoichiometric ratio, and then are fully ground with a mortar and pestle. After that, the powders are mixed with zirconia grinding balls and 10mL of ethanol is added to obtain a precursor;
[0053] S2, the precursor is placed in a ball mill jar and ball-milled in a planetary ball mill at a speed of 400r / min for 8h, and then is dried at 80℃ for 12h to obtain a uniformly mixed powder;
[0054] S3, the mixed powder is scraped off and ground, and then is pressed into a wafer with a diameter of 13mm by using a powder tablet press at a pressure of 10MPa;
[0055] S4, the wafer is calcined at 900℃ for 8h in a muffle furnace under air atmosphere, and then is quickly transferred for quenching treatment. After complete cooling, it is fully ground and stored in an argon-filled glove box to avoid moisture and air pollution, to obtain the low-entropy sodium-ion battery cathode material Na 0.67 Fe 0.2 Mn 0.65 Cu 0.15 O2(NFMC) and a preparation method thereof, specifically comprising the following steps:
[0056] Comparative Example 4
[0057] The medium-entropy sodium-ion battery cathode material Na 0.67 Fe 0.2 Mn 0.65 Mg 0.15 O2(NFMM) and a preparation method thereof, specifically comprising the following steps:
[0058] S1, Na2CO3, Fe2O3, MnO2 and MgO were weighed according to the stoichiometric ratio, and then were ground with a mortar and pestle. After that, the powders were mixed with zirconia balls and 10 mL of ethanol to obtain a precursor;
[0059] S2, the precursor was placed in a ball mill jar and ball milled in a planetary ball mill at a speed of 400 r / min for 8 h, and then dried at 80℃ for 12 h to obtain a uniformly mixed powder;
[0060] S3, the mixed powder was scraped off and ground, and then was pressed into a circular sheet with a diameter of 13 mm using a powder tablet press at a pressure of 10 MPa;
[0061] S4, the circular sheet was first calcined in a muffle furnace at 900℃ for 8 h under an air atmosphere, and then was quickly transferred for quenching treatment. After complete cooling, the sample was thoroughly ground and stored in an argon-filled glove box to avoid moisture and air pollution, to obtain an entropy-stabilized sodium-ion battery cathode material Na 0.67 Fe 0.2 Mn 0.65 Mg 0.15 O2(NFMM).
[0062] Test Example 1
[0063] (1) The sodium-ion battery cathode materials prepared in Example 1 and Comparative Examples 1-2 were subjected to SEM characterization, and the results are shown in Figure 1 From Figure 1 it can be seen that as the entropy value increases, the proportion of the (010) crystal plane increases, and the proportion of the (001) crystal plane decreases.
[0064] (2) The sodium-ion battery cathode materials prepared in Example 1 and Comparative Examples 1-2 were subjected to X-ray energy spectrum analysis, and the results are shown in Figure 2 From Figure 2 it can be seen that all elements are uniformly distributed in the material bulk phase.
[0065] (3) The sodium-ion battery cathode materials prepared in Example 1 and Comparative Examples 2-4 were subjected to XPS test, and the results are shown in Figure 3 From Figure 3 (a), it can be seen that the Fe 2p 1 / 2 and Fe 2p 3 / 2 peaks are located at 724.9 eV and 711.6 eV, respectively, and the doping does not cause the change of Fe 2p peak position. The initial valence state of Fe in the four materials is +3. From Figure 3 (b), it can be seen that Mn 3+ and Mn 4+ coexist in the four materials; among them, Mn 3+ 2p 1 / 2 and 2p 3 / 2653.7eV and 642.1eV, respectively, indicating that the valence state of Mn in NFM is +3.66. After doping, the peaks of Mn 2p and Mn 2p 4+ 2p 1 / 2 and 2p 3 / 2 peaks of Mn 2p and Mn 2p 3+ and Mn 4+ corresponding to the peak area changed, the trend of change is shown in Figure 3 (c). According to the ratio of Mn 2p 3+ and Mn 2p 4+ peak area, the valence state of Mn in NFM is about +3.66, and the valence state of Mn in NFMC, NFMM and NFMCM after doping is about +3.74, which is consistent with the designed valence state of Mn. From Figure 3 (d), it can be seen that the peaks of Cu 2p 1 / 2 and Cu 2p 3 / 2 are located at 953.5eV and 933.4eV, respectively, indicating that the valence state of copper in NFMC is +2. From Figure 3 (e), it can be seen that the peak at 49.8eV corresponds to Mg 2p, indicating that Mg 2+ exists in NFMM; while in NFMCM, Cu 2+ 2p 1 / 2 and 2p 3 / 2 peaks and Mg 2+ 2p peaks are observed, while no XPS signal of Cu and Mg is detected in NFM, proving that Cu and Mg are doped into the lattice of NFMCM.
[0066] (3) The sodium ion batteries prepared in Example 1 and Comparative Examples 1-2 were tested by non-in situ XRD, and the results are shown in Figure 4 From Figure 4 it can be seen that with the increase of entropy value, the proportion of (010) crystal face increases significantly, indicating that the optimization of crystal face structure can be effectively realized by entropy value regulation; and Cu / Mg co-doping further improves the entropy value and increases the proportion of (010) crystal face, further verifying the influence of entropy regulation on the crystal face structure.
[0067] Test Example 2
[0068] Battery assembly:
[0069] Positive sheet: the positive electrode materials of sodium ion batteries, conductive agent acetylene black and binder polyvinylidene fluoride (PVDF) of Example 1 and Comparative Examples 1-4 were respectively dissolved in solvent N-methyl pyrrolidone (NMP) at a mass ratio of 8:1:1, and then grinded into uniform slurry, coated on carbon-coated aluminum foil current collector, and then dried in a vacuum oven at 120℃ overnight to remove NMP solvent, and finally cut into positive sheets with a diameter of 13mm by a slicer.
[0070] Negative electrode sheet: metal sodium;
[0071] Separator: Whatman GF / D glass fiber separator;
[0072] Electrolyte: NaPF6 was dissolved in propylene carbonate and fluoroethylene carbonate (FEC, 5% by volume), to prepare an electrolyte with a NaPF6 concentration of 1 mol / L;
[0073] Assembly of sodium ion battery: In an argon atmosphere glove box, the negative electrode sheet, the separator, and the positive electrode sheet were stacked in order (the side coated with the sodium ion battery positive electrode material of Example 1 was bonded to the separator, and the other side of the separator was bonded to the negative electrode sheet), and the whole was sealed in a battery shell, and 200 μL of electrolyte was added dropwise, respectively, to obtain a sodium ion battery after sealing.
[0074] Battery performance test:
[0075] (1) The sodium ion batteries prepared in Example 1 and Comparative Example 2 were subjected to first cycle electrochemical performance test at 0.2C, and the results are shown in Figure 5 From Figure 5 it can be seen that the sodium ion battery of Example 1 has lower voltage hysteresis and higher specific capacity than the sodium ion battery of Comparative Example 2, indicating that Cu / Mg co-doped NFMCM exhibits higher charge-discharge capacity. This is because of the optimization of the crystal plane ratio, NFMCM has a more reversible sodium ion deintercalation process than NFM, and the introduction of Mg helps to activate anions to participate in the redox reaction to contribute capacity, while the presence of Cu can effectively alleviate the voltage hysteresis problem caused by anion redox, thereby synergistically improving the electrochemical performance of the material.
[0076] (2) The sodium ion batteries prepared in Example 1 and Comparative Example 2 were subjected to cycle performance and coulombic efficiency test at 0.2C in the voltage range of 2V-4.5V to evaluate their reversibility, and the results are shown in Figure 6 From Figure 6 it can be seen that the capacity retention rate of the sodium ion battery of Example 1 after 200 cycles is 59.6%, while the capacity retention rate of the sodium ion battery of Comparative Example 2 after 200 cycles is 48.1%, indicating that NFMCM has better reversible anion redox performance.
[0077] (3) The sodium ion batteries prepared in Example 1 and Comparative Example 2 were subjected to rate performance test at 0.1C-8C different rates, and the results are shown in Figure 7 From Figure 7It can be seen that the rate performance of the sodium ion battery of Example 1 is obviously better than that of the sodium ion battery of Comparative Example 1; for example, at 8C high rate, the discharge capacity of NFM is only 9.3 mAh / g, while the discharge capacity of NFMCM is still 65.4 mAh / g. This is because the entropy increase stabilization effect and the crystal face regulation optimization jointly improve the sodium ion transmission rate.
[0078] (4) The cycle performance of the sodium ion batteries prepared from Example 1 and Comparative Examples 2-4 was tested at 0.1C, and the dQ / dV graph of the first six cycles was obtained, as shown in Figure 8 Figure 8 It can be seen that the positive electrode material of the sodium ion battery of Example 1 exhibits the best cycle performance and the smallest voltage decay. By comparing the CV curves of the first six cycles of the four materials, it is found that the single Mg doping activates the anion redox reaction in the first cycle, but the stability of the O redox is poor, while the Cu doping significantly enhances the reversibility of the O redox by virtue of the strong Cu-O covalent bond, so the synergistic doping of Cu and Mg not only improves the anion redox capacity of the material, but also effectively improves the reversibility of the reaction.
[0079] Obviously, the above examples are merely examples for the sake of clarity, and are not limiting of the embodiments. For those of ordinary skill in the art, other different forms of changes or variations can be made on the basis of the above description. Here, it is not necessary and impossible to exhaust all the embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present application.
Claims
1. A medium-entropy sodium-ion battery cathode material, characterized in that, The chemical formula of the medium-entropy sodium-ion battery cathode material is Na. x Fe a Mn b M c O2; where M is Cu, Zn, Ni, Cr, Co, Ti, Sn and Mg, 0.5≤x≤1, 0.2≤a≤0.5, 0.3≤b≤0.8, 0<c≤0.2, a+b+c=1, and the values of x, a, b and c satisfy the charge balance of the chemical formula.
2. The method for preparing the medium-entropy sodium-ion battery cathode material as described in claim 1, characterized in that, Includes the following steps: Sodium, iron, manganese, copper, and magnesium sources are mixed in stoichiometric ratios, and the mixture is then ball-milled, pressed, and calcined to obtain the medium-entropy sodium-ion battery cathode material.
3. The method for preparing the medium-entropy sodium-ion battery cathode material according to claim 2, characterized in that, The sodium source is selected from one or more of sodium carbonate, sodium chloride, sodium fluoride, sodium nitrate, and sodium acetate.
4. The method for preparing the medium-entropy sodium-ion battery cathode material according to claim 2, characterized in that, The iron source is selected from one or more of ferric oxide, ferrous oxide, ferrous carbonate, ferrous nitrate, ferric acetate, and ferric chloride.
5. The method for preparing the medium-entropy sodium-ion battery cathode material according to claim 2, characterized in that, The manganese source is selected from one or more of manganese dioxide, manganese trioxide, manganese carbonate, manganese sulfate, and manganese nitrate.
6. The method for preparing the medium-entropy sodium-ion battery cathode material according to claim 2, characterized in that, The copper source is selected from one or more of copper oxide, copper acetate, copper sulfate, copper nitrate, and copper chloride.
7. The method for preparing the medium-entropy sodium-ion battery cathode material according to claim 2, characterized in that, The magnesium source is selected from one or more of magnesium oxide, magnesium carbonate, magnesium sulfate, magnesium acetate, and magnesium chloride.
8. The method for preparing the medium-entropy sodium-ion battery cathode material according to claim 2, characterized in that, The ball mill operates at a speed of 200 r / min to 600 r / min for 2 h to 8 h.
9. The method for preparing the medium-entropy sodium-ion battery cathode material according to claim 2, characterized in that, The pressure of the tablet is 9.8MPa-10.2MPa; the thickness of the material after tableting is 4.8mm-5.2mm, and the diameter is 12mm-14mm.
10. The method for preparing the medium-entropy sodium-ion battery cathode material according to claim 2, characterized in that, The calcination temperature is 500℃-1000℃, and the time is 8h-12h.