Positive electrode material for manganese-based sodium-ion battery, method for producing positive electrode material for manganese-based sodium-ion battery, positive electrode sheet, and sodium-ion secondary battery

Abstract

To provide a positive electrode material for a manganese-based sodium ion battery having advantages of high capacity and low cost, and a method for manufacturing the same.SOLUTION: The chemical formula of the positive electrode material is NaxM1aFebMncO2, 0.6 ≤ x ≤ 1.0, 0.05 ≤ a ≤ 0.4, 0.1 ≤ b ≤ 0.45, 0.4 ≤ c ≤ 0.6, a + b + c = 1, where M1 is a metallic element that is in a solid state and has no oxidation reduction function, and is preferably at least one of Li, Mg, Zn, Ca, and Al. In the XRD spectrum of the cathode material, the peak intensity ratio of the crystal plane diffraction peaks (003) and (104) is 0.5 ≤ I (003) / I (104) ≤ 0.98. In the Raman spectrum of the positive electrode material, the characteristic peak S appears in the range of 660 to 680cm - 1, the characteristic peak B appears in the range of 565 to 580cm - 1, and the peak intensity ratio of the two is 0.2 ≤ IS / IB ≤ 0.8.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to the field of sodium ion batteries, and more particularly to manganese-based sodium ion battery positive electrode materials, positive electrode sheets, and sodium ion secondary batteries. [Background technology]

[0002] Over the past few decades, lithium-ion batteries have been widely used in portable electronic devices, hybrid electric vehicles, and electric vehicles. However, limited lithium resources have raised concerns about their continued use as an ideal energy storage option. Due to the widespread availability and low cost of sodium resources, as well as the low-temperature performance and rate characteristics of sodium-ion batteries, the industry has gradually recognized the importance of sodium-ion batteries as a new energy storage battery. The search for high-energy density, low-cost cathode materials will undoubtedly be a key factor in promoting the industrialization of sodium-ion batteries. Various sodium-containing compounds have been intensively investigated as cathode materials for sodium-ion batteries. Among them, layered transition metal sodium oxide (NaO) x MO2 (where M is Mn, Co, Cr, Fe, or V) is considered one of the most promising cathode materials for industrialization due to its diverse structure and controllability of composition.

[0003] Among the Na transition metal oxides with different structures and compositions, Na 2 / 3 Ni 1 / 3 Mn 2 / 3 O2, NaLi 0.2 Ni 0.25 Mn 0.75 O2, Na x Fe y Mn 1-y O2, NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 It has been demonstrated that materials such as O2 exhibit electrochemical activity. Although a certain energy density can be achieved by designing and controlling the composition and structure, and by selecting and combining different transition metal elements, currently commercially available O3-type layered oxide cathode materials, such as NaNi 1 / 3 Fe1 / 3 Mn 1 / 3 The reversible capacity of O2 is generally limited to around 130-150 mAh / g. The capacity of these sodium-ion battery cathode materials is significantly lower than that of high-nickel ternary cathode materials for lithium-ion batteries and even lower than that of low-cost lithium iron phosphate cathode materials. Furthermore, the high nickel content (>20%) in these materials increases the cost of the cathode materials. Therefore, research and development of high-capacity, low-cost cathode materials is crucial for accelerating the industrialization and practical application of sodium-ion batteries, and it is essential to provide technical solutions to the above problems. Summary of the Invention [Problem to be solved by the invention]

[0004] To overcome the drawbacks of the prior art, a manganese-based sodium-ion battery cathode material is provided, which has the advantages of high capacity and low cost compared to the conventional sodium-ion battery cathode materials, which have the problems of high nickel content, high cost, and low practical capacity. [Means for solving the problem]

[0005] To achieve the above object, in one aspect, the present invention provides a manganese-based sodium-ion battery positive electrode material, which is specifically as follows:

[0006] It contains O3-type layered oxides with the R-3m space group and the chemical formula Na x M1 a Fe b Mn c O2 (where 0.6≦x≦1.0, 0.05≦a≦0.4, 0.1≦b≦0.45, 0.4≦c≦0.6, a+b+c=1). The metal element M1 is selected from at least one of Li, Mg, Zn, Ca, and Al, and in the XRD spectrum of the positive electrode material, the peak intensity ratio I of the crystal plane diffraction peaks (003) and (104) is 1. (003) / I(104) is 0.5≦I (003) / I (104) In the Raman scattering spectrum of the positive electrode material, the characteristic peak S is 660-680 cm -1 The characteristic peak B appears in the range of 565–580 cm -1 The peak intensity ratio between the two peaks is I S / I B is 0.3≦I S / I B ≦0.8.

[0007] Preferably, the positive electrode material Na x M1 a Fe b Mn c In O2, 0.7≦x≦0.9, 0.1≦a≦0.35, and 0.1≦b≦0.3.

[0008] Preferably, the positive electrode material Na x M1 a Fe b Mn c O2 crystal plane peak intensity ratio I (003) / I (104) is 0.6≦I (003) / I (104) ≦0.9.

[0009] Preferably, 0.4≦I S / I B ≦0.7.

[0010] In another aspect, the present invention also provides a method for producing a manganese-based sodium-ion battery cathode material, the method comprising the steps of:

[0011] A method for producing a manganese-based sodium-ion battery cathode material includes the following steps:

[0012] S1: A step of thoroughly mixing a sodium salt, an M1 source, an Fe source, and an Mn source in a predetermined ratio by ball milling and drying to obtain a reaction mixture precursor, wherein the M1 source, the Fe source, and the Mn source are selected from oxides, acetates, or nitrates of the corresponding metals.

[0013] S2: A step of calcining the reaction mixture precursor obtained in step S1 at 700°C to 800°C for 2 to 6 hours to obtain a calcined precursor 1.

[0014] S3: A step of calcining the positive electrode material precursor obtained in step S2 at 800° C. to 1050° C. for 10 to 20 hours to obtain a calcined precursor 2.

[0015] S4: The calcined precursor 2 is rapidly cooled to 400 to 600°C and held at that temperature for 3 to 6 hours to obtain a positive electrode material precursor.

[0016] S5: The cathode material precursor is naturally cooled to room temperature to obtain a manganese-based sodium ion battery cathode material.

[0017] Preferably, the firing temperature in step S2 is 750 to 800° C., and the temperature rise rate is 2 to 10° C. / min.

[0018] Preferably, the firing temperature in step S3 is 900 to 1000° C., and the temperature rise rate is 2 to 5° C. / min.

[0019] Preferably, in step S4, the fired precursor 2 is rapidly cooled to 430 to 560° C. and held at that temperature for 4 to 5 hours.

[0020] Furthermore, the present invention also provides a positive electrode sheet comprising the manganese-based sodium-ion battery positive electrode material.

[0021] Finally, the present invention provides a sodium-ion secondary battery comprising a positive electrode sheet, a negative electrode sheet, and a separator disposed between the positive electrode sheet and the negative electrode sheet, wherein the positive electrode sheet comprises the manganese-based sodium-ion battery positive electrode material. [Effects of the Invention]

[0022] The beneficial effects of the present invention are as follows: The cathode material provided by the present invention is primarily composed of manganese and is low-cost. It also combines an M1 element, which does not have redox function, with a transition metal element, Fe, which does have redox function. By adjusting the material components and structure, the cathode material can induce anion redox reactions based on the redox reaction of the supported transition metal. Furthermore, because the anion redox reaction is highly reversible, the number of sodium ions that can be reversibly released and inserted into the structure is significantly increased, improving the reversible capacity of the cathode material. The reversible discharge specific capacity of the cathode active material of the present invention reaches 180 mAh / g or more. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 shows the XRD pattern and Raman spectrum of the positive electrode material of Example 3 of the present invention. [Figure 2] FIG. 2 shows the XRD pattern and Raman spectrum of the positive electrode material of Example 12 of the present invention. [Figure 3] FIG. 3 shows the XRD pattern and Raman spectrum of the positive electrode material of Comparative Example 1 of the present invention. [Figure 4] FIG. 4 shows the XRD pattern and Raman spectrum of the positive electrode material of Comparative Example 3 of the present invention. [Figure 5] FIG. 5 shows the charge-discharge curves of the positive electrode material of Example 12 of the present invention. [Figure 6] FIG. 6 shows a schematic diagram of the energy band of the NaxM1aFebMncO2 cathode material of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] In order to further clarify the technical solutions and advantages of the present invention, the present invention and its beneficial effects will be described in more detail below with reference to specific embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0025] As used herein, "at least one" means one or more, and "plurality" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can mean a, b, c, ab (i.e., a and b), ac, bc, or abc, respectively, where a, b, and c can each be single or multiple.

[0026] To overcome the shortcomings of existing technologies, a manganese-based sodium-ion battery cathode material is provided, which solves the problems of current sodium-ion battery cathode materials, such as high nickel content, high cost, and low capacity, which cannot meet the requirements for practical application. The manganese-based cathode material of the present invention has the advantages of high capacity and low cost.

[0027] In order to achieve the above object, the present invention provides, as one aspect thereof, the following manganese-based sodium ion battery positive electrode material.

[0028] The manganese-based sodium-ion battery cathode material contains an O3-type layered oxide with the R-3m space group and the chemical formula is Na x M1 a Fe b Mn c O2, where 0.6≦x≦1.0, 0.05≦a≦0.4, 0.1≦b≦0.45, 0.4≦c≦0.6, and a+b+c=1, and M1 is a metal in the solid phase that does not have redox function. The positive electrode material is a metal element, and M1 is selected from at least one of Li, Mg, Zn, Ca, and Al. In the XRD spectrum of the positive electrode material, the peak intensity ratio of the crystal plane diffraction peak (003) to the peak (104) is 0.5≦I (003) / I (104) ≦0.98, and in the Raman scattering spectrum of the positive electrode material, -1 The characteristic peak S appears in the range of 565 to 580 cm -1 The characteristic peak B appears in the range of 0.3≦I S / I B ≦0.8.

[0029] Here, the Na content x can be 0.6≦x<0.7, 0.7≦x<0.8, 0.8≦x<0.82, 0.82≦x<0.85, 0.85≦x<0.9, or 0.9≦x≦1.0. Preferably, x can be 0.7≦x≦0.9. Using a Na content within this range in combination with M1, Fe, and Mn can induce a reversible anion redox reaction while ensuring the conductivity and cycle stability of the positive electrode active material.

[0030] Regarding the M1 element, adding a portion of a metal element that does not exhibit redox activity in the solid phase to the cathode material and combining it with Fe and Mn results in a locally ordered cathode material. Compared to conventional combinations containing only redox-active metal elements, this cathode active material also functions to induce anion redox reactions as a whole, increasing the number of reversibly detachable and detachable sodium ions, thereby improving the reversible capacity of the cathode material. A more stable structure also improves subsequent cycle performance. Preferably, the M1 element is Mg or Zn. This invention breaks the conventional practice of using only redox-active metal elements in cathode active materials. By adjusting the elemental composition, even if the number of redox-active metal elements in the composition is relatively reduced, the redox reaction of anions is promoted, increasing the number of reversibly detachable and detachable sodium ions, thereby improving the reversible capacity and cycle performance.

[0031] Regarding Fe and Mn in the positive electrode material, the inventors have found that combining the metal element M1, Fe, and Mn in a specific ratio results in a more stable locally ordered structure, improving the reversible capacity and cycle characteristics.

[0032] Regarding the microstructure of the positive electrode material, the peak intensity ratio of the crystal plane diffraction peaks (003) and (104) in the XRD spectrum is 0.5≦I (003) / I (104) ≦0.98, and in the Raman scattering spectrum, 660 to 680 cm-1 The characteristic peak S is in the range of 565 to 580 cm -1 The characteristic peak B appears in the range of 0.3≦I S / I B ≦0.8. In this case, the positive electrode material has a better layered structure, which promotes the interaction between the transition metal element and oxygen, thereby improving the capacity and stability of the positive electrode material.

[0033] Preferably, the positive electrode material Na x M1 a Fe b Mn c In O2, 0.1≦a≦0.35, 0.1≦b≦0.3.

[0034] Preferably, the positive electrode material Na x M1 a Fe b Mn c The crystal plane peak intensity ratio of O2 is 0.6≦I (003) / I (104) ≦0.9.

[0035] Preferably, 0.4≦I S / I B ≦0.7.

[0036] In another aspect, the present invention also provides a method for making a manganese-based sodium-ion battery cathode material.

[0037] 1. A method for producing a manganese-based sodium-ion battery cathode material, comprising the steps of: S1: A step of thoroughly mixing a sodium salt, an M1 source, an Fe source, and an Mn source in a predetermined ratio by ball milling and drying to obtain a reaction mixture precursor, wherein the M1 source, the Fe source, and the Mn source are selected from oxides, acetates, or nitrates of the corresponding metals. S2: A step of calcining the reaction mixture precursor from step S1 at 700°C to 800°C for 2 to 6 hours to obtain calcined precursor I. S3: The positive electrode material precursor obtained in step S2 is calcined at 800° C. to 1050° C. for 10 to 20 hours to obtain a calcined precursor II. S4: The calcined precursor II is rapidly cooled to 400 to 600°C and maintained at this temperature for 3 to 6 hours to obtain a positive electrode material precursor. S5: The positive electrode material precursor is naturally cooled to room temperature to obtain a manganese-based sodium ion battery positive electrode material.

[0038] The stepwise calcination and stepwise cooling method of the present invention promotes the formation of a highly ordered internal structure in the cathode material during the reaction heating process, and rapid cooling after calcination further improves the crystal morphology and significantly reduces internal structural defects, thereby improving the reversible capacity and cycle performance of the material.

[0039] Preferably, the firing temperature in step S2 is 750°C to 800°C, and the temperature rise rate is 2 to 10°C / min.

[0040] Preferably, the firing temperature in step S3 is 900° C. to 1000° C., and the temperature rise rate is 2 to 5° C. / min.

[0041] Preferably, in step S4, the fired precursor 2 is rapidly cooled to 430 to 560° C. and held at that temperature for 4 to 5 hours.

[0042] The present invention also provides a cathode sheet containing the above-described manganese-based sodium-ion battery cathode material. Specifically, the cathode sheet includes a cathode current collector and a cathode active material layer coated on at least one surface of the cathode current collector. The cathode active material in the cathode active material layer is the cathode material described herein. The cathode active material layer also includes a commonly used binder and a conductive agent. Examples of binders include, but are not limited to, at least one of SBR, PAA, PI, PAN, and PVDF. Examples of conductive agents include, but are not limited to, at least one of carbon black (e.g., Super-P, KS-6), VGCF, multi-walled CNT, and single-walled CNT. These will not be described in detail here.

[0043] The positive electrode current collector can be any material that can be used as a positive electrode current collector in a sodium-ion battery, for example, but is not limited to, metal foil, more specifically, aluminum foil.

[0044] Specifically, the positive electrode sheet can be produced by a conventional method for producing a positive electrode sheet, for example, by mixing the positive electrode material of the present invention, a conductive agent, and a binder in appropriate proportions to form a slurry, which is then applied, roll-pressed, and punched out at a certain areal density. The slurry can contain 85 to 97 wt % of the positive electrode material of the present invention, 0.01 to 5 wt % of the conductive agent, and 0.1 to 8 wt % of the binder.

[0045] The present invention also provides a sodium ion secondary battery including a positive electrode sheet, a negative electrode sheet, and a separator disposed between the positive electrode sheet and the negative electrode sheet.

[0046] The positive electrode sheet is a positive electrode sheet containing the aforementioned manganese-based sodium-ion battery positive electrode material. The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on at least one surface of the negative electrode current collector. The negative electrode active material layer may be, but is not limited to, one or more of soft carbon, hard carbon, carbon fiber, mesocarbon microbeads, tin-based materials, oxide-based negative electrode materials, or other metals capable of forming an alloy with sodium. The carbon-based negative electrode material can be selected from one or more of soft carbon, hard carbon, carbon fiber, and mesocarbon microbeads, and the tin-based material can be selected from one or more of elemental tin, tin oxide compounds, and tin alloys. The negative electrode current collector is typically a structure or component that collects current. Any material suitable for use as a negative electrode current collector in a sodium-ion battery can be used. Examples include metal foil, more specifically aluminum foil and copper foil. To facilitate performance testing of the positive electrode material, a sodium-ion battery can be assembled using the sodium sheet directly as the negative electrode.

[0047] The separator can be made from any material known in the art for sodium-ion battery separators, including, but not limited to, polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester, and natural fibers, or it can be an ionically conductive solid electrolyte membrane. [Example]

[0048] In order to further clarify the technical solutions and advantages of the present invention, the following will further describe the present invention and its beneficial effects with reference to specific embodiments and accompanying drawings, but the present invention is not limited thereto.

[0049] [Example 1] The manganese-based sodium-ion battery cathode material is an O3-type layered oxide with the R-3m space group. The chemical formula of the cathode material is Na 0.8 Mg 0.05 Fe 0.45 Mn 0.5 O2. The preparation method is as follows: S1: Na2CO3, MgCO3, Fe2O3, and Mn2O3 are mixed in the molar ratio of the metal elements listed above and heated to 400°C. The mixture is wet ball milled at 1000 rpm for 12 hours and then dried at 120°C for 6 hours to obtain a reaction mixture precursor. S2: The reaction mixture precursor obtained in step S1 was calcined at 750° C. for 3 hours to obtain calcined precursor 1. S3: The positive electrode material precursor obtained in step S2 was calcined at 950° C. for 15 hours to obtain calcined precursor 2. S4: The calcined precursor 2 was rapidly cooled to 450°C and held at this temperature for 4 hours to obtain a positive electrode material precursor. S5: The cathode material precursor is naturally cooled to room temperature, and Na is used as the manganese-based sodium ion battery cathode material. 0.8 Mg 0.05 Fe 0.45 Mn 0.5 Got O2.

[0050] [Examples 2 to 4] Unlike Example 1, the positive electrode material in this example is Na 0.8 Mg 0.1 Fe 0.4 Mn 0.5 O2, Na 0.8 Mg 0.2 Fe 0.3 Mn 0.5 O2, and Na 0.8 Mg 0.3 Fe 0.2 Mn 0.5 O2. The preparation process can be carried out by adjusting the content of each element according to the molar ratio. For details, see Example 1, which will not be repeated here.

[0051] [Examples 5 to 8] Unlike Examples 1 to 4, M1 in Examples 5 to 8 is Zn. 0.8 Zn 0.05 Fe 0.45 Mn 0.5 O2, Na 0.8 Zn 0.1 Fe 0.4 Mn 0.5 O2, Na 0.8 Zn 0.2 Fe 0.3 Mn 0.5 O2, and Na 0.8 Zn 0.3 Fe 0.2 Mn 0.5 O2. The preparation process can be carried out by adjusting the content of each element according to the molar ratio. For details, see Example 1, which will not be repeated here.

[0052] [Examples 9 to 11] Unlike Example 1, M1 in Examples 9 to 11 is a combination of two elements. 0.8 (Li 0.1 Al 0.1 )Fe 0.3 Mn 0.5 O2, Na 0.8 (Zn 0.1 Ca 0.1 )Fe 0.3 Mn 0.5 O2, and Na0.8 (Li 0.05 Mg 0.15 )Fe 0.3 Mn 0.5 O2. The preparation process can be carried out by adjusting the molar ratio of each element. For details, see Example 1, which will not be repeated here.

[0053] [Examples 12 to 13] Unlike Example 1, M1 in Examples 12 and 13 is a combination of three elements. 0.8 (Li 0.04 Mg 0.07 Al 0.09 )Fe 0.3 Mn 0.5 O2 and Na 0.8 (Li 0.06 Ca 0.05 Zn 0.09 )Fe 0.3 Mn 0.5 O2. The preparation process can be adjusted according to the molar ratio of each element. For details, see Example 1, which will not be repeated here.

[0054] [Comparative Example 1] Unlike Example 1, the positive electrode active material of this comparative example is Na 0.8 Fe 0.5 Mn 0.5 O2. The preparation process can be adjusted according to the molar ratio of each element. For details, see Example 1, which will not be repeated here.

[0055] Comparative Example 2 Unlike Example 1, the positive electrode active material of this comparative example is Na 0.8 Fe 0.3 Mn 0.7 O2. The preparation process can be carried out by adjusting the molar ratio of each element. For details, see Example 1, which will not be repeated here.

[0056] Comparative Example 3 In this comparative example, the positive electrode active material is Na 0.8 Mg 0.2 Fe 0.3 Mn 0.5Unlike Example 3, this comparative example does not employ the stepwise calcination and dispersed cooling method. Instead, the reaction mixture precursor is directly calcined at 950°C for 18 hours and then naturally cooled to room temperature. The other steps are the same as in Example 1.

[0057] The positive electrode materials obtained in Examples 1 to 13 and Comparative Examples 1 to 3 were subjected to XRD and Raman spectroscopic analysis. In the XRD spectrum, the peak intensity ratio of the crystal plane diffraction peaks (003) and (104) was I (003) / I (104) In the Raman scattering spectrum, 660-680 cm -1 The characteristic peak S is in the range of 565 to 580 cm -1 The characteristic peak B appears in the range of I. The intensity ratio of the two peaks is I S / I B The data are shown in Table 1.

[0058] The XRD spectrum and Raman spectrum of Example 3 are shown in FIG.

[0059] The XRD spectrum and Raman spectrum of Example 12 are shown in FIG.

[0060] The XRD spectrum and Raman spectrum of Comparative Example 1 are shown in FIG.

[0061] The XRD spectrum and Raman spectrum of Comparative Example 3 are shown in FIG.

[0062] Next, the above-mentioned positive electrode material is applied to a positive electrode sheet. The positive electrode sheet is manufactured by mixing the positive electrode material, polyvinylidene fluoride, and SP-P in a mass ratio of 90:5:5, then ball milling and stirring to obtain a positive electrode slurry. Next, this slurry is applied to aluminum foil, roll pressed, and then vacuum dried overnight at 160°C. The resulting positive electrode sheet is cold pressed and punched to obtain a positive electrode sheet.

[0063] The resulting positive electrode sheet was used in an R2032 coin battery for electrochemical performance testing. A sodium-ion button battery was fabricated using the positive electrode sheet as the working electrode, sodium foil as the counter electrode, a GB-100R separator, and a nonaqueous electrolyte (ethylene carbonate and ethyl methyl carbonate mixed in a volume ratio of 3:7, with NaPF6 added to make an electrolyte solution with a NaPF6 concentration of 1 mol / L). The fabrication method is described in detail in existing literature, so it will not be described in detail here.

[0064] The obtained sodium-ion coin battery was subjected to a constant temperature current charge-discharge test in a thermostatic chamber at approximately 25°C. The test voltage range was 1.5 to 4.3 V, and the current density was C / 20 (approximately 12.0 mA / g). -1 ) was.

[0065] The performance test results are shown in Table 1 and Figure 5.

[0066] [Table 1]

[0067] FIG. 1 shows the positive electrode material Na prepared according to the components and synthesis method of Example 3. 0.8 Mg 0.2 Fe 0.3 Mn 0.5 The XRD and Raman spectra of O2 are shown. The obtained cathode material has an O3-type structure, and the intensity ratio of the (003) peak near 2θ = 16° to the (104) peak near 2θ = 42° is approximately 0.76. In the Raman spectrum, I S / I B is about 0.62, indicating that the synthesized material has few structural defects and a good layered structure.

[0068] FIG. 2 shows the composition and synthesis method of the positive electrode material Na 0.8 (Li 0.05 Mg 0.1 Al 0.05 )Fe 0.3 Mn 0.5The XRD and Raman spectra of O2 are shown. The obtained cathode material has an O3-type structure, and the intensity ratio of the (003) peak near 2θ = 16° to the (104) peak near 2θ = 42° is approximately 0.69. In the Raman spectrum, I S / I B is about 0.63, indicating that the synthesized material has few structural defects and a good layered structure.

[0069] Figure 3 shows the XRD spectrum of the cathode material prepared according to the components and synthesis method of Comparative Example 1. Similar to Example 3, this material belongs to the O3-type layered oxide. The more obvious difference is that the intensity ratio of the (003) peak near 2θ = 16° and the (104) peak near 2θ = 42° are both significantly greater than 1, and the I S / I B The difference is significantly smaller than 0.3. This indicates obvious structural defects in the layers of the synthesized material. Adding a portion of the metal element M1, which has no redox activity in the solid state, to the cathode material and combining it with Fe and Mn elements results in a cathode material with a locally ordered structure. Meanwhile, compared to the conventional combination of metal elements that only have redox activity, the cathode active material as a whole also has the function of inducing the redox reaction of anions, increasing the number of sodium ions that can be extracted and inserted into the composition, thereby improving the reversible capacity of the cathode material. A more stable structure also improves subsequent cycle performance.

[0070] Figure 4 shows the XRD pattern of the cathode material prepared according to the components and synthesis method of Comparative Example 3. Similar to Example 3, this material belongs to the O3-type layered oxide. The more notable difference is that the intensities of the (003) peak near 2θ = 16° and the (104) peak near 2θ = 42° are approximately 0.95, close to the boundary value of 0.98, and the I S / I BThe value is approximately 0.38, close to the boundary value of 0.3. This indicates that there are certain structural defects in the layers of the synthesized material. It can be seen that the production method of directly heating the precursor mixture to approximately 1000°C for calcination and then naturally cooling to room temperature after calcination causes certain structural defects and is not conducive to the formation of an orderly internal structure of the material. However, stepwise calcination can significantly reduce the internal structural defects, thereby improving the reversible capacity and cycle properties of the material.

[0071] Figure 5 shows the charge-discharge curves for the cathode material of Example 12. The initial charge capacity is nearly 210 mAh / g, and the initial discharge capacity reaches 218 mAh / g. This high reversible capacity exceeds the capacity contribution from the redox reactions of Fe and Mn in this composition. Furthermore, the appearance of a charge plateau near 4.0 V in the charge-discharge curve suggests that the redox reactions of oxygen ions during the charge-discharge process also contribute to charge compensation.

[0072] Figure 6 shows the positive electrode material Na x M1 a Fe b Mn c The energy band diagrams for O2 are shown, which can clearly explain the mechanism of high-capacity charge compensation in various constituent materials in this invention. Figure 6(a) shows a = 0, which means that there is no inert metal element present as M1. Figure 6(b) shows a > 0, which means that at least one inert metal element is present as M1. The presence of M1 ions at transition metal sites in Na-containing layered oxides activates the oxygen redox reaction by forming an oxygen lone pair associated with the non-bonding O-2p state in the electronic structure. Compared to the Na-O-Mn interaction, the more ionic Na-O-M1 interaction places the O-2p state at a higher energy (closer to the Fermi level), making it more susceptible to oxygen ion redox reactions. Furthermore, these elevated non-bonding O-2p orbitals are highly active and can donate or accept additional charges upon insertion or desorption of sodium ions. Therefore, the introduction of this local structure promotes the oxygen ion redox reaction and improves the specific capacitance of the material.

[0073] Based on the disclosure and teachings of the above specification, those skilled in the art will be able to modify and alter the above embodiments. Therefore, the present invention is not limited to the specific embodiments described above. Any obvious improvements, substitutions, or modifications made by those skilled in the art based on the present invention will fall within the scope of protection of the present invention. Furthermore, although specific terms are used in this specification, these terms are for the convenience of description and do not limit the present invention.

Claims

1. A manganese-based sodium-ion battery cathode material, comprising: the positive electrode material is an O3-type layered oxide having an R-3m space group, The chemical formula of the positive electrode material is Na ｘ M1 ａ Fe ｂ Mn ｃ O ２ , 0.6≦x≦1.0, 0.05≦a≦0.4, 0.1≦b≦0.45, 0.4≦c≦0.6, a+b+c=1, M1 is a metal element that does not have an oxidation-reduction function in a solid phase, and M1 is selected from at least one of Li, Mg, Zn, N, Ca, and Al; In the XRD spectrum of the positive electrode material, the crystal plane diffraction peak intensity ratio I between (003) and (104) （００３） / I （１０４） However, 0.5≦I （００３） / I （１０４） ≦0.98, In the Raman scattering spectrum of the positive electrode material, －１ The characteristic peak S appears in the range of 565 to 580 cm －１ The characteristic peak B appears in the range of Ｓ / I Ｂ is 0.3≦I Ｓ / I Ｂ ≦0.

8.

2. The positive electrode material Na ｘ M1 ａ Fe ｂ Mn ｃ O ２ 2. The manganese-based sodium ion battery positive electrode material according to claim 1, wherein 0.7≦x≦0.9, 0.1≦a≦0.35, and 0.1≦b≦0.

3.

3. The positive electrode material Na ｘ M1 ａ Fe ｂ Mn ｃ O ２ Crystal plane peak intensity ratio I （００３） / I （１０４） However, 0.6≦I （００３） / I （１０４） 2. The manganese-based sodium ion battery positive electrode material according to claim 1, wherein the manganese-based sodium ion battery positive electrode material has a β-value of 0.9 or less.

4. 0.4≦I Ｓ / I Ｂ 2. The manganese-based sodium ion battery positive electrode material according to claim 1, wherein the β-value of the manganese-based sodium ion battery positive electrode material is ≦0.

7.

5. A method for producing the manganese-based sodium-ion battery cathode material of any one of claims 1 to 4, comprising the steps of: S1: A step of thoroughly mixing a sodium salt, an M1 source, an Fe source, and an Mn source in a certain ratio by ball milling, and drying to obtain a reaction mixture precursor, wherein the M1 source, the Fe source, and the Mn source are selected from oxides, acetates, or nitrates of the corresponding metals; S2: The reaction mixture precursor of step S1 is calcined at 700°C to 800°C for 2 to 6 hours to obtain calcined precursor 1. S3: The positive electrode material precursor of step S2 is calcined at 800° C. to 1050° C. for 10 to 20 hours to obtain calcined precursor 2. S4: The calcined precursor 2 is rapidly cooled to 400°C to 600°C, and the temperature is maintained for 3 to 6 hours to obtain a positive electrode material precursor. S5: The positive electrode material precursor is naturally cooled to room temperature to obtain a manganese-based sodium ion battery positive electrode material.

6. 6. The method for producing a manganese-based sodium ion battery positive electrode material according to claim 5, wherein the firing temperature in step S2 is 750°C to 800°C, and the temperature rising rate is 2°C / min to 10°C / min.

7. 6. The method for producing a manganese-based sodium ion battery positive electrode material according to claim 5, wherein the firing temperature in step S3 is 900°C to 1000°C, and the temperature rising rate is 2°C / min to 5°C / min.

8. 6. The method for producing a manganese-based sodium ion battery positive electrode material according to claim 5, wherein in step S4, the fired precursor 2 is rapidly cooled to 430°C to 560°C and kept at that temperature for 4 to 5 hours.

9. A positive electrode sheet comprising the manganese-based sodium ion battery positive electrode material according to any one of claims 1 to 4.

10. A sodium ion secondary battery comprising: a positive electrode sheet; a negative electrode sheet; and a separator separated between the positive electrode sheet and the negative electrode sheet, wherein the positive electrode sheet is the positive electrode sheet according to claim 9.

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