Ferro-manganese fluoride, sodium ion battery positive electrode material, preparation method of sodium ion battery positive electrode material, sodium ion battery and electric equipment

Abstract

The invention relates to the technical field of sodium-ion batteries, and discloses ferro-manganese fluoride, a sodium-ion battery positive electrode material and a preparation method thereof, and a sodium-ion battery. The chemical formula of the ferro-manganese fluoride is Fe < 1-beta > Mn < beta > F2, and beta is more than or equal to 0.5 and less than 1. The ferro-manganese fluoride provided by the invention can be used as a coating layer of a sodium ion battery positive electrode material, and the coating layer can provide charge compensation in a sodium ion deintercalation / intercalation process and improve the discharge medium voltage, so that the material realizes long cycle life while maintaining high specific capacity.

Description

Iron-manganese fluorides, sodium-ion battery cathode materials and their preparation methods, sodium-ion batteries, electrical equipment Technical Field

[0001] This invention relates to the field of sodium-ion battery technology, specifically to iron-manganese fluoride, sodium-ion battery cathode materials and their preparation methods, sodium-ion batteries, and electrical equipment. Background Technology

[0002] Sodium-ion layered oxide cathode materials have advantages such as abundant raw materials, low price, and simple preparation, and show important application prospects in the fields of consumer electronics and large-scale energy storage.

[0003] However, in the process of achieving more reversible insertion and extraction of sodium ions, layered oxide cathode materials often undergo complex structural evolution, including phenomena such as lattice distortion, transition metal migration, or stacking faults. These structural degradation problems can further induce phase separation and microcracks in the particles.

[0004] Surface coating modification is an important way to improve the structural and performance stability of O3-type layered oxide cathodes under high voltage. On the one hand, surface coating can protect the cathode from surface structure degradation caused by electrolyte and humid air corrosion; on the other hand, coating materials with three-dimensional sodium ion channels can also accelerate sodium ion transport and improve electrochemical performance.

[0005] Existing surface coating materials are typically oxides, fluorides, and phosphates, all of which suffer from poor electronic conductivity, potentially leading to increased surface impedance and slow sodium ion transport kinetics.

[0006] Therefore, developing a novel surface coating material to meet the requirements of sodium-ion battery cathode materials for long-cycle performance in practical applications is of great significance. Summary of the Invention

[0007] The purpose of this invention is to provide an iron-manganese fluoride coating material, a sodium-ion battery cathode material and its preparation method, a sodium-ion battery, and electrical equipment, aiming to solve at least one of the above-mentioned technical problems in the prior art.

[0008] To achieve the above objectives, a first aspect of the present invention provides an iron-manganese fluoride, wherein the chemical formula of the iron-manganese fluoride is Fe. 1-β Mn β F2, where 0.5 ≤ β < 1.

[0009] Preferably, the iron-manganese fluoride satisfies one of the following conditions: ① the chemical formula of the iron-manganese fluoride is Fe 1-β Mn β In F2, 0.9 ≤ β < 1; ② The compacted density of the iron-manganese fluoride is 3.0-4.0 g / cm³.3 ③ The particle size D50 of the iron-manganese fluoride is 100-500 nm.

[0010] A second aspect of the present invention provides a method for preparing the iron-manganese fluoride described in the first aspect above. The method includes the following steps: stirring and mixing a fluorine source, a manganese source and an iron source to obtain a mixture; and calcining the mixture under an inert atmosphere to obtain the iron-manganese fluoride.

[0011] Preferably, the preparation method satisfies one of the following conditions: (i) the fluorine source is selected from at least one of ammonium fluoride and manganese fluoride; (ii) the manganese source is selected from at least one of manganese carbonate, manganese oxide, and manganese oxalate; (iii) the iron source is selected from at least one of ferric oxide, ferric nitrate, and ferric fluoride; (iv) the calcination treatment conditions include: a temperature of 400-500℃ and a holding time of 4-8h.

[0012] A third aspect of the present invention provides a sodium-ion battery cathode material, the sodium-ion battery cathode material comprising a matrix material and a coating layer covering at least a portion of the surface of the matrix material; the chemical formula of the coating layer is Fe. 1-β Mn β F2, where 0.5 ≤ β < 1.

[0013] Preferably, the sodium-ion battery cathode material satisfies at least one of the following conditions: A. The chemical formula of the matrix material is Na. x MO2, where 0.8 < x < 1.1, and M is selected from at least one of Ni, Fe, Mn, Co, Ti, Cu, Ca, Zn, Mg, Al, Y, Ce, Sr, Sn, Ba, and La; B, based on the total mass of the matrix material, the mass of the coating layer is 0.5-2.5 wt%, optionally 1-2 wt%; C, the D50 of the sodium-ion battery cathode material is 3-20 μm; D, the sodium-ion battery cathode material is single crystal or polycrystalline; E, the thickness of the coating layer is H, 0 < H ≤ 100 nm; F, the matrix material is a layered oxide; optionally, the layered oxide has an O3 phase structure; G, the chemical formula of the matrix material is Na. x MO2, wherein 0.8 < x < 1.1, and M comprises Ni and Mn; optionally, M further comprises at least one of Fe, Ti and Cu, and even more optionally, M further comprises at least one of Co, Ca, Zn, Mg, Al, Y, Ce, Sr, Sn, Ba and La.

[0014] A fourth aspect of the present invention provides a method for preparing the sodium-ion battery cathode material described in the third aspect above. The method includes the following steps: mixing a coating material and a matrix material to obtain a mixture; sintering the mixture in an air atmosphere to obtain the sodium-ion battery cathode material; wherein the chemical formula of the coating material is Fe. 1-β Mn β F2, where 0.5 ≤ β < 1.

[0015] Preferably, the preparation method satisfies at least one of the following conditions: a) the matrix material is obtained by calcining raw materials containing a sodium source and a sodium-ion battery cathode material precursor in an air atmosphere; b) the sintering conditions include a temperature of 400-700℃ and a time of 3-6h; c) the mass ratio of the coating material to the matrix material is 0.5-2.5:100.

[0016] Preferably, the preparation method satisfies at least one of the following conditions: 1) the sodium source is selected from at least one of sodium carbonate, sodium hydroxide, and sodium nitrate; 2) the molar ratio of sodium element in the sodium source to the metal element in the sodium ion cathode material precursor is 0.8-1.1:1; 3) the sodium ion battery cathode material precursor is selected from hydroxides containing element M, carbonates containing element M, or oxides containing element M, wherein element M is selected from Ni, Fe, Mn, Co, Ti, Cu, Ca, Zn, Mg, Al, Y, Ce, and Sr. 4) The sodium-ion battery cathode material precursor is selected from hydroxides containing element M, carbonates containing element M, or oxides containing element M, wherein M contains Ni and Mn; optionally, M further contains at least one of Fe, Ti, and Cu, and further optionally, M further contains at least one of Co, Ca, Zn, Mg, Al, Y, Ce, Sr, Sn, Ba, and La; 5) The calcination treatment conditions include: a temperature of 800-1100℃ and a time of 10-15h.

[0017] A fifth aspect of the present invention provides a sodium-ion battery, the sodium-ion battery comprising the sodium-ion battery cathode material described in the third aspect above or the sodium-ion battery cathode material prepared by the method described in the fourth aspect above.

[0018] The iron-manganese fluoride (chemical formula Fe) provided by this invention 1-β Mn β F2, where 0.5≤β<1), iron atoms are embedded in the manganese fluoride lattice to form a solid solution structure, which effectively improves the electronic conductivity of the material and avoids phase separation or interface defects that occur in the MnF2-FeF2 composite system. The iron-manganese fluoride provided by this invention is very suitable for use in sodium-ion battery cathode materials.

[0019] The sodium-ion battery cathode material provided by this invention has a core-shell structure (including a matrix material and a coating layer). Regarding structural stability, the F-Mn and F-Fe bonds in the coating layer not only inhibit the corrosion of active materials by hydrogen fluoride in the electrolyte and reduce the dissolution of manganese and iron, but also mitigate the degradation of Mn. 3+ The resulting Ginger-Taylor effect reduces lattice distortion; in terms of electrochemical performance, the coating can provide additional charge compensation and increase discharge voltage during sodium ion insertion / extraction, enabling the material to significantly extend cycle life while maintaining high specific capacity.

[0020] The method for preparing sodium-ion battery cathode materials provided by this invention is simple, highly operable, and easy to scale up for production. Attached Figure Description

[0021] Figure 1 shows the discharge specific capacity variation of the sodium-ion battery cathode materials prepared in Example 1, Comparative Example 1, and Comparative Example 2; Figure 2 is a SEM image of the iron-manganese fluoride prepared in Preparation Example A1; Figure 3 is a SEM image of the sodium-ion battery cathode material prepared in Example 1; Figure 4 is an XRD pattern of the iron-manganese fluoride prepared in Preparation Example A1; Figure 5 is an XRD pattern of the sodium-ion battery cathode material prepared in Example 1; Figure 6 is an EPMA surface distribution diagram of the cross-section of the sodium-ion battery cathode material prepared in Example 1. Detailed Implementation

[0022] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0023] It should be noted that, in all aspects of the present invention, the same components or terms in each aspect are described only once in one aspect and not repeatedly, and those skilled in the art should not understand this as a limitation of the present invention.

[0024] As used herein, “prepared from” is synonymous with “comprising”. The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof, as used herein, are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0025] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0026] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 1–5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0027] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0028] "Parts by mass" refers to the basic unit of measurement that expresses the mass ratio of multiple components. One part can represent any unit mass, such as 1g or 2.689g. If we say that component A has "a" parts by mass and component B has "b" parts by mass, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (where K is any number representing a multiplier). It is important to understand that, unlike parts by mass, the sum of the mass parts of all components is not limited to 100 parts.

[0029] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0030] In this invention, particle size D50 refers to the particle size corresponding to a cumulative particle size distribution percentage of 50% for the material. The particle size D50 of the cathode material is measured using a Malvern 3000 laser particle size analyzer.

[0031] In this invention, room temperature refers to a temperature of 25±2℃.

[0032] In this invention, the particle size D50 of iron-manganese fluoride refers to the particle size corresponding to a cumulative particle size distribution percentage of 50%. It is tested by wet laser diffraction with ethanol as the solvent. The iron-manganese fluoride is ultrasonicated for 5 minutes. The laser particle size analyzer parameters are set to a refractive index of 1.52 and an absorptivity of 0.1.

[0033] In this invention, the compaction density is tested using a tablet press (model UTM7305) with a test pressure of 3T, a holding time of 30s, and a pressurization speed of 2mm / min.

[0034] As previously stated, a first aspect of the present invention provides an iron-manganese fluoride, wherein the chemical formula of the iron-manganese fluoride is Fe. 1-β Mn β F2, where 0.5 ≤ β < 1.

[0035] In some embodiments, the chemical formula of the iron-manganese fluoride is Fe 1-β Mn β In F2, 0.9 ≤ β < 1, and the specific value of β can be any value between 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, < 1, or 0.9 ≤ β < 1.

[0036] In some embodiments, the compacted density of the iron-manganese fluoride is 3.0-4.0 g / cm³. 3 For example, it can be 3.0 g / cm³. 3 3.1 g / cm 3 3.3 g / cm 3 3.5 g / cm 3 3.8 g / cm 3 4.0 g / cm 3 Or 3.0-4.0 g / cm 3 Any value between.

[0037] In some embodiments, the particle size D50 of the iron-manganese fluoride is 100-500 nm, for example, it can be any value between 100 nm, 200 nm, 300 nm, 400 nm, 500 nm or 100-500 nm.

[0038] As mentioned above, a second aspect of the present invention provides a method for preparing the iron-manganese fluoride described in the first aspect, the method comprising the following steps: stirring and mixing a fluorine source, a manganese source and an iron source to obtain a mixture; and calcining the mixture under an inert atmosphere to obtain the iron-manganese fluoride.

[0039] In some embodiments, the method further includes: subjecting the calcined powder to preliminary crushing followed by sand milling, drying, and sieving to obtain the iron-manganese fluoride with a particle size D50 of 100-500 nm.

[0040] In some embodiments, the inert atmosphere includes nitrogen and / or helium.

[0041] In some embodiments, the conditions for the sand milling process include: a ball-to-material ratio of 1:2-4; a slurry solid content of 60-80 wt%; and a sand milling time of 5-7 h, wherein the slurry is prepared by mixing iron-manganese fluoride with water.

[0042] In some embodiments provided by this invention, highly crystalline, monodisperse nanostructured iron-manganese fluorides were successfully prepared by combining solid-state sintering and mechanical ball milling. Iron atoms are embedded in the manganese fluoride lattice to form a solid solution structure, effectively improving the electronic conductivity of the material and avoiding phase separation or interface defects that occur in the MnF2-FeF2 composite system.

[0043] In some embodiments, the fluorine source is selected from at least one of ammonium fluoride and manganese fluoride.

[0044] In some embodiments, the manganese source is selected from at least one of manganese carbonate, manganese oxide, and manganese oxalate.

[0045] In some embodiments, the iron source is selected from at least one of ferric oxide, ferric nitrate, and ferric fluoride.

[0046] In some embodiments, the conditions for the calcination treatment include: a temperature of 400-500°C, for example, any value between 400°C, 420°C, 450°C, 480°C, 500°C or 400-500°C; and a holding time of 4-8 hours, for example, any value between 4 hours, 5 hours, 6 hours, 7 hours, 8 hours or 4-8 hours.

[0047] In some embodiments, the calcination treatment conditions further include: heating from room temperature to 400-500°C at a heating rate of 1-3°C / min, for example, the heating rate can be any value between 1°C / min, 2°C / min, 3°C / min or 1-3°C / min.

[0048] As previously described, a third aspect of the present invention provides a sodium-ion battery cathode material, the sodium-ion battery cathode material comprising a matrix material and a coating layer covering at least a portion of the surface of the matrix material; the chemical formula of the coating layer is Fe. 1-β Mn β F2, where 0.5 ≤ β < 1.

[0049] The F-Mn and F-Fe bonds in the coating layer of the sodium-ion battery cathode material provided by this invention not only reduce the corrosion of active materials by hydrogen fluoride in the electrolyte and reduce the dissolution of manganese and iron, but also inhibit the growth of Mn. 3+ The resulting Ginger-Taylor effect reduces lattice distortion; furthermore, the coating layer provides additional charge compensation and increases discharge voltage during sodium ion insertion / extraction. This combination of structural design and functional regulation successfully solves the key problem of achieving both high specific capacity and long cycle life in layered oxide cathode materials.

[0050] In some embodiments, the chemical formula of the matrix material is Na. x MO2, where 0.8 < x < 1.1, and M is selected from at least one of Ni, Fe, Mn, Co, Ti, Cu, Ca, Zn, Mg, Al, Y, Ce, Sr, Sn, Ba, and La.

[0051] In this invention, the chemical formula of the matrix material is Na x In MO2, M is [M1b1M2b2M3b3...Mnbn], where M1, M2, M3...Mn are all different and are independently selected from one of Ni, Fe, Mn, Co, Ti, Cu, Ca, Zn, Mg, Al, Y, Ce, Sr, Sn, Ba, and La. b1, b2, b3...bn may be the same or different, and b1+b2+b3+...+bn=1.

[0052] In some embodiments, the matrix material has the chemical formula Na x In MO2, M comprises Ni and Mn.

[0053] In some embodiments, the matrix material has the chemical formula Na x In MO2, M comprises Ni and Mn, and M further comprises at least one of Fe, Ti and Cu.

[0054] In some embodiments, the matrix material has the chemical formula Na x In MO2, M comprises Ni and Mn, and M further comprises at least one of Fe, Ti and Cu, and M further comprises at least one of Co, Ca, Zn, Mg, Al, Y, Ce, Sr, Sn, Ba and La.

[0055] In some embodiments, the mass of the coating layer is 0.5-2.5 wt% based on the total mass of the matrix material, for example, it can be any value between 0.5 wt%, 0.8 wt%, 1.0 wt%, 1.2 wt%, 1.5 wt%, 1.7 wt%, 1.9 wt%, 2.0 wt%, 2.2 wt%, 2.4 wt%, 2.5 wt%, or 0.5-2.5 wt%; optionally, it can be 1-2 wt%.

[0056] In some embodiments, the D50 of the sodium-ion battery cathode material is 3-20 μm, for example, it can be any value between 3 μm, 5 μm, 8 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm or 3-20 μm.

[0057] In some embodiments, the sodium-ion battery cathode material is monocrystalline or polycrystalline.

[0058] In some embodiments, the thickness of the coating layer is H, where 0 < H ≤ 100 nm, and can be, for example, any value between >0 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm or greater than 0 and less than or equal to 100 nm.

[0059] The thickness of the coating layer refers to the thickness range of F element enrichment on the particle surface in the EPMA surface distribution map. The specific method is as follows: randomly select at least one positive electrode particle (e.g., 1, 2, 3, 4 or 5), randomly select N (e.g., 5, 10, 15 or 20) points on the outer periphery of the particle, measure the thickness of F element enrichment on the particle surface at each measurement point, and the comprehensive range value is the thickness of the coating layer.

[0060] In some embodiments, the matrix material is a layered oxide; optionally, the layered oxide has an O3 phase structure.

[0061] As previously stated, a fourth aspect of the present invention provides a method for preparing the sodium-ion battery cathode material described in the third aspect, the method comprising the following steps: mixing a coating material and a matrix material to obtain a mixture; sintering the mixture in an air atmosphere to obtain the sodium-ion battery cathode material; wherein the chemical formula of the coating material is Fe. 1-β Mn β F2, where 0.5 ≤ β < 1.

[0062] In some embodiments, the matrix material is prepared by calcining raw materials containing a sodium source and a precursor for a sodium-ion battery cathode material in an air atmosphere.

[0063] In some embodiments, the sintering conditions include: a temperature of 400-700°C, for example, a temperature of 400°C, 500°C, 600°C, 700°C or any value between 400-700°C; and a time of 3-6 hours, for example, a time of 3 hours, 4 hours, 5 hours, 6 hours or any value between 3 and 6 hours.

[0064] In some embodiments, the mass ratio of the coating material to the matrix material is (0.5-2.5):100, for example, it can be any value between 0.5:100, 0.8:100, 1.0:100, 1.2:100, 1.5:100, 1.7:100, 1.9:100, 2.0:100, 2.2:100, 2.4:100, 2.5:100 or (0.5-2.5):100.

[0065] In some embodiments, the sodium source is selected from at least one of sodium carbonate, sodium hydroxide, and sodium nitrate.

[0066] In some embodiments, the molar ratio of sodium in the sodium source to metal in the sodium ion cathode material precursor is (0.8-1.1):1, for example, it can be any value between 0.8:1, 0.9:1, 1.0:1, 1.1:1 or (0.8-1.1):1.

[0067] In some embodiments, the preparation method of the matrix material may also include post-processing methods known in the art, such as cooling, crushing, and sieving, so as to obtain the sodium-ion battery cathode material of better quality. The present invention will not elaborate further here, and those skilled in the art should not understand it as a limitation of the present invention.

[0068] In some embodiments, the sodium-ion battery cathode material precursor is selected from hydroxides containing element M, carbonates containing element M, or oxides containing element M, wherein element M is selected from at least one of Ni, Fe, Mn, Co, Ti, Cu, Ca, Zn, Mg, Al, Y, Ce, Sr, Sn, Ba, and La.

[0069] In some embodiments, the sodium-ion battery cathode material precursor is selected from hydroxides containing element M, carbonates containing element M, or oxides containing element M, wherein element M includes Ni and Mn.

[0070] In some embodiments, the sodium-ion battery cathode material precursor is selected from hydroxides containing element M, carbonates containing element M, or oxides containing element M, wherein element M includes Ni and Mn, and element M further includes at least one of Fe, Ti, and Cu.

[0071] In some embodiments, the sodium-ion battery cathode material precursor is selected from hydroxides containing element M, carbonates containing element M, or oxides containing element M, wherein element M contains Ni and Mn, and element M further contains at least one of Fe, Ti, and Cu, and element M further includes at least one of Co, Ca, Zn, Mg, Al, Y, Ce, Sr, Sn, Ba, and La.

[0072] In some embodiments, the calcination treatment conditions include: a temperature of 800-1100°C, for example, any value between 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C, or 800-1100°C; and a time of 10-15 hours, for example, any value between 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, or 10-15 hours.

[0073] According to a preferred embodiment, before the calcination treatment, the raw material containing the sodium source and the precursor of the sodium-ion battery cathode material is heated from room temperature to T1 and kept at T1 for 4-6 hours, for example, any value between 4 hours, 5 hours, 6 hours or 4-6 hours; wherein T1 = 400-600℃, specifically, it can be any value between 400℃, 500℃, 600℃ or 400-600℃.

[0074] As previously described, the fifth aspect of the present invention provides a sodium-ion battery, the sodium-ion battery comprising the sodium-ion battery cathode material described in the third aspect or the sodium-ion battery cathode material prepared by the method described in the fourth aspect.

[0075] The present invention also provides an electrical device, the electrical device comprising a sodium-ion battery as described in the fifth aspect above.

[0076] The present invention will be described in detail below through examples. Unless otherwise specified, the instruments, reagents, and materials involved in the following examples are all conventional instruments, reagents, and materials, which can be obtained through legitimate commercial channels. Unless otherwise stated, all reagents used are commercially available analytical grade products.

[0077] The following preparation examples from Series A and comparative preparation examples are used to illustrate the preparation of iron-manganese fluorides.

[0078] Preparation Example A1: Preparation of Fe 0.05 Mn 0.95The iron-manganese fluoride of F2 is prepared by mixing a fluorine source (ammonium fluoride), a manganese source (manganese carbonate), and an iron source (ferric oxide) in a molar ratio of F:Mn:Fe of 2.7:0.95:0.05. The mixture is then calcined under an inert atmosphere (nitrogen) (heated from room temperature to 500°C at a rate of 2°C / min, and held for 6 hours). The calcined powder is then initially crushed and subsequently subjected to sand milling (ball-to-powder ratio of 1:3, slurry solid content of 70 wt%, sand milling time of 6 hours), drying, and sieving to obtain the iron-manganese fluoride.

[0079] The compacted density of the iron-manganese fluoride prepared in this example is 3.4 g / cm³. 3 The particle size distribution of the iron-manganese fluoride prepared in Preparation Example A1 was tested by laser diffraction, and the results are shown in Table 1: Table 1 Particle size distribution of the iron-manganese fluoride prepared in Preparation Example A1

[0080] Preparation Example A2: Preparation of Fe 0.10 Mn 0.90 The iron-manganese fluoride of F2 was prepared using a method similar to that of Preparation Example A1, except that the amounts of fluorine source (ammonium fluoride), manganese source (manganese carbonate), and iron source (ferric oxide) were controlled so that the molar ratio of F:Mn:Fe was 2.7:0.90:0.10; all other parts were the same as in Preparation Example 1, and the iron-manganese fluoride was prepared.

[0081] Comparative Preparation Examples A-D1: Preparation of Fluorides with the Chemical Formula MnF2: Ammonium fluoride and manganese carbonate were mixed by stirring at a molar ratio of F:Mn of 1:1.3 to obtain a mixture. The mixture was then calcined under an inert atmosphere (nitrogen) (heated from room temperature to 500°C at a heating rate of 2°C / min, and held for 6 hours). The calcined powder was then initially crushed and subsequently subjected to sand milling (ball-to-powder ratio of 1:3, slurry solid content of 70 wt%, sand milling time of 6 hours), drying, and sieving to obtain the fluoride.

[0082] The following preparation examples from Series B and comparative preparation examples are used to illustrate the preparation of matrix materials.

[0083] Preparation Example B1: Preparation of Na 0.88 Ni 0.38 Fe 0.02 Mn 0.50 Ti 0.05 Zn 0.05The O2 matrix material is prepared by mixing sodium carbonate with nickel oxide, ferric oxide, manganese dioxide, titanium dioxide, and zinc oxide in an elemental molar ratio of Na:Ni:Fe:Mn:Ti:Zn of 0.88:0.38:0.02:0.50:0.05:0.05 to obtain a raw material containing a sodium source and a precursor for sodium-ion battery cathode materials. The raw material containing the sodium source and the precursor for sodium-ion battery cathode materials is calcined in an air atmosphere (heated to 980℃ at a rate of 1℃ / min and sintered for 15h), and then cooled in the furnace and crushed and sieved to obtain the matrix material.

[0084] Preparation Example B2: Preparation of Na 1.0 Ni 0.33 Fe 0.33 Mn 0.34 The matrix material for O2 is prepared by mixing sodium carbonate, nickel oxide, ferric oxide, and manganese dioxide in an elemental ratio of Na:Ni:Fe:Mn of 1:0.33:0.33:0.34 to obtain a raw material containing a sodium source and a precursor for sodium-ion battery cathode materials. Under an air atmosphere, the raw material containing the sodium source and the precursor for sodium-ion battery cathode materials is heated from room temperature to T1 (500℃) and held at T1 for 5 hours. Then, it is calcined (heated to 980℃ at a rate of 1℃ / min and sintered for 15 hours). After being cooled in the furnace, it is crushed and sieved to obtain the matrix material.

[0085] Examples 1-5 and Comparative Examples 1-3 are used to illustrate the preparation of sodium-ion battery cathode materials according to the formulation and process conditions in Table 1 and the following steps: (1) mixing the coating material and the matrix material to obtain a mixture; (2) sintering the mixture in an air atmosphere (heating to 500°C at a rate of 2°C / min and holding for 6 hours) to obtain sodium-ion battery cathode materials; Unless otherwise specified, Examples 1-5 are all carried out using similar methods as described above, except that the formulation and process are shown in Table 2, and sodium-ion battery cathode materials are prepared.

[0086] Table 2 Summary of formulations and sintering conditions for Examples 1-5 and Comparative Examples 1-3

[0087] Note: The " / " in the table indicates that the coating material is 0, meaning no coating is applied.

[0088] Test Example 11: The thickness range of the coating layer is referenced to the thickness range of F element enrichment on the particle surface in the EPMA surface distribution diagram (Figure 6). The specific method is as follows: randomly select at least one positive electrode particle (e.g., 1, 2, 3, 4 or 5), randomly select N (e.g., 5, 10, 15 or 20) points on the outer periphery of the particle, and measure the thickness of F element enrichment on the particle surface at each measurement point. The thickness H of the coating layer in the positive electrode material prepared in Example 1 is 0 < H ≤ 93 nm.

[0089] 2. The particle size D50 of the positive electrode material was tested using a Malvern 3000 laser particle size analyzer, referring to standard GB / T19077-2016; 3. pH value test: 5.0g of sodium-ion battery positive electrode material prepared in the above examples was weighed, 45.0g of deionized water was added, and the mixture was magnetically stirred for 10 min; then the pH value was measured using a pH meter (during the test, the electrode liquid level was ensured to be submerged 1 / 3-2 / 3 below the liquid surface, and the temperature was 25±1℃); (2) Residual sodium test: 10.0g of sodium-ion battery positive electrode material prepared in the above examples was weighed, 90.0g of deionized water was added, and the mixture was magnetically stirred for 10 min. The filtrate was collected by vacuum filtration; the filtrate was titrated using a potentiometric titrator, and the residual sodium (Na) in the sample was calculated based on the titration volume corresponding to the two isoelectric points in the titration curve. + The content of ).

[0090] The test results are shown in Table 3.

[0091] Table 3 Summary of test results for Examples 1-5 and Comparative Examples 1-3

[0092] Test Example 2: Electrochemical performance tests were conducted on the sodium-ion battery cathode materials prepared in the above examples. The specific methods are as follows: (1) Preparation of cathode sheet: Sodium-ion battery cathode material, conductive agent (Super) P) and binder (polyvinylidene fluoride, PVDF) were weighed in a mass ratio of 85:10:5, N-methylpyrrolidone (NMP) was added as a dispersion solvent, and the mixture was stirred evenly to form a slurry. The slurry was evenly coated on the aluminum foil current collector and then dried, rolled, and stamped to form a positive electrode sheet. (2) Sodium-ion battery assembly and testing: CR2032 button battery was used as the assembly shell. The positive electrode shell, stainless steel gasket, positive electrode sheet, glass fiber separator, electrolyte, sodium metal negative electrode, gasket, spring sheet and negative electrode shell were placed in sequence and then encapsulated and allowed to stand for activation. The electrochemical performance was tested at 25±1℃ using the Blue Battery Test System. The voltage range was 2.0-4.3V. The charge and discharge regime was: activated at 0.1C (1C=150mA / g) rate for 2 weeks, activated at 0.2C rate for 2 weeks, and finally tested at 1C rate for 50 cycles.

[0093] The test results are shown in Table 4.

[0094] Table 4 Summary of electrical performance test results for Examples 1-5 and Comparative Examples 1-3

[0095] The results above show that by applying the iron-manganese fluoride provided by this invention to the preparation of sodium-ion battery cathode materials, the obtained sodium-ion battery cathode materials have excellent electrochemical performance.

[0096] The present invention exemplarily provides, in Figure 1, the discharge specific capacity variation of the sodium-ion battery cathode materials prepared in Example 1, Comparative Example 1 and Comparative Example 2 at a 1C rate in the voltage range of 2.0-4.3V; as can be seen from Figure 1, the discharge specific capacity decay of the battery corresponding to Example 1 is slower, indicating that it has better cycle stability.

[0097] The present invention provides an exemplary SEM image of the iron-manganese fluoride prepared in the aforementioned preparation example A1 in Figure 2. As can be seen from Figure 2, the primary particles of the coated material are relatively fine.

[0098] The present invention provides an exemplary SEM image of the sodium-ion battery cathode material prepared in Example 1 in Figure 3. As can be seen from Figure 3, the material is a single crystal morphology.

[0099] The present invention exemplarily shows the XRD pattern of the iron-manganese fluoride prepared in the aforementioned preparation example A1 in Figure 4. As can be seen from Figure 4, the iron-manganese fluoride has no other impurity phases.

[0100] Figure 5 shows the XRD pattern of the sodium-ion battery cathode material prepared in Example 1. As can be seen from Figure 5, the main body of the material still retains the original O3 phase after the coating treatment, and no significant changes have occurred.

[0101] Figure 6 illustrates the EPMA surface distribution of the sodium-ion battery cathode material prepared in Example 1. As can be seen from Figure 6, fluorine is significantly enriched in the particle edge region. The electrochemically active F-Mn and F-Fe bonds contained in this coating layer can participate in electrochemical reactions and provide capacity, while also inhibiting the corrosion of active materials by HF in the electrolyte and reducing the dissolution of manganese and iron, thereby enhancing cycle stability while improving capacity.

[0102] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. An iron-manganese fluoride, characterized in that, The chemical formula of the iron-manganese fluoride is Fe. 1-β Mn β F2, where 0.5 ≤ β < 1.

2. The iron-manganese fluoride according to claim 1, characterized in that, The iron-manganese fluoride satisfies at least one of the following conditions: ① the chemical formula of the iron-manganese fluoride is Fe 1-β Mn β In F2, 0.9 ≤ β < 1; ② The compacted density of the iron-manganese fluoride is 3.0-4.0 g / cm³. 3 ③ The particle size D50 of the iron-manganese fluoride is 100-500 nm.

3. A method for preparing the iron-manganese fluoride according to claim 1 or 2, characterized in that, The method includes the following steps: stirring and mixing a fluorine source, a manganese source and an iron source to obtain a mixture; calcining the mixture under an inert atmosphere to obtain the iron-manganese fluoride.

4. The preparation method according to claim 3, characterized in that, The preparation method satisfies at least one of the following conditions: (i) the fluorine source is selected from at least one of ammonium fluoride and manganese fluoride; (ii) the manganese source is selected from at least one of manganese carbonate, manganese oxide, and manganese oxalate; (iii) the iron source is selected from at least one of ferric oxide, ferric nitrate, and ferric fluoride; (iv) the calcination treatment conditions include: a temperature of 400-500℃ and a holding time of 4-8h.

5. A sodium-ion battery cathode material, characterized in that, The sodium-ion battery cathode material comprises a matrix material and a coating layer covering at least a portion of the surface of the matrix material; the chemical formula of the coating layer is Fe. 1-β Mn β F2, where 0.5 ≤ β < 1.

6. The sodium-ion battery cathode material according to claim 5, characterized in that, The sodium-ion battery cathode material satisfies at least one of the following conditions: A. The chemical formula of the matrix material is Na x MO2, where 0.8 < x < 1.1, and M is selected from at least one of Ni, Fe, Mn, Co, Ti, Cu, Ca, Zn, Mg, Al, Y, Ce, Sr, Sn, Ba, and La; B, based on the total mass of the matrix material, the mass of the coating layer is 0.5-2.5 wt%, optionally 1-2 wt%; C, the D50 of the sodium-ion battery cathode material is 3-20 μm; D, the sodium-ion battery cathode material is single crystal or polycrystalline; E, the thickness of the coating layer is H, 0 < H ≤ 100 nm; F, the matrix material is a layered oxide; optionally, the layered oxide has an O3 phase structure; G, the chemical formula of the matrix material is Na. x MO2, wherein 0.8 < x < 1.1, and M comprises Ni and Mn; optionally, M further comprises at least one of Fe, Ti and Cu, and even more optionally, M further comprises at least one of Co, Ca, Zn, Mg, Al, Y, Ce, Sr, Sn, Ba and La.

7. A method for preparing the sodium-ion battery cathode material according to claim 5 or 6, characterized in that, The method includes the following steps: mixing a coating material and a matrix material to obtain a mixture; sintering the mixture in an air atmosphere to obtain the sodium-ion battery cathode material; the chemical formula of the coating material is Fe. 1-β Mn β F2, where 0.5 ≤ β < 1.

8. The method according to claim 7, characterized in that, The preparation method satisfies at least one of the following conditions: a) the matrix material is obtained by calcining raw materials containing a sodium source and a sodium-ion battery cathode material precursor in an air atmosphere; b. The sintering conditions include: a temperature of 400-700℃ and a time of 3-6 hours; c. The mass ratio of the coating material to the matrix material is 0.5-2.5:

100.

9. The preparation method according to claim 8, characterized in that, The preparation method satisfies at least one of the following conditions: 1) The sodium source is selected from at least one of sodium carbonate, sodium hydroxide, and sodium nitrate; 2) The molar ratio of sodium element in the sodium source to metal element in the sodium ion cathode material precursor is 0.8-1.1:1; 3) The sodium ion battery cathode material precursor is selected from hydroxides containing element M, carbonates containing element M, or oxides containing element M, wherein element M is selected from at least one of Ni, Fe, Mn, Co, Ti, Cu, Ca, Zn, Mg, Al, Y, Ce, Sr, Sn, Ba, and La; 4) The sodium ion battery cathode material precursor is selected from hydroxides containing element M, carbonates containing element M, or oxides containing element M, wherein M contains Ni and Mn; optionally, M further contains at least one of Fe, Ti, and Cu, and further optionally, M also contains at least one of Co, Ca, Zn, Mg, Al, Y, Ce, Sr, Sn, Ba, and La; 5) The calcination conditions include: a temperature of 800-1100℃ and a time of 10-15h.

10. A sodium-ion battery, characterized in that, The sodium-ion battery includes the sodium-ion battery cathode material according to any one of claims 5-6 or the sodium-ion battery cathode material prepared by the method according to any one of claims 7-9.

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