Fluorine ion and / or vacancy doped sodium battery cathode material, preparation method and application

Abstract

The application relates to a sodium battery positive electrode material doped with fluorine ions and / or vacancies, a preparation method and application. In the sodium ion battery positive electrode material, part of fluorine ions and / or vacancies occupy oxygen sites to replace oxygen ions, ions of transition metal sites form an octahedral structure with six adjacent oxygen and / or fluorine and / or vacancies, and are alternately arranged with a sodium ion layer in octahedral coordination to form an O3 type layered oxide material with a space group of R-3m; the chemical general formula of the positive electrode material is: Na x M a Cu b Fe c Mn d 0 2‑e F e1 □ e2 ; wherein Cu, Fe and Mn are transition metal elements, M is an ion and / or vacancy doped and substituted to the transition metal site, F is a negative monovalent fluorine ion, and □ is a vacancy occupying an oxygen site; 0.76<=x<=1, 0 The doping of fluorine ions and / or vacancies to oxygen sites can improve the structural stability and intrinsic ion conduction and electron conduction of the positive electrode material in the charging and discharging process, and in-situ induce a coating layer of transition metal oxide on the surface of the material particles.

Description

Technical Field

[0001] This invention relates to the field of materials technology, and in particular to a sodium battery cathode material doped with fluorine ions and / or vacancy, its preparation method, and its application. Background Technology

[0002] Sodium-ion layered oxides have been extensively studied due to their relative ease of synthesis, tunable voltage range, and high specific capacity. Although these materials have not yet achieved the same level of electrochemical performance as lithium-ion layered materials, the numerous reported stable phases of sodium-ion layered oxides offer hope for finding competitive sodium-ion cathode materials from both performance and cost perspectives. Therefore, future research aims to improve the electrochemical performance of sodium-ion layered oxides while maintaining their price advantage. This requires developing compositions rich in inexpensive and abundant transition metal ions. Copper-iron-manganese layered oxide materials are very low-cost, with the constituent elements sodium, copper, iron, and manganese being far cheaper than elements such as nickel, cobalt, and vanadium, offering a possibility for the large-scale production and application of sodium-ion batteries.

[0003] However, this material exhibits low reversible specific capacity and energy density. While further optimization of the composition and increase of its operating voltage can significantly improve its energy density, the material's structure suffers noticeable fatigue damage during long-cycle charge-discharge processes. Therefore, further modification studies are needed to improve its overall electrochemical performance. Summary of the Invention

[0004] This invention provides a sodium battery cathode material doped with fluoride ions and / or vacancies, its preparation method, and its application. Through compositional optimization design, a small amount of fluoride ions and / or vacancies are used to replace oxygen ions in the material to significantly improve the structural stability, sodium ion conductivity, and electronic conductivity of the material.

[0005] In a first aspect, embodiments of the present invention provide a sodium-ion battery cathode material doped with fluoride ions and / or vacancies. In the sodium-ion battery cathode material doped with fluoride ions and / or vacancies, some fluoride ions and / or vacancies occupy oxygen sites to replace oxygen ions. Ions at transition metal sites form an octahedral structure with six adjacent oxygen and / or fluoride and / or vacancies, and are alternately arranged with octahedral coordinated sodium ion layers to form an O3-type layered oxide material with space group R-3m.

[0006] The general chemical formula of the sodium-ion battery cathode material is: Na x M a Cu b Fe c Mn d 0 2-e F e1 □ e2Wherein, Cu, Fe, and Mn are transition metal elements, M is an ion and / or vacancy that dopes and substitutes for the transition metal site, F is a negative monovalent fluoride ion, and □ is a vacancy occupying an oxygen site; 0.76≤x≤1, 0<a≤0.5, 0<b≤0.4, 0≤c≤0.4, 0.1≤d≤0.6, 0<e≤0.1, e=e1+e2;

[0007] The doping of oxygen sites with fluorine ions and / or vacancies is used to improve the structural stability and intrinsic ion and electronic conduction of the sodium-ion battery cathode material during charge and discharge, and to induce the formation of a transition metal oxide coating layer in situ on the surface of the material particles.

[0008] Preferably, the ions that substitute for the transition metal sites specifically include: Li + Mg 2+ Ca 2+ Ni 2+ Zn 2+ Ba 2+ Ni 3+ Al 3+ B 3+ Cr 3+ Co 3+ V 3+ Y 3+ Ti 4+ Zr 4+ Sn 4+ Si 4+ Mo 4+ 、Nb 5+ Sb 5+ Mo 5+ Te 6+ One or more of them.

[0009] Secondly, embodiments of the present invention provide a method for preparing the sodium-ion battery cathode material described in the first aspect, wherein the preparation method is a solid-state method, comprising:

[0010] Step 1: Mix 100wt%-105wt% sodium source, 0% or the required stoichiometric amount of fluorine source, and the required stoichiometric amount of transition metal oxide, hydroxide or nitrate in proportion, and grind, ball mill or sand mill evenly to obtain precursor powder.

[0011] Step 2: Place the obtained precursor powder in a crucible and calcine it at 700℃-950℃ for 10-24 hours in an air or oxygen sintering atmosphere. Then grind the heat-treated material.

[0012] And, including or excluding: step 3, quenching the ground sample or calcining it again in an inert atmosphere at 200℃-900℃ for 10-120 minutes to form vacancy doping of oxygen sites;

[0013] Wherein, when the amount of fluorine source added is 0%, the preparation method includes step 3; when the amount of fluorine source added is not 0% but is the required stoichiometry, the preparation method may or may not include step 3.

[0014] Preferably, the sodium source includes one or more of sodium carbonate, sodium nitrate, sodium peroxide, sodium superoxide, sodium hydroxide, or sodium oxalate;

[0015] The fluorine source includes sodium fluoride and / or ammonium fluoride;

[0016] The transition metal includes at least Cu and Mn, as well as ions and / or vacancies that dope and substitute at the transition metal sites, and may or may not include Fe; the ions that dope and substitute at the transition metal sites specifically include: Li + Mg 2+ Ca 2+ Ni 2+ Zn 2+ Ba 2+ Ni 3+ Al 3+ B 3+ Cr 3+ Co 3+ V 3+ Y 3+ Ti 4+ Zr 4+ Sn 4+ Si 4+ Mo 4+ 、Nb 5+ Sb 5+ Mo 5+ Te 6+ One or more of them.

[0017] Thirdly, embodiments of the present invention provide a method for preparing the sodium-ion battery cathode material described in the first aspect, wherein the preparation method is a spray drying method, comprising:

[0018] Step 1: Mix 100wt%-105wt% sodium source, 0% or the required stoichiometric amount of fluorine source, and the required stoichiometric amount of transition metal oxide, hydroxide or nitrate in proportion to form a precursor.

[0019] Step 2: Add ethanol or water to the precursor and stir until homogeneous to form a slurry. Inject the resulting slurry into a spray dryer for spray drying to obtain the precursor.

[0020] Step 3: Place the obtained precursor in a crucible and pretreat it at 250-500℃ for 1-5 hours. Then grind the pretreated powder and place it in a crucible to treat it at 700-950℃ for 10-24 hours.

[0021] And, including or excluding: step 4, quenching the ground sample or calcining it again in an inert atmosphere at 200℃-900℃ for 10-120 minutes to form vacancy doping of oxygen sites.

[0022] Wherein, when the amount of fluorine source added is 0%, the preparation method includes step 4; when the amount of fluorine source added is not 0% but is the required stoichiometry, the preparation method may or may not include step 4.

[0023] Preferably, the sodium source includes one or more of sodium carbonate, sodium nitrate, sodium peroxide, sodium superoxide, sodium hydroxide, or sodium oxalate;

[0024] The fluorine source includes sodium fluoride and / or ammonium fluoride;

[0025] The transition metal includes at least Cu and Mn, as well as ions and / or vacancies that dope and substitute at the transition metal sites, and may or may not include Fe; the ions that dope and substitute at the transition metal sites specifically include: Li + Mg 2+ Ca 2+ Ni 2+ Zn 2+ Ba 2+ Ni 3+ Al 3+ B 3+ Cr 3+ Co 3+ V 3+ Y 3+ Ti 4+ Zr 4+ Sn 4+ Si 4+ Mo 4+ 、Nb 5+ Sb 5+ Mo 5+ Te 6+ One or more of them.

[0026] Fourthly, embodiments of the present invention provide a method for preparing the sodium-ion battery cathode material described in the first aspect, wherein the preparation method is a sol-gel method, comprising:

[0027] Step 1: Weigh out 100wt%-105wt% of sodium salt, 0% or the required stoichiometric amount of fluoride salt, the required stoichiometric amount of soluble salt of transition metal ions, and an appropriate amount of citric acid according to the required stoichiometric ratio, and dissolve them in deionized water to form a slurry.

[0028] Step 2: Heat the obtained slurry in an oil bath to evaporate it and form a dry gel;

[0029] Step 3: Place the obtained dry gel in a crucible and pre-treat it at 400℃-500℃ for 3-6 hours. Then grind the powder obtained from the pre-treatment, compress it into tablets, place them in a crucible, and calcine them at 700℃-900℃ in an air or oxygen atmosphere for 10-24 hours.

[0030] And, including or excluding: step 4, quenching the ground sample or calcining it again in an inert atmosphere at 200℃-900℃ for 10-120 minutes to form vacancy doping of oxygen sites.

[0031] Wherein, when the amount of fluoride added is 0%, the preparation method includes step 4; when the amount of fluoride added is not 0% but is the required stoichiometry, the preparation method may or may not include step 4.

[0032] Preferably, the sodium salt includes one or more of sodium carbonate, sodium nitrate, or sodium oxalate;

[0033] The fluoride salt includes sodium fluoride and / or ammonium fluoride;

[0034] The transition metal includes at least Cu and Mn, as well as ions and / or vacancies that dope and substitute at the transition metal sites, and may or may not include Fe; the ions that dope and substitute at the transition metal sites specifically include: Li + Mg 2+ Ca 2+ Ni 2+ Zn 2+ Ba 2+ Ni 3+ Al 3+ B 3+ Cr 3+ Co 3+ V 3+ Y 3+ Ti 4+ Zr 4+ Sn 4+ Si 4+ Mo 4+ 、Nb 5+ Sb 5+ Mo 5+ Te 6+ One or more of them.

[0035] Fifthly, embodiments of the present invention provide a positive electrode material for sodium-ion batteries comprising the fluorine ion and / or vacancy-doped material described in the first aspect above.

[0036] Sixthly, embodiments of the present invention provide a sodium-ion secondary battery including the positive electrode described in the fifth aspect above.

[0037] This invention, through compositional optimization design, produces a sodium-ion battery O3-type layered oxide cathode material doped with fluoride ions and / or vacancies, replacing oxygen ions with a small amount of fluoride ions and / or vacancies. This material offers the following advantages: 1) The substitution of some oxygen ions in the layered oxide with fluoride ions and / or vacancies significantly improves the structural stability of the material. The stronger bonding energy between fluoride ions and transition metal ions makes the material structure after sodium removal more stable and can suppress the dissolution of transition metal ions and the formation of stacking faults; 2) Fluoride ion and / or vacancy doping improves the sodium ion conductivity and electronic conductivity of the material; 3) Fluoride ion and / or vacancy doping induces the formation of a transition metal oxide coating layer on the surface of material particles in situ, which can effectively suppress the corrosion of the electrode material by the products of electrolyte side reactions and improve the long-cycle stability of the material. The fluoride ion and / or vacancy doped layered oxide material of this invention is simple to prepare. The transition metals copper, iron, and manganese contained in this invention are all safe and non-toxic elements with high abundance in the Earth's crust, thus resulting in low synthesis costs. Sodium-ion secondary batteries using the fluorine ion and / or vacancy-doped layered oxide cathode material of this invention can be used as large-scale energy storage devices for solar power generation, wind power generation, smart grid peak shaving, distributed power stations, backup power supplies, or communication base stations. Attached Figure Description

[0038] The technical solutions of the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples.

[0039] Figure 1 The X-ray diffraction (XRD) patterns are shown for the fluorine-doped sodium-ion battery O3-type layered oxide cathode materials prepared in Examples 1-3 of the present invention and the O3 layered oxide cathode material without fluorine doping in Comparative Example 1.

[0040] Figure 2 The X-ray diffraction (XRD) patterns are shown for the fluorine-doped sodium-ion battery O3-type layered oxide cathode material prepared in Examples 5-8 of this invention and the O3 layered oxide cathode material without fluorine doping in Comparative Example 2.

[0041] Figure 3 This is a scanning electron microscope (SEM) image of the fluorine-doped sodium-ion battery O3-type layered oxide cathode material prepared in Example 5 of the present invention.

[0042] Figure 4This is a SEM image of the fluorine-doped sodium-ion battery O3-type layered oxide cathode material prepared in Example 6 of the present invention.

[0043] Figure 5 This is an EDS surface scan of the fluorine-doped sodium-ion battery O3-type layered oxide cathode material prepared in Example 6 of the present invention.

[0044] Figure 6 This is a SEM image of the fluorine-doped sodium-ion battery O3-type layered oxide cathode material prepared in Example 8 of the present invention.

[0045] Figure 7 This is a SEM image of the O3 layered oxide cathode material without fluorine ion doping prepared in Comparative Example 2 of this invention.

[0046] Figure 8 Cycle performance curves of the fluorine-doped sodium-ion battery O3-type layered oxide cathode material prepared in Example 6 of the present invention and the O3 layered oxide cathode material without fluorine doping in Comparative Example 2 in half-cell tests.

[0047] Figure 9 Rate performance curves of the fluorine-doped sodium-ion battery O3-type layered oxide cathode material prepared in Example 6 of the present invention and the O3 layered oxide cathode material without fluorine doping in Comparative Example 2 in half-cell tests.

[0048] Figure 10 Cyclic performance curves of the fluorine-doped sodium-ion battery O3-type layered oxide cathode material prepared in Example 8 of the present invention and the O3 layered oxide cathode material without fluorine doping in Comparative Example 3 in half-cell tests.

[0049] Figure 11 Cycle performance curves of the vacancy-doped sodium-ion battery O3-type layered oxide cathode material prepared in Example 11 of this invention and the undoped O3 layered oxide cathode material in Comparative Example 2 in half-cell testing. Detailed Implementation

[0050] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, it should be understood that these embodiments are only for more detailed description and should not be construed as limiting the present invention in any way, that is, not intended to limit the scope of protection of the present invention.

[0051] This invention proposes a sodium-ion battery cathode material doped with fluorine ions and / or vacancies, with the general chemical formula: Na x M a Cu b Fe c Mn d 02-e F e1 □ e2 Wherein, Cu, Fe, and Mn are transition metal elements, M is an ion and / or vacancy that dopes and substitutes at the transition metal site, F is a monovalent fluorine ion, and □ is a vacancy occupying an oxygen site; 0.76≤x≤1, 0<a≤0.5, 0<b≤0.4, 0≤c≤0.4, 0.1≤d≤0.6, 0<e≤0.1, e=e1+e2; the ions that dope and substitute at the transition metal site specifically include: Li + Mg 2+ Ca 2+ Ni 2+ Zn 2+ Ba 2+ Ni 3+ Al 3+ B 3+ Cr 3+ Co 3+ V 3+ Y 3+ Ti 4+ Zr 4+ Sn 4+ Si 4+ Mo 4+ 、Nb 5+ Sb 5+ Mo 5+ Te 6+ One or more of them.

[0052] In the cathode material, the sodium-ion battery cathode material doped with fluorine ions and / or vacancies has some fluorine ions and / or vacancies occupying oxygen sites and replacing oxygen ions. The ions at the transition metal sites form an octahedral structure with the six adjacent oxygen and / or fluorine and / or vacancies, and are alternately arranged with the sodium ion layer coordinated to the octahedron, forming an O3-type layered oxide material with space group R-3m.

[0053] This invention, through compositional optimization design, produces a sodium-ion battery O3-type layered oxide cathode material doped with fluoride ions and / or vacancies, replacing oxygen ions with a small amount of fluoride ions and / or vacancies. This material offers the following advantages: 1) The substitution of some oxygen ions in the layered oxide with fluoride ions and / or vacancies significantly improves the structural stability of the material. The stronger bonding energy between fluoride ions and transition metal ions makes the material structure after sodium removal more stable and can suppress the dissolution of transition metal ions and the formation of stacking faults; 2) Fluoride ion and / or vacancy doping improves the sodium ion conductivity and electronic conductivity of the material; 3) Fluoride ion and / or vacancy doping induces the formation of a transition metal oxide coating layer on the surface of material particles in situ, which can effectively suppress the corrosion of the electrode material by the products of electrolyte side reactions and improve the long-cycle stability of the material. The fluoride ion and / or vacancy doped layered oxide material of this invention is simple to prepare. The transition metals copper, iron, and manganese contained in this invention are all safe and non-toxic elements with high abundance in the Earth's crust, thus resulting in low synthesis costs. Sodium-ion secondary batteries using the fluorine ion and / or vacancy-doped layered oxide cathode material of this invention can be used as large-scale energy storage devices for solar power generation, wind power generation, smart grid peak shaving, distributed power stations, backup power supplies, or communication base stations.

[0054] The cathode material proposed in this invention can be prepared by solid-state method, spray drying method or sol-gel method.

[0055] Solid-state methods include:

[0056] Step 1: Mix 100wt%-105wt% sodium source, 0% or the required stoichiometric amount of fluorine source, and the required stoichiometric amount of transition metal oxide, hydroxide or nitrate in proportion, and grind, ball mill or sand mill evenly to obtain precursor powder.

[0057] Step 2: Place the obtained precursor powder in a crucible and calcine it at 700℃-950℃ for 10-24 hours in an air or oxygen sintering atmosphere. Then grind the heat-treated material.

[0058] And, including or excluding: step 3, quenching the ground sample or calcining it again in an inert atmosphere at 200℃-900℃ for 10-120 minutes to form vacancy doping of oxygen sites.

[0059] When the amount of fluorine source added is 0%, the preparation method includes step 3; when the amount of fluorine source added is not 0% but is the required stoichiometry, the preparation method may or may not include step 3.

[0060] Spray drying methods include:

[0061] Step 1: Mix 100wt%-105wt% sodium source, 0% or the required stoichiometric amount of fluorine source, and the required stoichiometric amount of transition metal oxide, hydroxide or nitrate in proportion to form a precursor.

[0062] Step 2: Add ethanol or water to the precursor and stir until homogeneous to form a slurry. Inject the resulting slurry into a spray dryer for spray drying to obtain the precursor.

[0063] Step 3: Place the obtained precursor in a crucible and pretreat it at 250-500℃ for 1-5 hours. Then grind the pretreated powder and place it in a crucible to treat it at 700-950℃ for 10-24 hours.

[0064] And, including or excluding: step 4, quenching the ground sample or calcining it again in an inert atmosphere at 200℃-900℃ for 10-120 minutes to form vacancy doping of oxygen sites.

[0065] When the amount of fluorine source added is 0%, the preparation method includes step 4; when the amount of fluorine source added is not 0% but is the required stoichiometry, the preparation method may or may not include step 4.

[0066] In the above solid-state method and spray drying method, the sodium source includes one or more of sodium carbonate, sodium nitrate, sodium peroxide, sodium superoxide, sodium hydroxide, or sodium oxalate; the fluorine source includes sodium fluoride and / or ammonium fluoride; the transition metal includes at least Cu and Mn, as well as ions and / or vacancies that dope and substitute at the transition metal sites, and optionally includes or excludes Fe; the ions that dope and substitute at the transition metal sites specifically include: Li + Mg 2+ Ca 2+ Ni 2+ Zn 2+ Ba 2+ Ni 3+ Al 3+ B 3+ Cr 3+ Co 3+ V 3+ Y 3+ Ti 4+ Zr 4+ Sn 4+ Si 4+ Mo 4+ 、Nb 5+ Sb 5+ Mo 5+ Te 6+ One or more of them.

[0067] Sol-gel method, including:

[0068] Step 1: Weigh out 100wt%-105wt% of sodium salt, 0% or the required stoichiometric amount of fluoride salt, the required stoichiometric amount of soluble salt of transition metal ions, and an appropriate amount of citric acid according to the required stoichiometric ratio, and dissolve them in deionized water to form a slurry.

[0069] Step 2: Heat the obtained slurry in an oil bath to evaporate it and form a dry gel;

[0070] Step 3: Place the obtained dry gel in a crucible and pre-treat it at 400℃-500℃ for 3-6 hours. Then grind the powder obtained from the pre-treatment, compress it into tablets, place them in a crucible, and calcine them at 700℃-900℃ in an air or oxygen atmosphere for 10-24 hours.

[0071] And, including or excluding: step 4, quenching the ground sample or calcining it again in an inert atmosphere at 200℃-900℃ for 10-120 minutes to form vacancy doping of oxygen sites.

[0072] When the amount of fluoride added is 0%, the preparation method includes step 4; when the amount of fluoride added is not 0% but is the required stoichiometry, the preparation method may or may not include step 4.

[0073] Sodium salts include one or more of sodium carbonate, sodium nitrate, or sodium oxalate; fluoride salts include sodium fluoride and / or ammonium fluoride; transition metals include at least Cu and Mn, and ions and / or vacancies doped at the transition metal sites, optionally including or excluding Fe; ions doped at the transition metal sites specifically include: Li + Mg 2+ Ca 2+ Ni 2+ Zn 2+ Ba 2+ Ni 3 + Al 3+ B 3+ Cr 3+ Co 3+ V 3+ Y 3+ Ti 4+ Zr 4+ Sn 4+ Si 4+ Mo 4+ 、Nb 5+ Sb 5+ Mo 5+ Te 6+ One or more of them.

[0074] The preparation method provided by this invention is simple and low-cost, and can synthesize pure-phase fluoride- and / or vacancy-doped layered oxide materials. Fluoride ions and / or vacancies effectively enter the material lattice to replace oxygen ions. This results in superior structural stability of the sodium-ion battery O3-type layered oxide cathode material. The stronger bonding energy between fluoride ions and transition metal ions makes the desodium-phase material structure more stable and reversible, and can suppress the dissolution of transition metal ions and the formation of stacking faults. Simultaneously, fluoride ion and / or vacancy doping improves the sodium-ion conductivity and electronic conductivity of the material. Fluoride ion and / or vacancy doping induces the in-situ formation of a transition metal oxide coating layer on the surface of the material particles, which can effectively suppress the corrosion of the electrode material by electrolyte side reaction products and improve the long-cycle stability of the material.

[0075] To better understand the technical solutions provided by the present invention, the following uses several specific examples to illustrate the specific process of preparing sodium battery cathode materials using the methods provided in the above embodiments of the present invention, as well as the methods and characteristics of applying them to sodium-ion batteries.

[0076] Example 1

[0077] This embodiment uses a high-temperature solid-state method to prepare fluorine-doped sodium-ion battery O3-type layered oxide cathode material Na. 0.9 Cu 0.17 Ni 0.05 Fe 0.3 Mn 0.48 O 1.99 F 0.01 The specific steps include: weighing Na2CO3 (2% excess), NaF, NiO, CuO, Fe2O3, and Mn2O3 into an agate mortar according to the stoichiometric ratio, adding an appropriate amount of anhydrous ethanol, mixing and grinding evenly to obtain a precursor, treating the precursor in a muffle furnace at 900°C in air atmosphere for 15 hours, and then cooling to room temperature to obtain the fluorine-doped sodium-ion battery O3-type layered oxide cathode material Na. 0.9 Cu 0.17 Ni 0.05 Fe 0.3 Mn 0.48 O 1.99 F 0.01 .

[0078] The XRD pattern of the fluorine-doped sodium-ion battery O3-type layered oxide cathode material prepared in this embodiment is as follows: Figure 1 As shown, by comparing with the standard card, it can be seen that its main phase is a pure O3 phase substance with space group R-3m, and it contains trace amounts of copper oxide impurity phase.

[0079] Example 2

[0080] This embodiment uses a high-temperature solid-state method to prepare fluorine-doped sodium-ion battery O3-type layered oxide cathode material Na. 0.9 Cu 0.17 Ni 0.05 Fe 0.3 Mn 0.48 O 1.98 F 0.02 The specific steps include: weighing Na₂CO₃ (2% excess), NaF, CuO, NiO, Fe₂O₃, and Mn₂O₃ into an agate mortar according to the stoichiometric ratio, adding an appropriate amount of anhydrous ethanol, mixing and grinding evenly to obtain a precursor, treating the precursor in a muffle furnace at 900°C in air atmosphere for 15 hours, and then cooling to room temperature to obtain the fluorine-doped sodium-ion battery O₃-type layered oxide cathode material Na. 0.9 Cu 0.17 Ni 0.05 Fe 0.3 Mn 0.48 O 1.98 F 0.02 .

[0081] The XRD pattern of the fluorine-doped sodium-ion battery O3-type layered oxide cathode material prepared in this embodiment is as follows: Figure 1 As shown, by comparing with the standard card, it can be seen that its main phase is a pure O3 phase substance with space group R-3m, and it contains trace amounts of copper oxide impurity phase.

[0082] Example 3

[0083] This embodiment uses a high-temperature solid-state method to prepare fluorine-doped sodium-ion battery O3-type layered oxide cathode material Na. 0.9 Cu 0.17 Ni 0.05 Fe 0.3 Mn 0.48 O 1.97 F 0.03 The specific steps include: weighing Na₂CO₃ (2% excess), NaF, CuO, NiO, Fe₂O₃, and Mn₂O₃ into an agate mortar according to the stoichiometric ratio, adding an appropriate amount of anhydrous ethanol, mixing and grinding evenly to obtain a precursor, treating the precursor in a muffle furnace at 900°C in air atmosphere for 15 hours, and then cooling to room temperature to obtain the fluorine-doped sodium-ion battery O₃-type layered oxide cathode material Na. 0.9 Cu 0.17 Ni 0.05 Fe 0.3 Mn 0.48 O 1.97 F 0.03 .

[0084] The XRD pattern of the fluorine-doped sodium-ion battery O3-type layered oxide cathode material prepared in this embodiment is as follows: Figure 1 As shown in the diagram, comparison with the standard card reveals that the main phase is a pure O3 phase with space group R-3m, and it contains a small amount of copper oxide impurities. This indicates that fluorine ions have been doped into the lattice of the layered oxide particles, leading to a decrease in the solid solubility of copper ions. However, the in-situ induced CuO coating layer can effectively prevent the corrosion of the electrode material by electrolyte decomposition byproducts. Therefore, an appropriate amount of oxide coating layer will be beneficial to improving the electrochemical performance of the material.

[0085] Example 4

[0086] This embodiment uses a high-temperature solid-state method to prepare fluorine-doped sodium-ion battery O3-type layered oxide cathode material Na. 0.9 Li 0.05 Cu 0.22 Fe 0.3 Mn 0.43 O 1.98 F 0.02 The specific steps include: weighing Na₂CO₃ (2% excess), NaF, LiOH, CuO, Fe₂O₃, and Mn₂O₃ into an agate mortar according to the stoichiometric ratio, adding an appropriate amount of anhydrous ethanol, mixing and grinding evenly to obtain a precursor, treating the precursor in a muffle furnace at 900°C in air atmosphere for 15 hours, and then cooling to room temperature to obtain the fluorine-doped sodium-ion battery O₃-type layered oxide cathode material Na. 0.9 Li 0.05 Cu 0.22 Fe 0.3 Mn 0.43 O 1.98 F 0.02 .

[0087] The XRD pattern of the fluorine-doped sodium-ion battery O3-type layered oxide cathode material prepared in this embodiment is as follows: Figure 1 As shown, by comparing with the standard card, it can be seen that the main phase is a pure O3 phase substance with space group R-3m, and contains trace amounts of copper oxide impurity phase.

[0088] Example 5

[0089] This embodiment uses a high-temperature solid-state method to prepare fluorine-doped sodium-ion battery O3-type layered oxide cathode material Na. 0.9 Li 0.05 Cu 0.15 Ni 0.07 Fe 0.3 Mn 0.43 O 1.98 F 0.02The specific steps include: weighing Na2CO3 (2% excess), NaF, LiOH, CuO, NiO, Fe2O3, and Mn2O3 into an agate mortar according to the stoichiometric ratio, adding an appropriate amount of anhydrous ethanol, mixing and grinding evenly to obtain a precursor, treating the precursor in a muffle furnace at 900°C in air atmosphere for 15 hours, and then cooling to room temperature to obtain the fluorine-doped sodium-ion battery O3-type layered oxide cathode material Na. 0.9 Li 0.05 Cu 0.15 Ni 0.07 Fe 0.3 Mn 0.43 O 1.98 F 0.02 .

[0090] The XRD pattern of the fluorine-doped sodium-ion battery O3-type layered oxide cathode material prepared in this embodiment is as follows: Figure 2 As shown, comparison with the standard card reveals that its main phase is a pure O3 phase, space group R-3m, and it contains trace amounts of copper oxide impurities. SEM images are shown below. Figure 3 As shown, the particles are approximately 4 micrometers in size and exhibit good crystallinity.

[0091] Example 6

[0092] This embodiment uses a high-temperature solid-state method to prepare fluorine-doped sodium-ion battery O3-type layered oxide cathode material Na. 0.9 Li 0.05 Cu 0.15 Ni 0.07 Fe 0.3 Mn 0.43 O 1.97 F 0.03 The specific steps include: weighing Na2CO3 (2% excess), NaF, LiOH, CuO, NiO, Fe2O3, and Mn2O3 into an agate mortar according to the stoichiometric ratio, adding an appropriate amount of anhydrous ethanol, mixing and grinding evenly to obtain a precursor, treating the precursor in a muffle furnace at 900°C in air atmosphere for 15 hours, and then cooling to room temperature to obtain the fluorine-doped sodium-ion battery O3-type layered oxide cathode material Na. 0.9 Li 0.05 Cu 0.15 Ni 0.07 Fe 0.3 Mn 0.43 O 1.97 F 0.03 .

[0093] The XRD pattern of the fluorine-doped sodium-ion battery O3-type layered oxide cathode material prepared in this embodiment is as follows: Figure 2As shown, comparison with the standard card reveals that its main phase is a pure O3 phase, space group R-3m, and it contains trace amounts of copper oxide impurities. SEM images are shown below. Figure 4 As shown, the particles are approximately 4 micrometers in size and exhibit good crystallinity. (Through...) Figure 5 The SEM-EDS images revealed copper enrichment sites on the material surface, indicating that it consists of copper oxide particles and thus has a copper oxide coating. The in-situ induced CuO coating effectively prevents corrosion of the electrode material by electrolyte decomposition byproducts. Therefore, an appropriate oxide coating will improve the electrochemical performance of the material.

[0094] Example 7

[0095] This embodiment uses a high-temperature solid-state method to prepare fluorine-doped sodium-ion battery O3-type layered oxide cathode material Na. 0.9 Li 0.05 Cu 0.15 Ni 0.07 Fe 0.3 Mn 0.43 O 1.97 F 0.03 The specific steps include: weighing Na2CO3 (2% excess), NH4F, LiOH, CuO, NiO, Fe2O3, and Mn2O3 into an agate mortar according to the stoichiometric ratio, adding an appropriate amount of anhydrous ethanol, mixing and grinding evenly to obtain a precursor, treating the precursor in a muffle furnace at 900°C in air atmosphere for 15 hours, and then cooling to room temperature to obtain the fluorine-doped sodium-ion battery O3-type layered oxide cathode material Na. 0.9 Li 0.05 Cu 0.15 Ni 0.07 Fe 0.3 Mn 0.43 O 1.97 F 0.03 .

[0096] The XRD pattern of the fluorine-doped sodium-ion battery O3-type layered oxide cathode material prepared in this embodiment is as follows: Figure 2 As shown, by comparing with the standard card, it can be seen that its main phase is a pure O3 phase substance with space group R-3m, and it contains trace amounts of copper oxide impurity phase.

[0097] Example 8

[0098] The examples demonstrate the preparation of fluorine-doped sodium-ion battery O3-type layered oxide cathode material NaCu using a high-temperature solid-state method. 0.11 Ni 0.22 Fe 0.33 Mn 0.33 O 1.97 F 0.03The specific steps include: weighing Na2CO3 (2% excess), NaF, CuO, NiO, Fe2O3, and Mn2O3 into an agate mortar according to the stoichiometric ratio, adding an appropriate amount of anhydrous ethanol, mixing and grinding evenly to obtain a precursor, treating the precursor in a muffle furnace at 900°C in air atmosphere for 15 hours, and then cooling to room temperature to obtain the fluorine-doped sodium-ion battery O3-type layered oxide cathode material NaCu. 0.11 Ni 0.22 Fe 0.33 Mn 0.33 O 1.97 F 0.03 .

[0099] The XRD pattern of the fluorine-doped sodium-ion battery O3-type layered oxide cathode material prepared in this embodiment is as follows: Figure 2 As shown, comparison with the standard card reveals that its main phase is a pure O3 phase, space group R-3m, and it contains trace amounts of nickel oxide impurities. SEM images are shown below. Figure 5 As shown, the particles are approximately 4 micrometers in size and exhibit good crystallinity.

[0100] Example 9

[0101] This embodiment uses the sol-gel method to prepare fluorine-doped sodium-ion battery O3-type layered oxide cathode material NaCu. 0.11 Ni 0.22 Fe 0.33 Mn 0.33 O 1.97 F 0.03 The specific steps include:

[0102] Sodium acetate, sodium fluoride, manganese acetate, nickel acetate, copper acetate, ferric nitrate, and an appropriate amount of citric acid were weighed according to the required stoichiometric ratio and dissolved in deionized water to form a mixed solution. The resulting slurry was heated to dryness in an oil bath to form a dry gel. The dry gel was collected and placed in a crucible, pretreated at 450℃ for 3-6 hours, then the pretreated powder was ground, pressed into tablets, placed in a crucible, and calcined at 850℃ for 20 hours in an air atmosphere. After cooling to room temperature, the fluoride-doped sodium-ion battery O3-type layered oxide cathode material Na was obtained. 0.9 Cu 0.11 Ni 0.11 Fe 0.30 Mn 0.48 O 1.97 F 0.03 .

[0103] Example 10

[0104] The example uses a high-temperature solid-state method to prepare fluorine-doped sodium-ion battery O3-type layered oxide cathode material Na. 0.83 Mg 0.05Cu 0.20 Fe 0.30 Mn 0.45 O 1.97 F 0.03 The specific steps include: weighing Na₂CO₃ (2% excess), NaF, MgO, CuO, Fe₂O₃, and Mn₂O₃ into an agate mortar according to the stoichiometric ratio, adding an appropriate amount of anhydrous ethanol, mixing and grinding evenly to obtain a precursor, treating the precursor in a muffle furnace at 900°C in air atmosphere for 15 hours, and then cooling to room temperature to obtain the fluorine-doped sodium-ion battery O₃-type layered oxide cathode material Na. 0.83 Mg 0.05 Cu 0.20 Fe 0.30 Mn 0.45 O 1.97 F 0.03 .

[0105] Example 11

[0106] This embodiment uses a high-temperature solid-state method to prepare vacancy-doped sodium-ion battery O3-type layered oxide cathode material Na. 0.9 Li 0.05 Cu 0.15 Ni 0.07 Fe 0.3 Mn 0.43 O 1.97 □ 0.03 The specific steps include: weighing Na₂CO₃ (2% excess), LiOH, CuO, NiO, Fe₂O₃, and Mn₂O₃ into an agate mortar according to the stoichiometric ratio, adding an appropriate amount of anhydrous ethanol, mixing and grinding evenly to obtain a precursor; treating the precursor in a muffle furnace at 900°C in air for 15 hours, cooling to room temperature, and then calcining at 800°C in argon atmosphere for 60 minutes to obtain the vacancy-doped sodium-ion battery O₃-type layered oxide cathode material Na. 0.9 Li 0.05 Cu 0.15 Ni 0.07 Fe 0.3 Mn 0.43 O 1.97 □ 0.03 .

[0107] The vacancy-doped sodium-ion battery O3-type layered oxide cathode material prepared in this embodiment has a pure O3 phase as its main phase, space group R-3m, and contains trace amounts of copper oxide impurities.

[0108] Example 12

[0109] This embodiment uses a high-temperature solid-state method to prepare vacancy and fluorine ion-doped sodium-ion battery O3-type layered oxide cathode material Na. 0.9 Li0.05 Cu 0.15 Ni 0.07 Fe 0.3 Mn 0.43 O 1.94 F 0.03 □ 0.03 The specific steps include: weighing Na₂CO₃ (2% excess), NH₄F, LiOH, CuO, NiO, Fe₂O₃, and Mn₂O₃ into an agate mortar according to the stoichiometric ratio, adding an appropriate amount of anhydrous ethanol, mixing and grinding evenly to obtain a precursor; treating the precursor in a muffle furnace at 900°C in air for 15 hours, cooling to room temperature, and then calcining at 800°C in nitrogen for 60 minutes to obtain the vacancy and fluorine ion doped sodium-ion battery O₃-type layered oxide cathode material Na. 0.9 Li 0.05 Cu 0.15 Ni 0.07 Fe 0.3 Mn 0.43 O 1.94 F 0.03 □ 0.03 .

[0110] Example 13

[0111] This embodiment uses the sol-gel method to prepare vacancy- and fluorine-doped sodium-ion battery O3-type layered oxide cathode material NaCu. 0.11 Ni 0.22 Fe 0.33 Mn 0.33 O 1.94 F 0.03 □ 0.03 The specific steps include:

[0112] Sodium acetate, sodium fluoride, manganese acetate, nickel acetate, copper acetate, ferric nitrate, and an appropriate amount of citric acid were weighed according to the required stoichiometric ratio and dissolved in deionized water to form a mixed solution. The resulting slurry was heated to dryness in an oil bath to form a dry gel. The dry gel was collected and placed in a crucible, pretreated at 450℃ for 3-6 hours, then the pretreated powder was ground, pressed into tablets, placed in a crucible, and calcined at 850℃ for 20 hours in an air atmosphere. After cooling to room temperature, it was calcined at 800℃ for 60 minutes in a nitrogen atmosphere to obtain the vacancy and fluorine ion doped sodium-ion battery O3 type layered oxide cathode material Na. 0.9 Cu 0.11 Ni 0.11 Fe 0.30 Mn 0.48 O 1.94 F 0.03 □ 0.03 .

[0113] Example 14

[0114] This embodiment uses spray drying to prepare fluorine-doped sodium-ion battery O3-type layered oxide cathode material Na. 0.83 Mg 0.05 Cu 0.20 Fe 0.30 Mn 0.45 O 1.97 F 0.03 The specific steps include: weighing Na2CO3 (2% excess), MgO, NaF, CuO, Fe2O3, Mn2O3, and an appropriate amount of citric acid according to the stoichiometric ratio and dissolving them in deionized water to form a slurry; injecting the obtained slurry into a spray dryer for spray drying to obtain a uniformly distributed precursor; placing the obtained precursor in a crucible, pretreating it at 450℃ for 5 hours, then grinding the pretreated powder evenly, and treating it in an air atmosphere in a muffle furnace at 900℃ for 15 hours; after cooling to room temperature, the fluorine-doped sodium-ion battery O3-type layered oxide cathode material Na is obtained. 0.83 Mg 0.05 Cu 0.20 Fe 0.30 Mn 0.4 5O 1.97 F 0.03 .

[0115] To make the technical effects of the invention clearer, we have also designed a comparative example for comparison with the above embodiments.

[0116] Comparative Example 1

[0117] This comparative example uses a high-temperature solid-state method to prepare Na3-type layered oxide cathode material for sodium-ion batteries. 0.9 Cu 0.17 Ni 0.05 Fe 0.3 Mn 0.48 The specific steps for obtaining O2 include: weighing Na2CO3 (2% excess), CuO, NiO, Fe2O3, and Mn2O3 into an agate mortar according to the stoichiometric ratio, adding an appropriate amount of anhydrous ethanol, mixing and grinding evenly to obtain a precursor; treating the precursor in a muffle furnace at 900°C in air atmosphere for 15 hours; and then cooling to room temperature to obtain the O3-type layered oxide cathode material for sodium-ion batteries. 0.9 Cu 0.17 Ni 0.05 Fe 0.3 Mn 0.48 O2.

[0118] The XRD pattern of the sodium-ion battery O3-type layered oxide cathode material prepared in this comparative example is shown below. Figure 1As shown, comparison with the standard card reveals that it is a pure O3 phase material with space group R-3m. The fact that this comparative example shows a pure O3 phase material without F / vacancy doping indicates that its surface lacks a metal oxide coating.

[0119] Comparative Example 2

[0120] This comparative example uses a high-temperature solid-state method to prepare Na3-type layered oxide cathode material for sodium-ion batteries. 0.9 Li 0.05 Cu 0.15 Ni 0.07 Fe 0.3 Mn 0.43 The specific steps for obtaining O2 include: weighing Na2CO3 (2% excess), LiOH, CuO, NiO, Fe2O3, and Mn2O3 into an agate mortar according to the stoichiometric ratio, adding an appropriate amount of anhydrous ethanol, mixing and grinding evenly to obtain a precursor; treating the precursor in a muffle furnace at 900°C in air atmosphere for 15 hours; and then cooling to room temperature to obtain the sodium-ion battery O3-type layered oxide cathode material Na. 0.9 Li 0.05 Cu 0.15 Ni 0.07 Fe 0.3 Mn 0.43 O2.

[0121] The XRD pattern of the sodium-ion battery O3-type layered oxide cathode material prepared in this comparative example is shown below. Figure 2 As shown, comparison with the standard card reveals that it is a pure O3 phase substance with space group R-3m. SEM images are shown below. Figure 5 As shown, the particles are approximately 4 micrometers in size and exhibit good crystallinity. The fact that this comparative example shows a pure O3 phase without F / vacancy doping indicates that its surface lacks a metal oxide coating.

[0122] Comparative Example 3

[0123] This comparative example uses a high-temperature solid-state method to prepare NaCu, an O3-type layered oxide cathode material for sodium-ion batteries. 0.11 Ni 0.22 Fe 0.33 Mn 0.33 The specific steps for obtaining O2 include: weighing Na2CO3 (2% excess), CuO, NiO, Fe2O3, and Mn2O3 into an agate mortar according to the stoichiometric ratio, adding an appropriate amount of anhydrous ethanol, mixing and grinding evenly to obtain a precursor; treating the precursor in a muffle furnace at 900°C in air atmosphere for 15 hours; and then cooling to room temperature to obtain the sodium-ion battery O3-type layered oxide cathode material NaCu. 0.11 Ni 0.22 Fe 0.33 Mn 0.33 O2.

[0124] The sodium-ion battery O3-type layered oxide cathode materials prepared in the above embodiments of the present invention and the materials in the comparative examples were tested and the results were compared.

[0125] Half-cell assembly: The fluorine-doped sodium-ion battery O3-type layered oxide cathode material from each embodiment was slurried with conductive carbon black (Super P) and vinylidene fluoride (PVDF) at a mass ratio of 75:15:10 in an N-methylpyrrolidone (NMP) solution, coated onto aluminum foil, vacuum dried, and then cut into 12 mm diameter electrode sheets (with a loading of 5-10 mg / cm²). 2 Using a sodium metal sheet as the negative electrode, a 1 mol / L NaClO4 / polycarbonate (PC): ethylene carbonate (EC): dimethyl carbonate (DMC) solution (volume ratio 1:1:1) was used as the electrolyte, and a glass fiber diaphragm was used to assemble a CR2032 coin cell half-cell in an argon glove box.

[0126] Charge and discharge test: The voltage range for charging and discharging the coin cell half-cell is 2.0 / 2.5-4.0V. Before the cycle test, it was activated twice with a low current density of 15mA / g (0.1C). Then it was cycled at 1C rate within the same voltage range. All electrochemical performance tests were performed at room temperature.

[0127] Figure 8 Na, the O3-type layered oxide cathode material for sodium-ion batteries prepared in Example 6 0.9 Li 0.05 Cu 0.15 Ni 0.07 Fe 0.3 Mn 0.43 O 1.97 F 0.03 Compared with the O3 layered oxide cathode material Na without fluorine ion doping in Comparative Example 2 0.9 Li 0.05 Cu 0.15 Ni 0.07 Fe 0.3 Mn 0.43 The cycling performance curves of O2 in half-cell tests were obtained by first activating both materials by cycling at 0.1C rate for two weeks at 2.5-4.0V, and then cycling at 1C rate for 300 cycles. At low rates, the undoped control sample showed a reversible specific capacity of 128 mAh·g. -1 The reversible specific capacity of the fluorine-doped sample is still 127 mAh·g. -1 This indicates that fluorine ion doping did not reduce the reversible specific capacity of the material. After 300 cycles, the reversible specific capacity of the undoped sample decreased from 116 mAh·g. -1 Reduced to 81.5 mAh·g -1The capacity retention rate was approximately 70%, while the reversible specific capacity of the fluorine-doped sample decreased from 117 mAh·g. -1 Reduced to 95.8 mAh·g -1 The capacity retention rate was 82%, which shows that fluorine ion doping can significantly improve the cycle performance of layered oxide sodium ion battery materials.

[0128] Figure 9 Na, the O3-type layered oxide cathode material for sodium-ion batteries prepared in Example 6 0.9 Li 0.05 Cu 0.15 Ni 0.07 Fe 0.3 Mn 0.43 O 1.97 F 0.03 Compared with the O3 layered oxide cathode material Na without fluorine ion doping in Comparative Example 2 0.9 Li 0.05 Cu 0.15 Ni 0.07 Fe 0.3 Mn 0.43 The rate performance curves of O2 in half-cell testing show that the specific capacities of the fluorine-doped samples at 0.1C, 0.2C, 0.5C, 1C, 2C, 5C, and 10C are 127, 124, 121, 119, 113, 102, and 83 mAh·g, respectively. -1 The values ​​for the undoped samples were 128, 124, 118, 112, 105, 92, and 71 mAh·g, respectively. -1 It can be seen that the fluorine-doped sample has superior rate performance, mainly due to the further improvement in ion transport and electronic conduction of the material.

[0129] Figure 10 NaCu, an O3-type layered oxide cathode material for sodium-ion batteries prepared in Example 8. 0.11 Ni 0.22 Fe 0.33 Mn 0.33 O 1.97 F 0.03 Compared with the O3 layered oxide cathode material NaCu without fluorine ion doping in Comparative Example 3 0.11 Ni 0.22 Fe 0.33 Mn 0.33 The cycling performance curves of O2 in half-cell tests were obtained. Both materials were first activated by cycling at 0.1C for two weeks at 2.0-4.0V, followed by 80 cycles at 1C. At low rates, the undoped control sample showed a reversible specific capacity of 127 mAh·g. -1 The fluorine-doped sample has a reversible specific capacity of 130 mAh·g.-1 This indicates that fluorine ion doping did not significantly affect the reversible specific capacity of the material. After 80 cycles, the reversible specific capacity of the undoped sample increased from 119 mAh·g⁻¹. -1 Reduced to 100mAh·g -1 The capacity retention rate was approximately 84%, while the reversible specific capacity of the fluorine-doped sample decreased from 120 mAh·g. -1 Reduced to 112mAh·g -1 The capacity retention rate is approximately 93.3%, demonstrating that fluorine ion doping can significantly improve the cycle performance of layered oxide sodium-ion battery materials.

[0130] Figure 11 Na, the O3-type layered oxide cathode material for sodium-ion batteries prepared in Example 11 0.9 Li 0.05 Cu 0.15 Ni 0.07 Fe 0.3 Mn 0.43 O 1.97 □ 0.03 Compared with the O3 layered oxide cathode material Na without doped vacancies in Comparative Example 2 0.9 Li 0.05 Cu 0.15 Ni 0.07 Fe 0.3 Mn 0.43 The cycling performance curves of O2 in half-cell tests were obtained. Both materials were first activated by cycling at 0.1C for two weeks at 2.5-4.0V, followed by 300 cycles at 1C. At low rates, the undoped control sample showed a reversible specific capacity of 127 mAh·g. -1 The vacancy-doped sample has a reversible specific capacity of 125 mAh·g. -1 This indicates that vacancy doping did not significantly affect the reversible specific capacity of the material. After 300 cycles, the reversible specific capacity of the undoped sample increased from 116 mAh·g⁻¹. -1 Reduced to 81.5 mAh·g -1 The capacity retention rate was approximately 70%, while the reversible specific capacity of the vacancy-doped sample was only 116 mAh·g. -1 Reduced to 94.2 mAh·g -1 The capacity retention rate was approximately 81.2%, demonstrating that vacancy doping can significantly improve the cycle performance of layered oxide sodium-ion battery materials.

[0131] This invention replaces oxygen ions with a small amount of fluoride ions and / or vacancies in a material to obtain a fluoride- and / or vacancy-doped sodium-ion battery O3-type layered oxide cathode material. The doping of oxygen sites with fluoride ions and / or vacancies improves the structural stability of the sodium-ion battery cathode material during charge and discharge, suppresses the dissolution of transition metal ions and the formation of stacking faults, enhances the ion and electronic conduction of the material, and can induce the in-situ formation of a transition metal oxide coating layer on the material surface, thereby improving the long-term cycle stability of the material. The sodium-ion secondary battery prepared by using the fluoride- and / or vacancy-doped layered oxide cathode material of this invention as the cathode can be used in large-scale energy storage devices for solar power generation, wind power generation, smart grid peak shaving, distributed power stations, backup power supplies, or communication base stations.

[0132] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A sodium-ion battery cathode material doped with fluorine ions or doped with both fluorine ions and vacancies, characterized in that, The sodium-ion battery cathode material doped with fluorine ions or doped with fluorine ions and vacancies contains some fluorine ions or fluorine ions and vacancies occupying oxygen sites to replace oxygen ions. The ions at the transition metal sites form an octahedral structure with the six adjacent oxygen and / or fluorine and / or vacancies, and are alternately arranged with the sodium ion layer coordinated to the octahedral, forming an O3-type layered oxide material with space group R-3m. The general chemical formula of the sodium-ion battery cathode material is: Na x M a Cu b Fe c Mn d 0 2-e F e1 □ e2 Wherein, Cu, Fe, and Mn are transition metal elements, M is an ion that substitutes for the transition metal site, F is a negative monovalent fluoride ion, and □ is a vacancy occupying an oxygen site; 0.76≤x≤1, 0<a≤0.5, 0<b≤0.4, 0<c≤0.4, 0.1≤d≤0.6, 0<e≤0.1, e=e1+e2; The doping of fluoride ions or fluoride ions and vacancies to oxygen sites is used to improve the structural stability and intrinsic ion and electronic conduction of the sodium-ion battery cathode material during charge and discharge, and to induce the formation of a transition metal oxide coating layer in situ on the surface of the material particles; the transition metal oxide includes copper oxide or nickel oxide. The ions that substitute for the transition metal sites specifically include: Li + Mg 2+ Ca 2+ Ni 2+ Zn 2+ Ba 2+ Ni 3+ Al 3+ B 3+ Cr 3+ Co 3+ V 3+ Y 3+ Ti 4+ Zr 4+ Sn 4+ Si 4+ Mo 4+ 、Nb 5+ Sb 5+ Mo 5+ Te 6+ One or more of them.

2. A method for preparing the sodium-ion battery cathode material according to claim 1, characterized in that, The preparation method is a solid-state method, including: Step 1: Mix sodium source (100wt%-105wt% of the required sodium stoichiometry), fluorine source (the required stoichiometry), transition metal (the required stoichiometry), and oxides, hydroxides, or nitrates of ions that dopant or substitute for the transition metal sites in proportion, and grind, ball mill, or sand mill evenly to obtain precursor powder. Step 2: Place the obtained precursor powder in a crucible and calcine it at 700℃-950℃ for 10-24 hours in an air or oxygen sintering atmosphere. Then grind the heat-treated material. The preparation method of the sodium-ion battery cathode material doped with fluorine ions and vacancy further includes step 3, which involves calcining the sample after step 2 in an inert atmosphere at 200℃-900℃ for 10-120 minutes to form vacancy doping of oxygen sites.

3. The preparation method according to claim 2, characterized in that, The sodium source includes one or more of sodium carbonate, sodium nitrate, sodium peroxide, sodium superoxide, sodium hydroxide, or sodium oxalate. The fluorine source includes sodium fluoride and / or ammonium fluoride; The transition metals include at least Cu, Fe, and Mn; the ions that dope and substitute the transition metal sites specifically include: Li + Mg 2+ Ca 2+ Ni 2+ Zn 2+ Ba 2+ Ni 3+ Al 3+ B 3+ Cr 3+ Co 3+ V 3+ Y 3+ Ti 4+ Zr 4+ Sn 4+ Si 4+ Mo 4+ 、Nb 5+ Sb 5+ Mo 5+ Te 6+ One or more of them.

4. A method for preparing the sodium-ion battery cathode material according to claim 1, characterized in that, The preparation method is spray drying, including: Step 1: Mix the required sodium source (100wt%-105wt%), the required fluorine source, the required transition metal, and the oxides, hydroxides, or nitrates of ions that dope or substitute for the transition metal sites in a certain proportion to form a precursor. Step 2: Add ethanol or water to the precursor and stir until homogeneous to form a slurry. Inject the resulting slurry into a spray dryer for spray drying to obtain the precursor. Step 3: Place the obtained precursor in a crucible and pretreat it at 250-500℃ for 1-5 hours. Then grind the pretreated powder and place it in a crucible to treat it at 700-950℃ for 10-24 hours. The preparation method of the sodium-ion battery cathode material doped with fluorine ions and vacancy further includes step 4, which involves calcining the sample after step 3 in an inert atmosphere at 200℃-900℃ for 10-120 minutes to form vacancy doping of oxygen sites.

5. The preparation method according to claim 4, characterized in that, The sodium source includes one or more of sodium carbonate, sodium nitrate, sodium peroxide, sodium superoxide, sodium hydroxide, or sodium oxalate. The fluorine source includes sodium fluoride and / or ammonium fluoride; The transition metals include at least Cu, Fe, and Mn; the ions that dope and substitute the transition metal sites specifically include: Li + Mg 2+ Ca 2+ Ni 2+ Zn 2+ Ba 2+ Ni 3+ Al 3+ B 3+ Cr 3+ Co 3+ V 3+ Y 3+ Ti 4+ Zr 4+ Sn 4+ Si 4+ Mo 4+ 、Nb 5+ Sb 5+ Mo 5+ Te 6+ One or more of them.

6. A method for preparing the sodium-ion battery cathode material according to claim 1, characterized in that, The preparation method is a sol-gel method, including: Step 1: Weigh out 100 wt%-105 wt% of sodium salt, 100 wt% of fluoride salt, 100 wt% of transition metal and soluble salt of ion doped and substituted for transition metal sites, and an appropriate amount of citric acid according to the required stoichiometric ratio, and dissolve them in deionized water to form a slurry. Step 2: Heat the obtained slurry in an oil bath to evaporate it and form a dry gel; Step 3: Place the obtained dry gel in a crucible and pre-treat it at 400℃-500℃ for 3-6 hours. Then grind the powder obtained from the pre-treatment, compress it into tablets, place them in a crucible, and calcine them at 700℃-900℃ in an air or oxygen atmosphere for 10-24 hours. The preparation method of the sodium-ion battery cathode material doped with fluorine ions and vacancy further includes step 4, which involves calcining the sample after step 3 in an inert atmosphere at 200℃-900℃ for 10-120 minutes to form vacancy doping of oxygen sites.

7. The preparation method according to claim 6, characterized in that, The sodium salt includes one or more of sodium carbonate, sodium nitrate, or sodium oxalate; The fluoride salt includes sodium fluoride and / or ammonium fluoride; The transition metals include at least Cu, Fe, and Mn; the ions that dope and substitute the transition metal sites specifically include: Li + Mg 2+ Ca 2+ Ni 2+ Zn 2+ Ba 2+ Ni 3+ Al 3+ B 3+ Cr 3+ Co 3+ V 3+ Y 3+ Ti 4+ Zr 4+ Sn 4+ Si 4+ Mo 4+ 、Nb 5+ Sb 5+ Mo 5+ Te 6+ One or more of them.

8. A vacancy-doped sodium-ion battery cathode material, characterized in that, In the vacancy-doped sodium-ion battery cathode material, some vacancies occupy oxygen sites to replace oxygen ions. The ions at the transition metal sites form an octahedral structure with the six adjacent oxygen and / or vacancies, and are alternately arranged with the sodium ion layer coordinated to the octahedral, forming an O3-type layered oxide material with space group R-3m. The general chemical formula of the sodium-ion battery cathode material is: Na x M a Cu b Fe c Mn d 0 2-e2 □ e2 ; where Cu, Fe, and Mn are transition metal elements, M is an ion that substitutes for the transition metal site, and □ is a vacancy occupying the oxygen site; 0.76≤x≤1, 0<a≤0.5, 0<b≤0.4, 0<c≤0.4, 0.1≤d≤0.6, 0<e2≤0.1; The doping of oxygen sites by vacancy occupancy to replace oxygen ions is used to improve the structural stability and intrinsic ion and electronic conduction of sodium-ion battery cathode materials during charge and discharge processes, and to induce the formation of a transition metal oxide coating layer in situ on the surface of material particles; the transition metal oxide includes copper oxide or nickel oxide. The ions that substitute for the transition metal sites specifically include: Li + Mg 2+ Ca 2+ Ni 2+ Zn 2+ Ba 2+ Ni 3+ Al 3+ B 3+ Cr 3+ Co 3+ V 3+ Y 3+ Ti 4+ Zr 4+ Sn 4+ Si 4+ Mo 4+ 、Nb 5+ Sb 5+ Mo 5+ Te 6+ One or more of the following; The vacancy-doped sodium-ion battery cathode material is obtained by any one of the following preparation methods: solid-state method, spray drying method, or sol-gel method. The solid-state method includes: mixing a sodium source (100wt%-105wt% of the required sodium stoichiometry), a transition metal (the required stoichiometry), and oxides, hydroxides, or nitrates of ions that dope and substitute for the transition metal sites in a certain proportion; grinding, ball milling, or sand milling to obtain a precursor powder; placing the obtained precursor powder in a crucible and calcining it at 700℃-950℃ for 10-24 hours in an air or oxygen sintering atmosphere; grinding the heat-treated material; and calcining the ground sample a second time at 200℃-900℃ in an inert atmosphere for 10-120 minutes to form vacancy doping at oxygen sites. The spray drying method includes: mixing a sodium source (100wt%-105wt% of the required sodium stoichiometry), a transition metal (the required stoichiometry), and oxides, hydroxides, or nitrates of ions that dope and substitute for the transition metal sites in a certain proportion to form a precursor; adding ethanol or water to the precursor and stirring evenly to form a slurry; injecting the obtained slurry into a spray dryer for spray drying to obtain the precursor; placing the obtained precursor in a crucible and pretreating it at 250-500℃ for 1-5 hours; then grinding the pretreated powder and placing it in a crucible for high-temperature treatment at 700-950℃ for 10-24 hours; and calcining the sample after high-temperature treatment again at 200℃-900℃ in an inert atmosphere for 10-120 minutes to form vacancy doping at oxygen sites. The sol-gel method includes: weighing 100 wt%-105 wt% of sodium salt, the required stoichiometric amount of transition metal, and soluble salts of ions that dopant and substituted for the transition metal sites, and an appropriate amount of citric acid in deionized water to form a slurry; heating the obtained slurry in an oil bath to evaporate it to dryness to form a dry gel; placing the obtained dry gel in a crucible and pretreating it at 400℃-500℃ for 3-6 hours; then grinding the pretreated powder, pressing it into tablets, and calcining it in a crucible at 700℃-900℃ in an air or oxygen atmosphere for 10-24 hours; and then calcining the calcined sample a second time at 200℃-900℃ in an inert atmosphere for 10-120 minutes to form vacancy doping at oxygen sites.

9. A method for preparing the sodium-ion battery cathode material according to claim 8, characterized in that, The preparation method is a solid-state method, including: Step 1: Mix the required sodium source (100wt%-105wt% stoichiometry), the required transition metal, and the oxides, hydroxides, or nitrates of ions that dopant or substitute for the transition metal sites in a certain proportion, and grind, ball mill, or sand mill until uniform to obtain the precursor powder. Step 2: Place the obtained precursor powder in a crucible and calcine it at 700℃-950℃ for 10-24 hours in an air or oxygen sintering atmosphere. Then grind the heat-treated material. Step 3: The sample after step 2 is calcined again at 200℃-900℃ in an inert atmosphere for 10-120 minutes to form vacancy doping of oxygen sites.

10. The preparation method according to claim 9, characterized in that, The sodium source includes one or more of sodium carbonate, sodium nitrate, sodium peroxide, sodium superoxide, sodium hydroxide, or sodium oxalate. The transition metals include at least Cu, Fe, and Mn; the ions that dope and substitute the transition metal sites specifically include: Li + Mg 2+ Ca 2+ Ni 2+ Zn 2+ Ba 2+ Ni 3+ Al 3+ B 3+ Cr 3+ Co 3+ V 3+ Y 3+ Ti 4+ Zr 4+ Sn 4+ Si 4+ Mo 4+ 、Nb 5+ Sb 5+ Mo 5+ Te 6+ One or more of them.

11. A method for preparing the sodium-ion battery cathode material according to claim 8, characterized in that, The preparation method is spray drying, including: Step 1: Mix the required sodium source (100wt%-105wt% stoichiometry), the required transition metal, and the oxides, hydroxides, or nitrates of ions that dope or substitute the transition metal sites in a certain proportion to form a precursor. Step 2: Add ethanol or water to the precursor and stir until homogeneous to form a slurry. Inject the resulting slurry into a spray dryer for spray drying to obtain the precursor. Step 3: Place the obtained precursor in a crucible and pretreat it at 250-500℃ for 1-5 hours. Then grind the pretreated powder and place it in a crucible to treat it at 700-950℃ for 10-24 hours. Step 4: The sample after step 3 is calcined again at 200℃-900℃ in an inert atmosphere for 10-120 minutes to form vacancy doping of oxygen sites.

12. The preparation method according to claim 11, characterized in that, The sodium source includes one or more of sodium carbonate, sodium nitrate, sodium peroxide, sodium superoxide, sodium hydroxide, or sodium oxalate. The transition metals include at least Cu, Fe, and Mn; the ions that dope and substitute the transition metal sites specifically include: Li + Mg 2+ Ca 2+ Ni 2+ Zn 2+ Ba 2+ Ni 3+ Al 3+ B 3+ Cr 3+ Co 3+ V 3+ Y 3+ Ti 4+ Zr 4+ Sn 4+ Si 4+ Mo 4+ 、Nb 5+ Sb 5+ Mo 5+ Te 6+ One or more of them.

13. A method for preparing the sodium-ion battery cathode material according to claim 8, characterized in that, The preparation method is a sol-gel method, including: Step 1: Weigh out 100 wt%-105 wt% of sodium salt, the required stoichiometric amount of transition metal, and soluble salts of ions that dopant and substituted for the transition metal sites, and an appropriate amount of citric acid according to the required stoichiometric ratio, and dissolve them in deionized water to form a slurry of mixed solution. Step 2: Heat the obtained slurry in an oil bath to evaporate it and form a dry gel; Step 3: Place the obtained dry gel in a crucible and pre-treat it at 400℃-500℃ for 3-6 hours. Then grind the powder obtained from the pre-treatment, compress it into tablets, place them in a crucible, and calcine them at 700℃-900℃ in an air or oxygen atmosphere for 10-24 hours. Step 4: The sample after step 3 is calcined again at 200℃-900℃ in an inert atmosphere for 10-120 minutes to form vacancy doping of oxygen sites.

14. The preparation method according to claim 13, characterized in that, The sodium salt includes one or more of sodium carbonate, sodium nitrate, or sodium oxalate; The transition metals include at least Cu, Fe, and Mn; the ions that dope and substitute the transition metal sites specifically include: Li + Mg 2+ Ca 2+ Ni 2+ Zn 2+ Ba 2+ Ni 3+ Al 3+ B 3+ Cr 3+ Co 3+ V 3+ Y 3+ Ti 4+ Zr 4+ Sn 4+ Si 4+ Mo 4+ 、Nb 5+ Sb 5+ Mo 5+ Te 6+ One or more of them.

15. A positive electrode, characterized in that, The positive electrode includes the fluoride ion or fluoride ion and vacancy-doped sodium ion battery positive electrode material as described in claim 1, or the vacancy-doped sodium ion battery positive electrode material as described in claim 8.

16. A sodium-ion secondary battery comprising the positive electrode as described in claim 15.

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