O3 type layered oxide positive electrode material and preparation method and application thereof

Abstract

The invention provides an O3 type layered oxide positive electrode material as well as a preparation method and application thereof, and belongs to the technical field of O3 type sodium ion battery positive electrode materials. The O3 type layered oxide positive electrode material is characterized in that the chemical formula is NaxNiaFebMncLidMeO2, x is larger than or equal to 0.83 and smaller than or equal to 0.95, a + b + c + d + e = 1, a, b and c are larger than or equal to 0.10 and smaller than or equal to 0.50, d is larger than or equal to 0.02 and smaller than or equal to 0.06, M is larger than or equal to 0.05 and smaller than or equal to 0.20, and M is at least one of transition metal Ti, Cr, Co, Cu and Zn. According to the invention, the (003) crystal face strength of the material is improved, the particle size of the material is increased, and residual alkali substances on the surfaces of crystal grains are reduced, so that not only is the air stability of the material improved, but also the cycle stability and the rate capability of the material are improved.

Description

Technical Field

[0001] This invention relates to the field of O3-type sodium-ion battery cathode material technology, specifically to an O3-type layered oxide cathode material, its preparation method, and its application. Background Technology

[0002] With the widespread application of lithium-ion batteries in energy storage, the demand for lithium resources has increased dramatically. However, lithium resources are scarce and unevenly distributed in the Earth's crust, leading to a year-on-year increase in the cost of lithium-ion batteries and limiting their application in large-scale energy storage. Sodium metal resources are abundant, with an abundance of 2.75% in the Earth's crust, far exceeding that of lithium metal (0.0017%). Furthermore, sodium-ion batteries have similar charge-discharge mechanisms to lithium-ion batteries. Therefore, developing sodium-ion battery technology is conducive to achieving the sustainable development of large-scale energy storage.

[0003] Common sodium-ion cathode materials mainly include layered transition metal oxides, polyanionic compounds, Prussian blue compounds, tunnel-type transition metal oxides, and organic compounds. Among them, sodium-ion layered transition metal oxides have become very promising cathode materials for sodium-ion batteries due to their advantages such as high theoretical specific capacity, simple preparation, and diverse structural compositions. Currently, the two most reported types of sodium-ion layered cathode materials are O3-phase and P2-phase materials. Compared to P2-phase materials, O3-type layered cathode materials have advantages such as high energy density, good compatibility with hard carbon anodes, and compatibility with layered lithium-ion battery production lines, thus attracting significant attention from the research and industrial communities.

[0004] However, most O3-type sodium ion layered cathodes have extremely poor air stability, as exemplified by the typical O3-type sodium cathode NaNi. 1 / 3 Fe 1 / 3 Mn 1 / 3 Taking O2 as an example, when placed in the air, NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 will inevitably cause surface degradation, producing surface residual alkali and a surface reconstruction layer, as shown in the following equation:

[0005]

[0006] Zheng Jiaxin's team at Peking University (Journal of the American Chemical Society 146, 22374-22386 (2024)) used density functional theory calculations and molecular dynamics simulations to study the interaction between air molecules and NaNi. 1 / 3 Fe 1 / 3Mn 1 / 3The chemical reaction process on the surface of O2(NFM) layered cathode material reveals that the poor air stability of NFM is due to the following three aspects: 1. Low proportion of non-active (003) surface, 2. Strong surface adsorption and high surface reactivity, 3. Poor stability of sodium ions on the surface.

[0007] The poor surface stability of these materials leads to increased costs during storage, transportation, and subsequent battery assembly. Currently, research on improving the air stability of O3-type sodium-ion layered cathode materials focuses on methods such as coating and doping. For example, in NaNi... 1 / 3 Fe 1 / 3 Mn 1 / 3 Coating O2 with a hydrophobic perfluorodecyltrimethoxysilane molecule (ACS Nano 18, 13106-13116 (2024)) can effectively improve its air stability, but this introduces a more complex process, making it far from practical application, and the non-electrochemically inactive coating layer can hinder sodium ion transport. Introducing low-valence metal elements or metals with large redox potential differences is also a common method to improve the air stability of O3-type materials (CN106328928A), but large doping amounts of non-electrochemically inactive elements can severely limit the specific capacity of such materials. Therefore, a more suitable method is still needed to improve the electrochemical performance of the material while simultaneously enhancing its air stability. Summary of the Invention

[0008] This invention is made to solve the above-mentioned problems, and aims to provide an O3-type layered oxide cathode material, its preparation method and application.

[0009] This invention provides an O3-type layered oxide cathode material with the following characteristics: Na x Ni a Fe b Mn c Li d M e O2, where 0.83≤x≤0.95, a+b+c+d+e=1, 0.10≤a,b,c≤0.50, 0.02≤d≤0.06, 0.05≤M≤0.20, and M is at least one of the transition metals Ti, Cr, Co, Cu, and Zn.

[0010] This invention also provides a method for preparing the above-mentioned O3-type layered oxide cathode material, characterized by the following steps: Step 1, according to the chemical formula Na... x Ni a Fe b Mn c Li d M eThe molar ratio of each element in O2 is determined by weighing the precursors of Na, Ni, Fe, Mn, Li, and M; Step 2: the precursors corresponding to each element are placed in a ball mill and ball-milled to obtain precursor powder; Step 3: the precursor powder is pressed into tablets to obtain powder tablets; Step 4: the powder tablets are calcined in an oxygen atmosphere to obtain O3-type layered oxide cathode material.

[0011] The preparation method of O3-type layered oxide cathode material provided by the present invention may also have the following characteristics: in step 1, the precursors of Na and Li are selected from their carbonates, nitrates and oxides, and the precursors of other elements are selected from their oxides.

[0012] The method for preparing O3-type layered oxide cathode material provided by the present invention may also have the following characteristics: in step 2, the rotation speed of the ball mill is not less than 400 rpm and the ball milling time is not less than 6 hours.

[0013] The preparation method of O3-type layered oxide cathode material provided by the present invention may also have the following characteristics: in step 3, the pressure for pressing the sheet is not less than 10 MPa and the holding time is not less than 1 min.

[0014] The preparation method of O3-type layered oxide cathode material provided by the present invention may also have the following characteristics: in step 4, the heating rate of calcination does not exceed 5℃ / min, the sintering temperature is not lower than 850℃, the holding time is not lower than 12h, and the cooling rate is 1-3℃ / min.

[0015] The method for preparing O3-type layered oxide cathode material provided by the present invention may also have the following characteristics: the O3-type layered oxide cathode material has a large grain size, high (003) crystal plane strength and a small amount of surface residual alkali.

[0016] This invention also provides the application of the above-mentioned O3-type layered oxide cathode material as a cathode material for sodium-ion batteries.

[0017] In the above-described applications provided by the present invention, the following feature may also be included: wherein the application is as follows: O3-type layered oxide cathode material is mixed with conductive additives, binders and solvents in a predetermined ratio, and then subjected to slurry preparation, coating and drying to obtain a composite cathode.

[0018] The present invention also provides a sodium-ion battery, characterized by comprising: a composite positive electrode, a separator, an organic electrolyte, and a negative electrode, wherein the composite positive electrode comprises an O3-type layered oxide positive electrode material, the separator is any one of a glass fiber separator, a ceramic separator, and a polymer separator, the organic electrolyte is a carbonate electrolyte, the solvent is selected from at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC), the solute is selected from at least one of sodium hexafluorophosphate (NaPF6), sodium perchlorate (NaClO4), and sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), and the negative electrode is any one of metallic sodium, metal oxide, and hard carbon.

[0019] The role and effect of invention

[0020] This invention relates to an O3-type layered oxide cathode material, its preparation method, and its application. The chemical formula of the O3-type layered oxide cathode material is: Na. x Ni a Fe b Mn c Li d M e O2, where 0.83≤x≤0.95, a+b+c+d+e=1, 0.10≤a,b,c≤0.50, 0.02≤d≤0.06, 0.05≤M≤0.20, and M is at least one of the transition metals Ti, Cr, Co, Cu, and Zn. This invention relates to a typical O3-type sodium electrode NaNi. 1 / 3 Fe 1 / 3 Mn 1 / 3 The introduction of Li doping, transition metal doping, and Na content design in O2 improves the strength of the (003) crystal facet, increases the particle size, and reduces residual alkali on the grain surface. This not only improves the material's air stability but also enhances its cycle stability and rate performance. Specifically, the larger particle size reduces the contact area between the material and air, and the (003) crystal facet has lower reactivity compared to other crystal faces, thus reducing surface reactivity. In addition to improved air stability, multi-element doping stabilizes the material's structure, improves its electrochemical stability, and reducing Na content lowers residual alkali on the surface, thereby enhancing the material's rate performance.

[0021] Furthermore, the preparation method of the O3-type layered oxide cathode material of this invention employs a single-step solid-state sintering method. By optimizing the calcination temperature and elemental ratio, the production process is simplified while achieving a synergistic improvement in material structural stability and electrochemical performance. Compared to traditional coating or single-element doping strategies, this method eliminates the need for complex post-processing, preserving the material's high specific capacity while significantly enhancing cycle life and rate performance through lattice stabilization and broadening of sodium ion insertion / extraction channels. Moreover, this method improves the cathode's stability at high voltages by suppressing transition metal dissolution and surface phase transitions, addressing the pain points of traditional modification processes that sacrifice capacity or increase process complexity. This provides a comprehensive solution combining material design and process optimization for the large-scale application of low-cost, high-performance sodium-ion batteries. Attached Figure Description

[0022] Figure 1 Na in Embodiment 1 of the present invention 8 / 9 Ni 5 / 18 Fe 5 / 18 Mn 1 / 3 Li 1 / 18 Ti 1 / 18 SEM image of O2 material.

[0023] Figure 2 Na in Embodiment 1 of the present invention 8 / 9 Ni 5 / 18 Fe 5 / 18 Mn 1 / 3 Li 1 / 18 Ti 1 / 18 XRD pattern of O2 material.

[0024] Figure 3 Na in Embodiment 1 of the present invention 8 / 9 Ni 5 / 18 Fe 5 / 18 Mn 1 / 3 Li 1 / 18 Ti 1 / 18 A comparison of the first charge-discharge curves of O2 material before and after it was placed in air.

[0025] Figure 4 NaNi in Comparative Example 1 of this invention 1 / 3 Fe 1 / 3 Mn 1 / 3 SEM image of O2 material.

[0026] Figure 5 NaNi in Comparative Example 1 of this invention 1 / 3 Fe 1 / 3 Mn 1 / 3 XRD pattern of O2 material. Figure 6 NaNi in Comparative Example 1 of this invention 1 / 3 Fe 1 / 3 Mn1 / 3 A comparison of the first charge-discharge curves of O2 material before and after it was placed in air. Detailed Implementation

[0027] This invention provides an O3-type layered oxide cathode material and its preparation method.

[0028] The chemical formula of O3-type layered oxide cathode material is: Na x Ni a Fe b Mn c Li d M e O2, where 0.83≤x≤0.95, a+b+c+d+e=1, 0.10≤a,b,c≤0.50, 0.02≤d≤0.06, 0.05≤M≤0.20, and M is at least one of the transition metals Ti, Cr, Co, Cu, and Zn.

[0029] The preparation method of O3-type layered oxide cathode material includes the following steps:

[0030] Step 1, according to the chemical formula Na x Ni a Fe b Mn c Li d M e The molar ratios of each element in O2 were determined by weighing the precursors of Na, Ni, Fe, Mn, Li, and M. The precursors of Na and Li were selected from their carbonates, nitrates, and oxides, while the precursors of the other elements were selected from their oxides.

[0031] Step 2: Place the precursors corresponding to each element in a ball mill and ball mill them to obtain precursor powder. The ball mill speed shall be no less than 400 rpm and the ball milling time shall be no less than 6 hours.

[0032] Step 3: Compress the precursor powder into tablets to obtain powder tablets. The compression pressure shall be no less than 10 MPa, and the holding time shall be no less than 1 min.

[0033] Step 4: Calcine the powder sheet in an oxygen atmosphere to obtain O3-type layered oxide cathode material. The heating rate during calcination shall not exceed 5℃ / min, the sintering temperature shall not be lower than 850℃, the holding time shall not be lower than 12h, and the cooling rate shall be 1-3℃ / min.

[0034] This O3-type layered oxide cathode material exhibits a large grain size, high (003) crystal plane strength, and a small amount of surface residual alkali. This is because at higher heat treatment temperatures, the presence of sodium vacancies and Li elements can further promote grain growth. At the same time, the doped elements reduce the surface energy of the (003) plane, allowing more 003 planes to be exposed. Furthermore, reducing the sodium content can reduce surface residual alkali in the O3 cathode material during the synthesis process.

[0035] The present invention also provides a sodium-ion battery, which includes a composite positive electrode, a separator, an organic electrolyte, and a negative electrode.

[0036] The preparation process of the composite cathode is as follows: the above-mentioned O3-type layered oxide cathode material is mixed with conductive additives, binders and solvents in a predetermined ratio, and then subjected to slurry preparation, coating and drying to obtain the composite cathode. The conductive additive is preferably Super P, the binder is preferably PVDF, and the solvent is preferably N-methylpyrrolidone (NMP).

[0037] The diaphragm can be any one of glass fiber diaphragm, ceramic diaphragm and polymer diaphragm, preferably GF / D type glass fiber diaphragm.

[0038] The organic electrolyte is a carbonate electrolyte. The solvent is selected from at least one of DMC, DEC, EMC, EC, and PC, preferably EC:PC = 1:1; the solute is selected from at least one of NaPF6, NaClO4, and NaTFSI, preferably NaClO4.

[0039] The negative electrode is any one of metallic sodium, metal oxide, and hard carbon, preferably metallic sodium.

[0040] To make the technical means, creative features, objectives and effects of this invention easy to understand, the following embodiments, in conjunction with the accompanying drawings, specifically illustrate the O3-type layered oxide cathode material, its preparation method and application.

[0041] Example 1

[0042] This embodiment provides an O3-type layered oxide cathode material with the chemical formula Na. 8 / 9 Ni 5 / 18 Fe 1 / 6 Mn 1 / 3Li 1 / 18 Ti 1 / 6 O2. This embodiment also provides a method for preparing and applying the O3-type layered oxide cathode material.

[0043] (I) Preparation of Na 8 / 9 Ni 5 / 18 Fe 1 / 6 Mn 1 / 3 Li1 / 18 Ti 1 / 6 O2 materials

[0044] O3-type layered oxide cathode material (Na) 8 / 9 Ni 5 / 18 Fe 1 / 6 Mn 1 / 3 Li 1 / 18 Ti 1 / 6 The preparation method of O2 includes the following steps:

[0045] Step 1, according to Na 8 / 9 Ni 5 / 18 Fe 1 / 6 Mn 1 / 3 Li 1 / 18 Ti 1 / 6 The stoichiometric ratios of each element in O2 are determined by accurately weighing Na2CO3, NiO, Fe2O3, MnO2, Li2CO3, and TiO2. 2。

[0046] Step 2: Place the Na2CO3, NiO, Fe2O3, MnO2, Li2CO3, and TiO2 weighed in Step 1 into a ball mill and ball mill for 10 hours at a speed of 500 rpm to obtain precursor powder.

[0047] Step 3: Press the precursor powder under a pressure of 20 MPa for 1 minute to form a disc with a diameter of 14 mm, thus obtaining a powder disc.

[0048] Step 4: Calcine the powder flakes at 950℃ for 14 hours, with a heating rate of 4℃ / min and a cooling rate of 3℃ / min, to obtain the target product. In this embodiment, the target product is Na. 8 / 9 Ni 5 / 18 Fe 1 / 6 Mn 1 / 3 Li 1 / 18 Ti 1 / 6 O2 materials.

[0049] Figure 1 Na in Embodiment 1 of the present invention 8 / 9 Ni 5 / 18 Fe 5 / 18 Mn 1 / 3 Li 1 / 18 Ti 1 / 18 SEM image of O2 material.

[0050] like Figure 1 As shown, Na 8 / 9 Ni 5 / 18 Fe 5 / 18 Mn 1 / 3 Li 1 / 18 Ti 1 / 18The O2 material consists of sheet-like particles of approximately 8 × 3 μm, and its smooth surface indicates a reduction in residual alkali substances on the surface.

[0051] Figure 2 Na in Embodiment 1 of the present invention 8 / 9 Ni 5 / 18 Fe 5 / 18 Mn 1 / 3 Li 1 / 18 Ti 1 / 18 XRD pattern of O2 material.

[0052] like Figure 2 As shown, the XRD pattern reveals that this Na 8 / 9 Ni 5 / 18 Fe 5 / 18 Mn 1 / 3 Li 1 / 18 Ti 1 / 18 The O2 material is an O3 phase with a good layered structure. The (003) peak intensity is the highest in this material, and the ratio of the (003) to (104) peak intensities is I. (003) / I (004) It reached 1.46.

[0053] (II) Preparation of Na 8 / 9 Ni 5 / 18 Fe 1 / 6 Mn 1 / 3 Li 1 / 18 Ti 1 / 6 O2 complex positive electrode

[0054] The target product prepared above was mixed with Super P and binder PVDF at a mass ratio of 8:1:1, and solvent NMP was added. The solid content was 30%. The composite cathode was obtained by going through processes such as pulping, coating and drying.

[0055] (III) Assembling Sodium-ion Batteries

[0056] The composite positive electrode and the sodium negative electrode prepared above were assembled into a CR2025 coin cell. The electrolyte was selected as a carbonate electrolyte (a solution of EC / PC with 1M NaClO4 in a volume ratio of 1:1 and 5% fluoroethylene carbonate (FEC) as an electrolyte additive).

[0057] (iv) Sodium-ion battery charge and discharge test

[0058] The assembled sodium-ion battery was tested using a Xinwei constant temperature charge-discharge tester, and constant current charge-discharge tests were performed at a rate of 0.1C.

[0059] Figure 3 Na in Embodiment 1 of the present invention 8 / 9 Ni 5 / 18 Fe5 / 18 Mn 1 / 3 Li 1 / 18 Ti 1 / 18 A comparison of the first charge-discharge curves of O2 material before and after it was placed in air.

[0060] from Figure 3 As can be seen from this, Na, which was not placed in the air 8 / 9 Ni 5 / 18 Fe 5 / 18 Mn 1 / 3 Li 1 / 18 Ti 1 / 18 The O2 material exhibits a high discharge specific capacity of 127.4 mA h / g. After being placed in air for 7 days, the discharge capacity of the material is 119.2 mAh / g, with a decay of only 6.4%, demonstrating excellent air stability.

[0061] Example 2

[0062] This embodiment provides an O3-type layered oxide cathode material with the chemical formula Na. 17 / 18 Ni 5 / 18 Fe 2 / 9 Mn 1 / 3Li 1 / 18 Ti 1 / 9 O2. This embodiment also provides a method for preparing and applying the O3-type layered oxide cathode material.

[0063] (I) Preparation of Na 17 / 18 Ni 5 / 18 Fe 2 / 9 Mn 1 / 3 Li 1 / 18 Ti 1 / 9 O2 cathode material (Step 1, according to Na) 17 / 18 Ni 5 / 18 Fe 2 / 9Mn 1 / 3 Li 1 / 18 Ti 1 / 9 The stoichiometric ratio of each element in O2 is determined by accurately weighing Na2CO3, NiO, Fe2O3, MnO2, Li2CO3, and TiO2. The remaining steps are the same as in Example 1. (II) Preparation of Na 17 / 18 Ni 5 / 18 Fe 2 / 9 Mn 1 / 3 Li 1 / 18 Ti 1 / 9 O2 composite cathode (specific steps are the same as in Example 1)

[0064] (III) Assembling the sodium-ion battery (specific steps are the same as in Example 1)

[0065] (iv) Sodium-ion battery testing (specific steps are the same as in Example 1)

[0066] Example 3

[0067] This embodiment provides an O3-type layered oxide cathode material with the chemical formula Na. 5 / 6 Ni 5 / 18 Fe 1 / 9 Mn 1 / 3Cu 1 / 18 Ti 2 / 9 O2. This embodiment also provides a method for preparing and applying the O3-type layered oxide cathode material.

[0068] (I) Preparation of Na 5 / 6 Ni 5 / 18 Fe 1 / 9 Mn 1 / 3 Cu 1 / 18 Ti 2 / 9 O2 cathode material (Step 1, according to Na) 5 / 6 Ni 5 / 18 Fe 1 / 9Mn 1 / 3 Li 1 / 18 Ti 2 / 9 The stoichiometric ratio of each element in O2 is determined by accurately weighing Na2CO3, NiO, Fe2O3, MnO2, CuO, and TiO2. The remaining steps are the same as in Example 1. (II) Preparation of Na 5 / 6 Ni 5 / 18 Fe 1 / 9 Mn 1 / 3 Cu 1 / 18 Ti 2 / 9 O2 composite cathode (specific steps are the same as in Example 1)

[0069] (III) Assembling the sodium-ion battery (specific steps are the same as in Example 1)

[0070] (iv) Sodium-ion battery testing (specific steps are the same as in Example 1)

[0071] Comparative Example 1

[0072] This comparative example provides a NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 cathode materials, their preparation methods, and applications.

[0073] (I) Preparation of NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 cathode material (Step 1, according to NaNi) 1 / 3 Fe 1 / 3 Mn 1 / 3The stoichiometric ratios of each element in O2 are determined by accurately weighing Na2CO3, NiO, Fe2O3, and MnO2. The remaining steps are the same as in Example 1.

[0074] Figure 4 This is a SEM image of the NaNi1 / 3Fe1 / 3Mn1 / 3O2 material in Comparative Example 1 of this invention.

[0075] like Figure 4 As shown, NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 The O2 cathode material consists of sheet-like particles of approximately 1.5 × 0.5 μm with many impurities on its surface.

[0076] Figure 5 NaNi in Comparative Example 1 of this invention 1 / 3 Fe 1 / 3 Mn 1 / 3 XRD pattern of O2 material.

[0077] like Figure 5 As shown, the XRD pattern indicates that the material is an O3 phase with a good layered structure. The (104) peak has the highest intensity, and the ratio of the (003) to (104) peak intensities is I. (003) / I (004) It is 0.58.

[0078] (II) Preparation of NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 composite cathode (specific steps are the same as in Example 1) (III) Assembling sodium-ion batteries (specific steps are the same as in Example 1)

[0079] (iv) Sodium-ion battery testing (specific steps are the same as in Example 1)

[0080] Figure 6 NaNi in Comparative Example 1 of this invention 1 / 3 Fe 1 / 3 Mn 1 / 3 A comparison of the first charge-discharge curves of O2 material before and after it was placed in air.

[0081] From the attached Figure 6 It can be seen from this that NaNi not placed in the air 1 / 3 Fe 1 / 3 Mn 1 / 3 The initial discharge capacity of the O2 material was 133.1 mAh / g. After being placed in the air for 7 days, the discharge capacity of the material was only 43.5 mAh / g, with a decay rate of 67.3%.

[0082] Comparative Example 2

[0083] This comparative example provides a NaNi 2 / 9 Fe 1 / 3 Mn 1 / 3 Cu 1 / 9 O2 cathode materials, their preparation methods, and applications.

[0084] (I) Preparation of NaNi 2 / 9 Fe 1 / 3 Mn 1 / 3 Cu 1 / 9 O2 cathode material (Step 1, according to NaNi) 2 / 9 Fe 1 / 3 Mn 1 / 3 Cu 1 / 9 The stoichiometric ratio of each element in O2 is determined by accurately weighing Na2CO3, NiO, Fe2O3, MnO2, and CuO. The remaining steps are the same as in Example 1.

[0085] (II) Preparation of NaNi 2 / 9 Fe 1 / 3 Mn 1 / 3 Cu 1 / 9 O2 composite cathode (specific steps are the same as in Example 1) (III) Assembling sodium-ion batteries (specific steps are the same as in Example 1)

[0086] (iv) Sodium-ion battery testing (specific steps are the same as in Example 1)

[0087] Comparative Example 3

[0088] This comparative example provides a NaNi 2 / 9 Fe 1 / 3 Mn 2 / 9 Cu 1 / 9 Ti 1 / 9 O2 cathode materials, their preparation methods, and applications.

[0089] (I) Preparation of NaNi 2 / 9 Fe 1 / 3 Mn 2 / 9 Cu 1 / 9 Ti 1 / 9 O2 cathode material (Step 1, according to NaNi) 2 / 9 Fe 1 / 3 Mn 2 / 9 Cu 1 / 9Ti 1 / 9 The stoichiometric ratio of each element in O2 is determined by accurately weighing Na2CO3, NiO, Fe2O3, MnO2, CuO, and TiO2. The remaining steps are the same as in Example 1. (II) Preparation of NaNi 2 / 9 Fe 1 / 3 Mn 2 / 9 Cu 1 / 9 Ti 1 / 9O2 composite cathode (specific steps are the same as in Example 1)

[0090] (III) Assembling the sodium-ion battery (specific steps are the same as in Example 1)

[0091] (iv) Sodium-ion battery testing (specific steps are the same as in Example 1)

[0092] Comparative Example 4

[0093] This comparative example provides a NaNi 5 / 18 Fe 5 / 18 Mn 7 / 18 Li 1 / 18 O2 cathode materials, their preparation methods, and applications.

[0094] (I) Preparation of NaNi 5 / 18 Fe 5 / 18 Mn 7 / 18 Li 1 / 18 O2 cathode material (Step 1, according to NaNi) 5 / 18 Fe 5 / 18 Mn 7 / 18 Li 1 / 18 The stoichiometric ratios of each element in O2 are determined by accurately weighing Na2CO3, NiO, Fe2O3, MnO2, and Li2CO3. The remaining steps are the same as in Example 1.

[0095] (II) Preparation of NaNi 5 / 18 Fe 5 / 18 Mn 7 / 18 Li 1 / 18 O2 composite cathode (specific steps are the same as in Example 1)

[0096] (III) Assembling the sodium-ion battery (specific steps are the same as in Example 1)

[0097] (iv) Sodium-ion battery testing (specific steps are the same as in Example 1)

[0098] Comparative Example 5

[0099] This comparative example provides a NaNi 5 / 18 Fe 5 / 18 Mn 1 / 3 Li 1 / 18 Ti 1 / 18 O2 cathode materials, their preparation methods, and applications.

[0100] (I) Preparation of NaNi 5 / 18 Fe 5 / 18 Mn 1 / 3 Li 1 / 18 Ti 1 / 18 O2 cathode material (Step 1, according to NaNi) 5 / 18 Fe5 / 18 Mn 1 / 3Li 1 / 18 Ti 1 / 18 The stoichiometric ratio of each element in O2 is determined by accurately weighing Na2CO3, NiO, Fe2O3, MnO2, Li2CO3, and TiO2. The remaining steps are the same as in Example 1. (II) Preparation of NaNi 5 / 18 Fe 5 / 18 Mn 1 / 3 Li 1 / 18 Ti 1 / 18 O2 composite cathode (specific steps are the same as in Example 1)

[0101] (III) Assembling the sodium-ion battery (specific steps are the same as in Example 1)

[0102] (iv) Sodium-ion battery testing (specific steps are the same as in Example 1)

[0103] Comparative Example 6

[0104] This comparative example provides a Na 8 / 9 Ni 1 / 3 Fe 2 / 9 Mn 4 / 9 O2 cathode materials, their preparation methods, and applications.

[0105] (I) Preparation of Na 8 / 9 Ni 1 / 3 Fe 2 / 9 Mn 4 / 9 O2 cathode material (Step 1, according to Na) 8 / 9 Ni 1 / 3 Fe 2 / 9 Mn 4 / 9 The stoichiometric ratios of each element in O2 are determined by accurately weighing Na2CO3, NiO, Fe2O3, and MnO2. The remaining steps are the same as in Example 1.

[0106] (II) Preparation of Na 8 / 9 Ni 1 / 3 Fe 2 / 9 Mn 4 / 9 O2 composite cathode (specific steps are the same as in Example 1) (III) Assembling sodium-ion batteries (specific steps are the same as in Example 1)

[0107] (iv) Sodium-ion battery testing (specific steps are the same as in Example 1)

[0108] Comparative Example 7

[0109] This comparative example provides a Na 8 / 9 Ni 1 / 3 Fe 2 / 9 Mn 1 / 3 Ti 1 / 9 O2 cathode materials, their preparation methods, and applications.

[0110] (I) Preparation of Na 8 / 9 Ni 1 / 3 Fe 2 / 9 Mn 1 / 3 Ti 1 / 9 O2 cathode material (Step 1, according to Na) 8 / 9 Ni 1 / 3 Fe 2 / 9 Mn 1 / 3 Ti 1 / The stoichiometric ratio of each element in 9O2 is determined by accurately weighing Na2CO3, NiO, Fe2O3, MnO2, and TiO2. The remaining steps are the same as in Example 1.

[0111] (II) Preparation of Na 8 / 9 Ni 1 / 3 Fe 2 / 9 Mn 1 / 3 Ti 1 / 9 O2 composite cathode (specific steps are the same as in Example 1) (III) Assembling sodium-ion batteries (specific steps are the same as in Example 1)

[0112] (iv) Sodium-ion battery testing (specific steps are the same as in Example 1)

[0113] Comparative Example 8

[0114] This comparative example provides a Na 8 / 9 Ni 5 / 18 Fe 2 / 9 Mn 1 / 3 Cu 1 / 18 Ti 1 / 9 O2 cathode materials, their preparation methods, and applications.

[0115] (I) Preparation of Na 8 / 9 Ni 5 / 18 Fe 2 / 9 Mn 1 / 3 Cu 1 / 18 Ti 1 / 9 O2 cathode material (Step 1, according to Na) 8 / 9 Ni 5 / 18 Fe 2 / 9Mn 1 / 3 Cu 1 / 18 Ti 1 / 9 The stoichiometric ratio of each element in O2 is determined by accurately weighing Na2CO3, NiO, Fe2O3, MnO2, CuO, and TiO2. The remaining steps are the same as in Example 1. (II) Preparation of Na 8 / 9 Ni 5 / 18 Fe 2 / 9 Mn 1 / 3 Cu 1 / 18 Ti 1 / 9O2 composite cathode (specific steps are the same as in Example 1)

[0116] (III) Assembling the sodium-ion battery (specific steps are the same as in Example 1)

[0117] (iv) Sodium-ion battery testing (specific steps are the same as in Example 1)

[0118] Comparative Example 9

[0119] This comparative example provides a Na 8 / 9 Ni 5 / 18 Fe 1 / 6 Mn 1 / 2 Li 1 / 18 O2 cathode materials, their preparation methods, and applications.

[0120] (I) Preparation of Na 8 / 9 Ni 5 / 18 Fe 1 / 6 Mn 1 / 2 Li 1 / 18 O2 cathode material (Step 1, according to Na) 8 / 9 Ni 5 / 18 Fe 1 / 6 Mn 1 / 2Li 1 / 18 The stoichiometric ratios of each element in O2 are determined by accurately weighing Na2CO3, NiO, Fe2O3, MnO2, and Li2CO3. The remaining steps are the same as in Example 1.

[0121] (II) Preparation of Na 8 / 9 Ni 5 / 18 Fe 1 / 6 Mn 1 / 2 Li 1 / 18 O2 composite cathode (specific steps are the same as in Example 1)

[0122] (III) Assembling the sodium-ion battery (specific steps are the same as in Example 1)

[0123] (iv) Sodium-ion battery testing (specific steps are the same as in Example 1)

[0124] Table 1 shows the grain sizes of Examples 1-3 and Comparative Examples 1-9. (003) / I (004) Comparison results of peak intensity ratio and air stability

[0125]

[0126]

[0127] The above test results indicate that increasing particle size and improving the (003) crystal plane strength can enhance the air stability of O3-type sodium cathode materials. A comparison of Examples 1-3 and Comparative Examples 1-5 reveals that doping with metal elements alone does not improve the air stability of NaNi. 1 / 3 Fe 1 / 3Mn 1 / 3 The increase in grain size and the improvement in (003) peak intensity of O2 materials are limited. A comparison of Examples 1-3 with Comparative Examples 1 and 6 reveals that simply reducing the sodium content (NaNi) is insufficient. 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 has limited effect on grain size growth and (003) peak intensity improvement. This is observed in comparisons of Examples 1-3 and Comparative Examples 1, 7, 8, and 9. Li doping has a limited effect on NaNi. 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 grain growth plays a significant role, but Li doping and Na vacancy design alone limit the material's specific capacity. Therefore, this invention improves NaNi by combining Li doping, transition metal doping, and sodium vacancy design. 1 / 3 Fe 1 / 3 Mn 1 / 3 The composite cathode material obtained by measuring the grain size of O2 material and the diffraction peak intensity of (003) exhibits good air stability and high specific capacity.

[0128] In summary, this invention synthesizes Na through Li doping, transition metal doping, and sodium vacancy design. x Ni a Fe b Mn c Li d M e O2-type (0.8≤x≤1.0, a+b+c+d+e=1, 0.10≤a,b,c≤0.50, 0.02≤d≤0.06, 0.05≤M≤0.20) cathode material. Compared to the original NaNi... 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 material exhibits larger particle size, higher (003) crystal plane strength, and lower surface residual alkali content. This type of sodium-ion cathode material demonstrates good air stability and high discharge specific capacity at room temperature. This invention primarily improves the air stability of the material by controlling the grain size and (003) crystal plane strength. This method is simple, efficient, low-cost, and suitable for industrial production. The O3-type sodium-ion layered material obtained using this method is inexpensive, easy to store and transport, and has high energy density, showing promising application prospects.

[0129] Those skilled in the art will appreciate that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An O3-type layered oxide cathode material, characterized in that, The chemical formula is: Na x Ni a Fe b Mn c Li d M e O2, where 0.83≤x≤0.95, a+b+c+d+e=1, 0.10 ≤a, b, c≤0.50, 0.02≤d≤0.06, 0.05≤M≤0.20, where M is at least one of the transition metals Ti, Cr, Co, Cu, and Zn.

2. The method for preparing the O3-type layered oxide cathode material as described in claim 1, characterized in that, Includes the following steps: Step 1, according to the chemical formula Na x Ni a Fe b Mn c Li d M e The molar ratio of each element in O2 is determined by weighing the precursors of Na, Ni, Fe, Mn, Li, and M. Step 2: Place the precursors corresponding to each element in a ball mill and ball mill them to obtain precursor powder; Step 3: Compress the precursor powder into tablets to obtain powder tablets; Step 4: Calcine the powder sheet in an oxygen atmosphere to obtain O3-type layered oxide cathode material.

3. The method for preparing the O3-type layered oxide cathode material according to claim 1, characterized in that: in, In step 1, the precursors of Na and Li are selected from their carbonates, nitrates and oxides, while the precursors of other elements are selected from their oxides.

4. The method for preparing the O3-type layered oxide cathode material according to claim 1, characterized in that: in, In step 2, the ball mill rotates at a speed of not less than 400 rpm and the ball milling time is not less than 6 hours.

5. The method for preparing the O3-type layered oxide cathode material according to claim 1, characterized in that: in, In step 3, the pressure for tablet compression shall not be less than 10 MPa, and the holding time shall not be less than 1 min.

6. The method for preparing the O3-type layered oxide cathode material according to claim 1, characterized in that: in, In step 4, the heating rate for calcination shall not exceed 5℃ / min, the sintering temperature shall not be lower than 850℃, the holding time shall not be lower than 12h, and the cooling rate shall be 1-3℃ / min.

7. The method for preparing the O3-type layered oxide cathode material according to claim 1, characterized in that: in, The O3-type layered oxide cathode material has a large grain size, high (003) crystal plane strength, and a small amount of surface residual alkali.

8. The application of the O3-type layered oxide cathode material as described in claim 1 as a cathode material for sodium-ion batteries.

9. The application according to claim 8, characterized in that: in, The application involves mixing the O3-type layered oxide cathode material with conductive additives, binders, and solvents in a predetermined ratio, followed by slurry preparation, coating, and drying to obtain a composite cathode.

10. A sodium-ion battery, characterized in that, include: The composite consists of a positive electrode, a separator, an organic electrolyte, and a negative electrode. The composite cathode includes the O3-type layered oxide cathode material. The diaphragm is any one of glass fiber diaphragm, ceramic diaphragm, and polymer diaphragm. The organic electrolyte is a carbonate electrolyte, with the solvent selected from at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC), and the solute selected from at least one of sodium hexafluorophosphate (NaPF6), sodium perchlorate (NaClO4), and sodium bis(trifluoromethanesulfonyl)imide (NaTFSI). The negative electrode is any one of metallic sodium, metal oxide, and hard carbon.

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