Layered oxide positive electrode material and preparation method thereof, and application to sodium battery

Abstract

The application relates to the technical field of battery materials, in particular to a layered oxide positive electrode material, a preparation method thereof and application to a sodium battery. The expression of the layered oxide positive electrode material is: AB2Y2X2O12, wherein, A is a sodium storage layer site doping element, B is a transition metal layer cation site doping element, C is a transition metal layer anion site doping element, and Y is a shuttle ion doping element. In the charging and discharging process of the layered oxide positive electrode material, the shuttle ion shuttles between the transition metal layer and the sodium storage layer, which can improve the stability and sodium ion diffusion rate of the material, and effectively solve the problems of unstable iron-manganese-based layer oxygen circulation, low coulomb efficiency and slow sodium ion diffusion rate.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, specifically to a layered oxide cathode material and its preparation method, and its application in sodium batteries. Background Technology

[0002] Among the many battery materials, sodium-ion batteries have received widespread attention due to their advantages such as low development cost, high safety, and wide temperature range adaptability.

[0003] Sodium-ion battery cathode materials are mainly classified into three categories: layered oxides, Prussian blue compounds, and polyanionic materials. Among them, layered oxides are the most promising cathode materials for sodium-ion batteries due to their high specific capacity, suitable operating voltage, high energy density, low cost, and relatively simple synthesis process. However, these materials are prone to harmful phase transitions and structural degradation during charge-discharge cycles, leading to ion channel blockage and hindered sodium ion diffusion, severely affecting their long-term cycle stability. These unfavorable factors limit the practical application and industrialization of layered oxide cathodes.

[0004] Currently, the ion doping modification techniques for improving layered oxide cathode materials in sodium-ion batteries are all based on doping at specific sites. After doping, the dopant element is anchored in that specific site and does not move. While this site-based doping can improve the stability of the material structure to some extent and enhance the ion diffusion ability of sodium ions in specific regions of the material by changing the valence state and electronegativity of surrounding ions, as sodium ions continuously insert and extract during the charge and discharge process, the sites farther away from the dopant element sites gradually begin to deform. Furthermore, the increased rigidity of the doped sites leads to insufficient material flexibility, causing stress to accumulate continuously and making it more prone to irreversible distortion. As a result, the material's performance in long-term cycling remains unsatisfactory.

[0005] Therefore, providing a novel layered oxide cathode material and its preparation method, as well as its application in sodium batteries, has become a pressing technical problem to be solved in this field. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a layered oxide cathode material and its preparation method, as well as its application in sodium batteries. This material can improve the stability of the material and the sodium ion diffusion rate, effectively solving the problems of unstable oxygen cycling, low coulombic efficiency, and slow sodium ion diffusion rate in iron-manganese substrates.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] This invention provides a layered oxide cathode material, characterized in that the expression for the layered oxide cathode material is: ,in, , , , , Dopant element A is used for sodium storage layer site doping, dopant element B is used for transition metal layer cation site doping, dopant element C is used for transition metal layer anion site doping, and dopant element Y is used as shuttle ion doping. During the charging and discharging process of the layered oxide cathode material, the shuttle ions shuttle between the transition metal layer and the sodium storage layer.

[0009] According to one embodiment of the present invention, the dopant element A includes at least one of Ca and K; the dopant element B includes at least one of Cu, Ti, Mg, Al, Zn, Nb, Ru and B; the dopant element C includes at least one of F and S; and the dopant element Y includes at least one of Sn, Ni and Li.

[0010] Another aspect of the present invention provides a method for preparing a layered oxide cathode material, comprising the following steps:

[0011] S1: Sodium source, iron source, manganese source, metal oxide powder of doping element A, metal oxide powder of doping element B and metal oxide powder of doping element C are added to anhydrous ethanol according to the stoichiometric ratio and then subjected to wet ball milling and vacuum filtration to obtain the first mixed powder.

[0012] S2: The first mixed powder is sequentially dried and calcined to obtain precursor cathode powder;

[0013] S3: The precursor cathode powder and the metal oxide powder doped with element Y are subjected to dry ball milling to obtain a second mixed powder, and the second mixed powder is subjected to a second calcination treatment to obtain cathode material powder, wherein the amount of metal oxide powder doped with element Y added is 2%-8% of the total molar mass of the precursor cathode powder.

[0014] According to one embodiment of the present invention, in step S1, the wet ball milling time is 1-10 hours; in step S2, the drying temperature is 60-80°C, the calcination temperature is 400-600°C, and the time is 5-10 hours; in step S3, the dry ball milling time is 1-10 hours, and the secondary calcination temperature is 850-1020°C, and the time is 10-15 hours.

[0015] Another aspect of the present invention provides a method for preparing a layered oxide cathode material, comprising the following steps:

[0016] S1: Dissolve iron source, manganese source, inorganic acid salt powder of doped element A, inorganic acid salt powder of doped element B, and inorganic acid salt powder of doped element C in deionized water according to stoichiometric ratio. Pump the dissolved mixed solution into a reaction vessel, add precipitant and acid-base adjuster to obtain a suspension. Then, perform vacuum filtration and drying treatment on the suspension in sequence to obtain the first mixed powder.

[0017] S2: The first mixed powder is dry ball-milled and calcined with sodium source, the easily hydrolyzable salt powder of dopant element B and dopant element C to obtain precursor cathode powder.

[0018] S3: The precursor cathode powder and the metal oxide powder doped with element Y are subjected to dry ball milling to obtain a second mixed powder, and the second mixed powder is subjected to a second calcination treatment to obtain cathode material powder, wherein the amount of metal oxide powder doped with element Y added is 2%-8% of the total molar mass of the precursor cathode powder.

[0019] According to one embodiment of the present invention, in step S1, the precipitant includes sodium hydroxide or sodium carbonate, and the acid-base regulator includes ammonia or urea.

[0020] According to one embodiment of the present invention, in step S1, the temperature of the mixed solution is 80-150℃, the pH value is 5-6, and the stirring speed of the reaction vessel is 150-350 rpm; in step S2, the drying treatment temperature is 60-80℃, the dry ball milling time is 1-10 hours, and the calcination treatment temperature is 400-600℃ for 5-10 hours; in step S3, the dry ball milling time is 1-10 hours, and the secondary calcination treatment temperature is 850-1020℃ for 10-15 hours.

[0021] In another aspect, the present invention provides a positive electrode, comprising the layered oxide positive electrode material described above or a positive electrode material prepared by the method for preparing the layered oxide positive electrode material described above.

[0022] Another aspect of the present invention provides a sodium-ion battery, comprising the layered oxide cathode material described above, or a cathode material prepared by the method for preparing the layered oxide cathode material described above, or the cathode described above.

[0023] Another aspect of the present invention provides an electrical device including the aforementioned sodium-ion battery.

[0024] Beneficial effects: The formula for the layered oxide cathode material of the present invention is as follows: ,in, , , , , Dopant element A is used for sodium storage layer site doping, dopant element B is used for transition metal layer cation site doping, dopant element C is used for transition metal layer anion site doping, and dopant element Y is used as shuttle ion doping. During the charging and discharging process of the layered oxide cathode material, the shuttle ions shuttle between the transition metal layer and the sodium storage layer. By performing three-point doping on the sodium storage layer sites, transition metal layer cation sites, and transition metal layer anion sites, and simultaneously introducing shuttle ions into the space between the transition metal layer and the sodium storage layer, the shuttle ions dynamically fill the vacancies between the sodium storage layer and the transition metal layer during the charging and discharging process. This increases the material's flexibility, releases accumulated stress, and acts as a sodium ion channel lubricant. When the shuttle ions shuttle between the transition metal layer and the sodium storage layer, the three-point doping method stabilizes the basic material structure, thereby improving the material's structural stability and the diffusion rate of sodium ions in the material. Attached Figure Description

[0025] Figure 1 This is a schematic flowchart of a method for preparing a layered oxide cathode material according to an embodiment of the present invention.

[0026] Figure 2 This is a schematic flowchart of a method for preparing a layered oxide cathode material according to another embodiment of the present invention.

[0027] Figure 3 These are scanning electron microscope (SEM) images of the layered oxide cathode materials prepared in Examples 1 and 2 of the present invention; wherein, (a) is the SEM image of Example 1 and (b) is the SEM image of Example 2.

[0028] Figure 4 This is an X-ray diffraction pattern of the layered oxide cathode material prepared in Example 1 of the present invention.

[0029] Figure 5 The layered oxide cathode material prepared in Example 1 of this invention performs at 100 mA in a sodium-ion coin cell. Charge-discharge curves for the first two cycles of the next cycle.

[0030] Figure 6 The layered oxide cathode material prepared in Example 1 of this invention performs at 100 mA in a sodium-ion coin cell. Cyclic stability under [condition / condition]. Detailed Implementation

[0031] The technical solution of the present invention will be illustrated below through specific embodiments. All raw materials and reagents used in the present invention are commercially available.

[0032] An embodiment of the present invention discloses a layered oxide cathode material, the expression of which is: ,in, , , , , Dopant element A is used for sodium storage layer site doping, dopant element B is used for transition metal layer cation site doping, dopant element C is used for transition metal layer anion site doping, and dopant element Y is used as shuttle ion doping. During the charging and discharging process of the layered oxide cathode material, shuttle ions shuttle between the transition metal layer and the sodium storage layer.

[0033] Wherein, dopant A includes at least one of Ca and K; dopant B includes at least one of Cu, Ti, Mg, Al, Zn, Nb, Ru and B; dopant C includes at least one of F and S; and dopant Y includes at least one of Sn, Ni and Li.

[0034] Previous modifications to layered oxide cathode materials have largely focused on a single dimension: either improving structural stability through single-site doping or alleviating stress by introducing a rigid framework (such as a carbon coating), but none have addressed the issue of "dynamic structural changes during charge and discharge." The layered oxide cathode material of this invention employs three-site doping of the sodium storage layer, the transition metal layer cation sites, and the transition metal layer anion sites, while simultaneously introducing shuttle ions between the transition metal layer and the sodium storage layer. During charge and discharge, the shuttle ions dynamically fill the vacancies between the sodium storage layer and the transition metal layer, increasing material flexibility, releasing accumulated stress, and acting as a sodium ion channel lubricant. When the shuttle ions shuttle between the transition metal layer and the sodium storage layer, the three-site doping stabilizes the basic material architecture, thereby improving the material's structural stability and the diffusion rate of sodium ions within the material. This invention effectively solves the problems of unstable cycling, low coulombic efficiency, and slow sodium ion diffusion rate in layered oxide materials through a composite strategy of "three-site doping to construct a statically stable substrate + shuttle ions to achieve dynamic process control."

[0035] Please see Figure 1 The present invention discloses a method for preparing a layered oxide cathode material, which is a solid-state reaction synthesis method, including the following steps:

[0036] S1: Sodium source, iron source, manganese source, metal oxide powder of dopant element A, metal oxide powder of dopant element B, and metal oxide powder of dopant element C are added to anhydrous ethanol in stoichiometric ratio and then subjected to wet ball milling and filtration to obtain the first mixed powder.

[0037] In step S1, the sodium source includes at least one of sodium carbonate and sodium hydroxide; the iron source includes at least one of ferric oxalate, ferric phosphate, and ferric nitrate; and the manganese source includes at least one of manganese dioxide and manganese acetate. Dopant element A includes at least one of Ca and K; for example, the calcium source includes at least one of calcium carbonate, calcium oxalate, calcium oxide, calcium hydroxide, and calcium bicarbonate. Dopant element B includes at least one of Cu, Ti, Mg, Al, Zn, Nb, Ru, and B; for example, the magnesium source includes at least one of magnesium carbonate, magnesium oxide, and magnesium hydroxide. Dopant element C includes at least one of F and S; for example, the fluorine source includes sodium fluoride, and the sulfur source includes sodium sulfide.

[0038] In this step, anhydrous ethanol is used as the ball milling medium to ball mill the sodium source, iron source, manganese source, metal oxide powder of doped element A, metal oxide powder of doped element B, and metal oxide powder of doped element C. The wet ball milling time is 1-10 hours. After ball milling, the slurry is transferred to a Buchner funnel and the solid is separated by vacuum filtration to obtain a filter cake-like first mixed powder.

[0039] S2: The first mixed powder is dried and calcined in sequence to obtain the precursor cathode powder.

[0040] In step S2, the first mixed powder is transferred to a vacuum drying oven and dried at 60-80℃ for 8 hours, with the filter cake turned over every 2 hours to ensure complete evaporation of anhydrous ethanol. The dried powder is then placed in a Marff furnace and calcined at 400-600℃ for 5-10 hours to promote the initial reaction between the sodium source and the transition metal source to form a layered precursor, while simultaneously fixing the distribution of dopant elements A, B, and C, resulting in... Powder, namely precursor cathode powder.

[0041] S3: The precursor cathode powder and the metal oxide powder doped with element Y are subjected to dry ball milling to obtain a second mixed powder, and the second mixed powder is subjected to secondary calcination to obtain cathode material powder, wherein the amount of metal oxide powder doped with element Y added is 2%-8% of the total molar mass of the precursor cathode powder.

[0042] In step S3, the amount of metal oxide powder containing dopant element Y added is 2%-8% of the total molar mass of the precursor cathode powder. For example, if the precursor cathode powder mass is 10g, the mass of oxide containing dopant element Y is 0.2-0.8g. Dopant element Y includes at least one of Sn, Ni, and Li. Specifically, the metal oxide containing shuttle ions Y is uniformly dispersed in the precursor cathode powder by dry ball milling, followed by a second calcination to achieve controllable doping of shuttle ions Y, ultimately obtaining a cathode material with three-point doping + shuttle ion characteristics, i.e. The dry ball milling time is 1-10 hours, and the secondary calcination treatment temperature is 850-1020℃, and the time is 10-15 hours.

[0043] The method for preparing the layered oxide cathode material in this invention introduces shuttle ion doping between the transition metal layer and the sodium storage layer. During the charging and discharging process of the cathode material, shuttle ions shuttle between the transition metal layer and the sodium storage layer. When sodium is released during charging, the shuttle ions diffuse into the sodium storage layer, stabilizing the sodium ion channels, guiding sodium ion diffusion, and connecting the transition metal layer. When sodium is inserted during discharging, the shuttle ions re-inserte into the transition metal layer, filling vacancies, stabilizing the layered framework of the material, and releasing stress in the transition metal layer. This further stabilizes the cycle stability of the sodium ion layered oxide cathode material and improves the sodium ion diffusion rate.

[0044] Furthermore, when shuttle ions shuttle between the transition metal layer and the sodium storage layer, this invention stabilizes the basic material architecture by using three-point doping, thereby preventing structural instability that may occur during shuttle ion transport. Therefore, the stable cycle performance of the cathode material is achieved through the synergistic effect of three-point doping combined with shuttle ion doping.

[0045] Furthermore, this preparation method has a simple synthetic route, does not cause environmental pollution, uses inexpensive raw materials, and has high feasibility for mass production and practical application value.

[0046] Please see Figure 2 The present invention discloses a method for preparing a layered oxide cathode material, which is a co-precipitation synthesis method, including the following steps:

[0047] S1: Dissolve iron source, manganese source, inorganic acid salt powder of doping element A, inorganic acid salt powder of doping element B, and inorganic acid salt powder of doping element C in deionized water according to the stoichiometric ratio. Pump the dissolved mixed solution into the reaction vessel, add precipitant and acid-base adjuster to obtain a suspension. Then, filter and dry the suspension in sequence to obtain the first mixed powder.

[0048] In step S1, the iron source is selected manganese source selection Dopant A includes at least one of Ca and K; dopant B includes at least one of Cu, Ti, Mg, Al, Zn, Nb, Ru, and B; and dopant C includes at least one of F and S. The sources of dopant A, dopant B, and dopant C include at least one of hydrochloride, sulfate, and nitrate. The precipitant includes sodium hydroxide or sodium carbonate, and the acid-base adjuster includes ammonia or urea. In this step, iron and manganese sources, as well as the metal sulfate powders of dopant A, B, and C, are dissolved in deionized water according to stoichiometric ratios. The resulting mixed solution is pumped into a reaction vessel, and the temperature of the mixed solution is controlled at 80-150℃. The stirring speed of the reaction vessel is 150-350 rpm. The precipitant and acid-base adjuster are added to control the pH value at 5-6. / , Hydroxide precipitate is formed simultaneously with the dopant ions through a co-precipitation reaction; after the reaction is completed, the mixture is naturally cooled to room temperature, and the suspension is transferred to a Buchner funnel for filtration until no obvious liquid seeps out from the surface of the filter cake; the filter cake is transferred to a vacuum drying oven and dried at 60-80℃ for 6 hours to remove water and obtain the first mixed powder.

[0049] S2: The first mixed powder is dry ball-milled and calcined with sodium source, dopant element B and dopant element C, which are easily hydrolyzable salt powders, to obtain precursor cathode powder.

[0050] In step S2, the first mixed powder is mixed uniformly with sodium source, dopant element B and easily hydrolyzable salt powder of dopant element C (such as titanium oxide, sodium fluoride, etc.) by dry ball milling for 1-10 hours; then calcined to allow the sodium source to react with the first mixed powder to generate a layered oxide precursor, while the easily hydrolyzable salt releases acidic gas or forms a specific doped structure during calcination. The calcination temperature is 400-600℃ and the time is 5-10 hours.

[0051] S3: The precursor cathode powder and the metal oxide powder doped with element Y are subjected to dry ball milling to obtain a second mixed powder, and the second mixed powder is subjected to secondary calcination to obtain cathode material powder, wherein the amount of metal oxide powder doped with element Y added is 2%-8% of the total molar mass of the precursor cathode powder.

[0052] In step S3, the precursor cathode powder and the metal oxide of doped element Y are mixed by dry ball milling for 1-10 hours. Then, the doped element Y ions are calcined twice to allow them to enter the crystal lattice, forming ions that can shuttle between the transition metal layer and the sodium storage layer, thus giving the material dynamic stress buffering and ion transport lubrication functions. The temperature of the second calcination treatment is 850-1020℃ and the time is 10-15 hours.

[0053] The method for preparing the layered oxide cathode material in this invention introduces shuttle ion doping between the transition metal layer and the sodium storage layer. During the charging and discharging process of the cathode material, shuttle ions shuttle between the transition metal layer and the sodium storage layer. When sodium is released during charging, the shuttle ions diffuse into the sodium storage layer, stabilizing the sodium ion channels, guiding sodium ion diffusion, and connecting the transition metal layer. When sodium is inserted during discharging, the shuttle ions re-inserte into the transition metal layer, filling vacancies, stabilizing the layered framework of the material, and releasing stress in the transition metal layer. This further stabilizes the cycle stability of the sodium ion layered oxide cathode material and improves the sodium ion diffusion rate.

[0054] Furthermore, when shuttle ions shuttle between the transition metal layer and the sodium storage layer, this invention stabilizes the basic material architecture by using three-point doping, thereby preventing structural instability that may occur during shuttle ion transport. Therefore, the stable cycle performance of the cathode material is achieved through the synergistic effect of three-point doping combined with shuttle ion doping.

[0055] Furthermore, this preparation method has a simple synthetic route, does not cause environmental pollution, uses inexpensive raw materials, and has high feasibility for mass production and practical application value.

[0056] Example 1

[0057] This embodiment discloses a method for preparing a layered oxide cathode material, including the following steps: [The following text appears to be a separate, unrelated section:] ...in accordance with stoichiometric ratios... MgO, CuO , , , Powders of ZnO and NaF were mixed in anhydrous ethanol. The mixture was then placed in a ball mill and ground at 400-600 rpm for 1-10 hours. The ground mixture was then filtered to obtain a first mixed powder. The first mixed powder was placed in an oven and dried at 60-80℃. The dried powder was then placed in a Marfenf furnace and calcined at 400-600℃ for 5-10 hours to obtain the precursor cathode powder. ; mix the precursor cathode powder with powder( The powder (5% of the total molar mass of the precursor cathode powder) is added to a ball mill jar and mixed by dry ball milling for 1-10 hours to obtain a second mixed powder. The second mixed powder is then placed in a Marff furnace and calcined at 850-1020℃ for 10-15 hours to obtain the cathode material powder. .

[0058] This embodiment also discloses a positive electrode, including the layered oxide positive electrode material prepared in this embodiment.

[0059] This embodiment also discloses a sodium-ion battery, including the layered oxide cathode material prepared in this embodiment or the cathode of this embodiment.

[0060] Example 2

[0061] This embodiment discloses a method for preparing a layered oxide cathode material, including the following steps: [The following text appears to be a separate, unrelated section:] ...in accordance with stoichiometric ratios... , , , , as well as Dissolve in deionized water, pump the dissolved mixture into a reaction vessel, add sodium hydroxide and ammonia, control the temperature of the mixture at 80-150℃, the stirring speed of the reaction vessel at 150-350 rpm, and control the pH at 5-6 to obtain a suspension. Then, filter the suspension and dry it in an oven at 60-80℃ to obtain the first mixed powder. The first mixed powder is then combined with... , Dry ball milling of NaF for 1-10 hours, then placing the mixed powder in a Marfir furnace and calcining at 400-600℃ for 5-10 hours to obtain precursor cathode powder. ; mix the precursor cathode powder with powder( The powder (5% of the total molar mass of the precursor cathode powder) is added to a ball mill jar and mixed by dry ball milling for 1-10 hours to obtain a second mixed powder. The second mixed powder is then placed in a Marff furnace and calcined at 850-1020℃ for 10-15 hours to obtain the cathode material powder. .

[0062] This embodiment also discloses a positive electrode, including the layered oxide positive electrode material prepared in this embodiment.

[0063] This embodiment also discloses a sodium-ion battery, including the layered oxide cathode material prepared in this embodiment or the cathode of this embodiment.

[0064] Example 3

[0065] This embodiment discloses a method for preparing a layered oxide cathode material. The only difference between this embodiment and Embodiment 1 is that... The amount of powder added was 2.5% of the total molar mass of the precursor cathode powder, resulting in the precursor cathode powder being... The positive electrode material powder obtained is .

[0066] This embodiment also discloses a positive electrode, including the layered oxide positive electrode material prepared in this embodiment.

[0067] This embodiment also discloses a sodium-ion battery, including the layered oxide cathode material prepared in this embodiment or the cathode of this embodiment.

[0068] Example 4

[0069] This embodiment discloses a method for preparing a layered oxide cathode material. The only difference between this embodiment and Embodiment 1 is that... The amount of powder added is 8% of the total molar mass of the precursor cathode powder, resulting in precursor cathode powder of the following composition: The positive electrode material powder obtained is .

[0070] This embodiment also discloses a positive electrode, including the layered oxide positive electrode material prepared in this embodiment.

[0071] This embodiment also discloses a sodium-ion battery, including the layered oxide cathode material prepared in this embodiment or the cathode of this embodiment.

[0072] Comparative Example 1

[0073] This comparative example discloses a method for preparing a layered oxide cathode material. The only difference between this comparative example and Example 1 is that this comparative example does not include... Powder, to obtain precursor cathode powder .

[0074] This embodiment also discloses a positive electrode, including the layered oxide positive electrode material prepared in this embodiment.

[0075] This embodiment also discloses a sodium-ion battery, including the layered oxide cathode material prepared in this embodiment or the cathode of this embodiment.

[0076] test

[0077] (1) The layered oxide cathode materials prepared in Examples 1 and 2 were subjected to scanning electron microscopy, and the morphology images are shown below. Figure 3 As shown; where, Figure 3 (a) is a morphological diagram of Example 1. Figure 3 (b) is a morphological diagram of Example 2.

[0078] (2) The layered oxide cathode material prepared in Example 1 was subjected to XRD testing, and the test results are as follows: Figure 4 As shown.

[0079] (3) Electrochemical performance tests were performed on the sodium-ion batteries prepared in Examples 1-4 and Comparative Example 1, including:

[0080] The prepared positive electrode sheet was combined with metallic sodium (approximately 1 mm thick) to form a CR2032 button cell in an Ar-filled glove box. The separator was Whatman GF / D glass fiber, the electrolyte was a 1 mol / L NaPF6 solution, and the solvent was EC (ethylene carbonate) / diethyl carbonate (DEC) (v:v = 1:1), containing 5 vol% fluoroethylene carbonate (FEC) additive.

[0081] The obtained CR2032 button cell was tested at 100 mA using the Newway battery testing system. Constant current charge-discharge experiments were conducted under conditions of a current density of 2.2-4V and a voltage range of 2.2-4V. The test results are shown in Table 1. Among them, the layered oxide cathode material prepared in Example 1 was tested in a sodium-ion coin cell at 100mA. The charge / discharge curves for the first two cycles of the next cycle are as follows: Figure 5 As shown; the layered oxide cathode material prepared in Example 1 was tested at 100 mA in a sodium-ion coin cell. Cyclic stability as follows Figure 6 As shown.

[0082] Table 1: Electrochemical performance test results of Examples 1-4 and Comparative Example 1.

[0083]

[0084] Table 1 shows that in the solid-state reaction synthesis route, when the molar proportion of shuttle ions is 5%, the resulting three-site and shuttle ion-doped layered oxide cathode material exhibits excellent specific capacity and stable cycle performance, achieving a high specific capacity (1C current discharge capacity of 95.5 mAh g⁻¹). −1 Simultaneously, optimal cycle stability (94.2% capacity retention after 200 cycles) was achieved. In the co-precipitation synthesis route, when the molar proportion of shuttle ions added was 5%, the electrochemical performance of the three-site and shuttle ion-doped layered oxide cathode material was similar to that of the layered oxide cathode material prepared by the solid-state reaction synthesis route, but the bulk morphology (e.g., ...) of the material prepared by the solid-state reaction synthesis route was different. Figure 3 (a) is different; the coprecipitation method synthesizes spherical morphologies (e.g., Figure 3 (b) Therefore, the initial specific capacity and cycle stability are different.

[0085] In Comparative Example 1, the layered oxide cathode material without shuttle ion doping exhibits relatively low cycle stability due to continuous stress accumulation and insufficient material flexibility. In Examples 1-4, the addition of shuttle ion doping significantly improves cycle stability. Furthermore, varying the amount of shuttle ions added results in different numbers of vacancies formed in the sodium storage layer and transition metal layer during charge / discharge operation, leading to changes in the material's capacity and cycle stability. In the comparison between the examples and the comparative examples, a shuttle ion molar ratio of 5% demonstrates the best performance.

[0086] The above are merely embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A layered oxide cathode material, characterized in that, The expression for the layered oxide cathode material is: ,in, , , , , Dopant element A is used for sodium storage layer site doping, dopant element B is used for transition metal layer cation site doping, dopant element C is used for transition metal layer anion site doping, and dopant element Y is used as shuttle ion doping. During the charging and discharging process of the layered oxide cathode material, the shuttle ions shuttle between the transition metal layer and the sodium storage layer. The preparation method of the layered oxide cathode material includes the following steps: S1: Sodium source, iron source, manganese source, metal oxide powder of doping element A, metal oxide powder of doping element B and metal oxide powder of doping element C are added to anhydrous ethanol according to the stoichiometric ratio and then subjected to wet ball milling and vacuum filtration to obtain the first mixed powder. S2: The first mixed powder is sequentially dried and calcined to obtain precursor cathode powder; S3: The precursor cathode powder and the metal oxide powder doped with element Y are subjected to dry ball milling to obtain a second mixed powder, and the second mixed powder is subjected to a second calcination treatment to obtain cathode material powder, wherein the amount of metal oxide powder doped with element Y added is 2%-8% of the total molar mass of the precursor cathode powder; The doping element A includes at least one of Ca and K; the doping element B includes at least one of Cu, Ti, Mg, Al, Zn, Nb, Ru and B; the doping element C includes at least one of F and S; and the doping element Y includes at least one of Sn, Ni and Li.

2. The layered oxide cathode material according to claim 1, characterized in that, In step S1, the wet ball milling time is 1-10 hours; in step S2, the drying temperature is 60-80℃, the calcination temperature is 400-600℃, and the time is 5-10 hours; in step S3, the dry ball milling time is 1-10 hours, and the secondary calcination temperature is 850-1020℃, and the time is 10-15 hours.

3. A layered oxide cathode material, characterized in that, The expression for the layered oxide cathode material is: ,in, , , , , Dopant element A is used for sodium storage layer site doping, dopant element B is used for transition metal layer cation site doping, dopant element C is used for transition metal layer anion site doping, and dopant element Y is used as shuttle ion doping. During the charging and discharging process of the layered oxide cathode material, the shuttle ions shuttle between the transition metal layer and the sodium storage layer. The preparation method of the layered oxide cathode material includes the following steps: S1: Dissolve iron source, manganese source, inorganic acid salt powder of doped element A, inorganic acid salt powder of doped element B, and inorganic acid salt powder of doped element C in deionized water according to stoichiometric ratio. Pump the dissolved mixed solution into a reaction vessel, add precipitant and acid-base adjuster to obtain a suspension. Then, perform vacuum filtration and drying treatment on the suspension in sequence to obtain the first mixed powder. S2: The first mixed powder is dry ball-milled and calcined with sodium source, the easily hydrolyzable salt powder of dopant element B and dopant element C to obtain precursor cathode powder. S3: The precursor cathode powder and the metal oxide powder doped with element Y are subjected to dry ball milling to obtain a second mixed powder, and the second mixed powder is subjected to a second calcination treatment to obtain cathode material powder, wherein the amount of metal oxide powder doped with element Y added is 2%-8% of the total molar mass of the precursor cathode powder; The doping element A includes at least one of Ca and K; the doping element B includes at least one of Cu, Ti, Mg, Al, Zn, Nb, Ru and B; the doping element C includes at least one of F and S; and the doping element Y includes at least one of Sn, Ni and Li.

4. The layered oxide cathode material according to claim 3, characterized in that, In step S1, the precipitant includes sodium hydroxide or sodium carbonate, and the acid-base adjuster includes ammonia or urea.

5. The layered oxide cathode material according to claim 3, characterized in that, In step S1, the temperature of the mixed solution is 80-150℃, the pH value is 5-6, the stirring speed of the reaction vessel is 150-350 rpm, and the drying temperature is 60-80℃; in step S2, the dry ball milling time is 1-10 hours, the calcination temperature is 400-600℃, and the time is 5-10 hours; in step S3, the dry ball milling time is 1-10 hours, and the secondary calcination temperature is 850-1020℃, and the time is 10-15 hours.

6. A positive electrode, characterized in that, It includes the layered oxide cathode material as described in any one of claims 1 to 2 or the layered oxide cathode material as described in any one of claims 3 to 5.

7. A sodium-ion battery, characterized in that, It includes the layered oxide cathode material as described in any one of claims 1 to 2, or the layered oxide cathode material as described in any one of claims 3 to 5, or the cathode as described in claim 6.

8. An electrical appliance, characterized in that, Including the sodium-ion battery as described in claim 7.

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