Single-crystal layered oxide cathode material, preparation method thereof and sodium ion battery

Abstract

The application provides a single-crystal layered oxide positive electrode material, a preparation method thereof and a sodium ion battery. The method comprises the following steps: preparing a mixed metal sulfate solution containing different metal elements; performing spray drying on the mixed metal sulfate solution to obtain a mixed metal sulfate powder; performing a first sintering treatment on the mixed metal sulfate powder to obtain a mixed metal oxide precursor; and performing a second sintering treatment on the mixed metal oxide precursor and a sodium source to obtain the single-crystal layered oxide positive electrode material. The application first performs spray drying pretreatment on a mixed metal sulfate solution as a raw material, and then utilizes two sintering treatments to prepare a large-size single-crystal layered oxide sodium ion battery positive electrode material, so that the technical problem of serious agglomeration of the sulfate is avoided.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sodium ion battery cathode materials, and particularly relates to a single-crystal layered oxide cathode material, a preparation method thereof and a sodium ion battery. BACKGROUND

[0002] Lithium ion batteries have dominated portable electronic devices and new energy vehicles. As one of the important raw materials of lithium ion batteries, the price of lithium has a periodic price fluctuation risk in recent years. Therefore, people strive to find a next-generation electrochemical energy storage technology that can replace lithium ion batteries, be applied on a large scale, and be environmentally friendly. Sodium and lithium are in the same main group and have many similar physical and chemical properties, and their reserves are much higher than those of lithium, which makes sodium ion batteries have an advantage in raw material supply, thereby helping to reduce production costs and reduce dependence on lithium resources.

[0003] The cathode material of a sodium ion battery is one of the main factors that determine the performance and cost of the battery, which mainly includes three categories of Prussian blue compounds, layered transition metal compounds, and polyanion compounds. Among them, layered transition metal compounds have outstanding advantages in energy density, cycle life, and material cost, and are the most promising cathode material for industrialization. At present, layered transition metal compounds are mostly obtained by co-precipitation method to obtain a precursor, and then the precursor and a sodium source are mixed and sintered to obtain. The above preparation method is controllable, and the obtained precursor is a compact sphere, so it has a high tap density. However, due to the need to adjust many parameters in the preparation process, and the solubility product constant of different metal ions has a large difference, it is difficult to synthesize uniform and stable layered transition metal compound sodium ion battery cathode materials.

[0004] In addition, in terms of raw material selection, on the one hand, metal oxides / hydroxides are not soluble in water, so they cannot be directly prepared by liquid phase method and need to be ground at high speed for a long time. On the other hand, some metal nitrates are dangerous (for example, nickel nitrate is listed in the "List of Easily Explosive Hazardous Chemicals") and expensive, so they are not suitable for large-scale production. Although metal chloride salts have good dispersibility, they have serious hydrolysis phenomenon, which can cause the salt solution to be strongly acidic, and the small radius of chloride ions can damage the passivation film on the surface of 304 stainless steel (a commonly used stainless steel material). In contrast, metal sulfate salts have weak corrosion to 304 stainless steel, but they are easy to absorb water, which leads to agglomeration between particles. At present, there are few studies on the preparation of layered sodium ion battery cathode materials using metal sulfate salts as raw materials.

[0005] Therefore, in the field, there is an urgent need to develop a method for preparing layered transition metal sodium ion battery cathode materials using metal sulfate salts as raw materials to solve the above problems. SUMMARY

[0006] In view of the deficiencies of the prior art, the present application aims to provide a single-crystal layered oxide positive electrode material, a preparation method thereof and a sodium-ion battery.

[0007] To achieve the above object, the present application adopts the following technical solutions:

[0008] In a first aspect, the present application provides a method for preparing a single-crystal layered oxide positive electrode material, comprising the following steps:

[0009] Preparation of a mixed metal sulfate solution containing different metal elements; spray drying the mixed metal sulfate solution to obtain a mixed metal sulfate powder;

[0010] First sintering treatment of the mixed metal sulfate powder to obtain a mixed metal oxide precursor;

[0011] Second sintering treatment of the mixed metal oxide precursor and a sodium source to obtain the single-crystal layered oxide positive electrode material.

[0012] Firstly, the present application uses an easily available sulfate solution containing different metal elements as raw material, which is because the corrosion of sulfate ions to stainless steel substrate is much lower than that of chloride ions, and it also has cost advantage; secondly, the present application uses a simple and fast spray drying technology to mix and granulate the mixed metal sulfate solution, so that the prepared mixed metal sulfate powder is uniform in composition, which is beneficial to form a micron-sized single crystal structure in the subsequent first sintering process; in addition, the single-crystal layered oxide positive electrode material prepared by the second sintering treatment eliminates the influence of the easy water absorption of sulfate and the agglomeration, and the single-crystal layered oxide positive electrode material has no grain boundary in the interior, so that its structural stability is higher than that of polycrystalline positive electrode material, and its discharge capacity is close to that of the positive electrode material prepared by using chloride as raw material.

[0013] Preferably, the chemical formula of the single-crystal layered oxide positive electrode material is Na a M x N 1-xO2, wherein M is any two or three of Ni, Fe or Mn in combination, N is any one or more of Li, Mg, Al, Si, K, Ca, Ti, V, Cr, Co, Cu, Zn, Sr, Y, Zr, Nb, Mo, Ru, In, Sn, Sb, W, Ta, Ba, Bi, La, Ce or Eu in combination; 0.7

[0014] Preferably, the concentration of the mixed metal sulfate solution is 1-4 mol / L, preferably 3 mol / L, for example 1, 1.2, 1.5, 1.8, 2, 2.2, 2.5, 2.8, 3, 3.2, 3.5, 3.8, 4 mol / L, etc.

[0015] Preferably, the inlet temperature of the spray drying is 180-220°C, preferably 200°C, for example 180, 185, 190, 195, 200, 205, 210, 215, 220°C, etc.

[0016] Preferably, the outlet temperature of the spray drying is 90-130°C, preferably 100°C, for example 90, 95, 100, 105, 110, 115, 120, 125, 130°C, etc.

[0017] In the present application, by regulating the inlet and outlet temperatures of the spray drying, the water in the solution can be rapidly vaporized and extracted, while the sulfate can form spherical particles with uniform composition.

[0018] Preferably, the particle size of the mixed metal sulfate powder is 0.5-3 μm, for example 0.5, 0.8, 1, 1.2, 1.5, 1.8, 2, 2.2, 2.5, 2.8, 3 μm, etc. By regulating the particle size of the mixed metal sulfate powder, the present application facilitates the formation of micron-level single crystal structure in the subsequent primary sintering process.

[0019] Preferably, the primary sintering process is carried out in an atmosphere containing oxygen.

[0020] Preferably, the temperature of the first sintering treatment is 700-1000℃, preferably 900℃; for example, it can be 700℃, 720℃, 750℃, 780℃, 800℃, 820℃, 850℃, 880℃, 900℃, 920℃, 950℃, 980℃, 1000℃, etc.

[0021] Preferably, the time of the first sintering treatment is 1-5h, preferably 2h; for example, it can be 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, etc. The present application can completely decompose the sulfate by regulating the process parameters of the first sintering treatment, so as to obtain a metal oxide precursor with low sulfur content.

[0022] Preferably, the second sintering treatment is carried out in an atmosphere containing oxygen.

[0023] Preferably, the temperature of the second sintering treatment is 800-1100℃, for example, it can be 800℃, 820℃, 850℃, 880℃, 900℃, 920℃, 950℃, 980℃, 1000℃, 1020℃, 1050℃, 1080℃, 1100℃, etc.; the time is 5-15h, for example, it can be 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, etc.

[0024] Preferably, the sodium source includes any one of sodium hydroxide, sodium carbonate, sodium formate or sodium acetate.

[0025] Preferably, the molar ratio of the sodium source to the mixed metal oxide precursor is (1.01-1.07):1, for example, it can be 1.01:1, 1.02:1, 1.03:1, 1.04:1, 1.05:1, 1.06:1, 1.07:1, etc.

[0026] In a second aspect, the present application provides a single-crystal layered oxide positive electrode material, which is prepared by the method for preparing a single-crystal layered oxide positive electrode material according to the first aspect.

[0027] Preferably, the particle size of the single-crystal layered oxide positive electrode material is 5-15μm, for example, it can be 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, etc.

[0028] The preparation method provided by the present application can prepare a single-crystal layered oxide sodium ion battery positive electrode material with large size, avoiding the influence of water absorption agglomeration between precursor raw material particles.

[0029] In a third aspect, the present application provides a sodium-ion battery, comprising a positive electrode, a negative electrode and an electrolyte, wherein the positive electrode comprises the single-crystal layered oxide positive electrode material according to the second aspect.

[0030] Compared with the prior art, the present application has the following beneficial effects:

[0031] The present application provides a method for preparing a single-crystal layered oxide positive electrode material. Firstly, the present application uses an easily obtained sulfate solution containing different metal elements as raw material, which has a cost advantage because sulfate ions have much lower corrosiveness to stainless steel substrates than chloride ions. Secondly, the present application uses a simple and fast spray drying technology to uniformly mix and granulate the mixed metal sulfate solution, so that the prepared mixed metal sulfate powder has uniform composition, which is beneficial to the formation of a micron-sized single-crystal structure in the subsequent primary sintering process. In addition, the single-crystal layered oxide positive electrode material prepared by the secondary sintering process eliminates the influence of the easy water absorption of the sulfate and the absence of grain boundaries in the single-crystal layered oxide positive electrode material, so that the structure stability is higher than that of the polycrystalline positive electrode material, and the discharge capacity is close to that of the positive electrode material prepared by using chloride as raw material. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 SEM characterization diagram of the mixed metal sulfate powder provided for Example 1;

[0033] Figure 2 SEM characterization diagram of the mixed metal oxide precursor provided for Example 1;

[0034] Figure 3 SEM characterization diagram of the single-crystal layered oxide positive electrode material provided for Example 1;

[0035] Figure 4 SEM characterization diagram of the mixed metal chloride salt powder provided for Comparative Example 1;

[0036] Figure 5 SEM characterization diagram of the mixed metal oxide precursor provided for Comparative Example 1;

[0037] Figure 6 SEM characterization diagram of the single-crystal layered oxide positive electrode material provided for Comparative Example 1.

[0038] Figure 7 XRD spectrum of the sample provided for Comparative Example 3. DETAILED DESCRIPTION

[0039] The technical solutions of the present application will be further illustrated below by combining with the drawings and specific embodiments. Those skilled in the art should understand that the embodiments are only used to help understand the present application, and should not be regarded as specific limitations of the present application.

[0040] Embodiment 1

[0041] The present embodiment provides a single-crystal layered oxide positive electrode material and a preparation method thereof, the preparation method comprising the following steps:

[0042] 0.6 mol of NiSO4, 1.05 mol of FeSO4, 1.05 mol of MnSO4 and 0.3 mol of CuSO4 were added into 1 L of water to obtain a mixed metal sulfate solution; the mixed metal sulfate solution was spray dried to obtain a mixed metal sulfate powder with a particle size of 1 μm, as shown in FIG. 1, denoted as NFMCSO4, wherein the inlet temperature was 200 ℃ and the outlet temperature was 100 ℃; Figure 1

[0043] The mixed metal sulfate powder was subjected to a first sintering treatment at 900 ℃ for 2 h in a compressed air atmosphere to obtain a mixed metal oxide precursor, as shown in FIG. 2, denoted as NFMCO-SO4; Figure 2

[0044] The mixed metal oxide precursor and sodium carbonate were subjected to a second sintering treatment at 900 ℃ for 8 h in a compressed air atmosphere, wherein the molar ratio of sodium carbonate to the mixed metal oxide precursor was 1.03:1, to obtain the single-crystal layered oxide positive electrode material, with a structural formula of Na 0.98 Ni 0.2 Fe 0.35 Mn 0.35 Cu 0.1 O2, denoted as NaNFMC-SO4.

[0045] The SEM image of the single-crystal layered oxide positive electrode material in the present embodiment is shown in FIG. 3, which is a single-crystal layered positive electrode material with a diameter of 10 μm. The content of each metal atom of the single-crystal layered oxide positive electrode material in the present embodiment was tested by inductively coupled plasma (ICP) technology, and the content of each metal atom was close to the feeding ratio, and the test results are shown in Table 1: Figure 3

[0046] Table 1

[0047]

[0048]

[0049] Embodiment 2

[0050] ​​​The embodiment provides a single-crystal layered oxide positive electrode material and a preparation method thereof.

[0051] 0.6 mol of NiSO4, 1.05 mol of FeSO4, 1.05 mol of MnSO4 and 0.3 mol of CuSO4 are added into 1L of water to obtain a mixed metal sulfate solution; the mixed metal sulfate solution is subjected to spray drying to obtain mixed metal sulfate powder with a particle size of 1 μm, wherein the temperature of an air inlet is 200 DEG C, and the temperature of an air outlet is 100 DEG C;

[0052] The mixed metal sulfate powder is subjected to primary sintering treatment at 850 DEG C for 2h in a compressed air atmosphere to obtain a mixed metal oxide precursor;

[0053] The mixed metal oxide precursor and sodium carbonate are subjected to secondary sintering treatment at 900 DEG C for 8h in a compressed air atmosphere, wherein the molar ratio of sodium carbonate to the mixed metal oxide precursor is 1.03:1, to obtain the single-crystal layered oxide positive electrode material.

[0054] Example 3

[0055] The embodiment provides a single-crystal layered oxide positive electrode material and a preparation method thereof, the preparation method comprising the following steps:

[0056] 0.6 mol of NiSO4, 1.05 mol of FeSO4, 1.05 mol of MnSO4 and 0.3 mol of CuSO4 are added into 1L of water to obtain a mixed metal sulfate solution; the mixed metal sulfate solution is subjected to spray drying to obtain mixed metal sulfate powder with a particle size of 1 μm, wherein the temperature of an air inlet is 200 DEG C, and the temperature of an air outlet is 100 DEG C;

[0057] The mixed metal sulfate powder is subjected to primary sintering treatment at 950 DEG C for 2h in a compressed air atmosphere to obtain a mixed metal oxide precursor;

[0058] The mixed metal oxide precursor and sodium carbonate are subjected to secondary sintering treatment at 900 DEG C for 8h in a compressed air atmosphere, wherein the molar ratio of sodium carbonate to the mixed metal oxide precursor is 1.03:1, to obtain the single-crystal layered oxide positive electrode material.

[0059] Example 4

[0060] The embodiment provides a single-crystal layered oxide positive electrode material and a preparation method thereof, the preparation method comprising the following steps:

[0061] A mixed metal sulfate solution was prepared by adding 0.6 mol of NiSO4, 1.05 mol of FeSO4, 1.05 mol of MnSO4 and 0.3 mol of CuSO4 into 1 L of water; the mixed metal sulfate solution was spray dried to obtain a mixed metal sulfate powder with a particle size of 0.5 μm, wherein the inlet temperature was 180 °C and the outlet temperature was 90 °C;

[0062] The mixed metal oxide precursor was obtained by sintering the mixed metal sulfate powder at 700 °C for 5 h in a compressed air atmosphere;

[0063] The single-crystal layered oxide positive electrode material was obtained by sintering the mixed metal oxide precursor and sodium carbonate at 800 °C for 8 h in a compressed air atmosphere, wherein the molar ratio of sodium carbonate to the mixed metal oxide precursor was 1.03:1.

[0064] Example 5

[0065] The present example provides a single-crystal layered oxide positive electrode material and a preparation method thereof, the preparation method comprising the following steps:

[0066] A mixed metal sulfate solution was prepared by adding 0.6 mol of NiSO4, 1.05 mol of FeSO4, 1.05 mol of MnSO4 and 0.3 mol of CuSO4 into 1 L of water; the mixed metal sulfate solution was spray dried to obtain a mixed metal sulfate powder with a particle size of 3 μm, wherein the inlet temperature was 220 °C and the outlet temperature was 130 °C;

[0067] The mixed metal oxide precursor was obtained by sintering the mixed metal sulfate powder at 1000 °C for 1 h in a compressed air atmosphere;

[0068] The single-crystal layered oxide positive electrode material was obtained by sintering the mixed metal oxide precursor and sodium carbonate at 1100 °C for 8 h in a compressed air atmosphere, wherein the molar ratio of sodium carbonate to the mixed metal oxide precursor was 1.03:1.

[0069] Example 6

[0070] The present example differs from Example 1 in that the inlet temperature of the spray drying was 150 °C and the outlet temperature was 50 °C, and the other conditions were the same as in Example 1.

[0071] Example 7

[0072] The present example differs from Example 1 in that the inlet temperature of the spray drying was 250 °C and the outlet temperature was 150 °C, and the other conditions were the same as in Example 1.

[0073] Example 8

[0074] This example is different from Example 1 in that the mixed metal sulfate powder is sintered at 500°C for 3h in a compressed air atmosphere to obtain a mixed metal oxide precursor, and the rest is the same as Example 1.

[0075] Comparative Example 1

[0076] This comparative example provides a single-crystal layered oxide positive electrode material, and the preparation method is as follows:

[0077] 0.6 mol of NiCl2, 1.05 mol of FeCl2, 1.05 mol of MnCl2, and 0.3 mol of CuCl2 are added to 1 L of water to obtain a mixed metal chloride salt solution; the mixed metal chloride salt solution is spray dried to obtain a mixed metal chloride salt powder with a particle size of 1 μm, as shown in FIG. 1, denoted as NFMCCl2, wherein the inlet temperature is 200°C and the outlet temperature is 100°C; Figure 4

[0078] The mixed metal chloride salt powder is sintered at 900°C for 2h in a compressed air atmosphere to obtain a mixed metal oxide precursor, as shown in FIG. 2, denoted as NFMCO-Cl2; Figure 5

[0079] The mixed metal oxide precursor and sodium carbonate are sintered at 900°C for 8h in a compressed air atmosphere, wherein the molar ratio of sodium carbonate to mixed metal oxide precursor is 1.03:1, to obtain the single-crystal layered oxide positive electrode material, denoted as NaNFMC-Cl2.

[0080] The SEM image of the single-crystal layered oxide positive electrode material in this comparative example is shown in FIG. 3, which is an oxide positive electrode material with a diameter of 10 μm. The content of each metal atom in the single-crystal layered oxide positive electrode material in this comparative example is tested using inductively coupled plasma (ICP) technology, wherein the proportion of copper ions is significantly lower than the feeding ratio, indicating that there is a loss of copper during the spray drying process. The test results are shown in Table 2: Figure 6

[0081] Table 2

[0082] Metal content / at% Ni Fe Mn Cu [NF2CCl2] 19.7 37.0 34.9 8.4 [NFMCO-Cl2] 19.9 36.1 35.5 8.5 NaNFMC-Cl2 19.7 36.8 35.1 8.4

[0083] Comparative Example 2

[0084] This comparative example provides an oxide positive electrode material, and the preparation method is as follows:

[0085] ​​​A mixed metal sulfate solution was prepared by adding 0.6 mol of NiSO4, 1.05 mol of FeSO4, 1.05 mol of MnSO4 and 0.3 mol of CuSO4 into 1 L of water; a 20 L reactor was charged with 12 L of pure water, the temperature was controlled at 58°C, the stirring speed was controlled at 380 rpm, the pH value was adjusted to 11.30 by passing in sodium hydroxide solution, and nitrogen was continuously passed into the reactor to obtain a bottom solution; the mixed metal sulfate solution, sodium hydroxide solution, acetylacetone and citric acid mixture were co-precipitated in the bottom solution. The pH value of the solution and the particle size of the precipitated particles were measured at least once an hour during the reaction, and the morphology of the particles was observed, and the flow rates of the metal sulfate solution, sodium hydroxide solution, acetylacetone and citric acid mixture were adjusted according to the results. When the particle size of the precipitated particles was 6 μm, the reaction was stopped and washing and filtration were carried out, and after drying treatment, a mixed metal oxide precursor was obtained;

[0086] The mixed metal oxide precursor and sodium carbonate were sintered at 900°C for 8 h in a compressed air atmosphere, and the molar ratio of sodium carbonate to mixed metal oxide precursor was 1.03:1, to obtain the oxide positive electrode material.

[0087] Comparative Example 3

[0088] The present comparative example provides a material and a preparation method thereof, which comprises the following steps:

[0089] A mixed metal sulfate solution was prepared by adding 0.6 mol of NiSO4, 1.05 mol of FeSO4, 1.05 mol of MnSO4 and 0.3 mol of CuSO4 into 1 L of water; the mixed metal sulfate solution was spray dried to obtain a mixed metal sulfate powder with a particle size of 1 μm, wherein the inlet temperature was 200°C and the outlet temperature was 100°C;

[0090] The mixed metal sulfate powder and sodium carbonate were sintered at 900°C for 10 h in a compressed air atmosphere, and the molar ratio of sodium carbonate to mixed metal sulfate powder was 1.03:1, and the obtained solid was in the form of a hard block, and the XRD spectrum result showed that it was composed of metal oxides and sodium sulfate (as shown in Figure 7 This is because sodium ions recombine with sulfates, and sodium sulfate is difficult to decompose at 900°C, so this method cannot obtain the final oxide positive electrode material.

[0091] Test conditions

[0092] The layered oxide positive electrode materials provided by Examples 1 to 8 and Comparative Examples 1 to 3 were tested, and the test method was as follows:

[0093] The layered oxide positive electrode material provided by Examples 1 to 8 and Comparative Examples 1 to 3, the conductive agent Super P, the polyvinylidene fluoride and the N-methylpyrrolidone were mixed to prepare a positive electrode slurry, which was blade-coated on the surface of an aluminum foil, and after drying, rolling and slicing, a positive electrode sheet was obtained;

[0094] The positive electrode sheet, a polypropylene separator, a lithium sheet and an electrolyte were assembled into a 2032 type button cell, wherein the electrolyte composition was a mixed solvent of sodium hexafluorophosphate with a concentration of 1 mol / L and dimethyl carbonate (DMC), ethylene carbonate (EC) and methyl ethyl carbonate (EMC) with a volume ratio of 1:1:1, and 1% by mass of VC was added.

[0095] The above button cell was placed in a blue power test system, and a current density of 0.1C (1C = 240 mA / g) was used for charge and discharge cycle test.

[0096] The test results are shown in Table 3:

[0097] Table 3

[0098]

[0099] Note: In the table, " / " indicates that due to the inability to prepare the oxide positive electrode material, performance testing cannot be performed.

[0100] As can be seen from Table 1, by comparing Example 1 with Comparative Example 1, it can be seen that the present application uses a mixed metal sulfate solution with less corrosion as raw material for spray drying pretreatment, so that the mixed metal sulfate powder prepared is uniform in composition, thereby facilitating the formation of a micron-sized single crystal structure in the subsequent one-time sintering process; and then using two sintering processes to prepare a large-size single crystal layered oxide sodium-ion battery positive electrode material, which eliminates the influence of the easy water absorption of the sulfate and the agglomeration thereof, and the single crystal layered oxide positive electrode material has no grain boundaries in the interior, so that its structural stability is higher than that of a polycrystalline positive electrode material, and its discharge capacity is close to that of a positive electrode material prepared from a chloride as a raw material.

[0101] Compared with Example 1, Examples 6-7 show that by adjusting the inlet air temperature and the outlet air temperature of the spray drying, the water in the solution can be rapidly vaporized and extracted, and the sulfate can form spherical particles with uniform composition.

[0102] Compared with Example 1, Example 8 shows that if the temperature of the one-time sintering process is lower, a large amount of sulfate will be left, which is difficult to decompose subsequently.

[0103] From Comparative Example 1, Comparative Example 2 and Comparative Example 3, it can be seen that the co-precipitation method and the sintering method used in the prior art have complex operation, more parameters to be controlled, and large difference in solubility product constant of different metal ions, so a suitable complexing agent and a precipitant need to be selected, and thus the preparation is difficult. Comparative Example 3 further shows that if the mixed metal sulfate powder and sodium carbonate are directly sintered, the mixed metal sulfate cannot be completely converted into oxide, and sodium sulfate is difficult to decompose at 900℃, so the final oxide cathode material cannot be obtained by this method.

[0104] The applicant declares that the process of the present application is illustrated by the above examples, but the present application is not limited to the above process steps, that is, it does not mean that the present application must rely on the above process steps to be implemented. It should be understood by those skilled in the art that any improvement of the present application, equivalent replacement of the raw materials selected by the present application, addition of auxiliary ingredients, selection of specific methods, etc. fall within the protection scope and disclosure scope of the present application.

Claims

1. A method for preparing a single-crystal layered oxide cathode material, characterized in that, The method includes the following steps: Prepare a mixed metal sulfate solution containing different metal elements; spray dry the mixed metal sulfate solution to obtain mixed metal sulfate powder; The inlet temperature of the spray dryer is 180℃~220℃; The outlet temperature of the spray dryer is 90℃~130℃; the mixed metal sulfate powder is subjected to a single sintering treatment to obtain a mixed metal oxide precursor; The temperature of the first sintering process is 700℃~1000℃; The primary sintering process is carried out in an oxygen-containing atmosphere; The duration of the first sintering process is 1 hour to 5 hours. The mixed metal oxide precursor and sodium source are subjected to a secondary sintering process to obtain the single-crystal layered oxide cathode material. The secondary sintering process is carried out in an oxygen-containing atmosphere; The secondary sintering treatment is performed at a temperature of 800℃~1100℃ for 5h~15h. The sodium source includes any one of sodium hydroxide, sodium carbonate, sodium formate, or sodium acetate; The molar ratio of the sodium source to the mixed metal oxide precursor is (1.01~1.07):

1.

2. The method according to claim 1, characterized in that, The chemical formula of the single-crystal layered oxide cathode material is Na. a M x N 1-x O2, where M is any combination of two or three of Ni, Fe or Mn, and N is any combination of one or more of Li, Mg, Al, Si, K, Ca, Ti, V, Cr, Co, Cu, Zn, Sr, Y, Zr, Nb, Mo, Ru, In, Sn, Sb, W, Ta, Ba, Bi, La, Ce or Eu; 0.7 < a ≤ 1.2, 0.8 ≤ x ≤ 1.

3. The method according to claim 1, characterized in that, The concentration of the mixed metal sulfate solution is 1 mol / L to 4 mol / L.

4. The method according to claim 3, characterized in that, The concentration of the mixed metal sulfate solution is 3 mol / L.

5. The method according to claim 1, characterized in that, The air inlet temperature of the spray dryer is 200°C.

6. The method according to claim 1, characterized in that, The outlet temperature of the spray dryer is 100°C.

7. The method according to claim 1, characterized in that, The particle size of the mixed metal sulfate powder is 0.5μm~3μm.

8. The method according to claim 1, characterized in that, The temperature of the first sintering process is 900℃.

9. The method according to claim 1, characterized in that, The sintering process takes 2 hours.

10. A single-crystal layered oxide cathode material, wherein the single-crystal layered oxide cathode material is prepared by the method for preparing a single-crystal layered oxide cathode material according to any one of claims 1-9.

11. The single-crystal layered oxide cathode material according to claim 10, characterized in that, The particle size of the single-crystal layered oxide cathode material is 5μm~15μm.

12. A sodium-ion battery, characterized in that, The sodium-ion battery includes a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode includes a single-crystal layered oxide positive electrode material according to claim 10 or 11.

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