Layered oxide positive electrode material of sodium ion battery, preparation method and positive electrode plate

Abstract

The invention provides a sodium ion battery layered oxide positive electrode material, a preparation method and a positive electrode plate, and belongs to the technical field of sodium ion battery positive electrode materials. The invention relates to a preparation method of a layered oxide positive electrode material of a sodium ion battery. The preparation method comprises the following steps: 1, providing a sodium source and a metal source; step 2, dissolving inorganic salt or organic salt of a metal source and a sodium source in a mixed solvent of ethylene glycol and ethanol according to a stoichiometric ratio to obtain a mixed solution; step 3, stirring the mixed solution at 50-90 DEG C, carrying out heat preservation for more than 5 hours, and carrying out chelation reaction; and 4, after the reaction is completed, transferring the mixed solution into an alumina crucible, and combusting with open fire until the mixed solution completely forms a powdery material, thereby obtaining the layered oxide positive electrode material of the sodium-ion battery. The preparation method is used for simplifying the process and improving the cycling stability of the sodium ion battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of sodium ion battery positive electrode materials, and in particular relates to a sodium ion battery layered oxide positive electrode material, a preparation method and a positive electrode sheet. Background Art

[0002] With the rapid development of renewable energy and smart grids, the demand for low-cost, long-life batteries for large-scale energy storage systems is becoming increasingly urgent. Sodium-ion batteries, due to their abundant resources and low cost, show great potential for application in large-scale energy storage. Layered transition metal oxides, as one of the core cathode materials for sodium-ion batteries, have attracted considerable attention due to their excellent electrochemical performance and structural stability.

[0003] However, the larger ionic radius of sodium ions (~1.02Å) is significantly different from that of lithium ions (~0.76Å), which brings different challenges to sodium ion layered cathode materials: the lattice volume change caused by sodium ions during interlayer deintercalation is usually larger than that of lithium ions, making the material more susceptible to harmful phase changes and structural distortions during cycling; the radius difference between sodium ions and transition metal ions is relatively small, which makes it easier for sodium ions in the sodium layer and transition metal ions in the transition metal layer to mix. This mixing will hinder the sodium ion diffusion channel, increase internal resistance, and seriously damage the material's rate performance and cycle stability; the above-mentioned structural instability and mixing problems, coupled with repeated lattice expansion / contraction stress during charge and discharge, can easily lead to cracking of material particles, peeling of active materials, and intensified interfacial side reactions, ultimately manifesting as rapid capacity decay and a shorter cycle life.

[0004] In order to improve the cycle stability of layered cathode materials for sodium ion batteries, researchers have conducted many explorations in order to solve the above problems. For example, patent application document CN116031396A discloses a method for preparing cathode materials for sodium ion batteries, comprising the following steps: (1) mixing NiO, MnO2, A oxide and sodium salt in water to form a mixed solution, and then sand-milling the mixed solution to obtain a slurry; (2) spray-drying the slurry to obtain a precursor powder; (3) sintering the precursor powder for the first time at a sintering temperature of 600-950°C, and then rapidly cooling the mixture to room temperature at a cooling rate of ≥20°C / min after sintering, and crushing the material to obtain a mixture A; (4) mixing the mixture A with B oxide or B hydroxide, and sintering the mixture for the second time (500-850°C for 5-10 hours), crushing, and sieving to obtain a cathode material. A double sintering + rapid cooling process is used to introduce inert elements to pin phase change cracks through defect engineering. Although this method improves the cycle performance, the preparation process is complicated, energy consumption is high, and the industrialization cost increases dramatically.

[0005] For example, patent application document CN118213653A discloses a method for preparing a sodium ion layered positive electrode material, comprising the following steps: (1) providing a layer containing Li + 、H + 、F - (1) preparing a sodium-ion battery cell recovery solution; preparing a sodium source and the lithium-ion battery cell recovery solution into a solution; (2) mixing a sodium-ion layered cathode material into the solution to prepare a mixed slurry; (3) filtering and drying the mixed slurry to obtain a precursor powder; (4) sintering the precursor powder, wherein the sintering comprises: heating to 200°C to 400°C, performing a first stage of heat preservation, then heating to 600°C to 900°C, performing a second stage of heat preservation, and then cooling the furnace to obtain a sodium-ion layered cathode material. Although this method reduces residual alkali and improves interface stability, Li + / F - The introduction of may disrupt the sodium layer transmission dynamics, and the volatility of the recovered liquid composition makes it difficult to ensure the consistency of material batches.

[0006] In view of this, it is necessary to develop a layered oxide positive electrode material for sodium ion batteries with a simpler preparation process, controllable energy consumption and improved cycle stability of sodium ion batteries. Summary of the Invention

[0007] In view of the shortcomings of the existing technology, the technical problem to be solved by the present invention is to provide a method for preparing a layered oxide positive electrode material for a sodium ion battery to simplify the process and improve the cycle stability of the sodium ion battery.

[0008] To solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing a layered oxide positive electrode material for a sodium ion battery, comprising the following steps: Step 1: providing a sodium source and a metal source; Step 2: dissolving an inorganic salt or organic salt of a metal source and a sodium source in a mixed solvent of ethylene glycol and ethanol in a stoichiometric ratio to obtain a mixed solution; Step 3: Stir the mixed solution at 50-90°C for more than 5 hours to carry out the chelation reaction; Step 4: After the reaction is complete, the mixed solution is transferred to an alumina crucible and burned with an open flame until the mixed solution is completely formed into a powdery material to obtain a sodium ion battery layered oxide positive electrode material.

[0009] This invention uses a mixed solvent of ethylene glycol and ethanol, combining low-temperature chelation with open flame sintering. Stirring is performed at 50-90°C for at least 5 hours. The ethylene glycol chelates the metal ions to form a uniform precursor, saving energy and preventing sodium salt decomposition. The high temperature (800-1000°C) generated by the open flame prevents excessive grain growth and reduces internal cracking. This overall solution simplifies the process and improves the cycling stability of sodium-ion batteries.

[0010] Optionally, the sodium source is a mixture of one or more of sodium chloride, sodium nitrate, sodium acetate, sodium citrate and sodium malate; The metal source is a mixture of one or more of magnesium, iron, titanium, copper, manganese, vanadium, chromium, nickel, cobalt, zinc, aluminum, zirconium and niobium; The inorganic salt or organic salt of the metal source is a mixture of one or more of chloride, acetate, nitrate, iodide, citrate, malate, tartrate, benzoate and metal ester of the metal source.

[0011] Furthermore, the metal ester may be selected from n-butyl titanate and / or n-butyl zirconate, but is not limited thereto.

[0012] Optionally, in the mixed solvent of ethylene glycol and ethanol, the volume ratio of ethylene glycol to ethanol is 1:(1-5).

[0013] Based on the above technical solution, the polarity of the solvent can be optimized and the chelation efficiency can be improved, wherein: ethylene glycol chelates metal ions and prevents the metal ions from reacting with OH. - Combine to form hydroxide precipitate; ethanol adjusts viscosity, improves fluidity, prevents local supersaturation crystallization, and avoids precipitation.

[0014] Optionally, the total concentration of metal ions and sodium ions in the mixed solution is 0.02-2 mol / L.

[0015] In the present invention, it is critical to control the total concentration of metal ions and sodium ions in the mixed solution. Too low a concentration will lead to insufficient chelation, while too high a concentration will easily cause component segregation. After experimental optimization and verification, when the total concentration of metal ions and sodium ions in the mixed solution is 0.02-2 mol / L, the structural stability of the layered oxide positive electrode material of the sodium ion battery is better, and the cycle stability of the sodium ion battery is more significant.

[0016] Optionally, the process parameters of the low-temperature heating and heat preservation treatment include: heat preservation at 50-90°C for 5-12 hours.

[0017] Optionally, the open flame sintering is to burn the mixed solution with an open flame, and the center temperature of the flame reaches 800-1000°C.

[0018] Based on the above technical solution, the high temperature generated by open flame combustion causes organic matter (including residual ethanol, ethylene glycol, organic salt chelates, etc.) to decompose rapidly, forming a reducing atmosphere, inhibiting the formation of high-valent oxides, reducing surface residual alkali, and the Na2CO3 content is <0.1%.

[0019] The present invention also provides a sodium ion battery layered oxide positive electrode material, which is obtained according to the above preparation method.

[0020] The present invention also provides a positive electrode plate, comprising the above-mentioned sodium ion battery layered oxide positive electrode material.

[0021] Compared with the prior art, the present invention has the following beneficial effects: The present invention utilizes inorganic salts or organic salts of metal sources to directly mix with sodium sources in a stoichiometric ratio, and dissolves them in a mixed solvent of ethylene glycol and ethanol to form a mixed solution, omitting the grinding / ball milling and / or calcination steps of synthesizing precursors in existing methods. No complicated pre-treatment process is required, which greatly simplifies the operation process, reduces the complexity of the process, makes the production process more efficient and convenient, greatly shortens the preparation cycle, improves production efficiency, and facilitates industrial production. Next, the mixed solution of the present invention is subjected to a low-temperature heating and heat preservation treatment of 50-90°C for more than 5 hours, and ethylene glycol chelates the metal ions to form a uniform precursor, which is then placed in an alumina crucible for open flame sintering. During the rapid sintering process, the high temperature (800-1000°C) provides energy to rearrange the surface atoms, forming a dense surface structure. The dense layer can block the contact between the electrolyte (such as NaPF6 / EC-DMC) and the internal active material, reduce side reactions, and at the same time, the volume change during charge and discharge (Na + The stress generated by embedding and de-embedding can be dispersed by the dense layer to avoid crack initiation. The amorphous structure in the dense layer provides a fast ion channel to reduce Na + Diffusion activation energy; the metal salt and sodium source fully react in this specific system, forming a cathode material with a micro-nano hierarchical layered structure, high crystallinity, and excellent thermal stability. This stable structure effectively inhibits the material's volume expansion and structural collapse during the battery's charge and discharge processes, reducing stress accumulation within the crystals and the risk of lattice dislocation and slip, thereby extending the battery's lifespan and improving its cycling stability.

[0022] In particular, the present invention avoids the use of toxic or hazardous chemicals throughout the sintering process, and produces no environmentally harmful waste gas, wastewater, or waste residue, making it environmentally friendly. Compared to traditional sintering methods, which can pose issues such as heavy metal pollution and acid-base corrosion, the present invention is particularly environmentally friendly, meeting the requirements of green chemistry. This contributes to the sustainable development of sodium-ion battery cathode materials, reduces the impact on the ecological environment, and contributes to the realization of clean energy and sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 : Sodium ion battery layered cathode material NaMg prepared in Example 1 0.05 Cu 0.05 Fe 0.40 Mn 0.40 Ti 0.10 X-ray diffraction pattern of O2; Figure 2 : The sodium ion battery layered cathode material NaMg prepared in Example 1 0.05 Cu 0.05 Fe 0.40 Mn 0.40 Ti 0.10 SEM image of O2. DETAILED DESCRIPTION

[0025] In order to better understand the present invention, the content of the present invention is further clearly set forth below in conjunction with the examples, but the protection content of the present invention is not limited to the following examples. In the following description, a large number of specific details are provided in order to provide a more thorough understanding of the present invention. However, it is obvious to those skilled in the art that the present invention can be implemented without one or more of these details.

[0026] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0027] Unless otherwise specified, all raw materials are derived from commercially available products and do not contain other unspecified components except inevitable impurities.

[0028] The preparation method of the present invention is described in detail below by taking sodium ion positive electrode material as an example. In the following description, normal temperature means that the ambient temperature is 25±5°C.

[0029] Example 1: NaMg 0.05 Cu 0.05 Fe 0.40 Mn 0.40 Ti 0.10 Take O2 as an example The preparation method of the layered positive electrode material for sodium ion batteries is specifically implemented as follows: Step 1: providing sodium acetate, manganese acetate, iron nitrate, magnesium nitrate, copper nitrate and tetrabutyl titanate; Step 2: Weigh the above raw materials in a stoichiometric ratio and dissolve them in a mixed solvent of ethylene glycol and ethanol in a volume ratio of 1:2 to form a mixed solution with a total concentration of sodium ions, manganese ions, iron ions, magnesium ions, copper ions, and titanium ions of 0.1 mol / L; Step 3: Stir the mixed solution at 80°C and keep the mixture for 8 hours; Step 4: Transfer the mixed solution to an alumina crucible and ignite it at room temperature. Burn the mixed solution with an open flame until the center temperature of the flame reaches 832°C until the mixed solution is completely formed into a powdery material to obtain the sodium ion battery layered positive electrode material NaMg 0.05 Cu 0.05 Fe 0.40 Mn 0.40 Ti 0.10 O2.

[0030] X-ray diffractometer was used to analyze the NaMg 0.05 Cu 0.05 Fe 0.40 Mn 0.40 Ti 0.10 The structure of O2 material is characterized and analyzed to obtain X-ray diffraction pattern. Figure 1 As shown, XRD analysis results show that NaMg 0.05 Cu 0.05 Fe 0.40 Mn 0.40 Ti 0.10 The diffraction peaks of O2 material show similarities to those of α-NaFeO2 ( The hexagonal lattice structure of the material is an O3 layered structure.

[0031] Scanning electron microscopy was used to analyze the NaMg 0.05 Cu 0.05 Fe 0.40 Mn 0.40 Ti 0.10 O2 material was tested and SEM photos were obtained. Figure 2 As mentioned above, NaMg 0.05 Cu 0.05 Fe 0.40 Mn 0.40 Ti 0.10 The O2 material is micron-sized particles composed of nano-scale flakes, with a size of less than 3 microns.

[0032] Example 2: Na 2 / 3 Mg 1 / 6 Ni 1 / 6 Mn 2 / 3 Take O2 as an example The preparation method of the layered positive electrode material for sodium ion batteries is specifically implemented as follows: Step 1: providing disodium malate, magnesium acetate, nickel nitrate, and manganese acetate; Step 2: Weigh the above raw materials in a stoichiometric ratio and dissolve them in a mixed solvent of ethylene glycol and ethanol in a volume ratio of 1:3 to form a mixed solution with a total concentration of sodium ions, magnesium ions, nickel ions, and manganese ions of 0.05 mol / L; Step 3: Stir the mixed solution at 70°C and keep the mixture for 10 hours; Step 4: Transfer the mixed solution to an alumina crucible and ignite it at room temperature. Burn the mixed solution with an open flame until the center temperature of the flame reaches 903°C until the mixed solution is completely formed into a powdery material to obtain the sodium ion battery layered positive electrode material Na 2 / 3 Mg 1 / 6 Ni 1 / 6 Mn 2 / 3 O2.

[0033] Example 3: NaCu 0.1 Fe 0.4 Mn 0.5 Take O2 as an example The preparation method of the layered positive electrode material for sodium ion batteries is specifically implemented as follows: Step 1: providing sodium citrate, copper chloride, ferric nitrate, and manganese acetate; Step 2: Weigh the above raw materials in a stoichiometric ratio and dissolve them in a mixed solvent of ethylene glycol and ethanol in a volume ratio of 1:5 to form a mixed solution with a total concentration of sodium ions, copper ions, iron ions, and manganese ions of 0.02 mol / L; Step 3: Stir the mixed solution at 60°C and keep the mixture for 12 hours; Step 4: Transfer the mixed solution to an alumina crucible and ignite it at room temperature. Burn the mixed solution with an open flame until the center temperature of the flame reaches 875°C until the mixed solution is completely formed into a powdery material to obtain the sodium ion battery layered positive electrode material NaCu 0.1 Fe 0.4 Mn 0.5 O2.

[0034] Example 4: Na 2 / 3 Ni 1 / 3 Mn 2 / 3 Take O2 as an example The preparation method of the layered positive electrode material for sodium ion batteries is specifically implemented as follows: Step 1: providing disodium malate, nickel nitrate, and manganese acetate; Step 2: Weigh the above raw materials in a stoichiometric ratio and dissolve them in a mixed solvent of ethylene glycol and ethanol in a volume ratio of 1:1 to form a mixed solution with a total concentration of sodium ions, nickel ions, and manganese ions of 0.1 mol / L; Step 3: Stir the mixed solution at 75°C and keep the mixture for 11 hours; Step 4: Transfer the mixed solution to an alumina crucible and ignite it at room temperature. Burn the mixed solution with an open flame until the center temperature of the flame reaches 927°C until the mixed solution is completely formed into a powdery material to obtain the sodium ion battery layered positive electrode material Na 2 / 3 Ni 1 / 3 Mn 2 / 3 O2.

[0035] Example 5: Na 2 / 3 Fe 1 / 2 Mn 1 / 2 Take O2 as an example The preparation method of the layered positive electrode material for sodium ion batteries is specifically implemented as follows: Step 1: providing sodium acetate, ferrous chloride, and manganese chloride; Step 2: Weigh the above raw materials according to the stoichiometric ratio and dissolve them in a mixed solvent of ethylene glycol and ethanol in a volume ratio of 1:4 to form a mixed solution with a total concentration of sodium ions, iron ions and manganese ions of 0.5 mol / L; Step 3: Stir the mixed solution at 50°C and keep the mixture for 12 hours; Step 4: Transfer the mixed solution to an alumina crucible and ignite it at room temperature. Burn the mixed solution with an open flame until the center temperature of the flame reaches 850°C until the mixed solution is completely formed into a powdery material to obtain the sodium ion battery layered positive electrode material Na 2 / 3 Fe 1 / 2 Mn 1 / 2 O2.

[0036] Example 6: NaZn 0.1 Co 0.1 Ni 0.30 Mn 0.40 Zr 0.10 Take O2 as an example The preparation method of the layered positive electrode material for sodium ion batteries is specifically implemented as follows: Step 1: providing sodium nitrate, zinc iodide, cobalt acetate, nickel chloride, manganese acetate, and n-butyl zirconate; Step 2: Weigh the above raw materials in a stoichiometric ratio and dissolve them in a mixed solvent of ethylene glycol and ethanol in a volume ratio of 1:3 to form a mixed solution with a total concentration of sodium ions, zinc ions, cobalt ions, nickel ions, manganese ions, and zirconium ions of 2 mol / L; Step 3: Stir the mixed solution at 70°C and keep the mixture for 10 hours; Step 4: Transfer the mixed solution to an alumina crucible and ignite it at room temperature. Burn the mixed solution with an open flame until the center temperature of the flame reaches 950°C until the mixed solution is completely formed into a powdery material to obtain the sodium ion battery layered positive electrode material NaZn 0.1 Co 0.1 Ni 0.30 Mn 0.40 Zr 0.10 O2.

[0037] Example 7: Na 0.67 V 0.02 Fe 0.4 Cr 0.08 Mn 0.4 Nb 0.1 Take O2 as an example The preparation method of the layered positive electrode material for sodium ion batteries is specifically implemented as follows: Step 1: providing sodium chloride, vanadium chloride, iron benzoate, chromium nitrate, manganese acetate, and niobium chloride; Step 2: Weigh the above raw materials in a stoichiometric ratio and dissolve them in a mixed solvent of ethylene glycol and ethanol in a volume ratio of 1:5 to form a mixed solution with a total concentration of sodium ions, vanadium ions, iron ions, chromium ions, manganese ions, and niobium ions of 1 mol / L; Step 3: Stir the mixed solution at 90°C and keep the mixture for 5 hours; Step 4: Transfer the mixed solution to an alumina crucible and ignite it at room temperature. Burn the mixed solution with an open flame until the center temperature of the flame reaches 935°C until the mixed solution is completely formed into a powdery material to obtain the sodium ion battery layered positive electrode material Na 0.67 V 0.02 Fe 0.4 Cr 0.08 Mn 0.4 Nb 0.1 O2.

[0038] Example 8: Na 2 / 3 Ni 1 / 4 Al 1 / 6 Mn 7 / 12 Take O2 as an example The preparation method of the layered positive electrode material for sodium ion batteries is specifically implemented as follows: Step 1: providing sodium nitrate, nickel acetate, aluminum nitrate, and manganese acetate; Step 2: Weigh the above raw materials in a stoichiometric ratio and dissolve them in a mixed solvent of ethylene glycol and ethanol in a volume ratio of 1:2 to form a mixed solution with a total concentration of sodium ions, nickel ions, aluminum ions, and manganese ions of 0.3 mol / L; Step 3: Stir the mixed solution at 65°C and keep the mixture for 11 hours; Step 4: Transfer the mixed solution to an alumina crucible and ignite it at room temperature. Burn the mixed solution with an open flame until the center temperature of the flame reaches 869°C until the mixed solution is completely formed into a powdery material to obtain the sodium ion battery layered positive electrode material Na 2 / 3 Ni 1 / 4 Al 1 / 6 Mn 7 / 12 O2.

[0039] The following are comparative examples.

[0040] Comparative Example 1: The difference from Example 1 is that the volume ratio of ethylene glycol to ethanol in the mixed solvent in step 2 is 1:8.

[0041] Comparative Example 2: The difference from Example 1 is that the mixed solvent in step 2 is replaced by ethylene glycol.

[0042] Comparative Example 3: The difference from Example 1 is that: Step 3 adopts stirring at 40°C and keeping warm for 16 hours.

[0043] Comparative Example 4: The difference from Example 1 is that: Step 3 adopts stirring at 100°C and keeping warm for 3 hours.

[0044] Comparative Example 5: The difference from Example 1 is that: the mixed solvent in step 2 is replaced by ethanol, and steps 3 and 4 are replaced by the following scheme, specifically: the mixed solution is placed in an alumina crucible, the alumina crucible is placed in a box furnace preheated to 500°C, ignited, and reacted vigorously in the air for 10 minutes. The product is cooled to room temperature of 25°C to obtain a preliminary product, the preliminary product is ground and placed in the box furnace again, annealed at a high temperature of 800°C for 16 hours, and then cooled to room temperature of 25°C with the furnace to obtain a sodium ion battery positive electrode material.

[0045] Next, the contents of the evaluation test will be described.

[0046] Preparation of sodium-ion battery positive electrode sheets and button cells: Sodium-ion battery positive electrode materials, conductive carbon black, and polyvinylidene fluoride were weighed in a mass ratio of 80:10:10. An appropriate amount of N-methylpyrrolidone solvent was added and ground into a slurry. The slurry was coated onto a current collector aluminum foil, vacuum-dried at 120°C for 10 hours, and then punched into positive electrode discs with a diameter of 12 mm. A sodium metal sheet was used as the negative electrode. A glass fiber membrane was used as the separator. A 1M NaPF₆ solution in EC:DEC (volume ratio 1:1) was used as the electrolyte. Finally, CR2032 button cells were assembled in an argon-filled dry glove box.

[0047] Battery Performance Test Method: Button cells were tested at room temperature using a LANDCT-2001A battery test system with a charge and discharge voltage range of 2.0-4.2V. At 25°C, they were charged at a constant current of 0.1C to 4.2V, then charged at a constant voltage to a cutoff current of 0.05C, and finally discharged at a constant current of 0.1C to 2.0V.

[0048] The sodium ion battery positive electrode materials prepared in Example 1 and Comparative Examples 1-5 were made into CR2032 button batteries according to the above method, marked as BC1, BC2, BC3, BC4, BC5 and BC6 in sequence, and then the cycle stability was tested according to the above test method.

[0049] The test results are shown in Table 1 below.

[0050] Table 1 Performance test results According to the test result of Comparative Example 1, it can be concluded that the proportion of ethylene glycol in the mixed solvent is reduced, and the capacity retention rate of the battery is significantly reduced. According to the test result of Comparative Example 2, it can be seen that the mixed solvent only adopts ethylene glycol, and the capacity retention rate of the battery is significantly reduced. It is thus illustrated that the ratio of ethylene glycol to ethanol in the mixed solvent of the present invention helps to significantly improve the cycle performance of sodium ion batteries. According to the test results of Comparative Examples 3 and 4, it can be seen that when the process parameters of step 2 chelate reaction are changed, the capacity retention rate of the battery produces extremely significant deterioration. It is thus illustrated that the process parameters of the chelate reaction of the present invention help to significantly improve the cycle performance of sodium ion batteries. According to the test result of Comparative Example 5, it can be seen that the method for high temperature combustion+annealing is used to prepare positive electrode material. The capacity retention rate of the battery is obviously less than that of Example 1. It is thus illustrated that the method for low temperature chelation+open flame combustion is used to prepare positive electrode material, which helps to significantly improve the cycle performance of sodium ion batteries.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention and are not limiting. Other modifications or equivalent substitutions made to the technical solution of the present invention by ordinary technicians in this field should be included in the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for preparing a layered oxide positive electrode material for a sodium ion battery, characterized in that: The following steps are involved: Step 1: providing a sodium source and a metal source; Step 2: dissolving an inorganic salt or organic salt of a metal source and a sodium source in a mixed solvent of ethylene glycol and ethanol in a stoichiometric ratio to obtain a mixed solution; Step 3: Stir the mixed solution at 50-90°C for more than 5 hours to carry out the chelation reaction; Step 4: After the reaction is complete, the mixed solution is transferred to an alumina crucible and burned with an open flame until the mixed solution is completely formed into a powdery material to obtain a sodium ion battery layered oxide positive electrode material.

2. The method for preparing a layered oxide positive electrode material for a sodium ion battery according to claim 1, wherein: The sodium source is a mixture of one or more of sodium chloride, sodium nitrate, sodium acetate, sodium citrate and sodium malate; The metal source is a mixture of one or more of magnesium, iron, titanium, copper, manganese, vanadium, chromium, nickel, cobalt, zinc, aluminum, zirconium and niobium; The inorganic salt or organic salt of the metal source is a mixture of one or more of chloride, acetate, nitrate, iodide, citrate, malate, tartrate, benzoate and metal ester of the metal source.

3. The method for preparing a layered oxide positive electrode material for sodium ion batteries according to claim 1, wherein: In the mixed solvent of ethylene glycol and ethanol, the volume ratio of ethylene glycol to ethanol is 1:(1-5).

4. The method for preparing a layered oxide positive electrode material for sodium ion batteries according to claim 1, wherein: The total concentration of metal ions and sodium ions in the mixed solution is 0.02-2 mol / L.

5. The method for preparing a layered oxide positive electrode material for sodium ion batteries according to claim 1, wherein: The process parameters of the low-temperature heating and heat preservation treatment include: heat preservation at 50-90° C. for 5-12 hours.

6. The method for preparing a layered oxide positive electrode material for sodium ion batteries according to claim 1, wherein: The open flame sintering is to burn the mixed solution with an open flame, and the center temperature of the flame reaches 800-1000°C.

7. A layered oxide positive electrode material for a sodium ion battery, obtained according to the preparation method according to any one of claims 1 to 6.

8. A positive electrode sheet comprising the sodium ion battery layered oxide positive electrode material according to claim 7.

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