Preparation method of nickel-iron-manganese oxide precursor and sodium ion layered oxide positive electrode material

Abstract

The invention discloses a preparation method of a nickel-iron-manganese oxide precursor and a sodium ion layered oxide positive electrode material, and belongs to the technical field of sodium ion battery materials, and the preparation method comprises the following steps: mixing a nickel source, an iron source and a manganese source according to a molar ratio, a first mixture is obtained; then sintering the first mixture in an air atmosphere at 400-850 DEG C for 4-8 hours to prepare a nickel-iron-manganese oxide precursor; mixing the prepared nickel-iron-manganese oxide precursor with a sodium source and the blend T according to a molar ratio; the preparation method comprises the following steps: mixing a first mixture and a second mixture to obtain a second mixture, and sintering the second mixture in an air atmosphere at 500-1000 DEG C for 15-30 hours to prepare the sodium ion layered oxide positive electrode material which has good specific capacity and cycle performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sodium ion battery materials, and particularly relates to a preparation method of a nickel-iron-manganese oxide precursor and a sodium ion layered oxide positive electrode material. BACKGROUND

[0002] Sodium ion batteries have shown great application potential in large-scale energy storage, electric vehicles and other portable devices due to their abundant sodium resources, low-temperature performance and excellent fast-charging performance, and have attracted widespread attention in recent years. Layered oxides of sodium ion batteries have become one of the key directions of research on positive electrode materials of sodium ion batteries due to their high theoretical specific capacity and relatively stable structure. However, the current traditional sodium ion layered oxide positive electrode material faces many challenges in practical application, one of which is that the average cost of sodium ion batteries is still higher than that of lithium ion batteries.

[0003] Studies have shown that the cost of sodium ion layered oxide positive electrode material accounts for 30% of sodium ion batteries, and the cost of the precursor accounts for 40% of the positive electrode material. On the other hand, the morphology and structure characteristics of the precursor play a decisive role in the performance of the positive electrode material. Since the inheritance between the precursor and the positive electrode material and the large cost proportion of the precursor, it is particularly important to develop high-performance, low-cost precursors and positive electrode material preparation processes to improve the performance of sodium ion batteries and reduce the cost of sodium ion batteries. The preparation method of the traditional layered oxide positive electrode material precursor is the coprecipitation method. The coprecipitation method precursor has the advantages of uniform metal ions and high mixed phase purity. For example, patent CN120483286A discloses a manufacturing method of a nickel-iron-manganese hydroxide precursor, which specifically dissolves nickel sulfate, ferrous sulfate and manganese sulfate in deionized water in a specified proportion, then supplies a mixed solution of sodium hydroxide and ammonia water to a reaction kettle to obtain a bottom liquid, and controls the reaction conditions at a certain temperature to prepare a nickel-iron-manganese hydroxide precursor. However, the coprecipitation method for preparing nickel-iron-manganese precursor has problems such as high cost of waste liquid treatment, incomplete element precipitation, and complex manufacturing process.

[0004] In summary, there is an urgent need for a preparation method of a nickel-iron-manganese oxide precursor and a sodium ion layered oxide positive electrode material to solve this problem. SUMMARY

[0005] The first aspect of the application aims to provide a preparation method of a nickel-iron-manganese oxide precursor with better specific capacity and cycle performance.

[0006] To achieve the above-mentioned purpose, the application adopts the following technical solutions: The application discloses a preparation method of a nickel-iron-manganese oxide precursor, and belongs to the technical field of inorganic materials.

[0007] The nickel-iron-manganese oxide prepared by the method has a structural formula of: Ni x Fe y Mn z O2 (x+y+z=1).

[0008] Further settings are as follows: The nickel source is selected from one or more of nickel-based metal organic framework materials, triniickel tetroxide, di-nickel trioxide, nickel protoxide, basic nickel oxide NiO(OH), nickel hydroxide, nickel protoxide hydroxide, nickelous sulfate, nickel sulfate, nickel nitrate, nickel acetate, nickel nitrate nonahydrate, nickel protoxide nitrate, nickel chloride, nickel bromide, nickel phosphate, nickel phosphite, nickel carbonate, nickel oxalate, nickel oxalate, nickel acetate, nickel citrate.

[0009] The iron source is selected from one or more of iron-based metal organic framework materials, triiron tetroxide, di-iron trioxide, iron protoxide, basic iron oxide FeO(OH), iron hydroxide, ferrous hydroxide, ferrous sulfate, iron sulfate, iron nitrate, iron acetate, iron nitrate nonahydrate, ferrous nitrate, iron chloride, iron bromide, iron phosphate, ferrous phosphate, iron carbonate, iron oxalate, ferrous oxalate, iron acetate, iron citrate, ferrous citrate.

[0010] The manganese source is selected from one or more of manganese-based metal organic framework materials, trimanganese tetroxide, dimanganese trioxide, manganese protoxide, manganese oxide, manganese dioxide, monohydroxy monoxide manganese MnO(OH), manganese dioxide hydrate MnO(OH)2, manganese hydroxide Mn(OH)2, manganese carbonate, manganese sulfate, manganese nitrate, manganese acetate, manganese citrate, manganese oxalate, manganese formate, manganese acetate, manganese phosphate.

[0011] The molar ratio of the nickel source, the iron source and the manganese source is preferably 1:1-2:1-2, and particularly preferably 1:2:2.

[0012] The rotation speed of the mixing of the nickel source, the iron source and the manganese source is 600-1500 rpm, and the mixing time is 15-60 min, and particularly preferably the rotation speed of the mixing is 1000 rpm, and the mixing time is 30 min.

[0013] The second aspect of the present application is to provide a preparation method of sodium ion layered oxide positive electrode material, comprising the following steps: mixing the nickel-iron-manganese oxide precursor prepared in the preceding step with a sodium source and a blend T according to a molar ratio to obtain a second mixture, and then sintering the second mixture under an air atmosphere at 500-1000 DEG C for 15-30 hours to obtain the sodium ion layered oxide positive electrode material.

[0014] The prepared sodium ion layered oxide positive electrode material has a structural formula of Na a Ni x Fe y Mn z T (1-x-y-z) O2, wherein 0.88≤a≤1.032, 0.15≤x≤0.2, 0.35≤y≤0.4, and 0.35≤z≤0.4; T is a doping element, and the T is selected from at least one of Al, Cr, Co, Fe, Mg, Ti, V, Ni, Cu, Zn, Zr, Nb, Mo, W, Ca, Y, La, Ce, Ga, In, and Sn.

[0015] Preferably, To further improve the specific capacity of the sodium nickel-iron-manganese oxide, the sintering process adopts gradient sintering, the first sintering temperature is 500-850 DEG C, the heating rate is 2-10 DEG C / min, and the time is 1-10 hours; the second sintering temperature is 850-1000 DEG C, the heating rate is 2-10 DEG C / min, and the time is 12-20 hours.

[0016] Further, the blend T is a doping element selected from at least one of Al, Cr, Co, Fe, Mg, Ti, V, Ni, Cu, Zn, Zr, Nb, Mo, W, Ca, Y, La, Ce, Ga, In, and Sn. The blend T can be at least one of oxides, hydroxides, halides, sulfates, carbonates, nitrates, and nitric oxide compounds of the above-mentioned doping elements.

[0017] The sodium source is selected from at least one of sodium carbonate, sodium hydroxide, sodium oxide, sodium peroxide, sodium bicarbonate, sodium phosphate, sodium dihydrogen phosphate, sodium hydrogen phosphate, sodium oxalate, sodium acetate, sodium sulfate, sodium nitrate, sodium chloride, sodium sulfide, sodium citrate, sodium benzoate, sodium borate, sodium metaborate, and sodium tetrachloroborate.

[0018] Compared with the prior art, the present application has the following advantages: (1) The nickel-iron-manganese oxide precursor is used to prepare the sodium ion layered oxide positive electrode material, compared with the traditional hydroxide precursor for preparing the positive electrode material, the steps are simple and easy to operate, the reaction conditions are mild, the manufacturing cost is relatively low, and the prepared product has excellent performance and is suitable for large-scale production and application.

[0019] (2) The nickel-iron-manganese oxide precursor is prepared from at least two metal organic framework materials of a nickel source, a manganese source and an iron source. After high-temperature treatment, the internal organic ligand of the metal organic framework material is removed, forming a metal oxide precursor with a porous structure of nanometer size. The precursor is beneficial to the diffusion of sodium ions in the sintering process after mixing, and is also beneficial to the doping of other elements in the positive electrode material. The sodium ion layered oxide positive electrode material prepared from the oxide precursor has better specific capacity and cycle performance. The particles of the oxide precursor prepared by the present application are more compact and round. The layered oxide positive electrode material sintered from the oxide precursor also has compact and round primary particles, reduces the negative reaction of the material interface in the charging and discharging process, effectively improves the structural stability of the material, and fully plays the specific capacity and cycle performance of the material. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 SEM image of the nickel-iron-manganese oxide precursor prepared in Example 1 of the present application.

[0021] Figure 2 SEM image of the layered oxide positive electrode material prepared in Example 1 of the present application.

[0022] Figure 3 SEM image of the layered oxide positive electrode material prepared in Comparative Example 1 of the present application.

[0023] Figure 4 XRD image of the layered oxide positive electrode materials prepared in Comparative Example 1 and Example 1 of the present application.

[0024] Figure 5 Charge-discharge curve of the layered oxide positive electrode materials prepared in Comparative Example 1 and Example 1 of the present application. DETAILED DESCRIPTION

[0025] The present application will be explained in more detail by specific embodiments. However, it should be understood that the specific functional details disclosed in the specification should not be interpreted as limiting, but merely as representative of a representative basis for teaching a person skilled in the art to employ the present application in different ways in any appropriate detailed embodiment. The raw materials and reagents used in the embodiments, if not specifically stated, are existing technologies or commercially available products in the art.

[0026] In the following examples and comparative examples, the nickel-based, iron-based and manganese-based metal organic framework materials are prepared by the following method.

[0027] The preparation method of the nickel-based metal organic framework material is as follows: the nickel source is Ni(CH3COO)2·4H2O, and the organic ligand is dihydroxy terephthalic acid. 0.989 g of the nickel source is dissolved in 5 mL of an ethanol and water mixed solution (the volume ratio of ethanol to water in the mixed solution is 1:1) to obtain a nickel-containing solution. 0.308 g of the organic ligand is dissolved in 35 mL of an N,N-dimethylformamide (DMF) solution to obtain an organic ligand solution. The organic ligand solution is poured into the above nickel-containing solution, stirred at room temperature for 25 minutes, and then placed in a polytetrafluoroethylene-lined autoclave, and kept at 125°C for 24 hours to obtain a precipitate. After washing and drying treatment, the nickel-based metal organic framework material is obtained.

[0028] The preparation method of the iron-based metal organic framework material is as follows: the iron source is Fe(CH3COO)2·4H2O, and the organic ligand is dihydroxy terephthalic acid. 1.045 g of the iron source is dissolved in 5 mL of an ethanol and water mixed solution (the volume ratio of ethanol to water in the mixed solution is 1:1) to obtain an iron-containing solution. 0.325 g of the organic ligand is dissolved in 35 mL of an N,N-dimethylformamide (DMF) solution to obtain an organic ligand solution. The organic ligand solution is poured into the above iron-containing solution, stirred at room temperature for 25 minutes, and then placed in a polytetrafluoroethylene-lined autoclave, and kept at 115°C for 22 hours to obtain a precipitate. After washing and drying treatment, the iron-based metal organic framework material is obtained.

[0029] The preparation method of the manganese-based metal organic framework material is as follows: the manganese source is Mn(CH3COO)2·4H2O, and the organic ligand is dihydroxy terephthalic acid. 0.974 g of the manganese source is dissolved in 5 mL of an ethanol and water mixed solution (the volume ratio of ethanol to water in the mixed solution is 1:1) to obtain a manganese-containing solution. 0.303 g of the organic ligand is dissolved in 35 mL of an N,N-dimethylformamide (DMF) solution to obtain an organic ligand solution. The organic ligand solution is poured into the above manganese-containing solution, stirred at room temperature for 25 minutes, and then placed in a polytetrafluoroethylene-lined autoclave, and kept at 135°C for 24 hours to obtain a precipitate. After washing and drying treatment, the manganese-based metal organic framework material is obtained.

[0030] Example 1

[0031] (1) Preparation of a nickel-iron-manganese oxide precursor The nickel-based, iron-based, and manganese-based metal organic framework materials are mixed in a molar ratio of Ni:Fe:Mn=1:2:2, the rotation speed is 1000 rpm, the mixing time is 30 min, and the temperature is controlled below 50°C during mixing. The mixture is placed in a muffle furnace at 550°C and sintered in an air atmosphere for 6 hours to obtain a nickel-iron-manganese oxide precursor Ni 1 / 5 Fe 2 / 5 Mn 2 / 5 O2.

[0032] Product characterization: like Figure 1 The image shown is a SEM image of the nickel-iron-manganese oxide precursor. This precursor is prepared from at least two metal-organic framework materials selected from nickel, manganese, and iron sources. After high-temperature treatment, the organic ligands inside the metal-organic framework materials are removed, forming a metal oxide precursor with a porous structure of nanoscale. This precursor is beneficial for the diffusion of sodium ions during the sintering process after mixing, and also facilitates the doping of other elements in the cathode material. The sodium ion layered oxide cathode material prepared from this oxide precursor has better specific capacity and cycle performance.

[0033] (2) Preparation of layered oxide cathode materials Ni, a precursor of nickel-iron-manganese oxide 1 / 5 Fe 2 / 5 Mn 2 / 5 O2, sodium carbonate, blend T (a mixture of calcium carbonate, copper oxide, and zinc oxide, with an elemental molar ratio of Ca:Cu:Zn = 1:3:6), based on the elemental molar ratio of Na:Ni x Fe y Mn z The ratio of T = 1.025:0.90:0.1 was weighed and placed in a mixer, where it was stirred at 1000 rpm to obtain a mixture. The mixture was then sintered at 650℃ for 3 hours in air and then at 930℃ for 19 hours. After sintering, it was allowed to cool naturally to room temperature, pulverized, and passed through a 200-mesh sieve to obtain the sodium ion layered oxide cathode material Na. 1.025 Ni x Fe y Mn z T 0.1 O2 (x+y+z=0.9).

[0034] Product characterization: SEM images of the prepared sodium ion layered oxide cathode material are shown below. Figure 2 As shown, the oxide precursor prepared by this invention has more dense and rounded particles. The primary particles of the layered oxide cathode material after sintering the oxide precursor are also dense and rounded, which reduces the negative reaction at the material interface during charging and discharging, effectively improves the structural stability of the material, and allows the specific capacity and cycle performance of the material to be fully utilized.

[0035] Example 2

[0036] Nickel-based, iron-based, and manganese-based metal-organic framework materials were mixed in an elemental molar ratio of Ni:Fe:Mn = 1:2:2 at a rotation speed of 1000 rpm for 30 minutes, with the mixing temperature controlled below 50℃. The mixture was then subjected to solid-state sintering at 550℃ in air for 6 hours to obtain the nickel-iron-manganese oxide precursor Ni. 1 / 5 Fe 2 / 5 Mn 2 / 5 O2.

[0037] Ni, a precursor of nickel-iron-manganese oxide 1 / 5 Fe 2 / 5 Mn 2 / 5 O2, sodium carbonate, blend T (a mixture of calcium carbonate, copper oxide, and zinc oxide, with an elemental molar ratio of Ca:Cu:Zn = 1:3:6), based on the elemental molar ratio of Na:Ni x Fe y Mn z The ratio of T = 1.025:0.90:0.1 was weighed and placed in a mixer, where it was stirred at 1000 rpm to obtain a mixture. The mixture was then sintered at 650 °C for 3 hours in air and then at 930 °C for 17 hours. After sintering, it was allowed to cool naturally to room temperature, pulverized, and passed through a 200-mesh sieve to obtain the sodium ion layered oxide cathode material Na. 1.025 Ni x Fe y Mn z T 0.1 O2 (x+y+z=0.9).

[0038] Example 3

[0039] Nickel-based, iron-based, and manganese-based metal-organic framework materials were mixed in an elemental molar ratio of Ni:Fe:Mn = 1:2:2 at a rotation speed of 1000 rpm for 30 minutes, with the mixing temperature controlled below 50℃. The mixture was then subjected to solid-state sintering at 550℃ in air for 6 hours to obtain the nickel-iron-manganese oxide precursor Ni. 1 / 5 Fe 2 / 5 Mn 2 / 5 O2.

[0040] Ni, a precursor of nickel-iron-manganese oxide 1 / 5 Fe 2 / 5 Mn 2 / 5 O2, sodium carbonate, blend T (a mixture of calcium carbonate, copper oxide, and zinc oxide, with an elemental molar ratio of Ca:Cu:Zn = 1:3:6), based on the elemental molar ratio of Na:Ni x Fe y Mn zThe ratio of T = 1.025:0.90:0.1 was weighed and placed in a mixer, where it was stirred at 1000 rpm to obtain a mixture. This mixture was then sintered at 650 °C for 3 hours in air and then at 930 °C for 15 hours. After sintering, it was allowed to cool naturally to room temperature, pulverized, and passed through a 200-mesh sieve to obtain the sodium ion layered oxide cathode material Na. 1.025 Ni x Fe y Mn z T 0.1 O2 (x+y+z=0.9).

[0041] Example 4

[0042] Nickel-based, iron-based, and manganese-based metal-organic framework materials were mixed in an elemental molar ratio of Ni:Fe:Mn = 1:2:2 at a rotation speed of 1000 rpm for 30 minutes, with the mixing temperature controlled below 50℃. The mixture was then subjected to solid-state sintering at 550℃ in air for 6 hours to obtain the nickel-iron-manganese oxide precursor Ni. 1 / 5 Fe 2 / 5 Mn 2 / 5 O2.

[0043] Ni, a precursor of nickel-iron-manganese oxide 1 / 5 Fe 2 / 5 Mn 2 / 5 O2, sodium carbonate, blend T (a mixture of calcium carbonate, copper oxide, and zinc oxide, with an elemental molar ratio of Ca:Cu:Zn = 1:3:6), based on the elemental molar ratio of Na:Ni x Fe y Mn z The ratio of T = 1.025:0.90:0.1 was weighed and placed in a mixer, where it was stirred at 1000 rpm to obtain a mixture. This mixture was then sintered at 650℃ for 3 hours in air and then at 910℃ for 19 hours. After sintering, it was allowed to cool naturally to room temperature, pulverized, and passed through a 200-mesh sieve to obtain the sodium ion layered oxide cathode material Na. 1.025 Ni x Fe y Mn z T 0.1 O2 (x+y+z=0.9).

[0044] Example 5

[0045] Nickel-based, iron-based, and manganese-based metal-organic framework materials were mixed in an elemental molar ratio of Ni:Fe:Mn = 1:2:2 at a rotation speed of 1000 rpm for 30 minutes, with the mixing temperature controlled below 50℃. The mixture was then subjected to solid-state sintering at 550℃ in air for 6 hours to obtain the nickel-iron-manganese oxide precursor Ni.1 / 5 Fe 2 / 5 Mn 2 / 5 O2.

[0046] Ni, a precursor of nickel-iron-manganese oxide 1 / 5 Fe 2 / 5 Mn 2 / 5 O2, sodium carbonate, blend T (a mixture of calcium carbonate, copper oxide, and zinc oxide, with an elemental molar ratio of Ca:Cu:Zn = 1:3:6), based on the elemental molar ratio of Na:Ni x Fe y Mn z The ratio of T = 1.025:0.90:0.1 was weighed and placed in a mixer, and stirred at 1000 rpm to obtain a mixture. The mixture was sintered at 650 °C for 3 h in air atmosphere, and then sintered at 910 °C for 17 h. After sintering, it was naturally cooled to room temperature, pulverized, and passed through a 200-mesh sieve to obtain the sodium ion layered oxide cathode material Na. 1.025 NixFeyMnzT 0.1 O2 (x+y+z=0.9).

[0047] Example 6

[0048] Nickel-based, iron-based, and manganese-based metal-organic framework materials were mixed in an elemental molar ratio of Ni:Fe:Mn = 1:2:2 at a rotation speed of 1000 rpm for 30 minutes, with the mixing temperature controlled below 50℃. The mixture was then subjected to solid-state sintering at 550℃ in air for 6 hours to obtain the nickel-iron-manganese oxide precursor Ni. 1 / 5 Fe 2 / 5 Mn 2 / 5 O2.

[0049] Ni, a precursor of nickel-iron-manganese oxide 1 / 5 Fe 2 / 5 Mn 2 / 5 O2, sodium carbonate, blend T (a mixture of calcium carbonate, copper oxide, and zinc oxide, with an elemental molar ratio of Ca:Cu:Zn = 1:3:6), based on the elemental molar ratio of Na:Ni x Fe y Mn z The ratio of T = 1.025:0.90:0.1 was weighed and placed in a mixer, and stirred at 1000 rpm to obtain a mixture. The mixture was sintered at 650 °C for 3 h in air atmosphere, and then sintered at 910 °C for 15 h. After sintering, it was naturally cooled to room temperature, pulverized, and passed through a 200-mesh sieve to obtain the sodium ion layered oxide cathode material Na. 1.025 Ni x Fe y Mn z T 0.1O2 (x+y+z=0.9).

[0050] Example 7

[0051] Nickel-based, iron-based, and manganese-based metal-organic framework materials were mixed in an elemental molar ratio of Ni:Fe:Mn = 1:2:2 at a rotation speed of 1000 rpm for 30 minutes, with the mixing temperature controlled below 50℃. The mixture was then subjected to solid-state sintering at 550℃ in air for 6 hours to obtain the nickel-iron-manganese oxide precursor Ni. 1 / 5 Fe 2 / 5 Mn 2 / 5 O2.

[0052] Ni, a precursor of nickel-iron-manganese oxide 1 / 5 Fe 2 / 5 Mn 2 / 5 O2, sodium carbonate, blend T (a mixture of calcium carbonate, copper oxide, and zinc oxide, with an elemental molar ratio of Ca:Cu:Zn = 1:6:3), based on the elemental molar ratio of Na:Ni x Fe y Mn z The ratio of T = 1.025:0.90:0.1 was weighed and placed in a mixer, where it was stirred at 1000 rpm to obtain a mixture. This mixture was then sintered at 650 °C for 3 hours in air, followed by sintering at 930 °C for 17 hours. After sintering, it was allowed to cool naturally to room temperature, pulverized, and passed through a 200-mesh sieve to obtain the sodium ion layered oxide cathode material Na. 1.025 Ni x Fe y Mn z T 0.1 O2 (x+y+z=0.9).

[0053] Example 8

[0054] Nickel-based, iron-based, and manganese-based metal-organic framework materials were mixed in an elemental molar ratio of Ni:Fe:Mn = 1:2:2 at a rotation speed of 1000 rpm for 30 minutes, with the mixing temperature controlled below 50℃. The mixture was then subjected to solid-state sintering at 550℃ in air for 6 hours to obtain the nickel-iron-manganese oxide precursor Ni. 1 / 5 Fe 2 / 5 Mn 2 / 5 O2.

[0055] Ni, a precursor of nickel-iron-manganese oxide 1 / 5 Fe 2 / 5 Mn 2 / 5 O2, sodium carbonate, blend T (a mixture of calcium carbonate, copper oxide, and zinc oxide, with an elemental molar ratio of Ca:Cu:Zn = 1:6:3), based on the elemental molar ratio of Na:Ni x Fey Mn z The ratio of T = 1.025:0.90:0.1 was weighed and placed in a mixer, where it was stirred at 1000 rpm to obtain a mixture. This mixture was then sintered at 650 °C for 3 hours in air and then at 930 °C for 19 hours. After sintering, it was allowed to cool naturally to room temperature, pulverized, and passed through a 200-mesh sieve to obtain the sodium ion layered oxide cathode material Na. 1.025 Ni x Fe y Mn z T 0.1 O2 (x+y+z=0.9).

[0056] Example 9

[0057] Nickel-based, iron-based, and manganese-based metal-organic framework materials were mixed in an elemental molar ratio of Ni:Fe:Mn = 1:2:2 at a rotation speed of 1000 rpm for 30 minutes, with the mixing temperature controlled below 50℃. The mixture was then subjected to solid-state sintering at 550℃ in air for 6 hours to obtain the nickel-iron-manganese oxide precursor Ni. 1 / 5 Fe 2 / 5 Mn 2 / 5 O2.

[0058] Ni, a precursor of nickel-iron-manganese oxide 1 / 5 Fe 2 / 5 Mn 2 / 5 O2, sodium carbonate, blend T (a mixture of calcium carbonate, copper oxide, and zinc oxide, with an elemental molar ratio of Ca:Cu:Zn = 3:1:6), based on the elemental molar ratio of Na:Ni x Fe y Mn z The ratio of T = 1.025:0.90:0.1 was weighed and placed in a mixer, where it was stirred at 1000 rpm to obtain a mixture. This mixture was then sintered at 650 °C for 3 hours in air, followed by sintering at 930 °C for 17 hours. After sintering, it was allowed to cool naturally to room temperature, pulverized, and passed through a 200-mesh sieve to obtain the sodium ion layered oxide cathode material Na. 1.025 Ni x Fe y Mn z T 0.1 O2 (x+y+z=0.9).

[0059] Example 10

[0060] Nickel-based, iron-based, and manganese-based metal-organic framework materials were mixed in an elemental molar ratio of Ni:Fe:Mn = 1:2:2 at a rotation speed of 1000 rpm for 30 minutes, with the mixing temperature controlled below 50℃. The mixture was then subjected to solid-state sintering at 550℃ in air for 6 hours to obtain the nickel-iron-manganese oxide precursor Ni. 1 / 5 Fe 2 / 5 Mn 2 / 5 O2.

[0061] Ni, a precursor of nickel-iron-manganese oxide 1 / 5 Fe 2 / 5 Mn 2 / 5 O2, sodium carbonate, blend T (a mixture of calcium carbonate, copper oxide, and zinc oxide, with an elemental molar ratio of Ca:Cu:Zn = 3:1:6), based on the elemental molar ratio of Na:Ni x Fe y Mn z The ratio of T = 1.025:0.90:0.1 was weighed and placed in a mixer, where it was stirred at 1000 rpm to obtain a mixture. This mixture was then sintered at 650 °C for 3 hours in air and then at 930 °C for 19 hours. After sintering, it was allowed to cool naturally to room temperature, pulverized, and passed through a 200-mesh sieve to obtain the sodium ion layered oxide cathode material Na. 1.025 Ni x Fe y Mn z T 0.1 O2 (x+y+z=0.9).

[0062] Comparative Example 1

[0063] Referring to Example 1, the difference is that no element was doped in Comparative Example 1, thus the influence of doping elements on the morphology and properties of the material was examined. The preparation method is as follows:

[0064] Nickel-based, iron-based, and manganese-based metal-organic framework materials were mixed in an elemental molar ratio of Ni:Fe:Mn = 1:2:2 at a rotation speed of 1000 rpm for 30 minutes, with the mixing temperature controlled below 50℃. The mixture was then subjected to solid-state sintering at 550℃ in air for 6 hours to obtain the nickel-iron-manganese oxide precursor Ni. 1 / 5 Fe 2 / 5 Mn 2 / 5 O2.

[0065] Ni, a precursor of nickel-iron-manganese oxide 1 / 5 Fe 2 / 5 Mn 2 / 5 O2, sodium carbonate, in the elemental molar ratio Na:Ni x Fe y Mn zThe ratio of sodium ions to oxides was 1.025:1. The mixture was weighed and placed in a mixer, stirred at 1000 rpm to obtain a final product. This mixture was then sintered in air at 650°C for 3 hours, followed by sintering at 930°C for 19 hours. After sintering, the mixture was allowed to cool naturally to room temperature, pulverized, and passed through a 200-mesh sieve to obtain the sodium ion layered oxide cathode material Na. 1.025 Ni x Fe y Mn z O2(x+y+z=1).

[0066] Product characterization: SEM images of the layered oxide cathode material prepared in Comparative Example 1 are shown below. Figure 3 As shown.

[0067] Comparative Example 2

[0068] Referring to Example 1, the difference is that: Comparative Example 2 investigated the effect of increasing the sintering temperature on the morphology and properties of the material. The preparation method is as follows:

[0069] Nickel-based, iron-based, and manganese-based metal-organic framework materials were mixed in an elemental molar ratio of Ni:Fe:Mn = 1:2:2 at a rotation speed of 1000 rpm for 30 minutes, with the mixing temperature controlled below 50℃. The mixture was then subjected to solid-state sintering at 550℃ in air for 6 hours to obtain the nickel-iron-manganese oxide precursor Ni. 1 / 5 Fe 2 / 5 Mn 2 / 5 O2.

[0070] Ni, a precursor of nickel-iron-manganese oxide 1 / 5 Fe 2 / 5 Mn 2 / 5 O2, sodium carbonate, blend T (a mixture of calcium carbonate, copper oxide, and zinc oxide, with an elemental molar ratio of Ca:Cu:Zn = 1:3:6), based on the elemental molar ratio of Na:Ni x Fe y Mn z The ratio of T = 1.025:0.90:0.1 was weighed and placed in a mixer, and stirred at 1000 rpm to obtain a mixture. The mixture was sintered at 650℃ for 3 hours in air atmosphere, and then sintered at 960℃ for 19 hours. After sintering, it was naturally cooled to room temperature, pulverized, and passed through a 200-mesh sieve to obtain the sodium ion layered oxide cathode material Na. 1.025 Ni x Fe y Mn z T 0.1 O2 (x+y+z=0.9).

[0071] Comparative Example 3

[0072] Referring to Example 1, the difference is that Comparative Example 3 only doped with Ca, and the effect of a single dopant element on the morphology and properties of the material was investigated. The preparation method is as follows:

[0073] Nickel-based, iron-based, and manganese-based metal-organic framework materials were mixed in an elemental molar ratio of Ni:Fe:Mn = 1:2:2 at a rotation speed of 1000 rpm for 30 minutes, with the mixing temperature controlled below 50℃. The mixture was then subjected to solid-state sintering at 550℃ in air for 6 hours to obtain the nickel-iron-manganese oxide precursor Ni. 1 / 5 Fe 2 / 5 Mn 2 / 5 O2.

[0074] Ni, a precursor of nickel-iron-manganese oxide 1 / 5 Fe 2 / 5 Mn 2 / 5 O2, sodium carbonate, calcium carbonate, in elemental molar ratio Na:Ni x Fe y Mn z The ratio of Ca:1.025:0.90:0.1 was weighed and placed in a mixer, where it was stirred at 1000 rpm to obtain a mixture. This mixture was then sintered at 650 °C for 3 hours in air, followed by sintering at 930 °C for 19 hours. After sintering, it was allowed to cool naturally to room temperature, pulverized, and passed through a 200-mesh sieve to obtain the sodium ion layered oxide cathode material Na. 1.025 Ni x Fe y Mn z T 0.1 O2 (x+y+z=0.9, T is Ca).

[0075] Comparative Example 4

[0076] Referring to Example 1, the difference is that Comparative Example 4 only doped with Cu, and the effect of a single doping element on the morphology and properties of the material was investigated. The preparation method is as follows: Nickel-based, iron-based, and manganese-based metal-organic framework materials were mixed in an elemental molar ratio of Ni:Fe:Mn = 1:2:2 at a rotation speed of 1000 rpm for 30 minutes, with the mixing temperature controlled below 50℃. The mixture was then subjected to solid-state sintering at 550℃ in air for 6 hours to obtain the nickel-iron-manganese oxide precursor Ni. 1 / 5 Fe 2 / 5 Mn 2 / 5 O2.

[0077] Ni, a precursor of nickel-iron-manganese oxide 1 / 5 Fe 2 / 5 Mn 2 / 5 O2, sodium carbonate, copper oxide, in the elemental molar ratio Na:Nix Fe y Mn z The ratio of Cu:1.025:0.90:0.1 was weighed and placed in a mixer, where it was stirred at 1000 rpm to obtain a mixture. This mixture was then sintered at 650 °C for 3 hours in air, followed by sintering at 930 °C for 19 hours. After sintering, it was allowed to cool naturally to room temperature, pulverized, and passed through a 200-mesh sieve to obtain the sodium ion layered oxide cathode material Na. 1.025 Ni x Fe y Mn z T 0.1 O2 (x+y+z=0.9, T is Cu).

[0078] Comparative Example 5

[0079] Using Example 1 as a reference, Comparative Example 5, which only doped with Zn, investigated the effect of a single dopant element on the morphology and properties of the material. The preparation method is as follows: Nickel-based, iron-based, and manganese-based metal-organic framework materials were mixed in an elemental molar ratio of Ni:Fe:Mn = 1:2:2 at a rotation speed of 1000 rpm for 30 minutes, with the mixing temperature controlled below 50℃. The mixture was then subjected to solid-state sintering at 550℃ in air for 6 hours to obtain the nickel-iron-manganese oxide precursor Ni. 1 / 5 Fe 2 / 5 Mn 2 / 5 O2.

[0080] Ni, a precursor of nickel-iron-manganese oxide 1 / 5 Fe 2 / 5 Mn 2 / 5 O2, sodium carbonate, zinc oxide, in the elemental molar ratio Na:Ni x Fe y Mn z The Zn ratio (1.025:0.90:0.1) was weighed and placed in a mixer, where it was stirred at 1000 rpm to obtain a mixture. This mixture was then sintered at 650 °C for 3 hours in air, followed by sintering at 930 °C for 19 hours. After sintering, the mixture was allowed to cool naturally to room temperature, pulverized, and passed through a 200-mesh sieve to obtain the sodium ion layered oxide cathode material Na. 1.025 Ni x Fe y Mn z T 0.1 O2 (x+y+z=0.9, T is Zn).

[0081] Performance testing

[0082] Battery Assembly: The sodium-ion layered oxide positive electrode material prepared in the aforementioned examples and comparative examples was mixed with SP (conductive carbon black) and PVDF (polyvinylidene fluoride) at a mass ratio of 8:1:1. The PVDF was pre-prepared into a 4%wt PVDF solution using NMP (N-methylpyrrolidone) as a solvent. After stirring into a slurry, the slurry was coated onto a 15μm thick aluminum foil. The resulting electrode was dried, stamped, and pressed to form the sodium-ion battery positive electrode material. Using metallic sodium as the negative electrode and a PE separator with dimensions of 14μm × 60mm, the CR2016 button cell was assembled in an argon-filled glove box in the following order: positive electrode shell, positive electrode sheet, electrolyte, separator, sodium sheet, nickel mesh, electrolyte, and negative electrode shell.

[0083] After the battery was assembled, charge and discharge tests were performed. Under the voltage range of 2.0-4.0V, the battery was first cycled twice at 0.2C, and then the capacity and cycle performance were tested at 1C. The test results are shown in Table 1.

[0084] Table 1 .

[0085] As can be seen from Table 1: (1) Comparison of Examples 1-3 shows that the sodium ion layered oxide cathode materials prepared with different sintering times have different performance. The specific capacity of the first discharge at 0.2C current in Example 3 can reach 137.23 mAh·g. -1 After 100 cycles at 1C, the capacity retention rate reaches 90.42%. By adjusting the sintering time at 930℃ in the constant temperature zone, the first-cycle discharge specific capacity at 0.2C current in Example 1 reaches 138.56 mAh·g. -1 After 100 cycles at 1C, the capacity retention rate reaches 93.49%, which is the best performance.

[0086] (2) By comparing Examples 4-6, we can see the effect of changing the sintering temperature on the performance of sodium ion layered oxide cathode materials. Lowering the sintering temperature will affect the formation of primary single crystal particles, thereby affecting the cycle performance of the material.

[0087] (3) By comparison of Examples 7-10, it can be seen that in the preparation process of sodium ion layered oxide cathode material, when the proportion of zinc oxide in blend T is high, it is beneficial to the material capacity. When the proportion of copper oxide in blend T is high, it is beneficial to the improvement of cycle performance, but the material capacity is somewhat lost.

[0088] (4) Comparing Comparative Example 1 with Example 1, Example 1 was doped with multiple elements. Figure 2 This is a SEM image of the layered oxide cathode material prepared in Example 1. Figure 3The image shows a SEM image of the layered oxide cathode material prepared in Comparative Example 1. Comparing the two, the particle morphology of Example 1 is more rounded. Figure 4 A comparison of the XRD patterns of the two samples showed that the peak values ​​of 003 and 104 were higher in Example 1, indicating that the crystal formation of Example 1 was better. (Table 1 and...) Figure 5 Performance tests have also confirmed this.

[0089] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are exhaustively listed. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a nickel iron manganese oxide precursor, characterized by, The method comprises the following steps: The nickel source, the iron source and the manganese source are mixed in a molar ratio, at least two of the nickel source, the iron source and the manganese source being a metal organic framework material, to obtain a first mixture; and then the first mixture is sintered at 400-850 DEG C under an air atmosphere for 4-8 hours to obtain a nickel-iron-manganese oxide precursor.

2. The method of claim 1, wherein the method further comprises: The nickel source is selected from one or more of a nickel-based metal organic framework material, triniickel tetroxide, nickel sesquioxide, nickel protoxide, nickel basic oxide, nickel hydroxide, nickel protoxide hydroxide, nickelous sulfate, nickel sulfate, nickel nitrate, nickel acetate, nickel nitrate nonahydrate, nickelous nitrate, nickel chloride, nickel bromide, nickel phosphate, nickel phosphite, nickel carbonate, nickel oxalate, nickel oxalate, nickel acetate, nickel citrate. ​ 3. The method of claim 1, wherein the method further comprises: The iron source is selected from one or more of an iron-based metal organic framework material, triiron tetroxide, iron sesquioxide, ferrous oxide, iron basic oxide, iron hydroxide, ferrous hydroxide, ferrous sulfate, iron sulfate, iron nitrate, iron acetate, iron nitrate nonahydrate, ferrous nitrate, iron chloride, iron bromide, iron phosphate, iron phosphite, iron carbonate, iron oxalate, ferrous oxalate, iron acetate, iron citrate, ferrous citrate. ​ 4. The method of claim 1, wherein the method further comprises: The manganese source is selected from one or more of a manganese-based metal organic framework material, trimanganese tetroxide, manganese sesquioxide, manganese protoxide, manganese oxide, manganese dioxide, monohydroxy manganese monoxide, manganese dioxide hydrate, manganese hydroxide, manganese carbonate, manganese sulfate, manganese nitrate, manganese acetate, manganese citrate, manganese oxalate, manganese formate, manganese acetate, manganese phosphate. ​ 5. The method of claim 1, wherein the method further comprises: The molar ratio of the nickel source, the iron source and the manganese source is preferably 1:1-2:1-2. ​ 6. The method of claim 1, wherein the method further comprises: The rotation speed of the mixing of the nickel source, the iron source and the manganese source is 600-1500 rpm, and the mixing time is 15-60 min. ​ 7. A method for producing a sodium-ion layered-oxide positive electrode material, characterized by, The method comprises the following steps: mixing the nickel-iron-manganese oxide precursor prepared in claim 1 with a sodium source and a blend T in a molar ratio to obtain a second mixture, and then sintering the second mixture at 500-1000 DEG C under an air atmosphere for 15-30 hours to obtain a sodium ion layered oxide positive electrode material. A prepared sodium-ion layered oxide positive electrode material has a structural formula of: Na a Ni x Fe y Mn z T (1-x-y-z) O2, wherein 0.88≤a≤1.032, 0.15≤x≤0.2, 0.35≤y≤0.4, 0.35≤z≤0.4; T is a doping element, and the T is at least one selected from Al, Cr, Co, Fe, Mg, Ti, V, Ni, Cu, Zn, Zr, Nb, Mo, W, Ca, Y, La, Ce, Ga, In, Sn.

8. The method of claim 7, wherein the sodium-ion layered oxide cathode material is prepared by the following steps: (1) preparing a precursor of the sodium-ion layered oxide cathode material; (2) mixing the precursor with a solvent; (3) heating the mixture to obtain the sodium-ion layered oxide cathode material. The sintering process adopts gradient sintering, the first sintering temperature is 500-850 DEG C, the heating rate is 2-10 DEG C / min, and the time is 1-10 hours; the second sintering temperature is 850-1000 DEG C, the heating rate is 2-10 DEG C / min, and the time is 12-20 hours.

9. The method of claim 7, wherein the sodium-ion layered oxide cathode material is prepared by the following steps: (1) preparing a precursor of the sodium-ion layered oxide cathode material; (2) mixing the precursor with a solvent; (3) heating the mixture to obtain the sodium-ion layered oxide cathode material. The blend T, T is a doping element, and is selected from at least one of Al, Cr, Co, Fe, Mg, Ti, V, Ni, Cu, Zn, Zr, Nb, Mo, W, Ca, Y, La, Ce, Ga, In and Sn, and the blend T is at least one of an oxide, a hydroxide, a halide, a sulfate, a carbonate, a nitrate and a nitric oxide compound of the above-mentioned doping element.

10. The method of claim 7, wherein the sodium-ion layered oxide cathode material is prepared by the following steps: (1) preparing a precursor of the sodium-ion layered oxide cathode material; (2) mixing the precursor with a solvent; (3) heating the mixture to obtain the sodium-ion layered oxide cathode material. The sodium source is selected from at least one of sodium carbonate, sodium hydroxide, sodium oxide, sodium peroxide, sodium bicarbonate, sodium phosphate, sodium dihydrogen phosphate, sodium hydrogen phosphate, sodium oxalate, sodium acetate, sodium sulfate, sodium nitrate, sodium chloride, sodium sulfide, sodium citrate, sodium benzoate, sodium borate, sodium metaborate, sodium tetrachloroborate.

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