Titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material and preparation method thereof

Abstract

The invention discloses a titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material and a preparation method thereof, and belongs to the technical field of sodium ion battery positive electrode materials. The preparation method comprises the following steps: firstly, taking butyl titanate as a titanium source, adding deionized water, and then adding HNO3 to react to prepare a titanium nitrate solution; mixing sodium nitrate, nickel nitrate, manganese nitrate, ferric nitrate, a titanium nitrate solution, an organic fuel and a complexing agent in proportion; then, evaporating the solvent, and burning to obtain a precursor; then, grinding the precursor, and annealing in an air atmosphere; and finally, cooling to obtain the positive electrode material. Compared with a traditional preparation method, the preparation method has the advantages of being easy and convenient to operate, low in temperature, simple in raw material, short in annealing time, low in energy consumption and the like, manganese is replaced with titanium, the Jahn-Teller effect of the material is effectively inhibited, and therefore the charge-discharge performance and the cycle stability of the material are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of cathode materials for sodium-ion batteries, and particularly relates to a titanium-doped nickel-manganese-iron-based sodium-ion layered cathode material and a preparation method thereof. Background Art

[0002] Sodium-ion batteries (SIBs) have gradually become strong competitors to lithium-ion batteries due to the similar chemical properties of sodium to lithium, abundant resources, and low cost. The electrochemical performance of SIBs depends to a large extent on the performance of the electrode materials, especially the selection and optimization of the cathode materials. The quality of the cathode materials directly affects the capacity, lifespan, cycle stability, and high-current rapid charge-discharge ability of sodium-ion batteries. Therefore, in-depth research on sodium-ion battery cathode materials not only has important theoretical significance but also has significant practical value in promoting practical applications.

[0003] Currently, the mainstream preparation methods for O3-type Na x TMO2 (0.7 < X ≤ 1) include solid-phase method, sol-gel method, co-precipitation method, and hydrothermal method. However, these methods have certain limitations. The solid-phase method requires high-temperature treatment, which consumes a large amount of energy and is prone to phase inhomogeneity; the sol-gel method has a complex process, a long preparation cycle, and it is difficult to control the particle size and morphology; the co-precipitation method is easy to operate, but may introduce impurities and affect the purity; the hydrothermal method requires long time and high-pressure conditions and is not suitable for large-scale production.

[0004] Existing preparation methods such as the patent application number CN202211136473, a preparation method and application of a coated layered sodium-ion cathode material. The synthesis steps are as follows: Mix the sodium-ion layered oxide precursor Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH)2 and sodium carbonate, where Na / Me = 1.05, mix through a high-speed mixer, and sinter at 900°C for 15 h to obtain a nickel-iron-manganese oxide cathode material. Mix the obtained nickel-iron-manganese oxide cathode material and the oxide of B, where the molar ratio of the coating amount of the oxide of B is 0.1 mol%, and sinter at 400°C for 5 h to obtain a coated nickel-iron-manganese oxide cathode material. However, the sintering time of 15 h at 900°C in this preparation process is relatively long, which may lead to high energy consumption, over-sintering, or grain growth, thus affecting the microstructure and performance stability of the material. In addition, long-time high-temperature sintering will increase the production cost and requires precise control of temperature and time, thereby increasing the equipment and energy consumption burden.

[0005] As disclosed in patent application number CN202410301327, a sodium ion layered cathode material and its preparation method and application. The synthesis steps are as follows: according to the element molar ratio of Ni:Fe:Mn:Mg=0.23:0.25:0.47:0.05, a certain mass of NiSO4·6H2O, FeSO4·7H2O, MnSO4·H2O and MgSO4 are weighed respectively to prepare a 1.0 mol / L metal ion mixed solution; 2.0 mol / L NaOH solution is prepared as a precipitant, and 1.0 mol / L NH3H2O ​​solution is prepared as a complexing agent; the complexing agent solution is added to the reactor as a base liquid; three liquids are added to the reactor in parallel, the reaction temperature is 60°C, the pH value is 11, and a co-precipitation reaction is carried out in a protective atmosphere. After the reaction is completed, it is kept at a constant temperature for 2 hours, and then aged at room temperature. The reaction product is centrifuged and washed with deionized water until neutral to obtain a precipitate, and the washed precursor precipitate is dried to obtain the dried Mg 2+ The precursor M(OH)2 of the doped sodium ion material; the precursor M(OH)2 and the sodium salt Na2CO3 and the lithium salt Li2CO3 are ball-milled at a molar ratio of 1:0.4738:0.0412, the ball-milled mixture is ground into powder and sintered in an air atmosphere, first at 550°C for 6h, then at 1100°C for 18h, the heating rate of the two sinterings is maintained at 5°C / min, and the matrix is ​​obtained by cooling to room temperature with the furnace. The chemical formula of the matrix is ​​Na 0.92 Li 0.08 Ni 0.23 Fe 0.25 Mn 0.47 Mg 0.05 O2. However, this preparation process involves multiple steps, such as co-precipitation reaction, centrifugal washing, drying, ball milling and high-temperature sintering, etc. Each step takes a long time and requires precise control of various reaction conditions (temperature, time, pH value, etc.), making the preparation process more complicated and not conducive to large-scale production. Summary of the invention

[0006] The object of the present invention is to overcome one or more deficiencies of the prior art and to provide a titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material and a preparation method thereof.

[0007] The objective of the present invention is achieved through the following technical solutions:

[0008] Various cathode materials have been developed so far, including layered transition metal oxides (Na x TMO2; X≤1, where TM represents transition metals such as Ni, Co, Mn, Fe and Cu), polyanionic compounds and Prussian blue analogs (PBA). Among these materials, Na with O3 structure xTMO2 (0.7 < X ≤ 1) has advantages such as high theoretical capacity, ease of synthesis, and good production scalability. However, for O3-type Na x The main challenge faced by TMO2 (0.7 < X ≤ 1) is Na + with a relatively large ionic radius, resulting in slow diffusion kinetics, which in turn affects high-rate performance. In addition, during the charge-discharge cycle, the irreversible migration of transition metal ions may trigger complex phase changes, thereby affecting the stability of the crystal structure. To overcome the above problems, doping a small amount of electrochemically active or inactive metal / non-metal elements (such as Ti, Mg, Al, Zn, Cu, F, and Li) into the transition metal oxide layer can share oxygen with transition metal ions and improve the interaction of TM-O bonds, thus stabilizing the structure.

[0009] Provided is a preparation method of a titanium-doped nickel-manganese-iron-based sodium-ion layered cathode material, comprising the following steps:

[0010] Step 1: Using tetrabutyl titanate as a titanium source, adding tetrabutyl titanate to deionized water, and then adding HNO3 for reaction to obtain a titanium nitrate solution;

[0011] Step 2: Mixing and stirring sodium nitrate, nickel nitrate, manganese nitrate, iron nitrate, the titanium nitrate solution, an organic fuel, and a complexing agent;

[0012] Step 3: Heating and evaporating the solvent to obtain a precursor of the titanium-doped nickel-manganese-iron-based sodium-ion layered cathode material;

[0013] Step 4: Grinding the precursor obtained in Step 3 and then annealing it in an air atmosphere;

[0014] Step 5: Cooling to obtain the titanium-doped nickel-manganese-iron-based sodium-ion layered cathode material.

[0015] Furthermore, the organic fuel is one or two of glycine, urea, citric acid, or alanine.

[0016] Furthermore, the complexing agent is citric acid or ethylenediaminetetraacetic acid.

[0017] Furthermore, the annealing temperature is 700 - 900 °C, and the annealing time is 1 - 10 h.

[0018] Furthermore, during the annealing process, the heating rate is 3 - 7 °C / min until the required annealing temperature is reached.

[0019] Furthermore, the molar ratio of sodium nitrate, nickel nitrate, manganese nitrate, iron nitrate, and tetrabutyl titanate is 1:0.4:0.3 - 0.4:0.2:0 - 0.1.

[0020] Furthermore, the molar ratio of sodium nitrate, nickel nitrate, manganese nitrate, iron nitrate, butyl titanate and organic fuel is 1:0.4:0.3-0.4:0.2:0-0.1:0.7-1.2.

[0021] Furthermore, the molar ratio of sodium nitrate, nickel nitrate, manganese nitrate, iron nitrate, butyl titanate and complexing agent is 1:0.4:0.3-0.4:0.2:0-0.1:0.1-0.5.

[0022] Furthermore, the molar ratio of sodium nitrate, nickel nitrate, manganese nitrate, iron nitrate, butyl titanate, glycine and citric acid is 1:0.4:0.37:0.2:0.03:1:0.3.

[0023] Provided is a titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material, which is prepared by the above-mentioned method for preparing a titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material.

[0024] The beneficial effects of the present invention are:

[0025] (1) The present invention uses a low-temperature combustion method to carry out in-situ titanium doping in air, which can accurately control the chemical dosage ratio of the raw material components and maintain uniform distribution; the process is simple to operate, has less impurities, and has a short preparation time and low energy consumption. The particle size of the obtained material can reach micrometer level, and has good prospects for industrial application;

[0026] (2) The method of the present invention obtains a titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material, by replacing the manganese element with titanium, thereby relatively reducing the Mn 3+ The concentration of 2.5 N·m can effectively inhibit the occurrence of the Jahn-Teller effect of the material, thereby improving the charge and discharge performance and cycle stability of the material;

[0027] (3) The titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material obtained by the preparation method of the present invention has an excellent hexagonal crystal structure, which enables it to have good electrochemical performance. When used as a sodium ion battery electrode, the battery's first 0.1C discharge capacity reaches 165.5 mAhg -1 , and after 200 1C long cycles, the capacity retention rate reaches 73.1%, which has good cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the process of the present invention;

[0029] Figure 2 This is an X-ray diffraction pattern of the titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material obtained in Example 1 of the present invention;

[0030] Figure 3This is a scanning electron microscope image of the titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material obtained in Example 1 of the present invention;

[0031] Figure 4 The energy dispersive X-ray spectrum of the titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material obtained in Example 1 of the present invention;

[0032] Figure 5 This is a transmission electron microscope image of the titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material obtained in Example 1 of the present invention;

[0033] Figure 6 This is a high-resolution transmission electron micrograph of the titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material obtained in Example 1 of the present invention;

[0034] Figure 7 This is the first charge and discharge diagram of the titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material at 0.1C obtained in Example 1 of the present invention;

[0035] Figure 8 This is the 1C long cycle diagram of the titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0036] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0037] like Figure 1 As shown, a method for preparing a titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material comprises the following steps:

[0038] Step 1: using butyl titanate as a titanium source, adding it into deionized water, and then adding HNO3 to react to obtain a titanium nitrate solution;

[0039] Step 2: Mix sodium nitrate, nickel nitrate, manganese nitrate, ferric nitrate, titanium nitrate solution, organic fuel, and complexing agent in the above solution; the molar ratio of sodium nitrate, nickel nitrate, manganese nitrate, ferric nitrate, butyl titanate, organic fuel and complexing agent is 1:0.4:0.3-0.4:0.2:0-0.1:0.7-1.2:0.1-0.5; the organic fuel is preferably glycine, and the complexing agent is preferably citric acid.

[0040] Step 3: heating and evaporating the solution, and obtaining a precursor of a titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material after combustion;

[0041] Step 4: Grind the precursor obtained in step 3 and place it in a tube furnace or a muffle furnace for annealing, heating it to 700-900° C. at 3-7° C. / min, and the annealing time is 1-10 hours, preferably 4-6 hours;

[0042] Step 5: After cooling, the titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material can be obtained.

[0043] Example 1

[0044] A method for preparing a titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material comprises the following steps:

[0045] Step 1: Use butyl titanate as a titanium source, add it into 20 mL of deionized water, and then add 5 mL of HNO3 to react to obtain a titanium nitrate solution;

[0046] Step 2: Sodium nitrate, nickel nitrate, manganese nitrate, iron nitrate, titanium nitrate solution, glycine and citric acid are placed in deionized water and mixed, and the mixture is placed in a 500 mL beaker, and stirred to form a transparent green solution, and the total solution is about 140 mL; the molar ratio of sodium nitrate, nickel nitrate, manganese nitrate, iron nitrate, butyl titanate, glycine and citric acid is 1:0.4:0.37:0.2:0.03:1:0.3;

[0047] Among them, the solutions that can also be selected or replaced in step 2 are specifically:

[0048] (1): The molar ratio of sodium nitrate, nickel nitrate, manganese nitrate, iron nitrate, butyl titanate, glycine and ethylenediaminetetraacetic acid is 1:0.4:0.39:0.2:0.01:1:0.3.

[0049] (2): The molar ratio of sodium nitrate, nickel nitrate, manganese nitrate, iron nitrate, butyl titanate, urea and citric acid is 1:0.4:0.35:0.2:0.05:1:0.3.

[0050] (3) The molar ratio of sodium nitrate, nickel nitrate, manganese nitrate, iron nitrate, butyl titanate, urea and ethylenediaminetetraacetic acid is 1:0.4:0.33:0.2:0.07:1:0.3.

[0051] Step 3: Place the beaker on an electronic multipurpose furnace with a total power of 1KW, heat and evaporate at a power of 800W, and boil the solution at about 100°C. After continuous boiling and evaporation, the solution turns into a brown paste-like substance, and continues to heat to finally obtain a black fluffy titanium-doped nickel-manganese-iron-based sodium ion layered cathode material precursor;

[0052] Step 4: The precursor obtained in step 3 is ground and then annealed in a tube furnace, with the temperature increased at 5°C / min to an annealing temperature of 900°C for 6 hours;

[0053] Step 5: After cooling, the titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material can be obtained.

[0054] See also Figure 2 , X-ray diffraction pattern (XRD pattern) of the titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material obtained in Example 1 of the present invention. Each diffraction peak in the spectrum highly corresponds to PDF#54-0887, and the sharp and strong diffraction peaks indicate that the sample has good crystallinity. Due to the solubility limitation of nickel in the O3 phase, a slight NiO impurity peak inevitably appears.

[0055] See also Figure 3 , is a scanning electron microscope image (SEM image) of the titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material obtained in Example 1 of the present invention. From the image, it can be clearly observed that the material is composed of micro-thin flaky particles with a relatively smooth surface.

[0056] See also Figure 4 , which is the energy dispersive X-ray spectrum (EDS diagram) of the titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material obtained in Example 1 of the present invention. The element mapping clearly shows that sodium (Na), nickel (Ni), manganese (Mn), iron (Fe) and titanium (Ti) are evenly distributed in the positive electrode material, indicating that titanium is successfully incorporated into the micron-sized nickel-manganese-iron-based sodium ion layered positive electrode material.

[0057] See also Figure 5 , is a transmission electron microscope image (TEM image) of the titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material obtained in Example 1 of the present invention, showing an excellent hexagonal crystal structure.

[0058] See also Figure 6 , which is a high-resolution transmission electron micrograph (HR-TEM) of the titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material obtained in Example 1 of the present invention. After being processed by lattice fringe measurement software (Digital Micrograph) and fast Fourier transform (FFT), the lattice spacing measured in the selected area is about 2.52Å, which is consistent with the (101) crystal plane of the layered hexagonal structure in the R3̅m space group.

[0059] See also Figure 7 , which is the 0.1C first charge and discharge curve of the titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material obtained in Example 1 of the present invention. The one with a starting voltage of 4.2V is the discharge curve, and the other is the charge curve. It can be seen that the material has a 0.1C first charge capacity of 179.3mAhg in the voltage range of 2-4.2V. -1 , discharge capacity is 165.5mAhg -1 , the first-cycle Coulomb efficiency is as high as 92.3%.

[0060] See also Figure 8 , is the 1C long cycle diagram of the titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material obtained in Example 1 of the present invention. The material still has 84.9 mAhg after 200 cycles. -1 , the capacity retention rate is 73.1%.

[0061] Compared with the existing preparation method, the titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material obtained by the present invention is prepared in an air atmosphere including the annealing process. The preparation method has the advantages of simple operation, low temperature, simple raw materials, short annealing time, and low energy consumption. At the same time, the particle size of the obtained material can reach the micron level. By replacing the manganese element with titanium, the Mn 3+ The concentration of 2.5-2.0% can effectively inhibit the occurrence of the Jahn-Teller effect of the material, thereby improving the charge and discharge performance and cycle stability of the material. When used as a sodium ion battery electrode, the battery 0.1C discharge capacity reaches 165.5 mAhg -1 , and the capacity retention rate reached 73.1% after 200 1C long cycles.

[0062] The above is only a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art shall not deviate from the spirit and scope of the present invention, and shall be within the scope of protection of the claims attached to the present invention.

Claims

1. A method for preparing a titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material, characterized in that: The following steps are involved: Step 1: Using butyl titanate as a titanium source, adding butyl titanate into deionized water, and then adding HNO3 to react to obtain a titanium nitrate solution; Step 2: Mix and stir sodium nitrate, nickel nitrate, manganese nitrate, iron nitrate, titanium nitrate solution, organic fuel and complexing agent; Step 3: heating and evaporating the solvent to obtain a precursor of a titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material; Step 4: Grinding the precursor obtained in step 3 and then annealing it in air atmosphere; Step 5: After cooling, a titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material is obtained.

2. The method for preparing a titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material according to claim 1, characterized in that: The organic fuel is one or two of glycine, urea, citric acid or alanine.

3. The method for preparing a titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material according to claim 1, characterized in that: The complexing agent is citric acid or ethylenediaminetetraacetic acid.

4. The method for preparing a titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material according to claim 1, characterized in that: The annealing temperature is 700-900° C., and the annealing time is 1-10 hours.

5. The method for preparing a titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material according to any one of claims 1 or 4, characterized in that: During the annealing process, the temperature is increased at a rate of 3 to 7°C / min until the desired annealing temperature is reached.

6. The method for preparing a titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material according to claim 1, characterized in that: The molar ratios of sodium nitrate, nickel nitrate, manganese nitrate, iron nitrate and butyl titanate are 1:0.4:0.3-0.4:0.2:0-0.1 respectively.

7. The method for preparing a titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material according to claim 1, characterized in that: The molar ratios of sodium nitrate, nickel nitrate, manganese nitrate, iron nitrate, butyl titanate and organic fuel are 1:0.4:0.3-0.4:0.2:0-0.1:0.7-1.2 respectively.

8. The method for preparing a titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material according to claim 1, characterized in that: The molar ratios of sodium nitrate, nickel nitrate, manganese nitrate, iron nitrate, butyl titanate and complexing agent are 1:0.4:0.3-0.4:0.2:0-0.1:0.1-0.5 respectively.

9. The method for preparing a titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material according to claim 1, characterized in that: The molar ratio of sodium nitrate, nickel nitrate, manganese nitrate, iron nitrate, butyl titanate, glycine and citric acid is 1:0.4:0.37:0.2:0.03:1:0.

3.

10. A titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material, characterized in that: The material is prepared by the method for preparing a titanium-doped nickel-manganese-iron-based sodium ion layered positive electrode material as described in any one of claims 1 to 9.

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