Na2Ti7O15-doped Na2Ti3O7 sodium titanate electrode material and its preparation and use

Abstract

The present invention is based on Na2Ti7O 15 This paper describes a doped sodium titanate electrode material, its preparation and use. The electrode material has a porous block structure stacked with nanorods and is synthesized by a simple solid-state method using proportional ball milling of precursors sodium carbonate and anatase titanium dioxide followed by microwave sintering in air. The resulting Na2Ti7O 15 The addition of Na increases the exposure of the (100) sodium storage crystal plane of Na2Ti3O7 sodium titanate and decreases the exposure of the (003) crystal plane, resulting in Na2Ti7O 15 has four TiO6 octahedra in one structural unit, providing more sodium storage sites and wider sodium ion diffusion channels, improving the specific capacity and rate performance of the material. 15 The TiO6 octahedra in the upper and lower layers are connected to each other, making the structure more stable during the sodium ion insertion / extraction process, thereby improving the long-term cycling stability of the material.

Description

[Technical Field]

[0001] The present invention relates to the field of sodium ion batteries, specifically to NaTiO 15 This paper relates to doped sodium titanate electrode material Na2Ti3O7 and its preparation method and use. [Background technology]

[0002] In recent years, lithium-ion batteries have achieved great success in the fields of portable electronic devices and electric vehicles, resulting in an increasing demand for lithium resources. With the price of lithium resources rising sharply, sodium-ion batteries are considered an ideal alternative to lithium-ion batteries due to their abundant resources, low cost, and high efficiency. Although numerous electrode materials have been researched for sodium-ion batteries, there is a serious shortage of low-voltage anode materials comparable to the graphite anodes of lithium-ion batteries. Titanium-based materials have abundant crystal forms, moderate Ti content, and high ionic strength. 3+ / Ti 4+ It has attracted widespread research interest as an anode material for sodium-ion batteries due to its low potential redox couple and low cost.

[0003] Among various titanium-based anode materials for sodium-ion batteries, Na2Ti3O7 has a unique titanium-oxygen octahedral zigzag layer structure, and an average voltage of 0.3V (vs. Na / Na + ) low sodium insertion platform, and 177mAhg -1 It is considered a very promising anode material due to its theoretical specific capacity of 1.5. Research has shown that the electronic conductivity and sodium ion diffusion coefficient of Na2Ti3O7 are not high, and to satisfy the minimum energy principle, sodium ions preferentially move along these zigzag layers rather than through them. Therefore, the number and length of the sodium ion transport channels and the stability of the channels are important factors limiting the movement and insertion / extraction of sodium ions in Na2Ti3O7.

[0004] In recent years, nano-sizing Na2Ti3O7 and doping it with other elements has become the mainstream strategy to shorten the migration path of sodium ions, widen the ion diffusion channels, and stabilize the interlayer structure during charging and discharging. However, the nano-sizing manufacturing methods are often costly and have low yields, making them very difficult to implement in industrial production. Simple ion doping cannot fully alleviate the structural collapse problem caused by structural slippage and expansion of the layered material during charging and discharging.

[0005] The patent application is for potassium-doped sodium titanate electrode material and its manufacturing method and use (202211220673.9), which involves doping sodium titanate electrode material with potassium ions. Due to the presence of potassium ions, a pure potassium-doped Na2Ti3O7 crystalline phase is obtained after sintering, and some of the sodium ions in the Na2Ti3O7 crystalline phase are replaced by potassium ions, which is a method of using ion doping to shorten the migration path of sodium ions.

[0006] This application adopts a completely different doping direction and uses crystalline phase doping to produce Na2Ti7O 15 The Na2Ti3O7 crystalline phase is doped with ZnO to increase the number of sodium ion storage sites, widen the diffusion channels for sodium ions, and stabilize the structural changes during charging and discharging. This strategy has not been reported before. In this strategy, a microwave-assisted solid-state method is used to synthesize the material. The manufacturing method is simple, the yield is high, and industrial production is easy. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] 202211220673.9 Summary of the Invention [Problem to be solved by the invention]

[0008] In response to the above problems in the prior art, the present invention provides Na2Ti7O 15 Provided are doped sodium titanate (Na2Ti3O7) electrode materials, their preparation methods and uses. [Means for solving the problem]

[0009] To achieve the above object, the present invention provides the following technical solutions:

[0010] Na2Ti7O 15 Doped Na2Ti3O7 sodium titanate electrode material, its structure is a porous block structure stacked with nanorods, with a diameter of 100-400nm.

[0011] Preferably, Na2Ti7O 15 The crystalline phase is regularly doped into the Na2Ti3O7 crystalline phase.

[0012] Microwave-assisted Na2Ti7O 15 Doped Na2Ti3O7 sodium titanate anode material produces a preferred orientation, increasing the exposure of the (100) crystal plane while decreasing the exposure of the (003) crystal plane. 15 The presence of can not only increase the sodium storage sites of the material but also widen the diffusion channels for sodium ions and stabilize the interlayer structure during charging and discharging.

[0013] The present invention also relates to the above Na2Ti7O 15 To provide a method for producing doped sodium titanate electrode material, (1) mixing sodium carbonate and anatase phase titanium dioxide by ball milling to obtain a homogeneously mixed precursor mixture; The homogeneously mixed precursor mixture was placed in a microwave tube furnace and fired in an air atmosphere to obtain Na2Ti7O 15 (2) obtaining a doped Na2Ti3O7 sodium titanate electrode material.

[0014] Preferably, the molar ratio of sodium carbonate to titanium dioxide of anatase phase is (1.5 to 1.99):6.

[0015] Preferably, the temperature rise rate in the sintering in a microwave tubular furnace is 5 to 10° C. / min, the sintering temperature is 800 to 1100° C., and the sintering time is 20 to 60 minutes.

[0016] The present invention also provides the above-mentioned Na2Ti7O in a sodium ion battery. 15 The present invention provides a doped sodium titanate electrode material, Na2Ti3O7. [Effects of the Invention]

[0017] The beneficial effects of the present invention are as follows: (1) The precursors of the electrode materials are low-cost sodium carbonate and titanium dioxide. (2) The manufacturing method of the material is simple. It can be synthesized by solid-phase synthesis, ball milling the precursor in proportion, and then microwave sintering in air. By reducing the proportion of sodium carbonate, a phase-doped sodium titanate electrode material can be obtained. (3)Na2Ti7O 15 When doped Na2Ti3O7 sodium titanate is used as the anode material in sodium-ion batteries, Na2Ti7O 15 By adding Na2Ti3O7 sodium titanate, the exposure of the (100) sodium storage crystal plane increases and the exposure of the (003) crystal plane decreases. 15 Since Na2Ti3O7 has four TiO6 octahedra in one structural unit, it has more sodium storage sites and wider sodium ion diffusion channels compared to Na2Ti3O7, which has three TiO6 octahedra in one structural unit, which improved the specific capacity and rate performance of the material. In contrast to the Na2Ti3O7 layered material, which has separate upper and lower TiO6 octahedra, Na2Ti7O 15 The TiO6 octahedra in the upper and lower layers are connected to each other, making the structure more stable during the sodium ion insertion / extraction process, thereby improving the long-term cycling stability of the material. [Brief explanation of the drawings]

[0018] [Figure 1] 1 shows the X-ray diffraction patterns of the Na2Ti7O15-doped Na2Ti3O7 sodium titanate electrode material 1.9Na2Ti3O7&Na2Ti7O15 prepared in Example 5 and the Na2Ti3O7 sodium titanate electrode material prepared in Comparative Example 1. [Figure 2] FIG. 1 is a field emission scanning electron microscope image of the Na2Ti7O15-doped Na2Ti3O7 sodium titanate electrode material 1.9Na2Ti3O7&Na2Ti7O15 prepared in Example 5. [Figure 3] FIG. 10 is a high-angle annular night-vision baseball-surface aberration-corrected scanning transmission electron microscope image of the Na2Ti7O15-doped Na2Ti3O7 sodium titanate electrode material 1.9Na2Ti3O7&Na2Ti7O15 prepared in Example 5. [Figure 4] FIG. 2 is a diagram showing the initial charge-discharge voltage and specific capacity of the Na2Ti7O15-doped Na2Ti3O7 sodium titanate electrode material 1.5Na2Ti3O7&Na2Ti7O15 prepared in Example 1. [Figure 5] FIG. 1 is a diagram showing the initial charge-discharge voltage and specific capacity of the Na2Ti7O15-doped Na2Ti3O7 sodium titanate electrode material 1.6Na2Ti3O7&Na2Ti7O15 prepared in Example 2. [Figure 6] FIG. 1 is a diagram showing the initial charge / discharge voltage and specific capacity of the Na2Ti7O15-doped Na2Ti3O7 sodium titanate electrode material 1.7Na2Ti3O7&Na2Ti7O15 prepared in Example 3. [Figure 7] FIG. 1 is a diagram showing the initial charge-discharge voltage and specific capacity of the Na2Ti7O15-doped Na2Ti3O7 sodium titanate electrode material 1.8Na2Ti3O7&Na2Ti7O15 prepared in Example 4. [Figure 8] FIG. 10 is a diagram showing the initial charge-discharge voltage and specific capacity of the Na2Ti7O15-doped Na2Ti3O7 sodium titanate electrode material 1.9Na2Ti3O7&Na2Ti7O15 prepared in Example 5. [Figure 9]FIG. 10 is a graph showing the initial charge / discharge voltage and specific capacity of the Na2Ti7O15-doped Na2Ti3O7 sodium titanate electrode material 1.99Na2Ti3O7&Na2Ti7O15 prepared in Example 6. [Figure 10] FIG. 1 is a graph showing the initial charge / discharge voltage and specific capacity of the Na2Ti3O7 sodium titanate electrode material produced in Comparative Example 1. [Figure 11] FIG. 1 is a graph showing the rate performance of the Na2Ti7O15-doped Na2Ti3O7 sodium titanate electrode material 1.9Na2Ti3O7&Na2Ti7O15 prepared in Example 5 and the Na2Ti3O7 sodium titanate electrode material prepared in Comparative Example 1 (circles: Example 5, triangles: Comparative Example 1). DETAILED DESCRIPTION OF THE INVENTION

[0019] In order to enable those skilled in the art to better understand the technical solution of the present invention, the following provides a clear and complete description of the technical solution of the present invention with reference to the drawings of the present invention, and any other similar embodiments obtained by those skilled in the art based on the embodiments in this application without any creative efforts shall fall within the protection scope of this application.

[0020] Example 1: In this example, Na2Ti7O 15 The method for producing doped Na2Ti3O7 sodium titanate electrode material involves placing 0.795 g of sodium carbonate and 2.396 g of anatase titanium dioxide (the molar ratio of sodium carbonate to anatase titanium dioxide is 1.5:6) in a high-energy ball mill tank and ball milling for 1 hour at room temperature to obtain a homogeneously mixed precursor. The precursor is then placed in a microwave tube furnace for high-temperature calcination, specifically, the heating rate is set to 5 degrees Celsius / min, and calcined at 800 degrees Celsius in an air atmosphere for 60 minutes to obtain Na2Ti7O 15 Doped Na2Ti3O7 sodium titanate electrode material (1.5Na2Ti3O7 & Na2Ti7O 15 ) is obtained.

[0021] Example 2: In this example, Na2Ti7O 15 The method for producing doped Na2Ti3O7 sodium titanate electrode material involves placing 0.848g of sodium carbonate and 2.396g of anatase titanium dioxide (the molar ratio of sodium carbonate to anatase titanium dioxide is 1.6:6) in a high-energy ball mill tank and ball milling for 1 hour at room temperature to obtain a homogeneously mixed precursor. The precursor is then placed in a microwave tube furnace for high-temperature calcination, specifically, the heating rate is set to 6 degrees Celsius / min, and calcined at 850 degrees Celsius in an air atmosphere for 50 minutes to obtain Na2Ti7O 15 Doped Na2Ti3O7 sodium titanate electrode material (1.6Na2Ti3O7 & Na2Ti7O 15 ) is obtained.

[0022] Example 3: In this example, Na2Ti7O 15 The method for producing doped Na2Ti3O7 sodium titanate electrode material involves placing 0.901g of sodium carbonate and 2.396g of anatase titanium dioxide (the molar ratio of sodium carbonate to anatase titanium dioxide is 1.7:6) in a high-energy ball mill tank and ball milling for 1 hour at room temperature to obtain a homogeneously mixed precursor. The precursor is then placed in a microwave tube furnace for high-temperature calcination, specifically, the heating rate is set to 7°C / min, and calcined at 900°C in air for 40 minutes to obtain Na2Ti7O 15 Doped Na2Ti3O7 sodium titanate electrode material (1.7Na2Ti3O7 & Na2Ti7O 15 ) is obtained.

[0023] Example 4: In this example, Na2Ti7O 15The method for producing doped Na2Ti3O7 sodium titanate electrode material involves placing 0.954 g of sodium carbonate and 2.396 g of anatase titanium dioxide (the molar ratio of sodium carbonate to anatase titanium dioxide is 1.8:6) in a high-energy ball mill tank and ball milling for 1 hour at room temperature to obtain a homogeneously mixed precursor. The precursor is then placed in a microwave tube furnace for high-temperature calcination, specifically, the heating rate is set to 8 degrees Celsius / min, and calcined at 1000 degrees Celsius in an air atmosphere for 30 minutes to obtain Na2Ti7O 15 Doped Na2Ti3O7 sodium titanate electrode material (1.8Na2Ti3O7 & Na2Ti7O 15 ) is obtained.

[0024] Example 5: In this example, Na2Ti7O 15 The method for producing doped Na2Ti3O7 sodium titanate electrode material involves placing 1.007 g of sodium carbonate and 2.396 g of anatase titanium dioxide (the molar ratio of sodium carbonate to anatase titanium dioxide is 1.9:6) in a high-energy ball mill tank and ball milling for 1 hour at room temperature to obtain a homogeneously mixed precursor. The precursor is then placed in a microwave tube furnace for high-temperature calcination, specifically, the heating rate is set to 10 degrees Celsius / min, and calcined at 850 degrees Celsius in an air atmosphere for 20 minutes to obtain Na2Ti7O 15 Doped Na2Ti3O7 sodium titanate electrode material (1.9Na2Ti3O7 & Na2Ti7O 15 ) is obtained.

[0025] Na2Ti7O produced in this example 15 Doped Na2Ti3O7 Sodium Titanate Electrode Material 1.9Na2Ti3O7&Na2Ti7O 15 The structure of this material was characterized using an X-ray diffractometer, and the results are shown in Figure 1. As can be seen from Figure 1, the diffraction peaks of the produced material are Na2Ti3O7 and Na2Ti7O 15 In this example, the crystal phase is Na2Ti7O 15Doped Na2Ti3O7 sodium titanate material (1.9Na2Ti3O7 & Na2Ti7O 15 ) was successfully produced. Figure 1 shows that the diffraction intensity of the 10.527° (100) crystal plane is increased, and the diffraction intensity of the 29.929° (003) crystal plane is relatively decreased. 15 The addition of α-glucan causes a preferred orientation of the crystals, increasing the exposure of the (100) crystal plane and relatively decreasing the exposure of the (003) crystal plane, which increases and shortens the diffusion channel for sodium ions, favoring the diffusion and storage of sodium ions.

[0026] 1.9Na2Ti3O7&Na2Ti7O 15 The morphology of the material was characterized by field emission scanning electron microscopy (FE-SEM), and the results are shown in Figure 2. As can be seen from Figure 2, the fabricated material has a porous block structure stacked with nanorods, and the diameter of the rods is 100–400 nm.

[0027] 1.9Na2Ti3O7&Na2Ti7O 15 The material was characterized by high-angle annular dark field aberration-corrected scanning transmission electron microscope (HAADF-STEM), and the results are shown in Figure 3. As can be seen from Figure 3, the prepared Na2Ti3O7 crystalline phase contained Na2Ti7O 15 The crystal phase of Na2Ti7O appears regularly. 15 This indicates that Na2Ti3O7 is successfully doped into the Na2Ti3O7 crystalline phase. 15 Since Na2Ti3O7 has four TiO6 octahedra in one structural unit, it has more sodium storage sites and wider sodium ion diffusion channels compared to Na2Ti3O7, which has three TiO6 octahedra in one structural unit, which improved the specific capacity and rate performance of the material. In contrast to the Na2Ti3O7 layered material, which has separate upper and lower TiO6 octahedra, Na2Ti7O 15 The TiO6 octahedra in the upper and lower layers are connected to each other, making the structure more stable during the sodium ion insertion / extraction process, thereby improving the long-term cycling stability of the material.

[0028] Example 6: In this example, Na2Ti7O 15 The method for producing doped Na2Ti3O7 sodium titanate electrode material involves placing 1.054 g of sodium carbonate and 2.396 g of anatase titanium dioxide (the molar ratio of sodium carbonate to anatase titanium dioxide is 1.99:6) in a high-energy ball mill tank and ball milling for 1 hour at room temperature to obtain a homogeneously mixed precursor, which is then placed in a microwave tube furnace for high-temperature calcination, specifically, at a heating rate of 10 degrees Celsius / min and calcined at 1100 degrees Celsius in an air atmosphere for 20 minutes to obtain Na2Ti7O 15 Doped Na2Ti3O7 sodium titanate electrode material (1.99Na2Ti3O7 & Na2Ti7O 15 ) is obtained.

[0029] Comparative Example 1: This example relates to a method for producing pure-phase Na2Ti3O7 sodium titanate electrode material. The steps are as follows: 1.060 g of sodium carbonate and 2.396 g of anatase titanium dioxide are placed in a high-energy ball mill tank and ball milled at room temperature for 1 hour to obtain a homogeneously mixed precursor; the precursor is then placed in a microwave tube furnace for high-temperature calcination, specifically, the heating rate is set to 10°C / min, and calcined at 850°C in an air atmosphere for 20 minutes to obtain sodium titanate electrode material (Na2Ti3O7).

[0030] The structure of the Na2Ti3O7 sodium titanate electrode material prepared in this example was characterized using an X-ray diffractometer, and the results are shown in Figure 1. As can be seen from Figure 1, the diffraction peaks of the prepared material match the crystalline phase represented by the DFT standard card for Na2Ti3O7, indicating that this example successfully produced a pure phase Na2Ti3O7 sodium titanate material. 15The specific steps of the electrochemical performance test experiment of the doped Na2Ti3O7 sodium titanate electrode material and Na2Ti3O7 sodium titanate electrode material are as follows: Na2Ti7O obtained in Examples 1 to 6 15 The doped Na2Ti3O7 sodium titanate material and the Na2Ti3O7 sodium titanate electrode material obtained in Comparative Example 1 were used as the negative electrode of a sodium ion battery, metallic sodium as the auxiliary electrode, glass fiber as the diaphragm, and sodium hexafluorophosphate (NaPF6) as the electrolyte. The battery was sealed and packaged in a CR2032 button-type battery shell in an argon atmosphere glove box to produce Na2Ti7O 15 Doped Na2Ti3O7 sodium titanate electrode material half-cells and Na2Ti3O7 sodium titanate electrode material half-cells were obtained. Electrochemical performance tests were conducted at a rate of 0.1 C (1 C = 177 mAg-1) and a voltage range of 0.01 to 2.5 V, and the resulting specific capacities are shown in Table 1. Electrochemical rate performance tests were also conducted at rates of 0.1, 0.2, 0.5, 1, 2, 5, 10, and 20 C and within a voltage range of 0.01 to 2.5 V, and the resulting rate performance is shown in Figure 11.

[0031] Table 1 shows the Na2Ti7O 15 The charge specific capacity (mAhg) of the doped Na2Ti3O7 sodium titanate electrode material and the Na2Ti3O7 sodium titanate electrode material of Comparative Example 1 -1 ) [Table 1]

[0032] Furthermore, although this specification is described according to the embodiments, each embodiment does not include only one independent technical solution, and the description method of the specification is for clarity only, and those skilled in the art should understand the specification as a whole. The technical solutions of each example can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. Na ２ Ti ７ O １５ Doped Na ２ Ti ３ O ７ A sodium titanate electrode material, characterized in that it has a porous block structure stacked with nanorods and has a diameter of 100 to 400 nm. ２ Ti ７ O １５ Doped Na ２ Ti ３ O ７ Sodium titanate electrode material.

2. Na ２ Ti ７ O １５ The crystalline phase is Na ２ Ti ３ O ７ The Na as claimed in claim 1, characterized in that it is regularly doped in a crystalline phase. ２ Ti ７ O １５ Doped Na ２ Ti ３ O ７ Sodium titanate electrode material.

3. Na according to claim 1 or 2 ２ Ti ７ O １５ Doped Na ２ Ti ３ O ７ A method for producing a sodium titanate electrode material, comprising: Step (1) mixing sodium carbonate and anatase phase titanium dioxide by ball milling to obtain a homogeneously mixed precursor mixture; The homogeneously mixed precursor mixture was placed in a microwave tube furnace and fired in an air atmosphere to obtain Na ２ Ti ７ O １５ Doped Na ２ Ti ３ O ７ (2) obtaining a sodium titanate electrode material; ２ Ti ７ O １５ Doped Na ２ Ti ３ O ７ Method for producing sodium titanate electrode material.

4. 4. The sodium carbonate of claim 3, wherein the molar ratio of the sodium carbonate to the anatase phase titanium dioxide is (1.50-1.99):

6. ２ Ti ７ O １５ Doped Na ２ Ti ３ O ７ Method for producing sodium titanate electrode material.

5. The method according to claim 3, characterized in that the heating rate in the microwave tubular furnace is 5 to 10°C / min, the firing temperature is 800 to 1100°C, and the firing time is 20 to 60 minutes. ２ Ti ７ O １５ Doped Na ２ Ti ３ O ７ Method for producing sodium titanate electrode material.

6. Na according to claim 1 or 2 ２ Ti ７ O １５ Doped Na ２ Ti ３ O ７ Use of sodium titanate electrode material in sodium-ion batteries.

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