Preparation method and application of inorganic interface-coated niobium-tungsten oxide heterojunction material

Abstract

A method for preparing an inorganically interface-coated niobium-tungsten oxide heterojunction material and its application are disclosed, belonging to the field of lithium-ion batteries. The preparation method includes the following steps: Step 1, adding a niobium source and a tungsten source to anhydrous ethanol, mixing them evenly, and drying them to obtain a niobium-tungsten oxide precursor; Step 2, transferring the niobium-tungsten oxide precursor to a tube furnace and sintering it at a gradient temperature of 700-1300℃, introducing the same or different gases at each temperature gradient to obtain an inorganically interface-coated niobium-tungsten oxide heterojunction material; the gas is PH3, H2S, or NH3. The heterostructure prepared by this invention improves the ionic conductivity of niobium-based oxides, and the inorganic coating improves the electronic conductivity of the niobium-based oxide heterojunction material, significantly improving rate performance, and is applicable to the field of high-power lithium-ion batteries.

Description

Technical Field

[0001] This invention belongs to the field of secondary lithium-ion battery technology, specifically relating to a method for preparing an inorganic interface-coated niobium tungsten oxide heterojunction material and its application in lithium-ion batteries. Background Technology

[0002] Lithium-ion batteries (LIBs) have become the preferred power source for portable electronic devices and electric vehicles due to their high energy density and long cycle life. Graphite, on the other hand, is valued for its low cost and high specific capacity (372 mA hg). -1 Graphite has become a commonly used negative electrode material in commercially available secondary lithium-ion batteries. However, graphite exhibits a relatively low operating voltage (0.1 V vs Li). + Lithium spinel titanate (Li₂ / Li₃) leads to permanent lithium depletion and is prone to forming lithium dendrites on the graphite surface, causing safety issues. Among anode intercalation materials, Li₂ / Li₃ has a higher operating voltage (1.55 V vs Li₂). + Lithium spinel titanate (Li / S) ensures safety and has a long cycle life. However, its theoretical specific capacity is relatively low (only 175 mA hg). -1 Its poor conductivity hinders its practical application.

[0003] In recent years, niobium-based oxides have attracted considerable attention as high-power anode materials for lithium-ion batteries and have the potential to replace lithium-titanium spinel. As a typical intercalated anode material, the excellent electrochemical performance of niobium-tungsten oxide mainly stems from its unique structure, where niobium (Nb) and tungsten (W) atoms are located at the center of NbO6 and WO6 octahedra, respectively, existing in a disordered arrangement. The NbO6 and WO6 octahedra are connected by edges and vertices, forming open tunnel-like gaps that can accommodate lithium-ion transport. Lithium-ion insertion and extraction are relatively easy, thus exhibiting excellent rate performance. Niobium-tungsten oxide not only possesses the advantages of conventional lithium titanate materials in terms of cycle stability and long lifespan, but also exhibits excellent rate performance, with an operating potential similar to lithium titanate (1.6 V vs Li). + Niobium-tungsten oxide (NiTO) can effectively prevent the formation of lithium dendrites and the reductive decomposition of the electrolyte. Compared with traditional batteries, its safety performance is greatly improved. However, NiTO also has some problems; its electronic and ionic conductivity is low. Therefore, there is an urgent need to invent a method that can simultaneously improve the electronic and ionic conductivity of the material. Summary of the Invention

[0004] Based on the above technical background, this invention provides a method for preparing an inorganic interface-coated niobium tungsten oxide heterojunction material and its application in lithium-ion batteries. By using gradient temperature control combined with in-situ gas introduction to modify the niobium tungsten oxide material, a one-step solid-phase method can be used to prepare an inorganically coated niobium tungsten oxide heterojunction. The heterostructure improves the ionic conductivity of the niobium tungsten oxide, and the inorganic coating improves the electronic conductivity of the niobium tungsten oxide heterojunction material, significantly improving rate performance for use in high-power lithium-ion batteries.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for preparing an inorganically interface-coated niobium-tungsten oxide heterojunction material includes the following steps:

[0007] Step 1: Add the niobium source and tungsten source to a beaker containing anhydrous ethanol and stir for 30 minutes to ensure uniform mixing. Then, transfer the resulting suspension to a forced-air drying oven and heat at 70°C for 24 hours to dry it and obtain the niobium tungsten oxide precursor. Preferably, the volume of anhydrous ethanol is 200 ml.

[0008] Step 2: Transfer the niobium tungsten oxide precursor prepared in Step 1 to a tube furnace and perform gradient sintering at 700-1300℃. The same or different gases are introduced at each temperature gradient to obtain an inorganic interface-coated niobium tungsten oxide heterojunction material; the gas is PH3, H2S, or NH3. Preferably, the gas flow rate is 50-100 ml / min.

[0009] Furthermore, in step one, the molar ratio of the niobium source and the tungsten source is 16:5, 7:3, 6:1, or 1:1.

[0010] Furthermore, in step one, the niobium source is one or more of Nb2O5, NbO, NbO2, and Nb powder; the tungsten source is one or more of WO3, WO2, and W powder.

[0011] Furthermore, in step two, the total time for gradient sintering is 12-24 hours.

[0012] Furthermore, in step two, the niobium tungsten oxide precursor is transferred to a tube furnace and sintered first at 700°C for 12 hours, then at 1200°C for 12 hours. At the sintering temperature of 700°C, PH3, H2S, or NH3 gas is introduced to generate niobium tungsten oxide heterojunctions (i.e., phosphide / niobium tungsten oxide heterojunctions, sulfide / niobium tungsten oxide heterojunctions, and nitride / niobium tungsten oxide heterojunctions). At the sintering temperature of 1200°C, PH3, H2S, or NH3 gas is introduced to form an inorganic protective layer (phosphide inorganic layer, sulfide inorganic layer, and nitride inorganic layer) on the surface of the generated niobium tungsten oxide heterojunction crystals.

[0013] Furthermore, in step two, during the gradient sintering process, the heating rate for each heating zone is 1-5℃ / min. Preferably, the heating rate is 1℃ / min, 2℃ / min, or 5℃ / min.

[0014] Furthermore, in step two, if there are two temperature gradients during gradient sintering, the order of introducing the gas is PH3 followed by PH3, PH3 followed by H2S, PH3 followed by NH3, H2S followed by PH3, H2S followed by H2S, H2S followed by NH3, NH3 followed by PH3, NH3 followed by H2S, or NH3 followed by NH3.

[0015] Preferably, the gas introduced during calcination at 700 °C for 12 hours is PH3, and the gas introduced during calcination at 1200 °C for 12 hours is PH3.

[0016] Preferably, the gas introduced during calcination at 700 °C for 12 hours is PH3, and the gas introduced during calcination at 1200 °C for 12 hours is H2S;

[0017] Preferably, the gas introduced during calcination at 700 °C for 12 hours is H2S, and the gas introduced during calcination at 1200 °C for 12 hours is PH3.

[0018] Preferably, the gas introduced during calcination at 700 °C for 12 hours is H2S, and the gas introduced during calcination at 1200 °C for 12 hours is H2S.

[0019] Preferably, the gas introduced during calcination at 700 °C for 12 hours is H2S, and the gas introduced during calcination at 1200 °C for 12 hours is NH3;

[0020] Preferably, the gas introduced during calcination at 700 °C for 12 hours is NH3, and the gas introduced during calcination at 1200 °C for 12 hours is PH3.

[0021] Preferably, the gas introduced during calcination at 700 °C for 12 hours is NH3, and the gas introduced during calcination at 1200 °C for 12 hours is H2S;

[0022] Preferably, the gas introduced during calcination at 700 °C for 12 hours is NH3, and the gas introduced during calcination at 1200 °C for 12 hours is NH3.

[0023] Furthermore, in step two, before the material is sintered, Ar gas or other inert gases are introduced into the tube furnace at room temperature for 1-3 hours, with the inert gas flow rate being 50-100 ml / min.

[0024] An application of the inorganic interface-coated niobium tungsten oxide heterojunction material prepared by the aforementioned preparation method, wherein the inorganic interface-coated niobium tungsten oxide heterojunction material is used as a negative electrode material for lithium-ion batteries.

[0025] The inorganic interface-coated niobium tungsten oxide heterojunction material is dispersed in a solvent with a conductive agent and a binder in a certain mass ratio to obtain a negative electrode slurry. The negative electrode slurry is coated on a negative electrode current collector, and after drying, rolling and punching, a negative electrode sheet is obtained, which is then assembled into a coin cell.

[0026] The binder is polyvinylidene fluoride (PVDF), the conductive agent is acetylene black, and the solvent is N-methylpyrrolidone (NMP). The mass ratio of the inorganic interface-coated niobium-tungsten oxide heterojunction material, conductive agent, and binder is 80%:10%:10%.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] In this invention, a one-step method is used to prepare niobium tungsten oxide heterojunction materials with inorganic interface coating. The heterostructure improves the ionic conductivity of niobium tungsten oxide, and the inorganic coating improves the electronic conductivity of the niobium tungsten oxide heterojunction material, thus significantly improving the rate performance for use in high-power lithium-ion batteries. Attached Figure Description

[0029] Figure 1 SEM image of the inorganic interface-coated niobium-tungsten oxide heterojunction material prepared in Example 1;

[0030] Figure 2 XRD pattern of the inorganic interface-coated niobium-tungsten oxide heterojunction material prepared in Example 1;

[0031] Figure 3 Cycling diagrams at 1C are shown for the inorganic interface-coated niobium-tungsten oxide heterojunction material prepared in Example 1 and the sample prepared in Comparative Example 1.

[0032] Figure 4 Cycling diagrams at 10°C for the inorganic interface-coated niobium-tungsten oxide heterojunction material prepared in Example 1 and the sample prepared in Comparative Example 1. Detailed Implementation

[0033] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only some embodiments of the invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0034] Comparative Example 1:

[0035] 200 mL of anhydrous ethanol was added to a beaker. Next, niobium pentoxide and tungsten trioxide were added in a molar ratio of 16:5 under stirring, and the mixture was continuously stirred magnetically for 30 minutes to ensure thorough mixing. The resulting suspension was then transferred to a forced-air oven and heated at 70 °C for 24 h to prepare a niobium-tungsten oxide precursor. The prepared niobium-tungsten oxide precursor was then transferred to a tube furnace for sintering. Calcination was performed at 700 °C for 12 h at a heating rate of 5 °C / min, followed by calcination at 1200 °C for 12 h at a heating rate of 5 °C / min to obtain the niobium-tungsten oxide material.

[0036] Example 1:

[0037] A method for preparing an inorganically interface-coated niobium-tungsten oxide heterojunction material and its application in lithium-ion batteries includes the following methods:

[0038] 200 mL of anhydrous ethanol was added to a beaker. Next, niobium pentoxide and tungsten trioxide were added in a molar ratio of 16:5 under stirring conditions, and the mixture was continuously stirred magnetically for 30 minutes to ensure thorough mixing. Then, the resulting suspension was transferred to a forced-air oven and heated at 70 °C for 24 h to prepare the niobium-tungsten oxide precursor.

[0039] The prepared niobium tungsten oxide precursor was transferred to a tube furnace for sintering. First, Ar gas was introduced into the tube furnace at 25°C at a flow rate of 50-100 ml / min. Then, it was calcined at 700°C for 12 hours with a heating rate of 5°C / min, while simultaneously introducing PH3 gas at a flow rate of 50-100 ml / min, thus obtaining a niobium tungsten oxide heterojunction (NWO / NWP). Next, it was calcined at 1200°C for 12 hours with a heating rate of 5°C / min, while simultaneously introducing NH3 gas at a flow rate of 50-100 ml / min, yielding a phosphide / niobium tungsten oxide heterojunction (NWO / NWP) material with a nitride inorganic layer coating. Figure 1 The image shows a SEM image of the niobium-tungsten oxide heterojunction material coated with a nitride inorganic layer prepared in Example 1. The nitride inorganic layer can be clearly observed. Figure 2 The XRD pattern of the niobium tungsten oxide heterojunction material coated with a nitrided inorganic layer prepared in Example 1 shows the characteristic peaks of NWO and WP.

[0040] The obtained nitride inorganic layer-coated phosphide / niobium tungsten oxide heterojunction (NWO / NWP) material is dispersed in a solvent with a conductive agent and a binder in a certain mass ratio to obtain a negative electrode slurry. The negative electrode slurry is coated on a negative electrode current collector, and after drying, rolling and punching, a negative electrode sheet is obtained, and then a coin cell is assembled. Figure 3The images show the cycling conditions at 1C for the niobium-tungsten oxide heterojunction material coated with an inorganic nitride layer prepared in Example 1 and the sample prepared in Comparative Example 1. Figure 4 The comparison shows the cycling curves of the niobium tungsten oxide heterojunction material coated with a nitrided inorganic layer prepared in Example 1 and the sample prepared in Comparative Example 1 at 10C. It can be seen that the method of the present invention can improve the electrochemical performance of niobium tungsten oxide.

[0041] The nitride inorganic layer-coated phosphide / niobium tungsten oxide heterojunction (NWO / NWP) material obtained in this embodiment is used as a lithium-ion battery anode material.

[0042] Example 2

[0043] The difference between this embodiment and Embodiment 1 is that the gas introduced during calcination at 700°C for 12 hours is PH3, and the gas introduced during calcination at 1200°C for 12 hours is also PH3, thereby obtaining a phosphide / niobium tungsten oxide heterojunction (NWO / NWP) material coated with a phosphated inorganic layer. All other aspects are the same as in Embodiment 1.

[0044] Example 3

[0045] The difference between this embodiment and Embodiment 1 is that the gas introduced during calcination at 700°C for 12 hours is PH3, and the gas introduced during calcination at 1200°C for 12 hours is H2S, thereby obtaining a phosphide / niobium tungsten oxide heterojunction (NWO / NWP) material coated with a sulfurized inorganic layer. All other aspects are the same as in Embodiment 1.

[0046] Example 4

[0047] The difference between this embodiment and Embodiment 1 is that the gas introduced during calcination at 700°C for 12 hours is H2S, and the gas introduced during calcination at 1200°C for 12 hours is PH3, thereby obtaining a sulfide / niobium tungsten oxide heterojunction (NWO / NWS) material coated with a phosphating inorganic layer. All other aspects are the same as in Embodiment 1.

[0048] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing an inorganically interface-coated niobium-tungsten oxide heterojunction material, characterized in that, Includes the following steps: Step 1: Add niobium source and tungsten source to anhydrous ethanol, mix evenly, and dry to obtain niobium tungsten oxide precursor; Step 2: Transfer the niobium tungsten oxide precursor to a tube furnace and sinter it at a gradient temperature of 700~1300℃. At each temperature gradient, the same or different gases are introduced to obtain niobium tungsten oxide heterojunction materials with inorganic interfaces. The gases are PH3, H2S or NH3. Before sintering the material, an inert gas is introduced into the tube furnace and kept for 1~3 hours at a gas flow rate of 50~100 ml / min.

2. The preparation method according to claim 1, characterized in that: In step one, the molar ratio of the niobium source and the tungsten source is 16:5, 7:3, 6:1 or 1:

1.

3. The preparation method according to claim 1, characterized in that: In step one, the niobium source is one or more of Nb2O5, NbO, NbO2, and Nb powder; the tungsten source is one or more of WO3, WO2, and W powder.

4. The preparation method according to claim 1, characterized in that: In step two, the total time for gradient sintering is 24~48h.

5. The preparation method according to claim 1, characterized in that: In step two, the niobium tungsten oxide precursor is transferred to a tube furnace and sintered at 700°C for 12 hours, and then sintered at 1200°C for 12 hours.

6. The preparation method according to claim 1, characterized in that: In step two, during the gradient sintering process, the heating rate of each heating zone is 1~5℃ / min.

7. The preparation method according to claim 1, characterized in that: In step two, during gradient sintering, if there are two temperature gradients, the gas introduction sequence is PH3 followed by PH3, PH3 followed by H2S, PH3 followed by NH3, H2S followed by PH3, H2S followed by H2S, H2S followed by NH3, NH3 followed by PH3, NH3 followed by H2S, and NH3 followed by NH3, with a gas flow rate of 50~100 ml / min.

8. The application of an inorganic interface-coated niobium-tungsten oxide heterojunction material prepared by the preparation method according to any one of claims 1 to 7, characterized in that: The inorganic interface-coated niobium-tungsten oxide heterojunction material is used as the negative electrode material for lithium-ion batteries.

9. The application according to claim 8, characterized in that: The inorganic interface-coated niobium tungsten oxide heterojunction material is dispersed in a solvent with a conductive agent and a binder to obtain a negative electrode slurry. The negative electrode slurry is coated on a negative electrode current collector, and after drying, rolling, and punching, a negative electrode sheet is obtained, and then the battery is assembled.

Images