A high-fast-charging T-Nb2O5 anode material, its preparation method and application

Abstract

A kind of high fast-charging performance T-Nb2O5 negative electrode material and its preparation method and application belong to lithium ion battery material technical field.The method is: niobium source, oxalic acid dihydrate and ammonium fluoride are dispersed into water in sequence to obtain clear solution, add citric acid, control micron flower-like precursor to preferentially expose high activity crystal face;Solution is carried out hydrothermal reaction, after ending, centrifugal drying is obtained even precursor;The precursor is calcined in oxygen-containing atmosphere at high temperature, after calcining, first with the rate of 2 ℃ / min to 200~400 ℃, then quickly immersed in brine and rapidly cooled to room temperature, so that high activity interface layer is formed in situ on the surface of material.The T-Nb2O5 negative electrode material with "crystalline nucleus-active shell" composite structure is obtained by synergistic temperature control strategy, the material has excellent bulk ion transport kinetics and extremely low surface interface reaction impedance, the charge and discharge capacity retention rate at 10C high rate is significantly improved, has excellent cycle stability and fast-charging performance, and is suitable for high-power lithium ion battery.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery materials technology, specifically to a high-fast-charging performance T-Nb2O5 anode material based on a composite temperature control of "slow cooling-salt water quenching" and its preparation method and application. Background Technology

[0002] With the rapid development of new energy vehicles, portable electronic devices, and other fields, the market is placing increasingly higher demands on the fast-charging performance, rate performance, and cycle stability of lithium-ion batteries. As a core component of lithium-ion batteries, the structure and performance of the anode material directly determine the overall performance of the battery. Niobium pentoxide (Nb₂O₅), with its high theoretical capacity, safe lithium-ion intercalation potential, and excellent rate performance, is considered a highly promising anode material for fast-charging lithium-ion batteries. Among them, the orthorhombic T-Nb₂O₅, due to its unique open crystal structure, provides a rapid two-dimensional diffusion channel for lithium ions, resulting in particularly outstanding electrochemical performance.

[0003] Currently, researchers have employed various methods to prepare T-Nb₂O₅ materials, such as solid-state methods, hydrothermal methods, and sol-gel methods. Among these, the hydrothermal method is widely used to prepare T-Nb₂O₅ with special morphologies due to its simplicity and high controllability. However, existing hydrothermal methods often produce T-Nb₂O₅ with nanoscale structures, which pose a risk of agglomeration in practical applications, leading to obstructed ion transport pathways and affecting rate performance. Furthermore, nanomaterials often suffer from low tap density and numerous surface side reactions. Simultaneously, during the calcination and cooling process, traditional slow cooling is beneficial for obtaining a bulk phase with high crystallinity and low internal stress, but surface activity is generally limited. Rapid cooling (quenching) may introduce highly active defects on the material surface, but it easily leads to incomplete bulk crystallization or crack formation. Therefore, how to simultaneously endow T-Nb₂O₅ materials with a highly crystalline bulk phase and a highly active surface through a simple and controllable process, thereby achieving a breakthrough in comprehensive performance, remains a key technological challenge. Summary of the Invention

[0004] To address the aforementioned shortcomings in existing technologies, the present invention aims to provide a high-fast-charging performance T-Nb2O5 anode material based on a composite temperature control method of "slow cooling-salt water quenching" and its preparation method and application. Through a composite temperature control cooling strategy, a T-Nb2O5 anode material with a composite structure of "crystallization nucleus-active shell" is prepared, achieving excellent performance at multiple rates of 0.2C, 5C, and 10C.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing a high-fast-charging-performance T-Nb2O5 anode material, the method comprising the following steps:

[0007] (1) Preparation of precursor solution: Niobium source, oxalic acid dihydrate and ammonium fluoride are dispersed in water one after another and stirred until a clear solution is formed. Citric acid is then added to the clear solution as a chelating agent and stirred until the mixture is homogeneous.

[0008] (2) Hydrothermal reaction: The mixed solution obtained in step (1) is transferred to a reaction vessel for hydrothermal reaction. After the reaction is completed, it is centrifuged and dried to obtain a micron flower-like precursor.

[0009] (3) Calcination and composite temperature control treatment: The micron flower-shaped precursor obtained in step (2) is placed in an oxygen-containing atmosphere for high-temperature calcination. After calcination, the temperature is first slowly reduced to 200~400℃ at a rate of 2℃ / min. The slow cooling in the high-temperature section ensures good bulk crystallization and structural relaxation of the material. Then, the material is rapidly immersed in a brine quenching medium and rapidly cooled to room temperature of 20~30℃. The rapid cooling in the low-temperature section creates an interface layer with abundant defects. Then, the material is centrifuged and washed until neutral, and dried to obtain T-Nb2O5 anode material.

[0010] Further, in step (1), the niobium source is one of niobium oxalate, niobium pentachloride or niobium ethoxide; the molar ratio of the niobium source, oxalic acid dihydrate, ammonium fluoride and citric acid is 1:4~6:2~3:0.1~0.5.

[0011] Furthermore, in step (1), after adding the chelating agent, the concentration of the niobium source in water is 0.04~0.1 mol / L; the stirring temperature is 25~40℃, the stirring time is 30~60 min, and the stirring is thorough to ensure the formation of a precursor solution with uniform composition.

[0012] Furthermore, in step (2), the hydrothermal reaction temperature is 180~220℃ and the time is 12~24 h. Sufficient hydrothermal time ensures the uniformity of the precursor; the drying temperature is 60~100℃ and the time is 8~12 h.

[0013] Furthermore, in step (3), the conditions for high-temperature calcination are: calcination temperature of 600~800℃ and holding time of 2~4 h; the oxygen-containing atmosphere is air or oxygen, and the gas flow rate is 10~30 mL / min. Under these conditions, calcination can ensure that the precursor is completely converted into T-Nb2O5 with good crystallinity.

[0014] Further, in step (3), the brine is a sodium chloride aqueous solution or potassium chloride aqueous solution with a mass fraction of 5% to 15%, and the brine temperature is 20 to 30°C.

[0015] Furthermore, in step (3), the rapid cooling rate is ≥200℃ / min, and rapid cooling helps to form abundant defects on the material surface.

[0016] A T-Nb2O5 anode material obtained by the above preparation method, wherein the anode material has a micron flower-like structure and preferentially exposes highly active crystal faces; the material has a "nucleus-active shell" composite structure, wherein the nucleus is an ordered crystal form T-Nb2O5 and the active shell is a T-Nb2O5 interface layer with abundant defects.

[0017] An application of the above-mentioned T-Nb2O5 anode material, wherein the T-Nb2O5 anode material is used to prepare the anode sheet of a high-power lithium-ion battery, and the high-power lithium-ion battery is suitable for fast charging scenarios.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) By adding ammonium fluoride as a mineralizing agent and citric acid as a chelating agent in the hydrothermal stage, and by controlling the raw material ratio and hydrothermal parameters, the present invention successfully prepared a micron flower-like precursor. The overall particle size of the obtained T-Nb2O5 material is 2~4 μm, which not only avoids the problem of nanostructure aggregation, but also preferentially exposes highly active crystal faces, providing sufficient channels for rapid ion transport.

[0020] (2) The present invention adopts a composite temperature control cooling strategy of “slow cooling in high temperature section + salt water quenching in low temperature section”. The slow cooling stage allows the bulk phase of the material to fully crystallize and relax, ensuring the structural stability of the material. The salt water quenching stage forms a highly active interface layer with controllable defects on the surface of the material, constructing a “crystallization nucleus-active shell” composite structure, which synergistically improves the bulk phase ion transport efficiency and surface and interface reaction activity of the material.

[0021] (3) The T-Nb2O5 anode material prepared by the present invention has excellent rate performance, high capacity at 30C high rate, and high capacity retention rate at 5C and 10C high current density cycling. It also has excellent fast charging performance and long cycle stability, which can meet the application requirements of high power lithium-ion batteries. Attached Figure Description

[0022] Figure 1 The X-ray diffraction patterns of the materials prepared in Example 1 and Comparative Examples 1 and 2 of this invention are shown below.

[0023] Figure 2 The following are rate performance graphs of the materials prepared in Example 1 and Comparative Examples 1 and 2 of this invention at different current densities;

[0024] Figure 3 The graph shows the cycling performance of the materials prepared in Example 1 and Comparative Examples 1 and 2 of this invention at 0.2C.

[0025] Figure 4The graph shows the cycling performance of the materials prepared in Example 1 and Comparative Examples 1 and 2 of this invention at 5C.

[0026] Figure 5 The graph shows the cycling performance of the materials prepared in Example 1 and Comparative Examples 1 and 2 of this invention at 10°C. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0028] Example 1

[0029] (1) Dissolve 3 mmol niobium pentachloride and 15 mmol oxalic acid dihydrate in 70 mL of deionized water and stir magnetically for 30 minutes. Then add 8 mmol ammonium fluoride and continue stirring until completely clear. Finally add 0.3 mmol citric acid and stir at 25-40℃ for 1 hour to obtain the precursor solution.

[0030] (2) The solution was transferred to a 100 mL high-pressure reactor lined with polytetrafluoroethylene and placed in a homogeneous reactor at 200 °C for 24 hours. After the reaction was completed, the mixture was allowed to cool naturally. The precipitate was centrifuged, washed three times alternately with deionized water and ethanol, and dried in a vacuum drying oven at 80 °C for 12 hours to obtain the precursor powder.

[0031] (3) The precursor powder was placed in a tube furnace and calcined at 700°C for 2 hours at a rate of 5°C / min under air atmosphere. After calcination, the temperature was immediately reduced to 300°C at a rate of 2°C / min. Then, the material was quickly transferred and immersed in a quenching tank containing a 10 wt% NaCl aqueous solution (20~30°C), and vigorously stirred to ensure rapid and uniform cooling at a rate ≥200°C / min. Finally, the quenched material was centrifuged and washed until neutral, and dried at 120°C to obtain the final product T-Nb2O5 material (labeled as Slow-Nb2O5).

[0032] (4) The prepared Slow-Nb2O5 anode material was assembled into a half-cell for electrochemical performance testing. PVDF was used as the binder and Super P as the conductive agent in the preparation of the slurry. The active material, conductive agent, and binder were weighed in a ratio of 8:1:1. These materials were uniformly dispersed in the organic solvent NMP. The resulting electrode slurry was coated onto the current collector copper foil, then dried, rolled, and sliced ​​before half-cell assembly. The entire assembly process was carried out in a glove box with low water and oxygen content (<0.1 ppm). Lithium foil was used as the electrode, Celgard polypropylene film as the separator, and 1 M LiPF6 (a 1:1:1 volume ratio of ethylene carbonate / diethyl carbonate / dimethyl carbonate mixed solvent) was used as the electrolyte. The nominal specific capacity was set at 200 mAh / g for subsequent electrochemical testing. After battery assembly, the cells were allowed to stand for 10 h before activation and testing.

[0033] Example 2

[0034] The difference from Example 1 is that in step 3, the precursor powder was placed in a tube furnace and calcined at 700°C for 2 hours under air atmosphere at a rate of 5°C / min. After calcination, a cooling program was immediately initiated, slowly cooling the material to 200°C at a rate of 2°C / min. Subsequently, the material was rapidly transferred and immersed in a quenching tank containing a 10 wt% NaCl aqueous solution, with vigorous stirring to ensure rapid and uniform cooling. Finally, the quenched material was centrifuged, washed until neutral, and dried at 120°C to obtain the final product, T-Nb2O5 material.

[0035] Example 3

[0036] The difference from Example 1 is that in step 3, the precursor powder was placed in a tube furnace and calcined at 700°C for 2 hours under air atmosphere at a rate of 5°C / min. After calcination, a cooling program was immediately initiated, slowly cooling the material to 300°C at a rate of 2°C / min. Subsequently, the material was rapidly transferred and immersed in a quenching tank containing a 15 wt% NaCl aqueous solution, with vigorous stirring to ensure rapid and uniform cooling. Finally, the quenched material was centrifuged, washed until neutral, and dried at 120°C to obtain the final product, T-Nb2O5 material.

[0037] Table 1 compares the rate performance of the negative electrode materials in Examples 1-3. It can be seen that by slightly adjusting the endpoint of slow cooling and the concentration of the quenching solution, the prepared T-Nb2O5 materials all exhibit good electrochemical performance, further demonstrating the stability of this process.

[0038]

[0039] Comparative Example 1

[0040] The difference from Example 1 is that in step 3, the precursor powder is placed in a tube furnace and calcined at 700°C at a rate of 5°C / min for 2 hours under an air atmosphere. After calcination, the material is allowed to cool naturally to room temperature to obtain the final product T-Nb2O5 material (labeled as Nb2O5).

[0041] Comparative Example 2

[0042] The difference from Example 1 is that in step 3, the precursor powder was placed in a tube furnace and calcined at 700°C for 2 hours under an air atmosphere at a rate of 5°C / min. After calcination, the material was directly quenched with a 10 wt% NaCl aqueous solution. The quenched material was then centrifuged and washed until neutral, and dried at 120°C to obtain the final product T-Nb2O5 material (labeled as Fast-Nb2O5).

[0043] Figure 1 The figures show the X-ray diffraction patterns of the materials prepared in Example 1 and Comparative Examples 1 and 2 of this invention. As can be seen from the figures, the characteristic diffraction peaks of the sample in Example 1 are all X-ray diffraction peaks of T-Nb₂O₅, proving that the prepared sample has a single crystal orientation, no impurities, and good crystallinity. The Nb₂O₅ sample of Comparative Example 1, after natural cooling, exhibits good crystallinity, and its characteristic peaks correspond one-to-one with the standard cards. However, the sample directly quenched in brine at 700℃ has a small amount of impurity phase, indicating incomplete bulk crystallization or numerous defects.

[0044] Figure 2 The graphs show the rate performance of the half-cells assembled with the negative electrode materials prepared in Example 1 and Comparative Examples 1 and 2 of this invention at different current densities. As can be seen from the graphs, the material prepared in Example 1 still maintains a discharge specific capacity of 91.7 mAh / g even at a high rate of 30C, and in subsequent 0.2C cycles, the battery capacity still retains the initial 195.5 mAh / g, demonstrating that the Slow-Nb2O5 material prepared using the "slow cooling-salt quenching" composite temperature control strategy has excellent electrochemical reversibility. The comparison shows that at different rates, the discharge specific capacity of Example 1 is superior to that of Comparative Examples 1 and 2. In particular, Comparative Example 2, due to its higher bulk defects, experiences a sharp decrease in capacity under high current charge-discharge conditions.

[0045] Figure 3 , 4Figures 5 and 6 show the cycling performance of the half-cells assembled with the negative electrode materials prepared in Example 1 and Comparative Examples 1 and 2 of this invention at 0.2C, 5C, and 10C. As can be seen from the figures, the Slow-Nb2O5 material exhibits a capacity retention of up to 97.1% under 120 continuous charge-discharge cycles, demonstrating excellent cycling stability. After 1000 cycles, the material still has a discharge specific capacity of 114.7 mAh / g, with a capacity retention of 68.1%. The comparison shows that, compared with Nb2O5 and Fast-Nb2O5 prepared by natural cooling and salt water quenching only in Comparative Examples 1 and 2, Slow-Nb2O5 prepared by the "slow cooling-salt water quenching" composite temperature control strategy in Example 1 exhibits better cycle stability and higher capacity. Even at a high rate of 30C, the discharge specific capacity of the battery is still as high as 91.7 mAh / g. After 1000 cycles under 10C fast charging conditions, the discharge specific capacity of the material is still 87.2 mAh / g, with a capacity retention rate of 55.2%, which meets the fast charging application requirements of high-power lithium-ion batteries.

[0046] This invention successfully prepared a micron-sized, flower-like T-Nb2O5 anode material with a "nucleation nucleus-active shell" composite structure through an innovative process combining hydrothermal method with "slow cooling-salt quenching" for temperature control. This process optimizes bulk crystallization through slow cooling at high temperatures and constructs a highly active interface through salt quenching at low temperatures, synergistically improving the material's ion / electron transport capability and structural stability. The prepared material exhibits high discharge specific capacity, excellent rate performance, and long cycle life across a wide rate range from 0.2C to 10C, making it particularly suitable for lithium-ion battery applications requiring fast charging and high power output.

[0047] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a high-fast-charging performance T-Nb2O5 anode material, characterized in that: The method includes the following steps: (1) Preparation of precursor solution: Niobium source, oxalic acid dihydrate and ammonium fluoride are dispersed in water one after another, stirred until a clear solution is formed, then citric acid is added and stirred until evenly mixed; (2) Hydrothermal reaction: The mixed solution obtained in step (1) is transferred to a reaction vessel for hydrothermal reaction. After the reaction is completed, it is centrifuged and dried to obtain a micron flower-like precursor. (3) Calcination and composite temperature control treatment: The micron flower-shaped precursor obtained in step (2) is placed in an oxygen-containing atmosphere for high-temperature calcination. After calcination, the temperature is first slowly reduced to 200~400℃ at a rate of 2℃ / min. Then, the material is rapidly immersed in a brine quenching medium and rapidly cooled to room temperature of 20~30℃. Subsequently, it is centrifuged and washed until neutral, and then dried to obtain T-Nb2O5 anode material.

2. The preparation method according to claim 1, characterized in that: In step (1), the niobium source is one of niobium oxalate, niobium pentachloride or niobium ethoxide; the molar ratio of the niobium source, oxalic acid dihydrate, ammonium fluoride and citric acid is 1:4~6:2~3:0.1~0.

5.

3. The preparation method according to claim 1, characterized in that: In step (1), after adding citric acid, the concentration of niobium source in water is 0.04~0.1 mol / L; the stirring temperature is 25~40℃ and the stirring time is 30~60 min.

4. The preparation method according to claim 1, characterized in that: In step (2), the temperature of the hydrothermal reaction is 180~220℃ and the time is 12~24 h, and the temperature of the drying is 60~100℃ and the time is 8~12 h.

5. The preparation method according to claim 1, characterized in that: In step (3), the conditions for high-temperature calcination are: calcination temperature of 600~800℃, holding time of 2~4 h; the oxygen-containing atmosphere is air or oxygen, and the gas flow rate is 10~30mL / min.

6. The preparation method according to claim 1, characterized in that: In step (3), the brine is a sodium chloride aqueous solution or potassium chloride aqueous solution with a mass fraction of 5% to 15%, and the brine temperature is 20 to 30°C.

7. The preparation method according to claim 1, characterized in that: In step (3), the rapid cooling rate is ≥200℃ / min.

8. A T-Nb2O5 anode material obtained by the preparation method according to any one of claims 1 to 7, characterized in that: The negative electrode material has a micron-shaped flower structure and preferentially exposes highly active crystal faces; the material has a "nucleus-active shell" composite structure, wherein the nucleus is an ordered crystal form T-Nb2O5 and the active shell is a T-Nb2O5 interface layer with abundant defects.

9. An application of the T-Nb2O5 anode material according to claim 8, characterized in that: The T-Nb2O5 anode material is used to prepare the anode sheet for high-power lithium-ion batteries, which are suitable for fast-charging scenarios.

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