Preparation method of quick-charge type negative electrode material and application of quick-charge type negative electrode material in sodium-ion battery
By preparing niobium-molybdenum nitrogen/nitrogen-doped graphene superlattice materials, the problems of small specific surface area and poor cycle stability of niobium nitride in sodium-ion batteries were solved, achieving high rate performance and good cycle stability.
Patent Information
- Application Number
- CN202410623308.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-05-20
- Publication Date
- 2025-11-21
AI Technical Summary
Existing niobium nitride materials in sodium-ion batteries suffer from problems such as small specific surface area, long ion diffusion distance, and poor cycle stability, which cannot meet the needs of practical applications.
Using layered molybdenum-doped lithium niobate as a precursor, a reduced graphene oxide superlattice material modified with molybdenum-doped niobium oxide/polydiallyldimethylammonium chloride is formed through electrostatic self-assembly. A niobium-molybdenum nitrogen solid solution/nitrogen-doped carbon superlattice structure is obtained through carbonization and nitridation reactions. During the nitridation process, the niobium-molybdenum nitrogen solid solution is generated and tightly bonded to the nitrogen-doped graphene to form a stable superlattice structure.
It improves the longitudinal conductivity and cycle stability of the material, buffers volume changes during charge and discharge, and achieves excellent rate performance and cycle stability.
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Figure CN120998949A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the field of electrochemistry and energy storage materials, and particularly relates to a preparation method of a fast-charging type negative electrode material and application thereof in a sodium ion battery. BACKGROUND
[0002] The sodium ion battery is an electrochemical energy storage device, has advantages of rich resources, low manufacturing cost, and good low-temperature performance. In addition, the sodium ion battery has a similar charging and discharging mechanism as the lithium ion battery, which makes the sodium ion battery be able to learn from the existing technology and manufacturing process of the lithium ion battery. Therefore, the sodium ion battery can replace the lithium ion battery in the fields of large-scale energy storage and low-speed electric vehicles. However, the radius (1.02 Å) of the sodium ion is larger than the radius (0.76 Å) of the lithium ion, which makes the sodium ion diffusion dynamics of the negative electrode slow and the volume change large, which seriously limits the development of the sodium ion battery. Therefore, it is of great significance to explore a new type of sodium ion battery negative electrode material with excellent performance. The transition metal nitride has a high theoretical specific capacity and stable chemical properties, and is a very potential sodium ion battery negative electrode material.
[0003] The niobium nitride is a pseudo-capacitive material, has good conductivity and rate performance, and mainly stores sodium ions through the surface or near-surface redox reaction. The niobium nitride is a cubic cell, and the pores in the cell are large, which is beneficial to the storage of Na +However, the current NbN has problems such as small specific surface area, long ion diffusion distance and poor cycle stability, which cannot meet the needs of practical application. Scholars have studied a series of optimization measures to improve the performance of NbN, such as transition metal atom doping, nanocrystallization, and carbon material compounding. The literature "Extra Storage Capacity Enabled by Structural Defects in Pseudocapacitive NbN Monocrystals for High-Energy Hybrid Supercapacitors[J]. Adv. Funct. Mater. 2022, 32, 2112592." by wet chemical pre-mixing and annealing treatment, the defect-rich NbN is embedded in the porous carbon framework to form NbN@C composite negative electrode for lithium ion battery, which has high specific capacity at small current, but poor cycle stability at large current. The literature "Porous niobium nitride as a capacitive anode material for advanced Li-ion hybrid capacitors with superior cycling stability[J]. J. Name. 2012, 00, 1-3" prepared a porous cubic niobium nitride (p-NbN) powder, which has good cycle stability. However, its specific capacity and rate performance are poor. The literature "Interconnected Two-dimensional Arrays of Niobium Nitride Nanocrystals as Stable Lithium Host[J]. Batteries & Supercaps, 2021, 4(1):106-111." uses topological chemistry to prepare a two-dimensional nanometer array of niobium nitride in ammonia, which has high conductivity and rich ion transport channels as a negative electrode material, but the cycle stability and rate performance of the material are poor.
[0004] In summary, the NbN prepared at present has certain limitations, therefore, it is of important research and application significance to further explore the NbN negative electrode material with higher rate performance and cycle stability. SUMMARY
[0005] The present application is proposed to overcome the shortcomings in the prior art, and provides a fast-charging type niobium-molybdenum-nitrogen / nitrogen-doped graphene superlattice negative electrode material and a preparation method thereof, which is applied to a sodium ion battery and exhibits excellent rate performance and cycle stability.
[0006] The application is realized by the following technical scheme: A preparation method of a fast-charging negative electrode material, characterized by comprising the following steps: (1) Disperse layered molybdenum-doped lithium niobate (LiNbMoO6) in a nitric acid solution of 0.1-1 mol / L nitric acid solution, continuously stir for 5 days at room temperature for protonation, and replace the nitric acid solution every day, after the end, centrifugal washing with deionized water, freeze-drying to obtain layered molybdenum-doped niobate (HNbMoO6); (2) Disperse the layered molybdenum-doped niobate prepared in step (1) in a tetrabutylammonium hydroxide solution, shake at room temperature for 7 days to make tetrabutylammonium hydroxide inserted into the interlayer of molybdenum-doped niobate, after the reaction, ultrasonic the mixed solution for 1 hour, then centrifugal at 6000 rpm or more for 20 minutes to remove the molybdenum-doped niobate that has not been exfoliated. Then obtain the molybdenum-doped niobium oxide nanosheet (NbMoO6) suspension; (3) Add polydiallyldimethylammonium chloride solution and hydrazine hydrate to the graphene oxide suspension, and keep it in a water bath at 90 degrees Celsius for 3 hours. Then, centrifugal washing with deionized water. After ultrasonic the precipitate for 2 hours, re-disperse it in deionized water to obtain polydiallyldimethylammonium chloride modified reduced graphene oxide (PDDA-rGO) solution.
[0007] (4) Mix the polydiallyldimethylammonium chloride modified reduced graphene oxide suspension prepared in step (3) and the molybdenum-doped niobium oxide nanosheet suspension (0.1-1 g / L) prepared in step (2) drop by drop with a mass ratio (nanosheet mass ratio) of 0.16-0.25. Then, centrifugal the precipitate with deionized water until the supernatant is neutral. Finally, re-ultrasonic the precipitate and disperse it in deionized water, and freeze-drying to obtain the molybdenum-doped niobium oxide / polydiallyldimethylammonium chloride modified reduced graphene oxide superlattice material (NbMoO6 / PDDA-rGO); (5) Heat the molybdenum-doped niobium oxide / polydiallyldimethylammonium chloride modified reduced graphene oxide superlattice material prepared in step (4) to 300 degrees Celsius at a heating rate of 1-5℃ / min in argon for low-temperature pre-carbonization, then replace the argon with ammonia, and then raise the temperature to 700 degrees Celsius at a heating rate of 1-5℃ / min for nitridation reaction, to obtain the niobium molybdenum nitrogen solid solution and the niobium molybdenum nitrogen / nitrogen-doped carbon superlattice material (NbMoN / NG) with regular stacking of nitrogen-doped carbon. Preferably, the optimal concentration of the nitric acid solution is 0.2 mol / L, and a too low concentration will result in a too long reaction time, and a too high concentration will cause part of the molybdenum to dissolve in the acid, resulting in the surface of the layered molybdenum-doped niobate being corroded and appearing holes, which will damage the structure of the material.
[0008] Preferably, the centrifugal speed is 6000 rpm, and a centrifugal speed lower than 6000 rpm will result in the presence of multiple layers of molybdenum-doped niobium oxide nanosheets in the solution, and the higher the speed, the higher the quality of the nanosheets obtained.
[0009] Preferably, the polydiallydimethylammonium chloride graphene oxide is prepared by the method described in the literature (ACS Energy Letters, 2018, 3(4): 997-1005).
[0010] Preferably, the concentration of the molybdenum-doped niobium oxide nanosheet suspension is 0.6 g / L, and a too low concentration will result in low yield and time-consuming, and a too high concentration will result in the two nanosheets not being regularly stacked layer by layer, and the superlattice structure cannot be obtained.
[0011] Preferably, the optimal mass ratio of the nanosheets is 0.173, which ensures that the area ratio of the two nanosheets is 1:1, so that the nanosheets are completely stacked together.
[0012] Preferably, the low-temperature pre-carbonization temperature in the inert atmosphere (Ar) is 300℃, the heating rate is 2℃ / min, the inert gas flow is 100sccm, and the carbonization time is 2h. A too high heating rate will result in the rapid decomposition of the polydiallydimethylammonium chloride in the superlattice material prepared in step 4, which will destroy the superlattice structure.
[0013] Preferably, the nitriding temperature in the ammonia atmosphere is 700℃, the heating rate is 1℃ / min, the ammonia flow is 60sccm, and the nitriding time is 3h. The optimal heating rate after carbonization is 1℃ / min, and a too fast heating rate will result in the agglomeration of the superlattice.
[0014] The application also provides the application of the niobium-molybdenum-nitrogen / nitrogen-doped carbon superlattice material in sodium ion batteries.
[0015] The application also discloses a niobium-molybdenum-nitrogen / nitrogen-doped graphene superlattice material, which is prepared by the preparation method of the fast-charging negative electrode material. Advantages
[0016] The nitrogen-doped graphene can effectively improve the longitudinal conductivity of the material, prevent the agglomeration of the two nanosheets, and further buffer the volume change of the niobium-molybdenum-nitrogen solid solution nanosheets during the charging and discharging process, thereby improving the cycle stability of the material. BRIEF DESCRIPTION OF DRAWINGS
[0017] Figure 1 A schematic diagram of the preparation method of the niobium molybdenum nitrogen / nitrogen-doped graphene superlattice negative electrode material of the present application is shown in the figure. Figure 2 The X-ray diffraction pattern of the final product prepared in Example 1 of the present application is shown in the figure. Figure 3 The scanning electron microscope image of the final product prepared in Example 1 of the present application is shown in the figure; wherein, figure (a) is the scanning electron microscope image (b) is the element mass ratio detection result image. Figure 4 The atomic force microscope image of the niobium molybdenum nitrogen solid solution prepared in Example 1 of the present application is shown in the figure; wherein, figure (a) is the atomic force microscope image (b) is the corresponding height profile image. Figure 5 The atomic force microscope image of the nitrogen-doped graphene prepared in Example 1 of the present application is shown in the figure; wherein, figure (a) is the atomic force microscope image (b) is the corresponding height profile image. Figure 6 The atomic force microscope image of the final product prepared in Example 1 of the present application is shown in the figure; wherein, figure (a) is the three-dimensional atomic force microscope image (b) is the corresponding height profile image. Figure 7 The transmission electron microscope image of the final product prepared in Example 1 of the present application is shown in the figure; wherein, figure (a) is the transmission electron microscope image (b) is the corresponding high-resolution transmission electron microscope image. Figure 8 The thermogravimetric analysis curve of the final product prepared in Example 1 of the present application is shown in the figure. Figure 9 The cycle performance graph of the material prepared in Example 1 of the present application is shown in the figure. Figure 10 The rate performance graph of the material prepared in Example 1 of the present application is shown in the figure. DETAILED DESCRIPTION
[0018] The present application will be further described in detail below with specific examples, so that those skilled in the art can more clearly understand the present application. However, the following content should not be understood as limiting the scope of protection claimed by the claims of the present application.
[0019] The principle of the present application is: The present application uses layered molybdenum-doped lithium niobate (LiNbMoO6) as a precursor, and obtains a molybdenum-doped niobium oxide / polydiallyldimethylammonium chloride modified reduced graphene oxide superlattice material by using electrostatic self-assembly. Then, the carbonization and nitridation reaction is used to obtain a niobium molybdenum nitrogen solid solution / nitrogen-doped carbon superlattice material. The nitridation process can decompose and carbonize the polydiallyldimethylammonium chloride, and then slowly increase the temperature to form a stable carbon layer. The nitridation reaction is violent and destroys the material structure. When nitridation is carried out in ammonia, the molybdenum-doped niobium oxide is nitrided to form a niobium molybdenum nitrogen solid solution, and nitrogen atoms are doped to replace part of the carbon in the graphene. Because the nitrogen-doped graphene and the niobium molybdenum nitrogen solid solution are closely combined, after the nitridation is completed, the material still has a superlattice structure. Embodiment
[0020] A preparation method of a fast-charging type niobium molybdenum nitrogen / nitrogen-doped graphene superlattice negative electrode material is provided, and the specific preparation process is as follows: (1) 1 g of layered molybdenum-doped lithium niobate is dispersed in 100 ml of a nitric acid solution with a concentration of 65%, and protonation is carried out at room temperature for 5 days, and a new nitric acid solution is changed every day. After the end, centrifugal washing is carried out with deionized water, and freeze-drying is carried out to obtain layered molybdenum-doped niobate; (2) 1 g of the layered molybdenum-doped niobate prepared in step 1 is dispersed in 200 ml of an aqueous solution in which 3.64 g of tetrabutylammonium hydroxide is dissolved, and continuous oscillation is carried out at room temperature for 7 days. Subsequently, the mixture is ultrasonically treated for 1 hour, and then centrifuged at 6000 rpm for 20 minutes to remove the molybdenum-doped niobate that has not been exfoliated. Finally, a single-layer molybdenum-doped niobium oxide nanosheet suspension with negative electricity is obtained.
[0021] (3) A polydiallyldimethylammonium chloride solution and a hydrazine hydrate are added to the graphene oxide suspension, and the mixture is kept in a water bath at 90 degrees Celsius for 3 hours. The mixture is centrifuged and washed with deionized water. The precipitate is ultrasonically treated for 2 hours and then dispersed in deionized water to obtain a polydiallyldimethylammonium chloride modified reduced graphene oxide (PDDA-rGO) suspension with positive electricity.
[0022] (4) The same volume of the molybdenum-doped niobium oxide nanosheet suspension (0.6 / L) prepared in step 2 and the polydiallyldimethylammonium chloride modified reduced graphene oxide suspension (0.104 g / L) prepared in step 3 are mixed and flocculated drop by drop in deionized water. Then, the precipitate is centrifuged and washed with water until the supernatant is neutral. Finally, the precipitate is ultrasonically dispersed in deionized water, and freeze-drying is carried out to obtain a molybdenum-doped niobium oxide / polydiallyldimethylammonium chloride modified reduced graphene oxide superlattice negative electrode material in which molybdenum-doped niobium oxide and reduced graphene oxide nanosheets are alternately stacked.
[0023] (5) The superlattice material prepared in step 4 is heated to 300 degrees Celsius in argon at a heating rate of 2 degrees Celsius per minute for low-temperature pre-carbonization for 2 hours, then raised to 700 degrees Celsius at a heating rate of 1-5 degrees Celsius per minute, and then the argon is replaced with ammonia for nitridation for 3 hours to obtain a Nb-Mo-N solid solution and a Nb-Mo-N / nitrogen-doped graphene superlattice material alternately stacked.
[0024] (6) Preparation of the negative electrode material. The prepared Nb-Mo-N / nitrogen-doped graphene superlattice material, conductive carbon black, and binder sodium carboxymethylcellulose are uniformly ground in a ratio of 8:1:1 by mass in a agate mortar, deionized water is added to prepare a slurry, which is coated on a copper foil and dried in a vacuum drying oven at 50 degrees Celsius for 24 hours.
[0025] (7) The obtained material is used as the negative electrode of a sodium ion battery to assemble a CR2032 type button sodium battery in the order of negative electrode shell-metal sodium negative electrode-separator-electrolyte-negative electrode-gasket-spring positive electrode shell. After assembly, the battery is sealed with a button cell sealing machine to obtain a sodium ion button half cell. The cycle voltammetry test, impedance test, and constant current charge and discharge performance test are performed using a Chenhua electrochemical workstation. The cycle voltammetry test is performed at a voltage range of 0.01 V to 3.0 V and a scan rate of 0.1 mV / s. The impedance test is performed at a frequency range of 1000 KHz-0.1 Hz and a voltage of the initial voltage. The constant current charge and discharge performance test is set at a voltage range of 0.01 V to 3.0 V and a current density of 50 A / g.
[0026] wherein, Figure 1 is a preparation flowchart of the Nb-Mo-N / nitrogen-doped graphene superlattice material.
[0027] Figure 2 is an XRD pattern of the Nb-Mo-N / nitrogen-doped graphene superlattice material. In addition to the graphite peak at 26.6 degrees, the Nb-Mo-N / nitrogen-doped graphene superlattice material has characteristic peaks between the characteristic peaks of NbN and Mo2N. This is because Mo replaces the larger radius Nb atoms in NbN, causing the lattice of NbN to shrink.
[0028] Figure 3 is a scanning electron microscope image and EDS energy spectrum of the product. As can be seen from the figure, the obtained product is a nanosheet with wrinkles on the surface, and the atomic ratio of Nb to Mo is 0.57:0.43. The prepared ternary nitride is Nb 0.57 Mo 0.43 N.
[0029] Figure 4 is an atomic force microscope image of the Nb-Mo-N solid solution. As can be seen from the figure, the thickness of the Nb-Mo-N solid solution is 1 nm.
[0030] Figure 5An atomic force microscope image of the nitrogen-doped graphene, from which it can be seen that the thickness of the nitrogen-doped graphene is 0.7 nm.
[0031] Figure 6 A three-dimensional atomic force microscope image of the niobium-molybdenum-nitrogen / nitrogen-doped graphene superlattice material, from which it can be seen that the thickness thereof is 23.8 nm, which is 14 times the thickness of the niobium-molybdenum-nitrogen solid solution and the nitrogen-doped graphene.
[0032] Figure 7 A transmission electron microscope image of the product, from which it can be seen that the surface of the product is not smooth, which is consistent with the result of the SEM. No agglomeration occurs, and the product has a clear layered structure, and the periodic interlayer spacing is 1.7 nm.
[0033] Figure 8 A thermogravimetric analysis curve of the product, from which it can be seen that the content of carbon in the product is 32.1% according to the test result.
[0034] Figure 9 A long cycle performance graph at a current density of 50 A / g, after 20,000 cycles, still has a reversible specific capacity of about 93 mAh g -1 , and the coulombic efficiency is 90.3%.
[0035] Figure 10 A rate performance graph of the niobium-molybdenum-nitrogen / nitrogen-doped graphene superlattice material, still has a capacity of 103 mAh / g at a current density of 50 A / g. Embodiment
[0036] In this embodiment, except that the concentration (0.8 g / L) of the molybdenum-doped niobium oxide nanosheet suspension in step (4) is different, the rest of the preparation method is the same as that in Embodiment 1.
[0037] A preparation method of a fast-charging type niobium-molybdenum-nitrogen / nitrogen-doped graphene superlattice negative electrode material, the specific preparation process is as follows: (1) 1 g of layered molybdenum-doped lithium niobate is dispersed in 100 ml of a nitric acid solution with a concentration of 1 mol / L, and is protonated at room temperature for 5 days with continuous stirring, and a new nitric acid solution is changed every day, after the end, centrifugal washing with deionized water, freeze-drying to obtain layered molybdenum-doped niobate; (2) 1 g of layered molybdenum-doped niobate prepared in step 1 is dispersed in 200 mL of an aqueous solution containing 3.64 g of tetrabutylammonium hydroxide, and is continuously shaken at room temperature for 7 days. Subsequently, the mixture is ultrasonically treated for 1 hour, and then centrifuged at 6000 rpm for 20 minutes to remove the molybdenum-doped niobate that has not been exfoliated. A molybdenum-doped niobium oxide nanosheet suspension is obtained.
[0038] (3) Polydiallyldimethylammonium chloride solution and hydrazine hydrate were added to the graphene oxide suspension, and the mixture was kept in a water bath at 90°C for 3 hours. The mixture was centrifuged and washed with deionized water. The precipitate was ultrasonically dispersed in deionized water for 2 hours to obtain a polydiallyldimethylammonium chloride modified reduced graphene oxide (PDDA-rGO) suspension.
[0039] (4) The same volume of the molybdenum-doped niobium oxide nanosheet suspension prepared in step 2 (0.8 / L) was mixed with the polydiallyldimethylammonium chloride modified reduced graphene oxide suspension prepared in step 3 (0.104 g / L) dropwise in deionized water to flocculate. Then, the precipitate was centrifuged and washed with water until the supernatant was neutral. Finally, the precipitate was ultrasonically dispersed in deionized water, and after freeze-drying, a molybdenum-doped niobium oxide / polydiallyldimethylammonium chloride modified reduced graphene oxide superlattice negative electrode material was obtained. (5) The superlattice material prepared in step 4 was heated to 300°C at a heating rate of 2°C / min in an argon atmosphere for low-temperature pre-carbonization for 2 hours, and then the temperature was raised to 700°C at a heating rate of 1°C / min. Then, the argon gas was replaced with ammonia gas for nitrogenization for 3 hours to obtain a niobium-molybdenum-nitrogen / nitrogen-doped graphene superlattice material.
[0040] The niobium-molybdenum-nitrogen / nitrogen-doped graphene material obtained by the above embodiment is not a superlattice structure, and its cycle performance and rate performance are worse than those of Example 1. Example
[0041] In this embodiment, except that the concentration of the polydiallyldimethylammonium chloride modified reduced graphene oxide suspension in step (4) is different (0.16 g / L), the rest of the preparation method is the same as that of Example 1.
[0042] A preparation method of a fast-charging type niobium-molybdenum-nitrogen / nitrogen-doped graphene superlattice negative electrode material, and the specific preparation process is as follows: (1) 1 g of layered molybdenum-doped lithium niobate was dispersed in 100 ml of 1 mol / L nitric acid solution, and continuously stirred at room temperature for 5 days for protonation, and a new nitric acid solution was replaced every day. After the end, the precipitate was washed with deionized water by centrifugation, and freeze-dried to obtain layered molybdenum-doped niobate. (2) 1 g of the layered molybdenum-doped niobate prepared in step 1 was dispersed in 200 mL of an aqueous solution containing 3.64 g of tetrabutylammonium hydroxide, and continuously oscillated at room temperature for 7 days to exfoliate. Subsequently, the mixture was ultrasonically dispersed for 1 hour, and then centrifuged at 6000 rpm for 20 minutes to remove the molybdenum-doped niobate that had not been exfoliated. A molybdenum-doped niobium oxide nanosheet suspension was obtained.
[0043] (3) Polydiallyldimethylammonium chloride solution and hydrazine hydrate were added to the graphene oxide suspension, and the mixture was kept in a water bath at 90°C for 3 hours. The mixture was centrifuged and washed with deionized water. The precipitate was ultrasonically dispersed in deionized water for 2 hours to obtain a polydiallyldimethylammonium chloride modified reduced graphene oxide (PDDA-rGO) suspension.
[0044] (4) The same volume of the molybdenum-doped niobium oxide nanosheet suspension prepared in step 2 (0.6 g / L) was mixed with the polydiallyldimethylammonium chloride modified reduced graphene oxide suspension prepared in step 3 (0.16 g / L) dropwise in deionized water to flocculate. Then, the precipitate was centrifuged and washed with deionized water until the supernatant was neutral. Finally, the precipitate was ultrasonically dispersed in deionized water, and after freeze-drying, a molybdenum-doped niobium oxide / polydiallyldimethylammonium chloride modified reduced graphene oxide superlattice negative electrode material was obtained. (5) The superlattice material prepared in step 4 was heated to 300°C at a heating rate of 2°C / min in an argon atmosphere for low-temperature pre-carbonization for 2 hours, and then the temperature was raised to 700°C at a heating rate of 1°C / min. Then, the argon gas was replaced with ammonia gas for nitrogenization for 3 hours to obtain a niobium-molybdenum-nitrogen / nitrogen-doped graphene superlattice material.
[0045] The niobium-molybdenum-nitrogen / nitrogen-doped graphene material obtained by the above example is not a superlattice structure, and has lower initial specific discharge capacity, cycle performance and rate performance than that of example 1. Example
[0046] In this example, the preparation method is the same as that of example 1, except that the freeze-drying process in step (4) is different (the precipitate collected by centrifugation is not ultrasonically dispersed in deionized water).
[0047] A preparation method of a fast-charging type niobium-molybdenum-nitrogen / nitrogen-doped graphene superlattice negative electrode material, and the specific preparation process is as follows: (1) 1 g of layered molybdenum-doped lithium niobate was dispersed in 100 ml of 1 mol / L nitric acid solution, and continuously stirred at room temperature for 5 days for protonation, and a new nitric acid solution was replaced every day. After the end, the precipitate was washed with deionized water by centrifugation, and freeze-dried to obtain layered molybdenum-doped niobate. (2) 1 g of layered molybdenum-doped niobate prepared in step 1 was dispersed in 200 mL of an aqueous solution containing 3.64 g of tetrabutylammonium hydroxide, and continuously oscillated at room temperature for 7 days for exfoliation. Subsequently, the mixture was ultrasonically dispersed for 1 hour, and then centrifuged at 6000 rpm for 20 minutes to remove the molybdenum-doped niobate that had not been exfoliated. A molybdenum-doped niobium oxide nanosheet suspension was obtained.
[0048] (3) Polydiallyldimethylammonium chloride solution and hydrazine hydrate were added to the graphene oxide suspension, and the mixture was kept in a water bath at 90°C for 3 hours. The mixture was centrifuged and washed with deionized water. The precipitate was ultrasonically dispersed in deionized water for 2 hours to obtain a polydiallyldimethylammonium chloride modified reduced graphene oxide (PDDA-rGO) suspension.
[0049] (4) The same volume of the molybdenum-doped niobium oxide nanosheet suspension prepared in step 2 (0.6 g / L) was mixed with the polydiallyldimethylammonium chloride modified reduced graphene oxide suspension prepared in step 3 (0.104 g / L) dropwise in deionized water to flocculate. Then, the precipitate was centrifuged and washed with water until the supernatant was neutral. Finally, the precipitate was freeze-dried to obtain a molybdenum-doped niobium oxide / polydiallyldimethylammonium chloride modified reduced graphene oxide superlattice negative electrode material. (5) The superlattice material prepared in step 4 was heated to 300°C at a heating rate of 2°C / min in an argon atmosphere for low-temperature pre-carbonization for 2 hours, and then the temperature was raised to 700°C at a heating rate of 1°C / min. Then, the argon gas was replaced with ammonia gas for nitrogenization for 3 hours to obtain a niobium-molybdenum-nitrogen / nitrogen-doped graphene superlattice material.
[0050] The niobium-molybdenum-nitrogen / nitrogen-doped graphene material obtained by the above example was severely agglomerated. Example
[0051] In this example, the preparation method is the same as that of Example 1, except that the low-temperature carbonization heating rate in step (5) is different (10°C / min).
[0052] A preparation method of a fast-charging type niobium-molybdenum-nitrogen / nitrogen-doped graphene superlattice negative electrode material, and the specific preparation process is as follows: (1) 1 g of layered molybdenum-doped lithium niobate was dispersed in 100 ml of 1 mol / L nitric acid solution, and continuously stirred at room temperature for 5 days for protonation, and a new nitric acid solution was replaced every day. After the end, the precipitate was washed with deionized water by centrifugation, and freeze-dried to obtain layered molybdenum-doped niobate. (2) 1 g of the layered molybdenum-doped niobate prepared in step 1 was dispersed in 200 mL of an aqueous solution containing 3.64 g of tetrabutylammonium hydroxide, and continuously oscillated at room temperature for 7 days. Subsequently, the mixture was ultrasonically treated for 1 hour, and then centrifuged at 6000 rpm for 20 minutes to remove the molybdenum-doped niobate that had not been exfoliated. A molybdenum-doped niobium oxide nanosheet suspension was obtained.
[0053] (3) Polydiallyldimethylammonium chloride solution and hydrazine hydrate were added to the graphene oxide suspension, and the mixture was kept in a water bath at 90 degrees Celsius for 3 hours. The mixture was centrifuged and washed with deionized water. The precipitate was ultrasonically dispersed in deionized water for 2 hours to obtain a polydiallyldimethylammonium chloride modified reduced graphene oxide suspension.
[0054] (4) The same volume of the molybdenum-doped niobium oxide nanosheet suspension prepared in step 2 (0.6 g / L) was mixed with the polydiallyldimethylammonium chloride modified reduced graphene oxide suspension prepared in step 3 (0.104 g / L) dropwise in deionized water to flocculate. Then, the precipitate was centrifuged and washed with water until the supernatant was neutral. Finally, the precipitate was ultrasonically dispersed in deionized water, and after freeze-drying, a molybdenum-doped niobium oxide / polydiallyldimethylammonium chloride modified reduced graphene oxide superlattice negative electrode material was obtained. (5) The superlattice material prepared in step 4 was heated to 300 degrees Celsius at a heating rate of 10 degrees Celsius per minute in an argon atmosphere for low-temperature pre-carbonization for 2 hours, and then the temperature was raised to 700 degrees Celsius at a heating rate of 1 degree Celsius per minute. Then, the argon gas was replaced with ammonia gas for nitrogenization for 3 hours to obtain a niobium-molybdenum-nitrogen / nitrogen-doped graphene superlattice material.
[0055] In the above embodiment, because the carbonization heating rate is increased, the polydiallyldimethylammonium chloride decomposes too quickly, which ultimately destroys the structure of the niobium-molybdenum-nitrogen / nitrogen-doped graphene superlattice material, resulting in poor electrochemical performance. Embodiment
[0056] In this embodiment, the preparation method is the same as that of embodiment 1, except that the high-temperature nitrogenization heating rate (10 degrees Celsius per minute) in step (5) is different.
[0057] A preparation method of a fast-charging type niobium-molybdenum-nitrogen / nitrogen-doped graphene superlattice negative electrode material, and the specific preparation process is as follows: (1) 1 g of layered molybdenum-doped lithium niobate was dispersed in 100 ml of 1 mol / L nitric acid solution, and continuously stirred at room temperature for 5 days for protonation, and a new nitric acid solution was replaced every day. After the end, the precipitate was washed with deionized water by centrifugation, and freeze-dried to obtain layered molybdenum-doped niobate. (2) 1 g of layered molybdenum-doped niobate prepared in step 1 was dispersed in 200 mL of an aqueous solution containing 3.64 g of tetrabutylammonium hydroxide, and continuously oscillated at room temperature for 7 days to exfoliate. Subsequently, the mixture was ultrasonically dispersed for 1 hour, and then centrifuged at 6000 rpm for 20 minutes to remove the unexfoliated molybdenum-doped niobate. A molybdenum-doped niobium oxide nanosheet suspension was obtained.
[0058] (3) Polydiallyldimethylammonium chloride solution and hydrazine hydrate are added to the graphene oxide suspension, and the mixture is kept in a water bath at 90 degrees Celsius for 3 hours. The mixture is centrifuged and washed with deionized water. The precipitate is ultrasonically dispersed in deionized water for 2 hours to obtain a polydiallyldimethylammonium chloride modified reduced graphene oxide (PDDA-rGO) suspension.
[0059] (4) The same volume of the molybdenum-doped niobium oxide nanosheet suspension (0.6 g / L) prepared in step 2 is mixed with the polydiallyldimethylammonium chloride modified reduced graphene oxide suspension (0.104 g / L) prepared in step 3 drop by drop in deionized water to flocculate. Then, the precipitate is centrifuged and washed with deionized water until the supernatant is neutral. Finally, the precipitate is ultrasonically dispersed in deionized water, and after freeze-drying, a molybdenum-doped niobium oxide / polydiallyldimethylammonium chloride modified reduced graphene oxide superlattice negative electrode material is obtained. (5) The superlattice material prepared in step 4 is heated to 300 degrees Celsius at a heating rate of 2 degrees Celsius per minute in an argon atmosphere for low-temperature pre-carbonization for 2 hours, and then the temperature is raised to 700 degrees Celsius at a heating rate of 10 degrees Celsius per minute. Then, the argon gas is replaced with ammonia gas for nitrogenization for 3 hours to obtain a niobium-molybdenum-nitrogen / nitrogen-doped graphene superlattice material.
[0060] In the above embodiment, due to the increase in the heating rate of the nitrogenization process, the niobium-molybdenum-nitrogen / nitrogen-doped graphene superlattice material agglomerates, resulting in poor electrochemical performance.
[0061] The present application provides a preparation method of a fast-charging type niobium-molybdenum-nitrogen / nitrogen-doped graphene superlattice negative electrode material. The two-dimensional superlattice material is composed of niobium-molybdenum-nitrogen solid solution and nitrogen-doped graphene nanosheets stacked in a regular manner, greatly improving the diffusion speed of ions and electrons in the material. The partial substitution of molybdenum atoms for niobium atoms improves the specific capacity of the niobium-molybdenum-nitrogen solid solution material. In addition, the nitrogen-doped graphene can reduce the volume expansion of the niobium-molybdenum-nitrogen solid solution and inhibit the agglomeration of the niobium-molybdenum-nitrogen solid solution during sodium intercalation / deintercalation. The material has good cycle stability and fast-charging performance.
Claims
1. A method for preparing a fast-charging type negative electrode material, characterized by, The method comprises the following steps: (1) dispersing layered molybdenum-doped lithium niobate in a nitric acid solution, protonating at room temperature for several days under continuous stirring, and replacing the nitric acid solution every day, and after the end, centrifugal washing with deionized water and freeze-drying to obtain layered molybdenum-doped niobate; (2) dispersing the layered molybdenum-doped niobate prepared in step (1) in a tetrabutylammonium hydroxide solution, and oscillating at room temperature for several days to insert tetrabutylammonium hydroxide into the interlayer of the molybdenum-doped niobate, after the reaction is completed, the mixed solution is ultrasonic, and then the molybdenum-doped niobate that is not exfoliated is removed by centrifugation, and then a molybdenum-doped niobium oxide nanosheet suspension is obtained; (3) adding a polydiallyldimethylammonium chloride solution and a hydrazine hydrate into a graphene oxide suspension, and keeping it in a water bath; then, centrifugal washing with deionized water; ultrasonic treatment of the precipitate and then redispersion in deionized water to obtain a polydiallyldimethylammonium chloride modified reduced graphene oxide solution; (4) mixing the same volume of the molybdenum-doped niobium oxide nanosheet suspension prepared in step (2) and the polydiallyldimethylammonium chloride modified reduced graphene oxide suspension prepared in step (3) drop by drop, and then centrifuging the precipitate with deionized water until the supernatant is neutral; finally, redispersion of the precipitate in deionized water by ultrasonic treatment, and freeze-drying to obtain a molybdenum-doped niobium oxide / polydiallyldimethylammonium chloride modified reduced graphene oxide superlattice material; (5) low-temperature pre-carbonization of the molybdenum-doped niobium oxide / polydiallyldimethylammonium chloride modified reduced graphene oxide superlattice material prepared in step (4) in an inert atmosphere, and switching to ammonia gas for nitridation when the temperature is raised to the nitridation temperature, to obtain a niobium molybdenum nitride solid solution nanosheet and a niobium molybdenum nitride / nitrogen-doped carbon superlattice material with regularly stacked nitrogen-doped carbon.
2. The preparation method of the fast-charging negative electrode material according to claim 1, wherein in step (1), the concentration of the nitric acid solution is 0.2 mol / L.
3. The preparation method of the fast-charging negative electrode material according to claim 1, wherein in step (2), the tetrabutylammonium hydroxide is inserted into the interlayer of the molybdenum-doped niobate by oscillation at room temperature for 7 days, the mixed solution is ultrasonic for 1 hour after the reaction is completed, and then centrifuged at 6000 rpm for 20 minutes; and the concentration of the molybdenum-doped niobium oxide nanosheet suspension is 0.6 g / L.
4. The preparation method of the fast-charging negative electrode material according to claim 1, wherein in step (3), the water bath is kept at 90 degrees Celsius for 3 hours; the precipitate is redispersed in deionized water after ultrasonic treatment for 2 hours; and the concentration of the polydiallyldimethylammonium chloride modified reduced graphene oxide nanosheet suspension is 0.104 g / L.
5. The preparation method of the fast-charging negative electrode material according to claim 1, wherein in step (5), the low-temperature pre-carbonization temperature in the inert atmosphere is 300 degrees Celsius, the heating rate is 2 degrees Celsius per minute, the inert gas flow is 100 sccm, and the carbonization time is 2 hours.
6. The preparation method of claim 1, wherein the nitriding temperature in the ammonia atmosphere is 700℃, the heating rate is 1℃ / min, the ammonia flow rate is 60sccm, and the nitriding time is 3h in step (5).
7. A fast-charging battery anode material, characterized in that, The niobium molybdenum nitride / nitrogen-doped graphene superlattice material prepared by the preparation method of any one of claims 1-6 is used as a battery negative electrode material.
8. A niobium molybdenum nitride / nitrogen doped graphene superlattice material characterized by, The material is prepared by the preparation method of any one of claims 1-6, and has a layered superlattice structure formed by alternately stacking single-layer niobium molybdenum nitride solid solution nanosheets and single-layer nitrogen-doped graphene; the atomic ratio of niobium to molybdenum in the niobium molybdenum nitride solid solution is about 1:1, and the content of the nitrogen-doped graphene is 32.1%; the sodium storage mechanism is intercalation reaction, and the nitrogen-doped graphene can relieve the volume expansion of the niobium molybdenum nitride solid solution during the sodium storage process, thereby maintaining the stability of the material structure.
9. A sodium-ion battery, characterized in that, The battery uses the material of any one of claims 7-8.