Niobium-doped lithium titanate material as well as preparation method and application thereof

Abstract

The invention belongs to the field of lithium ion batteries, and discloses a niobium-doped lithium titanate material and a preparation method and application thereof.The preparation method comprises the steps that a titanium source, a dispersing agent, organic acid and deionized water are used for preparing a mixed solution; adding a lithium source and a niobium source into the mixed solution, adjusting the pH value of the mixed solution to 7.8-8.2 by using ammonia water, and volatilizing water in the mixed solution to obtain wet gel; drying the wet gel to obtain precursor powder; and calcining the precursor powder to obtain the niobium-doped lithium titanate material. The niobium-doped lithium titanate material prepared by the method has a stable voltage platform and excellent rate capability and cycling stability in the charging and discharging process, the preparation method has the advantages of simple steps, no need of complex process flow, low cost, no pollution, convenience in industrialization, abundant and low-price required raw materials, lower energy consumption in the reaction process, and good application prospect. The preparation method is more environment-friendly and is a green, environment-friendly and efficient preparation method.

Description

Technical Field

[0001] This application belongs to the field of lithium-ion batteries, and in particular relates to a niobium-doped lithium titanate material, its preparation method and application. Background Technology

[0002] Traditional lithium-ion batteries suffer from rapid capacity decay at low temperatures due to sluggish electrochemical reaction kinetics, severely limiting their application in cold regions, deep-sea exploration, and aerospace. Electrochemical reaction kinetics performance depends primarily on factors such as battery configuration, electrolyte system, solid-electrolyte interface (SEI) formation, and electrode material selection. The negative electrode material has a particularly significant impact on electrochemical reaction kinetics performance; therefore, reducing charge transfer resistance, optimizing bulk resistance, and developing novel suitable materials are crucial.

[0003] Among existing lithium-ion battery anode materials, graphite / carbon-based anodes, which contain lithium in a layered graphite structure, have some drawbacks: first, a solid electrolyte interphase (SEI) layer forms on the surface of graphite / carbon particles; second, they shrink and expand as lithium ions are extracted and inserted; and third, they have large energy losses and poor charge-discharge performance at high rates. Tin-based and silicon-based materials are used as anode materials because they have high theoretical capacity, lithium packing density, and suitable operating voltage. However, tin-based and silicon-based materials undergo drastic volume changes during cycling, which limits their cycle life and reduces the possibility of commercialization.

[0004] Among various solid-state, liquid-state, and gel-state lithium-ion batteries, spinel-type Li4Ti5O 12 As a reliable anode material, it has been developed and used due to two significant characteristics: excellent reversibility of lithium-ion extraction and insertion, and minimal volume change during lithium transport. However, Li4Ti5O 12 However, it also has some limitations, such as low conductivity, limited lithium-ion diffusion, and inherent insulating properties, which restrict its high-rate performance. These limitations can be improved through strategies such as doping. Because niobium and titanium ions have similar radii (r(Ti)... 4+ ) = 0.605Å, r(Nb 5+ ()=0.64Å), using Nb 5+ Replaces Ti 4+ Nb 5+ It can form strongly hybridized 4d orbitals with the 3d orbitals of Ti, inducing Ti 4+ To Ti 3+ Transformation. Therefore, heteroatom doping is considered to improve the performance of Li4Ti5O. 12 An effective method for assessing intrinsic conductivity is to use dopants as Li4Ti5O. 12 Substituents in the crystal structure can improve its performance in lithium-ion batteries.

[0005] In view of the shortcomings of the above technologies, it is necessary to propose a niobium-doped lithium titanate anode and its preparation method to overcome the problems of low conductivity, limited lithium-ion diffusion ability, poor rate performance and complex preparation process of existing lithium titanate electrodes. Summary of the Invention

[0006] In order to overcome the defects of the existing technology, the purpose of this application is to provide a niobium-doped lithium titanate anode and its preparation method, which overcomes the problems of low conductivity, limited lithium-ion diffusion ability, poor rate performance and complex preparation process of existing lithium titanate electrodes.

[0007] To achieve the above objectives, this application provides the following technical solution: A method for preparing a niobium-doped lithium titanate material includes: A mixed solution was prepared using a titanium source, a dispersant, an organic acid, and deionized water. Lithium and niobium sources were added to the mixed solution, and the pH of the mixed solution was adjusted to 7.8-8.2 using ammonia. The water in the mixed solution was then evaporated to obtain a wet gel. The wet gel was dried to obtain the precursor powder; The precursor powder was calcined to obtain niobium-doped lithium titanate material.

[0008] Furthermore, the atomic ratio of lithium to titanium in the lithium source and titanium source is 4:5.

[0009] Furthermore, the titanium source is any one of tetrabutyl titanate, tetraisopropyl titanate, titanium dioxide, hydrated titanium dioxide, and titanium tetrachloride.

[0010] Furthermore, the lithium source is one or more of lithium hydroxide monohydrate, lithium hydroxide, lithium carbonate, lithium oxalate, and lithium nitrate.

[0011] Furthermore, the niobium source is Nb(OH)5 or Nb2O5.

[0012] Furthermore, evaporating the water from the mixed solution includes: Heat the mixed solution to 50-70℃ to evaporate the water.

[0013] Furthermore, the precursor powder is calcined, including: The precursor powder was first calcined to initially decompose the organic acids; The precursor powder was calcined a second time to obtain niobium-doped lithium titanate material.

[0014] Furthermore, the temperature of the first calcination is 200-400℃, and the calcination time is 1-3 hours.

[0015] Furthermore, the second calcination temperature is 700-900℃, and the calcination time is 2-6 hours.

[0016] This application also discloses a niobium-doped lithium titanate material prepared by the above-mentioned method, with the general structural formula Li₄Ti. 5-X Nb X O 12 , where 0 < x ≤ 0.15.

[0017] This application also discloses an application of the above-mentioned niobium-doped lithium titanate material, which is used as the negative electrode of a lithium-ion battery.

[0018] The technical effects and advantages of this application are as follows: (1) This application adjusts the lattice parameters and cell volume of lithium titanate by niobium doping, thereby improving the ionic conductivity and electronic conductivity. A small amount of Nb 5+ Doping did not affect the morphology of the material, nor did it result in severe particle agglomeration. After doping, there was sufficient contact between the active material and the electrolyte, which is beneficial for the Li in the electrode. + The diffusion of the diffusion process was tested by electrochemical analysis, and it exhibited a stable voltage plateau and excellent rate performance and cycle stability during charge and discharge.

[0019] (2) This application uses the sol-gel method to prepare niobium-doped lithium titanate materials. The steps are simple, no complicated process is required, the cost is low, there is no pollution, it is easy to industrialize, the required raw materials are abundant and inexpensive, the reaction process consumes less energy, and it is more environmentally friendly. It is a green, environmentally friendly and efficient preparation method.

[0020] Other features and advantages of this application will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the application. The objectives and other advantages of this application may be realized and obtained by means of the structures pointed out in the description, claims and drawings. Attached Figure Description

[0021] Figure 1 This is a flowchart illustrating the preparation method of niobium-doped lithium titanate material according to an embodiment of this application; Figure 2 The XRD pattern of the niobium-doped lithium titanate sample in this application embodiment; Figure 3 This is a graph showing the first constant current charge-discharge curve of a niobium-doped lithium titanate sample at 0.1C rate, according to an embodiment of this application. Figure 4 This is a cycling performance diagram of a niobium-doped lithium titanate sample according to an embodiment of this application. Detailed Implementation

[0022] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0023] like Figure 1 As shown, this application provides a method for preparing niobium-doped lithium titanate material, comprising: A certain amount of titanium source is weighed according to the stoichiometric ratio and added to a dispersant, which can be ethanol, urea, acetonitrile, methanol, or ethylenediamine. After stirring evenly, solution A is formed. An organic acid is dissolved in deionized water to form solution B. The organic acid can be citric acid, oxalic acid, or malic acid. Solution B is slowly added to solution A to obtain a mixed solution. Lithium and niobium sources are then added to the mixed solution. The pH of the mixed solution is adjusted to a weakly alkaline state, for example, 7.8-8.2, using ammonia water. The mixed solution is then heated to evaporate the water, resulting in a wet gel. The wet gel is then dried to obtain a precursor powder. The precursor powder is calcined to obtain niobium-doped lithium titanate material.

[0024] In some embodiments of this application, the atomic ratio of lithium to titanium in the lithium source and titanium source is 4:5.

[0025] In some embodiments of this application, the titanium source is any one of tetrabutyl titanate, tetraisopropyl titanate, titanium dioxide, hydrated titanium dioxide, and titanium tetrachloride.

[0026] In some embodiments of this application, the lithium source is one or more of lithium hydroxide monohydrate, lithium hydroxide, lithium carbonate, lithium oxalate, and lithium nitrate.

[0027] In some embodiments of this application, the niobium source is Nb(OH)5 or Nb2O5.

[0028] In some embodiments of this application, evaporating the water from the mixed solution includes heating the mixed solution to 50-70°C to evaporate the water.

[0029] In some embodiments of this application, the precursor powder is calcined, including: The precursor powder was calcined for the first time at a temperature of 200-400℃ for 1-3 hours to initially decompose the organic acids. The precursor powder was then subjected to a second calcination at a temperature of 700-900℃ for 2-6 hours to obtain niobium-doped lithium titanate material.

[0030] This application also discloses a niobium-doped lithium titanate material prepared by the above-mentioned method, with the general structural formula Li₄Ti. 5-X Nb X O 12 , where 0 < x ≤ 0.15.

[0031] This application also discloses an application of the above-mentioned niobium-doped lithium titanate material, which is used as the negative electrode of a lithium-ion battery.

[0032] To better explain this solution, the following embodiments and comparative examples are provided.

[0033] Example 1 Lithium hydroxide and tetrabutyl titanate were weighed according to an atomic ratio of lithium to titanium of 4:5, and niobium hydroxide was weighed according to an atomic ratio of 1:99.

[0034] Tetrabutyl titanate was stirred in anhydrous ethanol to form solution A. Citric acid was dissolved in deionized water to form solution B. Solution B was then slowly added to solution A to obtain a mixed solution.

[0035] While continuously stirring the above mixed solution, weighed lithium hydroxide and niobium hydroxide are added to the mixed solution, and then ammonia water (NH3·H2O, 25% mass concentration) is added to adjust the pH value to 8. The temperature is raised to 70℃ and continuously stirred to allow the water in the mixed solution to evaporate and form a wet gel.

[0036] The wet gel was dried at 120°C for 10 hours to obtain the precursor powder.

[0037] The precursor powder was calcined in a muffle furnace at 300°C for 2 hours to initially decompose the citric acid in the precursor powder. The precursor powder was then calcined in air at 800°C for 4 hours to obtain Li₄Ti. 4.95 Nb 0.05 O 12 powder.

[0038] Example 2 Lithium carbonate and titanium dioxide are weighed according to an atomic ratio of lithium to titanium of 4:5, and niobium oxide is weighed according to an atomic ratio of 1:49.

[0039] Lithium carbonate is added to methanol and stirred to form solution A. Malic acid is dissolved in deionized water to form solution B. Then, solution B is slowly added to solution A to obtain a mixed solution.

[0040] While continuously stirring the above mixed solution, weighed lithium carbonate and niobium oxide are added to the mixed solution, and then ammonia water (NH3·H2O, 25% mass concentration) is added to adjust the pH value to 7.8. The temperature is raised to 60℃ and continuously stirred to allow the water in the mixed solution to evaporate and form a wet gel.

[0041] The wet gel was dried at 120°C for 10 hours to obtain the precursor powder.

[0042] The precursor powder was calcined in a muffle furnace at 200°C for 1 hour to initially decompose the citric acid in the precursor powder. The precursor powder was then calcined in air at 700°C for 2 hours to obtain Li₄Ti. 4.9 Nb 0.1 O 12 powder.

[0043] Example 3 Lithium nitrate and titanium tetrachloride were weighed according to an atomic ratio of lithium to titanium of 4:5, and niobium hydroxide was weighed according to an atomic ratio of niobium to titanium of 3:99.

[0044] Titanium tetrachloride is added to ethylenediamine and stirred to form solution A. Oxalic acid is dissolved in deionized water to form solution B. Then, solution B is slowly added to solution A to obtain a mixed solution.

[0045] While continuously stirring the above mixed solution, weighed lithium nitrate and niobium hydroxide are added to the mixed solution, and then ammonia water (NH3·H2O, 25% mass concentration) is added to adjust the pH value to 8.2. The temperature is raised to 50℃ and continuously stirred to allow the water in the mixed solution to evaporate and form a wet gel.

[0046] The wet gel was dried at 120°C for 10 hours to obtain the precursor powder.

[0047] The precursor powder was calcined in a muffle furnace at 400°C for 3 hours to preliminarily decompose the citric acid in the precursor powder. The precursor powder was then calcined in air at 900°C for 6 hours to obtain Li₄Ti. 4.85 Nb 0.15 O 12 powder.

[0048] Comparative Example The difference between this comparative example and Example 1 is that niobium hydroxide is not added, resulting in Li4Ti5O 12 powder.

[0049] The XRD patterns of the powder samples prepared in Examples 1-3 and the comparative examples are as follows: Figure 2 As shown, all samples exhibit good crystallinity, and all diffraction peaks are consistent with Li4Ti5O. 12 Corresponding to the standard crystal form card. With Nb 5+With increasing doping content, Li4Ti 4.9 Nb 0.1 O 12 and Li4Ti 4.85 Nb 0.15 O 12 In the curves, besides Li4Ti5O 12 The diffraction peaks also showed faint peaks for the impurity phase Nb₂O₅, indicating that there was no pure spinel structure at this point, and that a small amount of Nb was present. 5+ It did not enter the crystal lattice. The magnified XRD pattern of the (111) peak shows that the diffraction peak shifted to a higher angle when the Nb doping content increased from x=0 to x=0.1.

[0050] The first-cycle constant current charge-discharge curves of the powder samples prepared in Examples 1-3 and the comparative examples at a 0.1C rate are shown in the figure below. Figure 3 As shown, all discharge curves exhibit two flat voltage plateaus around 1.55V and 0.7V. The voltage plateau around 1.55V corresponds to the spinel structure of Li4Ti5O. 12 Li7Ti5O with rock salt structure 12 The two-phase reactions showed excellent agreement. It is noteworthy that although the discharge capacities of the three samples were roughly the same after the voltage was reduced to 0V, the doping levels differed. x =0.05 indicates a longer voltage plateau, suggesting that appropriate Nb doping is beneficial to Li4Ti5O 12 Increased capacity.

[0051] The cycling performance graphs of the powder samples prepared in Examples 1-3 and the comparative examples are shown below. Figure 4 As shown, after a 500-cycle period x =0 and x The discharge specific capacity at a doping concentration of 0.05 can be maintained at 71.7 mAh / g and 101.6 mAh / g, respectively, with capacity retention rates of 94.7% and 98.7%. This indicates that the doping concentration is high. x The capacity and cycling stability of 0.05 are superior to those of pure Li4Ti5O. 12 Materials. Comparative studies show that doping with a small amount of Nb is beneficial to Li4Ti5O. 12 The increased material capacity also contributes to the stability of high-rate, long-cycle cycling.

[0052] In summary, the niobium-doped lithium titanate material prepared by the method of this application exhibits a stable voltage plateau and excellent rate performance and cycle stability during charge and discharge. Furthermore, the method of this application is simple, requires no complex processes, is low-cost, pollution-free, easy to industrialize, requires abundant and inexpensive raw materials, consumes less energy during the reaction process, and is more environmentally friendly, making it a green, environmentally friendly, and efficient preparation method.

[0053] Finally, it should be noted that the above description is only a preferred embodiment of this application and is not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a niobium-doped lithium titanate material, characterized in that, include: A mixed solution was prepared using a titanium source, a dispersant, an organic acid, and deionized water. A lithium source and a niobium source are added to the mixed solution, the pH of the mixed solution is adjusted to 7.8-8.2 using ammonia, and the water in the mixed solution is evaporated to obtain a wet gel. The wet gel was dried to obtain a precursor powder. The precursor powder was calcined to obtain niobium-doped lithium titanate material.

2. The preparation method according to claim 1, characterized in that, The ratio of lithium to titanium atoms in the lithium source and the titanium source is 4:

5.

3. The preparation method according to claim 1, characterized in that, The titanium source is any one of tetrabutyl titanate, tetraisopropyl titanate, titanium dioxide, hydrated titanium dioxide, and titanium tetrachloride.

4. The preparation method according to claim 1, characterized in that, The lithium source is one or more of lithium hydroxide monohydrate, lithium hydroxide, lithium carbonate, lithium oxalate, and lithium nitrate.

5. The preparation method according to claim 1, characterized in that, The niobium source is Nb(OH)5 or Nb2O5.

6. The preparation method according to claim 1, characterized in that, Evaporating the water from the mixed solution includes: The mixed solution is heated to 50-70°C to evaporate the water.

7. The preparation method according to claim 1, characterized in that, The precursor powder is calcined, comprising: The precursor powder was subjected to a first calcination to preliminarily decompose the organic acids; The precursor powder was calcined a second time to obtain niobium-doped lithium titanate material.

8. The preparation method according to claim 7, characterized in that, The temperature of the first calcination is 200-400℃, and the calcination time is 1-3 hours.

9. The preparation method according to claim 7, characterized in that, The second calcination temperature is 700-900℃, and the calcination time is 2-6 hours.

10. A niobium-doped lithium titanate material prepared by the preparation method according to any one of claims 1-9, characterized in that, The general structural formula of the niobium-doped lithium titanate material is Li4Ti. 5-X Nb X O 12 , where 0 < x ≤ 0.

15.

11. The application of the niobium-doped lithium titanate material according to claim 10, characterized in that, The niobium-doped lithium titanate material is used as the negative electrode of a lithium-ion battery.

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