Preparation method of fluorinated niobium titanium oxygen hollow sphere and application thereof in lithium ion battery

Abstract

The application relates to a preparation method of fluorinated niobium-titanium oxygen hollow spheres and application of the fluorinated niobium-titanium oxygen hollow spheres in lithium ion batteries. The method comprises the following steps: preparing silica microspheres, preparing niobium-titanium oxygen hollow spheres by taking the prepared silica microspheres as templates. A niobium-titanium oxygen material (SiO2@TiNb2O7) loaded on microspherical titanium dioxide is prepared by a solvothermal method. Then, the SiO2@TiNb2O7 is dissolved in a hydrofluoric acid (30 wt%) solution, and is transferred into a reaction kettle to obtain fluorinated niobium-titanium oxygen hollow sphere materials. The preparation method realizes the fluorination of niobium-titanium oxygen and the preparation of hollow spheres by a one-step method. The hollow sphere structure improves the specific surface area, can bear a larger real current density, is favorable for the fast deintercalation of lithium ions, the fluorination improves the electronic conductivity of the niobium-titanium oxygen material, greatly improves the rate performance, and the fluorination can passivate the electrode surface, inhibit the occurrence of interface side reactions, and further inhibit the gas production behavior. The preparation method can be used in the field of high-power niobium-titanium oxygen-based lithium ion batteries.

Description

Technical Field

[0001] The present invention belongs to the field of secondary lithium-ion batteries, and in particular relates to a preparation method of fluorinated niobium-titanium oxide hollow spheres and an application thereof in lithium-ion batteries. Background Art

[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 has been widely used due to its low cost and high specific capacity (372 mAh g -1 ) has become a commonly used negative electrode material in commercial secondary lithium-ion batteries. However, graphite exhibits a low operating voltage (0.1V vs Li + / Li), resulting in permanent consumption of lithium and easily forming lithium dendrites on the graphite surface, causing safety problems. Among the negative electrode intercalation materials, spinel lithium titanate has a higher working voltage (1.55V vs Li + / Li) ensures safety and a long cycle life. However, the theoretical specific capacity of spinel lithium titanate is relatively low (only 175mAh g -1 ), poor electrical conductivity, which hinders its practical application.

[0003] In recent years, niobium-based oxides have attracted considerable attention as high-power negative electrode materials for lithium-ion batteries and have the potential to replace lithium titanium spinel. As a typical intercalation negative electrode material, the excellent electrochemical performance of niobium titanate is mainly due to its unique structure, in which niobium (Nb) and titanium (Ti) atoms are located in the center of NbO6 and TiO6 octahedra, respectively, in a disordered arrangement. In addition, the NbO6 octahedron and the TiO6 octahedron are connected by edges and vertices to form an open tunnel-like gap that can accommodate the transmission of lithium ions. The insertion and extraction of lithium ions are relatively easy, so it has excellent rate performance. Niobium titanate not only has the advantages of conventional lithium titanate materials in terms of cycle stability and long life, but also has the advantages of TiO6. 3+ / Ti 4+ 、Nb 4+ / Nb 5+ and Nb 3+ / Nb 4+ It has a higher theoretical specific capacity (387.6mA h g-1) and a working potential similar to that of lithium titanate (1.6V vs Li + / Li), effectively preventing the formation of lithium dendrites and the reductive decomposition of the electrolyte. This significantly improves safety compared to traditional batteries. However, niobium titanium oxide also has some drawbacks, including low electronic and ionic conductivity. Therefore, a method to simultaneously enhance both electronic and ionic conductivity of niobium titanium oxide is urgently needed. Summary of the Invention

[0004] The application aims to solve the problem of low electronic and ionic conductivity of niobium titanium oxygen materials, and provides a preparation method of fluorinated niobium titanium oxygen hollow spheres and application thereof in lithium ion batteries.

[0005] To achieve the above-mentioned purpose, the technical scheme adopted by the application is as follows:

[0006] The application provides a preparation method of fluorinated niobium titanium oxygen hollow spheres.

[0007] Step one: preparing silica microspheres, 150-300 mL of anhydrous ethanol and 20-100 mL of deionized water are sequentially added into a glass container; under stirring, 5-20 mL of ammonia solution is added dropwise into the above solution, and stirring is performed for 30 min to ensure sufficient mixing; under room temperature, 20 g of tetraethyl orthosilicate (TEOS) is gradually added into the above mixture, and stirring is continuously performed under magnetic stirring for 24 h; the white suspension obtained by stirring is taken out, centrifuged at a speed of 8000-10000 r / min for three times, and then transferred to an oven at 65 ℃ for drying to obtain silica microspheres;

[0008] Step two: preparing niobium titanium oxygen hollow spheres by using the prepared silica microspheres as a template, the silica microspheres are dispersed in anhydrous ethanol; under magnetic stirring, ammonia is added into the above dispersed suspension, and stirring is continuously performed for 30 min; 1.02 g of tetrabutyl titanate and 1.62 g of NbCl5 are added into the above suspension, and magnetic stirring is performed for 2 h; the obtained solution is transferred to a 100 mL Teflon-lined stainless steel autoclave, and kept at 180 ℃ for a period of time; after the autoclave is cooled to room temperature, the precipitate is collected by centrifugation to obtain a precursor material; the precursor material is transferred to a box furnace and calcined in an air atmosphere to obtain SiO2@TiNb2O7;

[0009] Step three: the above SiO2@TiNb2O7 is dissolved in a hydrofluoric acid (30 wt%) solution, stirring is performed for 30 min, the solution is transferred to a polytetrafluoroethylene-lined reaction kettle, and kept at 180 ℃ for a period of time; the obtained product is washed with ethanol and deionized water for multiple times to remove impurities, the sample is placed in a vacuum drying box and dried at 60 ℃ for 12 h to obtain fluorinated niobium titanium oxygen hollow sphere material.

[0010] Further, in step two, the adding amount of the silica microspheres and ammonia is 40-60 mg: 0.5-1 mL.

[0011] Further, in step two, the Teflon-lined stainless steel autoclave is kept at 180℃ for 12-36h.

[0012] Further, in step two, the calcination temperature of the box furnace is 800-1600℃, more preferably, the calcination temperature is 800℃, 850℃, 1000℃.

[0013] Further, in step two, the calcination time of the box furnace is 6-24h.

[0014] Further, in step three, the polytetrafluoroethylene-lined reaction kettle is kept at 180℃ for 6-14h.

[0015] The fluorinated niobium-titanium-oxygen hollow sphere prepared by the above preparation method is applied as a negative electrode material in a lithium ion battery, wherein the negative electrode of the lithium ion battery is the fluorinated niobium-titanium-oxygen hollow sphere material; the fluorinated niobium-titanium-oxygen hollow sphere material, a conductive agent and a binder are dispersed in NMP solvent according to a mass ratio of 96%:2%:2% to obtain a negative electrode slurry, the slurry is coated on a negative electrode current collector, dried, rolled, punched and cut to obtain a negative electrode sheet, and then a button cell is assembled.

[0016] Compared with the prior art, the present application has the following beneficial effects: in the present application, the fluorination of niobium-titanium-oxygen and the preparation of hollow spheres are realized by one-step method, the hollow sphere structure improves the specific surface area, can withstand a larger real current density, and is beneficial to the rapid deintercalation of lithium ions, and the fluorination improves the electronic conductivity of the niobium-titanium-oxygen material, greatly improves the rate performance, and the fluorination can passivate the electrode surface, inhibit the occurrence of interface side reactions, and inhibit the gas production phenomenon, and the preparation method can be used in the field of high-power niobium-titanium-oxygen lithium ion batteries. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 A schematic diagram of the prepared fluorinated niobium-titanium-oxygen hollow sphere;

[0018] Figure 2 An SEM diagram of the prepared fluorinated niobium-titanium-oxygen hollow sphere;

[0019] Figure 3 A cycle diagram of the fluorinated niobium-titanium-oxygen hollow sphere prepared in Example 1 and the sample 1C of the comparative example under 10C;

[0020] Figure 4 A rate performance diagram of the fluorinated niobium-titanium-oxygen hollow sphere prepared in Example 1 and the sample of the comparative example;

[0021] Figure 5 A cycle diagram of the fluorinated niobium-titanium-oxygen hollow sphere prepared in Example 1 and the sample 10C of the comparative example. DETAILED DESCRIPTION

[0022] The technical solutions of the present application are further described below in combination with the drawings and examples, but are not limited thereto. Any modification or equivalent replacement of the technical solutions of the present application without departing from the spirit and scope of the present application shall be covered in the protection scope of the present application.

[0023] Example 1

[0024] A preparation method of fluorinated niobium titanium oxygen hollow spheres and its application in lithium ion batteries, comprising the following steps:

[0025] Step one: 200 mL of anhydrous ethanol and 50 mL of deionized water were sequentially added to a beaker. Next, 6 mL of ammonia solution was added dropwise to the above solution under stirring conditions, and stirring was continued for 30 minutes to ensure thorough mixing. Then, 20 g of tetraethyl orthosilicate (TEOS) was gradually added to the above mixture under room temperature conditions, and the stirring was continued for 24 h under magnetic stirring. Subsequently, the white suspension obtained by stirring was removed and centrifuged three times at a speed of 8000-10000 r / min, and then transferred to an oven at 65°C for drying to obtain silica microspheres.

[0026] Step two: The prepared silica microspheres were used as templates to prepare niobium titanium oxygen hollow spheres: 50 mg of silica microspheres were weighed and dispersed in anhydrous ethanol. 0.8 mL of NH3·H2O was added to the above dispersed suspension under magnetic stirring, and the stirring was continued for 30 min. 1.02 g of tetrabutyl titanate and 1.62 g of NbCl5 were added to the above suspension, and the magnetic stirring was continued for 2 h. Then, the obtained solution was transferred to a 100 mL Teflon-lined stainless steel autoclave, and kept at 180°C for 24 h. After the autoclave was cooled to room temperature, the precipitate was collected by centrifugation to obtain a precursor material. Subsequently, it was transferred to a box furnace and calcined at 850°C for 12 h in an air atmosphere to obtain SiO2@TiNb2O7.

[0027] Step three: The SiO2@TiNb2O7 was dissolved in a hydrofluoric acid (30 wt%) solution, stirred for 30 min, and transferred to a polytetrafluoroethylene-lined reaction kettle, and kept at 180°C for 12 h. The obtained product was washed with ethanol and deionized water several times to remove impurities, and the sample was placed in a vacuum drying oven at 60°C for 12 h to obtain fluorinated niobium titanium oxygen hollow sphere material.

[0028] Step four: The obtained niobium titanium oxygen hollow sphere material was dispersed in N-methyl pyrrolidone solvent according to a mass ratio of 96%:2%:2% with conductive agent (acetylene black, carbon nanotube) and binder (PVDF) to obtain negative electrode slurry, and the slurry was stirred for 10 h by planetary stirring. The slurry was coated on the negative electrode current collector, dried, rolled, and punched to obtain a negative electrode sheet, and then a button cell was assembled.

[0029] Example 2

[0030] The difference between this example and Example 1 is that in Step 1, 60 mL of deionized water is used, which can obtain silica microspheres with larger particle size, and then obtain Nb-Ti-O materials with greater hollow degree, thereby enhancing the specific surface area of the material.

[0031] Example 3

[0032] The difference between the fluorinated hollow Nb-Ti-O material prepared in this example and Example 1 is that in Step 2: using the prepared silica microspheres as a template to prepare Nb-Ti-O hollow spheres: first, 50 mg of silica microspheres is weighed and dispersed in anhydrous ethanol. Second, 0.8 mL of NH3·H2O is added to the above dispersed suspension under magnetic stirring, and stirring is continued for 30 min. Then, 1.02 g of tetrabutyl titanate and 1.62 g of NbCl5 are added to the above suspension, and magnetic stirring is performed for 2 h. Then, the obtained solution is transferred to a 100 mL Teflon-lined stainless steel autoclave, and kept at 180°C for 24 h. After the autoclave is cooled to room temperature, the precipitate is collected by centrifugation to obtain a precursor material. Subsequently, it is transferred to a box furnace and calcined at 850°C for 6 h in an air atmosphere to obtain SiO2@TiNb2O7.

[0033] Example 4

[0034] The difference between the fluorinated hollow Nb-Ti-O material prepared in this example and Example 1 is that in Step 2: using the prepared silica microspheres as a template to prepare Nb-Ti-O hollow spheres: first, 50 mg of silica microspheres is weighed and dispersed in anhydrous ethanol. Second, 0.8 mL of NH3·H2O is added to the above dispersed suspension under magnetic stirring, and stirring is continued for 30 min. Then, 1.02 g of tetrabutyl titanate and 1.62 g of NbCl5 are added to the above suspension, and magnetic stirring is performed for 2 h. Then, the obtained solution is transferred to a 100 mL Teflon-lined stainless steel autoclave, and kept at 180°C for 24 h. After the autoclave is cooled to room temperature, the precipitate is collected by centrifugation to obtain a precursor material. Subsequently, it is transferred to a box furnace and calcined at 850°C for 6 h in an air atmosphere to obtain SiO2@TiNb2O7.

[0035] Comparative Example 1

[0036] Comparative Example 1 is a pure phase spherical niobium titanium oxygen material without hollow sphere structure design and fluorinated surface treatment. The specific preparation method is as follows: 1.02 g of tetrabutyl titanate and 1.62 g of NbCl5 are added to 30-50 mL of ethanol and magnetically stirred for 2 h. Then, the obtained solution is transferred to a 100 mL Teflon-lined stainless steel autoclave, which is kept at 180 °C for 24 h. After the autoclave is cooled to room temperature, the precipitate is collected by centrifugation to obtain a precursor material. Subsequently, it is transferred to a box furnace and calcined at 850 °C for 12 h in an air atmosphere to obtain a pure phase TiNb2O7.

[0037] The fluorinated niobium titanium oxygen hollow spheres obtained in Example 1 are applied to lithium ion battery negative electrode materials, Figure 3 The cycle comparison chart of the fluorinated niobium titanium oxygen hollow spheres prepared in Example 1 and the sample 1C of the comparative example shows that after the improvement, the capacity at 1C rate is improved and the cycle is more stable, which is mainly due to the large specific surface area of the fluorinated niobium titanium oxygen hollow spheres and the fluorinated electrode surface, which improves the electrochemical performance of the niobium titanium oxygen material.

[0038] The rate performance and 10C large rate cycle performance of the samples prepared in Examples 1-4 and the comparative example are tested, as shown in Figure 4 、 5 After modification, the rate performance of the niobium titanium oxygen electrode is obviously improved. At 0.2C, 0.5C, 1C, 2C, 5C, 10C, 20C and 40C, the samples of Examples 1-4 all exhibit better rate performance than the samples of the comparative example. When the current density returns to 0.5C, the example samples exhibit excellent reversibility. In addition, the cycle stability at 10C large rate is obviously improved, and the cycle stability of Examples 1-4 is better than that of the samples of the comparative example, which is mainly due to the hollow sphere structure design, which enhances the specific surface area of the niobium titanium oxygen material, fully contacts with the electrolyte, shortens the lithium ion transmission distance, and the fluorinated surface enhances the electronic conductivity, passivates the electrode / electrolyte interface, and reduces the occurrence of side reactions.

Claims

1. A method for preparing fluorinated niobium titanium oxide hollow spheres, characterized in that: The method is: Step 1: Preparation of silica microspheres: 150-300 mL of anhydrous ethanol and 20-100 mL of deionized water were added to a glass container in sequence; 5-20 mL of ammonia solution was added dropwise to the above solution under stirring and stirred for 30 minutes to ensure thorough mixing; 20 g of tetraethyl orthosilicate was gradually added to the above mixture at room temperature and stirred continuously for 24 hours under magnetic stirring; the white suspension obtained by stirring was taken out and centrifuged three times at a speed of 8000-10000 r / min, and then transferred to a 65°C oven for drying to obtain silica microspheres; Step 2: Using the prepared silica microspheres as a template, a niobium-titanium oxide spherical material with a silica template as the core center was prepared: the silica microspheres were dispersed in anhydrous ethanol; ammonia water was added to the dispersed suspension under magnetic stirring and the stirring was continued for 30 minutes; 1.02 g of tetrabutyl titanate and 1.62 g of NbCl5 were added to the suspension and magnetic stirring was continued for 2 hours; the resulting solution was transferred to a Teflon-lined stainless steel autoclave and maintained at 180°C for a period of time; after the autoclave was cooled to room temperature, the precipitate was collected by centrifugation to obtain a precursor material; the precursor material was transferred to a box furnace and calcined in an air atmosphere to obtain SiO2@TiNb2O7; Step 3: Dissolve the above SiO2@TiNb2O7 in 30wt% hydrofluoric acid solution, stir for 30 min, transfer to a polytetrafluoroethylene-lined reactor, and keep warm at 180°C for a period of time. Wash the obtained product with ethanol and deionized water several times to remove impurities. Place the sample in a vacuum drying oven at 60°C and dry it for 12 h to obtain fluorinated niobium titanium oxide hollow sphere material.

2. The method for preparing fluorinated niobium titanium oxide hollow spheres according to claim 1, characterized in that: In step 2, the amount of silica microspheres and ammonia water added is 40-60 mg: 0.5-1 mL.

3. The method for preparing fluorinated niobium titanium oxide hollow spheres according to claim 1, characterized in that: In step 2, the Teflon-lined stainless steel autoclave is kept at 180°C for 12 to 36 hours.

4. The method for preparing fluorinated niobium titanium oxide hollow spheres according to claim 1, wherein: In step 2, the calcination temperature of the box furnace is 800-1600°C.

5. The method for preparing fluorinated niobium titanium oxide hollow spheres according to claim 1, wherein: In step 2, the calcination time in the box furnace is 6 to 24 hours.

6. The method for preparing fluorinated niobium titanium oxide hollow spheres according to claim 1, characterized in that: In step 3, the polytetrafluoroethylene-lined reactor was kept at 180 °C for 6 to 14 h.

7. Use of the fluorinated hollow niobium titanium oxide spheres prepared by the preparation method according to any one of claims 1 to 6 as negative electrode materials in lithium ion batteries.

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