阅读说明：本技术 一种硫掺杂二氧化钛纳米纤维的制备方法 (Preparation method of sulfur-doped titanium dioxide nano-fiber ) 是由 李星 高楠 于 2019-11-27 设计创作，主要内容包括：本发明公开了一种硫掺杂二氧化钛纳米纤维的制备方法,本发明中以钛酸四丁酯为主要原料溶于N,N-二甲基甲酰胺、乙醇和乙酸的混合溶剂中,加入聚乙烯吡咯烷酮,得到前驱体混合物溶液；在一定的电压与流率下,利用同轴技术进行静电纺丝；将静电纺丝产品进行烧结得到TiO<Sub>2</Sub>纳米管,将TiO<Sub>2</Sub>纳米管与升华硫混合进行熔融渗硫,将渗硫后的TiO<Sub>2</Sub>纳米管加入到钛酸四丁酯的乙醇溶液中,加入氨水使钛酸四丁酯水解产生TiO<Sub>2</Sub>包覆在硫单质和TiO<Sub>2</Sub>纳米管的外部,从而形成硫掺杂二氧化钛纳米纤维。本发明制得的硫掺杂二氧化钛纳米纤维具有良好的电化学性能,在整个制备过程中,操作简单,原料成本低,设备投资少,适合批量生产。(The invention discloses a preparation method of sulfur-doped titanium dioxide nano-fibers, tetrabutyl titanate is taken as a main raw material and dissolved in a mixed solvent of N, N-dimethylformamide, ethanol and acetic acid, polyvinylpyrrolidone is added to obtain a precursor mixture solution; under certain voltage and flow rate, electrostatic spinning is carried out by utilizing a coaxial technology; sintering the electrostatic spinning product to obtain TiO 2 Nanotube of TiO 2 Mixing the nanotubes with sublimed sulfurMelting sulfurizing, and sulfurizing the sulfurized TiO 2 Adding the nanotube into an ethanol solution of tetrabutyl titanate, and adding ammonia water to hydrolyze the tetrabutyl titanate to generate TiO 2 Coating sulfur and TiO 2 The exterior of the nanotube, thereby forming a sulfur-doped titanium dioxide nanofiber. The sulfur-doped titanium dioxide nanofiber prepared by the method has good electrochemical performance, is simple to operate, low in raw material cost and low in equipment investment in the whole preparation process, and is suitable for batch production.)

1. A preparation method of sulfur-doped titanium dioxide nano-fibers is characterized by comprising the following steps:

(1) dissolving a proper amount of tetrabutyl titanate in a mixed solvent of DMF, ethanol and acetic acid in a volume ratio of 2:2:1, adding a proper amount of PVP, and stirring for 3 hours to form a solution A;

(2) dissolving PVP in a mixed solvent with the volume ratio of DMF, ethanol and acetic acid being 2:2:1, and stirring for 3 hours to form a solution B;

(3) the two solutions A and B are subjected to a voltage of 17-19 kV, the receiving distance is 15-20 cm, the flow rate is 0.6mL h^-1Under the condition (1), carrying out coaxial electrostatic spinning, wherein the solution B is an inner layer solution, and the solution A is an outer layer solution;

(4) placing the obtained electrostatic spinning product in an oven, and drying for 12h at 100 ℃;

(5) transferring the dried electrostatic spinning product into a muffle furnace, and sintering at 750-900 ℃ for 5h to obtain TiO₂A nanotube;

(6) adding TiO into the mixture₂Mixing the nanotubes and sublimed sulfur in a mass ratio of 2:3, putting the mixture into a closed container, and carrying out melting and sulfurizing at 155 ℃;

(7) sulfurizing the sulfurized TiO₂Adding the nanotube into an ethanol solution of tetrabutyl titanate, and dropwise adding ammonia water to hydrolyze the tetrabutyl titanate to generate TiO₂Coating sulfur and TiO₂The sulfur-doped titanium dioxide nanofiber is obtained outside the nanotube;

the DMF is N, N-dimethylformamide;

the PVP is K-120 type polyvinylpyrrolidone;

the mass ratio of the tetrabutyl titanate to the PVP in the solution A is 1: 1;

the solvents, reagents or raw materials for the reaction are all chemically pure.

2. The sulfur-doped titanium dioxide nanofiber prepared by the preparation method of claim 1, wherein the nanofiber is used as a lithium battery positive electrode material and has a specific first discharge capacity of 957.9mAh g^-1。

Technical Field

The invention belongs to the field of material chemistry, and particularly relates to a preparation method of sulfur-doped titanium dioxide nano fibers.

Background

Lithium-sulfur batteries are considered to be one of the most promising new high-performance battery systems due to their advantages of high theoretical energy density, cheap raw materials, environmental friendliness, and the like. Although the research on sulfur-based batteries has been in history for decades and has made remarkable progress in recent years, the lithium-sulfur batteries are not a small distance from the actual practical use due to some special reaction properties of the electrochemical system consisting of elemental sulfur and metallic lithium and the matching problem of polysulfide with the electrolyte. At present, the development and application of lithium-sulfur batteries still face a plurality of technical problems (n.jayarakash et al, angel Chem inteedit, 50(2011) 5904-: 1) sulfur has extremely poor conductivity and the conductivity is only 5 multiplied by 10 at 25 DEG C^-30S/cm, which is a typical electronic and ionic insulator; the discharge product lithium sulfide is also an insulator, and the lithium sulfide cannot be completely and reversibly converted into sulfur, so that the electrochemical activity is easily lost; 2) an intermediate product polysulfide generated by elemental sulfur in the charging and discharging process is easily dissolved in the electrolyte, so that the loss of partial electrode active substances is caused, and meanwhile, the viscosity of the electrolyte is increased due to the large dissolution of the polysulfide, so that the migration resistance of lithium ions in the electrolyte is increased, the ionic conductivity of the electrolyte is deteriorated, and the electrode dynamic process of a sulfur electrode is influenced; 3) the phenomenon that the polysulfide shuttles back and forth between the positive electrode and the negative electrode to perform self-discharge is a phenomenon specific to the lithium-sulfur battery, namely the shuttle effect, and the shuttle effect influences the completion of normal charging of the battery and reduces the coulomb efficiency of the battery. In addition, the long-chain polysulfide reacts on the surface of the negative electrode to cause the corrosion phenomenon of the surface of the negative electrode, and the electrochemical performance of the lithium electrode is influenced; 4) density of elemental sulfur (2.07 g/cm)³) And the density of the discharge product lithium sulfide (1.66g/cm³) If the difference is large, the volume of the material can change obviously during charging and discharging, and the volume of the negative electrode can be reduced because lithium is consumed during reaction. The repeated change of the volumes of the anode and cathode materials can damage the physical structure of the electrode to a certain extent, so that microcracks are generated, and finally, the powdering phenomenon can occur to cause the failure of the electrode.

In order to solve the problems and challenges of the lithium sulfur battery, researchers have conducted intensive research from the aspect of the positive electrode. The positive electrode material has been the most critical part of the battery performance research. For sulfur-containing cathode materials, research has focused primarily on the preparation of sulfur-based composites. The matrix material incorporated in the composite material is required to satisfy two basic requirements: firstly, the matrix material has excellent conductivity to make up the insulativity of sulfur; secondly, the elemental sulfur can be uniformly dispersed on the matrix material by a certain composite preparation method, so that the utilization rate of the active substance is improved; thirdly, the introduced matrix material has the functions of containing and confining sulfur and polysulfide, and can inhibit the shuttle effect. The compounding of the nanometer transition metal oxide material and elemental sulfur is also an important research direction of the lithium-sulfur battery anode material. The transition metal oxide is used as an additive and directly added into elemental sulfur, and can play a role in improving sulfur conductivity, inhibiting shuttle effect and improving cycle performance to a certain extent after being prepared into a composite material with sulfur. In order to solve the problems of low utilization rate of sulfur anode active substances, poor cycle performance and the like, TiO is prepared by an electrostatic spinning method₂Nanotubes and then infiltrating elemental sulfur into TiO₂Inside and outside of nanotubes, finally with TiO₂Coated with TiO₂Sulfur outside the nanotubes, thereby forming a multilayer fiber structure.

Disclosure of Invention

The invention provides a preparation method of sulfur-doped titanium dioxide nano-fibers, which aims to solve the problems of low utilization rate of sulfur positive active substances, poor cycle performance and the like, further improve the sulfur conductivity and inhibit shuttle effect.

The technical scheme adopted by the invention for solving the technical problems is as follows: a preparation method of sulfur-doped titanium dioxide nano-fibers specifically comprises the following steps:

(1) adding appropriate amount of tetrabutyl titanate (C)₁₆H₃₆O₄Ti) is dissolved in a mixed solvent of DMF, ethanol and acetic acid with the volume ratio of 2:2:1, a proper amount of PVP is added, and the mixture is stirred for 3 hours to form a solution A;

(2) dissolving PVP in a mixed solvent of N, N' -Dimethylformamide (DMF), ethanol and acetic acid in a volume ratio of 2:2:1, and stirring for 3 hours to form a solution B;

(3) the two solutions A and B are subjected to a voltage of 17-19 kV, the receiving distance is 15-20 cm, the flow rate is 0.6mL h^-1Under the condition (1), carrying out coaxial electrostatic spinning, wherein the solution B is an inner layer solution, and the solution A is an outer layer solution;

(4) placing the obtained electrostatic spinning product in an oven, and drying for 12h at 100 ℃;

(5) transferring the dried electrostatic spinning product into a muffle furnace, and sintering at 750-900 ℃ for 5h to obtain TiO₂A nanotube;

(6) adding TiO into the mixture₂Mixing the nanotubes and sublimed sulfur in a mass ratio of 2:3, putting the mixture into a closed container, and carrying out melting and sulfurizing at 155 ℃;

(7) sulfurizing the sulfurized TiO₂Adding the nanotube into an ethanol solution of tetrabutyl titanate, and dropwise adding ammonia water to hydrolyze the tetrabutyl titanate to generate TiO₂Coating sulfur and TiO₂The sulfur-doped titanium dioxide nanofiber is obtained outside the nanotube;

the DMF is N, N-dimethylformamide;

the PVP is K-120 type polyvinylpyrrolidone;

the mass ratio of the tetrabutyl titanate to the PVP in the solution A is 1: 1;

the solvents, reagents or raw materials for the reaction are all chemically pure.

Compared with the prior art, the sulfur-doped titanium dioxide nanofiber synthesized by the method has the following characteristics:

by adopting the electrostatic spinning technology and combining the melting sulfurization and hydrolysis chemical deposition methods, the synthesized material has a tubular and multilayer nanofiber structure, and is uniform in particle size and high in stability; the first discharge specific capacity of the sulfur-doped titanium dioxide nanofiber serving as the lithium battery anode material is 957.9mAh g^-1。

Drawings

FIG. 1 is an XRD pattern of nanofibers made in example 1;

FIG. 2 is an SEM image of nanofibers made from example 1;

FIG. 3 shows that the nano-fiber prepared in example 1 is used as the positive electrode material of a lithium ion battery at 200mA g^-1Current density of (a).

Detailed Description

The technical solution of the present invention is not limited to the specific embodiments listed below, and includes any combination of the specific embodiments, and the present invention is further described in detail with reference to the following examples.