阅读说明：本技术 一种硫掺杂钛酸锂/氧化石墨烯复合材料、制备方法及其应用 (Sulfur-doped lithium titanate/graphene oxide composite material, and preparation method and application thereof ) 是由 任玉荣 梁康 于 2019-09-05 设计创作，主要内容包括：本发明涉及一种硫掺杂钛酸锂/氧化石墨烯复合材料、制备方法及其应用,它包括以下步骤：(a)将钛源溶于溶液中,搅拌得钛源溶液；(b)将锂源溶于去离子水中,搅拌得锂盐溶液；(c)将所述锂盐溶液添加到所述钛源溶液中,搅拌得混合溶液；(d)向所述混合溶液中添加PVP、氧化石墨烯,超声分散后进行水热反应,经离心、干燥得钛酸锂/氧化石墨烯前驱体；(e)将所述钛酸锂/氧化石墨烯前驱体在还原性气氛下进行烧结,得钛酸锂/氧化石墨烯复合材料；(f)将所述钛酸锂/氧化石墨烯复合材料与硫源混合,在还原性气氛下烧结得硫掺杂钛酸锂/氧化石墨烯复合材料。这样制得的钠离子电池具有容量高等优点,能用作钠离子电池负极的活性材料。(The invention relates to a sulfur-doped lithium titanate/graphene oxide composite material, a preparation method and application thereof, and the sulfur-doped lithium titanate/graphene oxide composite material comprises the following steps: (a) dissolving a titanium source in the solution, and stirring to obtain a titanium source solution; (b) dissolving a lithium source in deionized water, and stirring to obtain a lithium salt solution; (c) adding the lithium salt solution into the titanium source solution, and stirring to obtain a mixed solution; (d) adding PVP (polyvinyl pyrrolidone) and graphene oxide into the mixed solution, performing ultrasonic dispersion, performing hydrothermal reaction, centrifuging and drying to obtain a lithium titanate/graphene oxide precursor; (e) sintering the lithium titanate/graphene oxide precursor in a reducing atmosphere to obtain a lithium titanate/graphene oxide composite material; (f) and mixing the lithium titanate/graphene oxide composite material with a sulfur source, and sintering in a reducing atmosphere to obtain the sulfur-doped lithium titanate/graphene oxide composite material. The sodium ion battery prepared in the way has the advantages of high capacity and the like, and can be used as an active material of a negative electrode of the sodium ion battery.)

1. A preparation method of a sulfur-doped lithium titanate/graphene oxide composite material is characterized by comprising the following steps:

(a) dissolving a titanium source in the solution, and stirring to obtain a titanium source solution;

(b) dissolving a lithium source in deionized water, and stirring to obtain a lithium salt solution;

(c) adding the lithium salt solution into the titanium source solution, and stirring to obtain a mixed solution;

(d) adding PVP (polyvinyl pyrrolidone) and graphene oxide into the mixed solution, performing ultrasonic dispersion, performing hydrothermal reaction, centrifuging and drying to obtain a lithium titanate/graphene oxide precursor;

(e) sintering the lithium titanate/graphene oxide precursor in a reducing atmosphere to obtain a lithium titanate/graphene oxide composite material;

(f) and mixing the lithium titanate/graphene oxide composite material with a sulfur source, and sintering in a reducing atmosphere to obtain the sulfur-doped lithium titanate/graphene oxide composite material.

2. The preparation method of the sulfur-doped lithium titanate/graphene oxide composite material according to claim 1, characterized by comprising the following steps: in the step (a), the titanium source is tetrabutyl titanate or titanium sulfate, and the solution is deionized water or a mixture of deionized water and glycerol.

3. The preparation method of the sulfur-doped lithium titanate/graphene oxide composite material according to claim 1, characterized by comprising the following steps: in the step (b), the lithium source is lithium hydroxide or lithium acetate.

4. The preparation method of the sulfur-doped lithium titanate/graphene oxide composite material according to claim 1, characterized by comprising the following steps: the ratio of the titanium source to the lithium source to the PVP to the graphene oxide is 1-1.2 mol: 4-4.8 mol: 100-400 mg: 10-40 mg.

5. The preparation method of the sulfur-doped lithium titanate/graphene oxide composite material according to claim 1, characterized by comprising the following steps: in the step (d), the hydrothermal reaction temperature is 180-220 ℃ and the time is 6-12 h; the drying method is freeze drying.

6. The preparation method of the sulfur-doped lithium titanate/graphene oxide composite material according to claim 1, characterized by comprising the following steps: in the step (e) and the step (f), the reducing atmosphere is Ar and H₂And (4) mixing the atmosphere.

7. The preparation method of the sulfur-doped lithium titanate/graphene oxide composite material according to claim 1, characterized by comprising the following steps: the sintering temperature in step (e) is higher than the sintering temperature in step (f); in the step (e), the sintering temperature is 400-600 ℃, and the time is 4-6 h; in the step (f), the sintering temperature is 300-500 ℃, and the time is 1-3 h.

8. The preparation method of the sulfur-doped lithium titanate/graphene oxide composite material according to claim 1, characterized by comprising the following steps: in the step (f), the sulfur source is thiourea or sublimed sulfur, and the mass ratio of the sulfur source to the lithium titanate/graphene oxide composite material is 2-5: 1.

9. a sulfur-doped lithium titanate/graphene oxide composite material, characterized in that it is prepared by the preparation method of any one of claims 1 to 8.

10. The use of the sulfur-doped lithium titanate/graphene oxide composite material of claim 9, wherein: it is used as the active material of the negative electrode of the sodium ion battery.

Technical Field

The invention belongs to the field of negative electrode materials, relates to a graphene oxide composite material, and particularly relates to a sulfur-doped lithium titanate/graphene oxide composite material, and a preparation method and application thereof.

Background

Because of the limited storage of lithium in the earth's crust, it cannot be satisfied at the same timeThe application of the lithium ion battery in the fields of electric automobiles and large-scale energy storage is needed, so that other cheap energy storage systems are needed to be developed and applied to the field of large-scale energy storage as a substitute of the lithium ion battery. The sodium element is widely distributed in the earth crust, has high abundance (2.75%) and is ranked the sixth among all elements. Meanwhile, sodium and lithium belong to the same main group elements and have similar physicochemical properties, so that the sodium-ion battery has a similar electrochemical reaction mechanism and equivalent electrochemical performance as a lithium-ion battery. Therefore, the sodium ion battery has good application prospect in the fields of low cost and large-scale energy storage. However, due to the ionic radius of sodium ionsGreater than the radius of lithium ionThe diffusion kinetics of sodium ions in the electrode is slower than that of lithium ions, which provides certain challenges for the development of high-performance sodium-embedded anode and cathode materials.

Spinel type lithium titanate (Li)₄Ti₅O₁₂(ii) a LTO) is considered to be a sodium ion battery negative electrode material with a commercial application prospect due to its good cycle performance, high safety, high reliability in mass production, excellent sodium storage capacity, and relatively high oxidation-reduction potential. However, lithium titanates also have disadvantages, such as Ti in lithium titanate⁴⁺The 3d orbit of the lithium titanate is lack of electrons, so that the conductivity of the lithium titanate is very low, and simultaneously, the ion diffusion coefficient of sodium ions in lithium titanate is 10 due to the larger ionic radius of the sodium ions^-16cm²s^-1) Far lower than the diffusion coefficient (10) of lithium ions in lithium titanate^-9～10^-13cm²s^-1). Therefore, appropriate modification of lithium titanate is required to improve its electrochemical performance in sodium ion batteries.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a preparation method of a sulfur-doped lithium titanate/graphene oxide composite material.

In order to achieve the purpose, the invention adopts the technical scheme that: a preparation method of a sulfur-doped lithium titanate/graphene oxide composite material comprises the following steps:

(a) dissolving a titanium source in the solution, and stirring to obtain a titanium source solution;

(b) dissolving a lithium source in deionized water, and stirring to obtain a lithium salt solution;

(c) adding the lithium salt solution into the titanium source solution, and stirring to obtain a mixed solution;

(d) adding PVP (polyvinyl pyrrolidone) and graphene oxide into the mixed solution, performing ultrasonic dispersion, performing hydrothermal reaction, centrifuging and drying to obtain a lithium titanate/graphene oxide precursor;

(e) sintering the lithium titanate/graphene oxide precursor in a reducing atmosphere to obtain a lithium titanate/graphene oxide composite material;

(f) and mixing the lithium titanate/graphene oxide composite material with a sulfur source, and sintering in a reducing atmosphere to obtain the sulfur-doped lithium titanate/graphene oxide composite material.

Preferably, in step (a), the titanium source is tetrabutyl titanate or titanium sulfate, and the solution is deionized water or a mixture of deionized water and glycerol.

Preferably, in step (b), the lithium source is lithium hydroxide or lithium acetate.

Optimally, the ratio of the titanium source to the lithium source to the PVP to the graphene oxide is 1-1.2 mol: 4-4.8 mol: 100-400 mg: 10-40 mg.

Optimally, in the step (d), the hydrothermal reaction temperature is 180-220 ℃ and the time is 6-12 h; the drying method is freeze drying.

Optimally, in the step (e) and the step (f), the reducing atmosphere is Ar and H₂And (4) mixing the atmosphere.

Optimally, the sintering temperature in step (e) is higher than the sintering temperature in step (f); in the step (e), the sintering temperature is 400-600 ℃, and the time is 4-6 h; in the step (f), the sintering temperature is 300-500 ℃, and the time is 1-3 h.

Optimally, in the step (f), the sulfur source is thiourea or sublimed sulfur, and the mass ratio of the sulfur source to the lithium titanate/graphene oxide composite material is 2-5: 1.

the invention further aims to provide the sulfur-doped lithium titanate/graphene oxide composite material, which is prepared by the preparation method.

The invention further aims to provide application of the sulfur-doped lithium titanate/graphene oxide composite material, which is used as an active material of a negative electrode of a sodium-ion battery.

Due to the application of the technical scheme, compared with the prior art, the invention has the following advantages: according to the preparation method of the sulfur-doped lithium titanate/graphene oxide composite material, lithium titanate and graphene oxide are compounded in situ by a simple hydrothermal method, so that the lithium titanate/graphene oxide composite material has good conductivity; meanwhile, the intrinsic conductivity of the lithium titanate/graphene oxide composite material can be improved by embedding sulfur into the lithium titanate/graphene oxide composite material, so that high specific discharge capacity can be obtained, and the prepared sodium ion battery has the advantages of high capacity and the like and can be used as an active material of a cathode of the sodium ion battery.

Drawings

FIG. 1 is an XRD diffractogram of the S-LTO/rGO composite made in example 1;

FIG. 2 is an XPS plot of S-LTO/rGO composite made in example 1;

FIG. 3 is a FT-IR plot of the S-LTO/rGO composite made in example 1;

FIG. 4 is a graph of battery cycle performance for the S-LTO/rGO composite made in example 1;

FIG. 5 is a graph of the rate of S-LTO/rGO composite made in example 1.

Detailed Description

The invention relates to a preparation method of a sulfur-doped lithium titanate/graphene oxide composite material, which comprises the following steps: (a) dissolving a titanium source in the solution, and stirring to obtain a titanium source solution; (b) dissolving a lithium source in deionized water, and stirring to obtain a lithium salt solution; (c) adding the lithium salt solution into the titanium source solution, and stirring to obtain a mixed solution; (d) adding PVP (polyvinyl pyrrolidone) and graphene oxide into the mixed solution, performing ultrasonic dispersion, performing hydrothermal reaction, centrifuging and drying to obtain a lithium titanate/graphene oxide precursor; (e) sintering the lithium titanate/graphene oxide precursor in a reducing atmosphere to obtain a lithium titanate/graphene oxide composite material; (f) and mixing the lithium titanate/graphene oxide composite material with a sulfur source, and sintering in a reducing atmosphere to obtain the sulfur-doped lithium titanate/graphene oxide composite material. Lithium titanate and graphene oxide are compounded in situ by a simple hydrothermal method, so that the lithium titanate/graphene oxide composite material has good conductivity; meanwhile, the intrinsic conductivity of the lithium titanate/graphene oxide composite material can be improved by embedding sulfur into the lithium titanate/graphene oxide composite material, so that high specific discharge capacity can be obtained, and the prepared sodium ion battery has the advantages of high capacity and the like and can be used as an active material of a cathode of the sodium ion battery.

In the step (a), the titanium source is tetrabutyl titanate or titanium sulfate; the solution is deionized water or a mixture of deionized water and glycerol (due to weak acidity of glycerol hydrolysis, Ti can be effectively inhibited⁴⁺Hydrolysis of (2); specifically, the ratio of deionized water to glycerol may be 1: 3). In the step (b), the lithium source is lithium hydroxide or lithium acetate. Specifically, the raw material ratios are preferably as follows: the ratio of the titanium source to the lithium source to the PVP to the graphene oxide is 1-1.2 mol: 4-4.8 mol: 100-400 mg: 10-40 mg. In the step (d), the hydrothermal reaction temperature is 180-220 ℃ and the time is 6-12 h; the drying method is freeze drying. In the step (e) and the step (f), the reducing atmosphere is Ar and H₂Mixed atmosphere (specific volume ratio Ar: H)₂9: 1). The sintering temperature in step (e) is higher than the sintering temperature in step (f); in the step (e), the sintering temperature is 400-600 ℃, and the time is 4-6 h; in the step (f), the sintering temperature is 300-500 ℃, and the time is 1-3 h. In step (f), the sulfur source is thiourea or sublimed sulfur (S can be made by using thiourea^2-In the embedded material, an S-Ti bond is better formed), the mass of the lithium titanate/graphene oxide composite material and the sulfur source is 1: 2 to 5.

The sulfur-doped lithium titanate/graphene oxide composite material prepared by the method can be used as an active material of a negative electrode of a sodium-ion battery, and specifically comprises the following steps: according to the following mass ratio (active substance)(namely, the sulfur-doped lithium titanate/graphene oxide composite material is abbreviated as S-LTO/rGO): conductive agent (Super P): binder (CMC-Na) ═ 8: 1: 1) grinding active substance, conductive agent and binder uniformly, coating on current collector (copper foil), cutting into disc with diameter of 12mm, drying in vacuum drying oven at 80 deg.C for 8 hr, and matching with metal sodium as counter electrode and 1.0M NaClO₄Taking the mixture as electrolyte (the solvent is EC: DMC: EMC mixed according to the volume ratio of 1: 1: 1, FEC with the solvent volume of 5%) and glass fiber as a diaphragm, assembling the mixture in a glove box filled with argon to prepare a CR2016 button cell, and carrying out electrochemical performance test on a Xinwei test cabinet (the voltage range is 0.01-2.7V, the current density is 0.05-2A g)^-1)。

The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings: