阅读说明：本技术 一种钛酸锂负极材料及其制备方法 (Lithium titanate negative electrode material and preparation method thereof ) 是由 赖春艳 蒋宏雨 李佳炜 许晗 陆翔昊 于 2020-03-25 设计创作，主要内容包括：本发明涉及一种钛酸锂负极材料及其制备方法,该负极材料的原料包括,钛源、锂源和表面活性剂,所述的钛源、锂源和表面活性剂的质量比为(75-79):(15-20):(0.5-10)；按质量比,将钛源、锂源、表面活性剂和水混合后进行水热反应,再煅烧后,最终得到钛酸锂负极材料。与现有技术相比,本发明具有独特结构优势,不仅具有优异的循环稳定性、高倍率性能和低温性能,还具有制备简单、耗能少、绿色和易于产业化的有益效果。(The invention relates to a lithium titanate negative electrode material and a preparation method thereof, wherein the raw materials of the negative electrode material comprise a titanium source, a lithium source and a surfactant, and the mass ratio of the titanium source to the lithium source to the surfactant is (75-79) to (15-20) to (0.5-10); mixing a titanium source, a lithium source, a surfactant and water according to a mass ratio, carrying out hydrothermal reaction, and calcining to obtain the lithium titanate negative electrode material. Compared with the prior art, the invention has unique structural advantages, excellent cycle stability, high rate performance and low-temperature performance, and has the beneficial effects of simple preparation, low energy consumption, greenness and easiness in industrialization.)

1. A lithium titanate negative electrode material is characterized in that raw materials of the negative electrode material comprise a titanium source, a lithium source and a surfactant, wherein the mass ratio of the titanium source to the lithium source to the surfactant is (75-79): (15-20): 0.5-10).

2. A lithium titanate negative electrode material as claimed in claim 1, wherein the titanium source includes one or more of titanium carbide, tetrabutyl titanate, or titanium dioxide.

3. The lithium titanate negative electrode material as claimed in claim 2, wherein the titanium carbide is obtained by reacting titanium aluminum carbide with hydrofluoric acid.

4. The lithium titanate negative electrode material as claimed in claim 3, wherein the mass ratio of the carbon, aluminum and titanium to the hydrofluoric acid is 1 (60-120), the concentration of the hydrofluoric acid is 40-50 ω t%, the reaction time is 12-72h, and the temperature is 20-50 ℃.

5. The lithium titanate negative electrode material as claimed in claim 3, wherein the hydrofluoric acid is formed by reacting a fluoride comprising one or more of lithium fluoride, potassium fluoride, or sodium fluoride with an acid comprising one or more of hydrochloric acid, sulfuric acid, or nitric acid.

6. A lithium titanate negative electrode material as claimed in claim 1, wherein said lithium source comprises lithium hydroxide.

7. A lithium titanate negative electrode material as claimed in claim 1, wherein the surfactant includes one or more of sodium dodecylbenzenesulfonate, cetyltrimethylammonium bromide, or polyvinylpyrrolidone.

8. The preparation method of the lithium titanate negative electrode material as claimed in claim 1, characterized in that the method comprises mixing a titanium source, a lithium source, a surfactant and water according to a mass ratio, performing a hydrothermal reaction, and calcining to obtain the lithium titanate negative electrode material.

9. The preparation method of the lithium titanate negative electrode material as claimed in claim 8, wherein the mass ratio of the titanium source to the water is 1 (20-30), the temperature of the hydrothermal reaction is 100-200 ℃, and the time is 6-24 h.

10. The method as claimed in claim 8, wherein the calcination temperature is 500-650 ℃ and the calcination time is 2-6 h.

Technical Field

The invention relates to the field of preparation of lithium ion battery materials, in particular to a lithium titanate negative electrode material and a preparation method thereof.

Background

As a new type of chemical energy storage device, lithium ion batteries have become the most important and advanced batteries due to their advantages of long cycle life, high energy density, no memory effect, etc. Currently, carbon materials are the most commonly used commercial negative electrode materials for lithium ion batteries. However, due to the "lithium precipitation" phenomenon and the safety problem caused by the volume expansion of the carbon material during the charging and discharging processes, the development of lithium ion batteries urgently requires some novel negative electrode materials which are safe, reliable and long in service life.

Lithium titanate (L i)₄Ti₅O₁₂) Is a spinel crystal with Fd3m space group and cubic symmetry, which is a promising negative electrode material due to its outstanding "no volume change" property, the volume of the unit cell only changes 0.2% during charge and discharge, and more importantly, lithium titanate has a relatively high potential (relative to L i/L i)⁺1.55V), which can avoid the generation of lithium dendrites, however, L i is deficient in electrons due to the 3d electron shell in the Ti atom₄Ti₅O₁₂Very poor conductivity (10)^-13S·cm^-1) Low lithium diffusion coefficient (10)^-9-10^-13cm²·s^-1) To solve these problems, L i with a special morphology was developed₄Ti₅O₁₂And downsizing to the nanometer scale is considered a common and effective strategy.

International journal of Advanced Energy Materials, entitled "Ultrathin L i₄Ti₅O₁₂A nano sheet Based High-Rate and L ong-Cycle L ife L i-Ion Batteries (DOI:10.1002/aenm.201700950) is prepared by ultrasonic treatment of TiO₂The powder (2.0g, Degussa, P25) was dispersed in NaOH solution (80M L, 10 μ M.) the dispersion obtained was transferred to a 100M L stainless steel autoclave and kept at 120 ℃ for 24 hours, and then subjected to centrifugation to give NaTO NW. and subsequently, NaT was addedO NW (0.2g) was dispersed in NaOH solution (38.5M L, 2M) and then H was added to the solution₂O₂(1.5m L, 30%). the solution was transferred to a 50m L stainless steel autoclave and maintained at 150 ℃ for 12 hours to prepare HNaTO₃(0.05. mu.M) solution, stirred for 12 hours to exchange Na by hydrogen ion⁺Ion, repeating twice and obtaining HHTO, finally, dispersing HHTO in L iOH solution (40M L, 0.3M) by ultrasonic treatment, and transferring the solution TO a 50M L stainless steel autoclave and maintaining at 120 ℃ for 24 hours, separating the product by centrifugation, washing three times with water, and drying in an oven, and finally, after calcining at 400 ℃ for 4 hours, obtaining a H L TO-NS sample, which has excellent electrochemical properties.

Therefore, based on the research, the development of a simple and rapid novel lithium titanate preparation process has important practical significance.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide a lithium titanate negative electrode material which has unique structural advantages, excellent cycle stability, high rate performance and low-temperature performance, simple preparation, low energy consumption, greenness and easy industrialization and a preparation method thereof.

The purpose of the invention can be realized by the following technical scheme:

a lithium titanate negative electrode material is characterized in that raw materials of the negative electrode material comprise a titanium source, a lithium source and a surfactant, wherein the mass ratio of the titanium source to the lithium source to the surfactant is (75-79): (15-20): 0.5-10). The particle size of the negative electrode material is 3-5 μm.

The surface of the titanium carbide is charged with negative charges by adding the surfactant, and the lithium source can be better riveted on the surface of the titanium carbide through electrostatic adsorption. The purpose of this is to obtain a product with more excellent morphology, and the unique morphology structure is the main reason for the excellent performance.

Further, the titanium source comprises one or more of titanium carbide, tetrabutyl titanate or titanium dioxide, preferably a double titanium source consisting of 0.5-5 wt% of titanium carbide and 95-99.5 wt% of tetrabutyl titanate, and also preferably a double titanium source consisting of 0.5-5 wt% of titanium carbide and 95-99.5 wt% of titanium dioxide.

Further, the titanium carbide is obtained by reacting titanium aluminum carbide with hydrofluoric acid.

Further, the mass ratio of the carbon-aluminum-titanium to the hydrofluoric acid is 1 (60-120), the concentration of the hydrofluoric acid is 40-50 omega t%, the reaction time is 12-72h, and the temperature is 20-50 ℃.

Further, the hydrofluoric acid is generated by reacting fluoride with acid, the fluoride comprises one or more of lithium fluoride, potassium fluoride or sodium fluoride, and the acid comprises one or more of hydrochloric acid, sulfuric acid or nitric acid.

Further, the lithium source includes lithium hydroxide.

Further, the surfactant comprises one or more of sodium dodecyl benzene sulfonate, cetyl trimethyl ammonium bromide or polyvinylpyrrolidone.

The preparation method of the lithium titanate negative electrode material comprises the steps of mixing a titanium source, a lithium source, a surfactant and water according to a mass ratio, carrying out hydrothermal reaction, and calcining to obtain the lithium titanate negative electrode material.

Further, the method is characterized in that the mass ratio of the titanium source to the water is 1 (20-30), the temperature of the hydrothermal reaction is 100-200 ℃, and the time is 6-24 h.

Further, the calcining temperature is 500-650 ℃, and the time is 2-6 h.

Compared with the conventional reported preparation method of lithium titanate, a single titanium source such as lithium titanate or titanium dioxide is used as a reactant, titanium carbide is additionally added to serve as a second titanium source, and a dual-titanium source is uniquely adopted as a reactant to prepare pure-phase lithium titanate through a one-step hydrothermal method.

Compared with a single titanium source, the double titanium source has unique advantages that titanium carbide is used as both the titanium source and the reaction substrate, no template is required to be additionally added, no complex synthesis mode is required, and a simple one-step hydrothermal method is adopted. Because the added titanium carbide is used as a titanium source and is simultaneously used as a reaction substrate, the anionic surfactant is added to ensure that the surface of the titanium carbide is negatively charged, lithium hydroxide is further added to be used as a lithium source, lithium ions generated by hydrolysis can be effectively riveted on the surface of the titanium carbide under the electrostatic action, and finally, a second titanium source is added to further react with the lithium source to generate the lithium titanate precursor. The purpose of this is to obtain hollow microsphere lithium titanate assembled by dense nanoplates, further improve the cycling stability of the material, and have structural advantages compared with lithium titanate synthesized by a single titanium source, as can be seen from the comparison between fig. 2 and fig. 3.

Compared with the prior art, the invention has the following advantages:

(1) according to the invention, a dual titanium source is uniquely adopted as a reaction raw material, wherein titanium carbide is used as a part of the titanium source and also as a reaction substrate, an anionic surfactant is added to make the surface of the titanium carbide carry negative charges, then a lithium source is induced to be attached to the surface of the titanium carbide, the product is optimized in morphology and structure, the product is modified through morphology regulation, and no coating action exists;

(2) the invention simply adopts a one-pot method for reaction, has simple steps, avoids using high-cost alcohol reagents and harsh protective gas atmosphere, and has simple method, unique product structure and excellent performance;

(3) the lithium titanate negative electrode material prepared by the invention has a hollow microsphere assembled by compact nanoplates in a particle shape, the size is only 3-5 mu m, the first-circle discharge specific capacity at 5 ℃ is up to 174mAh/g, and the lithium titanate negative electrode material has excellent electrochemical cycling stability.

Drawings

Fig. 1 is a 10 k-fold SEM image of the lithium titanate negative electrode material obtained in example 1;

fig. 2 is an SEM image of 80k times of the lithium titanate negative electrode material obtained in example 1;

fig. 3 is an SEM image of 80k times of lithium titanate negative electrode material obtained by the prior art;

FIG. 4 is a TEM image of the lithium titanate negative electrode material obtained in example 1;

fig. 5 is an XRD pattern of the lithium titanate negative electrode material obtained in example 1;

fig. 6 is a cycle chart of a button cell assembled by the lithium titanate negative electrode material obtained in example 1.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments.