CN108417824B - A kind of preparation method of high performance lithium battery negative electrode material carbon-coated lithium titanate - Google Patents

Abstract

The invention discloses a preparation method of carbon-coated lithium titanate, which is a negative electrode material of a high-performance lithium battery. Specifically: at room temperature, CTAB was dissolved in isopropanol, and the magnetic stirring was uniform; then tetrabutyl titanate was added dropwise, and lithium hydroxide aqueous solution was added dropwise to the obtained mixed solution, and after stirring, the mixture was transferred. Put it in a stainless steel autoclave, keep it at 180°C for 36h to get a white precipitate; centrifugally wash it, dry it in an oven at 85°C, put the obtained precursor in a tube furnace, calcine it at 700-750°C for 6h, cool, grind, and get target product. The invention innovatively selects CTAB as the structure guiding agent, and directionally grows lithium titanate Li ₄ Ti ₅ O ₁₂ nanometer material with narrow particle size, forms a special structure of carbon-coated lithium titanate, and significantly enhances the lithium ions and electrons of lithium titanate. The transmission efficiency of the material itself will lead to better electrochemical properties such as rate performance and cycle performance of the material itself.

Description

A kind of preparation method of high performance lithium battery negative electrode material carbon-coated lithium titanate

technical field

The invention relates to the technical field of lithium ion batteries, in particular to a preparation method of carbon-coated lithium titanate as a negative electrode material of a high-performance lithium battery.

Background technique

The rapid development of human society with the progress of science and technology has also caused problems such as environmental pollution and resource depletion. Since the beginning of the 21st century, while enjoying the high-quality life brought about by scientific development, human beings have gradually realized the importance of developing new clean energy. Among the many new clean energy sources, lithium-ion batteries have attracted research due to their outstanding advantages such as small size, light weight, high energy density, good cycle stability, low self-discharge, no memory effect, safety and reliability, and no pollution. widespread attention.

As an important factor to improve battery energy, rate performance and cycle life, lithium-ion battery anode materials should be favored by researchers. In lithium-ion batteries, the developed anode materials mainly include carbon anode materials, germanium-based anode materials, silicon-based anode materials, titanium-based anode materials (Li ₄ Ti ₅ O ₁₂ ), etc., while titanium-based anode materials (Li ₄ Ti ₅ O ₁₂ ) has attracted extensive attention of researchers due to its inherent properties, spinel lithium titanate (Li ₄ Ti ₅ O ₁₂ ) has a flat and spacious charge-discharge platform at 1.55V (vs. Li/Li+), while In the process of charging and discharging, the material itself only has a volume change of 0.2%, which is a "zero-strain" negative electrode material, so it has excellent stability. However, spinel lithium titanate (Li ₄ Ti ₅ O ₁₂ ) has two serious shortcomings, such as poor conductivity and low transmission efficiency of lithium ions and electrons. Researchers have modified and optimized it based on these two shortcomings. At present, the modification and optimization methods of spinel lithium titanate anode materials are often used, including nano-ization to shorten the transport distance of Li ⁺ and electrons in the material; preparation of composite material systems to build a conductive network to improve the transport of Li ⁺ and electrons Ability; doping modification optimization, reducing the electrode polarization of the material at high rates, improving the electron transport capacity of the material, etc.

With the development of social economy and the progress of civilization, people's demand for energy is increasing day by day, and it is urgent to develop new green energy. As a green and efficient energy storage material, lithium-ion batteries have attracted extensive research interests of researchers. The anode material of lithium ion battery is one of the keys to ensure the high specific energy and cycle stability of lithium ion electrode. Some new titanium-based anode materials (such as Li ₄ Ti ₅ O ₁₂ ) have attracted widespread attention and great research interest, and are also promising for commercialization and application in next-generation high-performance lithium-ion batteries, thereby promoting lithium-ion The continuous development of batteries has contributed to alleviating the energy crisis and promoting the development of human civilization.

SUMMARY OF THE INVENTION

In order to solve the problem of low transmission efficiency of lithium ions and electrons in lithium titanate, a negative electrode material for lithium ion batteries, the purpose of the present invention is to provide a preparation method for carbon-coated lithium titanate, which is a negative electrode material for high performance lithium batteries, so as to further improve its performance. electrochemical performance.

The technical scheme adopted in the present invention is: a preparation method of carbon-coated lithium titanate as a negative electrode material of a high-performance lithium battery, comprising the following steps:

1) at room temperature, dissolve hexadecyltrimethylamine bromide (CTAB) in isopropanol, stir magnetically, mix well, add tetrabutyl titanate to obtain a mixed solution;

2) In the mixed solution obtained in step 1), add lithium hydroxide aqueous solution, and after stirring for 4 to 5 hours, transfer the reaction solution to a stainless steel autoclave, and react at 175 to 185 ° C for 36 to 45 hours to obtain a white precipitate, which is washed by centrifugation. After drying, the precursor was obtained by drying in an oven at 85°C;

3) The precursor obtained in step 2) is placed in a tube furnace, calcined at 600-750° C. for 6-7 hours in a nitrogen atmosphere, naturally cooled to room temperature, and ground to obtain the target product.

In the above-mentioned preparation method, lithium hydroxide and tetrabutyl titanate are prepared according to the molar ratio of lithium to titanium of 4.5:5.

In the above preparation method, the tetrabutyl titanate and the lithium hydroxide aqueous solution are added dropwise.

In the above preparation method, the calcination temperature is 700-750°C.

The beneficial effects of the present invention are:

The preparation method of carbon-coated lithium titanate as a high-performance lithium battery negative electrode material provided by the invention adopts an isopropanol-water composite solvothermal method, uses tetrabutyl titanate and LiOH·H ₂ O as raw materials, and uses isopropanol as raw materials. and water as solvent, react at 175～185℃ for 36～45h to obtain the precursor; sinter the precursor in nitrogen atmosphere at high temperature to obtain the target product Li ₄ Ti ₅ O ₁₂ /C. The nano Li ₄ Ti ₅ O ₁₂ /C material prepared by this method not only solves the problem of low transport efficiency of lithium ions and electrons of lithium titanate under the premise of maintaining the excellent characteristics of LTO, but also is particularly important. , its microstructure further increases the specific surface area of the material, thereby improving the electrochemical performance of the material. And the extremely simple one-step synthesis of isopropanol-water composite solvothermal method is particularly beneficial to the commercialization of LTO electrode materials and promote the development of lithium-ion battery anode materials.

In the present invention, CTAB is innovatively selected as the structure guiding agent in the preparation process, and the lithium titanate Li ₄ Ti ₅ O ₁₂ nanomaterial with narrow particle size is directionally grown, and the prepared nanomaterial has a large specific surface area and is in contact with the electrolyte. more active contact sites. At the same time, CTAB provides an appropriate amount of carbon source for the synthesis of the composite material. During the calcination process in an inert atmosphere, a small amount of carbon will be deposited on the surface of lithium titanate, which forms a special structure of carbon-coated lithium titanate, which significantly enhances the lithium titanate. The transport efficiency of lithium ions and electrons leads to better electrochemical properties such as the rate capability and cycle performance of the material itself.

Description of drawings

Fig. 1 is an XRD pattern of Li ₄ Ti ₅ O ₁₂ /C obtained by calcination at a temperature of 700-750°C.

Figure 2 is an XRD pattern of Li ₄ Ti ₅ O ₁₂ /C obtained by calcination at a temperature of 600-650°C.

Figure 3 is a SEM image of Li ₄ Ti ₅ O ₁₂ /C obtained by calcination at a temperature of 700-750°C;

Among them, a: 1 μm; b: 500 nm.

Detailed ways

The present invention is further explained below in conjunction with specific embodiments, but is not intended to limit the protection scope of the present invention.

The preparation method of carbon-coated lithium titanate for high-performance lithium battery negative electrode material provided by the present invention includes the following steps:

1) At room temperature, dissolve cetyltrimethylamine bromide (CTAB) in isopropanol, stir magnetically for 4h, and mix well; then add tetrabutyl titanate dropwise to obtain a mixed solution;

2) Dissolving lithium hydroxide in deionized water, and after magnetic stirring is completely dissolved, an aqueous solution of lithium hydroxide is obtained. The lithium hydroxide aqueous solution was added dropwise to the mixed solution obtained in step 1), and after stirring for 5 h, the mixture was transferred to a stainless steel autoclave, and reacted at 175-185 ° C for 36-45 h, and a white precipitate was obtained after hydrothermal treatment; Centrifuged and washed 5 times, and dried in an oven at 85 °C to obtain the precursor;

3) put the precursor obtained in step 2) into a tube furnace, calcined at 700-750° C. and 600-650° C. for 6 hours, naturally cooled to room temperature, and ground to obtain the target product Li ₄ Ti ₅ O ₁₂ /C.

Among them, in order to make the prepared material more excellent in electrochemical performance, the amount of CTAB in step 1) should be appropriate, that is, 10 mmol of tetrabutyl titanate and 9 mmol of lithium hydroxide are added per 0.2 g of CTAB. The molar ratio of lithium to titanium is 4.5:5, and the lithium needs to be in excess. The reason is that in the process of step 3) high temperature calcination, the lithium source will be lost, and if the lithium is not excessive, impurity TiO ₂ will be generated. Step 3) The purpose of high temperature calcination in nitrogen atmosphere is to convert the precursor into spinel lithium titanate Li ₄ Ti ₅ O ₁₂ negative electrode material under high temperature conditions, and CTAB will be converted into carbon source in an inert atmosphere.

In order to ensure that the raw material lithium hydroxide and tetrabutyl titanate can fully react, as an improvement of the technical solution, lithium hydroxide is added dropwise.

Wherein, in step 2), the stirring of LiOH·H ₂ O in deionized water is preferably magnetic stirring, so as to control the stirring speed and improve the degree of uniformity.

The calcination temperature in step 3) is preferably 700-750°C.

Example 1

A preparation method of carbon-coated lithium titanate as a negative electrode material for a high-performance lithium battery, comprising the following steps:

1) At room temperature, dissolve 0.2 g of hexadecyl trimethyl amine bromide (CTAB) in 30 mL of isopropanol, stir magnetically for 4 h, and mix well; then add 10 mmol of tetrabutyl titanate dropwise to obtain a mixed solution ;

2) Dissolve 9 mmol of lithium hydroxide in 15 mL of deionized water, and after the magnetic stirring is completely dissolved, an aqueous solution of lithium hydroxide is obtained. The lithium hydroxide aqueous solution was added dropwise to the mixed solution obtained in step 1), stirred for 5 h, then the mixture was transferred to a 100 mL stainless steel autoclave, and reacted at 175-185 ° C for 36 h, and a white precipitate was obtained after hydrothermal treatment; centrifugal washing 5 times, and dried in an oven at 85 °C to obtain the precursor;

3) The precursor obtained in step 2) is placed in a tube furnace, calcined at a temperature of 600-650° C. for 6 hours, naturally cooled to room temperature, and ground to obtain the target product Li ₄ Ti ₅ O ₁₂ /C.

Example 2

A preparation method of carbon-coated lithium titanate as a negative electrode material for a high-performance lithium battery, comprising the following steps:

1) At room temperature, dissolve 0.2 g of hexadecyl trimethyl amine bromide (CTAB) in 30 mL of isopropanol, stir magnetically for 4 h, and mix well; then add 10 mmol of tetrabutyl titanate dropwise to obtain a mixed solution ;

2) Dissolve 9 mmol of lithium hydroxide in 15 mL of deionized water, and after the magnetic stirring is completely dissolved, an aqueous solution of lithium hydroxide is obtained. The lithium hydroxide aqueous solution was added dropwise to the mixed solution obtained in step 1), stirred for 5 h, then the mixture was transferred to a 100 mL stainless steel autoclave, and reacted at 175-185 ° C for 36 h, and a white precipitate was obtained after hydrothermal treatment; centrifugal washing 5 times, and dried in an oven at 85 °C to obtain the precursor;

3) The precursor obtained in step 2) is placed in a tube furnace, calcined at a temperature of 700-750° C. for 6 hours, naturally cooled to room temperature, and ground to obtain the target product Li ₄ Ti ₅ O ₁₂ /C.

The Li ₄ Ti ₅ O ₁₂ /C obtained in Example 1 and Example 2 were examined by XRD and SEM, and the results are shown in FIG. 1 , FIG. 2 and FIG. 3 .

It can be seen from Figure 1 that the target product Li ₄ Ti ₅ O ₁₂ /C obtained in Example 1 has high purity and sharp XRD diffraction peaks. Compared with the standard lithium titanate card (JCPDS card number: 49-0207), there are no other impurity peaks. Appear.

It can be seen from FIG. 2 that the target product Li ₄ Ti ₅ O ₁₂ /C obtained in Example 2 has some TiO ₂ impurity peaks in the spectrum, and the XRD diffraction peaks are not sharp as shown in FIG. 1 .

It can be seen from FIG. 3 that the target product Li ₄ Ti ₅ O ₁₂ /C obtained in Example 1 has a narrow particle size and a regular morphology.

Example 3

For the materials obtained in Example 1 and Example 2 and the LTO materials bought in the general market, they were respectively used as the negative electrode material of the battery, and the lithium sheet was used as the counter electrode, which was assembled into a button battery, and the electrochemical performance was tested on it. The results are shown in Table 1.

Table 1 Comparison of electrochemical properties of different anode materials (charge-discharge rate 1C)

It can be seen from Table 1 that, compared with the common LTO negative electrode material, the electrochemical performance of the high-performance lithium battery negative electrode material lithium titanate Li ₄ Ti ₅ O ₁₂ /C synthesized by the method of the present invention is significantly improved, and it can be seen that 700 The electrochemical performance of the material obtained by calcination at a temperature of ~750 °C is much higher than that of the material obtained by calcination at a temperature of 600 ~ 650 °C; CTAB is innovatively selected as the material in this preparation process. The structure-directing agent, the directional growth of lithium titanate Li ₄ Ti ₅ O ₁₂ nanomaterials with narrow particle size, the nanomaterials have a large specific surface area and more active contact sites when they are in contact with the electrolyte, and the CTAB is The synthesis of the composite material provides an appropriate amount of carbon source. During the calcination process in an inert atmosphere, a small amount of carbon will be deposited on the surface of lithium titanate, which forms a special structure of carbon-coated lithium titanate, which significantly enhances the lithium ion and lithium titanate. The transfer efficiency of electrons leads to better electrochemical properties such as rate capability and cycle performance of the material itself.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (3)

1. a preparation method of high-performance lithium battery negative material carbon-coated lithium titanate, is characterized in that, comprises the steps: 1) At room temperature, dissolve cetyltrimethylamine bromide in isopropanol, stir magnetically, mix well, and then add tetrabutyl titanate dropwise to obtain a mixed solution; 2) In the mixed solution obtained in step 1), add lithium hydroxide aqueous solution dropwise, and after stirring for 4 to 5 h, transfer the reaction solution to a stainless steel autoclave, and react at 175 to 185 ° C for 36 to 45 h, the obtained white Precipitate, wash by centrifugation, and dry in an oven at 85°C to obtain the precursor; Add 10 mmol of tetrabutyl titanate and 9 mmol of lithium hydroxide per 0.2 g of cetyltrimethylamine bromide; 3) The precursor obtained in step 2) is placed in a tube furnace, calcined at 600-750° C. for 6-7 h in a nitrogen atmosphere, cooled to room temperature naturally, and ground to obtain the target product. 2. according to the preparation method of claim 1, it is characterized in that, lithium hydroxide and tetrabutyl titanate are batched according to lithium-titanium molar ratio of 4.5:5. 3. The preparation method according to claim 1, wherein the calcination temperature is 700-750°C.

Images