KR101451901B1 - Method for preparing of spinel lithium titanium oxide nanorods for negative electrode of lithium secondary battery - Google Patents

Abstract

The present invention relates to a method of manufacturing a spinel lithium titanium oxide nanorod active material for a lithium secondary battery. A method of manufacturing a spinel lithium titanium oxide nanorod active material of a lithium secondary battery according to the present invention comprises the steps of: (S1) preparing a titanate nanorod rod by hydrothermal synthesis from titanium oxide (TiO2) powder; (S2) preparing lithium titanate (Li-TiO) nanorods by ion exchange from the titanate nanorods and the lithium precursor; (S3) heat treating the lithium titanate nanorods; .
According to the spinel lithium titanium oxide nanofiber anode active material of the lithium secondary battery manufactured according to the manufacturing method of the present invention, it is possible to increase the contact area between the electrolyte solution and the conductive agent through the large surface area per unit volume of the spinel lithium titanium oxide nanofiber, Can greatly contribute to improvement of electric conductivity and ion conductivity. In addition, from the viewpoint of the process, it is possible to additionally obtain an effect of improving the lithium ion diffusion due to the reduction of the activation energy barrier of lithium ion diffusion caused by the residual metal such as sodium generated through the ion exchange method.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of preparing a spinel lithium titanium oxide nanorod anode active material for a lithium secondary battery,

The present invention relates to a method of manufacturing a negative electrode active material of a lithium secondary battery, and more particularly, to a method of manufacturing a nanowire-shaped spinel lithium titanium oxide negative electrode active material.

The secondary battery is used as a small-sized, high-performance energy source for a large-capacity power storage battery such as an electric car or a battery power storage system, and a portable electronic device such as a mobile phone, a camcorder, and a notebook.

Recently, the secondary battery market has been demanding high energy density and high output power of the power supply device due to the combined use of the existing portable electronic devices. For the green home and the hybrid vehicle (HEV or PHEV) Applications are rapidly expanding to mid- to large-sized power supplies.

Such a secondary battery as a next-generation large-sized power supply requires highly enhanced specifications in terms of high energy density, high output, and longevity stability.

Thus, there are typically a spinel lithium-titanium oxide (Li ₄ Ti ₅ O ₁₂₎ as a negative electrode material for next-generation batteries, the spinel lithium-titanium oxide The main advantage of the (Li ₄ Ti ₅ O ₁₂₎ is intercalation of Li ⁺ with no parent Structure / de-intercalation (zero-strain) characteristics and thus high life stability as an anode material.

However, as a disadvantage, the spinel lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ) has an electron conductivity of +4 (3d ⁰ configuration) in the initial state, Exhibit very low insulting character. Therefore, it is an important issue to be improved in order to satisfy high output characteristics as a next generation power supply device.

The inventors of the present invention found that by providing a large surface area per unit volume of spinel lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ) through the preparation of nanorods, the contact area increase of the electrolyte and the conductive agent and the lithium ion diffusion distance decreased, The present inventors have completed the present invention in view of the fact that the electrochemical characteristics at a high current density, which is a disadvantage of Li ₄ Ti ₅ O ₁₂ , can be improved.

Korean Patent Laid-Open No. 10-2012-0015293 Domestic registered patent No. 10-2009-0011219

In order to solve the problems of the prior art as described above, the present invention improves the electrical conductivity and the ion conductivity by increasing the contact area between the electrolyte and the conductive agent and reducing the lithium ion diffusion distance through the large surface area per unit volume of the spinel lithium titanium oxide nanorods And a method for manufacturing a spinel lithium titanium oxide nanorod active material for a lithium secondary battery.

It is another object of the present invention to provide a spinel lithium titanium oxide nanorod active material, a negative electrode and a lithium secondary battery including the same, which are manufactured using the above manufacturing method.

In order to accomplish the above object, the present invention provides a method for producing a titanate nanorod, comprising: (S1) preparing a titanate nanorod rod by hydrothermal synthesis from a titanium oxide (TiO ₂ ) powder; (S2) preparing lithium titanate (Li-TiO) nanorods by ion exchange from the titanate nanorods and the lithium precursor; (S3) heat treating the lithium titanate. The method of manufacturing a spinel lithium titanium oxide nanorod active material of the lithium secondary battery according to claim 1,

In the step S1, the titanium oxide powder may be mixed with a basic aqueous solution or an acidic aqueous solution to prepare a first mixed solution, followed by heating and reacting.

The acidic aqueous solution is preferably an aqueous solution of an acidic substance selected from the group consisting of hydrochloric acid, sulfuric acid and nitric acid.

The basic aqueous solution is preferably an aqueous solution of a basic substance selected from the group consisting of sodium hydroxide, potassium hydroxide and calcium hydroxide.

The titanium oxide powder is preferably added in an amount of 0.1 to 20 parts by weight based on 100 parts by weight of the basic aqueous solution or the acidic aqueous solution.

The heating of the first mixed solution is preferably performed at a temperature of 110 to 300 ° C.

The step S2 may include mixing a lithium precursor, the titanate nanorods prepared in the step S1, and a solvent to prepare a second mixed solution.

The step S2 may include heating and reacting the second mixed solution.

The heating of the second mixed solution is preferably performed at 110 to 300 ° C.

Examples of the solvent used for preparing the second mixed solution include water, ethanol, methanol, propanol, puthanol, isopropyl alcohol (IPA), acetone , Hexane (Hexane), tetrahydrofuran (THF), and toluene.

The lithium precursor may, for example lithium hydroxide (LiOH), lithium metal (Li), lithium acetate (CH ₃ COOLi), lithium chloride (LiCl), lithium nitrate (LiNO _3), butyllithium (C ₄ H ₉ Li), methyl lithium (CH ₃ Li), and ethyl lithium (C ₂ H ₅ Li).

The lithium precursor may be added in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the solvent.

In the preparation of the second mixed solution, 0.1 to 10 parts by weight of the titanate nanorods prepared in the step S1 is added to 100 parts by weight of the solvent.

The heat treatment in step S3 is preferably performed at a temperature of 300 to 800 ° C.

The present invention also provides a spinel lithium titanium oxide nanofiber anode active material of a lithium secondary battery produced by the production method of the present invention.

The present invention also provides a negative electrode of a lithium secondary battery comprising the negative electrode active material.

The present invention also provides a lithium secondary battery including the negative electrode.

According to the spinel lithium titanium oxide nanofiber anode active material of the lithium secondary battery manufactured according to the manufacturing method of the present invention, it is possible to increase the contact area between the electrolyte solution and the conductive agent through the large surface area per unit volume of the spinel lithium titanium oxide nanofiber, Can greatly contribute to improvement of electric conductivity and ion conductivity.

In addition, from the viewpoint of the process, it is possible to additionally obtain an effect of improving the lithium ion diffusion due to the reduction of the activation energy barrier of lithium ion diffusion caused by the residual metal such as sodium generated through the ion exchange method.

1 is a graph showing the results of analysis of the structure of spinel lithium titanium oxide nanorods (Li ₄ Ti ₅ O ₁₂ Nanorods) of Example 1. FIG.
FIG. 2 (a) is a graph showing a transmission electron microscopic analysis result of the spinel lithium titanium oxide nanorods (Li ₄ Ti ₅ O ₁₂ Nanorods) of Example 1, (b) is a graph showing the results of spinel lithium titanium oxide nano- (Li ₄ Ti ₅ O ₁₂ Nanorods) according to the present invention is a graph showing the result of a high-resolution transmission electron microscopic analysis.
FIG. 3A is a graph showing the results of charge / discharge characteristics of a half-cell manufactured using the spinel lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ) nanorods prepared in Example 1 as a negative electrode active material at 1 to 3 V with C / Fig.
FIG. 3B is a graph showing the results of 50 cycles of charging / discharging a half-cell manufactured using the spinel lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ) nanorods prepared in Example 1 as a negative electrode active material at 1 to 3 V to C / Discharge characteristics of the battery.
FIG. 3C shows a polarization phenomenon caused by overvoltage during charging of a half-cell made using the spinel lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ) nanorods prepared in Example 1 as an anode active material at 1 to 3 V to 0.1 C (GITT), and the measurement results are shown in the graph.
FIG. 3D is a graph showing the results of charge / discharge of a half-cell manufactured using the spinel lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ) nanorods prepared in Example 1 as an anode active material at 1 to 3 V at C / 10, C / And the results of measurement of the charge-discharge characteristics are shown.

Hereinafter, the present invention will be described in detail.

The present invention relates to a method for producing a negative electrode active material of a spinel lithium titanium oxide nanorod (Li ₄ Ti ₅ O ₁₂ Nanorods) of a lithium secondary battery, and a spinel lithium titanium oxide nanorod having a one-dimensional structure by hydrothermal synthesis and ion exchange .

A method of manufacturing a spinel lithium titanium oxide nanorod active material of a lithium secondary battery according to the present invention includes the steps of: (S1) preparing a titanate nanorod by hydrothermal synthesis from a titanium oxide (TiO ₂ ) powder; (S2) preparing lithium titanate (Li-TiO) nanorods by ion exchange from the titanate nanorods and the lithium precursor; (S3) heat treating the lithium titanate nanorods.

According to the above manufacturing method, first, titanate nanorods are prepared by hydrothermal synthesis from a titanium oxide (TiO ₂ ) powder (S 1).

More specifically, the titanium oxide powder is mixed with a basic aqueous solution or an acidic aqueous solution to prepare a first mixed solution, followed by heating and reacting the first mixed solution in the hydrothermal synthesis vessel.

If the product, titanate nanorod, is formed through the above process, washing and by-product removal may be performed.

As the acidic aqueous solution, hydrochloric acid, sulfuric acid or nitric acid aqueous solution may be used.

As the basic aqueous solution, sodium hydroxide, potassium hydroxide or calcium hydroxide may be used.

When an acidic aqueous solution is used in the hydrothermal synthesis process, a proton titanate (H-TiO) nanorod is produced. On the other hand, when a basic aqueous solution is used, the metal titanate (Na-TiO), potassium titanate (K-TiO), calcium titanate (Ca-TiO) ) Nanorods and proton-titanate (H-TiO) nanorods.

The concentrations of the acidic aqueous solution and the basic aqueous solution are preferably 1 to 20M, respectively. When the upper limit of the above range is exceeded, there is a problem that it is difficult to form a nanorod structure, and when the lower limit of the above range is exceeded, it is difficult to react with the titanium precursor.

The titanium oxide powder is preferably added in an amount of 0.1 to 20 parts by weight based on 100 parts by weight of the basic aqueous solution or the acidic aqueous solution. When the upper limit of the above range is exceeded, it is difficult to obtain a uniform nanorod structure, and when the lower limit of the above range is exceeded, sufficient pressure can not be provided in the reaction.

The heating of the first mixed solution is preferably performed at a temperature of 110 to 300 ° C. When the upper limit of the above range is exceeded, there is a problem that it is difficult to obtain a uniform nanorod structure due to agglomeration, and when the lower limit of the above range is exceeded, sufficient pressure can not be provided in the reaction, I can not.

Next, lithium titanate (Li-TiO) nanorods are prepared from the titanate nanorods and the lithium precursor by ion exchange (S2).

This step includes the steps of: preparing a second mixed solution by mixing a lithium precursor, the titanate nanorods prepared in the step S1, and a solvent; And heating and reacting the second mixed solution in a hydrothermal synthesis vessel. Through such a process, lithium titanate nanorods are formed by ion exchange.

When the product, lithium titanate nanorod, is formed through the above process, washing and by-product removal may be performed.

The heating of the second mixed solution is preferably performed at 110 to 300 ° C. If the upper limit of the above range is exceeded, there is a problem that excessive Li ions are contained in the structure and Li4Ti5O12 phase can not be obtained, and when the lower limit of the above range is exceeded, there is a problem that the ion- It is not desirable.

Examples of the solvent used for preparing the second mixed solution include water, ethanol, methanol, propanol, puthanol, isopropyl alcohol (IPA), acetone ), Hexane, tetrahydrofuran (THF), or toluene.

The lithium precursor may, for example lithium hydroxide (LiOH), lithium metal (Li), lithium acetate (CH ₃ COOLi), lithium chloride (LiCl), lithium nitrate (LiNO _3), butyllithium (C ₄ H ₉ Li), methyl lithium (CH ₃ Li), or ethyl lithium (C ₂ H ₅ Li).

The lithium precursor may be added in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the solvent. When it exceeds the upper limit of the range Li this may be different forms, such as the Li ₂ TiO ₃ comprises in excess, if below the lower limit of the range Li is insufficient Li ₂ Ti ₃ O ₇ phase or Li ₄ Ti ₅ O _The TiO ₂ phase can be synthesized together with TiO ₂ and TiO ₂ .

In the preparation of the second mixed solution, 0.1 to 10 parts by weight of the titanate nanorods prepared in the step S1 is added to 100 parts by weight of the solvent. When the upper limit of the above range is exceeded, it is difficult to obtain a uniform nanorod structure and a nanorod structure that does not meet the lower limit of the above range is difficult to be exhibited.

When heating the second mixed solution in the hydrothermal synthesis vessel, it is preferable to fill the second mixed solution with the second mixed solution at a temperature of 80% or more of the volume in the hydrothermal synthesis vessel and heat the mixture. The Li ₂ Ti ₃ O ₇ phase or Li ₄ Ti ₅ O, which is a Li-deficient phase because Li can not be sufficiently exchanged for sodium ions, can not sufficiently supply energy due to the insufficient reaction pressure when the second mixed solution is filled below the above range. ₁₂ , TiO ₂ mixed phase can be synthesized.

Next, the lithium titanate nanorods are heat-treated (S3).

Through this step, lithium titanium spinel oxide nanorods are obtained from the lithium titanate nanorods.

The heat treatment in step S3 is preferably performed at a temperature of 300 to 800 ° C. If the heat treatment temperature exceeds the upper limit of the above range, an impurity phase such as TiO ₂ or Li ₂ TiO ₃ may be formed at the same time, and if the lower limit of the range is exceeded, a phase lacking crystallinity may be synthesized.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention. Such variations and modifications are intended to be within the scope of the appended claims.

< Example  1>

The amount of NaOH is adjusted to 10 molar concentration in distilled water, and the mixture is stirred at room temperature to prepare a 10 M NaOH aqueous solution. Titanium oxide (TiO ₂ ) nano powder was added to the solution and stirred for 3 hours to prepare a mixed solution. After that, it is transferred into a 100-mL capacity hydrothermal synthesis vessel, sealed, heated and held for 48 hours to react. After the reaction was completed, the reaction solution was slowly cooled to room temperature, and then washed with distilled water and 0.1 M HCl aqueous solution using a centrifugal separator to remove the by-products. The obtained slurry is dried under reduced pressure at 60 DEG C for 5 hours to obtain powdered sodium or proton titanate (Na / H-TiO) nanorods. During the washing, non-stoichiometric sodium or proton titanate (Na / H-TiO) is obtained by the aqueous solution of 0.1 M HCl on the sodium thiotitanate.

The 10 M NaOH aqueous solution was adjusted to an amount of 80 mL, and titanium oxide (TiO ₂ ) was added in an amount of 500 mg. The diameter and length of the spinel lithium titanium oxide nanorods (Li ₄ Ti ₅ O ₁₂ Nanorods) of the present invention can be controlled by the amount of the aqueous 10M NaOH solution and the amount of titanium oxide (TiO ₂ ). The reaction temperature was maintained at 220 占 폚.

Next, lithium titanate (Li-TiO) nanorods are obtained by ion exchange. First, 0.6 g of lithium hydroxide (LiOH-H ₂ O) was added to 80 mL of distilled water, followed by stirring at room temperature for 5 hours to dissolve all. To this solution, 0.1 g of sodium or proton titanate (Na / H-TiO) prepared above was added, and the mixture was stirred at room temperature for 3 hours to prepare a mixed solution. Distilled water was used as a solvent in the preparation of the mixed solution.

Next, the mixed solution was transferred into a 100 mL capacity hydrothermal synthesis vessel, sealed, heated to 170 DEG C and held for 12 hours to react. Thereafter, the mixture is washed with distilled water using a centrifugal separator, and dried at 60 ° C. for 5 hours under reduced pressure.

Finally, the lithium titanate (Li-TiO) nanorods were annealed at 550 ° C for 3 hours in air to obtain lithium titanate spinel oxide nanorods (Li ₄ Ti ₅ O ₁₂ Nanorods).

< Experimental Example  1> X-ray diffraction  analysis

The results of analyzing the products according to the synthesis steps of the spinel lithium titanium oxide nanorods (Li ₄ Ti ₅ O ₁₂ Nanorods) prepared in Example 1 are shown in FIG. 1, (Li ₄ Ti ₅ O ₁₂ Nanorods) were obtained by ultrafiltering the lithium niobate, proton titanate (Na / H-TiO) nanorod, lithium-titanate (Li-TiO) nanorod, .

<Experimental Example 2> Transmission electron microscopic analysis

FIG. 1 shows the results of analysis of the structure of the spinel lithium titanium oxide nanorods (Li ₄ Ti ₅ O ₁₂ Nanorods) of Example 1. After the hydrothermal synthesis, ion exchange, and heat treatment were completed through FIG. 1A, a uniform and independent rod-shaped lithium titanate spinel oxide nanorod (Li ₄ Ti ₅ O ₁₂ nanorods) was prepared. Can be confirmed as a result of high resolution transmission electron microscopy and the lattice constant value slightly increased compared to the lattice constant of general lithium titanate spinel oxide by residual sodium ions.

< Experimental Example  3> Evaluation of electrochemical characteristics

The results of the electrochemical analysis of the spinel lithium titanium oxide nanorods (Li ₄ Ti ₅ O ₁₂ Nanorods) of Example 1 are shown in FIG.

The half-cells manufactured using the negative electrode active material were charged and discharged at 1 to 3 V to C / 10, respectively, and the measurement results of their charge-discharge characteristics are shown in Fig. Further, 50 cycles of charging / discharging at 1 to 3 V and C / 10 were carried out. The results of the measurement of the charging / discharging characteristics are shown in Fig. 3B. galvanostatic intermittent titration technique (GITT). The results of the measurement are shown in FIG. 3C. Charge-discharging was carried out at 1 to 3 V with C / 10, C / 5, 1C, 5C, 10C and 20C, and the measurement results of the charge-discharge characteristics are shown in Fig.

FIG. 3A shows the potential flatness of the spinel lithium titanium oxide in the charge / discharge reaction. It can be seen that the polarization is reduced because the oxidation / reduction potential difference is lower than that of the spinel lithium titanium oxide nanoparticles, and 155 mAh / g , Indicating a higher capacity than the nanoparticles of spinel lithium titanium oxide. FIG. 3B shows the characteristics of 50 charge / discharge repetition. As shown in FIG. 3A, the spinel lithium titanium oxide nanorods (Li ₄ Ti ₅ O ₁₂ Nanorods) were maintained at a higher capacity than the spinel lithium titanium oxide nanoparticles, Showing reversibility. Figure 3c also shows that the polarizations of spinel lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ) nanorods are lowered compared to the spinel lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ) nanoparticles in the galvanostatic titration curves, Respectively. Finally, FIG. 3D shows a high output characteristic showing a capacity retention rate of about 77% even when the discharge rate (C-rate) of the spinel lithium titanium oxide nanorods (Li ₄ Ti ₅ O ₁₂ Nanorods) increases from C / .

From the above results, it can be seen that the spinel lithium titanium oxide nanorods (Li ₄ Ti ₅ O ₁₂ Nanorods) have a larger surface area per unit volume than the control spinel lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ) The decrease of lithium ion diffusion distance improves the electrical conductivity and ion conductivity. The lattice expansion due to the residual sodium ions leads to the improvement of Li ion diffusion due to the reduction of Li ion diffusion barrier. Therefore, It can be seen that it is suitable as an anode material of an advantageous lithium secondary battery.

Claims (17)

(S1) preparing a titanate nanorods by titanium oxide (TiO ₂₎ hydrothermal synthesis from a powder;
(S2) preparing lithium titanate (Li-TiO) nanorods by ion exchange from the titanate nanorods and the lithium precursor;
(S3) heat treating the lithium titanate nanorods;
Lt; / RTI &gt;
In the step S1, the titanium oxide powder is mixed with a basic aqueous solution or an acidic aqueous solution to prepare a first mixed solution, followed by heating and reacting.
Wherein the acidic aqueous solution is an aqueous solution of an acidic substance selected from the group consisting of hydrochloric acid, sulfuric acid and nitric acid,
Wherein the basic aqueous solution is an aqueous solution of a basic substance selected from the group consisting of sodium hydroxide, potassium hydroxide and calcium hydroxide,
Wherein the titanium oxide powder is added in an amount of 0.1 to 20 parts by weight based on 100 parts by weight of the basic aqueous solution or acidic aqueous solution during the production of the first mixed solution.
delete delete delete delete The method according to claim 1,
Wherein the heating of the first mixed solution is performed at a temperature of 110 to 300 &lt; RTI ID = 0.0 &gt; C. &Lt; / RTI &gt;
The method according to claim 1,
The step S2 includes mixing a lithium precursor, the titanate nanorods prepared in the step S1, and a solvent to prepare a second mixed solution. The spinel lithium titanium oxide nanorod anode active material Gt;
8. The method of claim 7,
And the step (S2) comprises heating and reacting the second mixed solution. The method for manufacturing a spinel lithium titanium oxide nanorod active material of a lithium secondary battery according to claim 1,
9. The method of claim 8,
Wherein the heating of the second mixed solution is performed at 110 to 300 &lt; 0 &gt; C.
8. The method of claim 7,
The solvent used for preparing the second mixed solution may be selected from the group consisting of water, ethanol, methanol, propanol, puthanol, isopropyl alcohol (IPA), acetone, hexane Wherein the anode active material is selected from the group consisting of hexane, tetrahydrofuran (THF), and toluene. The method for manufacturing a spinel lithium titanium oxide nanorod active material of a lithium secondary battery according to claim 1,
8. The method of claim 7,
The Li precursor is lithium hydroxide (LiOH), lithium metal (Li), lithium acetate (CH ₃ COOLi), lithium chloride (LiCl), lithium nitrate (LiNO _3), butyllithium (C ₄ H ₉ Li), Wherein the anode active material is selected from the group consisting of methyl lithium (CH ₃ Li) and ethyl lithium (C ₂ H ₅ Li).
8. The method of claim 7,
Wherein the lithium precursor is added in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the solvent in the preparation of the second mixed solution.
8. The method of claim 7,
Wherein the titanate nanorods prepared in the step (S1) are added in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the solvent in the preparation of the second mixed solution. .
The method according to claim 1,
Wherein the heat treatment in step S3 is performed at a temperature of 300 to 800 &lt; RTI ID = 0.0 &gt; C. &Lt; / RTI &gt;
14. A spinel lithium titanium oxide nanofiber anode active material of a lithium secondary battery produced by the method of any one of claims 1 to 14.
An anode of a lithium secondary battery comprising the spinel lithium titanium oxide nanofiber anode active material according to claim 15.
17. A lithium secondary battery comprising the negative electrode according to claim 16.

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