KR101883630B1 - Titanium oxide composite doped with carbon, and method for preparing the same - Google Patents

Abstract

The present invention relates to a titanium oxide composite doped with carbon, and a method for preparing the same. More specifically, the present invention relates to a titanium oxide composite doped with carbon which has improved lithium ion mobility, electrical conductivity and charge/discharge characteristics by uniformly doping carbon in an anatase-bronze type titanium oxide composite through hydrothermal synthesis; and to a method for preparing the titanium oxide composite doped with carbon. By simply doping carbon inside a titanium oxide composite through hydrothermal synthesis, the titanium oxide composite doped with carbon prepared by the method of the present invention has improved lithium ion mobility and electrical conductivity, and allows a user to manufacture a lithium secondary battery with improved high rate characteristics and lifetime efficiency when the titanium oxide composite doped with carbon is used as a negative electrode.

Description

TECHNICAL FIELD [0001] The present invention relates to a carbon-doped titanium oxide composite and a method for manufacturing the same. BACKGROUND ART < RTI ID = 0.0 >

The present invention relates to a carbon-doped titanium oxide composite, and more particularly, to a carbon-doped titanium oxide composite which is uniformly doped with carbon in an anatase-bronz type titanium oxide complex by hydrothermal synthesis, And a carbon-doped titanium oxide composite having improved electric conductivity and improved charge / discharge characteristics, and a method for producing the same.

2. Description of the Related Art In general, the demand for a rechargeable lithium secondary battery as a driving power source for portable electronic devices for information communication such as a video camera, a PDA, a mobile phone, a notebook computer, an electric bicycle, and an electric vehicle is rapidly increasing. Particularly, since the performance of these products is dependent on the secondary battery, which is a core component, studies on the capacity increase of the negative electrode active material are increasing day by day.

Lithium batteries have spread rapidly in recent years because of their high energy density and excellent cycle characteristics, and are required to have lower cost and more readily available electrode active materials than commonly used lithium transition metal complex oxides.

The lithium secondary battery is manufactured by using a material capable of inserting and desorbing lithium ions as a cathode and an anode, filling an organic electrolyte or a polymer electrolyte between the anode and the cathode, and when lithium ions are inserted and removed from the anode and the cathode And an electric energy is generated by a reduction reaction.

As the negative electrode active material of the lithium secondary battery, graphite, a high-capacity silicon-based transition metal oxide, a tin-based transition metal oxide, and the like are used. However, the negative electrode active material developed so far has a lot of room for improvement because the capacity, the high rate discharge characteristic and the life characteristic have not reached satisfactory level.

Lithium secondary batteries generally use graphite capable of providing a flat electric potential as a negative electrode, but because of low discharge potential of graphite, there is a concern regarding stability for use in a large-sized battery such as a hybrid vehicle (HEV application).

On the other hand, it has been reported that a battery using a complex oxide containing titanium as an electrode active material has an excellent rapid charge / discharge performance and a long life.

Titanium oxide has been studied as a material for a negative electrode and a possibility of a material having various crystal structures as an electrode active material. As titanium oxide, rutile, anatase or brookite type titanium dioxide is known depending on the crystal structure, and recently, a crystal structure called bronze type (Non-Patent Document 1) has been reported.

 A titanium dioxide (TiO 2 -B) active material having a bronze-type crystal structure has recently attracted attention as an electrode material capable of an absorption-desorption reaction of a smooth lithium equivalent to a spinel-type lithium-titanium oxide and capable of a higher capacity than the spinel type Document 1 and Non-Patent Document 2).

Titanium oxide (TiO2-B) with a bronze phase has a theoretical capacity as high as 305 mAh / g, which not only provides a high capacity lithium battery but also exhibits a charge / discharge voltage of 1.6 V similar to titanium-based lithium oxide There is an advantage that problems such as electrolyte decomposition and the like do not occur during charging and discharging.

However, the bronze-type titanium oxide has a disadvantage in that its kinetic property is not excellent and its theoretical capacity is not expressed, and high-rate characteristics and life characteristics are also deteriorated. Therefore, a method for maximizing the electrode capacity of the bronze-type titanium oxide (TiO 2 -B) is required.

Among these problems, a carbon coating process is frequently used to improve the conductivity. However, since the carbon coating has to be fired in a high temperature and a reducing atmosphere, it is necessary to burn the carbon coating in a specific temperature range and oxygen atmosphere Titanium oxide is difficult to apply. In addition, titanium carbide, which is a titanium raw material that has been used for conventional carbon doping, is not preferable from the viewpoint of cost as an expensive raw material.

(Patent Document 1) Japanese Patent Application No. 2006-299477

Thomas P. Feist et al., &Quot; The soft Chemical Synthesis of TiO2 (B) from Layered Titanates ", Journal of Solid State Chemistry 101 (1992), 275-295 (Non-Patent Document 2) L. Brohan, R. Marchand, Solid State Ionics, 9-10, 419-424 (1983)

It is another object of the present invention to provide a carbon-doped titanium oxide composite having improved charging / discharging capacity and service life in order to solve the above-mentioned problems of conventional titanium oxide.

The present invention also aims to provide a method for producing a carbon-doped titanium oxide composite according to the present invention.

In order to solve the above problems,

There is provided a titanium oxide composite having a crystal phase in which a carbon-doped anatase type and a bronze type are mixed.

In the carbon-doped titanium oxide composite according to the present invention, the titanium oxide includes titanium dioxide.

In the carbon-doped titanium oxide composite according to the present invention, the titanium oxide has a peak intensity of the bronze (002) face to the sum of the peak intensity of the anatase-type (111) plane and the peak intensity of the bronze The ratio I (002) / (I (111) + I (110)) is 0.1 to 0.2.

In the carbon-doped titanium oxide composite according to the present invention, the titanium oxide may be characterized in that the distance between the bronze-type (001) planes is 0.63 nm to 0.66 nm.

The carbon-doped titanium oxide complex according to the present invention may be characterized by having a bimodal particle size of 1 to 3 μm or 200 to 300 nm.

The carbon-doped titanium oxide composite according to the present invention may be characterized in that it comprises a peak due to bronze TiO 2 at 10 to 20 ° or 40 to 50 ° in XRD analysis.

The present invention also relates to

Preparing a mixed solution by mixing a titanium precursor and a sodium precursor

Mixing a carbon precursor with the mixed solution to prepare a precursor solution;

Hydrothermally synthesizing to form particles;

Ion exchange reaction step; And

Sintering; Doped titanium oxide composite according to the present invention.

In the method for producing a carbon-doped titanium oxide composite of the present invention, the mixed solution may be characterized in that titanium is mixed at a molar ratio (Ti / Na mole ratio) of 0.1 to 0.4 per 1 mole of sodium.

In the method of manufacturing a carbon-doped titanium oxide composite of the present invention, the precursor solution may be mixed with the carbon precursor at a ratio of 5 to 20 parts by weight per 100 parts by weight of the mixed solution.

The titanium oxide precursor may be Ti metal, anatase TiO ₂ , TiO (OH) ₂ , Ti (OH) ₄ , TiCl ₄ , TiCl ₃ , TiC, Ti [ OCH (CH ₃ ) ₂ ] _4, and combinations thereof.

In the method for preparing the carbon-doped titanium oxide complex of the present invention, the carbon precursor may be selected from isopropyl alcohol, ethanol, sucrose, glycolic acid, and combinations thereof.

In the method for producing a carbon-doped titanium oxide composite of the present invention, the hydrothermal synthesis may be performed at a heating temperature of 150 to 170 ° C and a pressure of 1.5 to 6.0 kgf / cm ² for 48 hours.

In the method for producing the carbon-doped titanium oxide complex of the present invention, the ion exchange reaction step may be carried out with hydrochloric acid.

In the method for producing the carbon-doped titanium oxide composite of the present invention, the sintering may be performed at a temperature of 250 to 400 ° C.

The present invention also provides a lithium secondary battery having a carbon-doped titanium oxide complex according to the present invention as a cathode and having improved electrochemical characteristics.

The present invention relates to a carbon-doped titanium oxide composite produced by the production method of the present invention by relatively easily and uniformly doping carbon into the interior of the titanium oxide composite by hydrothermal synthesis, thereby improving lithium ion mobility and electric conductivity, It is possible to manufacture a lithium secondary battery having improved high rate characteristics and improved lifetime efficiency.

Fig. 1 shows XRD analysis results of the carbon-doped TiO2 composite according to Example 1 of the present invention.
2 is a SEM photograph of a TiO2 composite without carbon doping according to Comparative Example 1 of the present invention.
3 is a SEM photograph of a carbon-doped TiO2 composite according to Example 1 of the present invention.
4 is a TEM photograph of a TiO2 composite without carbon doping according to Comparative Example 1 of the present invention.
5 is a TEM photograph of a carbon-doped TiO2 composite according to Example 1 of the present invention.

Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited thereto.

< Example 1 > Carbon Doped  Manufacture of titanium oxide complex

To 200 mL of a 10 M sodium hydroxide solution was added TiO (OH) ₂ 78.3 g was added to prepare a mixed solution having a Ti / Na molar ratio of 0.4. A precursor solution was prepared by adding 10% of isopropyl alcohol as a doping material to the mixed solution. At this time, Isopropyl alcohol was mixed at a ratio of 5 to 20 parts by weight per 100 parts by weight of the mixed solution.

The prepared precursor solution was reacted in an autoclave at 160 ° C. for 24 hours and then maintained at the above temperature and pressure of 1.5 to 6.0 kgf / cm ² for 72 hours, washed with distilled water, and then treated with 0.1 M hydrochloric acid Ion exchange reaction was carried out.

Subsequently, the precipitate was filtered, sufficiently washed with distilled water, and then sintered at 350 ° C for 4 hours to prepare a titanium oxide composite.

< Example 2 > Carbon Doped  Manufacture of titanium oxide complex

A carbon-doped titanium oxide composite was prepared in the same manner as in Example 1, except that the carbon doping material in Example 1 was changed to 10% Ethanol.

< Comparative Example 1 > Manufacture of undoped titanium oxide composites

A titanium-oxide composite without carbon doping was prepared in the same manner as in Example 1, except that the carbon doping material was not added in Example 1.

< Experimental Example 1 > Anatase - Bronze type  Titanium oxide complex XRD  analysis

The carbon-doped titanium oxide composite prepared according to the above example was analyzed for crystal structure through XRD and the results are shown in Fig.

As shown in FIG. 1, the carbon-doped titanium oxide composite prepared according to an embodiment of the present invention had peaks due to anatase-type TiO 2 at 10.3, 10.5, 10.5, and 10.5 at 25.3 °, 37.9 °, 54.0 °, To 20 [deg.] Or 40 to 50 [deg.].

The peak observed through the XRD analysis shows that anatase and bronze phases are mixed, and it can be confirmed that the titanium oxide complex produced according to one embodiment of the present invention is a crystal phase mixed with an anatase and a bronze phase.

< Experimental Example 2 > Scanning Electron Microscope ( SEM ) analysis

SEM measurement of the carbon-doped titanium oxide composite prepared according to Comparative Example 1 and the carbon-doped titanium oxide composite prepared according to Example 1 were carried out, and the results are shown in FIGS. 2 and 3.

As shown in FIGS. 2 and 3, the carbon-doped titanium oxide composite prepared according to the present invention has a diameter of 1 to 3 .mu.m or 200 to 300 nm, and the particle size is bimodal.

By having such a bimodal particle size, the carbon-doped titanium oxide composite produced by the present invention can secure an improved tap density.

< Experimental Example 3 > Transmission electron microscope ( TEM ) analysis

A TEM measurement of the carbon-doped titanium oxide composite prepared according to Comparative Example 1 and the carbon-doped titanium oxide composite prepared according to Example 1 were performed, and the results are shown in FIGS. 3 and 4. FIG.

As shown in FIGS. 3 and 4, the interplanar distance of the carbon-doped titanium oxide composite particles was 0.627 nm, the interplanar distance of the carbon-doped titanium oxide composite particles was 0.644 nm, and the interplanar distance .

< Manufacturing example > Battery production

Using the final powder of the carbon-doped titanium oxide composite prepared according to the above example as an electrode active material, an electrode for a lithium secondary battery and a coin half cell were fabricated.

In order to manufacture the coin-shaped half-cell, super-P was used as a conductive material and polyvinylidene fluoride (PVDF) was used as a binder.

An electrode material: super-P: polyvinylidene fluoride (PVDF) containing the carbon-doped titanium oxide complex was mixed in a weight ratio of 80:10:10. This was added to N-methyl pyrrolidone (NMP) and mixed in a mixer to prepare a slurry. The mixed slurry was coated on one side of an aluminum foil and dried, followed by rolling using a pressing process to produce a negative electrode plate.

The negative electrode plate was punched out with a circular specimen having a diameter of 1.11 cm and used as a negative electrode, and a lithium metal thin plate was used as a positive electrode.

1.2 M of LiPF 6 was dissolved in a mixture of ethylene carbonate (EC): ethyl methyl carbonate (EMC) at a volume ratio of 30: 70 and used as an electrolyte. A lithium secondary battery was fabricated using W-scope C500 film as a separator .

< Experimental Example 4 > Evaluation of Battery Charging / Discharging Characteristics

A lithium secondary battery was prepared using the titanium oxide composite prepared in Example 1 and Comparative Example 1 as an electrode active material, and the charging / discharging characteristics thereof were evaluated. The results are shown in Table 1 below.

The charge / discharge capacity is measured at a constant voltage of 1.0 to 3.0 V at a charging / discharging current of 1 C = 337 mAh / g and is performed at a constant current. Measuring the charge / discharge capacity in the second cycle and the 50th cycle; (Discharge capacity in the 50th cycle / discharge capacity in the second cycle) x 100 is defined as a cycle characteristic.

Evaluation of battery characteristics
(1.0 to 3.0 V) unit Comparative Example 1 Example 1 Example 2 High rate
characteristic 0.1C charge / 0.1C discharge mAh / g 239.5 / 227.2 250.8 / 236.2 231.2 / 226.5 0.2C  charge/ 0.2C  Discharge mAh / g 229.7 / 224.8 233.0 / 228.2 231.5 / 226.0 0.2C  charge/ 1.0 C  Discharge mAh / g 211.8 / 208.8 208.2 / 203.1 217.3 / 210.9 0.2C  charge/ 2.0C  Discharge mAh / g 187.1 / 183.1 191.0 / 188.5 193.0 / 188.6 0.5 C  charge/ 2.0C  Discharge mAh / g 185.1 / 182.1 189.6 / 185.7 187.6 / 184.5 0.5 C  charge/ 5.0 C  Discharge mAh / g 151.5 / 147.4 160.2 / 157.0 156.9 / 152.2 0.5 C  Charging / discharging at 10.0C mAh / g 114.6 / 112.5 134.8 / 136.9 120.7 / 115.0 life span
efficiency @ 50 cycle
( 1.0 C  charge/ 1.0 C  Discharge) % 87.1 90.3 83.6

As shown in Table 1, it can be confirmed that the battery using the carbon-doped titanium oxide composite prepared in Example 1 of the present invention as the negative electrode active material of the secondary battery has excellent cycle characteristics and a large charge / discharge capacity .

Claims (15)

The present invention relates to a titanium oxide composite having a crystal phase in which a carbon-doped anatase type and a bronze type are mixed,
The ratio [I (002) / (I (111) + I (110)) of the peak intensity of the bronze type (002) face to the sum of the peak intensity of the anatase type (111) face and the peak intensity of the bronze type )] Is 0.1 to 0.2
Carbon-doped titanium oxide complex.
delete The method according to claim 1,
Wherein the titanium oxide has a distance between bronze (001) planes of 0.63 to 0.66 nm.
The method according to claim 1,
Wherein the composite has a bimodal particle size of from 1 to 3 um or from 200 to 300 nm.
The method according to claim 1,
Wherein the composite comprises a peak by bronze TiO2 at 10-20 [deg.] Or 40-50 [deg.] In XRD analysis.
Preparing a mixed solution by mixing a titanium precursor and a sodium precursor
Mixing a carbon precursor with the mixed solution to prepare a precursor solution;
Hydrothermally synthesizing to form particles;
Ion exchange reaction step; And
Sintering; Containing
A method for producing a carbon-doped titanium oxide composite.
The method according to claim 6,
Wherein the mixed solution is mixed at a Ti / Na mole ratio of 0.1 to 0.4 per mole of sodium.
The method according to claim 6,
Wherein the precursor solution is mixed at a ratio of 5 to 20 parts by weight of carbon precursor per 100 parts by weight of the mixed solution.
The method according to claim 6,
The titanium oxide precursor is selected from Ti metal, anatase TiO ₂ , TiO (OH) ₂ , Ti (OH) ₄ , TiCl ₄ , TiCl ₃ , TiC, Ti [OCH (CH ₃ ) ₂ ] _4, &Lt; / RTI &gt;
The method according to claim 6,
Wherein the carbon precursor is selected from the group consisting of Isopropyl alcohol, ethanol, sucrose, glycolic acid, and combinations thereof.
The method according to claim 6,
Wherein said hydrothermal synthesis is carried out at a heating temperature of 150 to 170 DEG C and a pressure of 1.5 to 6.0 kgf / cm &lt; ² &gt; for 48 hours.
The method according to claim 6,
Wherein the ion exchange reaction step is performed by adding hydrochloric acid.
The method according to claim 6,
Wherein the sintering step is performed at a temperature of 250 to 400 캜.
14. An anode for a lithium secondary battery comprising a carbon-doped titanium oxide composite produced by the method of any one of claims 6 to 13.
A lithium secondary battery comprising the negative electrode for a lithium secondary battery having the carbon-doped titanium oxide composite of claim 14.

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