WO2012020998A2

WO2012020998A2 - Method for preparing lithium titanium oxide, lithium titanium oxide prepared by same, and lithium secondary battery comprising the lithium titanium oxide

Info

Publication number: WO2012020998A2
Application number: PCT/KR2011/005878
Authority: WO
Inventors: 홍지준; 변기택; 김효원
Original assignee: 주식회사 루트제이제이
Priority date: 2010-08-11
Filing date: 2011-08-11
Publication date: 2012-02-16
Also published as: KR20120022622A; KR101285171B1; WO2012020998A3

Abstract

The present invention relates to a method for preparing lithium titanium oxide, to lithium titanium oxide prepared by same, and to a lithium secondary battery comprising the lithium titanium oxide. The method for preparing lithium titanium oxide according to the present invention comprises the following steps: mixing raw materials for preparing lithium titanium oxide; drying the mixture; and transferring and sintering the dried mixture. The method for preparing lithium titanium oxide according to the present invention involves performing reaction, drying, and heat-treatment processes while transferring the mixture, and therefore enables a large volume of lithium titanium oxide to be prepared in a more economically advantageous manner as compared to conventional batch methods. Further, the lithium titanium oxide prepared by the consecutive reaction of the present invention may exhibit superior electrode characteristics as an electrode material as compared to lithium titanium oxide prepared by a batch reaction method.

Description

Method for producing lithium titanium oxide, lithium titanium oxide produced thereby and lithium secondary battery comprising same

The present invention relates to a lithium titanium oxide manufacturing method, a lithium titanium oxide produced thereby and a lithium secondary battery comprising the same, more specifically in a more economical manner, can be produced in a large capacity lithium titanium oxide having excellent characteristics It relates to a lithium titanium oxide manufacturing method, a lithium titanium oxide produced thereby and a lithium secondary battery comprising the same.

Recently, with the development of portable devices such as mobile phones, notebook computers, camcorders, etc., demand for secondary batteries such as Ni-MH (Ni-MH) secondary batteries and lithium secondary batteries is increasing. In particular, lithium secondary batteries using lithium and nonaqueous electrolytes have been actively developed due to the high possibility of realizing small, lightweight and high energy density batteries. Generally, a transition metal oxide such as LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ is used as a cathode material of a lithium secondary battery, and lithium metal or carbon is used as an anode material. This is used, and a lithium secondary battery is comprised using the organic solvent which contains lithium ion as electrolyte between two electrodes.

However, a lithium secondary battery using metal lithium as a negative electrode tends to generate dendrite crystals when charging and discharging is repeated, and there is a high risk of short circuit. Lithium secondary batteries that use a nonaqueous solvent containing lithium ions as an electrolyte have been put to practical use. However, since the carbon-based material has a large irreversible capacity, there is a problem in that initial charge and discharge efficiency is low and the capacity is reduced. In addition, lithium may be deposited on the surface of carbon during overcharging, thereby causing a problem in safety.

On the other hand, lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ , LTO) material, which has recently been spotlighted as a negative electrode material of a lithium ion battery, has an operating voltage of 1.3 to 1.6 V, which is higher than that of a conventional carbon-based negative electrode material and has a reversible capacity. Although it has a disadvantage of being small as about 170 mAh / g, high-speed charging and discharging is possible, there is almost no irreversible reaction (over 95% of initial efficiency), and the heat of reaction is very low, so it has the advantage of excellent safety. In addition, the theoretical density of the carbon material is about 2 g / cm ³ , but Li ₄ Ti ₅ O ₁₂ has a theoretical density of 3.5 g / cm ^3, which is similar to the carbon material. In general, a method of manufacturing the LTO material is a method in which a lithium source and a titanium source are mixed at a temperature of 500 to 1200 ° C., and then calcined in one baking furnace by a predetermined time batch method.

For example, Korean Patent Laid-Open Publication No. 10-2008-0023831 includes the steps of appropriately mixing a source material of lithium (Li) and a source material of titanium (Ti); b) adding and mixing a substance containing at least one element selected from the group consisting of B, Sn, S, Be, Ge, and Zn to the mixture; And c) calcining the mixture to synthesize Li 4 Ti 5 O 12. The prior art also discloses a heat treatment process of a batch method in the same manner as the conventional general method in the heat treatment method. However, such a batch method has a limitation in the production capacity, and in order to process a large capacity, the size of the firing furnace eventually increases, so there is a limitation in the production capacity.

Therefore, the problem to be solved by the present invention is to provide a lithium titanium oxide manufacturing method capable of producing a large amount of lithium titanium oxide of excellent characteristics in a more economical manner, thereby providing a lithium titanium oxide and a lithium secondary battery comprising the same will be.

In order to solve the above problems, the present invention comprises the steps of mixing the raw material for the production of lithium titanium oxide; Drying the mixture; And it provides a method for producing lithium titanium oxide comprising the step of firing when the dried mixture is moved.

In one embodiment of the present invention, the mixing, drying and firing is carried out continuously, the movement of the dried mixture in the firing step may be carried out by gravity.

In one embodiment of the present invention, the raw material is at least one lithium source selected from the group consisting of Li ₂ CO ₃ , LiOH, LiF, Li ₂ SO ₄ , LiNO ₃ , LiCl and TiO ₂ , TiCl ₄ , TiOCl ₂ , TiOSO ₄ , TiO (OH) ₂ and at least one titanium source selected from the group consisting of, wherein the mixing of the raw material may be performed by an in-line mixer.

In order to solve the above another problem, the present invention provides a lithium titanium oxide prepared by the above-described method, and also provides a lithium secondary battery comprising the lithium titanium oxide as an electrode material.

In the present invention, the method for producing lithium titanium oxide is made by reaction, drying, and heat treatment in the process of being moved, and thus, it is possible to produce a large capacity lithium titanium oxide in a more economical manner as compared with the conventional batch method. Furthermore, the lithium titanium oxide produced by such a continuous reaction method exhibits excellent electrode characteristics compared to the lithium titanium oxide produced by a batch reaction method as an electrode material.

1 is a step diagram of a method for producing lithium titanium oxide according to an embodiment of the present invention.

2 is a particle image of a material produced according to the method according to the invention.

3 is a particle image for the comparative material.

4 is a graph of the cell specific capacity according to voltage.

Hereinafter, the present invention will be described in detail with reference to the drawings. The following embodiments are provided as examples to ensure that the spirit of the present invention to those skilled in the art will fully convey. Therefore, the present invention is not limited to the embodiments described below and may be embodied in other forms.

According to the present invention, unlike the prior art in which raw materials are mixed in a fixed reactor and then fired for a predetermined time in another fixed kiln, lithium titanium oxide having a heat treatment method in which raw materials (lithium source, titanium source) are moved ( LTO) manufacturing method. In particular, the continuous process according to the present invention enables the production of large-capacity LTO, without the need for a large-volume firing furnace, thereby reducing the production process cost.

1 is a step diagram of the LTO manufacturing process according to an embodiment of the present invention.

Referring to FIG. 1, first, a lithium source and a titanium source are mixed. In this case, a separate additive for powder growth may be added and mixed with the lithium source and the titanium source, but the scope of the present invention is not limited thereto. In one embodiment of the present invention, the lithium source may be, for example, at least one selected from the group consisting of Li ₂ CO ₃ , LiOH, LiF, Li ₂ SO ₄ , LiNO ₃ , LiCl, but the scope of the present invention is limited thereto. It doesn't work In addition, the titanium source may be, for example, TiO ₂ , TiCl ₄ , TiOCl ₂ , TiOSO ₄ , TiO (OH) ₂ , but the scope of the present invention is not limited thereto. At this time, the raw material according to the present invention is moved through the tube, it can be mixed by the in-line mixer provided in the moving path.

Thereafter, the mixed raw material moves through the pipe, and drying is performed in the process of being moved. Alternatively, however, the mixing and / or drying steps can also proceed in a batch manner until the firing step, at least as long as the firing step is a continuous mode, all of which are within the scope of the present invention.

According to an embodiment of the present invention, the dried mixture (raw material of lithium titanium oxide) is continuously moved through the pipe, and dried, and the dried material is subjected to a continuous kiln again.

Continuous firing furnace of the present invention is a form that can be moved at the same time the material fired in the interior firing. According to an embodiment of the present invention, the kiln is in the form of rotating in a cylindrical shape, the kiln is inclined at a predetermined angle. By the inclination of the kiln, the material inside the kiln is moved by gravity, and at the same time, the high temperature heat treatment proceeds. That is, the material inside the kiln is continuously moved by gravity, and is exposed to the heat at the top of the kiln, and the firing proceeds. The inventors of the present invention improve the productivity by solving the problem of lowering the productivity by cooling in the moving process, especially when moving / firing at the same time, and also obtain the lithium titanium oxide calcined in crystalline form in terms of physical properties. The electrode material also has excellent characteristics, which will be described in more detail with reference to the following experimental examples.

Although the names are described in more detail, the scope of the present invention is not limited by the examples given below.

Example 1

A lithium titanium oxide manufacturing method was prepared as shown in FIG. 1. That is, 1 kg of TiO 2 powder having a primary particle size of about 150 nm and 0.5 kg of LiOH.H ₂ O were mixed and dried. Then, the dried material was heat treated at 700 ° C. for 18 hours through a continuous kiln mixed with moving raw materials continuously as described above to obtain LTO powder.

Example 2

Except for adding the carbon raw material, it was prepared in the same manner as in Example 1.

Comparative Example 1

A commercial LTO powder prepared by firing in a stationary state for comparison was purchased.

Test Example 1

FE-SEM

Using FE-SEM (field scanning microscope), the particle shape of the negative electrode active material prepared in the above example was observed, which is shown in FIG. 2. Referring to FIG. 2, it can be seen that the average particle size of the negative electrode active material is 200 to 300 nm and the particles grow in a crystalline form. On the other hand, it can be seen that the comparative example fired in the stationary state is relatively weak in the crystal state. This difference in crystal phase also has a significant effect on the physical properties of the electrode material, which will be described in detail below.

Test Example 3

Particle size analysis

The particle size analysis of the material was performed using a laser diffraction particle size distribution meter. From the results of the cumulative particle size distribution, the particle sizes at the points where the cumulative volumes reached 10%, 50%, and 90% were confirmed to be d10, d50, and d90, respectively. The results are shown in Table 1 below. As shown in Table 1, the particle size of the LTO prepared in Examples 1 and 2 appears to be large, indicating that the crystallization is further made. From the results in Test Example 4, it can be seen that the specific particle size and crystallization of the titration should be made as the specific amounts of Examples 1 and 2 were larger.

Table 1

	Example 1	Example 2	Comparative Example 1
SSA [m2 / g]	60.6	68.2	69.8
d10 [μm]	0.12	0.13	0.05
d50 [μm]	0.24	0.26	0.15
d90 [μm]	0.34	0.35	0.20
pH	11.94	11.88	11.67

Test Example 4

Tap density

The tap density was calculated by tapping 50 g of material into the cylinder, measuring the volume after 2000 taps, and calculating the tap density. The results are shown in Table 2.

Referring to Table 2, it can be seen that the performance of the material produced by the continuous transfer / firing method according to the present invention is superior to the comparative example.

TABLE 2

		Example 1		Example 2		Comparative Example 1
Cycle	Mode	[+] mAh / g	efficiency	[+] mAh / g	efficiency	[+] mAh / g	efficiency
		[-] mAh / g		[-] mAh / g		[-] mAh / g
One	CHA	137.7	89.0	137.9	90.2	136.4	98.8
	DCH	154.7		154.1		153.6
2	CHA	138.4	99.4	138.1	100.1	136.6	100.0
	DCH	154.7		154.4		153.7
3	CHA	138.2	100.3	137.4	99.7	136.0	100.1
	DCH	154.8		153.6		153.1

Test Example 5

Battery rating

For the battery evaluation, the negative electrode active material (lithium titanium oxide): conductive agent: binder in the weight ratio of 85: 9: 3, the positive electrode active material (lithium nickel manganese cobalt oxide): the conductive agent, the binder in 92: 4.5: 3.5 Weighed. After mixing the slurry of the mixed material to the aluminum thin film and dried for 8 hours at 120 ℃ to prepare a pole plate, and then press the prepared pole plate. A 2030 type coin cell was prepared, and 1M-LiPF6 dissolved in EC-DEC (volume ratio 1: 1) was used as an electrolyte. Charge was cut off at 2.7V and discharge 1.5V, and it was charged and discharged at 0.1C. The results are shown in Table 2. As shown in Table 2, the smaller the particles, the higher the specific capacity of the battery, but rather the larger specific particle size. In addition, as shown in FIG. 4, the higher the C rate, the higher the cell efficiency of the active materials prepared in Examples 1 and 2 than the active materials prepared in Comparative Example 1. This suggests that the smaller the preceding particle size is, the better the cost will be, but rather the particle size and crystallization to some extent, and this crystallization is ultimately maximized in the way that the firing and migration proceed simultaneously.

TABLE 3

Relative Capacity [%]
C-rate	Comparative Example 1	Example 1	Example 2
0.5C	100.0	100.0	100.0
1.0C	97.7	97.2	97.9
2.0C	94.1	94.0	95.3
5.0C	88.2	89.2	91.1
8.0C	82.4	85.5	88.2
10.0C	77.4	82.9	85.5
12.0C	71.2	78.3	83.2

The present invention relates to a lithium titanium oxide manufacturing method capable of producing a large amount of lithium titanium oxide having excellent characteristics in an economical manner, to a lithium titanium oxide produced thereby and a lithium secondary battery comprising the same, which is used in the battery business There is a possibility.

Claims

Mixing raw materials for producing lithium titanium oxide;

Drying the mixture; And

Lithium oxide manufacturing method comprising the step of baking when the dried mixture material is moved.
The method of claim 1,

The mixing, drying and firing is a lithium titanium oxide production method characterized in that it is carried out continuously.
The method of claim 1,

Lithium oxide manufacturing method, characterized in that the movement of the dried mixture is carried out by gravity in the firing step.
The method of claim 1,

The raw material is at least one lithium source selected from the group consisting of Li 2 CO 3 , LiOH, LiF, Li 2 SO 4 , LiNO 3 , LiCl and TiO 2 , TiCl 4 , TiOCl 2 , TiOSO 4 , TiO (OH) 2 Lithium titanium oxide manufacturing method comprising at least one titanium source selected from the group consisting of.
The method of claim 4, wherein

The raw material is a lithium titanium oxide manufacturing method characterized in that it further comprises carbon.
The method of claim 1,

Mixing of the raw material is a lithium titanium oxide manufacturing method, characterized in that carried out by an in-line mixer.
Lithium titanium oxide prepared by the method according to any one of claims 1 to 6.
A lithium secondary battery comprising the lithium titanium oxide according to claim 7 as an electrode material.