KR20160080098A - Manufacturing method of lithium complex oxide, and lithium complex oxide made by the same - Google Patents

Abstract

The present invention relates to a method for producing a lithium composite oxide and a lithium composite oxide produced by the method. More particularly, the present invention relates to a method for producing a lithium composite oxide, which comprises the steps of: preparing a transition metal precursor; mixing the transition metal precursor and a lithium compound; And calcining the mixture, wherein the step of calcining the mixture comprises a temperature rising section, a first temperature holding section, a second temperature holding section, and a cooling section, and the second temperature maintaining And the section is fired in an oxygen-containing atmosphere of 20 vol% to 99 vol%. The present invention also relates to a method for producing a lithium composite oxide and a lithium composite oxide produced thereby.

Description

TECHNICAL FIELD [0001] The present invention relates to a method for producing a lithium composite oxide, and a lithium composite oxide produced by the method. BACKGROUND OF THE INVENTION 1. Field of the Invention [0002]

The present invention relates to a method for producing a lithium composite oxide and a lithium composite oxide produced by the method. More particularly, the present invention relates to a lithium composite oxide prepared by preparing a transition metal precursor, mixing a lithium compound, A second temperature holding period, and a cooling period, and firing is performed in a specific section. The present invention also relates to a lithium composite oxide produced by the method.

As the technology and demand for mobile devices increase, the demand for secondary batteries as energy sources is rapidly increasing. Lithium secondary batteries, which exhibit high energy density and operating potential, long cycle life and low self-discharge rate among such secondary batteries, It has been commercialized and widely used.

Lithium-containing cobalt oxide (LiCoO ₂ ) is mainly used as a positive electrode active material of a lithium secondary battery, and a lithium-containing manganese oxide such as LiMnO _{2 having a} layered crystal structure and LiMn ₂ O _{4 having a} spinel crystal structure, (LiNiO ₂ ) is also being considered.

Of the above cathode active materials, LiCoO ₂ is most widely used because of its excellent lifetime characteristics and charge / discharge efficiency. However, LiCoO ₂ has a low structural stability and is expensive due to the limited resource of cobalt used as a raw material. There is a disadvantage that price competitiveness is limited for mass use. Lithium manganese oxides such as LiMnO ₂ and LiMn ₂ O ₄ are advantageous in that they are rich in resources of manganese used as a raw material, are inexpensive, environmentally friendly, and excellent in thermal stability. However, they are small in capacity, And the like.

The method for preparing such a lithium composite oxide generally comprises preparing a transition metal precursor, mixing the transition metal precursor with a lithium compound, and then calcining the mixture. At this time, the lithium compound is preferably at least one selected from the group consisting of LiOH and Li ₂ CO ₃ . In order to reduce the production cost, it is more preferable to use Li ₂ CO ₃ which is lower in cost as a Li compound.

However, when Li ₂ CO ₃ is generally used as a Li compound, Li ₂ CO ₃ There is a problem that since the decomposition of CO ₂ generates CO ₂ and further decomposition of Li ₂ CO ₃ for the reaction may be thermodynamically disturbed, the reaction does not proceed any more and Li ₂ CO ₃ remains after the reaction. Particularly, such residual Li ₂ CO ₃ reacts with an electrolyte or the like in the battery to cause gas generation and swelling phenomenon, thereby causing a problem that the high-temperature safety is severely deteriorated.

DISCLOSURE OF THE INVENTION It is an object of the present invention to provide an economical method for producing a lithium composite oxide and a lithium composite oxide produced by the production method while improving the characteristics of a cathode active material while reducing residual lithium .

Disclosure of Invention Technical Problem [8] Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior art, Mixing the transition metal precursor and a lithium compound; And calcining the mixture; Wherein the step of firing the mixture comprises a temperature rising section, a first temperature holding section, a second temperature holding section, and a cooling section, wherein the temperature of the first temperature holding section and the temperature The temperature of the second temperature holding section is maintained at 700 ° C to 800 ° C for 6 hours, the temperature of the first temperature holding section and the temperature of the second temperature holding section are the same, By volume in an oxygen-containing atmosphere of from 1% by volume to 99% by volume, and the cooling rate is controlled in the range of 90 ° C / h to 110 ° C / h in the cooling section.

In one embodiment, the second temperature maintaining period and the cooling period are fired in an oxygen-containing atmosphere of 20% by volume to 99% by volume, and the temperature rising period and the first temperature holding period are lithium A method for producing a composite oxide is provided.

In one embodiment, the temperature raising rate is controlled at a rate of temperature increase of 30 ° C / h to 300 ° C / h.

The present invention also provides a lithium composite oxide produced by the production method of the present invention.

In one embodiment, the lithium composite oxide has a LiOH content of less than 0.5 wt% and a Li ₂ CO ₃ content of less than 1 wt% based on the total weight of the oxide.

In one embodiment, the lithium composite oxide provides a lithium complex oxide represented by the following formula (1).

[Chemical Formula 1] LixNi1-y-zCoyMzO ₂

(Wherein M is at least one kind of metal element selected from the group consisting of Al, Zn, Ti, V, Cr, Mn, Fe and Y)

According to the method for producing a lithium composite oxide according to the present invention, since the layered crystal structure is stably maintained under specific reaction conditions even when Li ₂ CO ₃ is used as the Li compound by specifying the oxygen injection period in the firing step, And a cathode active material in which the amount of residual Li is minimized can be produced.

In addition, according to the method for producing a lithium composite oxide according to the present invention, a lithium composite oxide can be economically produced by dividing an oxygen introduction section while maintaining the same firing temperature.

FIG. 1 is a view for measuring the amount of residual lithium according to an embodiment of the present invention, and is a Warder method which is an alkaline determination method.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the present invention is not limited by the following examples.

≪ Example 1 > NCA-based lithium composite oxide production

A NiCoAlOH precursor was prepared by coprecipitation reaction. Li ₂ CO ₃ was added to the prepared NiCoAlOH precursor, and the temperature was raised to 750 ° C at a rate of 100 ° C / h while air was supplied at a rate of 2L / min, followed by baking at 750 ° C for 6 hours. Then, oxygen-added air was supplied at a rate of 10 L / min and calcined at 750 ° C for 6 hours. In the cooling section, oxygen-added air was supplied at a rate of 10 L / min for 6 hours while cooling at a cooling rate of 100 ° C / h to prepare a lithium composite oxide including Ni, Co, and Al.

≪ Example 2 > NCA-based lithium composite oxide production

Except that the oxygen was supplied at a rate of 10 L / min in all the sections including the temperature rise period, the first temperature holding period, the second temperature holding period, and the cooling period, Li [Ni _0.80 Co _0.15 Al _0.05 ] O ₂ .

≪ Comparative Example 1 &

Li [Ni _0.80 Co _0.15 Al _0.05 ] O ₂ was prepared in the same manner as in Example 1, except that oxygen was not supplied in the entire section including the second temperature holding period in Example 1.

≪ Comparative Example 2 &

In the same manner as in Example 1 except that oxygen was used in the first temperature holding period and the cooling period in Example 1, Li [Ni _0.80 Co _0.15 Al _0.05 ] O ₂ .

<Experimental Example> Residual lithium measurement

The amount of residual lithium was measured by applying the Warder method, an alkaline quantitative method. Specifically, about 10 g of the cathode active material was put into a 250 mL beaker, and about 100 g of DIW was added to the beaker. At this time, the precise weight of the charged cathode active material and DIW was measured and recorded. The beaker carrying the positive electrode active material was stirred for 15 minutes, and the precipitate was filtered using a filter paper to obtain a filtrate. About 50 g of the filtrate was put into an Auto-titrator, which is a precision titration apparatus. The 0.1N HCl solution and the filtrate are added and agitated, and the amount of HCl introduced and pH are displayed. When the pH reached 3 or less, the titration experiment was completed.

Shown in Figure 1 and through the use of experimental graphs, and the pH is measured with extreme changes in EQP1 EQP2, to obtain a residual LiOH and Li ₂ CO _3.

That is, the more the HCl solution injection rate (X axis) in the sample filtrate was increased from 1 pH (Y-axis) is reduced as a black solid line, and the residual LiOH and Li ₂ CO ₃ by applying EQP1 and EQP2 pH is rapidly changed to the following formula .

Each of the above two expressions is as follows.

Q1: HCl input (mL, EQP1)

Q2: HCl input (mL, EQP2-EQP1)

LiOH M.W .: LiOH molecular weight (g / mol)

Li ₂ CO ₃ MW: Li ₂ CO ₃ Molecular weight (g / mol)

HCl con .: concentration of the HCl solution used in the titration (mol / liter)

DIW: DIW Input (g)

Solution: Weight of filtrate used in titration (g)

Powder: weight of cathode sample used in titration (g)

The experimental conditions and the results of the tests performed in Examples 1 and 2 and Comparative Examples 1 and 2 are shown in Table 1 below.

As shown in Table 1, in Examples 1 and 2 in which oxygen was applied to the second temperature holding step, it was confirmed that the residual lithium and discharge capacity characteristics were excellent.

< Example  3> NCM  Lithium complex oxide production

The NiCoMnOH precursor, Ni _{0 . 6} Co _{0 . 2} Mn _{0 . 2} (OH) ₂ . The Ni _{0 . 6} Co _{0 .} Li ₂ CO ₃ was added to the ₂ Mn _{0 .2} (OH) ₂ precursor, and the temperature was raised to 850 ° C. at a rate of 120 ° C./h while supplying air at a rate of 10 L / min. Air was supplied at a rate of 10 L / min. Oxygen was supplied at 10 L / min for 50% of the latter half of the second temperature holding period. In the cooling section, air was naturally cooled at a cooling rate of 120 ° C / h while supplying air at a rate of 10 L / min to produce a lithium composite oxide Li [Ni _0.6 Co _0.2 Mn _0.2 ] O ₂ containing Ni, Co, and Mn Respectively.

< Example  4> NCM  Lithium complex oxide production

Except that the step of firing while feeding air at a rate of 10 L / min in the temperature-raising section and the first temperature-maintaining section in the third embodiment and supplying oxygen at a rate of 10 L / min in the second temperature holding section was performed Lithium composite oxide Li [Ni _0.6 Co _0.2 Mn _0.2 ] O ₂ was prepared in the same manner as in Example 3.

< Example  5> NCM  Lithium complex oxide production

In the same manner as in Example 3, except that oxygen was supplied at a rate of 10 L / min in the temperature rising section, the first temperature holding section, the second temperature holding section and the cooling section in Example 3, Li [Ni _0.80 Co _0.15 Al _0.05 ] O ₂ .

& Lt; Comparative Example 3 >

In Example 3, a lithium composite oxide Li [Ni _0.6 Co _0.2 Mn _0.2 ] O ₂ was prepared in the same manner as in Example 3, except that the oxygen supply process was not performed in the entire section.

< Comparative Example  4>

The lithium composite oxide Li [Ni _0.6 Co _0.2 Mn _0.2 ] was prepared in the same manner as in Example 3, except that the sintering process was performed while supplying oxygen at a rate of 10 L / min only in the first temperature holding period. O ₂ .

The experimental conditions and results of Examples 3 to 5 and Comparative Examples 3 and 4 are shown in Table 2 below.

Claims (3)

Preparing a transition metal precursor;
Mixing the transition metal precursor and a lithium compound; And
Calcining the mixture;
A lithium composite oxide,
The step of firing the mixture includes a temperature rising section, a first temperature holding section, a second temperature holding section, and a cooling section,
The temperature of the first temperature holding period and the temperature of the second temperature holding period are maintained at 700 ° C to 800 ° C for 6 hours,
The temperature of the first temperature holding period and the temperature of the second temperature holding period are the same,
The second temperature holding period is fired in an oxygen-containing atmosphere of 20% by volume to 99% by volume,
Wherein the cooling period is controlled at a cooling rate of 90 占 폚 / h to 110 占 폚 / h.
The method according to claim 1,
Wherein the second temperature maintaining period and the cooling period are fired in an oxygen containing atmosphere of 20 vol% to 99 vol%, and the temperature rising period and the first temperature holding period are fired in an air atmosphere.
The method according to claim 1,
Wherein the temperature rising rate is controlled at a rate of temperature increase of 30 占 폚 / h to 300 占 폚 / h.

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