KR101908082B1 - Coating method for Ni―Co―Mn composite precursor with hetrogeneous metal - Google Patents

Abstract

The present invention relates to a method of coating a heterogeneous element of a nickel-cobalt-manganese composite hydroxide [Ni _x Co _y Mn _1-y (OH) ₂ ], which is a method of simultaneously coating two different elements during a washing step, No separate hetero-element coating process is required. In addition, since it is coated by the liquid phase method, uniform precursor coating is possible.

Description

Coating method for Ni-Co-Mn composite precursor with hetrogenous metal [

The present invention relates to a method for uniformly coating a surface of Ni _x Co _y Mn _1-xy (OH) ₂ , which is a nickel-cobalt-manganese composite precursor used as a cathode active material of a lithium secondary battery, Technology.

Development of new secondary batteries such as a nickel hydride battery and a lithium secondary battery is progressing actively due to the spread of portable small electric and electronic devices. Among them, the lithium secondary battery uses carbon such as graphite as an anode active material, a metal oxide containing lithium as a cathode active material, and a non-aqueous solvent as an electrolyte. Lithium is a highly ionized metal, and is capable of high-voltage development, and is a source of energy for high energy density batteries.

Lithium transition metal oxides containing lithium are mainly used as the positive electrode active material used in the lithium secondary battery, and layered lithium transition metal complex oxides such as cobalt, nickel, ternary system (coexisting cobalt, nickel and manganese) Have been used for more than 90%. For example, Li ₂ CO ₃ and Ni _x Co _y Mn _1-xy (OH) ₂ precursors are mixed and calcined to be used as a cathode material. In general, the Ni _x Co _y Mn _1-xy (OH) ₂ precursor is prepared by coprecipitation. After the nickel salt, manganese salt and cobalt salt are dissolved in distilled water, an aqueous ammonia solution (chelating agent), aqueous NaOH solution ), The Ni _x Co _y Mn _1-xy (OH) ₂ is synthesized as a solid phase and precipitated.

In order to increase the output characteristics of the positive electrode active material of the lithium secondary battery, it is necessary to increase the content of nickel in the positive electrode material. However, when the content of nickel is increased, there is a disadvantage in that stability is deteriorated due to lithium. Particularly, in such a nickel-based lithium composite oxide, nickel content (Ni-rich) composition having a nickel content of more than 50% causes deterioration of battery characteristics due to charging and discharging. This is known to be caused by the elution of nickel from the cathode active material due to the reaction of the anode and the electrolyte, and is known to lead to deterioration of high temperature lifetime characteristics. In addition, structural stability and chemical stability are deteriorated in the nickel-rich (Ni-rich) composition, which is pointed out as a serious problem in the thermal stability of the anode, particularly the deterioration of thermal stability at high temperatures.

In recent years, attempts have been made to improve the thermal stability, capacity and cycle characteristics by replacing a part of the nickel-cobalt-manganese cathode active material precursor with a heterogeneous element or coating the surface of the cathode active material with a hetero element. The degree of improvement is insufficient. For example, Patent Registration No. 10-1493932 discloses a technique for a cathode active material for a lithium secondary battery coated with silicon oxide and a manufacturing method thereof.

In particular, conventionally, in order to coat a nickel / cobalt-manganese cathode active material precursor with a hetero element, nickel / cobalt / manganese cathode active material preparation, cleaning, It was common to go through the cleaning step first.

Korean Patent Registration No. 10-1493932 Korean Patent Registration No. 10-1275845

It is an object of the present invention to provide a coating method of Ni _x Co _y Mn _1-xy (OH) ₂ which is a nickel-cobalt-manganese composite precursor, .

 In particular, it is an object of the present invention to provide a technique in which a nickel-cobalt-manganese composite precursor is coated with a heterogeneous material using another process without the need for a separate coating process.

In the present invention, a transition metal aqueous solution of nickel sulfate, cobalt sulfate and manganese sulfate is prepared by coprecipitation using a complex precursor (Ni _x Co _y Mn _1-xy (OH) ₂ , where 0 <x <1, 0 <y < 0 &lt; x + y &lt;1]; And a step (II) of washing the complex precursor prepared above with a cleaning liquid in which a hetero-element is dissolved in a pressurized filter equipped with a filter and coating a heterogeneous element, and a step (II) of coating a heterogeneous element with a nickel- to provide.

In particular, it is preferable to use an aqueous NaOH solution as the cleaning liquid.

In particular, the heteroelement oxide may be any one or more of metals selected from Ti, Zr, Si, Ce, La, Y, W, Sn, Gd and Nb or oxides thereof.

Particularly, the step (II) comprises the steps of (II-1) laminating the composite precursor to a predetermined thickness on the filter of the pressurized filter provided with a filter on the inner lower side; (II-2) filling the filter with a cleaning liquid containing a different element; And a step (II-3) of passing the cleaning liquid through the filter through pressurization.

In particular, it is preferable to further carry out the step (III) of drying the composite precursor after the step (II).

In particular, the filter is preferably a microsize filter.

Since nickel and cobalt-manganese complex precursors are coated simultaneously with the different elements during the cleaning process, the present invention can reduce the coating cost and time because the process is separately performed after the cleaning process in the prior art.

Further, in the present invention, since the coating of the heterogeneous material is performed through the cleaning liquid in the liquid state, the coating of the heterogeneous material can be uniformly performed on the composite precursor.

1 is a schematic diagram of a pressurized filter 10 for implementing step (II) of the present invention.
2 is a SEM photograph of a nickel-cobalt-manganese composite precursor on which zirconium oxide is surface-coated as a hetero-element produced in Experimental Example.
3 is a SEM photograph of the nickel-cobalt-manganese composite precursor prepared in Comparative Example.
4 is a photograph of the EDS measurement showing the distribution of metal components of the nickel-cobalt-manganese composite precursor surface-coated with zirconium oxide prepared in Experimental Example.

The present invention relates to a nickel-cobalt-manganese composite precursor (Ni _x Co _y Mn _1-xy (OH) ₂ , wherein 0 <x <1, 0 <y <1, 0 <x + y < , And a method for coating the surface of the precursor with a heteroelement.

In the following description, the term "composite precursor" or "precursor" refers to "Ni _x Co _y Mn _1-xy (OH) ₂ where 0 <x <1, 0 <y <1, 0 <x + y <1" , And the heterogeneous element is used as a term for Ni, Co, Mn constituting the composite precursor and a metal other than Li constituting the cathode active material of the lithium secondary battery, which is calcined with the complex precursor. Means various metals or oxides thereof such as Ti, Zr, Si, Ce, La, Y, W, Sn, Gd and Nb.

In the present invention, a transition metal aqueous solution of nickel sulfate, cobalt sulfate and manganese sulfate is prepared by coprecipitation using a complex precursor (Ni _x Co _y Mn _1-xy (OH) ₂ , where 0 <x <1, 0 <y < 0 &lt; x + y &lt;1]; And a step (II) of washing the complex precursor prepared above with a cleaning liquid in which a hetero-element is dissolved in a pressurized filter equipped with a filter and coating a heterogeneous element, and a step (II) of coating a heterogeneous element with a nickel- to provide.

In the present invention as well as the prior art, Ni _x Co _y Mn _1-xy (OH) ₂ is prepared _by coprecipitation using nickel sulfate, cobalt sulfate and manganese sulfate as raw materials for nickel, cobalt and manganese, Can be manufactured. Since the known co-precipitation method can be used for the step (I), a detailed description of the step (I) will be omitted.

The composite precursor prepared in the step (I) is washed using a caustic soda (NaOH) aqueous solution as a cleaning liquid in order to remove impurities such as the sulfur component used in the step (I). The present invention is characterized in that the cleaning liquid component includes a hetero-element so that the coating of the heterogeneous material is simultaneously performed in the cleaning process through the cleaning liquid.

Since the heterogeneous element is coated well on the nickel-cobalt-manganese composite precursor in a high pH environment, high pH, that is, high base condition is formed due to caustic soda used in the cleaning liquid. Therefore, So that cleaning and coating of the heterogeneous material can be performed simultaneously.

Step (II) of the present invention can be further divided into detailed steps. The step (II) comprises the steps of: (II-1) laminating a composite precursor on the filter of a pressurized filter provided with a filter on the inner lower side; (II-2) filling the filter with a cleaning liquid containing the heteroelement; And a step (II-3) in which the cleaning liquid passes through the filter through the pressurization to simultaneously perform cleaning and coating of the dissimilar material.

The detailed steps will be described with reference to the drawings. 1 is a schematic diagram of a pressurized filter 10 for implementing step (II) of the present invention.

The pressurized strainer 10 according to the preferred embodiment of the present invention has an inlet 12 through which a cleaning liquid containing a different element is injected as an upper part of the body 11 as a whole, And each of the inlet 12 and the outlet 13 may further include a conventional valve.

A filter 14 is provided near the inner bottom of the main body 11, and the filter 14 is preferably a micro pore size. The filter 14 may be various filters 14 having micro-sized pores such as a nonwoven fabric, a ceramic filter, and a polymer filter.

The composite precursor particles 20 prepared in the previous step are laminated on the filter 14.

For example, a NaOH aqueous solution containing a hetero-element is filled in the composite precursor particles 20 so that the composite precursor particles 20 are sufficiently immersed.

The pressurized filter 10 of the present invention is provided with a pressurizing means. For example, a pressurizing device 15 using a pneumatic pressure may be provided. For example, by injecting N ₂ , which is an inert gas from the outside, into the pressurized filter 10 of the present invention at a high pressure to maintain the high pressure in the pressurized filter 10, the cleaning liquid 30 passes through the filter 14, 13 to the outside.

Further, the step (III) of drying the complex precursor after the step (II) may be further carried out.

Hereinafter, the present invention will be described with reference to Examples and Experimental Examples.

Example

Nickel sulfate, cobalt sulfate, and manganese sulfate were mixed at a ratio (molar ratio) of 0.8: 0.1: 0.1 to prepare a 2.5 M transition metal aqueous solution, and a 50% aqueous solution of sodium hydroxide was prepared. The transition metal aqueous solution was supplied to a 100 L coprecipitated reactor having a dual tank structure containing ion-removing water maintained at 50 to 60 ° C at a rate of 6.5 to 7.0 L / hr, and the pH of the coprecipitated reactor was maintained at 10.5 to 11.0 The aqueous sodium hydroxide solution was added. As the additive, ammonia aqueous solution of 28% concentration was supplied with 3 L before introducing the transition metal aqueous solution. The coprecipitation reaction was carried out for 12 hours by the batch type coprecipitation method in which the nickel-cobalt-manganese complex hydroxide was allowed to stand for 3 hours and the supernatant liquid was removed.

After the reaction was completed, the coprecipitates reacted for 12 hours to remove the reaction solution except the nickel-cobalt-manganese hydroxide in the pressure filter.

To 200 ~ 300 L of 5 ~ 10% caustic soda aqueous solution to remove sulfuric acid ion (SO ₄ ^2- ) in the nickel-cobalt-manganese hydroxide from which the reaction solution was removed, Of zirconium oxide were dispersed in an amount of 10 to 20%. The caustic soda aqueous solution and the aqueous zirconium oxide solution were removed by applying pressure to the pressurized filter, then washed several times with deionized water and dried in a constant temperature drier at 120 ° C. for 24 hours to obtain a nickel-cobalt-manganese composite hydroxide &Lt; / RTI &gt;

Comparative Example

Nickel sulfate, cobalt sulfate, and manganese sulfate were mixed at a ratio (molar ratio) of 0.8: 0.1: 0.1 to prepare a 2.5 M transition metal aqueous solution, and a 50% aqueous solution of sodium hydroxide was prepared. The transition metal aqueous solution was supplied to a 100 L coprecipitated reactor having a dual tank structure containing ion-removing water maintained at 50 to 60 ° C at a rate of 6.5 to 7.0 L / hr, and the pH of the coprecipitated reactor was maintained at 10.5 to 11.0 The aqueous sodium hydroxide solution was added. As the additive, ammonia aqueous solution of 28% concentration was supplied with 3 L before introducing the transition metal aqueous solution. The coprecipitation reaction was carried out for 12 hours by the batch type coprecipitation method in which the nickel-cobalt-manganese complex hydroxide was allowed to stand for 3 hours and the supernatant liquid was removed.

After completion of the reaction, the nickel-cobalt-manganese complex hydroxide prepared by the reaction for 12 hours was washed several times with deionized water and dried in a constant temperature drier at 120 ° C for 24 hours to obtain nickel-cobalt-manganese complex hydroxide.

Experimental Example 1

2 is a SEM photograph of a nickel-cobalt-manganese composite precursor hydroxide surface-coated with zirconium oxide prepared in Experimental Example. The size of nickel - cobalt - manganese hydroxide was 8.3 ㎛.

Experimental Example 2

3 is a SEM photograph of the nickel-cobalt-manganese hydroxide prepared in Comparative Example. The size of nickel-cobalt-manganese hydroxide was 8.2 ㎛.

Experimental Example 3

4 is an EDS measurement photograph showing the distribution of metal components of the nickel-cobalt-manganese hydroxide surface-coated with zirconium oxide prepared in Experimental Example. Referring to FIG. 4, it was confirmed that zirconium oxide was uniformly coated on the surface of the nickel-cobalt-manganese hydroxide.

Experimental Example 4

Table 1 shows the results of ICP component analysis of the nickel-cobalt-manganese hydroxide prepared in Experimental Examples and Comparative Examples. The content ratio of Zr added in the molar ratio of 1.0 with respect to the total metal was close to the theoretical value and it was judged that the method of preparing nickel-cobalt-manganese hydroxide having the zirconium oxide surface-coated was an effective method for coating the additive component.

Claims (6)

The transition metal aqueous solution of nickel sulfate, cobalt sulfate and manganese sulfate is prepared by coprecipitation with a complex precursor [Ni _x Co _y Mn _1-xy (OH) ₂ , where 0 <x <1, 0 <y < + y &lt;1]; And
And a step (II) of washing the composite precursor prepared above with a cleaning liquid in which zirconium oxide is dissolved as a heteroelement in a pressurized filter equipped with a filter, and coating the zirconium oxide with the cleaning solution, wherein the zirconium oxide is a heterogeneous mixture of nickel-cobalt-manganese complex precursor Element coating method.
The method of claim 1, wherein the cleaning liquid comprises an aqueous solution of NaOH.
delete The method of claim 1, wherein step (II) comprises:
(II-1) laminating the composite precursor on the filter of a pressure-type filter provided with a filter on the inner lower side;
(II-2) filling a cleaning liquid containing zirconium oxide as a different element into the pressurized filter; And
And (II-3) passing the cleaning liquid through the filter through a pressurizing process. The method for coating a hetero-element of a nickel-cobalt-manganese composite precursor according to claim 1,
The method of claim 1, further comprising a step (III) of drying the composite precursor after the step (II).
The method of claim 1, wherein the filter is a filter having a micro pore size.

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