KR20160076037A - Process for the production of lithium complex oxide and lithium complex oxide made by the same, and lithium ion batteries comprising the same - Google Patents

Abstract

The present invention relates to a producing method of a lithium composite oxide, a lithium composite oxide produced thereby, and a non-aqueous electrolyte secondary battery comprising the same. The producing method of a lithium composite oxide according to the present invention can produce the lithium composite oxide having a core with a high content of nickel and a shell structure by impregnating the core into an aqueous solution for forming a shell including manganese or aluminum after producing the core with high content of nickel.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithium composite oxide, a lithium composite oxide, and a nonaqueous electrolyte secondary battery comprising the lithium composite oxide. 2. Description of the Related Art [0002]

The present invention relates to a method for producing a lithium composite oxide, a lithium composite oxide produced thereby, and a nonaqueous electrolyte secondary battery comprising the same.

Recently, miniaturization of electronic devices has been diversified into mobile phones, notebook computers (PCs), and portable personal digital assistants (PDAs), and the interest in energy storage technology has been increasing.

In addition, in the case of batteries used in hybrid vehicles (HEV) and electric vehicles (EV), not only high capacity and high output, but also stability are a big problem. As application fields expand, research and development on storage technologies are being actively carried out. In this respect, there is a growing interest in the development of secondary batteries capable of charging and discharging.

The secondary battery is composed of a positive electrode, a negative electrode, and an electrolyte, and the ratio of the positive electrode is the most important. The cathode material is a cathode active material and generally has a high energy density during charging and discharging, and the structure should not be destroyed by intercalation or desorption of reversible lithium ions. In addition, the electrical conductivity should be high, and the chemical stability of the organic solvent used as the electrolyte should be high. It should be a material that has low manufacturing cost and minimizes environmental pollution problems.

Examples of the positive electrode active material of such a lithium ion secondary battery include lithium nickel oxide (LiNiO2), lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMnO2), and the like, which are layered compounds capable of intercalating and deintercalating lithium ions. Lithium nickel oxide (LiNiO2) has a high electric capacity, but it has not been put to practical use due to problems such as cycle characteristics and stability during charging and discharging. In addition, lithium cobalt oxide (LiCoO 2) has an advantage of being excellent in cycle life and rate capability as well as capacity, and being easy to synthesize. However, the high price of cobalt and harmful to human body and thermal instability .

To overcome these disadvantages, there is a composite metal oxide of nickel-cobalt-manganese as a material having a layered crystal structure. However, since the cost of cobalt (Co) is high and harmful to the human body, LiMO 3 LiMXO 2 (where M = metal such as Ni, Mn, Cr) decreases the amount of cobalt (Co) Thackeray's work is currently being studied, and current research is underway at home and abroad.

Solid phase method and coprecipitation method are used as general methods for preparing such composite metal oxides. Solid phase method is difficult to obtain uniform composition due to high influx of impurities during mixing, and high temperature and manufacturing time are long.

On the other hand, the coprecipitation method uses an aqueous solution containing nickel (Ni), cobalt (Co) and manganese (Mn) and sodium hydroxide used as a co-precipitant, and a chelating agent as a complexing agent, Is mixed with a lithium salt and fired to obtain a cathode active material.

However, the coprecipitation method overcomes the drawbacks of the solid phase method in that it obtains a homogeneous composition in terms of the characteristics of the material. However, since the particle size of the active material is influenced by the particle size of the precursor, Therefore, there is a problem that a lot of effort and time are required in the optimization process.

It is another object of the present invention to provide a method for preparing a lithium composite oxide having a core shell structure by combining a coprecipitation method and a solid phase mixing method in order to solve the problems of the prior art.

The present invention also aims to provide the lithium composite oxide particles produced by the production method of the present invention.

DISCLOSURE OF THE INVENTION In order to solve the above problems,

A first step of preparing a precursor represented by Formula 1 below;

Ni _b Co _c M _d ( _b? 0.8, _c? 0.2, _d ? 0.2, and M is Al or Mn)

A second step of adding the precursor to a solution for forming a shell part and stirring to prepare a mixed solution; A third step of drying the mixed solution to prepare a shell-coated particle on the surface of the precursor; A fourth step of mixing the lithium compound; A fifth step of performing a first heat treatment at a temperature of 500 to 700 캜; A sixth step of cleaning; And a second heat treatment at a temperature of 700 to 850 캜; And a method for producing the lithium composite oxide.

In the method for producing a lithium composite oxide according to the present invention, the solution for forming the shell part comprises a compound represented by the following formula (2).

???????? Ni _b Co _c M _d ( _b? 0.1, _c? 0.1, _d ? 0.3, and M is Al or Mn)

The solution for forming the shell portion includes Ni and Co, and further contains Mn or Al.

In the method for producing a lithium composite oxide according to the present invention, in the step of mixing the precursor and the solution for forming a shell part to prepare a mixed solution, the precursor is rapidly dried under reduced pressure.

In the method for producing a lithium composite oxide according to the present invention, the first heat treatment step and the second heat treatment step are characterized in that the heat treatment is performed in an atmosphere containing 50 vol% or more of oxygen.

The present invention also provides a lithium composite oxide produced by the process according to the present invention.

The method for producing a lithium composite oxide according to the present invention can produce a lithium composite oxide having a core and a shell structure having a high nickel content by impregnating the core with an aqueous solution for forming a shell by coprecipitation.

FIGS. 1 to 3 show SEM photographs of the precursor and active material particles prepared in the examples of the present invention.
4 shows the XRD measurement results of the particles prepared in the examples of the present invention and the particles prepared in the comparative example.
FIGS. 5 to 10 show the results of measurement of the capacity characteristics and the life characteristics of a battery including the particles prepared in Examples and Comparative Examples of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Throughout the specification, when a part is referred to as being "connected" to another part, it includes not only "directly connected" but also "indirectly connected" . Also, when an element is referred to as "comprising ", it means that it can include other elements, not excluding other elements unless specifically stated otherwise.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The present invention relates to a process for preparing a precursor represented by the following general formula (1):

Ni _b Co _c M _d ( _b? 0.8, _c? 0.2, _d ? 0.2, and M is Al or Mn)

A second step of adding the precursor to a solution for forming a shell part and stirring to prepare a mixed solution; A third step of drying the mixed solution to prepare a shell-coated particle on the surface of the precursor; A fourth step of mixing the lithium compound; A fifth step of performing a first heat treatment at a temperature of 500 to 700 캜; A sixth step of cleaning; And a second heat treatment at a temperature of 700 to 850 캜; And a method for producing the lithium composite oxide.

The precursor Ni _b Co _c M _d ( _b ? 0.8, _c? 0.2, _d ? 0.2 and M is Al or Mn) prepared in the first step is reacted with a nickel compound, a cobalt compound and a metal compound by a coprecipitation reaction Can be manufactured.

The nickel compound may be at least one selected from the group consisting of Ni (OH) 2, NiO, NiOOH, NiCO3.2Ni (OH) 2 .4H2O, NiC2O4.2H2O, Ni (NO3) 2-6H2O, NiSO4, NiSO4.6H2O, . Among them, Ni (OH) 2, NiO, NiOOH, NiCO3. 2Ni (OH) 2 .4H2O, NiC2O4. 2H2O which do not contain a nitrogen source or a sulfur atom in that they do not generate harmful substances such as NOx and SOx, Are preferred. Further, Ni (OH) 2, NiO, and NiOOH are particularly preferable from the viewpoint of being available at low cost as an industrial raw material and high reactivity. These nickel compounds may be used singly or in combination of two or more.

The cobalt compound may be selected from the group consisting of Co (OH) 2, CoO, Co 2 O 3, Co 3 O 4, CoCOOH, Co (OCOCH 3) 2 揃 4H 2 O, CoCl 2, Co (NO 3) 2 揃 6H 2 O, Co (SO 4) 2 揃 7H 2 O have. Of these, Co (OH) 2, CoO, Co2O3, and Co3O4 are preferable in that no harmful substances such as NOx and SOx are generated during the firing process. More preferably, it is Co (OH) 2 in that it is commercially available at a low cost and has high reactivity. These cobalt compounds may be used singly or in combination of two or more.

The manganese compound may be a manganese oxide such as Mn2O3, MnO2 or Mn3O4, a manganese salt such as MnCO3, Mn (NO3) 2, MnSO4, manganese acetate, manganese dicarboxylate, manganese citrate or manganese fatty acid, oxyhydroxide, Cargo, and the like. Of these manganese compounds, MnO2, Mn2O3 and Mn3O4 are preferable because they can be obtained at low cost as industrial raw materials without generating gases such as NOx, SOx and CO2 when the calcination is carried out. These manganese compounds may be used singly or in combination of two or more.

The aluminum compound may be one selected from the group consisting of sodium aluminate, sodium aluminate, aluminum aluminate, and aluminum hydroxide, or may be used in combination of two or more.

In the second step, the precursor prepared in the first step may be added to a solution for forming a shell part and stirred to prepare a mixed solution.

The solution for forming the shell part can be prepared by dissolving the shell part in distilled water of 40 to 50% of the precursor volume of 100%. The component of the shell portion may be a Ni-Co-Mn compound or a Ni-Co-Al compound. When the precursor is added to the prepared solution for forming the shell portion and stirring is performed, the mixture at the completion of the addition of the precursor may be in the form of a powder, not a liquid phase such as slurry, and a smooth form of clay.

The drying method is not particularly limited, but it is possible to carry out the drying step at 130 to 200 ° C after impregnating the surface of the precursor with a metal aqueous solution of the surface of the precursor through depressurization before drying, and as shown in the SEM photograph of FIG. 1, The shape of the precursor after drying shows that a shell portion of a certain thickness is formed on the surface.

In the third step, the mixed solution prepared in the second step may be dried to produce coated particles having a shell part formed on the surface of the precursor.

The mixture of the clay phase prepared in the second step may be rapidly dried in a vacuum chamber under a reduced pressure condition, that is, under a reduced pressure condition for 30 minutes to 3 hours, and the rapid drying is preferably performed using a fluidized bed dryer. Through the rapid drying step, the core may contain the precursor, and particles having a shell portion coated on the surface of the precursor may be recovered.

In the fourth step, a lithium compound may be mixed with the core-shell particles produced in the third step.

Wherein the lithium compound is at least one selected from the group consisting of Li2CO3, LiNO3, LiNO2, LiOH, LiOH.H2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, Li acetate, Li dicarboxylic acid Li, citric acid Li, And a lithium halide. Of these, lithium carbonate is preferable because it is easy to handle and is inexpensive.

The method of mixing the lithium compound is not particularly limited, but it is possible to mix the particles coated with the shell on the surface of the precursor and the lithium compound using a Henschel mixer. The lithium compound has a particle diameter of 1 탆 or less, Is preferable.

In the fifth step, the particles coated with the shell on the surface of the precursor in which the lithium compound is mixed may be firstly subjected to a first heat treatment at a temperature of 500 to 700 ° C.

In the fifth step, the temperature raising rate of the first heat treatment may be maintained at a temperature of 500 to 700 ° C for 1 to 5 hours so that the lithium compound may be melted at a mild condition of 1 to 5 ° C / min. If the rate of temperature increase exceeds 5 DEG C / min, the precursor and shell portion may be peeled off or damaged due to rapid temperature changes.

The washing process of the sixth step may be performed using distilled water and ethanol as a medium, and may be stirred and filtered at 300 to 450 rpm for 5 to 15 minutes.

In the seventh step, the second annealing may be performed at a temperature of 700 to 850 ° C to perform the second annealing.

If the second heat treatment temperature is less than 700 ° C in the seventh step, the bulk density or the specific surface area may become excessively large. If the second heat treatment temperature is higher than 850 ° C, the primary particles may be excessively grown.

Meanwhile, the second firing may be performed in a mixed gas containing 50% or more of oxygen or an oxygen atmosphere for 5 to 20 hours. If the baking time is less than 5 hours, the crystallinity of the shell-coated particles on the surface of the precursor may deteriorate. If the baking time is more than 20 hours, it may become uneconomical or pulverization may become difficult.

After the seventh step, a cathode material coated with the shell portion of the precursor can be obtained within a range in which the surface damage of the particles is minimized through pulverization / classification equipment.

Hereinafter, embodiments of the present invention will be described in detail.

< Example  1>

Following the general co-precipitation method it was synthesized precursor represented by _{Ni 0 .88 Co 0 .12 (OH} ) 2. The Mn solution was prepared as the solution for forming the shell part, and the precursor particles represented by the Ni _0.88 Co _0.12 (OH) ₂ were impregnated with the shell part forming solution so that the liquid ratio ratio became 4 to 6, and then dried rapidly in the fluidized bed dryer.

After mixed with a lithium compound and heat-treated in an oxygen atmosphere of 50% _{LiNi 0 .70 Co 0 .10 Mn 0} .20 O 2 Was prepared. &Lt; tb &gt;&lt; TABLE &gt;

< Example  2>

A precursor represented by _{Ni 0 .90 Co 0 .10 (OH} ) 2 according to the coprecipitation method was synthesized.

After preparing a solution of Mn for the shell part formed solution, solid-liquid ratio of the _{Ni 0 .88 Co 0 .12 (OH} ) shell part of the precursor particles, represented by a _second impregnation such that the formed solution for from 4 to 6, in the fast fluidized bed dryer Lt; / RTI &gt;

After mixing with a lithium compound and heat-treated in an oxygen atmosphere of 50% by _{LiNi 0 .82 Co 0 .09 Mn 0} .09 O 2 Was prepared. &Lt; tb &gt;&lt; TABLE &gt;

< Example  3>

A precursor represented by _{Ni 0 .88 Co 0 .12 (OH} ) 2 according to the coprecipitation method was synthesized.

After preparing a solution of Al for the shell part formed solution, solid-liquid ratio of the _{Ni 0 .88 Co 0 .12 (OH} ) shell part of the precursor particles, represented by a _second impregnation such that the formed solution for from 4 to 6, in the fast fluidized bed dryer Lt; / RTI &gt;

After mixing with a lithium compound and heat-treated in an oxygen atmosphere of 50% by _{LiNi 0 .82 Co 0 .09 Mn 0} .09 O 2 Was prepared. &Lt; tb &gt;&lt; TABLE &gt;

< Comparative Example >

Comparative Example as the concentration of the transition metal throughout the particles by co-precipitation _{LiNi 0 .8 Co 0 .10 Mn 0} .10 O 2 To produce certain active material particles.

< Experimental Example  1> SEM  Photo measurement

SEM photographs of the precursor and lithium composite oxide particles prepared in Examples 1 to 3 were measured, and the results are shown in FIGS. 1 to 3.

1 to 3, it is confirmed that a shell part is formed on the surface after coating with the solution for forming a shell part.

< Experimental Example  2> XRD  Photo measurement

The XRD of the particles prepared in Example 1 and the particles prepared in Comparative Example were measured and the results are shown in FIG.

In FIG. 4, it can be seen that the crystal structures of the particles prepared in Examples and Comparative Examples are the same.

< Manufacturing example  1> Battery manufacturing

The batteries including the active materials prepared in Examples 1 and 2 and the active materials prepared in Comparative Examples were manufactured and their charge / discharge characteristics and life characteristics were measured. The results are shown in FIGS. 5 to 8.

< Manufacturing example  2> Battery manufacturing

9 and 10 show the results of measuring the charge-discharge characteristics and the life characteristics of the battery by preparing the battery including the active material prepared in Example 3 and the active material prepared in Comparative Example.

< Experimental Example  3> Comparison of discharge capacity

5, compared to the discharge capacity of the battery including the active material having the Ni content of 88% in the core portion manufactured in Example 1, the Ni content of the core portion manufactured in Example 2 shown in FIG. 6 was 90% It can be confirmed that the discharge capacity of the battery including the battery is increased.

< Experimental Example  4> Comparison of cycle characteristics

7, compared with the cycle characteristics of the battery including the active material having the Ni content of 88% in the core portion manufactured in Example 1, the Ni content of the core portion produced in Example 2 shown in FIG. 8 was 90% It is confirmed that the cycle characteristics of the battery including the battery are improved.

< Experimental Example  5> Comparison of discharge capacity

As shown in Fig. 9, the charge / discharge capacities of bulk Ni-Co-Al having the same composition as the Ni content of 85% and Ni-Co-Al of the core-shell portion are different between 4.1 V and 3.7 V can confirm. In the case of the Ni-Co-Al battery in the core-shell portion, the phase change is suppressed at a high voltage of 4.1 V or higher compared with the battery containing the bulk Ni-Co-Al, and the average discharge voltage rises at a low voltage of 3.7 V or lower It can be seen that the energy density is improved.

< Experimental Example  6> Comparison of cycle characteristics

As shown in FIG. 10, when the efficiency of the battery including the bulk Ni-Co-Al having the same composition as the Ni content of 85% and the Ni-Co-Al of the core-shell portion was compared at 50 cycles, -Al was improved compared to the battery containing bulk Ni-Co-Al.

Claims (7)

A first step of preparing a precursor represented by Formula 1 below;
Ni _b Co _c M _d ( _b? 0.8, _c? 0.2, _d ? 0.2, and M is Al or Mn)
A second step of adding the precursor to a solution for forming a shell part and stirring to prepare a mixed solution;
A third step of drying the mixed solution to prepare a shell-coated particle on the surface of the precursor;
A fourth step of mixing the lithium compound;
A fifth step of performing a first heat treatment at a temperature of 500 to 700 캜;
A sixth step of cleaning; And
A seventh step of performing a second heat treatment at a temperature of 700 to 850 캜; &Lt; / RTI &gt;
The method according to claim 1,
Wherein the solution for forming the shell part in the second step comprises a compound represented by the following formula (2).
???????? Ni _b Co _c M _d ( _b? 0.1, _c? 0.1, _d ? 0.3, and M is Al or Mn)
The method according to claim 1,
And the second step is rapid drying under reduced pressure conditions.
The method according to claim 1,
Wherein the first heat treatment step and the second heat treatment step are performed in an atmosphere having an oxygen content of 50 vol% or more.
A lithium composite oxide produced by the production method of any one of claims 1 to 4.
A cathode material for a nonaqueous electrolyte secondary battery comprising a lithium composite oxide produced by the method of any one of claims 1 to 4.
A nonaqueous electrolyte secondary battery comprising the lithium composite oxide produced by the production method of any one of claims 1 to 4.

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