KR102176654B1 - 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 method of manufacturing a lithium composite oxide, a lithium composite oxide prepared thereby, and a nonaqueous electrolyte secondary battery including the same.
In the method for producing a lithium composite oxide according to the present invention, after preparing a core having a high nickel content, a lithium composite oxide having a core and shell structure having a high nickel content is prepared by impregnating it in an aqueous solution for forming a shell containing manganese or aluminum. I can.

Description

Manufacturing method of lithium composite oxide, lithium composite oxide produced thereby, and a non-aqueous electrolyte secondary battery including the same.

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

Recently, miniaturization of electronic devices has been increasingly diversified into mobile phones, notebooks (PCs), and portable personal information terminals (PDAs), and accordingly, interest in energy storage technology is increasing.

In addition, in the case of batteries used in hybrid vehicles (HEVs) and electric vehicles (EVs), stability as well as high capacity and high output remains a major task. As the application field is expanded, research and development on storage technology are being actively conducted. In this respect, interest in the development of a secondary battery capable of charging and discharging is increasing.

The secondary battery is composed of a positive electrode, a negative electrode, and an electrolyte, and the ratio of the positive electrode is the highest and most important. The positive electrode material is a positive electrode 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 must be high, and the chemical stability of the organic solvent used as an electrolyte must be high. And it should be a material that has low manufacturing cost and minimizes environmental pollution problems.

Examples of positive electrode active materials for lithium ion secondary batteries include lithium nickel acid (LiNiO2), lithium cobaltate (LiCoO2), lithium manganate (LiMnO2), and the like, which are layered compounds capable of intercalating and desorbing lithium ions. Among them, lithium nickel oxide (LiNiO2) has a high electric capacity, but it has problems in cycle characteristics and stability during charging and discharging, so it is not being put into practical use. In addition, lithium cobalt oxide (LiCoO2) has the advantage of not only having a large capacity, but also excellent cycle life and rate capability, and easy synthesis, but the high cost of cobalt, harmful to the human body, and thermal instability at high temperatures, etc. It has its drawbacks.

In order to compensate for these drawbacks, 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 expensive and is harmful to the human body, LiMO3 LiMXO2 (here, metals such as M = Ni, Mn, Cr) by reducing the amount of cobalt (Co) and increasing the amount of manganese (Mn) Research on structured materials has been published by Thackeray, and domestic and international research is actively underway.

As a general manufacturing method for preparing such a composite metal oxide, a solid-phase method and a coprecipitation method are used, but the solid-phase method has a disadvantage in that it is difficult to obtain a uniform composition due to a large amount of impurities during mixing, and a high temperature and a long manufacturing time during manufacturing.

On the other hand, in the coprecipitation method, an aqueous solution containing nickel (Ni), cobalt (Co), and manganese (Mn) and sodium hydroxide used as a coprecipitation agent are used, and a chelating agent is used as a complexing agent to precipitate a precursor obtained at the same time. This is a method of obtaining a positive electrode active material by mixing with lithium (Li) salt and firing.

However, the coprecipitation method overcomes the disadvantages of the solid phase method in that it obtains a uniform composition in terms of the characteristics of the material, but the particle size of the active material is affected by the particle size of the precursor, and the synthesis process has many process variables and the process is complicated. Therefore, there is a problem that a lot of effort and time are required in the optimization process.

An object of the present invention is to provide a new method for producing a lithium composite oxide in which a coprecipitation method and a solid phase mixing method are combined in preparing a lithium composite oxide having a core-shell structure in order to solve the problems of the prior art as described above.

Another object of the present invention is to provide a lithium composite oxide particle manufactured by the manufacturing method of the present invention.

The present invention to solve the above problems

A first step of preparing a precursor represented by the following Chemical Formula 1;

[Formula 1] Ni _b Co _c M _d (OH) ₂ (b≥0.8, c≤0.2, d≤0.2, and M is Al or Mn)

A second step of preparing a mixed dispersion while adding the precursor to the solution for forming a shell portion and stirring; A third step of drying the mixed dispersion to prepare particles having a shell portion coated 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°C; A sixth step of washing; And a seventh step of performing a second heat treatment at a temperature of 700 to 850°C. It provides a method for producing a lithium composite oxide comprising a.

In the method for producing a lithium composite oxide according to the present invention, the solution for forming a shell portion is characterized in that it contains a compound represented by the following formula (2).

[Formula 2] Ni _b Co _c M _d (b≤0.1, c≤0.1, d≤0.3, M is Al or Mn)

The solution for forming the shell part comprises Ni and Co, and further comprises Mn or Al.

In the method for producing a lithium composite oxide according to the present invention, in the step of preparing a mixed solution by mixing the precursor and the solution for forming a shell portion, it is characterized in that rapid drying under reduced pressure.

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

The present invention also provides a lithium composite oxide prepared by the production method according to the present invention.

In the method for producing a lithium composite oxide according to the present invention, a core is prepared by a coprecipitation method and then impregnated in an aqueous solution for forming a shell, thereby producing a lithium composite oxide having a core and shell structure having a high nickel content.

1 to 3 show SEM photographs of precursors and active material particles prepared in an embodiment of the present invention.
4 shows the results of measuring the XRD of the particles prepared in Examples and Comparative Examples of the present invention.
5 to 10 show the results of measuring capacity characteristics and life characteristics of batteries including particles prepared in Examples and Comparative Examples of the present invention.

Hereinafter, the present invention will be described with reference to the accompanying drawings. However, the present invention may be implemented in various different forms, and therefore is not limited to the embodiments described herein. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and similar reference numerals are assigned to similar parts throughout the specification.

Throughout the specification, when a part is said to be "connected" to another part, this includes not only "directly connected" but also "indirectly connected" with another member interposed therebetween. . In addition, when a part "includes" a certain component, it means that other components may be further provided, rather than excluding other components unless specifically stated to the contrary.

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

The present invention is a first step of preparing a precursor represented by the following formula (1);

[Formula 1] Ni _b Co _c M _d (OH) ₂ (b≥0.8, c≤0.2, d≤0.2, and M is Al or Mn)

A second step of preparing a mixed dispersion while adding the precursor to the solution for forming a shell portion and stirring; A third step of drying the mixed dispersion to prepare particles having a shell portion coated on the surface of the precursor; A fourth step of mixing the lithium compound; A fifth step of first heat treatment at a temperature of 500 to 700°C; A sixth step of washing; And a seventh step of performing a second heat treatment at a temperature of 700 to 850°C. It can provide a method for producing a lithium composite oxide comprising a.

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 a nickel compound, a cobalt compound, and a metal compound by coprecipitation reaction. Can be manufactured.

The nickel compound includes Ni(OH)2, NiO, NiOOH, NiCO3·2Ni(OH)2·4H2O, NiC2O4·2H2O, Ni(NO3)2·6H2O, NiSO4, NiSO4·6H2O, fatty acid nickel, and nickel halide. Can be lifted. Among them, Ni(OH)2, NiO, NiOOH, NiCO3·2Ni(OH)2·4H2O, NiC2O4·2H2O, which do not contain nitrogen or sulfur atoms, do not generate harmful substances such as NOx and SOx when firing. Nickel compounds such as are preferred. In addition, Ni(OH)2, NiO, and NiOOH are particularly preferable from the viewpoint of being able to obtain inexpensively as industrial raw materials and from the viewpoint of high reactivity. These nickel compounds may be used alone or in combination of two or more.

The cobalt compound may be selected from the group consisting of Co(OH)2, CoO, Co2O3, Co3O4, CoCOOH, Co(OCOCH3)2·4H2O, CoCl2, Co(NO3)2·6H2O, Co(SO4)2·7H2O. have. Among them, Co(OH)2, CoO, Co2O3, and Co3O4 are preferable in that they do not generate harmful substances such as NOx and SOx during the firing process. More preferably, it is Co(OH)2 in terms of industrially inexpensive availability and high reactivity. These cobalt compounds may be used alone or in combination of two or more.

The manganese compounds include manganese oxides such as Mn2O3, MnO2, Mn3O4, MnCO3, Mn(NO3)2, MnSO4, manganese acetate, manganese dicarboxylic acid, manganese citrate, and manganese salts such as fatty acid manganese, oxyhydroxides, and halogens such as manganese chloride. And cargo. Among these manganese compounds, MnO2, Mn2O3 and Mn3O4 are preferable because they do not generate gases such as NOx, SOx, and CO2 during the firing process, and can be obtained inexpensively as industrial raw materials. These manganese compounds may be used alone or in combination of two or more.

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

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

The solution for forming the shell portion may be prepared by dissolving a component of the shell portion in distilled water of 40 to 50% relative to 100% of the precursor volume. The component of the shell part may be a Ni-Co-Mn-based compound or a Ni-Co-Al-based compound. When the precursor is added to the prepared solution for forming a shell portion to proceed with stirring, the mixture may have a soft clay-like form that is neither a powdery nor a liquid such as a slurry when the precursor is added.

The drying method is not particularly limited, but after impregnating the surface of the precursor particles with the metal aqueous solution through reduced pressure treatment before drying, the drying process may be performed at 130 to 200°C. As shown in the SEM image of FIG. After drying of the precursor, it can be seen that a shell portion having a predetermined thickness is formed on the surface.

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

After maintaining the clay mixture prepared in the second step in a negative pressure state, that is, under reduced pressure conditions for 30 minutes to 3 hours, it may be rapidly dried, and the rapid drying is preferably a fluid bed dryer. Through the rapid drying step, the core includes 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 prepared in the third step.

The lithium compound is Li2CO3, LiNO3, LiNO2, LiOH, LiOH.H2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, acetic acid Li, dicarboxylic acid Li, citric acid Li, fatty acid Li, alkyl lithium, And lithium halides, and among them, lithium carbonate is preferred because of its ease of handling and low cost.

The method of mixing the lithium compound is not particularly limited, but the particles coated with the shell portion on the surface of the precursor and the lithium compound may be mixed using a Hansel mixer, and the lithium compound having a particle diameter of 1 μm or less is uniformly mixed. It is preferable in that this is possible.

In the fifth step, the particles having the shell portion coated on the surface of the precursor mixed with the lithium compound may be subjected to a first heat treatment at a temperature of 500 to 700° C. to perform the first firing.

In the fifth step, the heating rate of the first heat treatment may be maintained for 1 to 5 hours at a temperature of 500 to 700° C. so that the lithium compound can be dissolved under mild conditions of 1 to 5° C./min. When the temperature increase rate exceeds 5°C/min, the precursor and the shell portion may be peeled off or damaged due to a rapid temperature change.

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

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

In the seventh step, if the second heat treatment temperature is less than 700°C, the bulk density may be small or the specific surface area may be excessively large, and if it exceeds 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 firing time is less than 5 hours, crystallinity of the particles coated with the shell portion on the surface of the precursor may deteriorate, and if it exceeds 20 hours, it may be uneconomical or difficult to pulverize.

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

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

< Example 1>

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

After that, it was mixed with a lithium compound and heat-treated in an oxygen 50% atmosphere to obtain LiNi _{0 .70} Co _{0 .10} Mn _{0 .20} O ₂ A lithium composite oxide particle represented by was prepared.

< Example 2>

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

Prepare the Mn solution as the solution for forming the shell part, and impregnate the precursor particles represented by the Ni _{0 .88} Co _{0 .12} (OH) ₂ into the solution for forming the shell part so that the solid-liquid ratio is 4 to 6, and then rapidly in a fluidized bed dryer. Dried.

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 A lithium composite oxide particle represented by was prepared.

< 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 Dried.

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 A lithium composite oxide particle represented by was prepared.

< Comparative example >

As a comparative example, the concentration of the transition metal in the entire particle by the coprecipitation method was LiNi _{0 .8} Co _{0 .10} Mn _{0 .10} O ₂ To prepare a constant active material particle.

< 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.

It can be seen from FIGS. 1 to 3 that a shell part is formed on the surface after coating with a solution for forming a shell part.

< Experimental example 2> XRD Photo measurement

XRD of the particles prepared in Example 1 and the particles prepared in Comparative Example were measured, and the results are shown in FIG. 4.

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

A battery including the active material prepared in Examples 1 and 2 and the active material prepared in Comparative Example was prepared, and results of measuring the charge/discharge characteristics and life characteristics of the battery are shown in FIGS. 5 to 8.

< Manufacturing example 2> battery manufacturing

A battery including the active material prepared in Example 3 and the active material prepared in Comparative Example was prepared, and results of measuring the charge/discharge characteristics and life characteristics of the battery are shown in FIGS. 9 and 10.

< Experimental example 3> Comparison of discharge capacity

The active material in which the Ni content of the core part prepared in Example 2 shown in FIG. 6 is 90% compared to the discharge capacity of the battery including the active material having the Ni content of 88% in the core part prepared in Example 1 shown in FIG. It can be seen that the discharge capacity of the battery including the increased.

< Experimental example 4> Comparison of cycle characteristics

Compared to the cycle characteristics of the battery including the active material having an Ni content of 88% in the core part prepared in Example 1 shown in FIG. 7, the active material having a Ni content of 90% in the core part prepared in Example 2 shown in FIG. It can be seen that the cycle characteristics of the battery including the improved.

< Experimental example 5> Comparison of discharge capacity

As shown in FIG. 9, the charge/discharge capacity of the battery containing the bulk Ni-Co-Al and the core-shell portion of Ni-Co-Al having the same composition as 85% of Ni content is different at 4.1V or more and 3.7V or less. can confirm. As a result, in the case of a battery containing Ni-Co-Al in the core-shell portion, phase shift is suppressed at a high voltage of 4.1 V or higher, and the average discharge voltage is increased at a low voltage of 3.7 V or less compared to a battery containing bulk Ni-Co-Al. Thus, it can be seen that the energy density is improved.

< Experimental example 6> Comparison of cycle characteristics

As shown in FIG. 10, when comparing the efficiency in 50 cycles of a battery containing bulk Ni-Co-Al and Ni-Co-Al of the same composition with a Ni content of 85%, Ni-Co of the core-shell portion It can be seen that the battery containing -Al has improved efficiency compared to the battery containing bulk Ni-Co-Al.

Claims (7)

A first step of preparing a precursor represented by the following Chemical Formula 1;
[Formula 1] Ni _b Co _c M _d (OH) ₂ (b≥0.8, c≤0.2, d≤0.2, and M is Al or Mn)
A second step of preparing a mixed dispersion while stirring by adding the precursor to a solution for forming a shell portion containing a compound represented by the following formula (2);
[Formula 2] Ni _b Co _c M _d (b≤0.1, c≤0.1, d≤0.3, M is Al or Mn)
A third step of drying the mixed dispersion to prepare particles having a shell portion coated 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° C.;
A sixth step of cleaning; And
A seventh step of performing a second heat treatment at a temperature of 700 to 850 °C; Method for producing a lithium composite oxide comprising a.
delete The method of claim 1,
The second step is a method of producing a lithium composite oxide, characterized in that rapid drying under reduced pressure conditions.
The method of claim 1,
In the first heat treatment step and the second heat treatment step, a method of producing a lithium composite oxide, characterized in that heat treatment is performed in an atmosphere containing 50% by volume or more of oxygen.
A lithium composite oxide manufactured by the manufacturing method of any one of claims 1, 3 and 4.
A cathode material for a non-aqueous electrolyte secondary battery comprising a lithium composite oxide prepared by the manufacturing method of any one of claims 1, 3 and 4.
A non-aqueous electrolyte secondary battery comprising a lithium composite oxide manufactured by the manufacturing method of any one of claims 1, 3 and 4.

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