KR102007565B1 - MANUFACTURING METHOD OF Li-Ni-Mn-O COMPOUNDS AS CATHOD MATERIAL FOR LITHIUM SECONDARY BATTERIES - Google Patents

Abstract

The present invention relates to a method for producing a lithium nickel manganese composite oxide for a lithium secondary battery. According to one embodiment of the invention, (a) mixing and synthesizing a plurality of metal precursors, and (b) cooling the synthesized composite by a quenching (quenching) process, wherein the composite is a spinel structure Provided is a method for producing a lithium nickel manganese composite oxide for a lithium secondary battery, including a lithium nickel manganese oxide and a lithium manganese oxide having a layered structure.

Description

Manufacturing method of lithium nickel manganese composite oxide for lithium secondary battery {MANUFACTURING METHOD OF Li-Ni-Mn-O COMPOUNDS AS CATHOD MATERIAL FOR LITHIUM SECONDARY BATTERIES}

The present invention relates to a method for producing a lithium nickel manganese composite oxide for a lithium secondary battery, and more particularly, the present invention is to increase the energy capacity of the positive electrode active material by dramatically increasing the electrochemical activity of the components constituting the composite A method for producing a lithium nickel manganese composite oxide for a battery.

In recent years, with the development of the electric, electronic, communication and computer industries, the development of eco-friendly vehicles and energy storage systems has rapidly progressed, and development of secondary batteries having high safety, high capacity, and low cost has become very important. Therefore, it is increasingly important to develop positive electrode materials that determine battery performance and determine overall cost.

Until now, most secondary battery markets use LiCoO ₂ (lithium cobalt oxide, LCO) based cathode active materials. However, this material contains expensive and toxic cobalt, and has a structurally layered structure, which is not suitable for electric vehicles because the structure collapses under high capacity and thus there is a problem in terms of safety. Therefore, much effort is being focused on the development of the anode material of a new material to replace this material.

Therefore, much research is being conducted on oxides composed of manganese and nickel, which are relatively inexpensive and have superior stability as cobalt as a material to replace the LCO-based cathode active material. In particular, much research is being conducted on spinel-structured lithium manganese composite oxides.

However, the lithium manganese oxide of the spinel structure has a disadvantage in that battery characteristics such as dissolution of Mn ions, which are transition metals, are degraded in the electrolyte when stored at a high temperature, thereby deteriorating battery characteristics. In addition, since the spinel structure has a smaller amount of lithium than the layered material, the capacity per unit weight is smaller than that of the conventional lithium cobalt composite oxide. Therefore, since there is a limit of capacity increase due to the spinel structure, the design of an electrode for improving the same must be parallel to enable mass use as a power source in fields such as electric vehicles.

A layered lithium-containing manganese / nickel oxide has been proposed to supplement the low capacity problem of lithium manganese oxide having such a spinel structure and to secure excellent thermal safety of the manganese-based active material. In particular, the layered Li ₂ MnO ₃ shows a very large capacity when overcharged at a high voltage, but has a disadvantage that the initial irreversible capacity is large. When the initial charge, activate the Li ₂ MnO ₃ as a positive electrode potential of lithium by i reference in order to enable at least 4.5V high voltage so that it contains no electrochemically activity Li ₂ MnO ₃ can be (activate). However, in this case, in order to prevent lithium precipitation from the negative electrode in the initial cycle according to the large irreversible capacity of Li ₂ MnO _3, the capacity of the negative electrode must be overdesigned, so that the actual reversible capacity may be reduced. In addition, some problems have been reported in safety.

As described above, there are disadvantages and limitations in the use of the positive electrode active materials of the conventional lithium secondary battery alone, and thus the use of the composites mixed between these materials is increasing. In particular, the lithium secondary battery has a high capacity to be used as a power source for medium and large equipment. In addition, the need for a lithium secondary battery having a high energy density by increasing the overall voltage distribution is increasing.

Korea Patent Publication No. 10-0694567 (2007.03.07)

The present invention is a composition change and structure of the components constituting the mixture through a new additional process to the spinel-layered cathode material mixture synthesized by the general solid-phase method described above, or by another process The present invention provides a method for manufacturing a lithium nickel manganese composite oxide for a lithium secondary battery that synthesizes lithium nickel manganese composite oxide (Li-Ni-Mn-O) having high capacity and high output characteristics by increasing electrochemical activity through change. .

According to one embodiment of the invention, (a) mixing and synthesizing a plurality of metal precursors, and (b) cooling the synthesized composite by a quenching (quenching) process, wherein the composite is a spinel structure Provided is a method for producing a lithium nickel manganese composite oxide for a lithium secondary battery, including a lithium nickel manganese oxide and a lithium manganese oxide having a layered structure.

In addition, the complex may be represented by the following formula (1) or (2).

[Formula 1]

Li _{1 + x} Ni _0.5-y Mn _1.5 O _4-z (where 0 <x <0.9 and 0 <y <0.4, 0 <z <3)

[Formula 2]

(1-x) LiNi _0.5 Mn _1.5 O ₄ + xLi ₂ MnO ₃ , where 0 <x <1.

In addition, the step (a), (a-1) mixing at least one metal precursor of lithium, nickel, manganese, transition metal, (a-2) primary synthesis of the mixed metal precursors, ( a-3) pulverizing the first synthesized composite to form a powder having a controlled particle size, and (a-4) secondly synthesizing the powder in an air atmosphere.

In addition, in the step (a-2), the precursor mixture may be calcined by at least one of a solid phase method, a coprecipitation method, an ion exchange synthesis method, and a sol-gel method.

In addition, in the step (a-3), the first synthesized composite may be ground using at least one method of a high energy ball mill, a high pressure water mill, an air jet mill, and a roller mill.

In addition, before step (a), the method may further include preparing a precursor of each of the spinel structure metal and the layered structure metal through a pretreatment process including a raw material mixing process, a drying process, and a pelletization process.

In addition, the mixing step of the raw material is a step of performing a homogeneous mixing of the solvent, the spinel structure metal precursor and the layered metal precursor using a ball mill, the drying step is a step of removing the solvent by heating the mixed precursor, The pelletization process may be a process of forming the mixed precursor into pellets of a predetermined form.

In addition, the composite cooled through the quenching process may have a weight percent (wt%) ratio of the layered metal oxide higher than the weight percent (wt%) ratio of the layered metal oxide set in accordance with the natural cooling process or the theoretical calculation. Can be.

In addition, the quenching process is to heat the complex in the furnace and then to take the complex out of the furnace and to cool it in the atmosphere. The natural cooling process is to heat the complex in the furnace and to cool the complex in the furnace. Can be.

According to the present invention, the energy capacity of a lithium-nickel-manganese composite oxide (with a spinel-layered structure) composite material formed and activated through a new process can be dramatically improved. At the same time, output performance can be improved. Therefore, the process developed in the present invention can provide a key process for forming a cathode material of a high capacity secondary battery, thereby improving energy capacity and output performance of various cathode active materials.

1 is a flowchart illustrating a method of manufacturing a lithium nickel manganese composite oxide for a lithium secondary battery according to an embodiment of the present invention.
Figure 2 shows the XRD pattern of the positive electrode material for a lithium secondary battery prepared by one embodiment of the present invention.
Figure 3 shows the XRD pattern of the powder obtained according to Example 3 of the present invention. .
Figure 4 shows the XRD pattern of the synthesis of 0.52 LiNi _0.5 Mn _1.5 O ₄ + 0.48 Li ₂ MnO ₃ prepared in Example 1 of the present invention by general natural cooling, and synthesized by quench cooling according to the present invention will be.
5 shows charge and discharge characteristics of 0.52 LiNi _0.5 Mn _1.5 O ₄ + 0.48 Li ₂ MnO ₃ prepared according to Example 1 of the present invention by general natural cooling, and the synthesis by quench cooling according to the present invention. The evaluation results are shown.
6 shows the XRD pattern of the spinel structure oxide.
7 and 8 show the EDS mapping of the spinel structure's oxide in natural cooling.
9 and 10 show the EDS mapping of the spinel structure oxide in the quenching process.

Hereinafter, the present invention will be described in more detail based on the preferred embodiments of the present invention. However, the following examples are merely examples to help the understanding of the present invention, whereby the scope of the present invention is not reduced or limited.

The present invention provides a method for synthesizing a mixed cathode active material comprising a spinel structure lithium nickel manganese oxide having a high operating voltage and excellent output characteristics and a lithium nickel manganese compound having a layered structure capable of expressing a large capacity when overcharged at a high voltage. It is about a new process to dramatically increase the electrochemical activity of a composite. Through this new process method, spinel structure lithium nickel manganese oxide can be used to improve the charge / discharge rate, which is an important electrochemical property, and lithium manganese oxide (Li ₂ MnO ₃ ) with layered structure can be used to secure the capacity. This could lead to new ways to dramatically improve the energy capacity of the anode material as a whole.

The present application proposes a method for synthesizing a mixture having a known spinel-layered structure but not the same composition or structure by adjusting the composition of lithium-nickel-manganese, and increasing electrochemical activity. In the following, the present invention will be described in more detail based on the preferred embodiments of the present invention. However, the following examples are merely examples to help the understanding of the present invention, whereby the scope of the present invention is not reduced or limited.

The present invention provides a method for synthesizing a mixed cathode active material comprising a spinel structure lithium nickel manganese oxide having a high operating voltage and excellent output characteristics and a lithium nickel manganese compound having a layered structure capable of expressing a large capacity when overcharged at a high voltage. It is about a new process to dramatically increase the electrochemical activity of a composite. Through this new process method, spinel structure lithium nickel manganese oxide can be used to improve the charge / discharge rate, which is an important electrochemical property, and lithium manganese oxide (Li ₂ MnO ₃ ) with layered structure can be used to secure the capacity. This could lead to new ways to dramatically improve the energy capacity of the anode material as a whole.

The present application proposes a method for synthesizing a mixture having a known spinel-layered structure but not the same composition or structure by adjusting the composition of lithium-nickel-manganese, and increasing electrochemical activity. For this purpose, an additional heat treatment method is proposed. Through this additional heat treatment, it can be seen that elements such as lithium, nickel and manganese are inter-diffusion between components. This additional heat treatment process results in a change in the structure of each component and an increase in electrochemical activity. A spinel-layered cathode mixture is not subjected to a new additional process. It is possible to synthesize a cathode active material for a secondary battery having a higher capacity and a higher power performance than a typical mixture.

In addition, in the present invention, in order to synthesize the composite of the spinel-layered structure, the solid phase method was used, but the co-precipitation method, the ion exchange reaction under hydrothermal condition, the ultrasonic spray pyrolysis method The composite synthesized in) may also improve the electrochemical performance when the process developed in the patent is applied. In the present invention, the overall performance can be improved by applying the developed post-treatment process regardless of the method of making the composite.

Accordingly, in the present invention, a spinel-layered lithium nickel manganese composite oxide (Li-Ni-) in which a conventional spinel-layered cathode material mixture is improved in output characteristics compared to the prior art through a new additional process. The preparation method of Mn-O) is shown.

Specifically, in the present invention, by adjusting the composition of the manganese, lithium, nickel of the known lithium nickel manganese composite oxide (LiNi _0.5 Mn _1.5 O ₄ ) of the spinel structure (Spinel) by synthesizing in a solid-phase method to spinel ( spinel) LiMn ₂ O ₄ , LiNi _0.5 Mn _1.5 O ₄ It is in the form of a composite containing a layered structure of Li ₂ MnO ₃ or spinel (Spinnel structure) LiMn ₂ O ₄ is included Without a spinel structure of LiNi _0.5 Mn _1.5 O ₄ and a layered structure of Li ₂ MnO ₃ or the two phases are synthesized separately and mechanically mixed according to the composition A method for obtaining a cathode material for a lithium secondary battery characterized by a composite and improving the electrochemical activity and power characteristics of a phase constituting the synthesized composite through an additional new process is described. present.

In general, the spinel structure oxide is capable of fast diffusion of lithium ions due to the characteristics of the three-dimensional crystal structure shows excellent output characteristics compared to the cathode material of the layer structure structure. However, when used alone, there are capacitive limitations due to the structural characteristics of the spinel, and there is a shortfall in order to finally increase the energy density. In addition, the spinel structure lithium nickel manganese oxide (LiNi _0.5 Mn _1.5 O ₄ ) has two operating voltages, which are largely divided into 4.7 V and 2.7 V. When used alone, the oxidation source reaction occurs in the region between the operating voltages of the two regions. Since there is no redox voltage, a sudden voltage drop occurs.

This improves the capacitive limit of spinel structure lithium nickel manganese oxide (LiNi _0.5 Mn _1.5 O ₄ ) and has a layered structure with redox voltage between 4V and 3V without sudden voltage drop. Through the development of a cathode active material constituting a composite (material) and a composite (material), the research to significantly improve the energy capacity of the cathode material.

In the present invention, spinel structure lithium manganese oxide (LiMn ₂ O ₄ ), spinel structure lithium by adjusting the composition of manganese, lithium, nickel in the known spinel structure lithium nickel manganese oxide (LiNi _0.5 Mn _1.5 O ₄ ) according to the stoichiometric ratio It is a composite material composed of nickel manganese oxide (LiNi _0.5 Mn _1.5 O ₄ ) and layered lithium manganese oxide (Li ₂ MnO ₃ ), or it does not contain spinel structure lithium manganese oxide (LiMn ₂ O ₄ ). Spinel-structured nickel manganese oxide (LiNi _0.5 Mn _1.5 O ₄ ) and layered structured lithium manganese oxide (Li ₂ MnO ₃ ) make up a total of two phase composite materials, A simple and mass-producible way to achieve high power characteristics can be proposed.

The cathode material for a lithium secondary battery according to the present invention synthesizes a spinel-layered composite through a solid phase reaction, and then spinels during quenching through a new additional process. Without forming a rock-salt phase, the spinel-layered layer increases the amount of the layered layer and increases the electrochemical activity and improves the output characteristics. ) Composite can be obtained.

In this case, the spinel-layered composite of the spinel-layered lithium nickel manganese oxide (LiNi _0.5 Mn _1.5 O ₄ ) and the layered structure are required for the effect of the new additional process. Lithium manganese oxide (Li ₂ MnO ₃ ) should be included in the case of phase with the amount of spinel and layered by adjusting the amount of lithium and nickel in the composition represented by the following [Formula 1]. I can regulate it.

[Formula 1]

Li _{1 + x} Ni _0.5-y Mn _1.5 O _4-z (where 0 <x <0.9 and 0 <y <0.4, z> 0)

When controlling the amount of lithium and nickel in the spinel phase lithium nickel manganese oxide (LiNi _0.5 Mn _1.5 O ₄ ), the spinel phase contains lithium manganese oxide (LiMn ₂ O ₄ ). The process proposed in the present invention is a composition containing a spinel structure of lithium nickel manganese oxide (LiNi _0.5 Mn _1.5 O ₄ ) and a layered structure of lithium manganese oxide (Li ₂ MnO ₃ ). The effects such as changes in electrochemical activity obtained through this can be obtained. Therefore, as shown in [Formula 2], a spinel structure may be represented by a composition including lithium nickel manganese oxide (LiNi _0.5 Mn _1.5 O ₄ ) and a layered structure lithium manganese oxide (Li ₂ MnO ₃ ).

[Formula 2]

(1-x) LiNi _0.5 Mn _1.5 O ₄ + xLi ₂ MnO ₃ , where 0 <x <1.

In addition, the spinel structure of lithium nickel manganese oxide (LiNi _0.5 Mn _1.5 O ₄ ) and the layered structure of lithium manganese oxide (Li ₂ MnO ₃ ) separately synthesized after mechanical mixing Similar effects are achieved with new additional processes.

1 is a flowchart illustrating a method of manufacturing a lithium nickel manganese composite oxide for a lithium secondary battery according to an embodiment of the present invention.

Referring to FIG. 1, in the method of manufacturing a lithium nickel manganese composite oxide for a rechargeable lithium battery according to an embodiment of the present invention, a step of mixing a lithium precursor, a manganese precursor, and a transition metal precursor (S100), and inserting the mixture into a heating furnace The first step of synthesizing in an air atmosphere (S200), the step of naturally cooling the material formed by the first synthesis and then grinding through a high energy ball mill (high energy ball mill) (S300), the pulverized material in the heating furnace And a step (S500) of secondary synthesis in an air atmosphere (S400) and a rapid cooling of the secondary synthesized composite through a quenching process (S500), represented by the formula (1) or (2) The cathode material for secondary batteries can be manufactured.

Before step S100, each metal precursor may be prepared through a pretreatment process including a mixing process of a raw material, a drying process, and a pelletization process.

Specifically, the mixing step of the raw material may be mixed by using a ball mill after each metal precursor is added to the acetone solvent. Here, the ball mill may be performed for about 6 to 24 hours.

If the ball mill is performed for less than 6 hours, it is not sufficient to dissolve, pulverize or mix the injected precursor, and if the ball mill is performed for more than 24 hours, the mixing effect may be saturated, which may be economically disadvantageous due to the extension of the process time. have.

In the present invention, a solvent such as acetone or water is used as the solvent, but any material may be used without limitation as long as the material is properly mixed with the precursor and does not affect subsequent processes. In addition, if the prepared precursor can produce a uniform mixture without performing ball milling, the precursor may be prepared through a simple stirring process.

In the drying step of the pretreatment step, the mixed precursor may be heated to a predetermined temperature to remove the solvent. In this drying process, the mixture containing the solvent is heated to less than about 100 ° C. using equipment such as a hot plate. At this time, when heated above about 100 ℃, the precursor may react to form another phase.

In addition, the pelletization process of the pretreatment process is to facilitate the synthesis of the gas component that is decomposed in the subsequent process to facilitate the synthesis, it is possible to make a pellet having an average diameter of 1cm using a pelletizing device. However, the diameter of the pellet in the pelletization step is not particularly limited.

In step S100, the proportion of each metal precursor is increased without increasing the amount of manganese, and the amount of lithium is increased, and thus the precursor is mixed uniformly using acetone solvent at room temperature according to the stoichiometric ratio. Can be performed. Here, the lithium precursor may include Li ₂ CO ₃ , LiNO ₃ , and the like. Each such metal precursor may provide a metal component to the composition of Formula 1 or Formula 2. In addition, the manganese precursor and the nickel precursor may include a material capable of synthesizing the material by heating.

In addition, as the addition ratio of the nickel precursor to the lithium precursor of the compound of Formula 1 increases, the spinel phase increases, and as the x value decreases in the composition of the compound of Formula 2, the spinel phase may increase.

In step S200, only the metal component is removed from the mixture by removing carbonates and nitrates attached to metal oxides, metal nitrides and metal oxynitrides, which are metal precursors, through the first synthesis process at about 800 ° C to about 900 ° C as heating conditions for the solid phase reaction. To form an image.

In step S300, mechanical grinding may be performed through a high energy ball mill. Mechanical pulverization in step S300 may make the reaction that goes from the initial high voltage charge process to the electrochemically activated (Li ₂ MnO ₃₎ material of the layer structure can be made better. In other words, mechanical grinding can further increase the activated reaction.

Here, the grinding of the mixture can take place for about 2 to 3 hours, but other chemical or physical processes that can reduce the particle size of the powder, such as high-pressure water milling, air-jet mills. It may also be made through a roller mill, or the like.

In step S400, annealing may be performed at a temperature of about 700 ° C. or more, which is a temperature at which Ni solubility on the spinel falls, in order to obtain an effect of promoting interaction between components of the composite through a heat treatment process. Can be. In this case, when the annealing time is too long, the size of the particles may increase, so that initial activation of Li ₂ MnO ₃ , which is a layered structure, may not occur. Therefore, annealing is suitably carried out for about 1 to 10 hours.

In step S500, quenching may be performed to rapidly cool after annealing.

Here, quenching is such that the interaction between the spinel-like Ni solubility and the layered electrochemical activity between the spinel-like material and the layered material is maintained at about 700 ° C. or higher. The cooling rate must be made fast.

If cooling slowly, the Ni solubility of the spinel is changed again, and at the same time, the electrochemical activity of the layered material is also changed, thereby creating a general spinel structure-layered structure in which the output characteristics are not improved.

Accordingly, the quenching process is a process of annealing to maintain the structure or composition of the mixture at a high temperature, so a quenching method capable of retaining the phase may also be used, and is not limited by the difference in the synthesis method.

On the other hand, the method for manufacturing a lithium nickel manganese composite oxide for a lithium secondary battery according to another embodiment of the present invention in order to obtain Li ₂ MnO ₃ of the layer structure and LiNi _0.5 Mn _1.5 O ₄ of the spinel structure separately, lithium precursor, manganese precursor, transition Mixing the metal precursor (S100), putting the mixture into a heating furnace and first synthesizing in an air atmosphere (S200), and a layer structure obtained by naturally cooling the material obtained through the first synthesis, Li ₂ MnO. ₃ and a spinel structure of LiNi _0.5 Mn _1.5 O ₄ mixed and pulverized through a high energy ball mill (S300), the pulverized material is put into a heating furnace and secondary synthesis in an air atmosphere (S400), and? It includes a step (S500) for rapidly cooling the secondary synthesized material through the description, it can be prepared a cathode material for a lithium secondary battery represented by the formula (1) and (2).

Here, duplicate description of the same method as the manufacturing method of the lithium nickel manganese composite oxide for lithium secondary batteries according to an embodiment of the present invention will be omitted.

According to another embodiment of the present invention, a high energy ball mill, which is a new additional process when a layered structure of Li ₂ MnO ₃ and a spinel structure of LiNi _0.5 Mn _1.5 O ₄ is present as a composite After a high energy ball mill, heat treatment is performed at about 700 ° C. or more, and a spinel-layered composite having improved output characteristics through quenching is manufactured.

According to another embodiment of the present invention, the initial charge activated process of the layered material is well performed through a high energy ball mill, and then heat treated at 700 ° C. or higher. Quenching is a rapid cooling process. In this process, the spinel structure generally does not form a rock-salt phase due to poor Ni solubility, and at the same time a layered structure. It is possible to prepare a spinel-layered composite having an increased output characteristic and an increase in the amount of material and electrochemical activity.

The cathode material manufactured by the above embodiments may be used in a cathode for a lithium secondary battery and a lithium secondary battery including the cathode.

The following presents specific embodiments of the present invention. However, the embodiments described below are merely for illustrating or explaining the present invention in detail, and thus the present invention should not be limited thereto.

Example 1

In Example 1 of the present invention (x) in the formula (2) was selected as 0.52 (1-x) LiNi _0.5 Mn _1.5 O ₄ + x Li ₂ MnO ₃ by the method shown in FIG.

First, precursors for the solid phase reaction include Li ₂ CO ₃ (Semisei, purity over 99%), NiCO ₃ , (alpha Aisa, purity above 99%), MnO ₂ (alpha Aisa, purity above 99.9%) It was prepared as follows.

0.75 Li ₂ CO ₃ + 0.24 NiCO ₃ + 1.26 MnO ₂

Specifically, the weight of each prepared material is 2.26 g of Li ₂ CO ₃ , 1 g of NiCO ₃ , 3.84 g of MnO ₂ ,

The wt% of LiNi _0.5 Mn _1.5 O ₄ was 52%, and the wt% of Li ₂ MnO ₃ was mixed at a ratio of 48%.

The precursor thus prepared was added to an acetone solvent and ball milling was performed for about 12 hours to prepare a mixture in which the aggregated powder in the precursor was disintegrated and uniformly mixed. Zirconia balls 3.5 mm in diameter and 10 mm were used for ball milling.

After mixing the powder via ball milling, the mixture was dried to a temperature below 100 ° C. in air using a hot plate, and the dried mixture was pelleted using a disc mold.

The pellets thus prepared are charged into an alumina crucible, calcined at 900 ° C. in an air atmosphere, and then ground through a high energy ball mill for about 2 hours and 20 minutes. In the ball milling, a zirconia ball having a diameter of 1 mm was used.

After grinding the powder through ball milling, the mixture was dried to a temperature below 100 ° C. in the air using a hot plate, and the dried mixture was pelleted using a disc mold.

After that, re-annealing was performed at 800 ° C. for about 5 hours. At this time, the heating rate is 4 ℃ / minute and immediately after the heating is quenched (quenching) process to remove rapidly from the furnace in the atmosphere.

The powder obtained through the above method was analyzed using XRD, and FIG. 2 shows the result.

As confirmed in FIG. 2, the powder obtained according to Example 1 of the present invention showed a 0.52 Li ₂ MnO ₃ 0.48 LiNi _0.5 Mn _1.5 O ₄ XRD pattern, which was a layered-spinel composite. . In this case, it can be seen that most peaks of the two phases overlap, and there may be some errors.

Example 2

In Example 2 of the present invention, Li _{1 + x} Ni _0.5-y Mn _1.5 O ₄ was synthesized by the method shown in FIG. 1 by selecting x as 0.2 and y as 0.1 in Chemical Formula 1.

First, precursors for the solid phase reaction include Li ₂ CO ₃ (Semisei, purity over 99%), NiCO ₃ , (alpha Aisa, purity above 99%), MnO ₂ (alpha Aisa, purity above 99.9%) It was prepared as follows.

0.6 Li ₂ CO ₃ + 0.4 NiCO ₃ + 1.5 MnO ₂

Specifically, the weight of each prepared material is 0.93 g of Li ₂ CO ₃ , 1 g of NiCO ₃ , 2.76 g of MnO ₂ , that is, in general LiNi _0.5 Mn _1.5 O ₄ , the amount of Mn is not changed, and the amount of Li is further increased by 20%. The amount of Ni was further reduced by 20% and mixed with Li _1.1 Ni _0.45 Mn _1.5 O _{4 according} to the stoichiometric ratio. Subsequent synthesis processes were carried out in the same manner as in Example 1 to synthesize Li _1.5 Ni _0.25 Mn _1.5 O ₄ . That is, the synthesis was carried out in the same manner as in Example 1 except that the amount of lithium increased and the amount of nickel reduced was increased five times compared to Example 1.

 Example 3

In Example 3 of the present invention, Li _{1 + x} Ni _0.5-y Mn _1.5 O ₄ was synthesized by the method shown in FIG. 1 by selecting x as 0.5 and y as 0.25 in [Formula 2].

First, precursors for the solid phase reaction include Li ₂ CO ₃ (Semisei, purity over 99%), NiCO ₃ , (alpha Aisa, purity above 99%), MnO ₂ (alpha Aisa, purity above 99.9%) It was prepared as follows.

0.75 Li ₂ CO ₃ + 0.25 NiCO ₃ + 1.5 MnO ₂

Specifically, the weight of each prepared material is 1.87 g of Li ₂ CO ₃ , 1 g of NiCO ₃ , 4.42 g of MnO ₂ , that is, in general LiNi _0.5 Mn _1.5 O ₄ , without changing the amount of Mn, increasing the amount of Li by 50% The amount of Ni was further reduced by 50% and mixed with Li _1.5 Ni _0.25 Mn _1.5 O _{4 according} to the stoichiometric ratio. Subsequent synthesis processes were carried out in the same manner as in Example 1 to synthesize Li _1.5 Ni _0.25 Mn _1.5 O ₄ . That is, the synthesis was carried out in the same manner as in Example 1 except that the amount of lithium increased and the amount of nickel reduced was increased five times compared to Example 1.

The powder obtained according to Example 3 of the present invention is 0.32 Li ₂ MnO ₃ 0.68 LiNi _0.5 Mn _1.5 O ₄ , which is a layered-spinel composite, and FIG. XRD pattern of the powder obtained according to the present. In this case, it can be seen that most peaks of the two phases overlap, and there may be some errors.

[XRD Pattern Comparison]

Figure 4 shows the XRD pattern of the synthesis of 0.52 LiNi _0.5 Mn _1.5 O ₄ + 0.48 Li ₂ MnO ₃ prepared in Example 1 of the present invention by general natural cooling, and synthesized by quench cooling according to the present invention will be.

As shown in FIG. 4, the synthetically synthesized by quenching cooling (red solid line 300), compared to the one synthesized by general natural cooling (blue solid line 200), is a composition of the same spinel-layered composite. The difference in the intensity of the peaks of the spinel and the layered structure is significantly different, which may mean that the weight ratio of the layered material and the material of the spinel structure constituting the material is different.

[Charge / Discharge Characteristics Evaluation Results]

5 shows charge and discharge characteristics of 0.52 LiNi _0.5 Mn _1.5 O ₄ + 0.48 Li ₂ MnO ₃ prepared according to Example 1 of the present invention by general natural cooling, and the synthesis by quench cooling according to the present invention. The evaluation results are shown. All proceeded identically at the C / 20 rate in the first cycle.

In order to evaluate the electrochemical behavior, the electrode was made with a 0.52 LiNi _0.5 Mn _1.5 O ₄ + 0.48 Li ₂ MnO ₃ material prepared according to Example 1 of the present invention and subjected to an electrochemical test. Electrode is made of 0.52 LiNi _0.5 Mn _1.5 O ₄ + 0.48 Li ₂ MnO ₃ as active material, 7.5 wt% super P with carbon powder, 7.5 wt% carbon nanofiber (CNF), and 5 wt% PVDF with binder. The mixture was mixed well for 20 to 30 minutes, stirred for about 2 hours, and applied well to Al foil, followed by drying for 12 hours in a vacuum chamber. It was then stamped with an 8mm punch to make 1 to 3 mg of anode, which was done in a glove box (argon atmosphere). The cell was assembled using the positive electrode prepared as described above. When the cell was assembled, the separator was used to cut Celgard 2400 into about 13 mm, and the electrolyte used was 1M LiPF ₆ as a solution containing 1: 1 weight of ethylene carbonate / dimethyl carbonate. As the negative electrode, lithium metal was used. The electrochemical behavior of the cells thus prepared was measured at room temperature. The instrument used the maccor series 4000, and the measurement began with charging from 2V to 5V, and the current was charged and discharged at the C / 12 rate and 25mA / g in the first cycle, and then charged and discharged. 1C rate, 300mA / g size was added to measure.

In general, the solubility in spinel-layered composites, particularly in the case of spinel materials, in the case of spinel materials, is greatly reduced as the temperature is about 700 ° C. or more, in the case of Ni, in particular in the case of Ni. As a result, the synthesis of these spinel-layered complexes at or above about 700 ° C. usually produces many unwanted rock-salt phases (new phases formed by decreasing solubility of the element). In this case, the rock-salt phase may affect the capacity reduction of the lithium secondary battery because it is electrochemically inactive. However, if the spinel-layered composite is subjected to a quenching process according to an embodiment of the present invention, the element escaped by the lower solubility in the spinel material may be easily bonded to the layered structure without forming a dark salt phase.

In addition, the electrochemical activity of the layered material can be greatly increased when the element is bonded to the layered structure. This can be proved that when the XRD refinement is performed, the lattice parameter is greatly increased and a new type of layer is formed.

In addition, the increase in the electrochemical properties of the layered material is due to the fact that the elements of the spinel material are bonded to the layered structure, which greatly affects the size of the diffusion channel of lithium ions. This can also be seen through the change of lattice constant.

That is, the quenching process according to one embodiment of the present invention can eliminate unnecessary phases that may occur during the synthesis process in the spinel and at the same time increase the electrochemical activity of the layered material by combining the spinel element with the layered material. Can be.

5 is synthesized by general natural cooling of 0.52 LiNi _0.5 Mn _1.5 O ₄ + 0.48 Li ₂ MnO ₃ prepared according to Example 1 of the present invention (blue solid line 400), and quench cooling according to the present invention It shows the result of evaluating the charge-discharge characteristics of the synthesized (solid red line 500).

Referring to FIG. 5, the weight% of the materials of the two structures are different according to the synthesis method as shown in FIG. 4, which may mean that many materials of the layered structure having increased activation degree are generated in the newly presented process. In particular, it can be seen that the difference in capacity in the redox potential at which the layered material reacts from about 4.0 V to about 2.8 V based on the discharge graph is apparent.

Meanwhile, as a result of comparison through XRD refinement, in the sample to which the quenching process according to an embodiment of the present invention is applied, the percentage by weight (wt%) of the layered metal oxide is natural cooling. It may be configured to be higher than the weight percent (wt%) ratio of the layered metal oxide set in accordance with the process or theoretical calculation.

At this time, the quenching process is to heat the composite in the furnace and then take the composite out of the furnace and cool it in the air. The natural cooling process is to heat the composite in the furnace and then to cool the composite in the furnace.

For example, a sample subjected to a quenching process has a weight percent (wt%) ratio of the layered structure and the spinel structured material to about 55:45, while a sample to which the natural cooling process is applied has a layered structure. It can be seen that the ratio of the weight percent (wt%) and the spinel material is similar to 40:60, the weight percent (wt%) calculated as about 40:60.

Here, when the proportion of the weight percent (wt%) of the layered material in the sample subjected to the quenching process has a value that is equal to or lower than the calculated composition of the layered / spinel, the layered structure is the solubility of Ni in the spinel. Due to the weight percent (wt%) is not increased, in this case, because it is a layered structure that does not contain Ni, the electrochemical activity is lowered, the storage capacity is reduced, and the form of the voltage is different energy There may be a problem that the density is low.

This percentage difference in weight percent (wt%) is formed as the structure stabilizes and the temperature difference occurs. In particular, in the case of quenching, the structure is in a high temperature state and in the case of natural cooling, Because it forms. This difference in temperature is particularly related to the solubility limit of the spinel-structured material, and at high temperatures, especially at low temperatures, the solubility of Ni is generally well formed. It can be seen that the weight ratio is changed while Ni is included in the layered structure due to low solubility.

In other words, if the spinel structure contains Ni through a quenching process, the layered structure has a high weight percent (wt%), which is generally known to have good electrochemical activity, and at the same time, low solubility Ni forms a rock salt phase. Because it does not. For these two reasons it can have a high electrochemical activity.

This will be described further with reference to FIGS. 6 to 10.

6 shows the XRD pattern of the spinel structure oxide, and it can be seen that NiO disappears while maintaining about 800 ° C., and at the same time, the pattern peak intensity ratio of Li ₂ MnO ₃ is increased. This results in a decrease in the solubility of Ni on the LNMO at high temperature to form NiO, but it can be predicted that NiO disappears and Ni is included in Li ₂ MnO ₃ while the temperature is maintained. At the same time, as the temperature is lowered to room temperature, the solubility of Ni increases again, the pattern peak intensity of the LNMO phase increases, and the pattern peak intensity of Li ₂ MnO ₃ decreases. In addition, it can be seen that the phase of Li ₂ MnO ₃ containing Ni disappears as the temperature drops.

7 and 8 show the EDS mapping of the spinel structure's oxide in natural cooling. 9 and 10 show the EDS mapping of the spinel structure oxide in the quenching process.

7 to 10, when comparing the ratio of Ni / Mn through the EDS mapping it can be seen that the ratio of Ni / Mn in the case of natural cooling is relatively non-uniform compared to the quenching process. That is, in the case of the sample according to the quenching process, it can be seen that Ni is uniformized while being included in Li ₂ MnO ₃ having only Mn at a high temperature.

Although the technical spirit of the present invention has been described above with reference to the accompanying drawings, the present invention has been described by way of example and is not intended to limit the present invention. In addition, it is obvious that any person skilled in the art may make various modifications and imitations without departing from the scope of the technical idea of the present invention.

Claims (9)

(a) preparing a composite of a lithium nickel manganese oxide having a spinel structure and a lithium manganese oxide having a layered structure,
(b) milling the composite to reduce particle size and
(c) heating the composite to a temperature of 700 to 900 ° C., followed by cooling by a quenching process,
The composite in which step (c) is performed is a lithium nickel manganese composite oxide for lithium secondary batteries in which at least a part of the nickel component included in the lithium nickel manganese oxide having the spinel structure is bonded to the lithium manganese oxide having the layered structure. Manufacturing method.
The method of claim 1,
The composite is a method for producing a lithium nickel manganese composite oxide for a lithium secondary battery, represented by the following [Formula 1] or [Formula 2].
[Formula 1]
Li _{1 + x} Ni _0.5-y Mn _1.5 O _4-z (where 0 <x <0.9 and 0 <y <0.4, 0 <z <3)
[Formula 2]
(1-x) LiNi _0.5 Mn _1.5 O ₄ + xLi ₂ MnO ₃ , where 0 <x <1.
The method of claim 1,
In step (a),
(a-1) mixing at least one metal precursor among lithium, nickel, manganese and transition metals, and
(a-2) A method for producing a lithium nickel manganese composite oxide for a lithium secondary battery, comprising the step of primary synthesis of the mixed metal precursors.
The method of claim 3,
In the step (a-2), a lithium nickel manganese composite oxide for a lithium secondary battery, which synthesizes the precursor mixture by at least one of a solid phase method, a coprecipitation method, an ion exchange synthesis method, and a sol-gel method. Manufacturing method.
The method of claim 3,
In the step (b), to prepare a lithium nickel manganese composite oxide for a lithium secondary battery, grinding the primary synthesized composite using at least one method of a high energy ball mill, high pressure water mill, air jet mill, and roller mill Way.
The method of claim 1,
Before the step (a), further comprising preparing a precursor of each of the spinel structure metal and the layered structure metal through a pretreatment process including a raw material mixing process, drying process and pelletization process, lithium nickel for lithium secondary battery Method for producing manganese composite oxide.
The method of claim 6,
The mixing step of the raw material is a step of performing a uniform mixing of the solvent, the spinel structure metal precursor and the layered metal precursor using a ball mill,
The drying step is a step of removing the solvent by heating the mixed precursor,
The pelletizing process is a process for forming a mixed precursor into a pellet of a predetermined form, a method for producing a lithium nickel manganese composite oxide for a lithium secondary battery.
The method of claim 1,
The composite cooled through the quenching process is characterized in that the weight percent (wt%) ratio of the layered metal oxide is higher than the weight percent (wt%) ratio of the layered metal oxide set in accordance with the natural cooling process or theoretical calculation. Method for producing a lithium nickel manganese composite oxide for a secondary battery.
The method of claim 8,
The quenching process is to heat the composite in the furnace and then to take the composite out of the furnace and cool it in the air.
The natural cooling process is a method for producing a lithium nickel manganese composite oxide for a lithium secondary battery, which is to cool the composite in the furnace after heating the composite in the furnace.

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