KR20150076402A - Positive electrode active material for rechargable lithium battery, method for synthesis the same, and rechargable lithium battery including the same - Google Patents

Abstract

The present invention relates to a cathode active material including the lithium manganese oxide doped with phosphorous (P) ions for a lithium secondary battery, a preparation method thereof, and the lithium secondary battery including the same.

Description

TECHNICAL FIELD [0001] The present invention relates to a positive electrode active material for a lithium secondary battery, a method for producing the same, and a lithium secondary battery including the same. BACKGROUND OF THE INVENTION [0002]

A cathode active material for a lithium secondary battery, a production method thereof, and a lithium secondary battery comprising the same.

A battery is a device that converts the chemical energy generated by an electrochemical oxidation-reduction reaction of an internal chemical substance into electrical energy. When the energy inside the battery is exhausted, the primary battery and the rechargeable secondary battery . Among them, the secondary battery can be used by charging and discharging several times by using reversible conversion between chemical energy and electric energy.

Background Art [0002] With the recent development of high-tech electronic industry, it is possible to miniaturize and lighten electronic equipments, and the use of portable electronic equipments is increasing. The need for a battery having a high energy density as a power source for such portable electronic devices has been increased, and research on lithium secondary batteries has been actively conducted.

Such a lithium secondary battery includes a positive electrode including a positive electrode active material capable of intercalating and deintercalating lithium and a negative electrode including a negative active material capable of intercalating and deintercalating lithium And the electrolyte is injected into the battery cell.

Among them, studies have been made to improve the battery characteristics by using an oxide containing various transition metals as a cathode active material. Examples of the oxide containing a transition metal include lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide and the like.

Lithium manganese oxide (LiMn ₂ O ₄ , LMO) has a spinel structure and has a large amount of Mn, which is cheaper than other materials (LiCoO ₂ , LiNiO ₂ ) This is environmentally friendly and safe. Also, because of its high energy density and excellent output characteristics, it is used in battery automobiles and various portable power sources. However, in order to be used as a stable power source for energy storage devices and battery automobiles in the future, problems of electrolyte decomposition at a high temperature and capacity reduction due to Mn dissolution must be solved.

During the charging and discharging of lithium manganese oxide, manganese ions (Mn ^{3 +} ) are divided into Mn ^{2 + / 4 +} ions by disproportionation and Mn ^{2 +} ions dissolve as electrolytes and move to the cathode And Mn ^{2 +} ions precipitate on the surface of the negative electrode and act as a resistor. This causes a reduction in capacity of the lithium manganese oxide. The Mn elution proceeds actively at a higher temperature (about 55 ° C) than at room temperature, resulting in a rapid capacity decrease.

Many studies have been carried out to solve this capacity reduction problem. Typically, there are cathode coating and cation doping.

The surface coating of the cathode material is a metal oxide such as Al ₂ O ₃ , ZrO ₂ , ZnO, and Co ₃ O ₄ to coat the particles of lithium manganese oxide, thereby suppressing the side reaction with the electrolyte through decomposition of the electrolyte and formation of a film. Cation doping also stabilizes the crystal structure by doping transition metal ions such as Al, Fe, Co, Ni, and Cr.

However, existing surface coatings and cation doping have limitations in solving capacity reduction problems at high temperatures.

A lithium secondary battery including the same, a method for producing the same, and a lithium secondary battery including the same.

In one embodiment of the present invention, there is provided a cathode active material for a lithium secondary battery comprising a lithium manganese oxide doped with phosphorus (P) based anions.

The phosphorus anion may be PO ₄ ^{3 -} .

The lithium manganese oxide doped with phosphorus anions may be further doped with aluminum.

The lithium manganese oxide doped with the phosphorus-based anion may be represented by the following formula (1).

[Chemical Formula 1]

Li _x Mn _{2 - y} Al _y O _{4 -z} (PO ₄ ) _z

In the above formula (1), 0.9? X? 1.5, 0? Y? 0.1, and 0.001? Z?

0.003? Z? 0.007 in the above formula (1).

In Formula 1, 0.05? Y? 0.1 may be satisfied.

The lattice constant of the lithium manganese oxide doped with the phosphorus anion may be 8.2085 to 8.2300.

The cathode active material may be in the form of secondary particles in which primary particles are aggregated, and the average particle diameter of the secondary particles may be 8 to 30 탆. Further, the average particle diameter of the primary particles may be 0.1 탆 to 5 탆.

The content of phosphorus (P) measured by inductively coupled plasma (ICP) analysis in the cathode active material may be 0.01 ppm to 0.5 ppm.

The cathode active material may be spherical.

According to another embodiment of the present invention, there is provided a method for producing a metal salt, comprising: preparing an aqueous metal salt solution containing a lithium source, a manganese source, and a phosphorus source; Pulverizing the aqueous metal salt solution; Spray-drying the pulverized metal salt aqueous solution to prepare a metal oxide precursor; Heat treating the metal oxide precursor; And a step of obtaining a lithium manganese oxide doped with a phosphorus-based anion.

The phosphorus source may be NH ₄ H ₂ PO ₄ , C ₆ H ₁₈ O ₈ P ₂ , C ₄ H ₁₁ O ₄ P, C ₆ H ₁₃ O ₉ P, AlPO ₄ , or a combination thereof.

The phosphorus raw material may be contained in an amount of 0.001 to 0.02 mol based on 1 mol of the lithium source.

The aqueous metal salt solution may further comprise an aluminum raw material.

The concentration of the aluminum raw material in the metal salt aqueous solution may be 0.01M to 0.1M.

The step of pulverizing the metal salt aqueous solution may be such that the raw materials are pulverized to have a particle size of 1 μm or less.

The step of heat-treating the metal oxide precursor may be performed at 850 캜 to 950 캜.

The average particle diameter of the metal oxide precursor may be 8 탆 to 30 탆.

The phosphorus-doped anion-doped lithium manganese oxide may be represented by the following formula (1).

[Chemical Formula 1]

Li _x Mn _{2 - y} Al _y O _{4 -z} (PO ₄ ) _z

In the above formula (1), 0.9? X? 1.5, 0? Y? 0.1, and 0.001? Z?

According to another embodiment of the present invention, there is provided a lithium secondary battery including the positive electrode, the negative electrode, and the electrolyte containing the positive electrode active material.

Other details of the embodiments of the present invention are included in the following detailed description.

The cathode active material according to one embodiment and the lithium secondary battery including the same have excellent high-temperature lifetime characteristics and output characteristics.

1 shows the results of XRD analysis of the cathode active materials of Comparative Example 1 and Examples 1 to 5.
2 is a scanning electron microscope (SEM) photograph of the cathode active material of Comparative Example 1 and Examples 1 to 5.
3 is an FIB-SEM photograph of the cathode active material of Example 1 and an energy spectroscopic analysis (EDS) of the particle cross-sectional layer.
4 is a Fourier transform infrared spectroscopy (FT-IR) analysis graph for the cathode active material of Comparative Example 1 and Examples 1 to 5.
Fig. 5 is a graph showing evaluation of life characteristics of Comparative Example 1 and Examples 1 to 5. Fig.
FIG. 6 is a graph showing C-rate characteristics for Example 2 and Comparative Example 1. FIG.

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

In one embodiment of the present invention, there is provided a cathode active material for a lithium secondary battery comprising a lithium manganese oxide doped with phosphorus (P) based anions. The cathode active material has excellent lifetime characteristics and output characteristics, and particularly excellent lifetime characteristics at high temperatures.

The fact that the phosphorus anion is doped into the lithium manganese oxide means that the phosphorus anion is substituted into a part of the oxygen sites of the lithium manganese oxide.

The phosphorus anion may be specifically a phosphate anion, for example, PO ₄ ^{3 -} .

Since the ion radius of the phosphorus anion is 2.78 Å and larger than 1.32 Å, which is the ion radius of the oxygen ion (O ^{2 -} ), the lattice constant may increase as the phosphorus anion enters part of the oxygen sites. Accordingly, insertion and desorption of lithium ions during charging and discharging are considered to be easy.

On the other hand, the lithium manganese oxide doped with the phosphorus anion may be further doped with aluminum cations. In this case, the cathode active material has improved high-temperature lifetime characteristics and output characteristics.

The lithium manganese oxide doped with the phosphorus-based anion may be represented by the following formula (1).

[Chemical Formula 1]

Li _x Mn _{2 - y} Al _y O _{4 -z} (PO ₄ ) _z

In the above formula (1), 0.9? X? 1.5, 0? Y? 0.1, and 0.001? Z?

When the lithium manganese oxide represented by Formula 1 is used as the cathode active material, the high temperature lifetime characteristics and the output characteristics of the battery can be improved.

Specifically, the range of x in the formula (1) may be 1.0? X? 1.5, 0.9? X? 1.4, 0.9? X? 1.3, and 0.9? X? 1.2. When x satisfies the above range, the positive electrode active material can realize excellent battery characteristics.

0.003? Z? 0.009, 0.003? Z? 0.008, 0.003? Z? 0.007, 0.005? Z? 0.02, 0.005? Z? 0.01. When z satisfies the above range, the cathode active material can exhibit excellent high-temperature lifetime characteristics.

Y may be 0 <y? 0.1, 0.01? Y? 0.1, 0.02? Y? 0.1, 0.03? Y? 0.1, 0.04? Y? 0.1, 0.05? Y? When y satisfies the above range, the cathode active material can exhibit excellent high-temperature lifetime characteristics.

The lattice constant of the lithium anion-doped lithium manganese oxide may be 8.2085 to 8.2300, specifically 8.2085 to 8.2250. When the lattice constant in the above range is satisfied, insertion and removal of lithium can be facilitated during charging and discharging, and the output characteristics can be improved.

The cathode active material may be in the form of secondary particles in which primary particles are aggregated. The average particle diameter of the secondary particles may be 8 탆 to 30 탆, specifically 8 탆 to 25 탆, 8 탆 to 20 탆, 10 탆 to 30 탆, 10 탆 to 25 탆 and 10 탆 to 20 탆. When the average particle diameter of the secondary particles satisfies the above range, the cathode active material can exhibit excellent battery characteristics.

The primary particles may have an average particle diameter of 0.1 탆 to 5 탆, specifically 0.5 탆 to 5 탆, 1 탆 to 5 탆, 1 탆 to 4 탆, and 1 탆 to 3 탆. When the average particle diameter of the primary particles satisfies the above range, the cathode active material can exhibit excellent battery characteristics.

The average particle diameter may mean D50, and D50 means a particle size at 50% by volume ratio in a cumulative size-distribution curve.

The cathode active material may be spherical. Specifically, the cathode active material may be in the form of spherical secondary particles in which the primary particles are tightly aggregated. In this case, the cathode active material may exhibit excellent battery characteristics.

The doping amount of the phosphorus anion may increase as the surface of the lithium manganese oxide doped with the phosphorus anion is doped. It is believed that phosphorus anions migrate to the surface of the particles during the preparation of lithium manganese oxide doped with phosphorus anions.

When aluminum is further doped in the lithium manganese oxide doped with the phosphorus anion, the doping amount of the aluminum may increase as the lithium manganese oxide is further doped. It is believed that aluminum migrates to the inside of the particles during the production of the lithium manganese oxide.

The content of phosphorus (P) measured by inductively coupled plasma (ICP) analysis in the cathode active material is 0.01 ppm to 0.5 ppm, specifically 0.01 ppm to 0.4 ppm, 0.01 ppm to 0.3 ppm, 0.01 ppm to 0.25 ppm, 0.02 ppm to 0.5 ppm, 0.03 ppm to 0.5 ppm, 0.04 ppm to 0.5 ppm, 0.05 ppm to 0.5 ppm, 0.06 ppm to 0.5 ppm, 0.06 ppm to 0.3 ppm, 0.06 ppm to 0.25 ppm. In this case, the cathode active material can exhibit excellent lifetime characteristics and output characteristics.

According to another embodiment of the present invention, there is provided a method for producing a metal salt, comprising: preparing an aqueous metal salt solution containing a lithium source, a manganese source, and a phosphorus source; Pulverizing the aqueous metal salt solution; Spray-drying the pulverized metal salt aqueous solution to prepare a metal oxide precursor; Heat treating the metal oxide precursor; And a step of obtaining a lithium manganese oxide doped with a phosphorus-based anion.

The cathode active material obtained by the above production method has excellent lifetime characteristics and output characteristics, and particularly excellent lifetime characteristics at high temperatures.

The general solid-phase method is manufactured through a heat treatment and a grinding process after mixing metal raw materials, and there is a limit to the raw material mixing. The cathode active material produced by the solid phase method generally grows into an amorphous particle form having a large specific surface area of the particles, so that the side reaction with the electrolyte is increased and the elution of manganese is increased.

However, the manufacturing method of one embodiment is a wet spray drying method, whereby a uniform mixing of the raw materials is achieved, and a spherical particle shape having a relatively small specific surface area is formed. Such a cathode active material has a reduced contact surface with the electrolyte, thereby reducing the side reaction with the electrolyte, reducing the elution of manganese and increasing the tap density.

The lithium source may be, for example, lithium carbonate, lithium hydroxide, lithium nitrate, lithium oxide, or a combination thereof.

The manganese raw material may be manganese dioxide, manganese sulfate, manganese nitrate, manganese hydrochloride, manganese nitrate, or a combination thereof.

The phosphorous source may be, for example, NH ₄ H ₂ PO ₄ , C ₆ H ₁₈ O ₈ P ₂ , C ₄ H ₁₁ O ₄ P, C ₆ H ₁₃ O ₉ P, AlPO ₄ , or a combination thereof.

In the aqueous metal salt solution, the phosphorus source may be contained in an amount of 0.001 to 0.02 mols relative to 1 mole of the lithium source, specifically 0.003 to 0.02 mols, 0.003 to 0.01 mols, 0.003 to 0.009 mols, 0.003 to 0.008 mols, 0.003 to 0.007 mols , 0.005 to 0.02 mole, and 0.005 to 0.01 mole. In this case, the cathode active material can exhibit excellent high-temperature lifetime characteristics.

The aqueous metal salt solution may further comprise an aluminum raw material. In this case, a lithium manganese oxide doped with phosphorus anions and aluminum cations can be obtained by the above production method.

The aluminum source may be, for example, aluminum hydroxide, aluminum sulfate, aluminum nitrate, aluminum acetate, aluminum chloride, or a combination thereof.

In the metal salt aqueous solution, the concentration of the aluminum raw material may be 0.01M to 0.1M, specifically 0.02M to 0.1M, 0.03M to 0.1M, 0.04M to 0.1M, and 0.05M to 0.1M. In this case, the cathode active material may exhibit excellent battery characteristics.

The step of pulverizing the metal salt aqueous solution may be such that the raw material particles are pulverized to have a particle diameter of 1 탆 or less, specifically 0.6 탆 or less. In this case, the spray drying step as the next step can be effectively performed.

The average particle diameter of the obtained metal oxide precursor may be 8 to 30 탆, specifically, 탆 to 25 탆, 8 to 20 탆, 10 to 30 탆, 10 to 25 탆, and 10 to 20 탆. In this case, the prepared positive electrode active material can exhibit excellent battery characteristics.

The step of heat-treating the metal oxide precursor may be performed at a temperature of 850 ° C to 950 ° C, specifically 850 ° C to 940 ° C, 850 ° C to 930 ° C, 850 ° C to 920 ° C, 850 ° C to 910 ° C, have. In this case, the lithium manganese oxide doped with phosphorus anions can be effectively produced, and the cathode active material containing the lithium manganese oxide can realize excellent battery characteristics.

The phosphorus-doped anion-doped lithium manganese oxide is as described above, and may be represented by the following formula (1).

[Chemical Formula 1]

Li _x Mn _{2 - y} Al _y O _{4 -z} (PO ₄ ) _z

In the above formula (1), 0.9? X? 1.5, 0? Y? 0.1, and 0.001? Z?

A detailed description of the formula 1 is as described above.

According to another embodiment of the present invention, there is provided a lithium secondary battery including the positive electrode, the negative electrode, and the electrolyte containing the positive electrode active material.

The positive electrode includes a current collector and a positive electrode active material layer formed on the current collector.

Al may be used as the current collector, but the present invention is not limited thereto.

The cathode active material layer includes a cathode active material, a binder, and optionally a conductive material.

The binder may be selected from, for example, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers comprising ethylene oxide, Styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, and the like can be used.

The conductive material is used for imparting conductivity to the electrode. Any conductive material can be used without causing any chemical change in the battery. Examples of the conductive material include metal powders such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, copper, nickel, aluminum and silver, metal fibers and the like, and conductive materials such as polyphenylene derivatives May be used alone or in combination.

The negative electrode includes a current collector and a negative electrode active material layer formed on the current collector.

The current collector may be a copper foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foil, a copper foil, a polymer substrate coated with a conductive metal, or a combination thereof.

The negative electrode active material layer includes a negative electrode active material, a binder composition, and / or a conductive material.

The negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, a lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

Descriptions of the negative electrode active material, the binder composition and the conductive material will be omitted.

The electrolyte includes a non-aqueous organic solvent and a lithium salt. The non-aqueous organic solvent and the lithium salt can be used as long as they are compatible with each other, so that detailed explanation is omitted.

Hereinafter, examples and comparative examples of the present invention will be described. The following examples are only illustrative of the present invention and are not intended to limit the scope of the present invention.

Comparative Example  One ( Al Doped LMO )

(1) Preparation of cathode active material

1.03M of Li ₂ CO _3, 1.92M of MnO _{2 and} 0.08M of Al (OH) ₃ were respectively measured as starting materials and sufficiently dissolved in distilled water, followed by wet pulverization. Wet milling used a small zirconium ball having a size of 0.65 mm for milling and uniform mixing of raw materials and circulated the slurry for 1 hour and a half at a high rotation speed of the zirconium ball at 2,800 rpm.

The slurry was first pulverized / mixed to obtain a slurry having a primary agglomeration of about 0.6 mu m, followed by agitation and wet spray drying. The slurry sprayed through the atomizer nozzles was subjected to secondary agglomeration at an internal temperature of 120 ° C and controlled to adjust the air pressure to obtain a desired particle size.

Thereafter, the synthesis was carried out by heat treatment at 885 ° C for 2 hours, and the heating rate was 2 ° C / min. The heat treated cathode active material was pulverized using induction and classified to finally produce Al-doped lithium manganese oxide.

(2) Lithium secondary battery ( Half - cell )

Lithium foil was used as a counter electrode and a porous polyethylene membrane was used as a separator. A coin cell of the R2032 type was fabricated using a common carbonate-based commercial electrolyte.

Example  1 to 5 ( PO ₄ - Al Doped LMO )

As in Comparative Example 1, except that ammonium phosphate (NH ₄ H ₂ PO ₄ ) 0.003, 0.005, 0.007, 0.01, 0.02 M was further added to the wet pulverization process as the phosphorus anion doping raw material in the starting material The cathode active material of PO ₄ -Al-doped lithium manganese oxide was prepared by wet spray drying and calcination.

Thereafter, a coin cell was produced in the same manner as in Comparative Example 1.

The formulas of the cathode active material prepared in Comparative Example 1 and Examples 1 to 5 are shown in Table 1 below.

division The Comparative Example 1 _{Li 1 .03 Mn 1 .92 Al 0} .08 O 4 Example 1 _{Li 1 .03 Mn 1 .92 Al 0} .08 O 3 .997 (PO 4) 0.003 Example 2 _{Li 1 .03 Mn 1 .92 Al 0} .08 O 3 .995 (PO 4) 0.005 Example 3 _{Li 1 .03 Mn 1 .92 Al 0} .08 O 3 .995 (PO 4) 0.007 Example 4 _{Li 1 .03 Mn 1 .92 Al 0} .08 O 3 .99 (PO 4) 0.01 Example 5 _{Li 1 .03 Mn 1 .92 Al 0} .08 O 3 .98 (PO 4) 0.02

Evaluation example  1: X-ray diffraction  Analysis (X- ray diffraction ; XRD )

XRD analysis was performed on the cathode active materials prepared in Comparative Example 1 and Examples 1 to 5, and the results are shown in Fig.

Fig. 1 shows the results of XRD analysis for Comparative Examples and Examples. As a result of the analysis, the peak of the spinel structure can be confirmed, and the change due to the doping of Al and phosphorus anions and the change of the doping amount of the phosphorus anions were not found. There is a difference in intensity, but all of the examples are results with no significant difference. As a result, it can be confirmed that a small amount of the doping material added during lithium manganese oxide synthesis does not exist separately or interfere with the synthesis.

Evaluation example  2: Measurement of lattice constant

The lattice constants of the cathode active materials of Comparative Example 1 and Examples 1 to 5 were measured and are shown in Table 2 below. As shown in Table 2, the anion PO ₄ ^{3 -} (ionic radius: 2.78 Å) enters the O ^{2 -} (ionic radius: 1.32 Å) site during the synthesis of lithium manganese oxide and the lattice constant increases with increasing doping amount of phosphorus anion Can be confirmed.

division The Lattice constant (A) (error) Comparative Example 1 _{Li 1 .03 Mn 1 .92 Al 0} .08 O 4 8.2083 (0.00076) Example 1 _{Li 1 .03 Mn 1 .92 Al 0} .08 O 3 .997 (PO 4) 0.003 8.2086 (0.00084) Example 2 _{Li 1 .03 Mn 1 .92 Al 0} .08 O 3 .995 (PO 4) 0.005 8.2092 (0.00094) Example 3 _{Li 1 .03 Mn 1 .92 Al 0} .08 O 3 .995 (PO 4) 0.007 8.2127 (0.00107) Example 4 _{Li 1 .03 Mn 1 .92 Al 0} .08 O 3 .99 (PO 4) 0.01 8.2160 (0.00118) Example 5 _{Li 1 .03 Mn 1 .92 Al 0} .08 O 3 .98 (PO 4) 0.02 8.2206 (0.00145)

Evaluation example  3: Scanning electron microscope ( SEM ) Shooting

The cathode active materials of Comparative Example 1 and Examples 1 to 5 were photographed by a scanning electron microscope (SEM), and the results are shown in Fig.

In Fig. 2, no difference was observed due to the doping of Al and phosphorus anions. Referring to FIG. 2, it can be seen that primary particles of 1 to 3 μm solidly clump together to form spherical secondary particles of about 18 μm.

Evaluation example  4: Energy spectroscopic analysis ( EDS )

The cathode active material of Example 1 was photographed with FIB-SEM to confirm the inside of the particles, and the particle cross-sectional layer was analyzed by energy dispersive spectroscopy (EDS). The results are shown in FIG.

As a result of analyzing the three elements 1, 2 and 3 shown in the photograph of FIG. 3, it can be seen that the P ₄ of the PO ₄ is clearly present in the pores 1 and 2 inside. On the other hand, in the dense part 3, Al was relatively larger than P.

This is another proof that the phosphorus anion was substantially incorporated into the synthesis of lithium manganese oxide and was confirmed inside the particle.

In addition, through the FIB-SEM cross-section analysis, Al in the doping material migrates to the inside of the particle and phosphorus anion moves to the surface of the particle in the synthesis process through the heat treatment, and phosphorus anions are concentrated in the pore portion, It is considered that Al is relatively large.

Evaluation example  5: Inductive coupling plasma  analysis( ICP ; inductively coupled plasma )

ICP analysis was performed on the cathode active materials of Comparative Example 1 and Examples 1 to 5 to quantitatively determine the amount of elements, and the results are shown in Table 3 below.

division Al Li P Comparative Example 1 1.33 4.40 N.D. Example 1 1.32 4.43 0.0671 Example 2 1.32 4.44 0.1052 Example 3 1.33 4.44 0.1587 Example 4 1.32 4.45 0.2130 Example 5 1.34 4.50 0.2450

In Table 3, each content unit is ppm.

From Table 3, it can be seen that the content of P increases with increasing doping amount of phosphorus anion.

Evaluation example  6: FT - IR  ( Fourier Transform Infrared Spectroscopy ) analysis

4 is a Fourier transform infrared spectroscopy (FT-IR) analysis graph for the cathode active material of Comparative Example 1 and Examples 1 to 5.

A small amount of phosphorus anion which can not be confirmed by the XRD analysis can be confirmed by FT-IR analysis. Except for Comparative Example 1, in all of the wavelengths 1410 to 1200 cm ^-1 and 580 to 450 cm ^-1 , all of Examples 1 to 5 were PO ₄ Anion can be confirmed, and it can be confirmed that the amount of PO ₄ doping is sequentially increased depending on the degree of absorption.

Evaluation example  7: Evaluation of high-temperature lifetime characteristics of battery

Fig. 5 is a graph showing evaluation of life characteristics of Comparative Example 1 and Examples 1 to 5. Fig. The lifetime characteristics were evaluated at cut-off of 3.0 ~ 4.3V at 55 ℃. As a result of charging / discharging 50 times by applying a constant current corresponding to 1C, it was found that Al-doped Comparative Example 1 maintained 98.1% of the initial discharge capacity after 50 cycles.

In the graphs of Examples 1 to 5 in which PO ₄ was additionally doped with Al, the capacity retention rates after 50 cycles were respectively 98.6, 99.0, 98.1, 96.6 and 95.0%.

Also, in the graphs of Examples 1 to 5, the initial discharge capacity tends to increase as the doping amount of the phosphorus anion increases.

As a result, Examples 1 to 3 exhibited superior high-temperature lifetime characteristics to those of Comparative Example 1, and in Example 2, the capacity retention rate was remarkably excellent at 50 cycles. In addition, the cells of Examples 1 to 5 showed an increase in initial capacity as compared with Comparative Example 1. Especially, in Examples 3 to 5, the initial discharge capacity was remarkably increased as compared with Comparative Example 1.

Evaluation example  8: C- rate  Character rating

The C-rate characteristics for Example 2 and Comparative Example 1 are shown in FIG. Similar to the evaluation of the lifetime characteristics, the cut-off was conducted at 3.0 to 4.3 V and the temperature was measured at 25 캜. 0.1, 0.2, 0.5, 1, 3, 5, and 7C, and the discharge capacity corresponding to each current is shown in FIG.

The discharge efficiencies of 5C and 7C versus 0.1C are 85.79 and 78.72%, respectively, in Example 2, and the C-rate characteristics are much higher than those of Comparative Example 1 at 82.04 and 72.13%.

This is because the increase of the lattice constant due to the doping of the phosphorus anion facilitates the insertion and desorption of lithium ions, and thus the C-rate characteristics are high at a high rate.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. As will be understood by those skilled in the art. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

Claims (21)

A lithium manganese oxide doped with phosphorus (P) based anions. The method of claim 1,
Wherein the phosphorus anion is a PO ₄ ^{3 -} phosphorus cathode active material for a lithium secondary battery. The method of claim 1,
Wherein the lithium manganese oxide doped with phosphorus anion is further doped with aluminum. The method of claim 1,
Wherein the lithium manganese oxide doped with phosphorus-based anions is represented by the following Formula 1:
[Chemical Formula 1]
Li _x Mn _{2 - y} Al _y O _{4 -z} (PO ₄ ) _z
In the above formula (1), 0.9? X? 1.5, 0? Y? 0.1, and 0.001? Z? The method of claim 1,
0.003? Z? 0.007 in the above formula (1). The method of claim 1,
Wherein 0.05? Y? 0.1 in the above formula (1). The method of claim 1,
Wherein the lithium manganese oxide doped with phosphorus anion has a lattice constant of 8.2085 to 8.2300. The method of claim 1,
The cathode active material is in the form of secondary particles in which primary particles are aggregated,
Wherein the secondary particles have an average particle diameter of 8 to 30 占 퐉. 9. The method of claim 8,
Wherein the primary particles have an average particle diameter of 0.1 占 퐉 to 5 占 퐉. The method of claim 1,
The content of phosphorus (P) in the positive electrode active material as measured by inductively coupled plasma (ICP) analysis is 0.01 ppm to 0.5 ppm. The method of claim 1,
Wherein the cathode active material is a spherical cathode active material for a lithium secondary battery. Preparing a metal salt aqueous solution containing a lithium source, a manganese source, and a phosphorus source;
Pulverizing the aqueous metal salt solution;
Spray-drying the pulverized metal salt aqueous solution to prepare a metal oxide precursor;
Heat treating the metal oxide precursor; And
Thereby obtaining a lithium manganese oxide doped with a phosphorus anion. The method for producing a cathode active material for a lithium secondary battery according to claim 1, The method of claim 12,
The phosphorus raw material may be at least one selected from the group consisting of NH ₄ H ₂ PO ₄ , C ₆ H ₁₈ O ₈ P ₂ , C ₄ H ₁₁ O ₄ P, C ₆ H ₁₃ O ₉ P, AlPO ₄ , Gt; The method of claim 12,
Wherein the phosphorus raw material is contained in an amount of 0.001 to 0.02 mol based on 1 mol of the lithium source. The method of claim 12,
Wherein the metal salt aqueous solution further comprises an aluminum raw material. 16. The method of claim 15,
Wherein the concentration of the aluminum raw material in the aqueous metal salt solution is 0.05M to 0.1M. The method of claim 12,
Wherein the pulverizing the metal salt aqueous solution is carried out by pulverizing the raw materials so that the particle diameters of the raw materials are not more than 1 占 퐉. The method of claim 12,
Wherein the step of heat-treating the metal oxide precursor is performed at 850 캜 to 950 캜. The method of claim 12,
Wherein the average particle diameter of the metal oxide precursor is 8 占 퐉 to 30 占 퐉. The method of claim 12,
The obtained phosphorus-anion-doped lithium manganese oxide is represented by the following Formula 1:
[Chemical Formula 1]
Li _x Mn _{2 - y} Al _y O _{4 -z} (PO ₄ ) _z
In the above formula (1), 0.9? X? 1.5, 0? Y? 0.1, and 0.001? Z? A positive electrode comprising the positive electrode active material according to any one of claims 1 to 11,
Cathode, and
A lithium secondary battery comprising an electrolytic solution.

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