KR20060046546A - Modified lithium manganese nickel composite oxide, method for preparing the same, positive electrode active material of lithium secondary battery, and lithium secondary battery - Google Patents

Abstract

The present invention provides a modified lithium manganese nickel-based composite oxide useful as a positive electrode active material of a lithium secondary battery, a manufacturing method thereof, a lithium secondary battery positive electrode active material, and a lithium secondary battery having excellent cycle characteristics and coulombic efficiency.

The present invention is characterized in that the particle surface of the lithium manganese nickel-based composite oxide represented by the following formula (1) is coated with a metal oxide containing at least one metal element selected from Mg, Al, Ti, Zr, and Zn. A modified lithium manganese nickel-based composite oxide, a method for producing the same, a lithium secondary battery positive electrode active material, and a lithium secondary battery.

<Formula 1>

Li _x Mn _1.5 Ni _0.5 O _4-w

In the formula, 0 <x <2, 0 ≦ w <2.

Modified lithium manganese nickel-based composite oxide, positive electrode active material, lithium secondary battery

Description

Modified Lithium Manganese Nickel Composite Oxide, Method For Preparing The Same, Positive Electrode Active Material of Lithium Secondary Battery, and Lithium Secondary Battery

1 is a scanning electron micrograph showing the particle surface state of the modified lithium manganese nickel-based composite oxide obtained in Example 1. FIG.

2 is a scanning electron micrograph showing the particle surface state of the modified lithium manganese nickel-based composite oxide obtained in Example 2. FIG.

3 is a diagram showing an initial discharge capacity curve when the modified lithium manganese nickel-based composite oxide obtained in Example 1 is used as a positive electrode active material of a lithium secondary battery.

4 is a diagram showing an initial discharge capacity curve when the modified lithium manganese nickel-based composite oxide obtained in Example 2 is used as a positive electrode active material of a lithium secondary battery.

5 is a diagram showing an initial discharge capacity curve when the modified lithium manganese nickel-based composite oxide obtained in Example 3 is used as a positive electrode active material of a lithium secondary battery.

[Document 1] Japanese Unexamined Patent Publication No. 2001-122626

[Document 2] Japanese Unexamined Patent Publication No. 2002-226213

[Document 3] Japanese Unexamined Patent Publication No. 2001-185148

[Document 4] Japanese Unexamined Patent Publication No. 2002-158007

[Document 5] Japanese Unexamined Patent Publication No. 2003-81637

The present invention relates to a modified lithium manganese nickel-based composite oxide useful as a lithium secondary battery positive electrode active material, a manufacturing method thereof, a lithium secondary battery positive electrode active material, and a lithium secondary battery having excellent cycle characteristics and coulombic efficiency.

The present applicant previously proposed a method for producing a lithium manganese composite oxide useful as a positive electrode active material of a lithium secondary battery (Japanese Patent Laid-Open No. 2001-122626 and Japanese Patent Laid-Open No. 2002-226213). The lithium manganese composite oxide prepared according to this manufacturing method has a distinctive particle size distribution and high fluidity. When the lithium manganese composite oxide is used as a positive electrode active material of a lithium secondary battery, the initial discharge capacity is increased and the capacity retention rate of the discharge capacity is increased. . In addition, this lithium manganese composite oxide is characterized by low elution amount of manganese ions and high storage characteristics even when contacted with a nonaqueous electrolyte solution of a lithium secondary battery.

In the above lithium manganese composite oxide, a lithium manganese nickel composite oxide in which a part of manganese is replaced with another transition metal element such as nickel is also known (Japanese Patent Laid-Open No. 2001-185148, Japanese Patent Laid-Open No. 2002-158007, Japanese Unexamined Patent Publication No. 2003-81637 gazette), in particular _{Li [Mn 3/2 Ni 1} /2] O _4, those having a composition of other than the lithium-manganese composite oxide has good cycle characteristics, and the lithium manganese composite oxide is 4 V region It has the advantage of having an electromotive force in the 5 V region compared to having an electromotive force of.

However, lithium manganese nickel-based composite oxides have a large amount of elution of manganese ions, and in the case of Li calcination by mixing nickel oxide, manganese oxide, and lithium compound, the actual discharge capacity is expressed only about the theoretical amount of moisture. There was this. Therefore, there has been a demand for development of a lithium manganese nickel-based composite oxide, a manufacturing method thereof, a lithium secondary battery positive electrode active material, and particularly a lithium secondary battery having excellent cycle characteristics and coulombic efficiency.

An object of the present invention is to provide a modified lithium manganese nickel-based composite oxide useful as a positive electrode active material of a lithium secondary battery, a method for producing the same, a lithium secondary battery positive electrode active material, and a lithium secondary battery having excellent cycle characteristics and coulombic efficiency.

As a result of intensive studies in this situation, the present inventors have found that lithium secondary manganese modified lithium manganese nickel-based composite oxide coated with a specific metal oxide particle surface of a lithium manganese nickel-based composite oxide represented by a specific formula is a lithium secondary material using a positive electrode active material. The battery was found to be excellent in battery performance, in particular in cycle characteristics and coulombic efficiency, and came to complete the present invention.

The first invention provided by the present invention is a metal oxide wherein the particle surface of the lithium manganese nickel-based composite oxide represented by the following formula (1) contains at least one metal element selected from Mg, Al, Ti, Zr and Zn. A modified lithium manganese nickel-based composite oxide, which is coated.

Li _x Mn _1.5 Ni _0.5 O _4-w

In the formula, 0 <x <2, 0 ≦ w <2.

Moreover, the 2nd invention which this invention provides,

First process; Lithium manganese nickel-based composite oxide represented by the formula (1) and one or two or more metal oxides of a compound containing at least one metal element selected from Mg, Al, Ti, Zr and Zn by dry mixing the composite Attaching the particles of the metal oxide to the particle surface of the oxide, and

Second process; A method of producing a modified lithium manganese nickel-based composite oxide, comprising the step of heating the composite oxide with a metal oxide obtained in the first step to obtain a modified lithium manganese-based composite oxide.

 <Formula 1>

_{Li x Mn 1 .5 Ni 0 .5} O 4 -w

In the formula, 0 <x <2, 0 ≦ w <2.

Moreover, the 3rd invention which this invention provides is a lithium secondary battery positive electrode active material characterized by including the modified lithium manganese complex oxide of the said 1st invention. Moreover, 4th invention provided by this invention uses the lithium secondary battery positive electrode active material of the said 3rd invention, It is a lithium secondary battery characterized by the above-mentioned.

In the modified lithium manganese nickel-based composite oxide of the present invention, elution of manganese ions is suppressed, and a lithium secondary battery using the modified lithium manganese nickel-based composite oxide as a positive electrode active material exhibits excellent cycle characteristics and coulombic efficiency.

Best Mode for Carrying Out the Invention

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated based on the preferable embodiment.

The modified lithium manganese nickel-based composite oxide of the present invention is a metal oxide in which the particle surface of the lithium manganese nickel-based composite oxide represented by the following formula (1) contains at least one metal element selected from Mg, Al, Ti, Zr, and Zn. It is characterized by being covered with.

<Formula 1>

Li _x Mn _1.5 Ni _0.5 O _4-w

In the formula, 0 <x <2, 0 ≦ w <2.

(Lithium Manganese Nickel Composite Oxide)

Preferred physical properties of the lithium manganese nickel-based composite oxide represented by Chemical Formula 1 are those having an average particle diameter of 5 to 15 µm, preferably 8 to 12 µm. The reason is that if the average particle diameter is less than 5 µm, the electrode density is small and the amount of manganese elution tends to increase due to the increase of the specific surface area, while if the average particle diameter exceeds 15 µm, the charge and discharge characteristics tend to be poor.

In addition, an average particle diameter can be calculated | required by the laser method particle size distribution measuring method (Hereafter, in the case of an average particle diameter, it means the value calculated | required by this measuring method).

In addition, the lithium manganese nickel-based composite oxide may be primary particles or aggregated particles in which primary particles are aggregated.

In addition, the BET specific surface area of the lithium manganese nickel-based composite oxide is 0.2 to 0.6 m 2 / g, preferably 0.2 to 0.45 m 2 / g. When the BET specific surface area is in the above range, it is preferable because the safety of the lithium secondary battery using the modified lithium manganese nickel-based composite oxide obtained as a positive electrode active material is good.

 In addition, the particle surface of the lithium manganese nickel system complex oxide in this invention also includes the surface of the aggregate particle which the primary particle or the primary particle aggregated.

The lithium manganese nickel-based composite oxide to be modified can be obtained by any manufacturing method. As an example thereof, (A) a mixed aqueous solution of manganese salt and nickel salt having an atomic ratio of manganese and nickel of 3: 1 in the presence of a complexing agent in an aqueous solution of pH 9 to 13 is reacted with an alkaline solution and coprecipitated to give manganese. Step A-1 to obtain a manganese nickel composite hydroxide and / or manganese nickel composite oxide having an atomic ratio of 3: 1 to 3; and a total atomic ratio of manganese and nickel to 2: 1 in an atomic ratio of lithium. Preferably, the A-2 step of firing the mixture of the hydroxide and / or oxide and the lithium compound at 850 ° C. or higher, and the A-B of further firing the mixture after firing obtained in the A-2 step at 650 to 800 ° C. (3) A method of carrying out the step 3 (see, for example, Japanese Unexamined Patent Application Publication No. 2002-158007), (B) a complex compound of manganese and nickel or a mixture of manganese compounds and nickel compounds is used as a starting material, which is 950 to Heat treatment at 1050 ° C. to form a first precursor, and after cooling the first precursor, heat treatment at 550 to 750 ° C. to form a second precursor, and after cooling the second precursor, it is mixed with a lithium compound to 800 to Although the method of baking at 1000 degreeC, etc. are mentioned, In this invention, especially when using the lithium manganese nickel system complex oxide obtained by the manufacturing method of said (B), elution of a manganese ion is effectively suppressed, and this lithium manganese nickel system A lithium secondary battery using a modified lithium manganese nickel-based composite oxide obtained by coating the particle surface of the composite oxide with the metal oxide as the positive electrode active material is particularly preferable in that it exhibits excellent cycle characteristics and coulombic efficiency.

The manufacturing method of (B) is divided roughly into (a) manufacturing process of starting material, (b) heat processing of 1st stage, (c) heat processing of 2nd stage, and (d) Li calcination process.

Hereinafter, each process is demonstrated.

(a) Process for preparing starting material

The starting materials in this process are (a) complex compounds of manganese and nickel or (b) mixtures of manganese compounds with nickel compounds. As the complex compound (a), a complex hydroxide, a complex oxyhydroxide, a complex carbonate or a complex oxide of manganese and nickel is preferably used. These complex compounds can be used 1 type or in combination of 2 or more types. For example, a composite hydroxide and a composite oxyhydroxide can be used in combination. In these composite compounds, it is preferable that the atomic ratio of manganese and nickel is Mn: Ni = 75: 25. It is preferable to use a composite hydroxide or a composite oxyhydroxide among these complex oxides. Said composite oxide can be manufactured by co-precipitation method, for example. Specifically, for example, when manufacturing a composite hydroxide, the composite hydroxide can be co-precipitated by mixing a mixed aqueous solution containing a manganese compound and a nickel compound, an aqueous complexing agent solution, and an aqueous alkali solution. The ratio of the manganese compound and the nickel compound in the mixed aqueous solution is such that the atomic ratio of manganese and nickel in the obtained composite hydroxide is 75:25.

As a manganese compound in the said mixed aqueous solution, the water-soluble salt of manganese, such as manganese sulfate, manganese nitrate, manganese chloride, etc. is mentioned, for example. As a nickel compound, the water-soluble salt of nickel, such as nickel sulfate, nickel nitrate, nickel chloride, etc. is mentioned, for example.

As the complexing agent, those which can form a complex with manganese and nickel are used. For example, an ammonium ion source (ammonia, ammonium chloride, ammonium carbonate, ammonium fluoride), hydrazine, ethylenediamine tetraacetate, glycine, etc. are mentioned. During the coprecipitation operation, the pH of the reaction solution is maintained in the range of about 9 to about 13. In the maintenance of pH, the said alkali aqueous solution, for example, sodium hydroxide or potassium hydroxide is used. As a manufacturing method of a composite hydroxide, in addition to the method mentioned above, the method of Unexamined-Japanese-Patent No. 2002-201028 can also be used, for example.

In the case of using the composite oxyhydroxide instead of the above-described complex hydroxide, after obtaining the precipitate of the composite hydroxide according to the coprecipitation operation described above, air can be blown into the reaction solution to oxidize the composite hydroxide. Thereby, a composite oxyhydroxide is obtained.

In the case of using a composite oxide, after obtaining a precipitate of the composite hydroxide by coprecipitation operation, it can be heat-treated at 200-500 degreeC, for example. As a result, a composite oxide is obtained.

In the case of using the composite carbonate, the composite carbonate can be coprecipitated by mixing a mixed aqueous solution containing a manganese compound and a nickel compound, an aqueous solution of a complexing agent, an alkali carbonate or an aqueous alkali carbonate solution. Moreover, a composite carbonate can also be obtained by introducing a carbon dioxide gas into the mixed aqueous solution. The ratio of the manganese compound and the nickel compound in the mixed aqueous solution is preferably such that the atomic ratio of manganese and nickel in the obtained composite carbonate is 75:25. As an alkali carbonate or an alkali hydrogen carbonate, sodium carbonate, potassium carbonate, sodium hydrogencarbonate, etc. are mentioned, for example.

On the other hand, when using a mixture of (b) as a starting material, manganese oxide, hydroxide, oxyhydroxide or carbonate is preferably used as the manganese compound. Likewise, nickel oxides, hydroxides, oxyhydroxides or carbonates are preferably used as the nickel compound. In this case, it is preferable to use the same kind as a kind of manganese compound and a nickel compound. For example, when using an oxide as a manganese compound, it is preferable to use an oxide also as a nickel compound. A particularly preferred combination is a combination of manganese dioxide and nickel oxide. The manganese compound and the nickel compound are preferably mixed in a mixture such that the atomic ratio of manganese and nickel in the mixture is Mn: Ni = 75: 25.

(b) Step 1 heat treatment process

The starting material obtained in the process of (a) is heat treated to 950 to 1050 ° C, preferably 970 to 1030 ° C, more preferably 980 to 1010 ° C. By this heat treatment, the starting material becomes a first precursor. Although the specific structure of the first precursor is not clear, it is assumed that the starting material is an oxide formed by oxidation. Heat treatment is generally performed in air | atmosphere. It is preferable that the time of heat processing is 5 to 20 hours, especially 8 to 12 hours in consideration of the BET specific surface area of the 1st precursor mentioned later.

In the first heat treatment step, adjusting the specific surface area of the first precursor obtained therefrom is advantageous in that a lithium manganese nickel composite oxide having a low manganese elution amount is obtained. Specifically, the BET specific surface area of the starting material obtained in the process of (a) is generally 10 to 15 m 2 / g, and the BET specific surface area is 0.2 to 0.6 m 2 / g, in particular 0.2 to 2 by heat treatment at this temperature. It is preferable to form the first precursor so as to be 0.45 m 2 / g. By this operation, the starting material, which is a porous particle, is changed into a first precursor, which is a dense particle. In order to make the BET specific surface area of a 1st precursor into the said range, the heating temperature and time of a 1st heat processing process can be adjusted suitably, for example.

(c) second stage heat treatment process

The first precursor obtained in the step (b) is once cooled. Cooling temperature shall be 50 degrees C or less, and simply cools to room temperature. The cooled first precursor is lightly ground to perform a second heat treatment process. In this process the first precursor is heat treated at 550 to 750 ° C., preferably 625 to 675 ° C. By this heat treatment, the first precursor becomes a second precursor. Although the specific structure of the second precursor is not clear, it is assumed that the oxidation state of manganese is an oxide different from that of the first precursor. The atmosphere of the heat treatment can be the same as in the first heat treatment process. It is preferable that the time of heat processing is 8 to 20 hours, especially 10 to 15 hours.

The second precursor obtained by the second stage heat treatment process has the same BET specific surface area as the first precursor or is somewhat smaller than the first precursor. When smaller than the BET specific surface area of the first precursor, the second precursor has a specific surface area of about 95 to 99% of the BET specific surface area of the first precursor.

(d) lithium firing process

The second precursor obtained in the step (c) is once cooled. The cooling temperature can be the same as the cooling temperature of the first precursor. The cooled second precursor is lightly ground and then subjected to a Li calcination process. In the Li calcination process, the second precursor and the lithium compound are mixed and calcined at 800 to 1000 ° C, preferably 850 to 950 ° C, and more preferably 850 to 900 ° C. The atmosphere of baking can be made the same as a 1st and 2nd heat processing process. The firing time is preferably 8 to 20 hours, in particular 10 to 15 hours.

The mixing ratio of the second precursor and the lithium compound is a value at which a spinel oxide is obtained by firing. Specifically, it is preferable to mix the two so that the ratio of the number of moles of lithium and the total amount of manganese and nickel is 0.5 after the Li calcination process. As a lithium compound, it is preferable to use lithium carbonate because it is easy to obtain industrially and is inexpensive. Of course, other lithium compounds such as lithium hydroxide, lithium nitrate, lithium oxide and the like can also be used.

By the above baking operation, the lithium manganese nickel composite oxide represented by General formula (1) which is a target object is obtained. This composite oxide is further reduced in amount by adjusting the BET specific surface area of the first precursor obtained in the first stage heat treatment step described above.

The lithium manganese nickel-based composite oxide obtained by the calcination step has a BET specific surface area of the same degree as that of the second precursor or somewhat smaller than the second precursor. Therefore, it becomes about the same as or smaller than the BET specific surface area of a 1st precursor. When smaller than the BET specific surface area of the second precursor, the lithium manganese nickel-based composite oxide has a specific surface area of about 95 to 99% of the BET specific surface area of the second precursor. The value of the specific surface area itself is preferably 0.2 to 0.6 m 2 / g, particularly 0.2 to 0.45 m 2 / g, in that the amount of elution of manganese is reduced. In addition, the lithium manganese nickel composite oxide preferably has an average particle diameter of 8 to 12 µm, particularly 10 to 12 µm, in view of electrode density, TAP density, and battery performance.

The lithium manganese nickel compound used by this invention can perform the post-heating process (e) in addition to the process of (a)-(d) mentioned above. In the post-heat treatment step, after cooling the lithium manganese nickel-based composite oxide, heat treatment is preferably performed at 550 to 650 ° C, more preferably 600 to 650 ° C. When the lithium manganese nickel composite oxide obtained by this operation is used as a positive electrode active material of a lithium secondary battery, the amount of leaching of manganese is further reduced, and a modified lithium manganese nickel composite oxide can be obtained. The reason is considered that the structure of the oxygen deficiency in spinel is repaired and trivalent manganese which is considered to be the cause of elution changes to tetravalent manganese which is considered to be difficult to elute. In addition, it has also been found that the coulombic efficiency increases, that is, the irreversible capacity is reduced by changing trivalent manganese to tetravalent manganese. In addition, in the preparation of the lithium manganese nickel-based composite oxide represented by the general formula (1), by changing trivalent manganese to tetravalent manganese, the existence ratio of 5V region (discharge capacity of 5V region and 5V region and 4V It has also been found that the ratio of the sum of the discharge capacities of the regions increases.

In the post-heat treatment step, the lithium manganese nickel composite oxide obtained by the Li calcination step is cooled, and then lightly pulverized, followed by heat treatment. The heating temperature can be the same as the heating temperature of the first and second precursors. The atmosphere of the post-heat treatment step can be the same as the atmosphere of the first and second heat treatment steps. In addition, an oxygen atmosphere can also be used. The heating time is a time at which the structure of the oxygen deficiency in the spinel is sufficiently repaired, and the longer it is, the more effective. It is preferable that it is 5 to 48 hours, especially 10 to 48 hours, considering the balance of structural repair of oxygen deficiency and manufacturing efficiency specifically ,. The post-heat-treated lithium manganese nickel composite oxide is substantially the same composition as before the heat treatment. In addition, the particle properties such as the BET specific surface area and the average particle diameter are also substantially the same.

The lithium manganese nickel composite oxide after the post-heat treatment step has the same BET specific surface area as before the heat treatment or is somewhat smaller than before the heat treatment. When it becomes smaller than the BET specific surface area before heat processing, the lithium manganese nickel complex oxide of a post-heating process has a specific surface area of about 95 to 99% of the BET specific surface area before heat processing.

The lithium manganese nickel-based composite oxide represented by the general formula (1) thus obtained has the above-described specific average particle diameter and BET specific surface area. In the present invention, the molar ratio 1.5 of Mn in the formula of the lithium manganese nickel-based composite oxide includes an error range of ± 0.05, and a molar ratio of Ni of 0.5 includes an error range of ± 0.05.

(Modified Lithium Manganese Nickel Composite Oxide)

In the modified lithium manganese nickel-based composite oxide of the present invention, the particle surface of the lithium manganese nickel-based composite oxide is coated with a metal oxide containing at least one metal element selected from Mg, Al, Ti, Zr and Zn. will be.

In the present invention, the modified lithium manganese nickel-based composite oxide is used, in particular, when the metal oxide covering the particle surface of the lithium manganese nickel-based composite oxide contains one or more metal elements selected from Mg, Al and Ti. In a lithium secondary battery having the positive electrode active material as an active material, the cycle characteristics and the coulombic efficiency are further preferred in that the lithium secondary battery is more excellent.

The coating amount of the metal oxide is 0.05 to 1% by weight, preferably 0.1 to 0.5% by weight. When the coating amount is 0.05 to 1% by weight, the elution of manganese ions is effectively suppressed, and the modified lithium manganese nickel-based composite oxide In the lithium secondary battery using the positive electrode active material, the cycle characteristics and the coulombic efficiency can be improved.

As a preferable physical property of the modified lithium manganese nickel-based composite oxide of the present invention, the average particle diameter is 5 to 15 µm, and preferably 8 to 12 µm. The reason is that, if the average particle diameter is less than 5 µm, the electrode density is small and the amount of elution of manganese tends to increase due to the increase of the specific surface area, while if it exceeds 15 µm, the charge and discharge characteristics tend to be poor. Further, when the BET specific surface area is 0.3 to 1.0 m 2 / g, preferably 0.4 to 0.9 m 2 / g, particularly preferably 0.5 to 0.8 m 2 / g, and the BET specific surface area is 0.3 to 1.0 m 2 / g, manganese elutes This is suppressed, and furthermore, the secondary battery using the modified lithium manganese nickel-based composite oxide as the positive electrode active material is preferable in that the charge and discharge characteristics are good. Further, 1 g of a modified lithium manganese nickel-based composite oxide was added to 5 g of an electrolyte solution in which 1 mol / L of LiPF ₆ was dissolved in a mixed solution of ethylene carbonate and diethyl carbonate in a volume ratio of 1: 2, and 168 at 80 ° C. The amount of Mn dissolved in the electrolyte after being left for a while is 100 ppm or less, preferably 90 ppm or less, and particularly preferably 80 ppm or less.

The modified lithium manganese nickel-based composite oxide of the present invention can be produced by coating the composite oxide with the metal oxide.

As a method of coating, for example, (1) an aqueous slurry containing the complex oxide is prepared, and then at least one selected from Mg, Al, Ti, Zr and Zn in the slurry containing the complex oxide. A method of precipitating hydroxides or oxides of these metals on the particle surface of a lithium manganese nickel-based composite oxide by adding a water-soluble metal salt and an alkali agent, and then heating the obtained product (2) to the organic solvent of the lithium manganese nickel-based composite oxide. The dispersed slurry was prepared, and then, a hydrolyzable organic compound of the metal was dissolved in a slurry in which the composite oxide was dispersed in an organic solvent, and then a hydrolyzable agent capable of hydrolyzing the organic compound of the metal was added to obtain a composite oxide. A hydroxide or oxide of these metals is precipitated on the particle surface, and then the obtained product is The method of heat-processing, or (3) the method of dry-coating the surface of the particle | grains of the said lithium manganese nickel system complex oxide with the said metal oxide, etc. are mentioned in this invention, Among these, the modification obtained by carrying out the coating process by dryness is mentioned. The lithium manganese nickel-based composite oxide is particularly preferable in that manganese ions are reduced, and a lithium secondary battery having the modified lithium manganese nickel-based composite oxide as a positive electrode active material has excellent cycle characteristics and coulombic efficiency.

Next, the method for producing the modified lithium manganese nickel-based composite oxide of the present invention in a dry manner will be described in detail.

The modified lithium manganese nickel-based composite oxide of the present invention can be produced by a method including the following first to second steps.

First process; Lithium manganese nickel-based composite oxide represented by the formula (1) and one or two or more metal oxides of a compound containing at least one metal element selected from Mg, Al, Ti, Zr and Zn by dry mixing the composite Adhering the particles of the metal oxide to the particle surface of the oxide.

<Formula 1>

Li _x Mn _1.5 Ni _0.5 O _4-w

In the formula, 0 <x <2, 0 ≦ w <2.

Second process; The process of heat-processing the complex oxide with a metal oxide obtained at the 1st process, and obtaining a modified lithium manganese system complex oxide.

In addition, since the lithium manganese nickel complex oxide used by a 1st process uses the thing mentioned above, the detailed description is abbreviate | omitted here.

The metal oxide selected from another raw material, Mg, Al, Ti, Zr and Zn, is preferably selected from MgO, γ-Al ₂ O ₃ , TiO ₂ , ZrO ₂ and ZnO, and these may be one or two or more. Can be used.

In addition, it is preferable to use fine ones in order to adhere these metal oxides uniformly and tightly to the particle surface of the lithium manganese nickel-based composite oxide, and have an average particle diameter of 0.005 to 1 µm or less. The reason for this is that when it exceeds 1 m, the metal oxide is hard to adhere to the particle surface of the lithium manganese nickel-based composite oxide and tends to be a simple mixed powder thereof. On the other hand, when the particle size of the metal oxide is less than 0.005 m, lithium manganese This is because the metal oxide particles adhering on the particle surface of the nickel-based composite oxide aggregate and the primary particles which are not in contact with the particle surface of the lithium manganese nickel-based composite oxide tend to return to their original state and act as impurities. Moreover, it is preferable to use the thing of 0.01-0.25 micrometers in average particle diameter of a metal oxide.

Moreover, the compounding quantity of the metal oxide of these raw materials is 0.05-1 weight%, Preferably it is 0.1-0.5 weight%. The reason for this is that if the amount is less than 0.05% by weight, the relative coating amount of the metal oxide present on the surface of the particles of the lithium manganese nickel-based composite oxide is insufficient. Only the effect according to the invention is saturated, on the contrary, the discharge capacity per weight tends to decrease.

Subsequently, a predetermined amount of the lithium manganese nickel-based composite oxide and the metal oxide of the raw material is uniformly mixed with a mixer or the like, and selected from fine Mg, Al, Ti, Zr and Zn on the particle surface of the lithium manganese nickel-based composite oxide. One or more metal oxides to be uniformly attached to the particle surface.

A 2nd process is a process of heat-processing the lithium manganese nickel system complex oxide with a metal oxide obtained at the said 1st process as it is, and obtaining a target modified lithium manganese nickel system complex oxide.

The heat treatment temperature is 300 to 600 ° C., preferably 400 to 500 ° C., and the heat treatment can be performed at 300 to 600 ° C. to allow the metal oxide to adhere more closely to the particle surface of the lithium manganese nickel-based composite oxide. . That is, it is thought that the energy of the surface of the metal oxide particle is reduced by this heat treatment, the surface of the metal oxide particle is smoothed, and the lithium manganese nickel-based composite oxide particles and the metal oxide particles are more accessible and the adhesion is increased. This can also be confirmed by the fact that the BET specific surface area is reduced by 3 to 15% after the heat treatment compared to before the heat treatment.

In the present invention, in particular, a lithium secondary battery having a modified lithium manganese nickel-based composite oxide obtained by heat treatment in the above temperature range as a positive electrode active material exhibits excellent cycle characteristics and coulombic efficiency. Moreover, heat processing time is 5 hours or more, Preferably it is 8 to 20 hours. Although the atmosphere of heat processing is not specifically limited, Usually, it is performed in air | atmosphere.

After completion of the second step, at least one metal oxide selected from Mg, Ti, Al, Zr, and Zn on the surface of the particles of the lithium manganese nickel-based composite oxide according to the present invention by appropriate cooling, pulverization and classification as necessary. The modified lithium manganese nickel-based composite oxide coated in an adhesive manner is obtained. In addition, grinding is suitably carried out when the modified lithium manganese nickel-based composite oxide is in the form of a weak block.

The modified lithium manganese nickel-based composite oxide of the present invention thus obtained can be suitably used as a positive electrode active material of a lithium secondary battery containing a nonaqueous electrolyte containing a positive electrode, a negative electrode, a separator and a lithium salt.

As the lithium secondary battery positive electrode active material according to the present invention, the modified lithium manganese nickel-based composite oxide is used. The positive electrode active material is a raw material of a positive electrode mixture of a lithium secondary battery described later, that is, a mixture containing a positive electrode active material, a conductive agent, a binder, a filler, and the like, as necessary. The lithium secondary battery positive electrode active material according to the present invention is the modified lithium manganese nickel-based composite oxide powder, by mixing with other raw materials to prepare a positive electrode mixture by using the one having a desirable particle size characteristics as described above Moreover, coating property at the time of apply | coating the obtained positive electrode mixture to a positive electrode electrical power collector becomes easy.

 The lithium secondary battery according to the present invention includes a nonaqueous electrolyte containing a positive electrode, a negative electrode, a separator and a lithium salt by using the lithium secondary battery positive electrode active material. The positive electrode is formed by, for example, coating and drying the positive electrode mixture on the positive electrode current collector, and the positive electrode mixture contains a positive electrode active material, a conductive agent, a binder, a filler added as necessary, and the like. In the lithium secondary battery according to the present invention, the modified lithium manganese nickel-based composite oxide, which is a positive electrode active material, is uniformly coated on a positive electrode. Therefore, especially in the lithium secondary battery according to the present invention, deterioration in load characteristics and cycle characteristics is unlikely to occur.

The positive electrode current collector is not particularly limited as long as it is an electron conductor that does not cause chemical change in the battery constituted. For example, carbon, nickel, titanium, silver may be applied to the surface of stainless steel, nickel, aluminum, titanium, calcined carbon, aluminum, or stainless steel. Surface-treated, etc. are mentioned. The surface of these materials may be oxidized, or may be used by adhering irregularities to the surface of the current collector by surface treatment. Moreover, as a form of an electrical power collector, a foil, a film, a sheet, a net, a punched thing, a lath body, a porous body, a foam, a fiber group, the molded object of a nonwoven fabric, etc. are mentioned, for example. Although the thickness of an electrical power collector is not specifically limited, It is preferable to set it as 1-500 micrometers.

The conductive agent is not particularly limited as long as it is an electron conductive material which does not cause chemical change in the battery configured. For example, graphite such as natural graphite and artificial graphite, carbon black such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, conductive fibers such as carbon fiber or metal fiber, fluoride Metal powders such as carbon, aluminum, nickel powder and the like, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide, or conductive materials such as polyphenylene derivatives, and the like, and natural graphite, For example, scaly graphite, scaly graphite, soil graphite, etc. are mentioned. These can be used 1 type or in combination or 2 or more types. The blending ratio of the conductive agent is 1 to 50% by weight, preferably 2 to 30% by weight in the positive electrode mixture.

As the binder, for example, starch, polyvinylidene fluoride, polyvinyl alcohol, carboxymetal cellulose, hydroxypropyl cellulose, regenerated cellulose, diacetyl cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, Ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrenebutadiene rubber, fluororubber, tetrafluoroethylene-hexafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene Perfluoroalkyl vinyl ether copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer, polychlorotrifluoroethylene, fluoride Vinylidene-pentafluoropropylene copolymer, propylene-tetrafluoroethylene ball Copolymer, ethylene-chlorotrifluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethylvinylether-tetrafluoroethylene copolymer, ethylene-acrylic acid Copolymer or (Na ⁺ ) ion crosslinker, ethylene-methacrylic acid copolymer or (Na ⁺ ) ion crosslinker, ethylene-methyl acrylate copolymer or (Na ⁺ ) ion crosslinker thereof, ethylene-methacrylic acid Polysaccharides, such as a methyl copolymer or its (Na ⁺ ) ion crosslinked body, polyethylene oxide, a thermoplastic resin, a polymer which has rubber elasticity, etc. are mentioned, These can be used 1 type or in combination of 2 or more types. In addition, when using the compound containing a functional group, such as reacting with lithium like a polysaccharide, it is preferable to add a compound, such as an isocyanate group, and inactivate the functional group. The blending ratio of the binder is 1 to 50% by weight, preferably 5 to 15% by weight in the positive electrode mixture.

A filler suppresses the volume expansion of a positive electrode, etc. in positive mix and is added as needed. Any filler may be used as long as it is a fibrous material which does not cause chemical change in the battery constituted. For example, an olefin polymer such as polypropylene, polyethylene or the like, or fiber such as glass or carbon is used. Although the addition amount of a filler is not specifically limited, 0-30 weight% is preferable in positive mix.

The negative electrode is formed on the negative electrode current collector by coating and drying of the negative electrode material. The negative electrode current collector is not particularly limited as long as it is an electron conductor that does not cause chemical change in a battery composed of, for example, carbon, nickel, titanium on the surface of stainless steel, nickel, copper, titanium, aluminum, calcined carbon, copper, or stainless steel. And the surface-treated silver, aluminum-cadmium alloy, etc. are mentioned. Moreover, the surface of these materials may be oxidized and used, and unevenness may be adhere | attached on the surface of an electrical power collector by surface treatment. Moreover, as a form of an electrical power collector, a foil, a film, a sheet, a net, a punched thing, a lath body, a porous body, a foam, a fiber group, the molded object of a nonwoven fabric, etc. are mentioned, for example. Although the thickness of an electrical power collector is not specifically limited, It is preferable to set it as 1-500 micrometers.

Although it does not restrict | limit especially as a negative electrode material, For example, a carbonaceous material, a metal complex oxide, lithium metal, a lithium alloy, a silicon type alloy, a tin type alloy, a metal oxide, a conductive polymer, a chalcogen compound, a Li-Co-Ni type material Etc. can be mentioned. Examples of the carbonaceous material include hardly graphitized carbon materials and graphite carbon materials. Metal composite oxides include, for example, ^{_{Sn p M 1 l - p M}} 2 q O r ( wherein, M ¹ represents at least one element selected from Mn, Fe, Pb, and Ge, M ² is Al, B , P, Si, at least one element selected from group 1, 2, 3, and halogen of the periodic table, and represents 0 <p ≦ 1, 1 ≦ q ≦ 3, 1 ≦ r ≦ 8) , Li _x Fe ₂ O ₃ (0 ≦ x ≦ 1), Li _x WO ₂ (0 ≦ x ≦ 1), and the like. Metal oxides include GeO, GeO ₂ , SnO, SnO ₂ , PbO, PbO ₂ , Pb ₂ O ₃ , Pb ₃ O ₄ , Sb ₂ O ₃ , Sb ₂ O ₄ , Sb ₂ O ₅ , Bi ₂ O ₃ , Bi ₂ O _4, and the like Bi ₂ O _5. Examples of the conductive polymer include polyacetylene and poly-p-phenylene.

As the separator, an insulating thin film having a large ion permeability and a predetermined mechanical strength is used. Due to the organic solvent resistance and hydrophobicity, sheets or nonwovens made from olefinic polymers such as polypropylene or glass fibers or polyethylene are used. As a pore size of the separator, generally useful range for a battery is used, for example, 0.01 to 10 mu m. As thickness of a separator, what is necessary is just the range for general batteries, for example, 5-300 micrometers. In addition, when a solid electrolyte, such as a polymer, is used as the electrolyte to be described later, the solid electrolyte may also serve as a separator.

The nonaqueous electrolyte containing a lithium salt includes a nonaqueous electrolyte and a lithium salt. As the nonaqueous electrolyte, a nonaqueous electrolyte, an organic solid electrolyte, and an inorganic solid electrolyte are used. As the nonaqueous electrolyte, for example, N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone , 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate , Methyl acetate, phosphate triester, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone, propylene carbo The solvent which mixed 1 type, or 2 or more types of an aprotic organic solvent, such as a nate derivative, tetrahydrofuran derivative, diethyl ether, 1, 3- propane sultone, methyl propionate, ethyl propionate, is mentioned.

As the organic solid electrolyte, for example, a polyethylene derivative, a polyethylene oxide derivative or a polymer containing the same, a polypropylene oxide derivative or a polymer containing the same, a phosphate ester polymer, polyphosphazene, polyaziridine, polyethylene sulfide, polyvinyl Polymers containing ionic dissociating groups such as alcohols, polyvinylidene fluoride, polyhexafluoropropylene, and the like, polymers containing ionic dissociating groups, and mixtures of the above non-aqueous electrolytes.

An inorganic solid electrolyte used may be a nitride, halide, oxygen acid salts of Li, for example, _{Li 3 N, LiI, Li 5} NI 2, Li 3 N-LiI-LiOH, LiSiO 4, LiSiO 4 -LiI- LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Li ₄ SiO ₄ -LiI-LiOH, Li ₃ PO ₄ -Li ₂ S-SiS ₂ , phosphorus sulfide compounds, and the like.

As the lithium salt, those dissolved in the nonaqueous electrolyte are used, for example, LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB ₁₀ Cl ₁₀ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiB ₁₀ Cl ₁₀ , LiAlCl ₄ , CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, (CF ₃ SO ₂ ) ₂ NLi, chloroborane lithium, lower aliphatic lithium carboxylate, lithium tetraphenylborate, imides, etc. The salt which mixed the same 1 type, or 2 or more types is mentioned.

 In addition, the compound shown below can be added to a nonaqueous electrolyte in order to improve discharge, a charging characteristic, and a flame retardance. For example, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, n-lime, hexaphosphate triamide, nitrobenzene derivative, sulfur, quinoneimine dye, N-substituted oxazolidinone and N, N -Substituted imidazolysin, ethylene glycol dialkyl ether, ammonium salt, polyethylene glycol, pyrrole, 2-methoxyethanol, aluminum trichloride, monomer of conductive polymer-electrode active material, triethylenephosphonamide, trialkylphosphine Aryl compounds having a morpholine, carbonyl group, hexamethylphosphoryriamide and 4-alkyl morpholine, bicyclic tertiary amines, oils, phosphonium salts and tertiary sulfonium salts, phosphazenes, carbonate esters, and the like. have. In addition, a halogen-containing solvent such as carbon tetrachloride and ethylene trifluoride may be included in the electrolyte to render the electrolyte nonflammable. In addition, in order to make it suitable for high temperature storage, carbon dioxide gas may be included in electrolyte solution.

The lithium secondary battery according to the present invention is a lithium secondary battery excellent in battery performance, particularly cycle characteristics and coulombic efficiency. The shape of the battery may be any shape such as a button, a sheet, a cylinder, a square, or a coin. Although the use of the lithium secondary battery according to the present invention is not particularly limited, for example, a notebook, a laptop personal computer, a pocket word processor, a mobile phone, a wireless handset, a portable CD player, a radio, a liquid crystal television, a backup power supply, an electric shaver, Electronic devices such as memory cards, video movies, and the like, and civilian electronic devices such as automobiles, electric vehicles, and game devices.

<Example>

<Complex Oxide Sample>

(a) Process for preparing starting material

300 ml of an aqueous mixed salt solution (volume ratio 1: 1) of 0.4 mol / l NiSO ₄ .6H ₂ O and 1.2 mol / l MnSO ₄ .5H ₂ O was prepared. Separately, 100 ml of an aqueous 1.5 mol / l ammonia solution and 200 ml of a 6 mol / l NaOH aqueous solution were prepared as complexing agents. These three aqueous solutions were simultaneously added to a 1 L beaker containing 200 mL of water. During the dropping, the dropping rate of each aqueous solution was adjusted so that the pH of the reaction solution was 11. The dropping rate was 60 ml / min for an aqueous mixed salt solution, 20 ml / min for an aqueous ammonia solution and 40 ml / min for an NaOH aqueous solution. The reaction solution was maintained at 50 ° C. Thus, the hydroxides of Mn and Ni were co-precipitated. The coprecipitate was aged by stirring for 9 hours. In the meantime, the amount of liquid in the reaction system was controlled in an overflow manner to replace the overflowed liquid every three hours. After filtration, the precipitated hydroxide was repulsed. The cleaning was sufficiently performed while the conductivity meter judged the cleaning effect. After drying, X-ray diffraction of the precipitated product was performed. As a result, confirmed that the amorphous precipitated product is not Mn and Ni are each ball and jams (共晶體) of the solid solution of Mn and Ni, the composition is substantially represented by _{Mn 0 .75 Ni 0 .25 (OH} ) 2 It became. The BET specific surface area of this precipitated product was 12.2 m 2 / g and the average particle diameter was 9.7 μm.

(b) Step 1 heat treatment process

The starting material obtained in the step (a) was heat-treated at 1000 ° C. for 12 hours in the air to obtain a first precursor. The temperature increase rate until reaching the maximum temperature range was 100 degreeC / hour. The first precursor was naturally cooled to room temperature (20 ° C.). Temperature-fall rate was 100 degreeC / hour. After cooling, it was ground lightly using a domestic mixer. The BET specific surface area of the first precursor was 0.43 m 2 / g.

(c) second stage heat treatment process

Subsequently, the first precursor obtained in the step (b) was heat treated at 650 ° C. for 10 hours in the air to obtain a second precursor. The temperature increase rate until reaching the maximum temperature range was 100 degreeC / hour. After heat processing, it cooled to room temperature (20 degreeC) at the temperature-fall rate of 100 degreeC / hour. The BET specific surface area of the obtained second precursor was 0.41 m 2 / g.

(d) Liification firing process

The second precursor obtained in the step (c) and lithium carbonate were mixed dry. Mixing was performed so that the ratio (the former / the latter) of the total number of moles of lithium and the number of moles of Mn and Ni would be 0.5. Then, it was calcined at 900 ° C for 12 hours in the air. The temperature increase rate until reaching the maximum temperature range was 100 degreeC / hour. After baking, it cooled to room temperature (20 degreeC) by 100 degreeC / hour of temperature-fall rates. Then, it was ground using a domestic mixer. It was confirmed that the composition of the obtained lithium manganese nickel composite oxide was almost expressed as LiMn _1.5 Ni _0.5 O ₄ . The BET specific surface area of this composite oxide was 0.39 m 2 / g, and the average particle diameter was 10.5 m.

(e) heat treatment

Subsequently, the lithium manganese nickel composite oxide obtained by the process of (d) was heat-processed at 600 degreeC for 5 hours in air | atmosphere (after-heating process). The temperature increase rate until reaching the maximum temperature range was 100 degreeC / hour. After the post-heating treatment, the mixture was cooled to room temperature (20 ° C) at a temperature-fall rate of 100 ° C / hour. It was confirmed that the composition of the obtained lithium manganese nickel composite oxide was almost expressed as LiMn _1.5 Ni _0.5 O ₄ . The BET specific surface area of this composite oxide was 0.38 m 2 / g, and the average particle diameter was 10.6 µm.

Moreover, it was 98 ppm when the manganese elution amount of the lithium manganese nickel system complex oxide was measured with the following method.

[Manganese Elution]

1 g of lithium manganese nickel composite oxide was placed in a sealable Teflon® container. The vessel was placed in a vacuum dryer heated to 120 ° C. overnight to remove moisture. After the container was extracted from the vacuum dryer, 5 g of electrolyte was placed in a Teflon (registered trademark) container under a dry air atmosphere to cover the container. The electrolyte solution was obtained by dissolving 1 mol of LiPF _{6 in} 1 liter of a volume ratio 1: 2 mixture of ethylene carbonate and diethyl carbonate. The container was shaken up and down to completely mix the composite oxide and the electrolyte solution, and then the container was placed in a constant temperature bath at 80 ° C. and left for one week. In the meantime, the container was shaken once every 2-3 days, and both were mixed. After one week, the vessel was extracted from the thermostat and the electrolyte in the vessel was filtered with a 0.1 μm filter. 1 g of the filtrate was placed in a 100 ml volumetric flask, and a mixed solvent of ultrapure water: ethanol = 80: 20 (weight ratio) was added to the volumetric flask, and the mixture was diluted. After shaking the measuring flask well, the concentration of Mn was uniformed by atomic absorption spectrometry. Based on the quantitative value, the amount of Mn dissolved in 5 g of electrolyte solution was calculated, and the elution amount was computed.

 <Metal Oxide Sample>

Metal oxide samples were used having various materials shown in Table 1 below.

Note) MgO; Ube Materials, Inc., Al ₂ O ₃ ; Showa Denko Co., Ltd., TiO ₂ ; Showa Titanium Corporation

<Example 1>

(First process)

Each metal oxide was attached to the surface of the particles of LiMn _1.5 Ni _0.5 O ₄ by sufficiently mixing 60 g of each of the LiMn _1.5 Ni _0.5 O ₄ and 1 g of the metal oxide prepared above for 60 seconds using a domestic mixer. In addition, the BET specific surface area after the first step was measured, and the results are shown in Table 2 below.

(Second process)

Subsequently, heat treatment was performed at 500 ° C. for 5 hours in an alumina furnace. After cooling, pulverization and classification were performed to obtain a modified lithium manganese nickel-based composite oxide. Table 2 shows the various materials of the obtained modified lithium manganese nickel-based composite oxide. In addition, electron micrographs of the modified lithium manganese nickel-based composite oxides obtained in Examples 1 and 2 are shown in FIGS. 1 and 2. In addition, the amount of manganese elution was measured as described above. As a result, the amount of manganese elution was 78 ppm, 86 ppm and 91 ppm, respectively.

Reference Example 1

The lithium manganese nickel composite oxide which was not subjected to the coating treatment prepared above was used as a reference sample.

(Performance evaluation)

A lithium secondary battery was manufactured using the modified lithium manganese nickel-based composite oxide obtained in the examples and the lithium manganese nickel-based composite oxide of Reference Example 1 as the positive electrode active material. About this battery, the initial discharge capacity, the coulombic efficiency of the 10th cycle, and the discharge capacity ratio of 5V area / 5V and 4V area were measured with the following method. These results are shown in Table 3 below. In addition, the initial discharge capacity curves for Examples 1 to 3 are shown in Figs. 3, 4 and 5, respectively.

 [Initial discharge capacity]

5.7 g of lithium manganese nickel composite oxide, 0.15 g of a conductive agent (conductive carbon, Super P manufactured by Erachem Co., Ltd.), and 0.15 g of a binder (polyvinylidene fluoride) were mixed. Subsequently, about 5 ml of N-methylpyrrolidinone was added to prepare a uniform paint with a stirrer. The coating material was apply | coated to the sheet | seat made from aluminum, and it dried for 2 hours at 120 degreeC, and obtained the positive electrode sheet. Coating thickness was 120 micrometers. After compressing the positive electrode sheet, it was punched to a size of φ 15 mm to obtain a positive electrode plate. Using this positive electrode plate, a lithium secondary battery was manufactured using each member such as a separator, a negative electrode, a current collector plate, a metal fitting, an external terminal, and an electrolyte solution. A negative electrode include metallic lithium foil, electrolyte solution is ethylene carbonate and diethyl carbonate in a volume ratio of 1: was used by dissolving LiPF ₆ 1 mol to 2 mixture 1 ℓ. The initial discharge capacity was measured at 25 ° C. for this lithium secondary battery. Charging was performed at CCCV (current is charged at the current value of 0.05 C) to 5.0 V at a current value of 0.5 C, and discharge was performed at CC at a current value of 0.2 C to 3.0 V.

[Coulomb efficiency of the tenth cycle]

Discharge capacity of the 10th cycle and the charge capacity of the 10th cycle were measured about the lithium secondary battery used for the measurement of the initial discharge capacity mentioned above, and it is 10 cycles from the discharge capacity of 10th cycle / 10th charge capacity * 100 Coulomb efficiency of was calculated.

[Discharge capacity ratio in 5 V region / 5 V and 4 V region]

Charge and discharge up to 20 cycles are repeated for the lithium secondary battery used for the measurement of the initial discharge capacity described above, and the discharge capacity at 4.6 to 4.7 V (discharge capacity at 5 V region) and discharge capacity at 3.9 to 4.1 V ( Discharge capacity in the 4 V region). The discharge capacity ratio was calculated from the discharge capacity in the 5 V region / (discharge capacity in the 5 V region + discharge capacity in the 4 V region) × 100.

From the results in Table 3, it was found that the coulombic efficiency and the discharge capacity ratio in the 5 V region / 5 V and 4 V region were improved. 3, 4, and 5 also show that the cycle characteristics are excellent in that the deterioration of the charge / discharge curve is small.

In the modified lithium manganese nickel-based composite oxide of the present invention, elution of manganese ions is suppressed, and a lithium secondary battery using the modified lithium manganese nickel-based composite oxide as a positive electrode active material exhibits excellent cycle characteristics and coulombic efficiency.

Claims (13)

Particle surface of the lithium manganese nickel-based composite oxide represented by the formula (1) is coated with a metal oxide containing at least one metal element selected from Mg, Al, Ti, Zr and Zn modified lithium manganese Nickel-based composite oxides.  <Formula 1> Li _x Mn _1.5 Ni _0.5 O _4-w In the formula, 0 <x <2, 0 ≦ w <2. The method according to claim 1, wherein the lithium manganese nickel-based composite oxide and one or two or more metal oxides of a compound containing at least one metal element selected from Mg, Al, Ti, Zr, and Zn are dry mixed, Next, the modified lithium manganese nickel-based composite oxide, which is obtained by heat treatment. The modified lithium manganese nickel-based composite oxide according to claim 1 or 2, wherein the coating amount of the metal oxide is 0.05 to 1% by weight. The modified lithium manganese nickel-based composite oxide according to any one of claims 1 to 3, wherein the BET specific surface area is 0.3 to 1.0 m 2 / g. 2 g of a modified lithium manganese nickel-based composite oxide is added to 5 g of an electrolyte solution in which 1 mol / L of LiPF ₆ is dissolved in a mixed solution of ethylene carbonate and diethyl carbonate in a volume ratio of 1: 2. A modified lithium manganese nickel-based composite oxide, characterized in that the amount of Mn dissolved in the electrolyte after 100 hours at 80 ° C. is 100 ppm or less. The modified lithium manganese nickel-based composite oxide according to claim 1, wherein the at least one metal element is at least one metal element selected from Mg, Al, and Ti. First process; Lithium manganese nickel-based composite oxide represented by the formula (1) and one or two or more metal oxides of a compound containing at least one metal element selected from Mg, Al, Ti, Zr and Zn by dry mixing the composite Attaching the particles of the metal oxide to the particle surface of the oxide, and  Second process; A method for producing a modified lithium manganese nickel-based composite oxide, comprising the step of heating the composite oxide with a metal oxide obtained in the first step to obtain a modified lithium manganese-based composite oxide.  <Formula 1> _{Li x Mn 1 .5 Ni 0 .5} O 4 -w (In formula, 0 <x <2 and 0 <w <2.) 8. The lithium manganese nickel-based composite oxide of the first step is prepared by using a manganese and nickel complex compound or a mixture of a manganese compound and a nickel compound as a starting material. 1 precursor was formed, the first precursor was cooled, and then heated to 550 to 750 ° C. to form a second precursor, and after cooling the second precursor, it was mixed with a lithium compound to be baked at 800 to 1000 ° C. Method for producing a modified lithium manganese nickel-based composite oxide, characterized in that. The method of claim 8, wherein the lithium manganese nickel-based composite oxide of the first step is heated to 550 to 650 ° C after cooling the lithium manganese nickel-based composite oxide obtained by mixing and baking the second precursor and the lithium compound. A process for producing a modified lithium manganese nickel-based composite oxide, which is obtained by treatment. The manufacturing method of the modified lithium manganese nickel complex oxide of any one of Claims 7-9 whose average particle diameter of the metal oxide used at a said 1st process is 1.0 micrometer or less. The method for producing a modified lithium manganese nickel-based composite oxide according to any one of claims 7 to 10, wherein the heat treatment of the second step is performed at 300 to 600 ° C. A lithium secondary battery positive electrode active material comprising the modified lithium manganese nickel-based composite oxide according to any one of claims 1 to 6. The lithium secondary battery positive electrode active material of Claim 12 is used, The lithium secondary battery characterized by the above-mentioned.

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