KR102413743B1 - Manufacturing method of positive electrode active material for lithium secondary battery - Google Patents

Abstract

This method for producing a positive electrode active material for a lithium secondary battery is a method for producing a positive electrode active material for a lithium secondary battery containing a lithium composite metal compound, heating a composite metal compound powder containing nickel, cobalt, and manganese, and dissolving a tungsten compound A spray mixing process comprising spraying an alkali solution on the composite metal compound powder, mixing the composite metal compound powder and the tungsten compound to prepare a mixed powder, and then cooling the mixed powder; and mixing and calcining the mixed powder to prepare a lithium composite metal compound.

Description

Manufacturing method of positive electrode active material for lithium secondary battery

The present invention relates to a method for producing a positive electrode active material for a lithium secondary battery.

This application claims priority based on Japanese Patent Application No. 2016-237694 for which it applied to Japan on December 7, 2016, and uses the content here.

A lithium composite oxide is used as a positive electrode active material for lithium secondary batteries. Lithium secondary batteries have already been put into practical use not only in small power supplies for mobile phone applications and notebook computers, but also in medium-sized and large-sized power sources such as automobile applications and power storage applications.

In order to improve the performance of lithium secondary batteries, such as battery capacity, the lithium composite metal compound containing lithium, nickel, cobalt, and manganese is used for the positive electrode active material for lithium secondary batteries. In addition, in order to achieve lower resistance and longer life of the battery, it is useful to contain tungsten in the positive electrode active material for a lithium secondary battery. For example, Patent Document 1 describes a technique of adding an alkali solution in which a tungsten compound is dissolved after the primary firing of the lithium composite metal compound. In addition, Patent Document 2 describes a method of dry adding tungsten oxide to a precursor of a lithium composite metal compound. Moreover, in patent document 3, the method of preparing the slurry solution containing the precursor of a lithium composite metal compound, and tungsten oxide, and spray-drying this slurry solution is described.

Japanese Patent Laid-Open No. 2012-79464 Japanese Laid-Open Patent Publication No. 2014-197556 Japanese Patent Laid-Open No. 2011-228292

In order to achieve low-resistance and long-life of a battery, it is useful to contain tungsten in the positive electrode active material for lithium secondary batteries. However, in the method of patent documents 1-3, when tungsten is added, there exists a subject that tungsten aggregates and segregates, and the foreign material derived from tungsten will generate|occur|produce.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing a positive electrode active material for a lithium secondary battery in which segregation of tungsten is suppressed.

That is, the present invention includes the following inventions [1] to [6].

[1] A method for producing a positive electrode active material for a lithium secondary battery containing a lithium composite metal compound, wherein the composite metal compound powder containing nickel, cobalt, and manganese is heated, and an alkali solution in which a tungsten compound is dissolved is added to the composite metal compound powder and mixing the composite metal compound powder and the tungsten compound to prepare a mixed powder, and then a spray mixing process comprising cooling the mixed powder, lithium salt and the mixed powder, , a method for producing a positive electrode active material for a lithium secondary battery having a step of producing a lithium composite metal compound by firing.

[2] The method for producing a positive electrode active material for a lithium secondary battery according to [1], wherein the lithium composite metal compound is represented by the following compositional formula (I).

Li[Lix(Ni(1 - y - z - w)CoyMnzMw)1 -x]O ₂ ... (I)

(In formula (I), -0.1 ≤ x ≤ 0.2, 0 < y ≤ 0.5, 0 < z ≤ 0.8, 0 ≤ w ≤ 0.1, y + z + w < 1, M is Fe, Cu, Ti, Mg, At least one metal selected from the group consisting of Al, W, B, Mo, Nb, Zn, Sn, Zr, Ga and V is represented.)

[3] The method for producing a positive electrode active material for a lithium secondary battery according to [1] or [2], wherein the content of tungsten contained in the positive electrode active material for a lithium secondary battery is 1.0 mol% or less with respect to the total molar amount of the transition metal.

[4] The method for producing a positive electrode active material for a lithium secondary battery according to any one of [1] to [3], wherein in the spray mixing step, the tungsten compound is tungsten oxide.

[5] The method for producing a positive electrode active material for a lithium secondary battery according to any one of [1] to [4], wherein in the spray mixing step, the alkali solution contains lithium hydroxide.

[6] The method for producing a positive electrode active material for a lithium secondary battery according to any one of [1] to [5], wherein in the spray mixing step, the temperature of the composite metal compound powder at the time of spraying the alkali solution is 100° C. or higher.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the positive electrode active material for lithium secondary batteries by which segregation of tungsten was suppressed can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic structural diagram which shows an example of a lithium ion secondary battery.
It is a schematic structural diagram which shows an example of a lithium ion secondary battery.
Fig. 2 is an SEM image of the mixed powder of Comparative Example 2 after dry mixing.
Fig. 3 is an SEM image of the mixed powder of Example 3 after spray mixing.

<The manufacturing method of the positive electrode active material for lithium secondary batteries>

In the manufacturing method of the positive electrode active material for lithium secondary batteries of this embodiment, heating the composite metal compound powder containing nickel, cobalt and manganese, and spraying the alkali solution in which the tungsten compound was dissolved to the composite metal compound powder, the said composite A spray mixing process comprising mixing the metal compound powder and the tungsten compound to prepare a mixed powder, and then cooling the mixed powder, a lithium salt and the mixture powder are mixed and fired to form a lithium composite metal It has a process for preparing the compound.

In the manufacturing method of the positive electrode active material for lithium secondary batteries, first, metals other than lithium, ie, essential metals comprised from Ni, Co and Mn, and Fe, Cr, Cu, Ti, B, Mg, Al, W, Mo , Nb, Zn, Sn, Zr, Ga and V, it is preferable to prepare a composite metal compound containing any one or more arbitrary metals, and to calcinate the composite metal compound with an appropriate lithium salt. As the composite metal compound, a composite metal hydroxide or a composite metal oxide is preferable.

In more detail, the manufacturing method of the positive electrode active material for lithium secondary batteries of this embodiment is equipped with the manufacturing process of the composite metal compound which has the said spray mixing process, and the manufacturing process of a lithium metal composite oxide.

Hereinafter, each process of the manufacturing method of the positive electrode active material for lithium secondary batteries of this embodiment is demonstrated.

[Manufacturing process of composite metal compound]

The manufacturing process of the composite metal compound is a metal other than lithium, that is, an essential metal composed of Ni, Co and Mn, and Fe, Cr, Cu, Ti, B, Mg, Al, W, Mo, Nb, Zn, It is a process of preparing the composite metal compound containing any 1 or more types of arbitrary metals of Sn, Zr, Ga, and V.

The composite metal compound can be produced by a conventionally known batch co-precipitation method or continuous co-precipitation method. Hereinafter, a composite metal hydroxide containing nickel, cobalt, and manganese as a metal is taken as an example, and a manufacturing method thereof will be described in detail.

First, a nickel salt solution, a cobalt salt solution, a manganese salt solution, and a complexing agent are reacted by a co-precipitation method, particularly the continuous method described in Japanese Patent Application Laid-Open No. 2002-201028, to react Ni _x Co _y Mn _z (OH) ₂ A composite metal hydroxide represented by (wherein, x + y + z = 1) is prepared.

Although it does not specifically limit as a nickel salt which is a solute of the said nickel salt solution, For example, any of nickel sulfate, nickel nitrate, nickel chloride, and nickel acetate can be used. As a cobalt salt which is a solute of the said cobalt salt solution, for example, any one of cobalt sulfate, cobalt nitrate, and cobalt chloride can be used. As the manganese salt that is the solute of the manganese salt solution, for example, any one of manganese sulfate, manganese nitrate, and manganese chloride can be used. The above metal salt is used in a proportion corresponding to the composition ratio of Ni _x Co _y Mn _z (OH) ₂ . That is, the quantity of each metal salt is prescribed|regulated so that the molar ratio of nickel, cobalt, and manganese in the mixed solution containing the said metal salt may become x:y:z. Moreover, water is used as a solvent.

The complexing agent is one capable of forming a complex with ions of nickel, cobalt and manganese in aqueous solution, for example, an ammonium ion supplier (ammonium sulfate, ammonium chloride, ammonium carbonate, ammonium fluoride, etc.), hydrazine, ethylenediaminetetraacetic acid, nitrilotriacetic acid, uracildiacetic acid and glycine.

The complexing agent does not need to be contained, and when the complexing agent is contained, the amount of the complexing agent contained in the nickel salt solution, the cobalt salt solution, the manganese salt solution, and the mixed solution containing the complexing agent is, for example, the amount of the complexing agent relative to the sum of the moles of the metal salts. The molar ratio is greater than 0 and less than or equal to 2.0.

At the time of precipitation, an alkali metal hydroxide (for example, sodium hydroxide, potassium hydroxide) is added if necessary in order to adjust the pH value of the aqueous solution.

In addition to the nickel salt solution, the cobalt salt solution, and the manganese salt solution, when a complexing agent is continuously supplied to the reaction tank, nickel, cobalt, and manganese react to produce Ni _x Co _y Mn _z (OH) ₂ . At the time of reaction, the temperature of a reaction tank is 20 degreeC or more and 80 degrees C or less, for example, Preferably it is controlled within the range of 30-70 degreeC. The pH value (at the time of 40 degreeC measurement) in a reaction tank is controlled within the range of pH 9 or more and pH 13 or less, Preferably it is pH 11-13. The material in the reaction vessel is properly stirred.

An inert atmosphere may be sufficient as the inside of a reaction tank. In an inert atmosphere, it is possible to suppress aggregation of elements that are more easily oxidized than nickel, and a uniform composite metal hydroxide can be obtained.

Moreover, an appropriate oxygen-containing atmosphere or an oxidizing agent may be present while maintaining an inert atmosphere in the reaction tank. By appropriately oxidizing the transition metal, it becomes possible to control the shape of the composite metal hydroxide, and to control the size and degree of dispersion of the pores inside the secondary particles in the positive electrode material produced using the composite metal hydroxide. At this time, oxygen and the oxidizing agent in the oxygen-containing gas may have sufficient oxygen atoms to oxidize the transition metal. By introducing an appropriate oxygen atom into the reaction tank, an inert atmosphere in the reaction tank can be maintained.

In order to make the inside of a reaction tank into an oxygen-containing atmosphere, what is necessary is just to introduce|transduce oxygen-containing gas into a reaction tank. It is preferable that the oxygen concentration (vol%) with respect to the volume of the oxygen-containing gas in the oxygen-containing gas is 1 or more and 15 or less. In order to improve the uniformity of the solution in the reaction tank, the oxygen-containing gas may be bubbled. Examples of the oxygen-containing gas include oxygen gas, air, or a mixed gas of these and non-oxygen gas such as nitrogen gas. From a viewpoint of being easy to adjust the oxygen concentration in oxygen-containing gas, it is preferable that it is a mixed gas among the above.

In order to make the inside of a reaction tank into presence of an oxidizing agent, what is necessary is just to add an oxidizing agent to the inside of a reaction tank. Examples of the oxidizing agent include hydrogen peroxide, chlorate, hypochlorite, perchlorate, and permanganate. Hydrogen peroxide is preferably used from a viewpoint that it is difficult to bring in impurities into the reaction system.

After the above reaction, the obtained reaction precipitate is washed with water and dried to isolate nickel-cobalt-manganese hydroxide as a composite metal compound containing nickel, cobalt and manganese. Moreover, you may wash|clean with weak acid water or the alkaline solution containing sodium hydroxide or potassium hydroxide as needed. In addition, although the nickel-cobalt-manganese composite hydroxide is manufactured in the above-mentioned example, a nickel-cobalt-manganese composite oxide may be prepared. When preparing the nickel-cobalt-manganese composite oxide, for example, a step of contacting the coprecipitate slurry with an oxidizing agent or a step of heat-treating the nickel-cobalt-manganese composite hydroxide may be performed.

The BET specific surface area of the obtained powder of the composite metal compound containing nickel, cobalt and manganese is preferably 15 to 90 m 2 /g, and the average particle diameter is preferably 2.0 to 15 µm.

Here, as for the BET specific surface area, after drying 1 g of a powder of a complex metal compound containing nickel, cobalt and manganese at 105° C. for 30 minutes in a nitrogen atmosphere, a BET specific surface area meter (Macsorb (registered trademark) manufactured by Mountec Co., Ltd.) was measured. It is a value measured using

In addition, an average particle diameter is a value measured by the following method. Using a laser diffraction particle size distribution analyzer (manufactured by Horiba Corporation, LA-950), 0.1 g of a composite metal compound powder containing nickel, cobalt, and manganese was put into 50 ml of a 0.2 mass% sodium hexametaphosphate aqueous solution, and the powder to obtain a dispersion in which The particle size distribution of the obtained dispersion is measured to obtain a volume-based cumulative particle size distribution curve. In the obtained cumulative particle size distribution curve, the particle diameter (D ₅₀ ) seen from the microparticle side at the time of 50% accumulation Let the value of is the average particle diameter of the composite metal compound containing nickel, cobalt, and manganese.

· Spray mixing process

In the spray mixing step, the composite metal compound powder containing nickel, cobalt and manganese obtained in the above step is heated, and an alkali solution in which the tungsten compound is dissolved is sprayed onto the composite metal compound powder to form the composite metal compound powder and the tungsten compound. Mix to prepare a mixed powder. After that, the mixed powder is cooled.

In the spray mixing process, a tungsten compound is dissolved in an alkali solution. The dissolution method is not specifically limited, For example, what is necessary is just to add and dissolve a tungsten compound while stirring a solution using the reaction tank with a stirring device. From a viewpoint of suppressing generation|occurrence|production of the foreign material derived from tungsten, it is preferable to melt|dissolve a tungsten compound completely in an alkali solution, and to disperse|distribute it uniformly.

When a tungsten-derived foreign material in this specification is added to a composite metal compound, a tungsten compound is segregated and it is a tungsten aggregate which generate|occur|produces.

It is preferable that it is 0.5-15 mass % with respect to the alkali solution whole mass, and, as for the density|concentration of the tungsten compound in an alkali solution, it is more preferable that it is 2.0-6.0 mass %. When the concentration of the tungsten compound is 15% by mass or more, there is a possibility that a dissolved residue of the tungsten compound is generated. When the concentration of the tungsten compound is 15% by mass or less, the tungsten compound can be completely dissolved in an alkali solution and uniformly dispersed.

Next, the composite metal compound powder containing nickel, cobalt and manganese obtained in the above process is heated, and an alkali solution in which a tungsten compound is dissolved is sprayed onto the composite metal compound powder, and the composite containing nickel, cobalt and manganese A mixed powder is prepared by mixing the metal compound powder and the tungsten compound. That is, while heating and stirring the composite metal compound powder containing nickel, cobalt and manganese obtained in the above process, an alkali solution in which a tungsten compound is dissolved is sprayed onto the composite metal compound powder, and the nickel, cobalt and manganese containing A mixed powder is prepared by mixing the composite metal compound powder and the tungsten compound.

It is preferable to heat the composite metal compound powder to a temperature higher than the temperature at which the solvent of the alkali solution evaporates. Specifically, the temperature at which the composite metal compound powder is heated is appropriately set according to the boiling point of the solvent of the alkali solution contained in the alkali solution and the spraying conditions of the alkali solution.

More specifically, the lower limit of the temperature of the composite metal compound powder is preferably 100°C or higher, and more preferably 105°C or higher. The upper limit of the temperature of the composite metal compound powder is not particularly limited, and examples thereof include 150°C or less, 130°C or less, and 120°C or less.

The above upper limit and lower limit may be arbitrarily combined. For example, 100 degreeC or more and 150 degrees C or less are preferable, and, as for the temperature of composite metal compound powder, 105 degreeC or more and 150 degrees C or less are more preferable.

In a spray mixing process, the alkali solution which melt|dissolved the tungsten compound is sprayed to the heated composite metal compound powder, and a composite metal compound and a tungsten compound are mixed. The supply amount (L/min), the discharge pressure (MPa), the nozzle diameter of the nozzle which discharges the alkali solution at the time of spraying of an alkali solution, etc. are suitably set according to the specification of the heating spraying apparatus to be used, etc.

For example, the supply amount at the time of spraying of the alkali solution is 1.0 to 3.0 L/h, the discharge pressure is 0.05 MPa to 1.0 MPa, the nozzle diameter is 30 to 200 μm, and it is preferable to spray and mix for about 10 minutes to 600 minutes. .

Moreover, it is preferable that the temperature of the alkali solution in a spraying process is 20-90 degreeC.

The tungsten compound used in the spray mixing process will not be specifically limited if it is soluble with respect to an alkali solution, Tungsten oxide, ammonium tungstate, sodium tungstate, and lithium tungstate can be used. In this embodiment, it is especially preferable to use tungsten oxide.

In a spray mixing process, an above-described tungsten compound is melt|dissolved in an alkali solution, and it is used. As an alkaline solute used for an alkaline solution, ammonia and lithium hydroxide can be used. In this embodiment, it is preferable to use lithium hydroxide. As a solvent used for an alkali solution, what is necessary is just a liquid in which the said solute melt|dissolves, and water is mentioned.

After spray-mixing under each of the above conditions, the mixed powder is cooled to about room temperature (eg, 25° C.).

The manufacturing method of the positive electrode active material for lithium secondary batteries of this embodiment heats the composite metal compound which is a precursor of the positive electrode active material for lithium secondary batteries, and spray-mixes the alkali solution in which the tungsten compound was dissolved. According to this process, the alkali solution adheres to the surface of the composite metal compound, and the solvent of the alkali solution evaporates instantaneously, so that the tungsten particles do not agglomerate and can be mixed with the composite metal compound. For this reason, the positive electrode active material for lithium secondary batteries by which generation|occurrence|production of the foreign material derived from tungsten was suppressed can be manufactured.

[Process for producing lithium composite metal oxide]

The mixed powder of the composite metal compound and the tungsten compound (hereinafter, referred to as “mixed powder”) is mixed with a lithium salt. As the lithium salt, any one of lithium carbonate, lithium nitrate, lithium acetate, lithium hydroxide, lithium hydroxide hydrate, lithium oxide, or a mixture of two or more may be used.

The above lithium salt and mixed powder are used in consideration of the composition ratio of the final target product. In the spray mixing step, when an aqueous lithium hydroxide solution is used as the alkali solution, the lithium injection amount (addition amount) is the total amount of lithium and lithium salt in the lithium hydroxide used in the spray mixing step. For example, when nickel-cobalt-manganese composite hydroxide is used, the lithium salt and the mixed powder are used in a ratio corresponding to the composition ratio of LiNi _x Co _y Mn _z O ₂ (wherein, x + y + z = 1). .

Moreover, you may mix a lithium salt and the said mixed powder so that the molar ratio (Li/Me) of lithium in a lithium compound, and all the transition metal elements (Me) in the mixed powder containing nickel may become a ratio exceeding 1.

By calcining the mixture of the lithium salt and the mixed powder, a lithium-tungsten-nickel cobalt-manganese composite oxide is obtained. In addition, dry air, oxygen atmosphere, an inert atmosphere, etc. are used for baking according to a desired composition, and a several heating process required is implemented.

The calcination temperature of the mixed powder and lithium compounds such as lithium hydroxide and lithium carbonate is not particularly limited, but is preferably 600°C or more and 1100°C or less, more preferably 750°C or more and 1050°C or less, 800°C or more and 1025°C The following are more preferable. By setting the calcination temperature to 600°C or higher, the charging capacity can be increased. By setting the calcination temperature to 1100°C or lower, the volatilization of Li can be prevented, and a lithium-tungsten-nickel cobalt-manganese composite oxide having a target composition can be obtained.

The firing time is preferably from 3 hours to 50 hours. When the firing time exceeds 50 hours, the battery performance tends to be substantially inferior due to the volatilization of lithium. In other words, when the firing time is 50 hours or less, it is possible to prevent lithium from volatilizing. When the calcination time is less than 3 hours, the crystal development tends to be poor and the battery performance tends to deteriorate. In other words, when the firing time is 3 hours or more, the crystal development is good and the battery performance is good. It is also effective to perform preliminary firing before the above firing. The temperature of such preliminary baking is in the range of 300-850 degreeC, and it is preferable to perform for 1 to 10 hours.

It is preferable that the time from the start of temperature increase to reaching the calcination temperature is 0.5 hours or more and 20 hours or less. A more uniform lithium-tungsten-nickel-cobalt-manganese composite oxide can be obtained if the time from the start of temperature increase to reaching the firing temperature is within this range. Moreover, it is preferable that time from reaching a calcination temperature until temperature maintenance is complete|finished is 0.5 hour or more and 20 hours or less. When the time from reaching the calcination temperature until the temperature maintenance is completed is within this range, crystal development proceeds more favorably, and the battery performance can be further improved.

The lithium metal composite oxide obtained by calcination is appropriately classified after pulverization, and becomes a positive electrode active material applicable to a lithium secondary battery.

<Positive electrode active material for lithium secondary battery>

In this embodiment, it is preferable that the positive electrode active material for lithium secondary batteries manufactured contains the compound represented by the following compositional formula (I).

Li[Lix(Ni(1 - y - z - w)CoyMnzMw)1 -x]O ₂ ... (I)

(In formula (I), -0.1 ≤ x ≤ 0.2, 0 < y ≤ 0.5, 0 < z ≤ 0.8, 0 ≤ w ≤ 0.1, y + z + w < 1, M is Fe, Cu, Ti, Mg, At least one metal selected from the group consisting of Al, W, B, Mo, Nb, Zn, Sn, Zr, Ga and V is represented.)

In the present embodiment, when the produced positive electrode active material for a lithium secondary battery consists only of the lithium composite metal compound represented by the composition formula (I), W (tungsten) is necessarily contained in the metal represented by M in the composition formula (I). do it by doing

In the present embodiment, the produced positive electrode active material for a lithium secondary battery is a lithium composite metal compound represented by the composition formula (I), and a lithium composite containing no W (tungsten) among the metals represented by M in the composition formula (I). When a metal compound is contained, it shall contain the lithium composite metal compound and tungsten compound represented by the said compositional formula (I).

In the present embodiment, the tungsten content contained in the positive electrode active material for a lithium secondary battery is preferably 0.01 mol% or more and 1.0 mol% or less, more preferably 0.1 mol% or more and 0.9 mol% or less, with respect to the total molar amount of the transition metal, It is especially preferable that they are 0.2 mol% or more and 0.8 mol% or less. If the tungsten content contained in the positive electrode active material for a lithium secondary battery is 0.01 mol% or more and 1.0 mol% or less, the resistance reduction of the battery is expected.

From a viewpoint of obtaining the positive electrode active material for lithium secondary batteries with high cycling characteristics, it is preferable that x in the said composition formula (I) exceeds 0, It is more preferable that it is 0.01 or more, It is still more preferable that it is 0.02 or more. Further, from the viewpoint of obtaining a positive electrode active material for a lithium secondary battery having a higher initial coulombic efficiency, x in the composition formula (I) is preferably 0.1 or less, more preferably 0.08 or less, and still more preferably 0.06 or less.

The upper and lower limits of x can be arbitrarily combined. For example, x exceeds 0 and is preferably 0.1 or less, more preferably 0.01 or more and 0.08 or less, and still more preferably 0.02 or more and 0.06 or less.

In this specification, "high cycle characteristics" means that the discharge capacity retention rate is high.

Moreover, from a viewpoint of obtaining the positive electrode active material for lithium secondary batteries with high discharge capacity, it is preferable that y in the said composition formula (I) is 0.10 or more, It is more preferable that it is 0.20 or more, It is still more preferable that it is 0.30 or more. Moreover, from a viewpoint of obtaining a positive electrode active material for lithium secondary batteries with high thermal stability, it is preferable that y in the said composition formula (I) is 0.49 or less, It is more preferable that it is 0.48 or less, It is still more preferable that it is 0.47 or less.

The upper and lower limits of y may be arbitrarily combined. For example, y is preferably 0.10 or more and 0.49 or less, more preferably 0.20 or more and 0.48 or less, and still more preferably 0.30 or more and 0.47 or less.

Further, from the viewpoint of obtaining a positive electrode active material for a lithium secondary battery having a high discharge capacity at a high current rate, z in the composition formula (I) is preferably 0.05 or more, more preferably 0.10 or more, still more preferably 0.20 or more. do. Moreover, from a viewpoint of obtaining the positive electrode active material for lithium secondary batteries with high discharge capacity, it is preferable that z in the said composition formula (I) is 0.35 or less, It is more preferable that it is 0.30 or less, It is still more preferable that it is 0.25 or less.

The upper and lower limits of z may be arbitrarily combined. For example, it is preferable that z is 0.05 or more and 0.35 or less, It is more preferable that it is 0.10 or more and 0.30 or less, It is more preferable that it is 0.20 or more and 0.25 or less.

Moreover, from a viewpoint of obtaining the positive electrode active material for lithium secondary batteries with high cycling characteristics, it is preferable that w in the said composition formula (I) is 0.01 or more, It is more preferable that it is 0.03 or more, It is still more preferable that it is 0.05 or more. Further, from the viewpoint of obtaining a positive electrode active material for a lithium secondary battery having high storage characteristics at a high temperature (for example, under a 60°C environment), w in the composition formula (I) is preferably 0.09 or less, more preferably 0.08 or less and 0.07 or less is more preferable.

The upper and lower limits of w can be arbitrarily combined. For example, w is preferably 0.01 or more and 0.09 or less, more preferably 0.03 or more and 0.08 or less, and still more preferably 0.05 or more and 0.07 or less.

M in the composition formula (I) represents at least one metal selected from the group consisting of Fe, Cu, Ti, Mg, Al, W, B, Mo, Nb, Zn, Sn, Zr, Ga and V.

In addition, from the viewpoint of obtaining a positive electrode active material for a lithium secondary battery having high cycle characteristics, M in the composition formula (I) is preferably at least one metal selected from the group consisting of Ti, B, Mg, Al, W and Zr. And from the viewpoint of obtaining a positive electrode active material for a lithium secondary battery with high thermal stability, it is preferably at least one metal selected from the group consisting of B, Al, W and Zr.

(BET specific surface area)

In the present embodiment, from the viewpoint of obtaining a positive electrode active material for a lithium secondary battery having a high discharge capacity at a high current rate, the BET specific surface area (m2/g) of the positive electrode active material is preferably 0.1 m2/g or more, and 0.5 m2/g It is more preferable that it is more than it, and it is still more preferable that it is 1.0 m<2>/g or more. In addition, from the viewpoint of lowering the hygroscopicity of the positive electrode active material, the BET specific surface area (m2/g) of the positive electrode active material is preferably 4.0 m2/g or less, more preferably 3.8 m2/g or less, more preferably 2.6 m2/g or less. desirable.

The upper limit and the lower limit of the BET specific surface area (m 2 /g) of the positive electrode active material can be arbitrarily combined. For example, the BET specific surface area (m2/g) is preferably 0.1 m2/g or more and 4.0 m2/g or less, more preferably 0.5 m2/g or more and 3.8 m2/g or less, 1.05 m2/g or more and 2.6 m2 /g or less is more preferable.

The BET specific surface area in this embodiment is measured using Macsorb (trademark) by Muntech, after drying 1 g of powder of a positive electrode active material at 105 degreeC in nitrogen atmosphere for 30 minutes.

(Layered structure)

The crystal structure of the positive electrode active material is a layered structure, more preferably a hexagonal crystal structure or a monoclinic crystal structure.

The hexagonal crystal structure is P3, P3 ₁ , P3 ₂ , R3, P-3, R-3, P312, P321, P3 ₁ 12, P3 ₁ 21, P3 ₂ 12, P3 ₂ 21, R32, P3m1, P31m , P3c1, P31c, R3m, R3c, P-31m, P-31c, P-3m1, P-3c1, R-3m, R-3c, P6, P6 ₁ , P6 ₅ , P6 ₂ , P6 ₄ , P6 ₃ , P-6, P6/m, P6 ₃ /m, P622, P6 ₁ 22, P6 ₅ 22, P6 ₂ 22, P6 ₄ 22, P6 ₃ 22, P6mm, P6cc, P6 ₃ cm, P6 ₃ mc, P-6m2 , P-6c2, P-62m, P-62c, P6/mmm, P6/mcc, P6 ₃ /mcm, and P6 ₃ /mmc belong to any one space group selected from the group consisting of.

In addition, the monoclinic crystal structure is P2, P2 ₁ , C2, Pm, Pc, Cm, Cc, P2/m, P2 ₁ /m, C2/m, P2/c, P2 ₁ /c and C2/c. It belongs to any one space group selected from the group consisting of.

Among these, from the viewpoint of obtaining a positive electrode active material for a lithium secondary battery having a high discharge capacity, the crystal structure is a hexagonal crystal structure belonging to the space group R-3m, or a monoclinic crystal structure belonging to C2/m, particularly desirable.

<Lithium secondary battery>

Next, the positive electrode which used the positive electrode active material for lithium secondary batteries of this embodiment as a positive electrode active material of a lithium secondary battery, and the lithium secondary battery which has this positive electrode are demonstrated, demonstrating the structure of a lithium secondary battery.

An example of the lithium secondary battery of this embodiment has a positive electrode and a negative electrode, the separator clamped between a positive electrode and a negative electrode, and the electrolyte solution arrange|positioned between a positive electrode and a negative electrode.

1A and 1B are schematic diagrams showing an example of a lithium secondary battery of the present embodiment. The cylindrical lithium secondary battery 10 of this embodiment is manufactured as follows.

First, as shown in Fig. 1A, a pair of separators 1 having a band shape, a band-shaped positive electrode 2 having a positive electrode lead 21 at one end, and a band-shaped negative electrode having a negative electrode lead 31 at one end ( 3) is laminated in order of the separator 1, the positive electrode 2, the separator 1, and the negative electrode 3, and it is set as the electrode group 4 by winding.

Then, as shown in Fig. 1B, after accommodating the electrode group 4 and an insulator not shown in the battery can 5, the can bottom is sealed, and the electrode group 4 is impregnated with the electrolyte solution 6, An electrolyte is disposed between the positive electrode 2 and the negative electrode 3 . Further, the lithium secondary battery 10 can be manufactured by sealing the upper part of the battery can 5 with the top insulator 7 and the sealing body 8 .

As the shape of the electrode group 4, for example, the cross-sectional shape when the electrode group 4 is cut in a direction perpendicular to the winding axis is a circle, an ellipse, a rectangle,柱狀) can be mentioned.

In addition, as the shape of the lithium secondary battery having such an electrode group 4, a shape determined by IEC60086 or JIS C8500, which is a standard for batteries set by the International Electrotechnical Commission (IEC), can be adopted. For example, shapes, such as a cylindrical shape and a square, are mentioned.

In addition, the lithium secondary battery is not limited to the above-described wound-type configuration, and may have a stacked-type configuration in which a stacked structure of a positive electrode, a separator, a negative electrode, and a separator is repeatedly stacked. As a stacked lithium secondary battery, a so-called coin-type battery, a button-type battery, and a paper-type (or sheet-type) battery can be illustrated.

Hereinafter, each structure is demonstrated in order.

(positive pole)

The positive electrode of this embodiment can be manufactured by first adjusting the positive mix containing a positive electrode active material, a electrically conductive material, and a binder, and carrying out the positive mix on a positive electrode collector.

(conductive material)

A carbon material can be used as an electrically conductive material which the positive electrode of this embodiment has. As a carbon material, graphite powder, carbon black (for example, acetylene black), a fibrous carbon material, etc. are mentioned. Since carbon black is fine and has a large surface area, by adding a small amount to the positive electrode mixture, the internal conductivity of the positive electrode can be increased to improve charge/discharge efficiency and output characteristics. , and all of the binding force inside the positive mix is lowered, rather causing an increase in internal resistance.

It is preferable that the ratio of the electrically conductive material in positive mix is 5 mass parts or more and 20 mass parts or less with respect to 100 mass parts of positive electrode active materials. When a fibrous carbon material such as graphitized carbon fiber or carbon nanotube is used as the conductive material, it is also possible to lower this ratio.

(bookbinder)

A thermoplastic resin can be used as a binder which the positive electrode of this embodiment has.

Examples of the thermoplastic resin include polyvinylidene fluoride (hereinafter, may be referred to as PVdF), polytetrafluoroethylene (hereinafter may be referred to as PTFE), ethylene tetrafluoride/propylene hexafluoride/vinylidene fluoride. Fluorine resins, such as a denene type copolymer, a propylene hexafluoride/vinylidene fluoride type copolymer, and an ethylene tetrafluoride/perfluorovinyl ether type copolymer; polyolefin resins such as polyethylene and polypropylene; can be heard

You may use these thermoplastic resins in mixture of 2 or more types. By using a fluororesin and polyolefin resin as a binder, the ratio of the fluororesin with respect to the mass of the whole positive mix into 1 mass % or more and 10 mass % or less, and the ratio of the polyolefin resin being 0.1 mass % or more and 2 mass % or less, a positive electrode It is possible to obtain a positive mix having both high adhesion to the current collector and a high bonding force inside the positive mix.

(Positive electrode current collector)

As a positive electrode collector which the positive electrode of this embodiment has, the band-shaped member which makes metal materials, such as Al, Ni, and stainless steel, a forming material can be used. Among them, it is preferable to use Al as a forming material and process it into a thin film from the viewpoint of being easy to process and inexpensive.

As a method of supporting the positive electrode mixture on the positive electrode current collector, a method of press-molding the positive electrode mixture on the positive electrode current collector is exemplified. In addition, the positive electrode mixture may be supported on the positive electrode current collector by using an organic solvent to paste the positive mixture, and applying the resulting positive electrode mixture paste to at least one side of the positive electrode current collector, drying, and pressing and fixing.

As an organic solvent which can be used when making a positive mix into paste, amine solvents, such as N,N- dimethylamino propylamine and diethylenetriamine; ether solvents such as tetrahydrofuran; Ketone solvents, such as methyl ethyl ketone; ester solvents such as methyl acetate; amide solvents such as dimethylacetamide and N-methyl-2-pyrrolidone (hereinafter, may be referred to as NMP); can be heard

As a method of apply|coating the paste of positive mix to a positive electrode collector, the slit-die coating method, the screen coating method, the curtain coating method, the knife coating method, the gravure coating method, and the electrostatic spraying method are mentioned, for example.

A positive electrode can be manufactured by the method mentioned above.

(negative electrode)

The negative electrode of the lithium secondary battery of the present embodiment can be doped and dedoped with lithium ions at a potential lower than that of the positive electrode, and the negative electrode mixture containing the negative electrode active material is supported on the negative electrode current collector, and the negative electrode active material alone and an electrode made of

(Negative electrode active material)

Examples of the negative electrode active material of the negative electrode include carbon materials, chalcogen compounds (oxides, sulfides, etc.), nitrides, metals, or alloys, and materials capable of doping and dedoping with lithium ions at a potential lower than that of the positive electrode.

Examples of the carbon material that can be used as the negative electrode active material include graphite such as natural graphite and artificial graphite, cokes, carbon black, pyrolytic carbons, carbon fibers, and fired organic polymer compounds.

Examples of the oxide usable as the negative electrode active material include oxides of silicon represented by the formula SiO _x (here, x is a positive real number) such as SiO ₂ and SiO; Oxide of titanium represented by formula TiOx (here, _x is a positive real number), such as TiO2 _and TiO; Oxide _of vanadium represented by formula VOx (here, _x is _a positive real number), such as _V2O5 and VO2; oxides of iron represented by the formula FeO _x (here, x is a positive real number) such as Fe ₃ O ₄ , Fe ₂ O ₃ , and FeO; Oxide of tin represented by formula SnOx (here, _x is a positive real number), such as SnO2 and _SnO ; Oxides _of tungsten represented by general formula _WOx (here, _x is a positive real number), such as WO3 and WO2; Composite metal oxides containing lithium, titanium, or _vanadium , such as _{Li4Ti5O12 and LiVO2} ; can be heard

Examples of the sulfide usable as the negative electrode active material include sulfide of titanium represented by the formula TiS _x (here, x is a positive real number) such as Ti ₂ S ₃ , TiS ₂ , and TiS; Sulfide of vanadium represented by formula _VSx (here, _x is a positive real number), such as _V3S4 , _VS2 , VS; Sulfide of iron represented by formula _FeSx (here, _x is _a positive real number), such as Fe3S4, _FeS2 , FeS; Molybdenum sulfide represented by formula _MoSx (here, _x is a positive real number), such as _{Mo2S3 and} MoS2; Sulfide of tin represented by formula SnSx (here, _x is a positive real number), such as _SnS2 and SnS; Sulfide of tungsten represented by formula _WSx (here, _x is a positive real number), such as WS2; sulfide of antimony represented by the formula SbS _x (here, x is a positive real number) such as Sb ₂ S ₃ ; sulfide of selenium represented by the formula SeS _x (here, x is a positive real number) such as Se ₅ S ₃ , SeS ₂ , and SeS; can be heard

Examples of the nitride usable as the negative electrode active material include lithium-containing nitrides such as Li ₃ N and Li _3-x A _x N (where A is either or both of Ni and Co, and 0 < x < 3). can

These carbon materials, oxides, sulfides, and nitrides may be used alone or in combination of two or more thereof. Moreover, crystalline or amorphous any may be sufficient as these carbon materials, an oxide, a sulfide, and a nitride.

Moreover, lithium metal, a silicon metal, a tin metal, etc. are mentioned as a metal usable as a negative electrode active material.

As an alloy usable as a negative electrode active material, Lithium alloys, such as Li-Al, Li-Ni, Li-Si, Li-Sn, and Li-Sn-Ni; Silicon alloys, such as Si-Zn; Tin alloys, such as Sn-Mn, Sn-Co, Sn-Ni, Sn-Cu, and Sn-La; alloys such as Cu ₂ Sb and La ₃ Ni ₂ Sn ₇ ; can also be heard

These metals and alloys are mainly used alone as electrodes after being processed into thin films, for example.

Among the negative electrode active materials, the potential of the negative electrode hardly changes from an uncharged state to a fully charged state during charging (potential flatness is good), the average discharge potential is low, and the capacity retention rate when repeatedly charged and discharged is high For reasons such as (good cycle characteristics), a carbon material containing graphite as a main component, such as natural graphite or artificial graphite, is preferably used. The shape of the carbon material may be, for example, flaky like natural graphite, spherical like mesocarbon microbeads, fibrous like graphitized carbon fiber, or fine powder aggregate.

Said negative mix may contain a binder as needed. As a binder, a thermoplastic resin is mentioned, PVdF, a thermoplastic polyimide, carboxymethylcellulose, polyethylene, and polypropylene are mentioned specifically,.

(Negative electrode current collector)

As a negative electrode collector which a negative electrode has, the band-shaped member which uses metal materials, such as Cu, Ni, and stainless steel, as a forming material is mentioned. Among them, it is preferable to use Cu as a forming material and process it into a thin film from the viewpoint of being difficult to form an alloy with lithium and easy to process.

As a method of supporting the negative electrode mixture on such a negative electrode current collector, as in the case of a positive electrode, a method by pressure molding, a method by using a solvent, etc. to make a paste, apply on the negative electrode current collector, dry, and press to compress. can be heard

(separator)

The separator of the lithium secondary battery of the present embodiment includes, for example, a porous membrane, a nonwoven fabric, a woven fabric, etc. made of a material such as a polyolefin resin such as polyethylene or polypropylene, a fluororesin, or a nitrogen-containing aromatic polymer. material can be used. Moreover, a separator may be formed using 2 or more types of these materials, and these materials may be laminated|stacked and a separator may be formed.

In the present embodiment, the separator has an air permeation resistance according to the Gurley method determined by JIS P 8117, 50 sec/100 cc or more, 300 sec/ It is preferable that it is 100 cc or less, and it is more preferable that it is 50 sec/100 cc or more and 200 sec/100 cc or less.

Moreover, preferably the porosity of a separator is 30 volume% or more and 80 volume% or less with respect to the volume of a separator, More preferably, they are 40 volume% or more and 70 volume% or less. The separator may be one in which separators having different porosity are laminated.

(electrolyte)

The electrolyte solution which the lithium secondary battery of this embodiment has contains an electrolyte and an organic solvent.

Examples of the electrolyte contained in the electrolyte include LiClO ₄ , LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN(SO ₂ CF ₃ ) ₂ , LiN(SO ₂ C ₂ F ₅ ) ₂ , LiN( SO ₂ CF ₃ )(COCF ₃ ), Li(C ₄ F ₉ SO ₃ ), LiC(SO ₂ CF ₃ ) ₃ , Li ₂ B ₁₀ Cl ₁₀ , LiBOB (where BOB is bis(oxalato)borate. ), LiFSI (herein, FSI is bis (fluorosulfonyl)imide), lower aliphatic carboxylic acid lithium salt, LiAlCl ₄ and the like, and a mixture of two or more thereof may be used. Among them, the electrolyte is selected from the group consisting of fluorine-containing LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN(SO ₂ CF ₃ ) ₂ and LiC(SO ₂ CF ₃ ) ₃ . It is preferable to use the thing containing at least 1 type.

Examples of the organic solvent contained in the electrolytic solution include propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, 4-trifluoromethyl-1,3-dioxolan-2-one, carbonates such as 1,2-di(methoxycarbonyloxy)ethane; 1,2-dimethoxyethane, 1,3-dimethoxypropane, pentafluoropropylmethyl ether, 2,2,3,3-tetrafluoropropyldifluoromethyl ether, tetrahydrofuran, 2-methyltetrahydro ethers such as furan; esters such as methyl formate, methyl acetate, and γ-butyrolactone; nitriles such as acetonitrile and butyronitrile; amides such as N,N-dimethylformamide and N,N-dimethylacetamide; carbamates such as 3-methyl-2-oxazolidone; A sulfur-containing compound such as sulfolane, dimethyl sulfoxide, or 1,3-propane sultone, or one in which a fluoro group is introduced into these organic solvents (one in which at least one hydrogen atom in the organic solvent is replaced with a fluorine atom) may be used can

As an organic solvent, it is preferable to mix and use 2 or more types of these. Among them, a mixed solvent containing carbonates is preferable, and a mixed solvent of a cyclic carbonate and an acyclic carbonate and a mixed solvent of a cyclic carbonate and an ether are more preferable. As a mixed solvent of cyclic carbonate and acyclic carbonate, the mixed solvent containing ethylene carbonate, dimethyl carbonate, and ethylmethyl carbonate is preferable. The electrolyte solution using such a mixed solvent has a wide operating temperature range, is not easily degraded even when charging and discharging at a high current rate, is not easily degraded even when used for a long time, and natural graphite or artificial graphite as an active material for a negative electrode Even when graphite materials such as these are used, they have many features such as resistance to decomposition.

Moreover, as electrolyte solution, since the safety|security of the lithium secondary battery obtained becomes high, it is preferable to use the electrolyte solution containing lithium salt containing fluorine, such as _LiPF6 , and the organic solvent which has a fluorine substituent. A mixed solvent containing ethers having a fluorine substituent such as pentafluoropropylmethyl ether and 2,2,3,3-tetrafluoropropyldifluoromethyl ether and dimethyl carbonate is charged and discharged at a high current rate. It is more preferable because the capacity retention rate is high even if it is performed.

A solid electrolyte may be used instead of the above-described electrolyte solution. As the solid electrolyte, for example, an organic polymer electrolyte such as a polyethylene oxide-based polymer compound or a polymer compound containing at least one of polyorganosiloxane chains or polyoxyalkylene chains can be used. Moreover, what is called a gel type in which the nonaqueous electrolyte solution was hold|maintained in the high molecular compound can also be used. Li ₂ S-SiS ₂ , Li ₂ S-GeS ₂ , Li ₂ SP ₂ S ₅ , Li ₂ SB ₂ S ₃ , Li ₂ S-SiS ₂ -Li ₃ PO ₄ , Li ₂ S-SiS ₂ -Li ₂ Inorganic solid electrolytes containing sulfides, such as SO4 and _{Li2S -} GeS2 _{- P2S5} , are mentioned, You may use these ₂ or more types of mixture. By using these solid electrolytes, the safety|security of a lithium secondary battery may be improved more.

Moreover, in the lithium secondary battery of this embodiment, when using a solid electrolyte, a solid electrolyte may play the role of a separator, and a separator may not be required in that case.

Since the positive electrode active material of the above structure uses the lithium containing composite metal oxide of this embodiment mentioned above, the lifetime of the lithium secondary battery using the positive electrode active material can be extended.

Moreover, since the positive electrode of the above structure has the positive electrode active material for lithium secondary batteries of this embodiment mentioned above, the lifetime of a lithium secondary battery can be extended.

Moreover, since the lithium secondary battery of the above structure has the above-mentioned positive electrode, it becomes a lithium secondary battery with a longer life than before.

[Example]

Next, embodiments of the present invention will be described in more detail by way of examples.

In this Example, evaluation of the positive electrode active material for lithium secondary batteries was performed as follows.

[Evaluation of segregation of tungsten]

3 g of the positive electrode active material powder for lithium secondary batteries was extract|collected, and the image before reflection of the positive electrode active material for lithium ion secondary batteries was measured using a field emission scanning electron microscope (ULTRA PLUS by ZEISS). Images of 10 different fields of view were acquired at an acceleration voltage of 15 kV and a magnification of 500, and particles having different contrasts from the active material in the obtained image were regarded as segregation of tungsten, and the presence or absence of segregation of tungsten was evaluated.

[BET specific surface area measurement]

1 g of positive electrode active material powder for lithium secondary batteries or nickel cobalt-manganese composite metal hydroxide powder was dried in a nitrogen atmosphere at 105° C. for 30 minutes, and then measured using a BET specific surface area meter (Macsorb (registered trademark) manufactured by Mountec).

[Measurement of average particle diameter]

The average particle diameter is measured using a laser diffraction particle size distribution analyzer (manufactured by Horiba Corporation, LA-950), and 0.1 g of positive electrode active material powder for lithium secondary batteries or composite metal compound powder, 0.2 mass % sodium hexametaphosphate aqueous solution 50 ml to obtain a dispersion in which the powder was dispersed. The particle size distribution of the obtained dispersion was measured to obtain a volume-based cumulative particle size distribution curve. The obtained cumulative particle size distribution curve WHEREIN: The value of the particle diameter (D50) seen from the microparticle side at the time of ₅₀ % accumulation was made into the average particle diameter of the positive electrode active material for lithium secondary batteries.

[Composition analysis]

In the composition analysis of the lithium metal composite oxide powder produced by the method described below, the obtained lithium metal composite oxide powder is dissolved in hydrochloric acid, and then an inductively coupled plasma emission analyzer (manufactured by SI Nanotechnology Co., Ltd., SPS3000) is used. was done.

<Example 1>

«Production of positive electrode active material 1 for lithium secondary batteries»

[Method for preparing spray solution]

After putting water in the tank provided with a stirrer, lithium hydroxide aqueous solution and tungsten oxide were added, and the aqueous alkali solution in which tungsten oxide was dissolved was obtained. The tungsten oxide concentration in the aqueous alkali solution at this time was 2.8 mass % with respect to the mass of the whole aqueous alkali solution.

· Spray mixing process

Nickel cobalt manganese composite metal hydroxide powder (Ni _0.55 Co _0.21 Mn _0.24 (OH) ₂ ) (BET specific surface area: 86.3 m / g, D ₅₀ : 3.4 μm) was heated to 105 ° C. The dissolved aqueous alkali solution was sprayed for 1 hour. Then, it cooled and obtained the mixed powder 1. The spray conditions at this time are as follows.

{spray conditions}

Nozzle diameter: 45 μm

Discharge pressure: 0.6 MPaG

Flow rate: 1.9 ℓ/h

Nickel cobalt manganese composite metal hydroxide powder amount: 4100 g

Aqueous alkali solution: 1850 g

[Production Process of Lithium Composite Metal Oxide]

The mixed powder (1) and the lithium carbonate powder are weighed and mixed so that Li/(Ni+Co+Mn)=1.07, and then primary firing is performed at 760° C. for 5 hours under an atmospheric atmosphere, and further, the air Secondary baking for 10 hours was performed at 850 degreeC in atmosphere, and the target positive electrode active material 1 for lithium secondary batteries was obtained. The BET specific surface area of this positive electrode active material 1 for lithium secondary batteries was 3.8 m 2 /g, and D ₅₀ was 2.7 µm.

«Evaluation of the positive electrode active material 1 for lithium secondary batteries»

As a result of analyzing the composition of the obtained positive electrode active material 1 for lithium secondary batteries, it was Li:Ni:Co:Mn:W=1.07:0.55:0.21:0.24:0.005 in molar ratio.

Moreover, segregation was not seen in the positive electrode active material 1 for lithium secondary batteries, and the foreign material derived from tungsten was not recognized.

<Example 2>

«Production of positive electrode active material 2 for lithium secondary batteries»

[Method for preparing spray solution]

After putting water in the tank provided with a stirrer, lithium hydroxide aqueous solution and tungsten oxide were added, and the aqueous alkali solution in which tungsten oxide was dissolved was obtained. The tungsten oxide concentration in the aqueous alkali solution at this time was 5.6 mass % with respect to the mass of the whole aqueous alkali solution.

· Spray mixing process

Nickel-cobalt-manganese composite metal hydroxide powder (Ni _0.31 Co _0.33 Mn _0.36 (OH) ₂ ) (BET specific surface area: 37.2 m/g, D ₅₀ : 4.0 µm) was heated to 105° C. and mixed while mixing, the tungsten compound obtained above The aqueous alkali solution in which the was dissolved was sprayed for 0.5 hours. It cooled after that, and the mixed powder 2 was obtained. The spray conditions at this time are as follows.

{spray conditions}

Nozzle diameter: 45 μm

Discharge pressure: 0.6 MPaG

Flow rate: 1.9 ℓ/h

Nickel cobalt manganese composite metal hydroxide powder amount: 4100 g

Alkali solution amount: 950 g

[Production Process of Lithium Composite Metal Oxide]

Mixed powder 2 and lithium carbonate powder are weighed and mixed so that Li/(Ni+Co+Mn)=1.10, and then primary calcination is performed at 690°C in an air atmosphere for 5 hours, and further, in an air atmosphere Secondary baking for 6 hours was performed at 950 degreeC, and the target positive electrode active material 2 for lithium secondary batteries was obtained. The BET specific surface area of this positive electrode active material 2 for lithium secondary batteries was 2.4 m<2>/g, and _D50 was 3.6 micrometers.

«Evaluation of the positive electrode active material 2 for lithium secondary batteries»

As a result of analyzing the composition of the obtained positive electrode active material 2 for lithium secondary batteries, it was Li:Ni:Co:Mn:W=1.10:0.32:0.33:0.35:0.005 in molar ratio.

Moreover, segregation was not seen in the positive electrode active material 2 for lithium secondary batteries, and the foreign material derived from tungsten was not recognized.

<Example 3>

«Production of positive electrode active material 3 for lithium secondary batteries»

[Method for preparing spray solution]

After putting water in the tank provided with a stirrer, lithium hydroxide aqueous solution and tungsten oxide were added, and the aqueous alkali solution in which the tungsten oxide was dissolved was obtained. The tungsten oxide concentration in the aqueous alkali solution at this time was 2.8 mass % with respect to the mass of the whole aqueous alkali solution.

· Spray mixing process

Nickel cobalt-manganese composite metal hydroxide powder (Ni _0.31 Co _0.33 Mn _0.36 (OH) ₂ ) (BET specific surface area: 37.9 m 2 /g, D ₅₀ : 3.3 μm) was heated to 105 ° C. and mixed while mixing, the tungsten compound obtained above The aqueous alkali solution in which the was dissolved was sprayed for 1 hour. It cooled after that, and the mixed powder 3 was obtained. The spray conditions at this time are as follows.

{spray conditions}

Nozzle diameter: 45 μm

Discharge pressure: 0.6 MPaG

Flow rate: 1.9 ℓ/h

Nickel cobalt manganese composite metal hydroxide powder amount: 4100 g

Alkali aqueous solution: 1900 g

[Production Process of Lithium Composite Metal Oxide]

Mixed powder 3 and lithium carbonate powder are weighed and mixed so that Li/(Ni+Co+Mn)=1.10, then primary calcination is performed at 690°C in an atmospheric atmosphere for 5 hours, and further, in an atmospheric atmosphere Secondary baking for 6 hours was performed at 950 degreeC, and the target positive electrode active material 3 for lithium secondary batteries was obtained. The BET specific surface area of this positive electrode active material 3 for lithium secondary batteries was 2.4 m<2>/g, and _D50 was 3.4 micrometers.

«Evaluation of the positive electrode active material 3 for lithium secondary batteries»

As a result of performing compositional analysis of the obtained positive electrode active material 3 for lithium secondary batteries, it was Li:Ni:Co:Mn:W=1.10:0.32:0.33:0.36:0.005 by molar ratio.

Moreover, segregation was not seen in the positive electrode active material 3 for lithium secondary batteries, and the foreign material derived from tungsten was not recognized.

<Example 4>

«Production of positive electrode active material 4 for lithium secondary batteries»

[Method for preparing spray solution]

After putting water in the tank provided with a stirrer, lithium hydroxide aqueous solution and tungsten oxide were added, and the aqueous alkali solution in which tungsten oxide was dissolved was obtained. The tungsten oxide concentration in the aqueous alkali solution at this time was 2.8 mass % with respect to the mass of the whole aqueous alkali solution.

· Spray mixing process

Nickel-cobalt-manganese composite metal hydroxide powder (Ni _0.31 Co _0.33 Mn _0.36 (OH) ₂ ) (BET specific surface area: 29.8 m 2 /g, D ₅₀ : 4.0 µm) was heated to 105 ° C. and mixed, while mixing, the tungsten compound obtained above The aqueous alkali solution in which the was dissolved was sprayed for 1 hour. Then, it cooled and obtained the mixed powder 4. The spray conditions at this time are as follows.

{spray conditions}

Nozzle diameter: 45 μm

Discharge pressure: 0.6 MPaG

Flow rate: 1.9 ℓ/h

Nickel cobalt manganese composite metal hydroxide powder amount: 4100 g

Alkali aqueous solution: 1900 g

[Production Process of Lithium Composite Metal Oxide]

Mixed powder 4 and lithium carbonate powder were weighed and mixed so that Li/(Ni+Co+Mn)=1.10, followed by performing 4 hours at 690°C in an atmospheric atmosphere, and successively baking at 955°C for 6 hours. Thus, the target positive electrode active material 4 for lithium secondary batteries was obtained. The BET specific surface area of this positive electrode active material 4 for lithium secondary batteries was 1.8 m 2 /g, and D ₅₀ was 3.7 µm.

«Evaluation of the positive electrode active material 4 for lithium secondary batteries»

As a result of analyzing the composition of the obtained positive electrode active material 4 for lithium secondary batteries, it was Li:Ni:Co:Mn:W=1.11:0.32:0.33:0.35:0.005 by molar ratio.

Moreover, segregation was not seen in the positive electrode active material 4 for lithium secondary batteries, and the foreign material derived from tungsten was not recognized.

<Example 5>

«Production of positive electrode active material 5 for lithium secondary batteries»

[Method for preparing spray solution]

After putting water in the tank provided with a stirrer, lithium hydroxide aqueous solution and tungsten oxide were added, and the aqueous alkali solution in which tungsten oxide was dissolved was obtained. The tungsten oxide concentration in the aqueous alkali solution at this time was 2.3 mass % with respect to the mass of the whole aqueous alkali solution.

· Spray mixing process

Nickel cobalt manganese composite metal hydroxide powder (Ni _0.87 Co _0.10 Mn _0.02 Al _0.01 (OH) ₂ ) (BET specific surface area: 20.6 m 2 /g, D ₅₀ : 10.4 μm) was heated to 105° C. and mixed while being obtained above An aqueous alkali solution in which a tungsten compound was dissolved was sprayed for 2.5 hours. Then, it cooled and obtained the mixed powder 5. The spray conditions at this time are as follows.

{spray conditions}

Nozzle diameter: 45 μm

Discharge pressure: 0.6 MPaG

Flow rate: 1.9 ℓ/h

Nickel cobalt manganese composite metal hydroxide powder amount: 9000 g

Aqueous alkali solution: 4700 g

[Production Process of Lithium Composite Metal Oxide]

Mixed powder 5 and lithium carbonate powder are weighed and mixed so that Li/(Ni+Co+Mn)=1.02, and then primary firing is performed at 760°C in oxygen atmosphere for 5 hours, and then, oxygen atmosphere Then, secondary baking was carried out at 760 degreeC for 10 hours, and the target positive electrode active material 5 for lithium secondary batteries was obtained. The BET specific surface area of this positive electrode active material 5 for lithium secondary batteries was 0.26 m 2 /g, and D ₅₀ was 10.9 µm.

«Evaluation of positive electrode active material 5 for lithium secondary batteries»

As a result of analyzing the composition of the obtained positive electrode active material 5 for lithium secondary batteries, it was Li:Ni:Co:Mn:Al:W=0.99:0.89:0.09:0.02:0.02:0.004 in molar ratio.

Moreover, segregation was not seen in the positive electrode active material 5 for lithium secondary batteries, and the foreign material derived from tungsten was not recognized.

<Comparative Example 1>

«Production of positive electrode active material 6 for lithium secondary batteries»

Nickel-cobalt-manganese composite metal hydroxide powder (Ni _0.55 Co _0.21 Mn _0.24 (OH) ₂ ) (BET specific surface area: 82.6 m/g, D ₅₀ : 3.6 µm) and tungsten oxide powder were mixed with a W of 0.005 per 1 mol of the transition metal. It measured so that it might become mol, and it dry-mixed for 1 hour, and the mixed powder 6 was obtained.

Mixed powder 6 and lithium carbonate powder are weighed and mixed so that Li/(Ni+Co+Mn)=1.07, and then primary calcination is performed at 760°C for 5 hours under atmospheric atmosphere, and then, atmospheric atmosphere Then, secondary baking was carried out at 850 degreeC for 10 hours, and the target positive electrode active material 6 for lithium secondary batteries was obtained. The BET specific surface area of this positive electrode active material 6 for lithium secondary batteries was 3.2 m 2 /g, and D ₅₀ was 3.2 µm.

«Evaluation of positive electrode active material 6 for lithium secondary batteries»

As a result of performing compositional analysis of the obtained positive electrode active material 6 for lithium secondary batteries, it was Li:Ni:Co:Mn:W=1.07:0.55:0.21:0.24:0.005 by molar ratio.

Moreover, segregation was seen in the positive electrode active material 6 for lithium secondary batteries, and the foreign material derived from tungsten was confirmed.

<Comparative Example 2>

«Production of positive electrode active material 7 for lithium secondary batteries»

[Manufacturing process of composite metal compound]

Nickel-cobalt-manganese composite metal hydroxide powder (Ni _0.31 Co _0.33 Mn _0.36 (OH) ₂ ) (BET specific surface area: 37.2 m/g, D ₅₀ : 4.0 µm) and tungsten oxide powder, W per 1 mol of the transition metal was 0.005 It weighed so that it might become mol, and it dry-mixed for 1 hour, and the mixed powder 7 was obtained.

[Production Process of Lithium Composite Metal Oxide]

The mixed powder 7 obtained in the above process was heat-treated. Specifically, primary baking for 5 hours was performed at 690 degreeC in atmospheric atmosphere, and secondary baking for 6 hours was performed at 950 degreeC in atmospheric atmosphere after that.

Mixed powder 7 and lithium carbonate powder were weighed and mixed so that Li/(Ni+Co+Mn)=1.10, and then primary calcination was performed at 690°C for 5 hours under an atmospheric atmosphere, and further, under an atmospheric atmosphere The target positive electrode active material 7 for lithium secondary batteries was obtained by performing secondary baking for 6 hours at 925 degreeC. The BET specific surface area of this positive electrode active material 7 for lithium secondary batteries was 2.2 m 2 /g, and D ₅₀ was 3.8 µm.

«Evaluation of the positive electrode active material 7 for lithium secondary batteries»

As a result of analyzing the composition of the obtained positive electrode active material 7 for lithium secondary batteries, it was Li:Ni:Co:Mn:W=1.10:0.32:0.33:0.35:0.005 in molar ratio.

Moreover, segregation was seen in the positive electrode active material 7 for lithium secondary batteries, and the foreign material derived from tungsten was confirmed.

<Comparative example 3>

«Production of positive electrode active material 8 for lithium secondary batteries»

Nickel-cobalt-manganese composite metal hydroxide powder (Ni _0.87 Co _0.10 Mn _0.02 Al _0.01 (OH) ₂ ) (BET specific surface area: 20.6 m 2 /g, D ₅₀ : 10.4 µm) and tungsten oxide powder, W per 1 mol of transition metal It weighed so that it might be set to 0.004 mol, and it dry-mixed for 1 hour, and the mixed powder 8 was obtained.

[Production Process of Lithium Composite Metal Oxide]

Mixed powder 8 and lithium carbonate powder are weighed and mixed so that Li/(Ni+Co+Mn)=1.02, and then primary firing is performed at 760°C in an oxygen atmosphere for 5 hours, and then in an oxygen atmosphere Then, secondary baking was carried out at 760 degreeC for 10 hours, and the target positive electrode active material 8 for lithium secondary batteries was obtained. The BET specific surface area of this positive electrode active material 8 for lithium secondary batteries was 0.28 m 2 /g, and D ₅₀ was 10.6 µm.

«Evaluation of the positive electrode active material 8 for lithium secondary batteries»

As a result of analyzing the composition of the obtained positive electrode active material 8 for lithium secondary batteries, it was Li:Ni:Co:Mn:Al:W=0.99:0.89:0.09:0.02:0.02:0.004 in molar ratio.

Moreover, segregation was seen in the positive electrode active material 8 for lithium secondary batteries, and the foreign material derived from tungsten was confirmed.

<Comparative Example 4>

«Production of positive electrode active material 9 for lithium secondary batteries»

Nickel-cobalt-manganese composite metal hydroxide powder (Ni _0.55 Co _0.21 Mn _0.24 (OH) ₂ ) (BET specific surface area: 84.0 m 2 /g, D ₅₀ : 3.5 µm) and lithium carbonate powder were mixed with Li/(Ni + Co + Mn). ) = 1.07, after weighing and mixing, primary firing was performed at 760°C in an air atmosphere for 10 hours, and the obtained composite metal compound powder 9 and tungsten oxide powder were dry-mixed for 1 hour. Then, secondary baking for 10 hours was performed at 850 degreeC in oxygen atmosphere, and the target positive electrode active material 9 for lithium secondary batteries was obtained. The BET specific surface area of this positive electrode active material 9 for lithium secondary batteries was 3.5 m 2 /g, and D ₅₀ was 3.0 µm.

«Evaluation of positive electrode active material 9 for lithium secondary batteries»

As a result of analyzing the composition of the obtained positive electrode active material 9 for lithium secondary batteries, it was Li:Ni:Co:Mn:W=1.07:0.56:0.21:0.24:0.005 in molar ratio.

Moreover, segregation was seen in the positive electrode active material 9 for lithium secondary batteries, and the foreign material derived from tungsten was confirmed.

About Examples 1-5 and Comparative Examples 1-4, manufacturing conditions etc. are put together in Table 1, and are described. In Table 1 below, "W" means tungsten.

As described in the above results, in Examples 1 to 5 to which the present invention is applied, segregation products derived from tungsten were not seen, and the generation of foreign substances could be suppressed. On the other hand, in Comparative Examples 1 to 4 to which the present invention was not applied, segregation products derived from tungsten were seen and foreign substances were generated.

The SEM photograph of the mixed powder after dry mixing of Comparative Example 2 is shown in FIG. 2, and the SEM photograph of the mixed powder after spray mixing of Example 3 is described in FIG. In Comparative Example 2 to which the present invention is not applied, segregation products derived from tungsten were confirmed at the location indicated by reference numeral 20 in FIG. 2 . On the other hand, in Example 3 to which this invention is applied, the segregation material derived from tungsten was not confirmed after mixing of tungsten.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the positive electrode active material for lithium secondary batteries by which segregation of tungsten was suppressed can be provided.

1: separator;
2: positive electrode,
3: negative electrode;
4: electrode group;
5: battery can,
6: electrolyte,
7: top insulator,
8: spheroid,
10: lithium secondary battery;
21: positive lead,
31: negative electrode lead

Claims (6)

A method for producing a positive electrode active material for a lithium secondary battery containing a lithium composite metal compound, the method comprising:
heating the composite metal compound powder containing nickel, cobalt and manganese, spraying an alkali solution of tungsten oxide onto the composite metal compound powder, and mixing the composite metal compound powder and the tungsten oxide to prepare a mixed powder; , thereafter, a spray mixing process comprising cooling the mixed powder;
A method for producing a positive electrode active material for a lithium secondary battery, comprising a step of mixing a lithium salt and the mixed powder and calcining to prepare a lithium composite metal compound. The method of claim 1,
The manufacturing method of the positive electrode active material for lithium secondary batteries in which the said lithium composite metal compound is represented by the following compositional formula (I).
Li[Lix(Ni(1 - y - z - w)CoyMnzMw)1 -x]O ₂ ... (I)
(In formula (I), -0.1 ≤ x ≤ 0.2, 0 < y ≤ 0.5, 0 < z ≤ 0.8, 0 ≤ w ≤ 0.1, y + z + w < 1, M is Fe, Cu, Ti, Mg, At least one metal selected from the group consisting of Al, W, B, Mo, Nb, Zn, Sn, Zr, Ga and V is represented.) 3. The method of claim 1 or 2,
The manufacturing method of the positive electrode active material for lithium secondary batteries whose tungsten content contained in the said positive electrode active material for lithium secondary batteries is 1.0 mol% or less with respect to the total molar amount of a transition metal. 3. The method of claim 1 or 2,
The said spray mixing process WHEREIN: The manufacturing method of the positive electrode active material for lithium secondary batteries in which the said alkali solution contains lithium hydroxide. 3. The method of claim 1 or 2,
In the said spray mixing process, the temperature of the composite metal compound powder at the time of spraying the said alkali solution is 100 degreeC or more, The manufacturing method of the positive electrode active material for lithium secondary batteries. delete

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