WO2015147209A1

WO2015147209A1 - Method for manufacturing lithium metal complex oxide having layered crystal structure

Info

Publication number: WO2015147209A1
Application number: PCT/JP2015/059468
Authority: WO
Inventors: 大輔鷲田; 徹也光本; 仁彦井手; 祥巳畑
Original assignee: 三井金属鉱業株式会社
Priority date: 2014-03-28
Filing date: 2015-03-26
Publication date: 2015-10-01
Also published as: JPWO2015147209A1; JP6546582B2

Abstract

The invention relates to a method for manufacturing a lithium metal complex oxide having a layered crystal structure, and provides a novel method for manufacturing a lithium metal complex oxide which when used as a cathode active material for a lithium secondary battery, can suppress reaction with an electrolyte to improve the lifetime characteristics of the battery and give output characteristics that are equal to or better than the past. After firing, a lithium metal complex oxide powder is treated on its surface using a surface treatment agent including aluminum, titanium, or zirconium or a dispersion of the surface treatment agent, then the surface-treated lithium metal complex oxide powder is heat treated in an oxygen-containing atmosphere while maintained at a temperature of 700 to 950°C.

Description

Method for producing lithium metal composite oxide having layered crystal structure

The present invention relates to a method for producing a lithium metal composite oxide having a layered crystal structure that can be used as a positive electrode active material of a lithium battery.

Lithium batteries, especially lithium secondary batteries, have features such as high energy density and long life, so they can be used for home appliances such as video cameras, portable electronic devices such as notebook computers and mobile phones. Used as a power source. Recently, the lithium secondary battery is also applied to a large battery mounted on an electric vehicle (EV), a hybrid electric vehicle (HEV), or the like.

A lithium secondary battery is a secondary battery with a structure in which lithium is melted as ions from the positive electrode during charging, moves to the negative electrode and is stored, and reversely, lithium ions return from the negative electrode to the positive electrode during discharging. It is known to be caused by the potential of the positive electrode material.

As positive electrode active materials for lithium secondary batteries, lithium manganese oxide (LiMn ₂ O ₄ ) having a spinel structure and lithium metal composite oxides such as LiCoO ₂ , LiNiO ₂ and LiMnO ₂ having a layered crystal structure are known. It has been. For example, LiCoO ₂ has a layered crystal structure in which lithium atom layers and cobalt atom layers are alternately stacked via oxygen atom layers, has a large charge / discharge capacity, and is excellent in diffusibility of lithium ion storage / desorption. Therefore, most of the lithium secondary batteries currently on the market are lithium metal composite oxides having a layered crystal structure such as LiCoO ₂ .

A lithium metal composite oxide having a layered crystal structure such as LiCoO ₂ or LiNiO ₂ is represented by a general formula LiMO ₂ (M: transition metal). The crystal structure of these lithium metal composite oxides having a layered crystal structure belongs to the space group R-3m ("-" is usually attached to the upper part of "3" and indicates reversal. The same applies hereinafter). The Li ion, Me ion, and oxide ion occupy the 3a site, 3b site, and 6c site, respectively. It is known that a layer composed of Li ions (Li layer) and a layer composed of Me ions (Me layer) exhibit a layered crystal structure in which they are alternately stacked via O layers composed of oxide ions.

Regarding a method for producing a lithium metal composite oxide having a layered crystal structure, for example, in Patent Document 1, an alkaline solution is added to a mixed aqueous solution of manganese and nickel to coprecipitate manganese and nickel, lithium hydroxide is added, and A manufacturing method for obtaining a lithium metal composite oxide by firing is disclosed.

Further, in Patent Document 2, a raw material containing a lithium salt compound, a manganese salt compound, a nickel salt compound and a cobalt salt compound is mixed, mixed and stirred in water to prepare a slurry, and this slurry is pulverized. A method for producing a lithium metal composite oxide having a layer structure by granulating and drying a pulverized slurry using a thermal spray dryer or the like and then calcination and pulverization is disclosed.

By the way, since the positive electrode active material has a lower electric conductivity than a general conductor, an element having a higher electric conductivity so as to further increase the electric conductivity between the current collector and the positive electrode active material or between the active materials. It has been proposed to modify the positive electrode active material.
For example, Patent Document 3 proposes a method of improving cycle characteristics and reducing internal resistance by modifying a lithium composite oxide with a compound such as Co.
In Patent Document 4, after mixing the raw materials for lithium composite oxide, the surface of the composite oxide particles produced through the steps of firing, crushing, heat treatment and classification, Al, Mg, Sn, It is disclosed that the internal resistance can be lowered and high output can be obtained by using a surface-modified metal compound film containing at least one of Ti, Zn and Zr as a positive electrode active material. .

JP-A-8-171910 JP 2013-232400 A JP 2002-151083 A JP 2005-310744 A

When a lithium metal composite oxide having a layered crystal structure is used as the positive electrode active material of a lithium secondary battery, it can be used at a high voltage, with a charge voltage of 4.3 V or less on a metal lithium basis, or charged and discharged at a voltage exceeding 4.3 V. Otherwise, the surface of the lithium metal composite oxide is changed due to the reaction with the electrolytic solution, which causes a problem that the life characteristics of the battery are deteriorated.
As an example of means for solving such a problem, it is conceivable to coat the particle surface of the lithium metal composite oxide with an oxide. However, if the surface of the lithium metal composite oxide particles is covered with an oxide, a new problem arises that the output characteristics of the battery are degraded.
Thus, regarding the lithium metal composite oxide having a layered crystal structure, it is not easy to achieve both life characteristics and output characteristics.

Therefore, the present invention relates to a method for producing a lithium metal composite oxide having a layered crystal structure, and when used as a positive electrode active material of a lithium secondary battery, it can suppress a reaction with an electrolyte and improve a battery life characteristic. In addition, the present invention is to provide a new method for producing a lithium metal composite oxide capable of making output characteristics equivalent or higher.

The present invention relates to a surface treatment step of performing a surface treatment of a lithium metal composite oxide powder using a surface treatment agent containing at least one of aluminum, titanium and zirconium, and a lithium metal composite oxide after the surface treatment. A method for producing a lithium metal composite oxide having a layered crystal structure, comprising a heat treatment step for heat treating the powder, wherein in the heat treatment step, the surface-treated lithium metal composite oxide powder is heated at a temperature in an oxygen-containing atmosphere. A method for producing a lithium metal composite oxide having a layered crystal structure, characterized in that heat treatment is performed so as to maintain at 700 to 950 ° C. is proposed.

According to the method for producing a lithium metal composite oxide proposed by the present invention, a surface layer containing at least one of aluminum, titanium and zirconium can be formed on the surface of the lithium metal composite oxide particles. As a result, when the lithium metal composite oxide particles are used as a positive electrode active material of a lithium secondary battery, the life characteristics can be improved by suppressing the reaction with the electrolytic solution, and the output characteristics are equivalent or more. Can be. Therefore, the obtained lithium metal composite oxide is particularly excellent as a positive electrode active material of a battery mounted on a vehicle, in particular, an electric vehicle (EV: Electric Vehicle) or a hybrid electric vehicle (HEV: Hybrid Electric Vehicle). It will be a thing.

It is a figure for demonstrating the structure of the cell for electrochemical evaluation produced by the battery characteristic evaluation of an Example.

Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to the following embodiment.

<This manufacturing method>
A method for producing a lithium metal composite oxide (hereinafter referred to as “the present lithium metal composite oxide”) according to an example of the present embodiment (hereinafter referred to as “the present production method”) contains at least one of aluminum, titanium, and zirconium. A surface treatment step of performing a surface treatment of a lithium metal composite oxide powder (referred to as “matrix lithium metal composite oxide powder”) using the surface treatment agent to be treated, and heat treating the lithium metal composite oxide powder after the surface treatment A method for producing a lithium metal composite oxide having a layered crystal structure, comprising a heat treatment step.

Since the present manufacturing method only needs to include the surface treatment step and the heat treatment step, it may further include other steps. For example, a crushing step may be inserted after the heat treatment step, or a crushing step or a classification step may be inserted before the surface treatment step. Moreover, you may add another process.

<The lithium metal composite oxide>
The lithium metal composite oxide, which is a product of this production method, is not particularly limited in composition as long as it is a lithium metal composite oxide having a layered crystal structure. That is, the lithium metal composite oxide may be a lithium metal composite oxide having a layered crystal structure in which lithium atomic layers and metal atomic layers are alternately stacked via oxygen atomic layers.

The lithium metal composite oxide having a layered crystal structure has a common problem, and the effects of surface treatment and heat treatment are the same, so there is no need to limit the composition.
However, in this section, it is easier to understand the present manufacturing method based on a more specific example. Therefore, in-vehicle batteries, in particular, electric vehicles (EVs) and hybrid electric vehicles (HEVs) are described. The following lithium metal composite oxide preferable as a positive electrode active material of a lithium secondary battery to be mounted on) will be described as an example.

As an example of the present lithium metal composite oxide, a lithium metal composite oxide having a layered crystal structure represented by the general formula (1): Li _{1 + x} M _1-x O ₂ can be given.

“1 + x” in the above formula (1) is 1.00 to 1.07, more preferably 1.01 or more and 1.07 or less, and more preferably 1.02 or more and 1.06 or less.

“M” in the above formula (1) represents Mn, Co, Ni, transition elements existing between Group 3 elements of the periodic table and Group 11 elements and the third period of the periodic table. Any one or more of the typical elements may be used.
Here, as transition elements existing between the Group 3 elements of the periodic table and the Group 11 elements and typical elements from the third period of the periodic table, for example, Al, V, Fe, Ti, Mg, Cr , Ga, In, Cu, Zn, Nb, Zr, Mo, W, Ta, Re, and the like.
“M” is, for example, any one of Mn, Co, Ni, Al, V, Fe, Ti, Mg, Cr, Ga, In, Cu, Zn, Nb, Zr, Mo, W, Ta, and Re. That is all you need. Therefore, “M” may be composed of, for example, only three elements of Mn, Co, and Ni, or the three elements may include one or more of the other elements, or may have other structures. .

When “M” in the above formula (1) contains three elements of Mn, Co and Ni, the molar ratio of Mn, Co and Ni is Mn: Co: Ni = 0.10 to 0.45: 0.05 to 0.40: 0.30 to 0.75 is preferable, and Mn: Co: Ni = 0.10 to 0.40: 0.05 to 0.40: 0.30 to 0. More preferably, it is 75.
In the above general formulas (1) and (2), the atomic ratio of the oxygen amount is described as “2” for convenience, but may have some non-stoichiometry.

The present lithium metal composite oxide may contain 0.33 wt% or less of S as impurities and 0.17 wt% or less of other elements. This is because an amount of this level is considered to hardly affect the characteristics of the present lithium metal composite oxide.

<Raw material>
Examples of the lithium compound as a raw material include lithium hydroxide (including LiOH and LiOH.H ₂ O), lithium carbonate (Li ₂ CO ₃ ), lithium nitrate (LiNO ₃ ), lithium oxide (Li ₂ O), and other fatty acids. Examples thereof include lithium and lithium halide.
The kind of manganese compound is not particularly limited. For example, manganese carbonate, manganese nitrate, manganese chloride, manganese dioxide, manganese oxide (iii), trimanganese tetraoxide, and the like can be used, and among these, manganese carbonate and manganese dioxide are preferable. Among these, electrolytic manganese dioxide obtained by an electrolytic method is particularly preferable.
The kind of the nickel salt compound is not particularly limited, and for example, nickel carbonate, nickel nitrate, nickel chloride, nickel oxyhydroxide, nickel hydroxide, nickel oxide, etc. can be used, among which nickel carbonate, nickel hydroxide, nickel oxide are used. preferable.
The type of the cobalt compound is not particularly limited, and for example, basic cobalt carbonate, cobalt nitrate, cobalt chloride, cobalt oxyhydroxide, cobalt hydroxide, cobalt oxide and the like can be used. Among them, basic cobalt carbonate, cobalt hydroxide Cobalt oxide and cobalt oxyhydroxide are preferred.
The type of the aluminum compound is not particularly limited, and for example, aluminum carbonate, aluminum nitrate, aluminum chloride, aluminum oxyhydroxide, aluminum hydroxide, aluminum oxide and the like can be used, and among them, aluminum carbonate, aluminum hydroxide, and aluminum oxide are preferable. .

In addition, hydroxides, carbonates, nitrates, and the like of the M element in the above formula (1) can be used as raw materials.

<Base lithium metal composite oxide powder>
In this production method, the base lithium metal composite oxide powder is obtained by mixing raw materials, granulating and drying as necessary, firing, heat treatment as necessary, and further crushing as necessary. Can do. The obtained lithium metal composite oxide powder can also be obtained by subjecting it to a predetermined treatment.

The base lithium metal composite oxide powder preferably has a moisture content of 50 to 1000 ppm measured at 110 to 300 ° C. by the Karl Fischer method. If the moisture content is 50 ppm or more, the reaction with the coupling agent among the surface treatment agents can be enhanced, and the surface treatment effect can be enhanced. On the other hand, if the water content is 1000 ppm or less, it is preferable in that the battery characteristics can be made equal or more.
From this point of view, the moisture content of the base lithium metal composite oxide powder is preferably 50 to 1000 ppm, more preferably 50 ppm or more and 700 ppm or less, of which 50 ppm or more or 500 ppm or less, and more preferably 400 ppm or less. preferable.
The water content measured at 110 to 300 ° C. by the Karl Fischer method is measured in a device at 110 ° C. in a nitrogen atmosphere using a Karl Fischer moisture meter (for example, CA-100 manufactured by Mitsubishi Chemical Corporation). This is the amount of water released when a sample is heated for 45 minutes, then heated to 300 ° C. and heated at 300 ° C. for 45 minutes.
The water measured at 110 to 300 ° C. by the Karl Fischer method is considered to be mainly water chemically bonded to the inside of the base lithium metal composite oxide powder particles.

Examples of means for adjusting the moisture content of the base lithium metal composite oxide powder to the above range include drying, dehumidification, and humidity control. However, it is not limited to such a method.

(Mixing process)
It is preferable to mix the raw materials for obtaining the base lithium metal composite oxide powder by adding a liquid medium such as water or a dispersant and wet-mixing it to form a slurry. And when employ | adopting the spray-drying method mentioned later, it is preferable to grind | pulverize the above-mentioned obtained slurry with a wet grinder. However, dry pulverization may be performed.

In the mixing process, in order to improve the homogeneity at the time of raw material mixing by removing the coarse powder of the nickel raw material, at least the nickel compound is preliminarily mixed and the nickel compound and the aluminum compound are pulverized and classified before mixing the raw materials. The maximum particle size (Dmax) of the nickel compound is preferably adjusted to be 10 μm or less, particularly 5 μm or less, and more preferably 4 μm or less.

(Granulation)
After mixing the raw materials, it is preferable to granulate as necessary.
The granulation method may be either wet or dry as long as various raw materials are dispersed in the granulated particles without being separated. Extrusion granulation method, rolling granulation method, fluidized granulation method, mixed granulation method, spraying method A dry granulation method, a pressure molding granulation method, or a flake granulation method using a roll or the like may be used.
However, when wet granulation is performed, it is necessary to sufficiently dry before firing. As a drying method at this time, it may be dried by a known drying method such as a spray heat drying method, a hot air drying method, a vacuum drying method, a freeze drying method, etc., among which the spray heat drying method is preferable.
The spray heat drying method is preferably carried out using a heat spray dryer (spray dryer) (referred to herein as “spray drying method”).
However, it is also possible to produce a coprecipitated powder to be fired by, for example, a so-called coprecipitation method (referred to herein as “coprecipitation method”). In the coprecipitation method, after the raw material is dissolved in a solution, the coprecipitation powder can be obtained by adjusting the conditions such as pH and causing precipitation.

In the spray drying method, the powder strength is relatively low, and voids tend to occur between the particles. Therefore, when the spray drying method is adopted, the crushing strength after the crushing step after the firing step, which will be described later, is higher than that of a conventional crushing method, for example, a crushing method using a coarse crusher having a rotation speed of about 1000 rpm. It is preferable to employ a high grinding method.

(Baking process)
In the firing step for obtaining the base lithium metal composite oxide powder, it is preferable to perform preliminary firing at 500 to 840 ° C., if necessary, followed by main firing at 700 to 1000 ° C. It is also possible to perform the main baking at 700 to 1000 ° C. without performing the preliminary baking.
By calcining, a gas (for example, CO ₂ ) generated from a component contained in the raw material can be extracted. Therefore, for example, when a carbonate such as lithium carbonate (Li ₂ CO ₃ ), manganese carbonate, nickel carbonate, basic cobalt carbonate or the like is used as a raw material, it is preferably calcined.
And in this baking, the crystallinity of particle | grains can be raised or it can adjust to the desired particle size by baking at high temperature rather than temporary baking.

Temporary baking is performed at a temperature of 500 to 840 ° C. in a baking furnace in an air atmosphere, an oxygen gas atmosphere, an atmosphere in which an oxygen partial pressure is adjusted, a carbon dioxide gas-containing atmosphere, or other atmosphere (: This means the temperature when a thermocouple is brought into contact with the fired product in the firing furnace.) Especially, 600 ° C. or higher or 840 ° C. or lower, especially 650 ° C. or higher or 750 ° C. or lower, and held for 0.5 to 30 hours It is preferable to perform firing.
The kind of baking furnace is not specifically limited. For example, it can be fired using a rotary kiln, a stationary furnace, or other firing furnace.

The main firing is performed in a firing furnace in an air atmosphere, an oxygen gas atmosphere, an atmosphere in which an oxygen partial pressure is adjusted, a carbon dioxide gas-containing atmosphere, or other atmosphere, at a temperature of 700 to 1000 ° C. It means the temperature when a thermocouple is brought into contact with the fired product in the furnace.), Preferably 750 ° C. or higher or 950 ° C. or lower, more preferably 800 ° C. or higher or 950 ° C. or lower, and more preferably 850 ° C. or higher. Alternatively, firing is preferably performed at 910 ° C. or lower for 0.5 to 30 hours. At this time, it is preferable to select a firing condition in which a fired product including a plurality of metal elements can be regarded as a single phase of a lithium metal composite oxide having a target composition.
The kind of baking furnace is not specifically limited. For example, it can be fired using a rotary kiln, a stationary furnace, or other firing furnace.

However, when the main baking is performed without pre-baking, the temperature is 700 to 1000 ° C., particularly 750 ° C. or higher or 950 ° C. or lower, particularly 800 ° C. or higher or 950 ° C. or lower, and more preferably 850 ° C. or higher or 910 ° C. or lower. Calcination is preferably performed for 5 hours to 30 hours.

(Heat treatment)
The heat treatment after firing is preferably performed when the crystal structure needs to be adjusted. As the heat treatment atmosphere at that time, it is preferable to perform the heat treatment under conditions of an oxidizing atmosphere such as an air atmosphere, an oxygen gas atmosphere, or an atmosphere in which the oxygen partial pressure is adjusted.

(Disintegration)
Crushing after firing or heat treatment is preferably performed using a high-speed rotary pulverizer or the like. If pulverization is performed by a high-speed rotary pulverizer, it is possible to pulverize a portion where the particles are aggregated or weakly sintered, and to suppress distortion of the particles. However, the present invention is not limited to a high-speed rotary pulverizer.

An example of a high-speed rotary pulverizer is a pin mill. The pin mill is known as a rotary disk crusher, and is a type of crusher that draws in powder from a raw material supply port by rotating a rotating disk with pins to make the inside negative pressure. Therefore, since the fine particles are light in weight, they are easy to ride on the air current and pass through the clearance in the pin mill, while the coarse particles are reliably crushed. Therefore, when pulverizing with a pin mill, aggregation between particles and weakly sintered portions can be surely solved, and distortion can be suppressed from entering into the particles.
The rotational speed of the high-speed rotary pulverizer is preferably 4000 rpm or more, particularly 5000 to 12000 rpm, more preferably 7000 to 10000 rpm.

Since the classification after firing has the technical significance of adjusting the particle size distribution of the agglomerated powder and removing foreign matter, it is preferable to classify by selecting a sieve having a preferred size.

(Surface treatment process)
In the surface treatment step, the surface treatment agent containing at least one of aluminum, titanium, and zirconium may be brought into contact with the base lithium metal composite oxide powder obtained as described above.
For example, an organometallic compound containing at least one of aluminum, titanium, and zirconium, such as a titanium coupling agent, an aluminum coupling agent, a zirconium coupling agent, a titanium-aluminum coupling agent, a titanium-zirconium coupling agent, or an aluminum. A surface treatment agent such as zirconium coupling agent or titanium / aluminum / zirconium coupling agent is dispersed in an organic solvent to form a dispersion, and the dispersion and the base lithium metal composite oxide powder obtained as described above Can be mentioned as a surface treatment.

The surface treatment agent may be a compound having an organic functional group and a hydrolyzable group in the molecule, and among them, one having phosphorus (P) in the side chain is preferable. The coupling agent having phosphorus (P) in the side chain is particularly excellent in binding property with the binder because of better compatibility with the binder.

In the surface treatment step, a surface treatment agent equivalent to 0.1 to 20 parts by mass is preferably brought into contact with 100 parts by mass of the lithium metal composite oxide powder, and in particular, 0.5 parts by mass or more or 10 parts by mass or less. Among them, it is more preferable to contact the lithium metal composite oxide powder with a surface treatment agent of 1 part by mass or more or 5 parts by mass or less, and more preferably 1 part by mass or more and 3 parts by mass or less.

More specifically, for example, the ratio of the total number of moles of aluminum, titanium and zirconium in the surface treatment agent to the number of moles of the lithium metal composite oxide powder {(M / lithium metal composite oxide powder) × 100 ( M: Al, Ti, Zr)} is 0.005 to 4%, particularly 0.04% or more or 2% or less, and more preferably 0.08% or more or 1% or less. In particular, it is preferable that the lithium metal composite oxide powder and the surface treatment agent are brought into contact with each other so that the content is 0.08% or more or 0.6% or less.

Further, the ratio of the total number of moles of aluminum, titanium and zirconium in the surface treatment agent to the number of moles of nickel in the lithium metal composite oxide powder {(M / Ni) × 100 (M: Al, Ti, Zr) } Is 0.01 to 13%, in particular 0.05% or more or 7% or less, and in particular, 0.1% or more or 3.5% or less. It is preferable that the lithium metal composite oxide powder and the surface treatment agent are brought into contact with each other so as to be 1% or more or 2% or less.
When the Ni content is high, the life deterioration at a relatively high voltage becomes relatively large. Therefore, it is preferable to adjust the total amount of aluminum, titanium and zirconium in the surface treatment agent by the ratio with respect to the Ni content.

The amount of the dispersion in which the surface treatment agent is dispersed in the organic solvent is 0.2 to 20 parts by mass, particularly 1 to 15 parts by mass, with respect to 100 parts by mass of the lithium metal composite oxide powder. Among them, it is preferable to contact the lithium metal composite oxide powder with an amount of 2 parts by mass or more and 10 parts by mass or less, and among them, an amount of 2 parts by mass or more or 7 parts by mass or less.

In the case of a lithium metal composite oxide having a layered crystal structure, if the amount of the organic solvent to be contacted is large, lithium in the layered crystal structure will be eluted, so the amount of the surface treatment agent or the surface treatment agent is dispersed in the organic solvent. It is preferred to limit the amount of dispersion made as described above.
In addition, by bringing a small amount of a surface treatment agent or a dispersion in which a surface treatment agent is dispersed in an organic solvent into contact with the lithium metal composite oxide powder, the surface treatment agent is mixed with the atmosphere or oxygen while being mixed with the lithium metal composite oxide. The oxide powder can be contacted. As a result, oxygen can be left on the particle surface, which can be assumed to contribute to the supply of oxygen consumed in the oxidation reaction of the organic matter during the subsequent heat treatment.
At this time, the above-mentioned amount of the surface treatment agent or the dispersion in which the surface treatment agent is dispersed in the organic solvent is not brought into contact with the lithium metal composite oxide powder and mixed at once, but is brought into contact several times. It is preferable to repeat the mixing process.
Regarding the contact method at this time, that is, a method in which the dispersion in which the surface treatment agent is dispersed in the organic solvent is brought into contact with the lithium metal composite oxide powder, for example, the dispersion is sprayed on the lithium metal composite oxide powder. Examples thereof include a method, a dripping method, and a spraying method.

Also, the type of mixer used for the surface treatment is not particularly limited. Mixing can be performed using a mixing / kneading stirrer, a container rotating mixer, etc., for example, a planetary mixer, a Henschel mixer, a nauter mixer, a cutter mill, or other mixers.

When performing the surface treatment using the above-described surface treatment agent, it is preferable to heat and dry the next step after heating to 40 to 120 ° C., for example, in order to volatilize the organic solvent.

(Heat treatment process)
In the heat treatment step, the surface-treated lithium metal composite oxide powder is heated to 700 to 950 ° C. in an atmosphere having an oxygen concentration of 20 to 100% (temperature when a thermocouple is brought into contact with the fired product in the furnace, That is, it means the product temperature.) It is preferable to heat-treat so as to hold for a predetermined time.
By such heat treatment, the organic solvent can be volatilized or the side chain of the surface treatment agent can be decomposed, and aluminum, titanium, or zirconium in the surface treatment agent can be diffused from the surface in a deeper layer direction. The life characteristics are improved, and the output characteristics can be made equal or better.

From the viewpoint of further enhancing the effect of such heat treatment, the treatment atmosphere in the heat treatment step is preferably an oxygen-containing atmosphere. Among them, an oxygen-containing atmosphere having an oxygen concentration of 20 to 100% is preferable, of which 30% or more or 100% or less, of which 50% or more or 100% or less, of which 70% or more or 100% or less. Of these, an oxygen-containing atmosphere of 80% or more or 100% or less is more preferable.

Further, the treatment temperature in the heat treatment step is preferably 700 to 950 ° C. (meaning the temperature when a thermocouple is brought into contact with the fired product in the firing furnace). When the heat treatment temperature is 700 ° C. or higher, the bond between the lithium metal composite oxide and the surface layer to be formed can be further strengthened, and the output characteristics can be improved. On the other hand, if the heat treatment temperature is 950 ° C. or lower, the release of oxygen from the lithium metal composite oxide can be suppressed and the cycle characteristics can be maintained. From this point of view, the heat treatment temperature is preferably 700 to 950 ° C., may be higher than 800 ° C., more preferably 750 ° C. or more and 900 ° C. or less, and more preferably 750 ° C. or more and 850 ° C. or less.

Furthermore, the treatment time in the heat treatment step is preferably 0.5 to 20 hours, depending on the treatment temperature, and is preferably 1 hour or more or 10 hours or less, more preferably 3 hours or more or 10 hours or less. Is more preferable.
The type of furnace is not particularly limited. For example, it can be fired using a rotary kiln, a stationary furnace, or other firing furnace.

After the heat treatment step, the lithium metal composite oxide powder may be pulverized with a pulverization strength at which the change rate of the specific surface area (SSA) before and after pulverization becomes 100 to 250%.
Crushing after heat treatment is performed so that the new surface under the surface treatment layer is not exposed too much so as to maintain the effect of the surface treatment. From the viewpoint of changing the specific surface area (SSA) before and after crushing. It is preferable that the rate is 100 to 200%, among which 100% or more and 175% or less, among which 100% or more and 150% or less, and among them, the pulverization is performed so as to be 100% or more and 125% or less. preferable.

As a preferable example of such a crushing method, a crushing apparatus (for example, a pin mill) that crushes with a pin attached to a crushing plate that rotates at a high speed in a relative direction, and a rotation speed of 4000 rpm to 10,000 rpm, particularly 4000 rpm or more or 9000 rpm. Hereinafter, among them, a method of grinding at 4000 rpm or more or 8000 rpm or less can be mentioned.

(Classification)
Classification after crushing has technical significance of adjusting the particle size distribution of the agglomerated powder and removing foreign substances, and therefore, it is preferable to classify by selecting a sieve having a preferable size.

<Characteristics / Applications>
A common feature that the present lithium metal composite oxide obtained by the present manufacturing method can have is that the entire surface or part of the surface of the lithium metal composite oxide particle when observed by TEM, Al element, Ti Lithium metal composite oxide particles containing at least one of element and Zr element, and having a specific surface area (SSA) of 0.2 to 3 m ² / g, especially 0.2 m ² / g or more or 2 m ² / g hereinafter, 0.2 m ² / g or more or 1.0 m ² / g or less among them, mention may be made of points even not greater than 0.2 m ² / g or 0.8 m ² / g among them.
The present lithium metal composite oxide, when used as a positive electrode active material of a lithium secondary battery due to the presence of at least one of Al element, Ti element and Zr element in the surface layer of the particles, The life characteristics can be improved by suppressing the reaction, and the output characteristics can be made equal or better.
Therefore, the present lithium metal composite oxide is suitable for use as a positive electrode active material of a lithium secondary battery, and particularly a battery for vehicle use, particularly an electric vehicle (EV) and a hybrid electric vehicle (HEV: Hybrid). It is particularly excellent as a positive electrode active material for batteries mounted on electric vehicles.

For example, the lithium metal composite oxide powder is mixed with a conductive material made of carbon black or the like and a binder made of Teflon (Teflon is a registered trademark of DUPONT, USA) binder or the like to mix the positive electrode. Agent can be produced. Such a positive electrode mixture is used for the positive electrode, for example, a material that can store and desorb lithium such as lithium or carbon is used for the negative electrode, and lithium such as lithium hexafluorophosphate (LiPF ₆ ) is used for the non-aqueous electrolyte. A lithium secondary battery can be constituted by using a salt dissolved in a mixed solvent such as ethylene carbonate-dimethyl carbonate. However, the present invention is not limited to the battery having such a configuration.

Lithium batteries equipped with this lithium metal composite oxide as a positive electrode active material exhibit excellent life characteristics (cycle characteristics) when repeatedly used for charge and discharge, and are particularly suitable for electric vehicles (EVs) and EVs. It is particularly excellent in the use of a positive electrode active material of a lithium battery used as a power source for driving a motor mounted on a hybrid electric vehicle (HEV).

A “hybrid vehicle” is a vehicle that uses two power sources, an electric motor and an internal combustion engine.
The term “lithium battery” is intended to encompass all batteries containing lithium or lithium ions in the battery, such as lithium primary batteries, lithium secondary batteries, lithium ion secondary batteries, and lithium polymer batteries.

<Explanation of words>
In the present specification, when expressed as “X to Y” (X and Y are arbitrary numbers), “X is preferably greater than X” or “preferably Y”, with the meaning of “X to Y” unless otherwise specified. It also includes the meaning of “smaller”.
In addition, when expressed as “X or more” (X is an arbitrary number) or “Y or less” (Y is an arbitrary number), it is “preferably greater than X” or “preferably less than Y”. Includes intentions.

Next, the present invention will be further described based on examples and comparative examples. However, the present invention is not limited to the following examples.

<Example 1>
Lithium carbonate having an average particle size (D50) of 7 μm, electrolytic manganese dioxide having an average particle size (D50) of 23 μm and a specific surface area of 40 m ² / g, nickel hydroxide having an average particle size (D50) of 22 μm, an average particle size ( D50) 14 [mu] m cobalt oxyhydroxide and an average particle diameter (D50) of 1.4 [mu] m aluminum hydroxide in a molar ratio of Li: Mn: Ni: Co: Al = 1.05: 0.27: 0.46 : 0.21: 0.01.

An aqueous polycarboxylic acid ammonium salt solution (SN Dispersant 5468 manufactured by San Nopco Co., Ltd.) was added as a dispersant to ion-exchanged water. The amount of dispersant added was 6 wt% with respect to nickel hydroxide and aluminum hydroxide.
Nickel hydroxide and aluminum hydroxide were added to the above ion-exchanged water, mixed and stirred to prepare a slurry having a solid content concentration of 40 wt%. This slurry was wet pulverized for 60 minutes at 1300 rpm using a wet pulverizer (Nippon Coke SC220 / 70A-VB-ZZ). The average particle size (D50) was 0.56 μm and the maximum particle size (Dmax) was 1. A pulverized slurry of 9 μm was obtained.
Next, weighed electrolytic manganese dioxide, cobalt oxyhydroxide, lithium carbonate and ion-exchanged water are added to the pulverized slurry containing nickel hydroxide and aluminum hydroxide to prepare a slurry having a solid content concentration of 60 wt%. did. At that time, the dispersant was added so as to be 6 wt% with respect to the solid content in the slurry.
The slurry was wet pulverized at 1300 rpm for 50 minutes using the same wet pulverizer as described above to obtain a mixed pulverized slurry having an average particle diameter (D50) of 0.45 μm and a maximum particle diameter (Dmax) of 1.6 μm. It was.
The obtained mixed and pulverized slurry was granulated and dried using a thermal spray dryer (spray dryer, OC-16 manufactured by Okawahara Chemical Co., Ltd.). At this time, a two-fluid nozzle was used for spraying, and granulation drying was performed by adjusting the temperature so that the spray pressure was 0.6 MPa, the slurry supply amount was 14 kg / hr, and the outlet temperature of the drying tower was 100 to 110 ° C. .
The obtained granulated powder was calcined at 700 ° C. for 5 hours in an air atmosphere using a stationary electric furnace, and then calcined at 910 ° C. for 20 hours in the air.

The lithium metal composite oxide powder obtained by firing had a moisture content of 340 ppm measured at 110 to 300 ° C. by the Karl Fischer method.
As a result of chemical analysis of the lithium metal composite oxide powder obtained by firing, lithium metal composite oxide powder (sample) Li _1.05 Ni _0.46 Co _0.21 Mn _0.27 Al _0.01 O ₂ .

Next, 3.0 parts by mass of an aluminum coupling agent (Ajinomoto Fine Techno Co., Ltd., Plenact AL-M) as a surface treatment agent and 3.8 parts by mass of isopropyl alcohol as a solvent are mixed, and aluminum is added to the solvent. A dispersion in which a coupling agent was dispersed was prepared. Thereafter, 6.8 parts by mass of the dispersion was added to 100 parts by mass of the lithium metal composite oxide powder obtained by firing and mixed using a cutter mill (Milcer 720G manufactured by Iwatani Corporation). .
Next, it was dried in an oven at 100 ° C. for 1 hour in the atmosphere. Thereafter, heat treatment was performed in an atmosphere having an oxygen concentration of 100% so as to maintain the product temperature at 770 ° C. for 5 hours to obtain a lithium metal composite oxide powder.
The lithium metal composite oxide obtained by the heat treatment was classified with a sieve having an opening of 53 μm to obtain a lithium metal composite oxide powder (sample) under the sieve.

<Example 2>
A lithium metal composite oxide powder (sample) was obtained in the same manner as in Example 1 except that the heat treatment temperature after the surface treatment was changed to 910 ° C. in Example 1.

<Example 3>
In Example 1, the amount of isopropyl alcohol used in the surface treatment was changed from 3.8 parts by mass to 5.0 parts by mass, the addition amount of the dispersion was changed from 6.8 parts by mass to 8.0 parts by mass, and In the same manner as in Example 1, except that the heat treatment condition after the surface treatment is changed to “heat treatment is performed so that the product temperature is maintained at 700 ° C. for 5 hours in an atmosphere having an oxygen concentration of 50%”. A powder (sample) was obtained.

<Example 4>
In Example 1, the amount of the aluminum coupling agent used in the surface treatment was changed from 3.0 parts by weight to 1.0 part by weight, the amount of isopropyl alcohol 3.8 parts by weight was changed to 19.0 parts by weight, Further, a lithium metal composite oxide powder (sample) was obtained in the same manner as in Example 1 except that the amount of dispersion added was changed from 6.8 parts by mass to 20.0 parts by mass.

<Example 5>
In Example 1, the amount of the aluminum coupling agent used in the surface treatment was changed from 3.0 parts by weight to 0.5 parts by weight, the amount of isopropyl alcohol was changed from 3.8 parts by weight to 2.5 parts by weight, Further, the amount of the dispersion added was changed from 6.8 parts by mass to 3.0 parts by mass, and the heat treatment temperature after the surface treatment was changed to 810 ° C. (Sample) was obtained.

<Example 6>
In Example 1, the amount of the aluminum coupling agent used in the surface treatment was changed from 3.0 parts by weight to 4.0 parts by weight, the amount of isopropyl alcohol from 3.8 parts by weight was changed to 5.1 parts by weight, The amount of dispersion added was changed from 6.8 parts by mass to 9.1 parts by mass, and the heat treatment conditions after the surface treatment were changed to “maintain the product temperature at 770 ° C. for 5 hours in an atmosphere with an oxygen concentration of 80%. A lithium metal composite oxide powder (sample) was obtained in the same manner as in Example 1 except that the heat treatment was changed.

<Example 7>
In Example 1, 3.0 parts by mass of the aluminum coupling agent used in the surface treatment was changed to 1.0 part by mass of a titanium coupling agent (Ajinomoto Fine Techno Co., Ltd., Plenact KR 46B), and the amount of isopropyl alcohol was changed to 3. In the same manner as in Example 1, except that 8 parts by mass was changed to 5.0 parts by mass, and the addition amount of dispersion 6.8 parts by mass was changed to 6.0 parts by mass, a lithium metal composite oxide powder ( Sample).

<Example 8>
In Example 1, 3.0 parts by mass of the aluminum coupling agent used in the surface treatment was added to a zirconium coupling agent (Kenrich Petrochemicals, Inc. Ken-React®). NZ (registered trademark) 12) The amount was changed to 1.1 parts by mass, the amount of isopropyl alcohol was changed from 3.8 parts by mass to 4.9 parts by mass, and the addition amount of the dispersion was changed from 6.8 parts by mass to 6.0 parts by mass. Except for the above, a lithium metal composite oxide powder (sample) was obtained in the same manner as in Example 1.

<Comparative Example 1>
An aqueous polycarboxylic acid ammonium salt solution (SN Dispersant 5468 manufactured by San Nopco Co., Ltd.) as a dispersant was added to ion-exchanged water. The addition amount of the dispersant was 6 wt% with respect to the total amount of Ni raw material, Mn raw material, Co raw material, Li raw material and the like described later, and was sufficiently dissolved and mixed in ion-exchanged water.
Lithium carbonate having an average particle size (D50) of 7 μm, electrolytic manganese dioxide having an average particle size (D50) of 23 μm and a specific surface area of 40 m ² / g, nickel hydroxide having an average particle size (D50) of 22 μm, an average particle size ( D50) 14 μm cobalt oxyhydroxide was weighed so that the molar ratio was Li: Mn: Ni: Co = 1.04: 0.26: 0.51: 0.19, and the solid content concentration was 50 wt%. The slurry was adjusted and pulverized with a wet pulverizer at 1300 rpm for 40 minutes, and wet pulverized until the average particle size (D50) became 0.55 μm.
The obtained pulverized slurry was granulated and dried using a thermal spray dryer (spray dryer, OC-16 manufactured by Okawahara Chemical Co., Ltd.). At this time, a rotating disk was used for spraying, and granulation drying was performed by adjusting the temperature so that the rotation speed was 24,000 rpm, the slurry supply amount was 20 kg / hr, and the outlet temperature of the drying tower was 100 ° C.
The obtained granulated powder was calcined at 450 ° C. in the atmosphere using a stationary electric furnace. Subsequently, the calcined powder was fired in the atmosphere at 910 ° C. for 20 hours using a stationary electric furnace.
The fired lump obtained by firing was put in a mortar and crushed, classified with a sieve having an opening of 53 μm, and the lithium metal composite oxide powder (sample) under the sieve was collected.
As a result of chemical analysis of the collected lithium metal composite oxide powder (sample), it was Li _1.04 Ni _0.52 Co _0.19 Mn _0.25 O ₂ .

<Analysis of surface layer>
A cross section near the particle surface of the lithium metal composite oxide (sample) was observed with a transmission electron microscope (“JEM-ARM200F” manufactured by JEOL Ltd.) and analyzed with EDS (energy dispersive X-ray analysis).
As a result, for the lithium metal composite oxide (sample) obtained in Examples 1 and 2, it was confirmed that a layer containing a large amount of Al element was present on the surface of each particle.

<Measurement of D50>
The lithium metal composite oxide powders (samples) obtained in the examples and comparative examples were measured using an automatic sample feeder for laser diffraction particle size distribution measuring device (“Microtorac SDC” manufactured by Nikkiso Co., Ltd.). The powder (sample) was put into a water-soluble solvent and irradiated with ultrasonic waves of 40 W at a flow rate of 40% for 360 seconds, and then the particle size distribution was measured using a laser diffraction particle size analyzer “MT3000II” manufactured by Nikkiso Co., Ltd. Then, D50 was determined from the obtained volume-based particle size distribution chart.
The water-soluble solvent used in the measurement was passed through a 60 μm filter, the solvent refractive index was 1.33, the particle permeability was transmissive, the particle refractive index was 2.46, the shape was non-spherical, and the measurement range was 0.133. ˜704.0 μm, the measurement time was 30 seconds, and the average value measured twice was D50.

<Measurement of specific surface area>
Lithium metal composite oxide powder (sample) 0.5g was weighed and put into a glass cell for a flow method gas adsorption specific surface area measurement device MONOSORB LOOP ("product name MS-18" manufactured by Yuasa Ionics Co., Ltd.). In the MONOSORB LOOP pretreatment apparatus, the inside of the glass cell was replaced for 5 minutes while flowing nitrogen gas at a gas amount of 30 mL / min, and then the treatment was performed in the nitrogen gas atmosphere at 250 ° C. for 10 minutes. Then, the sample (powder) was measured by the BET single point method using the MONOSORB LOOP.
The adsorbed gas at the time of measurement was a mixed gas of 30% nitrogen: 70% helium.

<Battery characteristics evaluation>
8.0 g of lithium metal composite oxide powder (sample) obtained in Examples and Comparative Examples and 1.0 g of acetylene black (manufactured by Denki Kagaku Kogyo) were accurately weighed and mixed in a mortar for 10 minutes. Thereafter, 8.3 g of a solution in which 12 wt% of PVDF (manufactured by Kishida Chemical) was dissolved in NMP (N-methylpyrrolidone) was accurately weighed, and a mixture of lithium metal composite oxide powder and acetylene black was added thereto and further mixed. . Thereafter, 5 ml of NMP was added and mixed well to prepare a paste. This paste is placed on an aluminum foil as a current collector, coated with an applicator adjusted to a gap of 100 μm to 280 μm, dried in a vacuum at 140 ° C. overnight, and then rolled so that the linear pressure becomes 0.3 t / cm ^2. Pressed and punched out with a diameter of 16 mm to form a positive electrode.
Immediately before producing the battery, it was vacuum-dried at 200 ° C. for 300 minutes or longer to remove the adhering moisture and incorporated into the battery. In addition, an average value of the weight of an aluminum foil having a diameter of 16 mm was obtained in advance, and the weight of the positive electrode mixture was obtained by subtracting the weight of the aluminum foil from the weight of the positive electrode. Further, the content of the positive electrode active material was determined from the mixing ratio of the lithium metal composite oxide powder (positive electrode active material), acetylene black and PVDF.
The negative electrode was made of metal Li with a diameter of 19 mm and a thickness of 0.5 mm, and the electrolyte was a mixture of EC and DMC in a volume of 3: 7, and a solvent in which 1 mol / L of LiPF ₆ was dissolved as a solute was used. A cell for electrochemical evaluation shown in 1 (TOMCEL (registered trademark)) was prepared.

(Initial activity)
Using the electrochemical cell prepared as described above, initial activity was performed by the method described below. After constant current and constant potential charging at 0.2C to 25V at 25 ° C, constant current discharging was performed to 0.2V at 0.2C. This was repeated for 2 cycles. The actually set current value was calculated from the content of the positive electrode active material in the positive electrode.

(High temperature cycle life evaluation: 45 ° C high temperature cycle characteristics)
A charge / discharge test was conducted by the method described below using the electrochemical cell after the initial activity as described above, and the high-temperature cycle life characteristics were evaluated.
Place the cell in an environmental testing machine set so that the environmental temperature for charging and discharging the battery is 45 ° C., prepare to charge and discharge, and let it stand for 4 hours so that the cell temperature becomes the environmental temperature, then charge and discharge range Was set to 4.3 V to 3.0 V, charging was performed at a constant constant potential of 0.2 C and discharging was performed for one cycle at a constant constant current of 0.2 C, and then 40 cycles of charging and discharging were performed at 1 C.
The percentage (%) of the numerical value obtained by dividing the discharge capacity at the 40th cycle by the discharge capacity at the second cycle was determined as the high temperature cycle life characteristic value.
Table 1 shows the high-temperature cycle life characteristic values of the examples and the comparative examples as relative values when the high-temperature cycle life characteristic value of the comparative example 1 is 100.

(Output characteristic evaluation test)
Separately, the electrochemical cell after initial activation was charged at a constant current of 0.2% to 50% SOC at 25 ° C. After charging, discharge for 10 seconds at a current value of 3C, subtract the post-discharge potential from the potential after charging, and determine the resistance value by dividing the potential difference by the current value of 3C. It was. Table 1 shows the relative value (%) when the resistance value of Comparative Example 1 is 100.0%. The smaller the value, the better the output characteristics.

In the following Table 1, “(M / lithium metal composite oxide powder) × 100” means the ratio of the total number of moles of aluminum, titanium and zirconium in the surface treatment agent to the number of moles of the lithium metal composite oxide powder ( M: Al, Ti, Zr), and “(M / Ni) × 100” is the sum of aluminum, titanium and zirconium in the surface treatment agent relative to the number of moles of nickel in the lithium metal composite oxide powder. "Molecular ratio (M: Al, Ti, Zr)}" and "addition amount of surface treatment agent dispersion" means a dispersion lithium metal composite oxide in which the surface treatment agent is dispersed in an organic solvent It means the amount added with respect to 100 parts by mass of the powder.

(Discussion)
As in the above example, the sintered lithium metal composite oxide powder is a dispersion containing a surface treatment agent containing at least one of aluminum, titanium and zirconium or a surface treatment agent dispersed in an organic solvent. After the surface treatment of the lithium metal composite oxide powder, the lithium metal composite oxide was heat-treated in an oxygen atmosphere, preferably in an atmosphere having an oxygen concentration of 20 to 100% and maintained at a temperature of 700 to 950 ° C. A surface layer containing at least one of aluminum, titanium, and zirconium can be formed on the surface of the particles, and when used as a positive electrode active material of a lithium secondary battery, the life of the lithium secondary battery is suppressed and the reaction with the electrolyte is suppressed. It was found that the characteristics could be improved and the output characteristics could be made equal or better.

In addition, although said Example is an Example about lithium metal complex oxide which has a layered crystal structure of a specific composition, according to the test result and technical common sense which this inventor performed so far, a layered crystal structure is shown. Since the lithium metal composite oxide has a common problem, and the effects of surface treatment and heat treatment are the same, any lithium metal composite oxide having a layered crystal structure can be used regardless of its composition. It can be considered that the same effect can be obtained in common.

Claims

A surface treatment step of performing a surface treatment of the lithium metal composite oxide powder using an organometallic compound containing at least one of aluminum, titanium and zirconium, and heat treating the lithium metal composite oxide powder after the surface treatment A method for producing a lithium metal composite oxide having a layered crystal structure, comprising a heat treatment step,
In the heat treatment step, the lithium metal composite oxide powder having a layered crystal structure is heat-treated so that the surface-treated lithium metal composite oxide powder is maintained at a temperature of 700 to 950 ° C. in an oxygen-containing atmosphere. Manufacturing method.
The lithium metal composite oxide according to claim 1, wherein in the surface treatment step, a surface treatment agent corresponding to 0.1 to 20 parts by mass is brought into contact with 100 parts by mass of the lithium metal composite oxide powder. Production method.
In the surface treatment step, the ratio of the total number of moles of aluminum, titanium and zirconium in the surface treatment agent to the number of moles of the lithium metal composite oxide powder {(M / lithium metal composite oxide powder) × 100 (M: 2. The lithium metal composite oxide according to claim 1, wherein the lithium metal composite oxide powder and the surface treatment agent are brought into contact so that Al, Ti, Zr)} is 0.005 to 4%. Production method.
In the surface treatment step, the ratio of the total number of moles of aluminum, titanium and zirconium in the surface treatment agent to the number of moles of nickel in the lithium metal composite oxide powder {(M / Ni) × 100 (M: Al, 2. The method for producing a lithium metal composite oxide according to claim 1, wherein the lithium metal composite oxide powder is brought into contact with the surface treatment agent so that Ti, Zr)} is 0.01 to 13%. .
5. In the surface treatment step, 0.2 to 20 parts by mass of a dispersion in which a surface treatment agent is dispersed in an organic solvent is brought into contact with 100 parts by mass of a lithium metal composite oxide powder. A method for producing a lithium metal composite oxide according to any one of the above.
A crushing step of crushing the lithium metal composite oxide powder at a crushing strength at which the change rate of the specific surface area (SSA) before and after crushing is 100 to 250% is further provided after the heat treatment step. 6. The method for producing a lithium metal composite oxide according to any one of 5 above.
The method for producing a lithium metal composite oxide according to any one of claims 1 to 6, wherein the organometallic compound used for the surface treatment is a coupling agent.