JP2010282982A - Lithium transition metal complex oxide and lithium battery made by using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithium transition metal complex oxide of large discharge capacity and excellent in rate characteristics, and to provide its manufacturing method. <P>SOLUTION: In the stratified rock salt lithium transition metal complex oxide expressed in: Li<SB>1+x</SB>M<SB>1-x</SB>O<SB>2</SB>(wherein M is at least one transition metal selected from nickel, manganese, cobalt, iron, copper, zinc, chromium, titanium, and zirconium; 0≤x≤0.15), a content of the acid root in total quantity is 1,500 ppm at most, a content of the alkali metal in total quantity is 2,000 ppm at most, a peak intensity ratio (I(003)/I(104)) at (003) and (104) of X-ray diffraction attributed to hexagonal crystal is 1.4 at least. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a lithium / transition metal composite oxide useful for an electrode material of a lithium battery, a method for producing it industrially advantageously, and a lithium battery using the same.

  Lithium secondary batteries are rapidly spreading due to their high energy density and excellent charge / discharge cycle characteristics, and lithium cobalt oxide is most commonly used as the positive electrode active material for lithium secondary batteries. . However, since cobalt resources are scarce and expensive, in recent years, lithium and transition metal composites that combine cobalt with transition metals such as nickel, manganese, iron, copper, zinc, and chromium to reduce the amount of cobalt used. A compound in which the above transition metal is combined without using an oxide or cobalt has been proposed. Among them, the layered rock salt type lithium / transition metal composite oxide has a large discharge capacity and excellent cycle characteristics, and the layered rock salt type lithium / nickel / manganese / cobalt composite oxide has battery characteristics, safety and cost. Practical use is expected as a material with an excellent balance.

The lithium-nickel-manganese-cobalt composite oxide has a composition formula: Li [Li _x Co _y A _1-xy ] O ₂ (A represents [Mn _z Ni _1-z ], where 0 ≦ x ≦ 0. .16, 0.1 ≦ y ≦ 0.3, 0.4 ≦ z ≦ 0.65, Lix is included in the transition metal layer) (see Patent Document 1), composition formula: Li _a Mn _0.5-x Ni _0.5-y Co _{x + y} O ₂ (0.05 ≦ x <0.3, 0.05 ≦ y <0.3, −0.1 ≦ x−y ≦ 0.02, 0 <A <1.3, x + y <0.5, where M is an element other than Ni, Mn such as Co), and 2θ of powder X-ray diffraction using CuKα rays: 18.6 ± 1 ° (003 plane) The relative intensity ratio of the diffraction peak at 2θ: 44.1 ± 1 ° (104 plane) with respect to the diffraction peak in FIG. Patent Document reference 2) it is known.

Japanese Patent No. 3571671 WO2002 / 086993

  In the lithium-nickel-manganese-cobalt composite oxide described in Patent Documents 1 and 2, the discharge is reduced when the cobalt content is reduced to the same level as nickel or manganese, or even less than nickel or manganese. The capacity and rate characteristics are not sufficient. Therefore, an object of the present invention is to provide a lithium / nickel / manganese / cobalt composite oxide having a large discharge capacity and excellent rate characteristics even when the cobalt content is reduced, and a method for producing the same.

  As a result of intensive studies to solve the above problems, the present inventors have found that lithium / transition metal composite oxides having a low content of acidic roots and alkali metals, a layered rock salt type and good crystallinity have a discharge capacity. The lithium / nickel / manganese / cobalt composite oxide not only has a high discharge capacity, but the cobalt content, which is usually disadvantageous for the rate characteristics, is not limited to nickel or manganese. It has been found that excellent rate characteristics are exhibited even with compositions of the same amount or less. In addition, by leaching the transition metal carbonate used as a raw material with a basic aqueous solution, the content of acidic roots and alkali metals can be reduced. Furthermore, this transition metal carbonate is highly reactive with water-soluble lithium compounds in aqueous systems. Therefore, the precursor composition obtained by the reaction with lithium found that a homogeneous lithium / transition metal composite oxide having high crystallinity can be easily obtained by heating and baking, and completed the present invention.

That is, the present invention relates to Li _{1 + x} M _1-x O ₂ (M is at least one transition metal selected from nickel, manganese, cobalt, iron, copper, zinc, chromium, titanium, zirconium, 0 ≦ x ≦ 0.15). Is a layered rock salt type lithium-transition metal composite oxide represented by the formula (1), wherein the total content of acidic roots is at most 1500 ppm, and the total content of alkali metals is at most 2000 ppm. The lithium / transition metal composite oxide has a peak intensity ratio (I ₍₀₀₃₎ / I ₍₁₀₄₎ ) of (003) and (104) of X-ray diffraction of at least 1.4. Furthermore, the present invention is a method for producing the above-mentioned lithium / transition metal composite oxide, which comprises at least one transition metal selected from nickel, manganese, cobalt, iron, copper, zinc, chromium, titanium, and zirconium. The first step of leaching a metal carbonate with a basic aqueous solution, filtering, and then washing with pure water to obtain a leaching treatment transition metal carbonate, the leaching treatment transition metal carbonate and a water-soluble lithium compound in an aqueous system The second step of obtaining a lithium / transition metal composite oxide precursor composition by solid-liquid separation after reacting in a liquid medium, heating and firing the precursor composition to form a lithium / transition metal composite oxide A method for producing a lithium / transition metal composite oxide, comprising the third step of obtaining.

  The lithium / transition metal composite oxide of the present invention has a high discharge capacity and excellent rate characteristics. In particular, the lithium-nickel-manganese-cobalt composite oxide of the present invention is inexpensive because it contains a small amount of cobalt. In addition to having a large discharge capacity as described above, the content of cobalt is low. Nevertheless, since the rate characteristics are excellent, when this is used as an electrode active material, a high-power lithium battery can be obtained. In addition, the production method of the present invention advantageously produces a lithium / transition metal composite oxide having a low content of acidic roots and alkali metals, and having a high crystallinity and a homogeneous lithium / transition metal composite.

6 is an X-ray diffraction chart of a precursor composition (Sample e) of Example 5. FIG. It is an X-ray diffraction chart of Example 5 (sample E). It is an X-ray-diffraction chart of the comparative example 6 (sample S).

The present invention is a layered rock salt type lithium / transition metal composite oxide, wherein Li _{1 + x} M _1-x O ₂ (M is at least selected from nickel, manganese, cobalt, iron, copper, zinc, chromium, titanium, zirconium) A kind of transition metal, 0 ≦ x ≦ 0.15), the total content of acidic roots is at most 1500 ppm, the total content of alkali metals is at most 2000 ppm, and X belonging to hexagonal crystals The peak intensity ratio (I ₍₀₀₃₎ / I ₍₁₀₄₎ ) of (003) and (104) of the line diffraction is at least 1.4. If a large amount of acidic roots and alkali metals are present, it is considered that the battery characteristics, particularly the discharge capacity, are hindered. In the present invention, since the contents of acidic roots and alkali metals are small as described above, the discharge capacity is high. On the other hand, in the present invention in which the crystal structure is a layered rock salt type, the peak intensities of (003) and (104) of X-ray diffraction attributed to hexagonal crystals are I ₍₀₀₃₎ and I ₍₁₀₄₎ , respectively. The peak intensity ratio (I ₍₀₀₃₎ / I ₍₁₀₄₎ ) of at least 1.4 indicates that the crystallinity is excellent and the layered structure is highly developed. Therefore, the lithium / transition metal composite oxide of the present invention has excellent rate characteristics. In the present invention, the acidic root means a sulfate group (SO ₃ ) and a chlorine group (Cl), and the total amount thereof is at most 1500 ppm, preferably at most 1000 ppm. In the present invention, the alkali metal means sodium and potassium, and the total amount thereof is at most 2000 ppm, preferably 1500 ppm. Further, the peak intensity ratio is more preferably at least 1.5.

  The transition metal M constituting the lithium-transition metal composite oxide of the present invention is nickel, manganese, cobalt, iron, copper, zinc, chromium, titanium, zirconium, or one kind or two or more kinds. The combination of transition metal species is not particularly limited as long as it is two or more species. Among these, composite oxides in which at least one transition metal is nickel are preferable because they exhibit characteristic battery characteristics. Examples include lithium / nickel / manganese composite oxides, lithium / nickel / cobalt composite oxides, lithium / nickel / manganese / cobalt composite oxides, and lithium / nickel / manganese / cobalt / titanium composite oxides.

In particular, a lithium / nickel / manganese / cobalt composite oxide is a preferable lithium / transition metal composite oxide because of its excellent balance of battery characteristics, safety, and cost. In general, in the layered rock salt type lithium / nickel / manganese / cobalt composite oxide, the valence of nickel is considered to be divalent or trivalent. Since divalent nickel and lithium have similar ionic radii, so-called cation mixing in which nickel is mixed into the lithium layer is likely to occur. It is said that the irregularity of the layered structure due to cation mixing is more likely to occur when the cobalt content is low. It is presumed that nickel mixed in the lithium layer inhibits lithium insertion / extraction during the charge / discharge reaction and deteriorates the rate characteristics. In the present invention, in particular, the composition of the transition metal M is Ni _{(1-y + z) / 2} Mn _{(1-yz) / 2} Co _y (0 <y ≦ 0.35, −0.05 ≦ z ≦ 0. The lithium / nickel / manganese / cobalt composite oxide represented by (05) not only has a high discharge capacity as described above, but also has a cobalt content equal to or less than that of nickel or manganese. It is presumed that there is little or very little irregularity of the layered structure due to cation mixing, and it has excellent rate characteristics. Further, when the cobalt content is low, it is preferable to use titanium as a transition metal and to make a lithium / nickel / manganese / cobalt / titanium composite oxide because thermal stability and rate characteristics are improved. Among them, Ni _(1- wy _{+ z) / 2} Mn _{(1-w-yz) / 2} Co _y Ti _w (0 <w ≦ 0.1, 0 ≦ y ≦ 0.35, −0.05 ≦ The composition of z ≦ 0.05) is more preferable.

  In the present invention, for the purpose of improving battery characteristics, different elements other than lithium and the transition metal can be doped into the crystal lattice within a range that does not inhibit the crystallinity (peak intensity ratio). . Examples of the different element include Al for the purpose of improving the thermal stability, and Mg, Ca, Al, B and the like for the purpose of improving the cycle characteristics. Alternatively, these different elements can be coated on the particle surface of the composite oxide in the form of an oxide, a composite oxide or the like.

  Next, the present invention relates to a method for producing a lithium / transition metal composite oxide, which comprises at least one transition metal selected from nickel, manganese, cobalt, iron, copper, zinc, chromium, titanium, and zirconium. The first step of leaching the carbonate with a basic aqueous solution, filtering, and then washing with pure water to obtain a leaching treated transition metal carbonate, the leaching treated transition metal carbonate and the water-soluble lithium compound in an aqueous medium. The second step of obtaining a lithium / transition metal composite oxide precursor composition by solid-liquid separation after reacting in the liquid, and heating and firing the precursor composition to obtain a lithium / transition metal composite oxide A third step is included. According to the present invention, a lithium / transition metal composite oxide having a low content of acidic roots and alkali metals, excellent crystallinity, and a highly developed layered structure can be obtained.

  First, in the first step, a transition metal carbonate containing at least one transition metal selected from nickel, manganese, cobalt, iron, copper, zinc, chromium, titanium, and zirconium is leached with a basic aqueous solution and filtered. Thereafter, it is washed with pure water to obtain a leaching-treated transition metal carbonate. The transition metal carbonate used in the first step is at least one selected from nickel ions, manganese ions, cobalt ions, iron ions, copper ions, zinc ions, chromium ions, titanium ions and zirconium ions in an aqueous medium. These transition metal ions can be obtained by reacting at least with carbonate ions. As a method of reacting with carbonate ions, (1) water-soluble nickel compound, water-soluble manganese compound, water-soluble cobalt compound, water-soluble iron compound, water-soluble copper compound, water-soluble zinc compound, water-soluble chromium compound, water-soluble titanium A method of neutralizing at least one water-soluble transition metal compound selected from a compound and a water-soluble zirconium compound with a basic compound containing a basic carbonate compound in an aqueous medium, or (2) a water-soluble nickel compound or water At least one water-soluble transition metal compound selected from water-soluble manganese compounds, water-soluble cobalt compounds, water-soluble iron compounds, water-soluble copper compounds, water-soluble zinc compounds, water-soluble chromium compounds, water-soluble titanium compounds and water-soluble zirconium compounds A method of neutralizing with a basic compound while blowing carbon dioxide in an aqueous medium is preferable. Examples of the water-soluble compounds of the transition metal used include these sulfates, chlorides, nitrates, etc., and basic carbonate compounds include sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, ammonium carbonate, hydrogen carbonate. Ammonium etc. are mentioned. In addition to the basic carbonic acid compound, a basic hydroxide may be used in combination as the basic compound used in the method (1). In that case, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide can be used as the basic hydroxide. Examples of the basic compound used in the method (2) include a basic carbonate compound, a basic hydroxide, and the like. In particular, when a basic carbonate compound is used in combination with carbon dioxide, a heavy complex carbonate is formed. This is preferable.

  In the method of (1), the reaction between the water-soluble compound of the transition metal and the basic compound containing the basic carbonate compound is performed by using the water-soluble compound of the transition metal as a mixed aqueous solution. An aqueous solution of a basic compound containing a compound may be added or vice versa, or the mixed aqueous solution and an aqueous solution of a basic compound containing a basic carbonate compound may be added in parallel to an aqueous medium. You may go. Also in the method (2), even if an aqueous solution of a basic compound containing a basic hydroxide is added to the mixed aqueous solution while aeration of carbon dioxide gas, the basic hydroxide is conversely changed. The mixed aqueous solution may be added to the aqueous solution of the basic compound containing the carbon dioxide gas, or the mixed aqueous solution and the basic hydroxide may be added to the aqueous medium solution while the carbon dioxide gas is bubbled. You may carry out by adding in parallel with the aqueous solution of the basic compound to contain. In particular, in any of the methods (1) and (2), when the parallel addition is performed, it is easy to obtain a composite carbonate having a uniform particle size distribution, and when this is used, a lithium / transition metal composite oxide having excellent battery characteristics. Is easy to obtain. When the parallel addition is gradually performed over 1 to 20 hours, a product having a more uniform particle size distribution is easily obtained, and the range of 3 to 12 hours is more preferable. In any method, the reaction temperature is preferably in the range of 0 to 90 ° C., because the reaction easily proceeds, and the range of 15 to 80 ° C. is more preferable. The basic carbonic acid compound in the method (1) is preferably used in the range of neutralization equivalent to 2.5-fold equivalent of the water-soluble compound of the transition metal. When a basic hydroxide is used in combination, it is preferable to use an amount equal to or less than that of the basic carbonate compound. When the amount of the basic hydroxide used is more than the same amount as the basic carbonate compound, the transition metal hydroxide is easily produced as a by-product in addition to the complex carbonate. In the method (2), the basic compound is preferably used in the range of neutralization equivalent to double equivalent, and the amount of carbon dioxide used is the stoichiometric amount or more required to form the complex carbonate. If so, there is no particular limitation.

  The blending ratio of the water-soluble transition metal compound can be appropriately set according to the composition of the target lithium / transition metal composite oxide.

  When the transition metal carbonate used in the first step is produced by the above method (1) or (2), the resulting transition metal carbonate contains nickel carbonate, manganese carbonate, cobalt carbonate when one transition metal is included. , Iron carbonate, copper carbonate, zinc carbonate, and chromium carbonate. When two or more kinds of transition metals are included, they are complex carbonates such as nickel, manganese, cobalt, iron, copper, zinc, chromium, titanium, and zirconium. Titanium and zirconium are not known as single carbonates, respectively, but it is considered that complex carbonates with other transition metals can be formed. These are all compounds having a hexagonal crystal structure, and can be confirmed by measuring powder X-ray diffraction.

The transition metal carbonate is leached with a basic aqueous solution, filtered, and then washed with pure water to obtain a leached transition metal carbonate. The content of acidic roots and alkali metals is reduced by leaching treatment. When the precursor composition described later contains a large amount of acidic root and alkali metal, a large amount of acidic root and alkali are also contained in the lithium / transition metal composite oxide obtained by heating and firing in the third step. Metal is included, which inhibits battery characteristics, particularly discharge capacity. Since complex carbonates do not easily form salts with acidic roots, and basic aqueous solutions have a high ability to remove acidic roots, in the present invention, by leaching the complex carbonates with basic aqueous solutions, acidic roots that have been difficult in the past have been difficult. Can be removed relatively easily, and the alkali metal is removed by washing with pure water. Examples of the basic aqueous solution include alkali metal carbonates such as sodium carbonate and potassium carbonate, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and aqueous solutions such as ammonia. Oxides are preferred because of their good cleaning properties. In the leaching of the composite carbonate, the transition metal may be filtered and washed with a basic aqueous solution. Is preferably adjusted to the range of 8 to 11.5, more preferably 8.5 to 11, so that the content of acidic roots can be easily reduced. When the pH is 8 or less, it is difficult to reduce acidic roots. When the pH is 11.5 or more, the amount of the basic aqueous solution used is excessive, and it is difficult to remove the alkaline component even if washed with water. After adding the basic aqueous solution, it is preferable to hold for a certain period of time, for example, by stirring for about 10 minutes to 2 hours. The acidic root is SO ₃ or Cl derived from the water-soluble compound of the transition metal as a starting material, and the alkali metal is derived from a basic carbonate compound or a neutralizing agent, and is substantially sodium and potassium. In the first step, when the basic aqueous solution leaching and pure water washing are performed so that the total content of acidic roots in the composite carbonate is at most 2000 ppm and the total content of alkali metals is at most 3000 ppm preferable.

  Next, in the second step, the leaching-treated transition metal carbonate and the water-soluble lithium compound are reacted in an aqueous medium, followed by solid-liquid separation to obtain a lithium / transition metal composite oxide precursor composition. obtain. Since the leaching treatment transition metal carbonate obtained in the first step is rich in reactivity with the water-soluble lithium compound, there is no particular limitation as long as the reaction temperature is less than 100 ° C. at which the reaction can be performed at normal pressure. Although it sets suitably according to the kind of metal element, the temperature of the range of room temperature or more and less than 90 degreeC is preferable normally, and the range of room temperature or more and 60 degrees C or less is still more preferable. Examples of the water-soluble lithium compound include lithium hydroxide, lithium nitrate, lithium sulfate and the like. Among them, lithium hydroxide is excellent in reactivity with the leaching-treated transition metal carbonate, and it is preferable to use this. What is necessary is just to set the addition amount of a water-soluble lithium compound to the quantity corresponding to 1.0-1.4 by molar ratio with respect to the total amount of the said transition metal in which Li component is contained in transition metal carbonate. The reaction between the leaching treatment transition metal carbonate and the water-soluble lithium compound is such that the carbonate component contained in the transition metal carbonate reacts with lithium contained in the lithium compound to produce lithium carbonate, while the transition metal However, the precursor composition is a composition containing these lithium carbonate and transition metal hydroxide, and can be confirmed by measuring powder X-ray diffraction. .

  After the reaction, the obtained precursor composition is filtered off. In this invention, while separating a precursor composition into solid and liquid by filtration, the acidic root and alkali metal which remain | survive after a 1st process can be removed, and these content can be reduced further. A known filtration device can be used for the filtration, and there is no particular limitation, but a roll press, a filter press and the like are preferable industrially. However, it is not preferable to perform washing or leaching during or after the filtration because lithium is easily eluted from the precursor composition. The total amount of acidic roots in the precursor composition is preferably at most 1500 ppm, and the total content of alkali metals is preferably at most 2000 ppm, more preferably at most 1000 ppm and 1500 ppm, respectively. It is preferable to dry after filtration and to use for the following 3rd process.

  The contents of acidic root and alkali metal in the leaching-treated transition metal carbonate and precursor composition were measured after drying them at a temperature of 120 ° C. for 5 hours.

In the third step, the precursor composition obtained in the second step is heated and fired to obtain a lithium / transition metal composite oxide. The heating and baking temperature is preferably in the range of approximately 700 to 1100 ° C. In order to prevent the sintering of the particles, it is preferable to set the temperature to 1000 ° C. or lower, and thus a more preferable heating and baking temperature is in the range of 700 to 1000 ° C. The heating time may be 1 to 20 hours, and more preferably 3 to 10 hours. Conversion to a composite oxide proceeds homogeneously by heating and firing, and it becomes easy to obtain a lithium / transition metal composite oxide having very high crystallinity and a layered structure. For example, if it has a layered rock salt type crystal structure, the peak intensities of (003) and (104) of X-ray diffraction attributed to hexagonal crystals are I ₍₀₀₃₎ and I ₍₁₀₄₎ , respectively. The ratio (I ₍₀₀₃₎ / I ₍₁₀₄₎ ) is at least 1.4, preferably 1.5 or more. If the obtained composite oxide is sintered and agglomerated after heating and firing, it may be pulverized using a flake crusher, a hammer mill, a pin mill, or the like, if necessary.

  In order to dope different elements other than lithium and the transition metal into the crystal lattice, for example, a known method such as heating and firing after depositing a compound of a different metal on the surface of the composite oxide may be used. . Or you may add the water-soluble compound of a different element in the 1st or 3rd process of this invention.

Furthermore, the present invention is a lithium battery, wherein the lithium / transition metal composite oxide is used as a positive electrode active material. The positive electrode for a lithium battery is obtained by adding a conductive material such as carbon black and a binder such as a fluororesin to the composite oxide, and appropriately molding or applying it. The lithium battery is composed of the positive electrode, the negative electrode, and the electrolytic solution. As the negative electrode material, metallic lithium, lithium alloy or the like, or carbon-based material such as graphite or coke is used. In addition, the electrolyte includes a solvent such as propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, dimethyl carbonate, diethyl carbonate, LiPF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , Conventional materials such as those in which a lithium salt such as LiBF ₄ is dissolved can be used.

  Examples of the present invention are shown below, but these do not limit the present invention.

Example 1
(First step)
Preparation of transition metal carbonate 700 ml of a mixed aqueous solution of nickel sulfate, manganese sulfate and cobalt sulfate (0.7 mol each in terms of nickel ion, manganese ion and cobalt ion) and an aqueous potassium hydrogen carbonate solution (4.72 in terms of carbonate ion) Mole) 1575 ml of pure water at a temperature of 70 ° C., neutralized by adding in parallel over 10 hours with stirring while maintaining the temperature, filtered and then washed with pure water. Got.

Complex carbonate basic aqueous solution leaching and washing Filtered and washed composite carbonate is dispersed in pure water to make a 400 ml slurry, and potassium carbonate aqueous solution is added to adjust the pH of the slurry to 9, 1 hour After stirring, it was filtered again and washed with pure water. In addition, as an acidic root contained in this composite carbonate, SO ₃ was 1710 ppm, and as an alkali metal, sodium was 150 ppm and potassium was 100 ppm.

(Second step: Preparation of precursor composition)
A leaching / water-washed composite carbonate equivalent to 100 g in terms of the total amount of nickel, manganese and cobalt was dispersed in pure water to form a 400 milliliter slurry. While stirring the slurry, 83 g of lithium hydroxide (monohydrate) was added at room temperature and normal pressure, stirred for 1 hour, filtered and dried to obtain a precursor composition. Note that the SO ₃ as the acidic roots included in the precursor composition 800 ppm, sodium as the alkali metal is 120 ppm, potassium was 70 ppm.

(Third step: Heat firing of the precursor composition)
The precursor composition was heated and fired at 900 ° C. in the atmosphere for 10 hours to obtain the lithium / nickel / manganese / cobalt composite oxide (sample A) of the present invention.

Example 2
In the first step, the lithium / nickel / manganese / cobalt composite oxidation of the present invention was performed in the same manner as in Example 1 except that the pH was adjusted to 10 using sodium hydroxide instead of potassium carbonate. A product (sample B) was obtained. The acidic root contained in the precursor composition was 500 ppm of SO ₃ , and the alkali metal component was 90 ppm of sodium and 10 ppm of potassium.

Example 3
(First step)
Preparation of transition metal carbonate A mixed aqueous solution of nickel sulfate, manganese sulfate and cobalt sulfate (nickel ion, manganese ion and manganese ion) while blowing carbon dioxide at a flow rate of 1 liter per minute into 500 ml of pure water at a temperature of 70 ° C. Neutralize by adding 800 ml of each 0.8 mol in terms of cobalt ion) and 1000 ml of aqueous sodium carbonate solution (3.2 mol in terms of carbonate ion) in parallel over 10 hours while maintaining the temperature. After filtration, it was washed with pure water to obtain a composite carbonate.

Complex carbonate basic aqueous solution leaching and washing Filtered and washed composite carbonate is dispersed in pure water to make a 500 ml slurry, and an aqueous sodium carbonate solution is added to adjust the pH of the slurry to 9 for 1 hour. After stirring, it was filtered again and washed with pure water. The acidic root contained in this composite carbonate was 810 ppm for SO ₃ , and 2890 ppm for sodium and 20 ppm for potassium as the alkali metal.

(Second step: Preparation of precursor composition)
A leaching / water-washed composite carbonate equivalent to 100 g in terms of the total amount of nickel, manganese and cobalt was dispersed in pure water to give a 500 milliliter slurry. While stirring this slurry, 85 g of lithium hydroxide (monohydrate) was added at room temperature and normal pressure and stirred for 1 hour, followed by filtration and drying to obtain a precursor composition. The acidic root contained in the precursor composition was 10 ppm SO ₃ , and the alkali metal was 1350 ppm sodium and 10 ppm potassium.

(Third step: Heat firing of the precursor composition)
The precursor composition was fired at 900 ° C. for 10 hours in the atmosphere to obtain a lithium / nickel / manganese / cobalt composite oxide (sample C) of the present invention.

Example 4
In the first step, the lithium / nickel / manganese / cobalt composite oxide of the present invention (in the same manner as in Example 3 except that the temperature of pure water was 25 ° C. and the temperature during parallel addition was also maintained at 25 ° C.) Sample D) was obtained. Note that the SO ₃ as the acidic roots included in the precursor composition 630 ppm, sodium as the alkali metal is 1250 ppm, the potassium was 10 ppm.

Example 5
In preparation of the transition metal carbonate in the first step, nickel ions, manganese ions, and cobalt ions in a mixed aqueous solution of nickel sulfate, manganese sulfate, and cobalt sulfate were added to 0.875, 0.875, and 0.35 mol, respectively. Except for the above, a lithium / nickel / manganese / cobalt composite oxide (sample E) of the present invention was obtained in the same manner as in Example 1. Note that the SO ₃ as the acidic roots included in the precursor composition (Sample e) 530 ppm, sodium 100 ppm, potassium was 40ppm as alkali metal.

Example 6
In the preparation of the transition metal carbonate in the first step, nickel ion, cobalt ion and manganese ion in the mixed aqueous solution of nickel sulfate, manganese sulfate and cobalt sulfate were respectively 1.0, 1.0 and 0.4 mol. Except for the above, a lithium / nickel / manganese / cobalt composite oxide (sample F) of the present invention was obtained in the same manner as in Example 3. The acidic root contained in the precursor composition was 420 ppm SO ₃ , and the alkali metal was 1260 ppm sodium and 10 ppm potassium.

Example 7
In the preparation of the transition metal carbonate in the first step, nickel ion, manganese ion, and cobalt ion in the mixed aqueous solution of nickel sulfate, manganese sulfate, and cobalt sulfate are respectively 1.0, 1.0, and 0.4 mol. The lithium / nickel / manganese / cobalt composite oxide of the present invention (sample G) was used in the same manner as in Example 3 except that sodium hydroxide was used instead of sodium carbonate in the leaching and the pH was adjusted to 10. Got. The acidic root contained in the precursor composition was 330 ppm of SO ₃ , and the alkali was 590 ppm of sodium and 10 ppm of potassium.

Example 8
In the preparation of the transition metal carbonate in the first step, a mixed aqueous solution of nickel chloride, manganese chloride, and cobalt chloride was used instead of the mixed aqueous solution of nickel sulfate, manganese sulfate, and cobalt sulfate. The lithium / nickel of the present invention was prepared in the same manner as in Example 3, except that the ions and cobalt ions were 1.0, 1.0, and 0.4 mol, respectively, and potassium carbonate was used instead of sodium carbonate in leaching. -Manganese-cobalt composite oxide (sample H) was obtained. The acidic root contained in the precursor composition was 130 ppm for Cl, 10 ppm for SO ₃ , 80 ppm for alkali metal, and 20 ppm for potassium.

Example 9
In the preparation of the transition metal carbonate in the first step, nickel ion, manganese ion, and cobalt ion in the mixed aqueous solution of nickel sulfate, manganese sulfate, and cobalt sulfate were 1.15, 1.15, and 0.1 mol, respectively. A lithium / nickel / manganese / cobalt composite oxide (sample I) of the present invention was obtained in the same manner as in Example 3 except that. The acidic root contained in the precursor composition was 160 ppm of SO ₃ , and the alkali metal was 1100 ppm of sodium and 10 ppm of potassium.

Example 10
In the preparation of the transition metal carbonate in the first step, the nickel ion, manganese ion, and cobalt ion in the mixed aqueous solution of nickel sulfate, manganese sulfate, and cobalt sulfate were 1.15, 1.15, and 0.1 mol, respectively. The lithium / nickel / manganese / cobalt composite oxide (Sample J) of the present invention was prepared in the same manner as in Example 3 except that sodium hydroxide was used instead of sodium carbonate in the leaching and the pH was adjusted to 10. Obtained. The acidic root contained in the precursor composition was 140 ppm of SO ₃ , and the alkali metal was 630 ppm of sodium and 10 ppm of potassium.

Example 11
In the preparation of the transition metal carbonate in the first step, a mixed aqueous solution of nickel chloride, manganese chloride, and cobalt chloride was used instead of the mixed aqueous solution of nickel sulfate, manganese sulfate, and cobalt sulfate. The lithium, nickel, and nickel ions of the present invention were prepared in the same manner as in Example 3, except that the ions and cobalt ions were 1.15, 1.15, and 0.1 mol, respectively, and potassium carbonate was used instead of sodium carbonate in leaching. Manganese / cobalt composite oxide (sample K) was obtained. The acidic root contained in the precursor composition was 60 ppm for Cl, 20 ppm for SO ₃ , and 110 ppm for sodium and 40 ppm for potassium as the alkali metal.

Example 12
In the first step, a mixed aqueous solution of nickel chloride, manganese chloride, and cobalt chloride is used instead of the mixed aqueous solution of nickel sulfate, manganese sulfate, and cobalt sulfate, and the nickel ion, manganese ion, and cobalt ion in the aqueous solution are each 1. 15, 1.15, 0.1 mol, except that pure water temperature was 25 ° C. and the temperature during parallel addition was maintained at 25 ° C., and potassium carbonate was used instead of sodium carbonate in leaching. In the same manner as in Example 3, the lithium-nickel-manganese-cobalt composite oxide (sample L) of the present invention was obtained. The acidic root contained in the precursor composition was 50 ppm for Cl, 20 ppm for SO ₃ , and 90 ppm for sodium and 20 ppm for potassium as the alkali metal.

Example 13
In the first step, a mixed aqueous solution of nickel chloride, manganese chloride, cobalt chloride and titanium tetrachloride is used in place of the mixed aqueous solution of nickel sulfate, manganese sulfate and cobalt sulfate, and nickel ion, manganese ion and cobalt ion in the aqueous solution are used. In the same manner as in Example 3, except that the titanium ions were 1.14, 1.14, 0.1, and 0.02 mol, respectively, and potassium carbonate was used instead of sodium carbonate in the leaching, the lithium of the present invention was used. Nickel / manganese / cobalt / titanium composite oxide (sample M) was obtained. The acidic root contained in the precursor composition was Cl of 60 ppm, SO ₃ of 10 ppm, and the alkali metal was 100 ppm of sodium and 20 ppm of potassium.

Comparative Example 1
A lithium / nickel / manganese / cobalt composite oxide (sample N) was obtained in the same manner as in Example 3 except that leaching was not performed. The acidic root contained in the composite carbonate is 2540 ppm of SO ₃ , the alkali metal is 8100 ppm of sodium and 70 ppm of potassium, the precursor composition contains SO ₃ of 840 ppm, sodium of 4500 ppm and potassium of 40 ppm. Met.

Comparative Example 2
800 ml of a mixed aqueous solution of nickel sulfate, manganese sulfate and cobalt sulfate (each 0.8 in terms of nickel ion, manganese ion and cobalt ion) and 1000 ml of an aqueous sodium hydroxide solution (6.2 mol in terms of hydroxide ion) In 600 ml of pure water at a temperature of 50 ° C., neutralize by adding in parallel over 6 hours while maintaining the temperature, filter, wash with pure water, and dry to obtain a composite hydroxide. It was. This composite hydroxide contained 4230 ppm of SO3 as an acidic root and 2200 ppm of sodium as an alkali metal. 42 g of lithium hydroxide (monohydrate) is mixed with a composite hydroxide equivalent to 50 g in terms of the total amount of nickel, manganese and cobalt using a sample mill, and this mixture is heated and fired at 900 ° C. in the atmosphere for 10 hours. As a result, a lithium / nickel / manganese / cobalt composite oxide (sample O) was obtained.

Comparative Example 3
Lithium / nickel / manganese / cobalt composite oxide in the same manner as in Comparative Example 2, except that a lithium hydroxide aqueous solution was used instead of the sodium hydroxide aqueous solution, and the amount added was 6.2 mol in terms of hydroxide ion. (Sample P) was obtained. As a reference, this composite hydroxide contained 14040 ppm of SO ₃ as an acidic root.

Comparative Example 4
The nickel ion, manganese ion, and cobalt ion in the mixed aqueous solution of nickel sulfate, manganese sulfate, and cobalt sulfate are 1.0, 1.0, and 0.4 mol, respectively. Instead of the sodium hydroxide aqueous solution, the lithium hydroxide aqueous solution is used. A lithium / nickel / manganese / cobalt composite oxide (sample Q) was obtained in the same manner as in Comparative Example 2 except that the amount used was 6.2 mol in terms of hydroxide ion. As a reference, this composite hydroxide contained 13400 ppm of SO ₃ as an acidic root.

Comparative Example 5
The nickel ion, manganese ion, and cobalt ion in the mixed aqueous solution of nickel sulfate, manganese sulfate, and cobalt sulfate are 1.15, 1.15, and 0.1 mol, respectively. Instead of the sodium hydroxide aqueous solution, the lithium hydroxide aqueous solution is used. A lithium / nickel / manganese / cobalt composite oxide (sample R) was obtained in the same manner as in Comparative Example 2 except that the amount used was 6.2 mol in terms of hydroxide ion. As a reference, this composite hydroxide contained 12300 ppm of SO3 as an acidic root.

Comparative Example 6
The transition metal carbonate obtained in Example 4 was used in an amount corresponding to 50 g in terms of the total amount of nickel, manganese and cobalt, and 37 g of lithium carbonate was mixed using a sample mill, and the mixture was mixed in the atmosphere. Lithium / nickel / manganese / cobalt composite oxide (Sample S) was obtained by heating and firing at 900 ° C. for 10 hours.

Evaluation 1: Content of acidic root and alkali metal, measurement of I ₍₀₀₃₎ / I ₍₁₀₄₎ value Chemical composition of samples A to S of Examples 1 to 13 and Comparative Examples 1 to 6, of acidic root and alkali metal The content is shown in Table 1. The powder X-ray diffraction (X-ray: Cu-Kα) of these samples was measured, and from this X-ray diffraction chart, the intensities of peaks (003) and (104) belonging to hexagonal crystals I ₍₀₀₃₎ , I ₍₁₀₄₎ reads, shows the result of calculating the intensity ratio _{(I (003) / I (104))} in Table 1. In the lithium / nickel / manganese / cobalt composite oxide of the present invention, the total content of acidic roots is 1500 ppm or less, the content of alkali metal components is 2000 ppm or less in total, I ₍₀₀₃₎ / I ₍₁₀₄₎ Is 1.5 or more.

Evaluation 2: Evaluation of charge / discharge characteristics and rate characteristics Lithium secondary battery using lithium / transition metal composite oxides (samples A to S) obtained in Examples 1 to 13 and Comparative Examples 1 to 6 as a positive electrode active material The charge / discharge capacity and rate characteristics were evaluated. The battery configuration and measurement conditions will be described.

  Samples A to S, acetylene black powder as a conductive agent, and polyvinylidene fluoride powder as a binder were kneaded in N-methyl-2-pyrrolidone, and the sample, the conductive agent, and the binder were 100 by weight. A paste mixed at a ratio of 10:10 was prepared. This paste was applied onto an aluminum foil, desolvated at 120 ° C., punched into a circle with a diameter of 10 mm, and pressed at 14.7 MPa to obtain a working electrode.

This working electrode was vacuum-dried at 120 ° C. for 4 hours and then incorporated as a positive electrode in a sealable coin-type evaluation cell in a glove box having a dew point of −70 ° C. or lower. The evaluation cell used was made of stainless steel (SUS316) and had an outer diameter of 20 mm and a height of 3.2 mm. As the negative electrode, a metal lithium having a thickness of 0.5 mm formed into a circle having a diameter of 14 mm was used. As the non-aqueous electrolyte, a mixed solution of ethylene carbonate and dimethyl carbonate (mixed in a volume ratio of 1: 2) in which LiPF ₆ was dissolved at a concentration of 1 mol / liter was used.

  The positive electrode was placed in the lower can of the evaluation cell, a porous polypropylene film was placed thereon as a separator, and a non-aqueous electrolyte was dropped from above with a dropper. Further, a negative electrode and a 0.5 mm thick spacer for adjusting the thickness and a spring (both made of SUS316) were put thereon, and an upper can with a propylene gasket was put on and the outer peripheral edge portion was caulked and sealed.

When the voltage range is set to 2.5 V to 4.3 V, the charging current is 40 mA / g, the discharging current is 40 mA / g, the discharging capacity C ₁ , the charging current is 40 mA / g, and the discharging current is 320 mA / g. The discharge capacity C ₂ was measured, C ₁ was the discharge capacity, and (C ₂ / C ₁ ) × 100 (%) (capacity maintenance ratio) was the rate characteristic.

  Table 2 shows the discharge capacities and capacity retention rates of Samples A to S. It can be seen that the lithium / nickel / manganese / cobalt composite oxide of the present invention has a high discharge capacity and excellent rate characteristics, and particularly shows good load characteristics even in a sample having a low cobalt content.

  The lithium-transition metal of the present invention, particularly lithium-nickel-manganese-cobalt composite oxide, is excellent in rate characteristics and is particularly useful for a high-capacity lithium battery.

Claims (4)

Li _{1 + x} M _1−x O ₂ (M is at least one transition metal selected from nickel, manganese, cobalt, iron, copper, zinc, chromium, titanium, zirconium, 0 ≦ x ≦ 0.15) A rock salt type lithium / transition metal composite oxide having an acid radical content of at most 1500 ppm and an alkali metal content of at most 2000 ppm. 003) and (104) have a peak intensity ratio (I ₍₀₀₃₎ / I ₍₁₀₄₎ ) of at least 1.4. The transition metal M is Ni _{(1-y + z) / 2} Mn _{(1-y-z) / 2} Co _y (0 <y ≦ 0.35, −0.05 ≦ z ≦ 0.05), The lithium / transition metal composite oxide according to claim 1. The transition metal M is Ni _(1- wy _{+ z) / 2} Mn _(1- wyzy _{) / 2} Co _y Ti _w (0 <w ≦ 0.1, 0 ≦ y ≦ 0.35, −0. The lithium / transition metal composite oxide according to claim 1, wherein 05 ≦ z ≦ 0.05). A lithium battery using the lithium-transition metal composite oxide according to claim 1 as a positive electrode active material.

Images