JP2012216476A - Method for producing lithium transition metal compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a lithium transition metal compound for a lithium secondary battery, by which a large amount of lithium transition metal compounds can be stably produced.SOLUTION: In a method for producing a lithium transition metal compound using a multi-stage roll crusher, a lithium transition metal compound for a lithium secondary battery is pulverized while a gap between rolls of a first stage and a gap between rolls of a second stage are each set to be their respective specified gaps.

Description

  The present invention relates to a method for producing a lithium transition metal compound.

2. Description of the Related Art In recent years, with the reduction in size and weight of portable electronic devices and communication devices, lithium secondary batteries having high output and high energy density have attracted attention as power sources thereof and as power sources for automobiles.
Lithium transition metal compounds are known as positive electrode active materials for lithium secondary batteries. Among them, it is known that a lithium transition metal composite oxide such as LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ having a standard composition is preferable. Further, from the viewpoint of safety and raw material cost, LiNi _1-X Mn _X O _{2 in} which a part of the transition metal of these lithium transition metal composite oxides is substituted with another transition metal (where 0 ≦ X ≦ 1) , LiNi _{1-x′-y ′} Mn _{x ′} Co _{y ′} O ₂ (
However, lithium transition metal composite oxides having the same layered structure as LiCoO ₂ and LiNiO ₂ such as 0 ≦ X ′ ≦ 1, 0 ≦ Y ′ ≦ 1, 0 ≦ X ′ + Y ′ ≦ 1) have attracted attention.

  As a method for producing these lithium transition metal compounds, for example, a lithium raw material, a nickel raw material, a cobalt raw material, a manganese raw material, etc. are mixed in a dry method and baked, crushed, classified, a nickel raw material, a cobalt raw material, a manganese raw material, A slurry containing a small amount of a lithium raw material, if desired, and spray-dried into granules, and further dry-mixed with the lithium raw material so that the desired composition ratio is obtained, and calcined, crushed, classified, or A composite carbonate obtained by co-precipitation of nickel, cobalt, manganese, etc., for example, as a carbonate is calcined and decarboxylated, and the resulting granulate and lithium raw material are dry-mixed and then calcined, crushed and classified. Methods are used.

  As the application of lithium secondary batteries to portable devices and automobiles rapidly expands, it has been required to supply lithium secondary batteries stably. In order to stably supply a lithium secondary battery, it is necessary to stably produce a lithium transition metal compound used for the electrode. That is, among the above-described methods for producing a lithium transition metal compound, there is a demand for a production method that can stably produce a large amount of a lithium transition metal compound.

  In addition, lithium secondary batteries are required to have high performance such as high capacity and high output. In particular, in order to realize a high capacity, studies for thinning the electrode of the lithium secondary battery are being actively conducted. For this reason, the lithium transition metal compound used for the electrode needs to have a sharp particle size distribution. That is, among the above-described methods for producing a lithium transition metal composite oxide, there is a demand for a production method that can obtain a sharp particle size distribution when a lithium transition metal compound is used.

Furthermore, it is known that the inclusion of metallic foreign matter in the materials constituting lithium secondary batteries, especially the positive electrode active material, may lead to battery failure and further risk of battery ignition, etc. In the manufacturing process of the lithium transition metal compound which is the positive electrode active material, there is a demand for a manufacturing method in which no metallic foreign matter is mixed.
In Patent Document 1, in order to obtain a positive electrode material for a powdery lithium secondary battery that is effective for increasing the output of a lithium secondary battery, it is possible to prevent the incorporation of coarse particles and impurities using an airflow classifier such as a cyclone. Are listed.

Furthermore, Patent Document 2 describes a roll crusher that is difficult to rotate with any shape and size of raw material by providing multiple types of compression teeth and cutting teeth on the outer periphery of the roll crusher.
Patent Document 3 describes a discharge assist device for a roll crusher that assists the discharge of crushed materials such as concrete waste by a roll crusher provided with crushing teeth having a plurality of convex members and grooves on the outer periphery of the roll crusher. Has been.

JP 2004-311297 A JP 2001-334156 A JP 2004-66041 A

However, in the production methods of Patent Documents 2 and 3, the roll crusher is simply used in one stage, and the productivity of the invention of the present invention, which is crushed in two stages, is low because the crushing efficiency is low. I left a challenge.
Therefore, the subject of the present invention is to improve the productivity by making the first stage of crushing coarse crushing and finely crushing the second stage, improving the crushing efficiency in the transition metal compound production process. It is to provide a manufacturing method.

As a result of intensive studies to solve the above problems, the present inventors, in the process of pulverizing coarse particles in the method of producing a transition metal compound,
Having a crushing step of crushing the lithium transition metal composite oxide after firing using a roll crusher having two or more rolls;
The first step roll interval is 0.8-4 mm,
The present invention was completed by finding that the above problem can be solved by setting the second-stage roll interval to 0.3 to 1 mm.

That is, the gist of the present invention is as follows.
(1) In the method for producing a lithium transition metal composite oxide for a lithium secondary battery,
Having a crushing step of crushing the lithium transition metal composite oxide after firing using a roll crusher having two or more rolls;
The first step roll interval is 0.8-4 mm,
A method for producing a lithium transition metal composite oxide for a lithium secondary battery, wherein a second-stage roll interval is 0.3 to 1 mm.
(2) The method according to (1), wherein the roll is provided with a groove.
(3) The production method according to (1) or (2), further comprising a classification step using a pneumatic classifier after the pulverization step.
(4) The manufacturing method according to any one of (1) to (3), wherein the material of the roll is ceramic.

In the method for producing a transition metal compound, in the step of crushing coarse particles, there is a crushing step of crushing the fired lithium transition metal composite oxide using a roll crusher having two or more rolls. And
The first step roll interval is 0.8-4 mm,
It is in providing the manufacturing method which improves crushing efficiency and improves productivity in the manufacturing method of a transition metal type compound by making the roll space | interval of a 2nd step into 0.3-1 mm.

Schematic diagram of roll crusher

Hereinafter, embodiments of the present invention will be described in detail. However, the description of the constituent elements described below is an example (representative example) of an embodiment of the present invention, and the present invention is specified by these contents. is not.
<Lithium transition metal compound>
The use of the lithium transition metal compound produced by the method for producing a lithium transition metal compound of the present invention (hereinafter referred to as “the production method of the present invention” as appropriate) is not particularly limited, but according to the production method of the present invention, According to the production method of the present invention, since metal impurities are not mixed, it is preferably used for electronic materials such as display materials, dielectric materials, magnetic materials, semiconductor materials, superconducting materials, battery materials and the like. Among these, it is more preferable to use for battery materials. Examples of the battery material include a fuel cell material, a lithium primary battery material, and a lithium secondary battery material. Among these, it is more preferable to use for the negative electrode material or positive electrode material of a lithium secondary battery, and it is especially preferable to use for the positive electrode material of a lithium secondary battery.

Further, the lithium transition metal compound produced by the production method of the present invention is not particularly limited, but is a compound having a structure capable of desorbing and inserting Li ions, such as phosphate compounds, lithium transitions. Examples include metal complex oxides and sulfides.
In particular,
(1) Phosphorus having an olivine structure and generally represented by LiMePO ₄ (Me is at least one or more transition metals), specifically, LiFePO ₄ , LiCoPO ₄ , LiNiPO ₄ , LiMnPO _4, etc. Acid salt compounds,
(2) It has a spinel structure capable of three-dimensional diffusion of lithium ions and is generally expressed as LiMe ₂ O ₄ (Me is at least one transition metal), specifically, LiMn ₂ O ₄ , A lithium transition metal composite oxide having a spinel structure, such as LiCoMnO ₄ , LiNi _0.5 Mn _1.5 O ₄ , CoLiVO ₄ ,
(3) It has a layered structure that enables two-dimensional diffusion of lithium ions and is generally expressed as LiMeO ₂ (Me is at least one transition metal), specifically, LiCoO ₂ , LiNiO ₂ , _{LiNi 1-X Co X O 2} ( however, 0 ≦ X ≦ 1), LiNi 1-X'-Y 'Mn X' Co Y 'O 2 ( however, 0 ≦ X' ≦ 1,0 ≦ Y '≦ 1 , 0 ≦ X ′ + Y ′ ≦ 1), L
A layered structure including iNi _0.5 Mn _0.5 O ₂ , Li _1.2 Cr _0.4 Mn _0.4 O ₂ , Li _1.2 Cr _0.4 Ti _0.4 O ₂ , LiMnO _{2 and the} like. Lithium transition metal composite oxide having,
(4) Sulfides, for example, TiS ₂ or MoS ₂ having a two-dimensional layered structure, or a strong three-dimensional skeleton structure, and a general formula Me _{X ″} Mo ₆ S ₈ (where Me is Pb, Ag, Examples thereof include various transition metals including Cu, and a chevrel compound represented by 0 ≦ X ″ ≦ 1).

Among them, a lithium transition metal composite oxide having a spinel structure or a layered structure is preferable, and a lithium transition metal having a layered structure is preferable in that good battery characteristics can be obtained when used as a positive electrode active material for a lithium secondary battery. A composite oxide is particularly preferred.
<Crystal structure>
The lithium transition metal-based compound powder of the present invention preferably contains at least a lithium nickel manganese cobalt-based composite oxide having a layered structure and / or a lithium manganese-based composite oxide having a spinel structure as a main component. Among these, since the expansion and contraction of the crystal lattice is large and the effect of the present invention is remarkable, the main component is a lithium nickel manganese cobalt composite oxide having a layered structure. In the present invention, among lithium nickel manganese cobalt-based composite oxides, lithium nickel manganese-based composite oxides not including cobalt are also included in the term “lithium nickel manganese cobalt-based composite oxide”.

Here, the layered structure will be described in more detail. As a typical crystal system having a layered structure, there are those belonging to the α-NaFeO ₂ type such as LiCoO ₂ and LiNiO ₂ , which are hexagonal and have a space group due to their symmetry.

(Hereinafter referred to as “layered R (−3) m structure”).
However, the layered LiMeO ₂ is not limited to the layered R (−3) m structure. In addition to this, LiMnO ₂ called so-called layered Mn is an orthorhombic and space-group Pm2m layered compound, and Li ₂ MnO ₃ called so-called 213 phase is Li [Li _1/3 Mn _2/3 ]. O ₂ , which is a monoclinic space group C2 / m structure, is also a layered compound in which a Li layer, a [Li _1/3 Mn _2/3 ] layer, and an oxygen layer are stacked.
Furthermore, the spinel structure will be described in more detail. As a typical crystal system having a spinel structure, there is a crystal system belonging to the MgAl ₂ O ₄ type such as LiMn ₂ O ₄ , which is a cubic system, and because of its symmetry, the space group.

(Hereinafter sometimes referred to as “spinel-type Fd (−3) m structure”). However, the spinel type LiMeO ₄ is not limited to the spinel type Fd (−3) m structure. In addition, spinel type LiMeO ₄ belonging to a different space group (P4 ₃ 32) also exists.
<composition>
The lithium-containing transition metal compound powder of the present invention is preferably a lithium transition metal compound powder represented by the following composition formula (A) or (B). Further, in the layered compound, the amount of Mn eluted is relatively small compared to the spinel type compound, and the influence of Mn on the cycle characteristics is small. Therefore, the effect of the present invention appears as a clear difference. Therefore, the present invention is more preferably a lithium transition metal compound powder represented by the following composition formula (A).
1) In the case of a lithium transition metal compound powder represented by the following composition formula (A)
Li _{1 + x} MO ₂ (A)
However, x is usually 0 or more, preferably 0.01 or more, more preferably 0.02 or more, most preferably 0.03 or more, usually 0.5 or less, preferably 0.4 or less, more preferably 0.3. Hereinafter, it is most preferably 0.2 or less. M is an element composed of Ni and Mn, or Ni, Mn and Co, and the Mn / Ni molar ratio is usually 0.1 or more, preferably 0.3 or more, more preferably 0.5 or more, Preferably 0.6 or more, more preferably 0.7 or more, still more preferably 0.8 or more, most preferably 0.9 or more, usually 5 or less, preferably 4 or less, more preferably 3 or less, still more preferably 2.5 or less, most preferably 1.5 or less. The Ni / M molar ratio is usually 0 or more, preferably 0.01 or more, more preferably 0.02 or more, still more preferably 0.03 or more, most preferably 0.05 or more, usually 0.50 or less, preferably 0. .49 or less, more preferably 0.48 or less, still more preferably 0.
. 47 or less, most preferably 0.45 or less. The Co / M molar ratio is usually 0 or more, preferably 0.01 or more, more preferably 0.02 or more, still more preferably 0.03 or more, most preferably 0.05 or more, usually 0.50 or less, preferably 0. .40 or less, more preferably 0.30 or less, still more preferably 0.20 or less, and most preferably 0.15 or less. In addition, the rich portion of Li represented by x may be replaced with the transition metal site M.

In the composition formula (A), the atomic ratio of the oxygen amount is described as 2 for convenience, but there may be some non-stoichiometry. In the case of non-stoichiometry, the atomic ratio of oxygen is usually in the range of 2 ± 0.2, preferably in the range of 2 ± 0.15, more preferably in the range of 2 ± 0.12, and even more preferably 2 ± 0.10. And particularly preferably in the range of 2 ± 0.05.
In addition, the lithium transition metal-based compound powder of the present invention is preferably obtained by firing at a high temperature in an oxygen-containing gas atmosphere in order to increase the crystallinity of the positive electrode active material.

The lower limit of the firing temperature is usually 900 ° C. or higher, preferably 950 ° C. or higher, most preferably 1000 ° C. or higher, and usually 1300 ° C., in the lithium transition metal compound having the composition represented by the composition formula (A). The temperature is preferably 1250 ° C. or lower, most preferably 1200 ° C. or lower. If the firing temperature is too low, heterogeneous phases are mixed, and the lattice distortion increases without developing a crystal structure. Moreover, the specific surface area becomes too large. Conversely, if the firing temperature is too high, the primary particles grow excessively, sintering between the particles proceeds too much, and the specific surface area becomes too small.
2) A lithium transition metal compound represented by the following general formula (B).

_{Li [Li a M b Mn 2} -b-a] O 4 + δ ··· (B)
However, M is an element composed of at least one of transition metals selected from Ni, Cr, Fe, Co, Cu, Zr, Al and Mg, and among these, the charge / discharge capacity at a high potential is From the point of view, Ni is most preferable.
The value of b is usually 0.4 or more, preferably 0.425 or more, more preferably 0.45 or more, further preferably 0.475 or more, most preferably 0.49 or more, usually 0.6 or less, preferably 0. .575 or less, more preferably 0.55 or less, still more preferably 0.525 or less, and most preferably 0.51 or less.

If the value of b is in this range, the energy density per unit weight in the lithium transition metal compound is high, which is preferable.
The value of a is usually 0 or more, preferably 0.01 or more, more preferably 0.02 or more, further preferably 0.03 or more, most preferably 0.04 or more, usually 0.3 or less, preferably 0. .2 or less, more preferably 0.15 or less, still more preferably 0.1 or less, and most preferably 0.075 or less.

If the value of a is within this range, the energy density per unit weight in the lithium transition metal-based compound is not significantly impaired, and good load characteristics can be obtained, which is preferable.
Furthermore, the value of δ is usually in the range of ± 0.5, preferably in the range of ± 0.4, more preferably in the range of ± 0.2, still more preferably in the range of ± 0.1, particularly preferably ± 0.05. Range.

If the value of δ is within this range, the stability as a crystal structure is high, and the cycle characteristics and high-temperature storage of a battery having an electrode produced using this lithium transition metal compound are favorable.
Here, the chemical meaning of the lithium composition in the lithium nickel manganese composite oxide, which is the composition of the lithium transition metal compound of the present invention, will be described in more detail below.

In order to obtain a and b in the composition formula of the lithium transition metal compound, each transition metal and lithium are analyzed with an inductively coupled plasma emission spectrometer (ICP-AES) to obtain a ratio of Li / Ni / Mn. It is calculated by the thing.
From a structural point of view, it is considered that lithium related to a is substituted for the same transition metal site. Here, due to the lithium according to a, the average valence of M and manganese becomes larger than 3.5 due to the principle of charge neutrality.

<Raw metal compound>
Although it does not specifically limit as a raw material metal compound used for the manufacturing method of this invention, For example, it selects from the group which consists of lithium raw material, nickel raw material, cobalt raw material, manganese raw material, iron raw material, vanadium raw material, chromium raw material, and titanium raw material At least one starting metal compound is used. Among these, at least one raw material metal compound selected from the group consisting of a lithium raw material, a nickel raw material, a cobalt raw material, and a manganese raw material is preferably used from the viewpoint of battery characteristics.

Preferred specific examples of these raw materials will be described later.
<Manufacturing method>
The production method of the present invention is not particularly limited. For example, in the method for producing a lithium transition metal composite oxide, the raw materials are mixed in a wet form to form a slurry, and the slurry is spray-dried to form a granular material. A method of crushing and classifying (this production method is sometimes referred to as “spray drying method” in the present application), among which lithium raw material, nickel raw material, cobalt raw material, manganese raw material, etc. are mixed in a wet form to form a slurry. A method of spray drying to form granules, firing, crushing, and classification (this production method may be referred to as “lithium pre-added spray drying method” in the present application), or nickel raw material, cobalt raw material, manganese raw material, etc. If necessary, a small amount of lithium raw material is mixed in a wet manner, and the slurry is spray-dried to form a granular material, and further lithium raw material so as to have a desired composition ratio. A method of dry-mixing, firing, crushing, and classifying (this production method is sometimes referred to as “lithium post-addition spray drying method” in this application), or a nickel raw material, a cobalt raw material, a manganese raw material, etc. The composite carbonate obtained by co-precipitation as a salt is calcined and decarboxylated, and the resulting granule and lithium raw material are dry mixed, and then calcined, crushed and classified (this, the production method in this application, "It may be called" coprecipitation method ").

<Particle size of lithium transition metal compound>
The particle size of the lithium transition metal compound obtained by the production method of the present invention is arbitrary as long as the effects of the present invention are not significantly impaired.
However, it is desirable that the lithium transition metal compound has a median diameter of 20 μm or less, preferably 15 μm or less when a particle size distribution is measured by a laser diffraction method on a sample that is not subjected to dispersion treatment with an ultrasonic oscillator. If the median diameter exceeds the upper limit, it is not possible to stably supply a slurry suitable for the desired particle size, or a large number of coarse particles are generated, so that a sharp particle size distribution can be obtained as a lithium transition metal compound. In some cases, the effects of the present invention cannot be obtained.

  On the other hand, the lower limit of the median diameter is usually 1 μm or more, preferably 3 μm or more. If the median diameter is less than the above lower limit, it is not possible to stably supply a slurry suitable for the desired particle size, or the fine powder increases and the particles of the lithium transition metal compound aggregate to form a lithium transition metal system. As a compound, a sharp particle size distribution may not be obtained, or the effects of the present invention may not be obtained.

As the median diameter of the lithium transition metal compound, a value measured by a known laser diffraction / scattering particle size distribution measuring device (manufactured by Horiba, Ltd .: LA-920 type) based on JIS Z 8825-1 should be adopted. Can do. Moreover, as a dispersion medium used in the measurement, 0
. A 1% by weight aqueous solution of sodium hexametaphosphate is used. Furthermore, the application time of ultrasonic waves (output 30 W, frequency 22.5 kHz) at the time of measurement is 0 minutes, and the refractive index used at the time of measurement is 1.60a010i (real part 1.60, imaginary part 0.10).

<Specific surface area of lithium transition metal compound>
The specific surface area of the lithium transition metal compound obtained by the production method of the present invention is arbitrary as long as the effects of the present invention are not significantly impaired.
However, the specific surface area of the lithium transition metal-based compound is usually 10 m ² / g or less, preferably 5 m ² / g or less. When the median diameter exceeds the upper limit, there may be a problem that the coating characteristics of the lithium transition metal compound obtained by the present invention are deteriorated or the battery performance is deteriorated.

On the other hand, the lower limit of the median diameter is usually 0.1 m ² / g or more, preferably 0.3 m ² / g or more. When the specific surface area is less than the lower limit, problems such as deterioration of battery performance as the lithium transition metal compound obtained by the present invention may occur.
The BET specific surface area can be measured by a known BET type powder specific surface area measuring device. In the present invention, a BET one-point method measurement by a continuous flow method was performed using Shimadzu Corporation: Flowsorb II 2300 type specific surface area measuring apparatus, using nitrogen as an adsorption gas and helium as a carrier gas. Specifically, the powder sample is heated and deaerated with a mixed gas at a temperature of 350 ° C., then cooled to liquid nitrogen temperature to adsorb the nitrogen / helium mixed gas, and then heated to room temperature with water. The adsorbed nitrogen gas was desorbed, the amount was detected by a heat conduction detector, and the specific surface area of the sample was calculated from this.

Next, taking a lithium nickel manganese cobalt composite oxide powder as an example of the lithium transition metal compound, the raw material and production method thereof will be described in more detail.
<Li raw material>
Among the raw material compounds used for the preparation of the slurry in producing the lithium nickel manganese cobalt based composite oxide by the method of the present invention, the lithium compounds include Li ₂ CO ₃ , LiNO ₃ , LiNO ₂ , LiOH, LiOH · H. ₂ O, LiH, LiF, LiCl, LiBr, LiI, CH ₃ OOLi, Li ₂ O, Li ₂ SO ₄ , dicarboxylic acid Li, citric acid Li, fatty acid Li, alkyllithium and the like can be mentioned.

Among these lithium compounds, lithium compounds that do not contain nitrogen atoms, sulfur atoms, or halogen atoms are preferable in that no harmful substances such as SO _x and NO _x are generated during the firing treatment. Further, a compound that easily forms voids by generating decomposition gas in the secondary particles of the spray-dried powder, for example, by generating decomposition gas during firing is preferable. Taking these points into consideration, Li ₂ CO ₃ , LiOH, and LiOH.H ₂ O are particularly preferable. These lithium compounds may be used individually by 1 type, and may use 2 or more types together.

<Ni raw material>
The nickel compounds include Ni (OH) ₂ , NiO, NiOOH, nickel carbonate, NiC ₂ O ₄ .2H ₂ O, Ni (NO ₃ ) ₂ .6H ₂ O, NiSO ₄ , NiSO ₄ .6H ₂ O,
Examples include nickel fatty acid and nickel halide.
Of these nickel compounds, _SO x during the firing process, in that it does not generate harmful substances such as NO _X, such as _{Ni (OH) 2, NiO,} NiOOH, nickel _{carbonate, NiC 2 O 4 · 2H 2} O Nickel compounds are preferred. Further, Ni (OH) ₂ , NiO, NiOOH, and nickel carbonate are more preferable from the viewpoint of being available as an industrial raw material at a low cost and from the viewpoint of high reactivity. In addition, Ni (OH) ₂ , NiO, and nickel carbonate are particularly preferable from the viewpoint of easily forming voids in the secondary particles of the spray-dried powder by generating decomposition gas during firing. These nickel compounds may be used individually by 1 type, and may use 2 or more types together.

<Mn raw material>
Further, as the manganese compound, manganese oxides such as Mn ₂ O ₃ , MnO ₂ , Mn ₃ O ₄ , M
Examples thereof include manganese salts such as nCO ₃ , Mn (NO ₃ ) ₂ , MnSO ₄ , manganese acetate, manganese dicarboxylate, manganese citrate and fatty acid manganese, halides such as oxyhydroxide and manganese chloride.

Among these manganese compounds, MnO ₂ , Mn ₂ O ₃ , Mn ₃ O ₄ , MnCO are used because they do not generate gases such as SO _x , NO _x, etc., and can be obtained at low cost as industrial raw materials. ₃ is preferred. These manganese compounds may be used individually by 1 type, and may use 2 or more types together.
<Co raw material>
Cobalt compounds include Co (OH) ₂ , CoOOH, CoO, Co ₂ O ₃ , C
o ₃ O ₄ , Co (OCOCH ₃ ) ₂ .4H ₂ O, CoCl ₂ , Co (NO ₃ ) ₂ .6H ₂ O, Co
(SO ₄ ) ₂ · 7H ₂ O, CoCO _{3 and the} like.

Among these cobalt compounds, _SO x during the firing process, in that it does not generate harmful substances such as _{NO X, Co (OH) 2} , CoOOH, CoO, is _{Co 2 O 3, Co 3 O} 4, CoCO 3 preferably Co (OH) ₂ , CoOO in terms of industrial availability at low cost and high reactivity
H is more preferable. In addition, Co (OH) ₂ , CoOOH, and CoCO ₃ are particularly preferable from the viewpoint of easily forming voids in the secondary particles of the spray-dried powder by generating decomposition gas during firing. These cobalt compounds may be used individually by 1 type, and may use 2 or more types together.

<Other element substitution and additives>
Further, in order to appropriately adjust the battery characteristics, other element substitution is performed in the structure of the lithium transition metal composite oxide in addition to the above Li, Ni, Mn, and Co raw material compounds to introduce a different element group, which will be described later. By adding the different element group by spray drying, it is possible to adjust the powder physical properties in the formed secondary particles. As used herein, the step of adding the foreign element added for the purpose of efficiently forming the voids of the secondary particles can be selected either before or after mixing the raw materials, depending on the nature. Is possible. In particular, it is preferable to add a compound that is easily decomposed due to mechanical shear stress applied by the mixing step after the mixing step.

As specific examples of the different element group introduced or substituted with other elements, there are two groups of elements, and specific compound names are described below.
As the first group, it is preferable to use a compound (further additive 1) having at least one element (further additive element 1) selected from B and Bi. Among these additional elements 1, it is preferable that the additional element 1 is B from the viewpoint that it can be obtained at low cost as an industrial raw material and is a light element.

  The type of compound containing additional element 1 (further additive 1) is not particularly limited as long as it exhibits the effects of the present invention, but usually boric acid, oxo acid salts, Oxides and hydroxides are used. Among these further additives 2, boric acid and oxides are preferable, and boric acid is particularly preferable because it can be obtained as an industrial raw material at low cost.

Further exemplary compounds of additive 1 include BO, B ₂ O ₂ , B ₂ O ₃ , B ₄ O ₅ , B ₆ O, B ₇ O, B ₁₃ O ₂ , LiBO ₂ , LiB ₅ O ₈ , Li ₂ B ₄ O ₇ , HBO ₂ , H ₃ BO ₃ , B (OH) ₃ , B (OH) ₄ , BiBO ₃ , Bi ₂ O ₃ , Bi ₂ O ₅ , Bi (OH
) Such as ₃ can be mentioned, from the viewpoint of relatively inexpensive and readily available as an industrial raw material, preferably include _{B 2 O 3, H 3 BO} 3, Bi 2 O 3, particularly _preferably, the H 3 BO ₃ Can be mentioned. These additional additives 1 may be used individually by 1 type, and 2 or more types may be mixed and used for them.

The second group includes compounds having at least one element selected from Mo, W, Nb, Ta and Re (hereinafter referred to as “further additive element 2”) (hereinafter “further additive 2”). It is preferable to use. Among these additional elements 2, the additional element 2 is preferably Mo or W, and most preferably W, because the effect is great. The type of the compound (further additive 2) containing the additional element 2 is not particularly limited as long as the effect of the present invention is exhibited, but an oxide is usually used.

Further exemplary compounds of additive 2 include MoO, MoO ₂ , MoO ₃ , MoO _x , Mo ₂ O ₃ , Mo ₂ O ₅ , Li ₂ MoO ₄ , WO, WO ₂ , WO ₃ , WO _x , W _2. O ₃ , W ₂ O ₅ , W ₁₈ O ₄₉ , W ₂₀ O ₅₈ , W ₂₄ O ₇₀ , W ₂₅ O ₇₃ , W ₄₀ O ₁₁₈ , Li ₂ WO ₄ , NbO, NbO ₂ , Nb ₂ O ₃ , Nb ₂ O ₅ , Nb ₂ O ₅ .nH ₂ O, LiNbO ₃ , Ta ₂ O, Ta ₂ O ₅ , LiTaO ₃ , ReO ₂ , ReO ₃ , Re ₂ O ₃ , Re ₂ O _{7 and the} like are listed as industrial raw materials. MoO ₃ , Li ₂ MoO ₄ , WO ₃ , Li ₂ WO ₄ are preferable, and WO ₃ is particularly preferable because it is relatively easily available or includes lithium. These additional additives 2 may be used individually by 1 type, and 2 or more types may be mixed and used for them.

<Wet grinding>
In the raw material mixing stage, it is preferable that the raw material is pulverized in parallel. As the degree of pulverization, the particle diameter of the raw material particles after pulverization is an index, but the average particle diameter (median diameter) is usually 1.0 μm or less, preferably 0.7 μm or less, and most preferably 0.5 μm or less. . If the average particle size of the pulverized raw material particles is too large, the reactivity in the firing process is lowered, and the composition is difficult to homogenize. However, making particles smaller than necessary leads to an increase in the cost of pulverization, so that the average particle size is usually 0.01 μm or more, preferably 0.02 μm or more, more preferably 0.05 μm or more. It ’s fine. A means for realizing such a degree of pulverization is not particularly limited, but a wet pulverization method is preferable. Specific examples include a dyno mill and a star mill.

  The median diameter of the pulverized particles in the slurry should be a value measured by a known laser diffraction / scattering particle size distribution measuring device (manufactured by Horiba, Ltd .: LA-920 type) based on JIS Z 8825-1. Can do. Moreover, as a dispersion medium used in the measurement, a 0.1% by weight sodium hexametaphosphate aqueous solution is used. Furthermore, the application time of ultrasonic waves (output 30 W, frequency 22.5 kHz) during measurement is 5 minutes, and the refractive index used during measurement is 1.24a000i (real part 1.24, imaginary part 0.00).

<Spray drying>
After the wet mixing, it is then usually subjected to a drying process. The method is not particularly limited, but spray drying is preferable from the viewpoints of uniformity of the generated particulate matter, powder flowability, powder handling performance, and efficient production of dry particles.
The concentration of the slurry to be subjected to spray drying is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired, but usually 1% by weight or more, preferably 5% by weight or more, more preferably 10% by weight or more, particularly Preferably it is 15 weight% or more. This is because if the slurry concentration is too low, productivity is significantly impaired. Further, the upper limit of the slurry concentration is preferably higher as productivity is improved, but if the slurry concentration is too high, the viscosity of the slurry becomes high, and there is a possibility that the nozzle cannot be sprayed in the spraying step described later. Therefore, it is usually 70% by weight or less.

  Further, the viscosity of the slurry is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. Usually, the viscosity is 100 mPa · s or more, preferably 200 mPa · s or more, and usually 5000 mPa · s or less, preferably 3000 mPa. -S or less. If the viscosity of the slurry is too low, it becomes difficult to form clean spherical particles when sprayed in the spraying process described later, and if it is too high, there is a possibility that the nozzle cannot be sprayed.

Spray drying may be performed by a known method. For example, it is possible to use a method in which a gas flow and slurry are caused to flow into the tip of the nozzle so that the slurry is ejected as droplets from the nozzle and brought into contact with a drying gas to quickly dry the droplets.
When producing granulated particles by spray drying, the particle size of the obtained granulated particles can be controlled by appropriately selecting the spray format, pressurized gas flow supply rate, slurry supply rate, drying temperature, etc. it can.

Moreover, there is no restriction | limiting in the conditions at the time of spray-drying, as long as the effect of this invention is not impaired remarkably. For example, the dry atmosphere is usually air, but may be an inert atmosphere such as nitrogen. Moreover, although the temperature of the drying gas is also arbitrary, it is usually preferable to introduce into the spraying device at 80 to 300 ° C and to discharge from the device at 45 to 250 ° C.
The median diameter of the powder obtained by spray drying is usually 30 μm or less, more preferably 25 μm or less, still more preferably 20 μm or less, and most preferably 18 μm or less. However, since it tends to be difficult to obtain a too small particle size, it is usually 3 μm or more, preferably 4 μm or more, more preferably 5 μm or more.

<Baking precursor>
Here, the “firing precursor” in the present invention means a precursor of a lithium transition metal compound such as a lithium nickel manganese cobalt composite oxide before firing obtained by treating a spray-dried powder. For example, the above spray-dried powder may contain a compound that generates or sublimates decomposition gas during the above-described firing to form voids in the secondary particles, and serves as a firing precursor.

<Baking>
This firing condition depends on the composition and the lithium compound raw material used, but as a tendency, if the firing temperature is too high, primary particles grow excessively, sintering between the particles proceeds too much, and the specific surface area becomes small. Pass. On the other hand, if it is too low, heterogeneous phases are mixed, and the lattice distortion increases without developing the crystal structure. Moreover, the specific surface area becomes too large. The firing temperature is usually 900 ° C. or higher, preferably 950 ° C. or higher, most preferably 1000 ° C. or higher, and is usually 1300 ° C. or lower, preferably 1250 ° C. or lower, most preferably 1200 ° C. or lower.

  When firing is performed in two stages, the first stage holding temperature is preferably 500 ° C. or higher, more preferably 550 ° C. or higher, most preferably 600 ° C. or higher, usually 1000 ° C. or lower, more preferably 950 ° C. or lower, most preferably. Is 900 ° C. or lower. For firing, for example, a box furnace, a tubular furnace, a tunnel furnace, a rotary kiln or the like can be used. The firing process is usually divided into three parts: temperature increase, maximum temperature retention, and temperature decrease. The second maximum temperature holding portion is not necessarily limited to one time, and may include two or more stages depending on the purpose, which means that aggregation is eliminated to the extent that secondary particles are not destroyed. The temperature raising, maximum temperature holding, and temperature lowering steps may be repeated twice or more with a crushing step or a pulverization step which means crushing to primary particles or even fine powder.

Although the time required for firing varies depending on the temperature, it is preferable from the viewpoint of productivity as it is short, but if it is too short, the crystallinity of the lithium transition metal compound is not improved, and usually 30 minutes or more,
Preferably it is 3 hours or more, most preferably 6 hours or more, 24 hours or less, preferably 20 hours or less, most preferably 16 hours or less. If the holding time is too short, it is difficult to obtain a lithium nickel manganese cobalt based composite oxide powder with good crystallinity, and it is not practical to have a too long holding time. If the firing time is too long, productivity is remarkably impaired.

  When firing is performed in two stages, the time required for the first stage firing varies depending on the temperature, but the shorter is preferable from the viewpoint of productivity, but if it is too short, the purpose of the first stage (preliminary firing) cannot be achieved. Therefore, it is usually 30 minutes or longer, preferably 3 hours or longer, most preferably 6 hours or longer, 24 hours or shorter, preferably 20 hours or shorter, most preferably 16 hours or shorter. If the firing time is too long, productivity is remarkably impaired.

In addition to the above-described manufacturing method using a baking furnace, baking using a moving bed or the like is also possible.
As an atmosphere during firing, an oxygen-containing gas atmosphere such as air can be used. Usually, the atmosphere has an oxygen concentration of 1% by volume or more, preferably 10% by volume or more, more preferably 15% by volume or more, and 100% by volume or less, preferably 50% by volume or less, more preferably 25% by volume or less.

By performing this firing step, a lithium transition metal composite compound can be obtained.
<Disintegration / classification process>
The lithium transition metal composite compound obtained in the firing step is then subjected to a crushing / classifying step.
The crushing step is a step of breaking the lithium transition metal composite compound sintered after firing to an appropriate size. The size after crushing is usually 3 cm or less, preferably 1 cm or less, more preferably 5 mm. Hereinafter, it is more preferably 1 mm or less, usually 1 μm or more, preferably 10 μm or more, more preferably 50 μm or more, and further preferably 100 μm or more. If the size after crushing is too large, the classification efficiency in the classification step, which is the next step, may be reduced. On the other hand, if the size after pulverization is too small, the spherical shape formed in the spray drying process may collapse, or fine powders may aggregate to reduce the classification efficiency in the subsequent classification process. A roll crusher device is used for crushing. The operating conditions of each device are determined according to the desired size after crushing. The crushing step may not be performed or may be performed a plurality of times depending on the degree of sintering of the lithium transition metal composite compound.

<Crushing process by roll crusher>
The crushing step of the present invention has a crushing step of crushing the fired lithium transition metal composite oxide using a roll crusher having two or more rolls,
The first step roll interval is 0.8-4 mm,
The second stage roll interval is 0.3 to 1 mm.

  The number of rolls of the roll crusher is characterized in that the lower limit is two or more stages from the viewpoint of improving crushing efficiency. The number of rolls of the roll crusher may be increased from the viewpoint of crushing efficiency. However, since the effect of improving the crushing efficiency is low even if the number of rolls is increased beyond the upper limit, the upper limit is usually 5 or less, preferably 4 or less, particularly preferably 3 or less.

The lower limit of the roll interval of the first stage is characterized in that it is 0.8 mm or more in order to prevent crushing efficiency and retention of the transition metal compound. Further, it is preferably 0.85 mm or more, more preferably 0.9 mm or more, and particularly preferably 0.95 mm or more. The upper limit is characterized in that it is 4 mm or less because the crushing efficiency in the second stage is reduced, and coarse particles increase and the yield decreases. Also preferably 3.8 mm
Hereinafter, it is more preferably 3.5 mm or less, particularly preferably 3 mm or less.

  The lower limit of the roll interval of the second stage is characterized by being 0.3 mm or more in order to prevent crushing efficiency and retention of the transition metal compound. Moreover, Preferably it is 0.4 mm or more, Most preferably, it is 0.5 mm or more. As an upper limit, since coarse particles increase and a yield falls, it is characterized by being 1 mm or less normally. Further, it is preferably 0.9 mm or less, more preferably 0.8 mm or less, and particularly preferably 0.7 mm or less.

Examples of the material of the roll usually include metals and ceramics. Among these, ceramic is particularly preferable from the viewpoint of preventing foreign matter contamination.
In this invention, in order to further improve crushing efficiency, it is preferable to make a groove | channel in the axial direction of a roll. The groove is preferably placed in the first-stage roll from the viewpoint of improving the crushing efficiency. The groove is preferably inserted at equal intervals with respect to the rotation axis. The lower limit of the number of grooves is usually 1 or more, preferably 2 or more, from the viewpoint of facilitating biting of the calcined mass. The upper limit is usually 8 or less, preferably 6 or less from the point that the amount passing through the groove without being sufficiently crushed increases and the crushed material becomes rough and may reduce the yield. is there.

  The lower limit of the width of the groove is usually 1 cm or more, preferably 1.1 cm or more, and more preferably 1.2 cm or more, because the calcined mass stays in the roll and lowers the crushing efficiency. . The upper limit is usually 5 cm or less, preferably 4 cm or less, and more preferably 3 cm or less, because crushing becomes rough and the yield may be reduced. The lower limit of the depth of the groove is usually 2 mm or more, preferably 2.5 mm or more, and more preferably 3 mm or more, from the viewpoint of sufficiently expressing the effect of facilitating the biting of the calcined mass. The upper limit is usually 2 cm or less, preferably 1.5 cm or less, and more preferably 1 cm or less, because crushing becomes coarse and the yield may be reduced.

  The lithium transition metal composite compound that has been moderately sized in the crushing step is then adjusted to the final desired particle size in the classification step. The median diameter after classification is usually 20 μm or less, preferably 15 μm or less, and usually 1 μm or more, preferably 3 μm or more. When the median diameter exceeds the upper limit, a large amount of coarse particles exceeding the electrode film thickness are generated when the battery electrode is formed, which may adversely affect the battery yield. When the median diameter is less than the above lower limit, the fine powder increases and the particles of the transition metal compound agglomerate so that a sharp particle size distribution cannot be obtained as the transition metal compound or the effect of the present invention cannot be obtained. There is a case. For classification, devices such as a circular vibration sieve, a classifier that presses powder against a mesh screen with a blade rotating at high speed, and an airflow classifier are used. The operating conditions of each device are determined according to the desired size after crushing. In addition, you may implement a classification process in multiple times as needed. In the classification, crushing may be performed at the same time.

[Other processes]
In the production method of the present invention, unless the effects of the present invention are significantly impaired, processes other than the classification process and the baking process described above may be performed.
For example, you may make it perform the grinding | pulverization process etc. which grind | pulverize the lithium transition metal complex oxide obtained by baking.

Further, for example, a part of the raw material may be added to or removed from the firing precursor in order to adjust the ratio of the contained elements.
Further, for example, in order to keep the median diameter and maximum particle diameter of the firing precursor within the above-described range, pulverization or the like may be performed as appropriate.
<Reason why the production method of the present invention brings about the above effects>
The reason why the production method of the present invention brings about the above-mentioned effects is not yet clear, but is presumed as follows.

  That is, in the production process of the transition metal compound, the production method of the present invention can efficiently perform crushing by performing crushing in a plurality of stages, and also controls the roll interval. It is presumed that the transition metal compound did not stay and the crushing efficiency was further improved to improve the productivity.

EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further more concretely, this invention is not limited to these Examples, unless the summary is exceeded.
<Example 1>
Li ₂ CO ₃ , nickel carbonate, Mn ₃ O ₄ , CoOOH, H ₃ BO ₃ , WO ₃ with Li: Ni: Mn: Co: B: W = 1.15: 0.45: 0.45: 0.10 : Weighed and mixed so that the molar ratio was 0.0025: 0.015, and added water to prepare a slurry having a solid content of 40% by weight. The solid content in the slurry was wet pulverized to a median diameter of 0.5 μm using a circulating medium agitation type wet bead mill. The obtained slurry was spray-dried with a spray dryer to obtain substantially spherical granulated particles having a median diameter of about 17 μm. The granulated particles are charged into a ceramic baking pot, and the first stage baking is performed at a maximum temperature of 800 ° C. for about 10 hours while circulating air, and then the second stage baking is performed at a maximum temperature of 1150 ° C. for about 12 hours. went. As a result, a fired lump having an almost charged molar ratio composition was obtained.

The fired lump was crushed by setting the interval between the first rolls of the roll crusher having two ceramic rolls to 1 mm and the interval between the second rolls to 0.5 mm.
As a result, the coarse particle ratio of 1 mm or more in the powder after pulverization was 0.7%, which led to a significant yield improvement.
<Example 2>
A lithium transition metal composite oxide was produced in the same manner as in Example 1 except that the interval between the first rolls was 3 mm. As a result, the coarse particle ratio of 1 mm or more in the powder after pulverization was 2.3%, which led to a significant yield improvement.

<Example 3>
A lithium transition metal composite oxide was produced in the same manner as in Example 1 except that the first roll was provided with grooves. The grooves had a width of 2 cm and a depth of 5 mm, and four grooves were produced on one roll. As a result, the pulverization time could be shortened compared to Examples 1 and 2 without causing the baked mass to stay on the roll, and the pulverization could be efficiently performed.

<Comparative Example 1>
A lithium transition metal composite oxide was produced in the same manner as in Example 1 except that the interval between the first rolls was 5 mm. As a result, the coarse particle ratio of 1 mm or more in the powder after pulverization was 6.3%.
In Examples 1 and 2 according to the present invention, by adjusting the gap between the rolls, the coarse particle ratio after pulverization could be reduced as compared with Comparative Example 1, and the yield could be improved. Further, in Example 3, the effect of facilitating the biting of the calcined mass can be expressed by forming a groove in the roll, and the problem that the calcined mass stays on the roll is improved. It could be crushed more efficiently than Example 2.

The field of application of the present invention is not particularly limited, and can be used for various known uses, and is particularly useful for the method of producing a transition metal composite oxide for a lithium secondary battery. Input PC, mobile PC, electronic book player, mobile phone, mobile fax, mobile copy, mobile printer, headphone stereo, video movie, LCD TV, handy cleaner, portable CD, mini-disc, transceiver, electronic notebook, calculator, memory card, It is useful in a method for producing a transition metal composite oxide for a lithium secondary battery suitably used for a portable tape recorder, a radio, a backup power source, a motor, a lighting device, a toy, a game machine, a watch, a strobe, a camera and the like.

Claims (4)

In the method for producing a lithium transition metal composite oxide for a lithium secondary battery,
Having a crushing step of crushing the lithium transition metal composite oxide after firing using a roll crusher having two or more rolls;
The first step roll interval is 0.8-4 mm,
A method for producing a lithium transition metal composite oxide for a lithium secondary battery, wherein a second-stage roll interval is 0.3 to 1 mm.   The manufacturing method according to claim 1, wherein the roll is provided with a groove.   The manufacturing method according to claim 1, further comprising a classification step using a pneumatic classifier after the pulverization step.   4. The manufacturing method according to claim 1, wherein the material of the roll is ceramic.