JP2006253119A - Lithium-nickel-manganese-cobalt-based composite oxide powder for lithium secondary battery positive electrode material, its manufacturing method, positive electrode for lithium secondary battery using it, and lithium secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide lithium-nickel-manganese-cobalt-based composite oxide powder for a lithium secondary battery positive electrode material capable of achieving a balance among cost reduction, enhancement of high-voltage resistance, increase of safety and battery performance improvement, in use for a lithium secondary battery positive electrode material. <P>SOLUTION: This lithium-nickel-manganese-cobalt-based composite oxide powder for a lithium secondary battery positive electrode material is formed by including a crystalline structure belonging to a layered structure and has a composition represented by the following formula (I): Li[Li<SB>z/(2+z)</SB>ä(Li<SB>x</SB>Ni<SB>(1-3x)/2</SB>Mn<SB>(1+x)/2</SB>)<SB>(1-y)</SB>Co<SB>y</SB>}<SB>2/(2+z)</SB>]O<SB>2</SB>, where 0.01≤x≤0.15, 0≤y≤0.35 and 0.02(1-y)(1-3x)≤z≤0.15(1-y)(1-3x). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a lithium nickel manganese cobalt composite oxide powder used as a lithium secondary battery positive electrode material and a method for producing the same, and a positive electrode for a lithium secondary battery using the lithium nickel manganese cobalt composite oxide powder, The present invention also relates to a lithium secondary battery including the positive electrode for the lithium secondary battery.

  Lithium secondary batteries are excellent in energy density and output density, and are effective in reducing the size and weight. Therefore, the demand for power supplies for portable devices such as notebook computers, mobile phones, and handy video cameras is growing rapidly. ing. Lithium secondary batteries are also attracting attention as power sources for electric vehicles and power load leveling.

  Currently, lithium manganese composite oxides, layered lithium nickel composite oxides, and layered lithium cobalt composite oxides having a spinel structure are used as positive electrode active material materials for lithium secondary batteries. All of the lithium secondary batteries using these lithium-containing composite oxides have advantages and disadvantages in terms of characteristics. That is, a lithium manganese composite oxide having a spinel structure is inexpensive and relatively easy to synthesize, and is excellent in safety when used as a battery, but has a low capacity and inferior high-temperature characteristics (cycle and storage). Layered lithium-nickel composite oxides have high capacity and excellent high-temperature characteristics, but are difficult to synthesize, have poor stability when used as batteries, and have drawbacks such as requiring careful storage. Layered lithium cobalt-based composite oxides are widely used as power sources for portable devices because they are easy to synthesize and have an excellent balance of battery performance. However, they are not sufficient in safety and costly. It is a drawback.

  Under these circumstances, lithium nickel manganese cobalt-based composite oxides having a layered structure have been overcome as disadvantages of these positive electrode active material materials as possible candidates for active material materials that can overcome or be reduced as much as possible and are excellent in battery performance balance. It has been proposed, and is expected to be a promising positive electrode active material that can meet any of the demands in recent years, with increasing demands for cost reduction, higher voltage, and safety.

  However, in conventional layered lithium nickel manganese cobalt-based composite oxides, the cost reduction, voltage increase, and safety change depending on the composition ratio, so further cost reduction and higher upper limit voltage are set. For higher safety requirements, select a material with a limited composition range such as increasing the manganese / nickel atomic ratio above 1 or reducing the cobalt ratio. There is a need. However, a lithium secondary battery using a lithium nickel manganese cobalt based composite oxide having such a composition range as a positive electrode material is deteriorated in battery performance such as rate and output characteristics. It was necessary.

  Conventionally, examples in which lithium nickel manganese cobalt based composite oxide having a composition range in which the manganese / nickel atomic ratio exceeds 1 are actually used are disclosed in Patent Documents 1 and 2 and Non-Patent Documents 1-8.

  However, in Patent Document 1 and Non-Patent Documents 1 to 8, the Li excess amount z described later defined in the present invention is limited to 0, and the necessary conditions for improving battery performance in the present invention are not satisfied. However, these techniques alone cannot improve the battery performance which is the object of the present invention. Moreover, in the Example of patent document 2, the manganese / nickel atomic ratio is larger than the upper limit prescribed | regulated by this invention, and it does not satisfy | fill the necessary condition for aiming at the improvement of battery performance. However, the intended battery performance cannot be improved.

  On the other hand, Patent Document 3 discloses that the battery performance is improved in the lithium nickel manganese cobalt-based composite oxide composition region, which is considered to have relatively high safety. In Patent Document 3, selection of the lithium / transition metal (nickel, manganese, cobalt) ratio can be considered as one of the reasons for improving the battery performance. In this case, by making the lithium / transition metal (nickel, manganese, cobalt) ratio slightly larger than 1, battery performance such as rate characteristics and output characteristics can be improved without lowering the charge / discharge capacity. Become.

However, in the example of Patent Document 3, only a composition material having a manganese / nickel atomic ratio of 1 is used, and in such a composition, when the charge voltage is set higher, the charge / discharge cycle characteristics are inferior. Have. That is, Patent Document 3 does not have a technical idea of taking measures to maintain cycle characteristics even when the manganese / nickel atomic ratio is set to be larger than 1 and the charging voltage is set higher. Nor. Containing carbon that affects battery performance by causing side reactions as impurity constituents, or existing on the surface and grain boundaries of the positive electrode active material, thereby inhibiting lithium ion storage and release reactions. There is no description about concentration C, and there is no recognition of the effect of volume resistivity on battery performance.
JP2004-6267 US6,680,143B2 Japanese Patent No. 3571671 Electrochem. Solid-State Lett. , 4 (2001) A194 J. et al. Power sources, 119-121 (2003) 166 J. et al. Power sources, 129 (2004) 288 Electrochem. Solid-State Lett. , 7 (2004) A167 J. et al. Power sources, 119-121 (2003) 161 Solid State Ionics, 164 (2003) 43 J. et al. Electrochem. Soc. 149 (2002) A815 Electrochem. Com. 6 (2004) 1085

  The present invention relates to a lithium nickel manganese cobalt composite for lithium secondary battery positive electrode material that can achieve both low cost, high voltage resistance, high safety and battery performance improvement in use as a lithium secondary battery positive electrode material. An object of the present invention is to provide an oxide powder, a manufacturing method thereof, a positive electrode for a lithium secondary battery using the lithium nickel manganese composite oxide powder, and a lithium secondary battery including the positive electrode for the lithium secondary battery. And

The lithium nickel manganese cobalt based composite oxide powder for a positive electrode material of a lithium secondary battery of the present invention comprises a crystal structure belonging to a layered structure, and the composition is represented by the following formula (I): (Claim 1).
Li [Li _{z / (2 + z)} {(Li _x Ni _{(1-3x) / 2} Mn _{(1 + x) / 2} ) _(1-y) Co _y } _{2 / (2 + z)} ] O ₂ ... (I)
(However, 0.01 ≦ x ≦ 0.15
0 ≦ y ≦ 0.35
0.02 (1-y) (1-3x) ≦ z ≦ 0.15 (1-y) (1-3x))

  That is, as a result of intensive studies, the present inventors have determined that the atomic ratio of lithium, nickel, manganese, and cobalt is within the above range in a lithium nickel manganese cobalt based composite oxide that includes a crystal structure belonging to a layered structure. Lithium nickel manganese cobalt-based composite oxide that can achieve both low cost, high voltage resistance, high safety, and improved battery performance such as rate and output characteristics as lithium secondary battery positive electrode material by limiting The inventors have found that a powder can be obtained and have completed the present invention.

（以下「層状Ｒ（−３）ｍ構造」と表記する。）に帰属される。
ただし、層状ＬｉＭｅＯ_２とは、層状Ｒ（−３）ｍ構造に限るものではない。これ以外にもいわゆる層状Ｍｎと呼ばれるＬｉＭｎＯ_２は斜方晶系で空間群Ｐｍ２ｍの層状化合物であり、またいわゆる２１３相と呼ばれるＬｉ_２ＭｎＯ_３は、Ｌｉ［Ｌｉ_1/3Ｍｎ_2/3］Ｏ_２とも表記でき、単斜晶系の空間群Ｃ２／ｍ構造であるが、やはりＬｉ層と［Ｌｉ_1/3Ｍｎ_2/3］層および酸素層が積層した層状化合物である。 The lithium nickel manganese cobalt-based composite oxide having a structure that can be attributed to the layered structure is generally expressed as LiMeO ₂ (Me is a transition metal), and the lithium layer, the transition metal layer, and the oxygen layer are uniaxially oriented. It has a structure equivalent to the laminated lithium transition metal oxide. As typical LiMeO ₂ , 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 layered compound of the space group Pm2m, and Li ₂ MnO ₃ called so-called 213 phase is Li [Li _1/3 Mn _2/3 ] O. _{2 is} a monoclinic space group C2 / m structure, which is also a layered compound in which a Li layer, a [Li _1/3 Mn _2/3 ] layer and an oxygen layer are laminated.

  In the composition of the present invention, the z value is 0.02 (1-y) (1-3x) ≦ z ≦ 0.15 (1-y) (1-3x), and the Li amount is the stoichiometric composition. Although it is important to be in a slightly richer range, the reason why the battery performance (particularly rate characteristics and output characteristics) is improved by this is considered as follows.

Assuming that the layered structure is, for example, a layered R (−3) m structure, Ni valence change (Ni (II) → Ni (III)) accompanying the transition metal site (3b) substitution of excess Li occurs, and Ni As a result of an increase in the ratio of (III) / Ni (II) (increase in Ni average valence), the electronic state of the crystal is changed and powder conductivity is improved (resistivity is decreased). It is estimated that the substitution amount (occupancy) of the Li site (3a) in II) is reduced, the disorder of the crystal structure is suppressed, and the diffusion of Li ions becomes smooth.
In addition, as a result of performing XANES (X-ray absorption near edge structure) spectrum measurement on the sample in which surplus lithium was systematically changed, the present inventors did not observe valence changes of Mn and Co (Mn (IV) It is confirmed that only Ni causes a valence change (Ni (II) → Ni (III)).

  In addition, when the x value is 0.01 ≦ x ≦ 0.15 and the Mn / Ni atomic ratio is in a range larger than 1, when used as a lithium secondary battery designed to be charged at a high charging potential, , Cycle characteristics and safety are improved. This is because the Mn / Ni atomic ratio has increased, the crystal structure has become more stable, and since the Ni content ratio has decreased, the Li site substitution amount (occupancy) of Ni (II) has decreased relatively. This is probably because the disorder of the crystal structure was suppressed.

  The chemical meaning of z and x in the above formula (I) will be described in more detail below.

The lithium nickel manganese cobalt based composite oxide of the present invention includes a crystal structure belonging to a layered structure.
As described above, the layered structure is not necessarily limited to the R (-3) m structure, but is preferably one that can be attributed to the R (-3) m structure from the viewpoint of electrochemical performance. In order to explain in detail, the layered structure is assumed to be an R (-3) m structure below.
In the present invention, the ratio of Li [Ni _1/2 Mn _1/2 ] O ₂ having a layered structure is (1-3x) (1-y),
The ratio of Li [Li _1/3 Mn _2/3 ] O ₂ is 3x (1-y),
The ratio of LiCoO ₂ is y
Layered lithium transition metal composite oxide,
[Li] ^(3a) [(Li _x Ni _{(1-3x) / 2} Mn _{(1 + x) / 2} ) _(1-y) Co _y ] ^(3b) O ₂ (II)
In the basic structure.
Here, (3a) and (3b) represent different metal sites in the layered R (-3) m structure, respectively.

However, the important point of the present invention is that Li is added in excess of z mol with respect to the composition of the formula (II), and is dissolved.
[Li] ^(3a) [Li _{z / (2 + z)} {(Li _x Ni _{(1-3x) / 2} Mn _{(1 + x) / 2} ) _(1-y) Co _y } _{2 / (2 + z ^{)] (3b) O 2 ...}} (I)
(However, 0.01 ≦ x ≦ 0.15, 0 ≦ y ≦ 0.35, 0.02 (1-y) (1-3x) ≦ z ≦ 0.15 (1-y) (1-3x) (3a) and (3b) represent different metal sites in the layered R (-3) m structure.)
It is represented by.

In addition, this notation indicates that, in a layered lithium transition metal composite oxide expressed as LiMeO ₂ (Me is a transition metal), when an excess Li of z mol is dissolved in a transition metal site (3b site), [Li] ^(3a) [Li _{z / (2 + z)} Me _{2 / (2 + z)} ] ^(3b) O ₂
It is expressed in the same way as that.

In order to obtain x, y, and z in the formula (I), each transition metal and Li are analyzed by an inductively coupled plasma emission spectrometer (ICP-AES) to obtain a ratio of Li / Ni / Mn / Co. It is calculated by the thing. That is, x and y are determined by the Ni / Mn and Co / Ni ratios, and z is the Li / Ni molar ratio Li / Ni = {2 + 2z + 2x (1-y)} / {(1-3x) (1-y) }
It can be obtained from

  From a structural point of view, it is considered that both Li related to z and Li related to x are substituted by the same transition metal site. Here, the difference between Li related to x and Li related to z is whether or not the valence of Ni is greater than two (whether or not trivalent Ni is generated). That is, since x is a value linked with the Mn / Ni ratio (Mn rich degree), the Ni valence does not vary only by this x value, and Ni remains divalent. On the other hand, z can be regarded as Li that increases the Ni valence, and z is an index of the Ni valence (the ratio of Ni (III)).

  When the Ni valence (m) accompanying the change of z is calculated from the formula (I), it is assumed that the Co valence is trivalent and the Mn valence is tetravalent, and m = 2z / {(1 -Y) (1-3x)} + 2. This calculation result means that the Ni valence is not determined only by z but is a function of x and y. If z = 0, the Ni valence remains divalent regardless of the values of x and y. In short, even when the z value is the same, it means that the Ni valence increases as the composition of Mn rich (x value is large) and / or Co rich (y value is large). The rate characteristics and output characteristics are improved, but on the other hand, the capacity tends to decrease. From this, it can be said that the upper limit of the z value is more preferably defined as a function of x and y as described above.

  In addition, when the y value is in the range of 0 ≦ y ≦ 0.35 and the amount of Co is small, in addition to reducing the cost, it was used as a lithium secondary battery designed to be charged at a high charging potential. In some cases, cycle characteristics and safety are improved.

  In the above formula (I), x, y, z values are 0.05 ≦ x ≦ 0.12, 0.10 ≦ y ≦ 0.20, and 0.04 (1-y) (1−3x) ≦, respectively. It is preferable that z ≦ 0.13 (1-y) (1-3x) (claim 2).

  The lithium nickel manganese cobalt based composite oxide of the present invention preferably has no diffraction peak at 2θ = 31 ± 1 ° in a powder X-ray diffraction pattern using CuKα rays.

  Further, the lithium nickel manganese cobalt based composite oxide of the present invention includes a structure whose crystal structure belongs to a layered R (-3) m structure, and has a lattice constant of 2.855Å ≦ a ≦ 2.870８, It is preferable to be in the range of 14.235 Å ≦ c ≦ 14.265 請求 (Claim 4).

The lithium nickel manganese cobalt composite oxide powder for a lithium secondary battery positive electrode material of the present invention preferably has a carbon content C of 0.030 wt% or less (Claim 5), and has a volume resistivity ( (When compacted to 40 MPa) is 5 × 10 ⁵ Ω · cm or less (Claim 6), the bulk density is 1.5 g / cc or more, the average primary particle diameter is 0.1 to 3 μm, and the median diameter of the secondary particles is 3. It is preferably in the range of ˜20 μm (Claim 7). The BET specific surface area is preferably 0.2 to 3.0 m ² / g (Claim 8).

  The method for producing a lithium nickel manganese cobalt composite oxide powder for a lithium secondary battery positive electrode material of the present invention is obtained by using such a layered lithium nickel manganese cobalt composite oxide powder for a lithium secondary battery positive electrode material of the present invention. A method for producing a nickel compound, a manganese compound, and a cobalt compound, and a slurry in which these are uniformly dispersed is spray-dried and / or pyrolyzed to aggregate primary particles to form secondary particles. After the powder is formed, the powder is mixed with a lithium compound, and the obtained mixture is fired in an oxygen-containing gas atmosphere (claim 9).

  The positive electrode for a lithium secondary battery of the present invention has a positive electrode active material layer containing such a lithium nickel manganese cobalt-based composite oxide powder for a lithium secondary battery positive electrode material of the present invention and a binder as a current collector. (Claim 10).

  The lithium secondary battery of the present invention is a lithium secondary battery comprising a negative electrode capable of inserting and extracting lithium, a non-aqueous electrolyte containing a lithium salt, and a positive electrode capable of inserting and extracting lithium. Such a positive electrode for a lithium secondary battery according to the present invention is used (claim 11).

The lithium secondary battery of the present invention is preferably designed such that the charging potential of the positive electrode in a fully charged state is 4.4 V (vs. Li ^/ Li ⁺ ) or higher (claim 12).

  When the lithium nickel manganese cobalt based composite oxide powder for lithium secondary battery positive electrode material of the present invention is used as a lithium secondary battery positive electrode material, the cost reduction, high voltage resistance, high safety and battery performance improvement are achieved. Can be achieved. Therefore, according to the present invention, there is provided an excellent lithium secondary battery that is inexpensive and highly safe and can maintain high performance even when used at a high charging voltage.

  DESCRIPTION OF EMBODIMENTS 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 not limited to the gist thereof. The content of is not specified.

[Lithium nickel manganese cobalt based composite oxide]
<composition>
The lithium nickel manganese cobalt-based composite oxide for a lithium secondary battery positive electrode material of the present invention includes a crystal structure belonging to a layered structure, and the composition is represented by the following formula (I).
Li [Li _{z / (2 + z)} {(Li _x Ni _{(1-3x) / 2} Mn _{(1 + x) / 2} ) _(1-y) Co _y } _{2 / (2 + z)} ] O ₂ ... (I)
(However, 0.01 ≦ x ≦ 0.15
0 ≦ y ≦ 0.35
0.02 (1-y) (1-3x) ≦ z ≦ 0.15 (1-y) (1-3x))

  In the formula (I), the value of z is 0.02 (1-y) (1-3x) or more, preferably 0.03 (1-y) (1-3x) or more, more preferably 0.04 ( 1-y) (1-3x) or more, more preferably 0.05 (1-y) (1-3x) or more, most preferably 0.06 (1-y) (1-3x) or more, 0 .15 (1-y) (1-3x) or less, preferably 0.14 (1-y) (1-3x) or less, more preferably 0.13 (1-y) (1-3x) or less, Preferably it is 0.12 (1-y) (1-3x) or less. If the lower limit is not reached, the conductivity may decrease, and if the upper limit is exceeded, the amount of substitution to the transition metal site becomes too large and the battery capacity becomes low. There is a fear.

  On the other hand, if z is too large, the carbon dioxide absorbability of the active material powder increases, so that it becomes easy to absorb carbon dioxide in the atmosphere. As a result, it is estimated that the concentration of contained carbon increases.

  On the other hand, if z is too small, the amount of Li for forming a phase mainly composed of a layered structure is clearly insufficient, and it is estimated that a spinel phase appears as a different phase.

  The value of x is 0.01 or more, preferably 0.03 or more, more preferably 0.04 or more, most preferably 0.05 or more, 0.15 or less, preferably 0.14 or less, more preferably 0.13. Hereinafter, it is most preferably 0.12 or less. Below this lower limit, the storage stability tends to deteriorate and easily deteriorate, the stability at high voltage decreases, and the safety tends to decrease. When the upper limit is exceeded, a heterogeneous phase is likely to be generated, or the battery performance is likely to be lowered.

  The value of y is 0 or more, preferably 0.05 or more, more preferably 0.10 or more, most preferably 0.15 or more, 0.35 or less, preferably 0.30 or less, more preferably 0.25 or less, Most preferably, it is 0.20 or less.

  In the composition range of the above formula (I), the closer the z value is to the lower limit that is a constant ratio, the lower the rate characteristics and output characteristics of the battery, and the lower the z value is to the upper limit, Although the rate characteristics and output characteristics of the battery are improved, there is a tendency for the capacity to decrease. Moreover, the lower the x value, that is, the closer the manganese / nickel atomic ratio is to 1, the lower the charging voltage, the higher the capacity, but the tendency is seen that the cycle characteristics and safety of batteries with a high charging voltage are lowered, and vice versa. In addition, the closer the x value is to the upper limit, the more the cycle characteristics and safety of the battery set at a higher charge voltage are improved, while the discharge capacity, rate characteristics, and output characteristics tend to decrease. Also, the closer the y value is to the lower limit, the lower the load characteristics such as rate characteristics and output characteristics when the battery is used, and conversely, the closer the y value is to the upper limit, the rate characteristics when the battery is used. However, the cycle characteristics and safety when set at a high charge voltage are lowered, and the raw material cost tends to be high. The present invention has been completed as a result of intensive studies to overcome these conflicting trends, and it is important that the composition parameters x, y, and z are within the specified ranges.

  In the composition of the formula (I), the atomic ratio of the oxygen amount is described as 2 for convenience, but there may be some non-stoichiometry. For example, the atomic ratio of oxygen can be in the range of 2 ± 0.1.

  In the lithium nickel manganese cobalt based composite oxide powder of the present invention, a substitution element may be introduced into the structure. The substitution element is selected from any one or more of Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn, Nb, Zr, Mo, W, and Sn. These substitution elements are appropriately replaced with Ni, Mn, and Co elements within a range of 20 atomic% or less.

<Powder X-ray diffraction peak>
The lithium nickel manganese cobalt based composite oxide powder of the present invention preferably has no diffraction peak at 2θ = 31 ± 1 ° in a powder X-ray diffraction pattern using CuKα rays. Here, “does not include” includes those having a diffraction peak that does not adversely affect the battery performance of the present invention. That is, this diffraction peak is derived from the spinel phase, but if the spinel phase is included, the capacity, rate characteristics, high-temperature storage characteristics, and high-temperature cycle characteristics of the battery are reduced. For this reason, the diffraction peak may have a diffraction peak that does not adversely affect the battery performance of the present invention, but 2θ = 31 on the basis of the (003) peak area of 2θ = 18.5 ± 1 °. The diffraction peak area at ± 1 ° is preferably 0.5% or less, more preferably 0.2% or less, and particularly preferably no diffraction peak at all. In other words, this diffraction peak is derived from the spinel phase, and if the spinel phase is included, the capacity, rate characteristics, high-temperature storage characteristics, and high-temperature cycle characteristics of the battery tend to deteriorate, so there is no such diffraction peak. Is preferred.

<Crystal structure>
In addition, the lithium nickel manganese cobalt based composite oxide powder of the present invention has a crystal structure including a layered R (-3) m structure, and a lattice constant of 2.855Å ≦ a ≦ 2.870Å, 14. It is preferable to be in the range of 235 Å ≦ c ≦ 14.265 Å. In the present invention, the crystal structure and lattice constant can be obtained by powder X-ray diffraction measurement using CuKα rays.

<Contained carbon concentration C>
The C value of the lithium nickel manganese cobalt based composite oxide powder of the present invention is usually 0.030% by weight or less, preferably 0.025% by weight or less, more preferably 0.020% by weight or less. It is 001% by weight or more, preferably 0.004% by weight or more, more preferably 0.010% by weight or more. If the C value exceeds this upper limit, swelling due to gas generation when the battery is produced may increase or the battery performance may decrease, and if the C value is less than the lower limit, the battery performance may decrease.

  In the present invention, the carbon concentration C of the lithium nickel manganese cobalt-based composite oxide powder is determined by measurement using an oxygen gas combustion (high-frequency heating furnace type) infrared absorption method, as shown in the Examples section below. be able to.

  In addition, from the concentration of carbon contained in the lithium nickel manganese cobalt composite oxide powder obtained by carbon analysis described later, a numerical value assuming that all of the carbon is derived from carbonate ions, and the lithium nickel manganese cobalt composite analyzed by ion chromatography Since the carbonate ion concentration value in the oxide powder is almost the same, the carbon is considered to exist as a carbonate, and therefore the C value indicates information on the amount of carbonate compound, particularly lithium carbonate. It can be regarded as a thing.

  On the other hand, in the lithium nickel manganese cobalt based composite oxide powder defined by the present invention, a very small amount of lithium is present as a carbonate, which affects the lithium composition (x, z) defined by the composite oxide powder. Not give.

<Volume resistivity>
The volume resistivity value when the lithium nickel manganese cobalt based composite oxide powder of the present invention is compacted at a pressure of 40 MPa is usually 5 × 10 ⁵ Ω · cm or less, preferably 2 × 10 ⁵ Ω · cm or less, More preferably, it is 1 × 10 ⁵ Ω · cm or less, and particularly preferably 5 × 10 ⁴ Ω · cm or less. If this volume resistivity exceeds this upper limit, the rate characteristics and low-temperature characteristics of the battery may be reduced. The lower limit of the volume resistivity is usually 5 × 10 ¹ Ω · cm or more, preferably 1 × 10 ² Ω · cm or more, more preferably 5 × 10 ² Ω · cm or more, and most preferably 1 × 10 ³ Ω · cm. That's it. If the volume resistivity is below this lower limit, the safety of the battery may be reduced.

  In the present invention, the volume resistivity of the lithium nickel manganese cobalt based composite oxide powder is four probe / ring electrode, electrode spacing 5.0 mm, electrode radius 1.0 mm, sample radius 12.5 mm, and applied voltage. It is a volume resistivity measured in a state where the limiter is 90 V and the lithium nickel manganese cobalt based composite oxide powder is compacted at a pressure of 40 MPa. The volume resistivity is measured by, for example, using a powder resistivity measuring device (eg, manufactured by Dia Instruments Co., Ltd .: Lorester GP powder resistivity measuring system), using a powder probe unit, to form a powder under a predetermined pressure. Can be done against.

<The bulk density>
The bulk density of the lithium nickel manganese cobalt based composite oxide powder of the present invention is usually 1.5 g / cc or more, preferably 1.7 g / cc or more, more preferably 1.9 g / cc or more, most preferably 2.0 g. / Cc or more. Below this lower limit, powder filling properties and electrode preparation are adversely affected, and a positive electrode using this as an active material is not preferable because the capacity density per unit volume becomes too small. Further, the upper limit of the bulk density is usually 3 g / cc or less, preferably 2.8 g / cc or less, more preferably 2.6 g / cc or less. While it is preferable for the bulk density to exceed this upper limit, it is preferable for improving powder filling properties and electrode density. On the other hand, the specific surface area may become too low, which is not preferable because battery performance deteriorates.

  In the present invention, the bulk density is a powder packing density (tap density) when 5 to 10 g of lithium nickel manganese cobalt based composite oxide powder is put in a 10 ml glass graduated cylinder and tapped 200 times with a stroke of about 20 mm. ) G / cc was determined.

<Average primary particle size>
The average primary particle diameter of the lithium nickel manganese cobalt based composite oxide powder of the present invention is usually 0.1 μm or more, preferably 0.2 μm or more, more preferably 0.3 μm or more, and most preferably 0.4 μm or more. Usually, it is 3 μm or less, preferably 2 μm or less, more preferably 1.5 μm or less, and most preferably 1.0 μm or less. If the above upper limit is exceeded, it will be difficult to form spherical secondary particles, which will adversely affect powder filling properties and the specific surface area will be greatly reduced, which may reduce battery performance such as rate characteristics and output characteristics. Is unfavorable because of the high. Below the lower limit, the crystal is undeveloped, which may cause problems such as poor reversibility of charge / discharge, which is not preferable.

  In addition, the average particle diameter of the primary particle in this invention is an average diameter observed with the scanning electron microscope (SEM), and the particle diameter of about 10-30 primary particles using a 30,000 times SEM image. It can be calculated as an average value.

<Median diameter of secondary particles and 90% integrated diameter ( _D90 )>
The lithium nickel manganese cobalt based composite oxide powder of the present invention preferably has a layered structure, and primary particles are aggregated and sintered to form secondary particles.

  The median diameter of secondary particles of the lithium nickel manganese cobalt based composite oxide powder of the present invention is usually 3 μm or more, preferably 5 μm or more, more preferably 9 μm or more, most preferably 10 μm or more, and usually 20 μm or less, preferably 18 μm. Below, more preferably 16 μm or less, most preferably 15 μm or less. If the above lower limit is not reached, a high bulk density product may not be obtained, and if the upper limit is exceeded, battery performance may be deteriorated, or there may be a problem in applicability during the formation of the positive electrode active material layer. .

The 90% cumulative diameter (D ₉₀ ) of the secondary particles of the lithium nickel manganese cobalt composite oxide powder of the present invention is usually 30 μm or less, preferably 26 μm or less, more preferably 23 μm or less, and most preferably 20 μm or less. Usually, it is 5 μm or more, preferably 8 μm or more, more preferably 12 μm or more, and most preferably 15 μm or more. If the above upper limit is exceeded, battery performance may be deteriorated, and there may be a problem in applicability at the time of forming the positive electrode active material layer, and if it is below the lower limit, a high bulk density product may not be obtained.

In the present invention, the median diameter and the 90% integrated diameter (D ₉₀ ) as the average particle diameter are set to a refractive index of 1.24 using a known laser diffraction / scattering particle size distribution measuring device, and the particle diameter standard is determined. Measured as a volume reference. In the present invention, a 0.1 wt% sodium hexametaphosphate aqueous solution was used as a dispersion medium used in the measurement, and the measurement was performed after ultrasonic dispersion for 5 minutes.

<BET specific surface area>
The lithium nickel manganese cobalt based composite oxide powder of the present invention also has a BET specific surface area of usually 0.2 m ² / g or more, preferably 0.3 m ² / g or more, more preferably 0.4 m ² / g or more. , Most preferably 0.5 m ² / g or more, usually 3.0 m ² / g or less, preferably 1.5 m ² / g or less, more preferably 1.2 m ² / g or less, most preferably 1.0 m ^2. / G or less. If the BET specific surface area is smaller than this range, the battery performance tends to be lowered, and if it is larger, the bulk density is difficult to increase, or a problem is likely to occur in the coating property when forming the positive electrode active material layer.

  The BET specific surface area can be measured by a known BET type powder specific surface area measuring device. In the present invention, an OMS Riken: AMS8000 type automatic powder specific surface area measuring device was used, nitrogen was used as an adsorption gas, and helium was used as a carrier gas. Specifically, the powder sample was heated and deaerated with a mixed gas at a temperature of 150 ° C., then cooled to liquid nitrogen temperature to adsorb the mixed gas, and then heated to room temperature with water to be adsorbed. Nitrogen gas was desorbed, the amount was detected by a thermal conductivity detector, and the specific surface area of the sample was calculated from this.

[Method for producing lithium nickel manganese cobalt based composite oxide powder]
The production method of the lithium nickel manganese cobalt based composite oxide powder of the present invention is not limited to a specific production method. For example, a slurry in which a nickel compound, a manganese compound, and a cobalt compound are dispersed in a liquid medium. Can be spray dried and / or pyrolyzed, mixed with a lithium compound, and the mixture can be fired.

  Hereinafter, a method for producing the lithium nickel manganese cobalt based composite oxide powder of the present invention will be described in detail.

Among the raw material compounds used for the preparation of the slurry for producing lithium nickel manganese cobalt based composite oxide powder by the method of the present invention, the nickel compounds include Ni (OH) ₂ , NiO, NiOOH, NiCO ₃ .2Ni. (OH) ₂ .4H ₂ O, NiC ₂ O ₄ .2H ₂ O, Ni (NO ₃ ) ₂ .6H ₂ O, NiSO ₄ , NiSO ₄ .6H ₂ O, fatty acid nickel, nickel halide and the like. Among these, Ni (OH) ₂ , NiO, NiOOH, NiCO ₃ .2Ni (OH) ₂ .4H ₂ O, and NiC ₂ O _{4 are} not used in the generation of harmful substances such as SO _x and NO _x during the firing process. -Nickel compounds such as 2H ₂ O are preferred. Further, Ni (OH) ₂ , NiO, and NiOOH are particularly preferable from the viewpoint of being available as an industrial raw material at a low cost and having a high reactivity. These nickel compounds may be used individually by 1 type, and may use 2 or more types together.

As manganese compounds, manganese oxides such as Mn ₂ O ₃ , MnO ₂ , Mn ₃ O ₄ , MnCO ₃ , Mn (NO ₃ ) ₂ , MnSO ₄ , manganese acetate, manganese dicarboxylate, manganese citrate, manganese fatty acid And manganese salts such as oxyhydroxide, manganese chloride and the like. Among these manganese compounds, MnO ₂ , Mn ₂ O ₃ , and Mn ₃ O ₄ do not generate gases such as SO _x , NO _x , and CO ₂ during firing, and can be obtained at low cost as industrial raw materials. Therefore, it is preferable. These manganese compounds may be used individually by 1 type, and may use 2 or more types together.

Cobalt compounds include Co (OH) ₂ , CoOOH, CoO, Co ₂ O ₃ , Co 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, and the like. Among them, Co (OH) ₂ , CoOOH, CoO, Co ₂ O ₃ , and Co ₃ O ₄ are preferable in terms of not generating harmful substances such as SO _x and NO _x during the firing step, and more preferably industrially. Co (OH) ₂ and CoOOH are available at a low cost and highly reactive. These cobalt compounds may be used individually by 1 type, and may use 2 or more types together.

  The method for mixing the raw materials is not particularly limited, and may be wet or dry. For example, a method using an apparatus such as a ball mill, a vibration mill, or a bead mill can be used. Wet mixing is preferable because more uniform mixing is possible and the reactivity of the mixture can be increased in the firing step. As the dispersion medium used in the wet method, either an organic solvent or water can be used, but water is preferably used.

  The mixing time varies depending on the mixing method, but it is sufficient that the raw materials are uniformly mixed at the particle level. For example, in a ball mill (wet or dry type), usually about 1 to 2 days, and in a bead mill (wet continuous method), a residence time. Is usually about 0.1 to 6 hours.

  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 0.5 μm or less, preferably 0.3 μm or less, more preferably 0.25 μm or less, most preferably Preferably it is 0.20 μm or less. If the average particle size of the pulverized raw material particles is too large, the reactivity in the firing step is lowered, and it is difficult to make the composition uniform. 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 dyno mill. The median diameter of the pulverized particles in the slurry described in the examples described later is set to a refractive index of 1.24 using a known laser diffraction / scattering particle size distribution measuring apparatus, and the particle diameter reference is set to the volume reference. Measured. In the present invention, a 0.1 wt% sodium hexametaphosphate aqueous solution was used as a dispersion medium used in the measurement, and the measurement was performed after ultrasonic dispersion for 5 minutes.

  After the wet mixing, it is then usually subjected to a drying and / or pyrolysis step. The drying 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 the ability to efficiently form spherical secondary particles.

  In the method for producing lithium nickel manganese cobalt based composite oxide powder of the present invention, primary particles are aggregated by pulverization to an average particle size of 0.3 μm or less by wet pulverization, followed by spray drying and / or thermal decomposition. Thus, it is preferable to obtain a powder obtained by forming solid secondary particles. Lithium nickel manganese, which is basically obtained by further mixing and firing with Li raw material, although the shape characteristics of the powder formed by agglomeration of primary particles to form solid secondary particles vary in particle size. This is also reflected in the cobalt-based composite oxide powder. Examples of the shape confirmation method include SEM observation and cross-sectional SEM observation.

  The average particle size of the powder obtained by spray drying and / or thermal decomposition is usually 50 μm or less, more preferably 40 μm or less, and most preferably 30 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 5 μm or more, more preferably 6 μm or more. In the case of producing a particulate material by the spray drying method, the particle size can be controlled by appropriately selecting the spray format, the pressurized gas flow supply rate, the slurry supply rate, the drying temperature, and the like.

Further, when the particulate matter obtained by spray drying and / or thermal decomposition has a small specific surface area, a lithium nickel manganese cobalt based composite oxide is produced by a firing reaction with a lithium compound in the next step. As described above, it is preferable that the specific surface area be increased as much as possible by means such as pulverizing the starting material before spray drying and / or thermal decomposition. On the other hand, excessively high specific surface area is industrially disadvantageous. Therefore, the powder particles obtained by spray drying and / or pyrolysis are usually 20 m ² / g or more, preferably 30 m ² / g or more, more preferably 40 m ² / g or more, and more preferably in terms of BET specific surface area. It is preferably 50 m ² / g or more, most preferably 60 m ² / g or more, and usually 200 m ² / g or less, preferably 150 m ² / g or less.

Examples of the lithium compound mixed with the granulated particles obtained by spray drying and / or thermal decomposition 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, citrate Li, fatty acid Li, alkyllithium and the like. Among these lithium compounds, lithium compounds that do not contain nitrogen atoms or sulfur atoms are preferred because they do not generate harmful substances such as SO _x and NO _x during the firing treatment. In view of reducing the carbon concentration C as much as possible, it is a compound that does not contain a carbon atom. Taking these points into consideration, LiOH and LiOH.H ₂ O are particularly preferable. These lithium compounds are used alone. Two or more kinds may be used in combination.

  As the particle size of such a lithium compound, the average particle size is usually 500 μm or less, preferably in order to improve the mixing performance with a mixture containing a nickel raw material, a manganese raw material, and a cobalt raw material, and to improve battery performance. Is 100 μm or less, more preferably 50 μm or less, still more preferably 20 μm or less, and most preferably 10 μm or less. On the other hand, those having a too small particle size have a mean particle size of usually 0.01 μm or more, preferably 0.1 μm or more, more preferably 0.2 μm or more, and most preferably 0 because the stability in the air is low. .5 μm or more. The median diameter as the average particle diameter of lithium hydroxide used as a raw material in the examples described later is set to a refractive index of 1.14 using a known laser diffraction / scattering particle size distribution measuring device, and the particle diameter standard is Measured as a volume reference. In this measurement, ethyl alcohol was used as a dispersion medium used in the measurement to obtain a saturated lithium hydroxide solution, and the measurement was performed after ultrasonic dispersion for 5 minutes.

  It is important to sufficiently mix the powder obtained by spray drying and / or pyrolysis with the lithium compound. The mixing method is not particularly limited as long as it can be sufficiently mixed, but it is preferable to use a powder mixing apparatus generally used for industrial purposes. The atmosphere in the system to be mixed is preferably an inert gas atmosphere such as nitrogen gas or argon gas in order to prevent carbon dioxide absorption in the air.

  The mixed powder thus obtained is then fired. 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, the primary particles grow too much. Conversely, if the firing temperature is too low, the bulk density is small and the specific surface area is large. Too much. The firing temperature is usually 800 ° C. or higher, preferably 900 ° C. or higher, more preferably 950 ° C. or higher, usually 1100 ° C. or lower, preferably 1075 ° C. or lower, more preferably 1050 ° 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 crushing step meaning crushing to primary particles or even fine powder.

  In the temperature raising step, the temperature in the furnace is usually raised at a temperature raising rate of 1 ° C./min to 10 ° C./min. Even if this rate of temperature rise is too slow, it takes time and is industrially disadvantageous. However, if it is too fast, the furnace temperature does not follow the set temperature depending on the furnace. The temperature rising rate is preferably 2 ° C./min or more, more preferably 3 ° C./min or more, preferably 10 ° C./min or less, more preferably 5 ° C./min or less.

  Although the holding time in the maximum temperature holding step varies depending on the temperature, it is usually 30 minutes or longer, preferably 5 hours or longer, more preferably 10 hours or longer, 50 hours or shorter, preferably 25 hours within the aforementioned temperature range. Hereinafter, it is more preferably 20 hours or less. If the firing time is too short, it becomes difficult to obtain a lithium nickel manganese cobalt composite oxide powder having good crystallinity, and it is not practical to be too long. If the firing time is too long, it will be disadvantageous because it will be necessary to crush afterwards or it will be difficult to crush.

  In the temperature lowering step, the temperature in the furnace is normally decreased at a temperature decreasing rate of 0.1 ° C./min to 10 ° C./min. If the temperature drop is too slow, it takes time and is industrially disadvantageous, but if it is too fast, it tends to lack uniformity of the target product or accelerate deterioration of the container. The temperature lowering rate is preferably 1 ° C./min or more, more preferably 3 ° C./min or more, preferably 10 ° C./min or less, more preferably 5 ° C./min or less.

  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.

  In such a production method, in order to produce the lithium nickel manganese cobalt-based composite oxide powder having the specific composition of the present invention, the nickel compound, the manganese compound, and the cobalt are prepared under the same production conditions. Lithium when adjusting the mixing ratio of each compound when preparing a slurry in which the compound is dispersed in a liquid medium, and mixing the lithium compound with the granulated particles obtained by spray drying and / or thermal decomposition of this slurry By adjusting the mixing ratio of the compounds, the target Li / Ni / Mn / M molar ratio can be controlled.

  According to the lithium nickel manganese cobalt based composite oxide powder obtained in this way, there is little swelling due to gas generation, high capacity, excellent rate characteristics, low temperature output characteristics, excellent storage characteristics, and a balance of performance. A positive electrode material for a lithium secondary battery is provided.

[Positive electrode for lithium secondary battery]
The positive electrode for a lithium secondary battery of the present invention is formed by forming a positive electrode active material layer containing a lithium nickel manganese cobalt composite oxide powder for a lithium secondary battery positive electrode material of the present invention and a binder on a current collector. It will be.

  The positive electrode active material layer is usually formed by mixing a positive electrode material, a binder, and a conductive material and a thickener, which are used if necessary, in a dry form into a sheet shape, and then pressing the positive electrode current collector on the positive electrode current collector. Alternatively, these materials are dissolved or dispersed in a liquid medium to form a slurry, which is applied to the positive electrode current collector and dried.

  As the material for the positive electrode current collector, metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum, and carbon materials such as carbon cloth and carbon paper are usually used. Of these, metal materials are preferable, and aluminum is particularly preferable. As for the shape, in the case of a metal material, a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, an expanded metal, a punch metal, a foam metal, etc., and in the case of a carbon material, a carbon plate, a carbon thin film, a carbon cylinder Etc. Among these, metal thin films are preferable because they are currently used in industrialized products. In addition, you may form a thin film suitably in mesh shape.

  When a thin film is used as the positive electrode current collector, its thickness is arbitrary, but it is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and usually 100 mm or less, preferably 1 mm or less, more preferably 50 μm or less. The range of is preferable. If the thickness is thinner than the above range, the strength required for the current collector may be insufficient. On the other hand, if it is thicker than the above range, the handleability may be impaired.

  The binder used in the production of the positive electrode active material layer is not particularly limited, and in the case of a coating method, any material that is stable with respect to the liquid medium used during electrode production may be used. Specific examples include polyethylene, Resin polymers such as polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, nitrocellulose, SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), fluorine rubber, isoprene rubber, butadiene rubber, ethylene・ Rubber polymers such as propylene rubber, styrene / butadiene / styrene block copolymer and hydrogenated products thereof, EPDM (ethylene-propylene-diene terpolymer), styrene / ethylene / butadiene / ethylene copolymer, Styrene / isoprene styrene bromide Copolymer and its hydrogenated thermoplastic elastomeric polymer, syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinyl acetate copolymer, propylene / α-olefin copolymer, etc. Fluorine polymers such as soft resinous polymers, polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymers, ion conductivity of alkali metal ions (especially lithium ions) And a polymer composition having the same. These substances may be used alone or in combination of two or more in any combination and ratio.

  The ratio of the binder in the positive electrode active material layer is usually 0.1% by weight or more, preferably 1% by weight or more, more preferably 5% by weight or more, and usually 80% by weight or less, preferably 60% by weight or less. More preferably, it is 40% by weight or less, and most preferably 10% by weight or less. If the proportion of the binder is too low, the positive electrode active material cannot be sufficiently retained, and the mechanical strength of the positive electrode may be insufficient, and the battery performance such as cycle characteristics may be deteriorated. There is a possibility that it may lead to a decrease in capacity and conductivity.

  The positive electrode active material layer usually contains a conductive material in order to increase conductivity. There are no particular restrictions on the type of conductive material, but specific examples include metal materials such as copper and nickel, graphite such as natural graphite and artificial graphite, carbon black such as acetylene black, and amorphous such as needle coke. Examples thereof include carbon materials such as carbon. In addition, these substances may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios. The proportion of the conductive material in the positive electrode active material layer is usually 0.01% by weight or more, preferably 0.1% by weight or more, more preferably 1% by weight or more, and usually 50% by weight or less, preferably 30%. % By weight or less, more preferably 15% by weight or less. If the proportion of the conductive material is too low, the conductivity may be insufficient, and conversely if it is too high, the battery capacity may be reduced.

  The liquid medium for forming the slurry is to dissolve or disperse the lithium nickel manganese cobalt composite oxide powder, which is the positive electrode material, the binder, and the conductive material and thickener used as necessary. As long as the solvent can be used, the type is not particularly limited, and either an aqueous solvent or an organic solvent may be used. Examples of the aqueous solvent include water and alcohol. Examples of the organic solvent include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N -N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran (THF), toluene, acetone, dimethyl ether, dimethylacetamide, hexamethylphosphalamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane, etc. be able to. In particular, when an aqueous solvent is used, a dispersant is added together with the thickener, and a slurry such as SBR is slurried. In addition, these solvents may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  The content ratio of the lithium nickel manganese cobalt composite oxide powder of the present invention as the positive electrode material in the positive electrode active material layer is usually 10% by weight or more, preferably 30% by weight or more, more preferably 50% by weight or more. Usually, it is 99.9% by weight or less, preferably 99% by weight or less. If the proportion of the lithium nickel manganese cobalt composite oxide powder in the positive electrode active material layer is too large, the strength of the positive electrode tends to be insufficient, and if it is too small, the capacity may be insufficient.

  The thickness of the positive electrode active material layer is usually about 10 to 200 μm.

  The positive electrode active material layer obtained by applying the slurry to the positive electrode current collector and drying is preferably consolidated by a roller press or the like in order to increase the packing density of the positive electrode active material.

[Lithium secondary battery]
The lithium secondary battery of the present invention includes the above-described positive electrode for a lithium secondary battery of the present invention capable of occluding and releasing lithium, a negative electrode capable of occluding and releasing lithium, and a non-aqueous electrolyte using a lithium salt as an electrolytic salt, Is provided. Further, a separator for holding a nonaqueous electrolyte may be provided between the positive electrode and the negative electrode. In order to effectively prevent a short circuit due to contact between the positive electrode and the negative electrode, it is desirable to interpose a separator in this way.

<Negative electrode>
The negative electrode is usually configured by forming a negative electrode active material layer on a negative electrode current collector, similarly to the positive electrode.

  As a material of the negative electrode current collector, a metal material such as copper, nickel, stainless steel, nickel-plated steel, or a carbon material such as carbon cloth or carbon paper is used. Examples of the shape include a metal foil, a metal cylinder, a metal coil, a metal plate, and a metal thin film in the case of a metal material, and a carbon plate, a carbon thin film, and a carbon cylinder in the case of a carbon material. Among these, metal thin films are preferable because they are currently used in industrialized products. In addition, you may form a thin film suitably in mesh shape. When a metal thin film is used as the negative electrode current collector, the preferred thickness range is the same as the range described above for the positive electrode current collector.

  The negative electrode active material layer includes a negative electrode active material. The negative electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions, but it can usually occlude and release lithium from the viewpoint of high safety. A carbon material is used.

  Although there is no restriction | limiting in particular as a carbon material, Graphite (graphite), such as artificial graphite and natural graphite, and the thermal decomposition thing of organic substance on various thermal decomposition conditions are mentioned. Examples of pyrolysis products of organic matter include coal-based coke, petroleum-based coke, coal-based pitch carbide, petroleum-based pitch carbide, or carbide obtained by oxidizing these pitches, needle coke, pitch coke, phenol resin, crystalline cellulose, etc. And carbon materials obtained by partially graphitizing these, furnace black, acetylene black, pitch-based carbon fibers, and the like. Among them, graphite is preferable, and particularly preferable is artificial graphite, purified natural graphite, or graphite material containing pitch in these graphites, which is manufactured by subjecting easy-graphite pitch obtained from various raw materials to high-temperature heat treatment. Therefore, those subjected to various surface treatments are mainly used. One of these carbon materials may be used alone, or two or more thereof may be used in combination.

  When a graphite material is used as the negative electrode active material, the d value (interlayer distance) of the lattice plane (002 plane) determined by X-ray diffraction by the Gakushin method is usually 0.335 nm or more, and usually 0.34 nm or less, preferably Is preferably 0.337 nm or less.

  Further, the ash content of the graphite material is usually 1% by weight or less, particularly 0.5% by weight or less, and particularly preferably 0.1% by weight or less, based on the weight of the graphite material.

  Further, the crystallite size (Lc) of the graphite material determined by X-ray diffraction by the Gakushin method is usually 30 nm or more, preferably 50 nm or more, and particularly preferably 100 nm or more.

  The median diameter of the graphite material determined by the laser diffraction / scattering method is usually 1 μm or more, especially 3 μm or more, more preferably 5 μm or more, especially 7 μm or more, and usually 100 μm or less, especially 50 μm or less, more preferably 40 μm or less, especially 40 μm or less. It is preferable that it is 30 micrometers or less.

Moreover, the BET specific surface area of the graphite material is usually 0.5 m ² / g or more, preferably 0.7 m ² / g or more, more preferably 1.0 m ² / g or more, and further preferably 1.5 m ² / g. or more, and usually 25.0 m ² / g or less, preferably 20.0 m ² / g, more preferably 15.0 m ² / g or less, still more preferably 10.0 m ² / g or less.

Further, when performing Raman spectroscopy using argon laser light for graphite material, and strength _{I A} of the peak _{P A} is detected in the range of 1580～1620Cm ^-1, is detected in the range of 1350 ^-1 that intensity ratio _I a / _{I B} of the intensity _{I B} of a peak _{P B} is what is preferably 0 to 0.5. Further, the half width of the peak _{P A} is preferably 26cm ^-1 or less, 25 cm ^-1 or less is more preferable.

  In addition to the various carbon materials described above, other materials capable of inserting and extracting lithium can be used as the negative electrode active material. Specific examples of the negative electrode active material other than the carbon material include metal oxides such as tin oxide and silicon oxide, sulfides and nitrides, and lithium alloys such as lithium alone and lithium aluminum alloys. As for materials other than these carbon materials, one kind may be used alone, or two or more kinds may be used in combination. Moreover, you may use in combination with the above-mentioned carbon material.

  As in the case of the positive electrode active material layer, the negative electrode active material layer is usually prepared by slurrying the above-described negative electrode active material, a binder, and optionally a conductive material and a thickener in a liquid medium. It can manufacture by apply | coating to a negative electrode electrical power collector, and drying. As the liquid medium, the binder, the thickener, the conductive material and the like forming the slurry, the same materials as those described above for the positive electrode active material layer can be used at the same ratio.

<Nonaqueous electrolyte>
As the non-aqueous electrolyte, for example, known organic electrolytes, polymer solid electrolytes, gel electrolytes, inorganic solid electrolytes, and the like can be used. Of these, organic electrolytes are preferable. The organic electrolytic solution is configured by dissolving a solute (electrolyte) in an organic solvent.

  Here, the type of the organic solvent is not particularly limited. For example, carbonates, ethers, ketones, sulfolane compounds, lactones, nitriles, chlorinated hydrocarbons, ethers, amines, esters, amides. A phosphoric acid ester compound or the like can be used. Typical examples are dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propylene carbonate, ethylene carbonate, vinylene carbonate, tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 4-methyl-2-pentanone, 1, 2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, 1,3-dioxolane, 4-methyl-1,3-dioxolane, diethyl ether, sulfolane, methylsulfolane, acetonitrile, propionitrile, benzonitrile, Examples include butyronitrile, valeronitrile, 1,2-dichloroethane, dimethylformamide, dimethyl sulfoxide, trimethyl phosphate, triethyl phosphate, and the like alone or in combination. Mixed solvents can be used.

  The organic solvent described above preferably contains a high dielectric constant solvent in order to dissociate the electrolytic salt. Here, the high dielectric constant solvent means a compound having a relative dielectric constant of 20 or more at 25 ° C. Among the high dielectric constant solvents, it is preferable that ethylene carbonate, propylene carbonate, and compounds in which hydrogen atoms thereof are substituted with other elements such as halogen or alkyl groups are contained in the electrolytic solution. The proportion of the high dielectric constant solvent in the electrolytic solution is preferably 20% by weight or more, more preferably 30% by weight or more, and most preferably 40% by weight or more. If the content of the high dielectric constant solvent is less than the above range, desired battery characteristics may not be obtained.

In addition, in the organic electrolyte, a gas such as CO ₂ , N ₂ O, CO, and SO ₂ , vinylene carbonate, polysulfide S _x ^{2−, and the} like that enables efficient charge and discharge of lithium ions on the negative electrode surface You may add the additive which forms a film in arbitrary ratios. Of these, vinylene carbonate is particularly preferable.

The type of the electrolytic salt is not particularly limited, and any conventionally known solute can be used. Specific examples include LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiB (C ₆ H ₅ ) ₄ , LiBOB, LiCl, LiBr, CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiC (SO ₂ CF ₃ ) ₃ , LiN (SO ₃ CF ₃ ) _{2 and the} like. Any one of these electrolytic salts may be used alone, or two or more thereof may be used in any combination and ratio.

  The lithium salt of the electrolytic salt is usually contained in the electrolytic solution so as to have a concentration of 0.5 mol / L to 1.5 mol / L. Even if this concentration is less than 0.5 mol / L or more than 1.5 mol / L, the electric conductivity may be lowered, and the battery characteristics may be adversely affected. The lower limit of the electrolytic salt concentration is preferably 0.75 mol / L or more and the upper limit is 1.25 mol / L or less.

Even when a polymer solid electrolyte is used, the type thereof is not particularly limited, and any known crystalline / amorphous inorganic substance can be used as the solid electrolyte. Examples of the crystalline inorganic solid electrolyte include LiI, Li ₃ N, Li _{1 + x} J _x Ti _2-x (PO ₄ ) ₃ (J = Al, Sc, Y, La), Li _0.5-3x RE _{0. .5 + x} TiO ₃ (RE = La, Pr, Nd, Sm) and the like. Examples of the amorphous inorganic solid electrolyte include oxide glasses such as 4.9LiI-34.1Li ₂ O-61B ₂ O ₅ and 33.3Li ₂ O-66.7SiO ₂ . Any one of these may be used alone, or two or more may be used in any combination and ratio.

<Separator>
When the above-described organic electrolyte is used as the electrolyte, a separator is interposed between the positive electrode and the negative electrode in order to prevent a short circuit between the electrodes. The material and shape of the separator are not particularly limited, but those that are stable with respect to the organic electrolyte used, have excellent liquid retention properties, and can reliably prevent short-circuiting between electrodes are preferable. Preferable examples include microporous films, sheets, nonwoven fabrics and the like made of various polymer materials. Specific examples of the polymer material include polyolefin polymers such as nylon, cellulose acetate, nitrocellulose, polysulfone, polyacrylonitrile, polyvinylidene fluoride, polypropylene, polyethylene, and polybutene. In particular, from the viewpoint of chemical and electrochemical stability, which is an important factor for separators, polyolefin polymers are preferable. From the viewpoint of self-occluding temperature, which is one of the purposes of use of separators in batteries, polyethylene is preferred. Is particularly desirable.

  When using a separator made of polyethylene, it is preferable to use ultra-high molecular weight polyethylene from the viewpoint of maintaining high-temperature shape, and the lower limit of the molecular weight is preferably 500,000, more preferably 1,000,000, and most preferably 1,500,000. On the other hand, the upper limit of the molecular weight is preferably 5 million, more preferably 4 million, and most preferably 3 million. This is because if the molecular weight is too large, the fluidity becomes too low, and the pores of the separator may not close when heated.

<Battery shape>
The lithium secondary battery of the present invention is manufactured by assembling the above-described positive electrode for a lithium secondary battery of the present invention, a negative electrode, a nonaqueous electrolyte, and a separator used as necessary into an appropriate shape. . Furthermore, other components such as an outer case can be used as necessary.

  The shape of the lithium secondary battery of the present invention is not particularly limited, and can be appropriately selected from various commonly employed shapes according to the application. Examples of commonly used shapes include a cylinder type with a sheet electrode and separator in a spiral shape, a cylinder type with an inside-out structure combining a pellet electrode and a separator, and a coin type with stacked pellet electrodes and a separator. Can be mentioned.

  The method for assembling the battery is not particularly limited, and can be appropriately selected from various commonly used methods according to the shape of the target battery.

<Charge potential of the positive electrode when fully charged>
The lithium secondary battery of the present invention is preferably designed so that the charging potential of the positive electrode in a fully charged state is 4.4 V (vs. Li ^/ Li ⁺ ) or higher. That is, when the lithium nickel manganese cobalt based composite oxide powder for a lithium secondary battery positive electrode material of the present invention is used as a lithium secondary battery designed to be charged at a high charging potential according to the specific composition described above. In this case, the effect of improving the cycle characteristics and safety is effectively exhibited. However, it is also possible to use this charging potential as less than 4.4V.

  The general embodiment of the lithium secondary battery of the present invention has been described above. However, the lithium secondary battery of the present invention is not limited to the above-described embodiment, and various modifications are possible as long as the gist thereof is not exceeded. Can be implemented.

  EXAMPLES The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples unless it exceeds the gist.

[Measurement method of physical properties]
The physical properties and the like of lithium nickel manganese cobalt based composite oxide powders manufactured in each of Examples and Comparative Examples described below were measured as follows.

Composition (Li / Ni / Mn / Co):
It was determined by ICP-AES analysis.

Crystal phase:
It calculated | required by the powder X-ray-diffraction pattern using a CuK alpha ray.
(Powder X-ray diffraction measurement device) PANalytical PW1700
(Measurement conditions) X-ray output: 40 kV, 30 mA, scanning axis: θ / 2θ
Scanning range (2θ): 10.0-90.0 °
Measurement mode: Continuous
Reading width: 0.05 °
Scanning speed: 3.0 ° / min.
Slit: DS 1 °, SS 1 °, RS 0.2mm

Lattice constant:
Powder X-ray diffraction measurement using the CuKα ray was performed, and (hkl) = (003), (101), (006), (012) among diffraction planes belonging to the layered R (−3) m structure. , (104), (015), (107), (108), (110), and (113).

Specific surface area:
Okura Riken: AMS8000 type fully automatic powder specific surface area measuring device was used, nitrogen was used as the adsorption gas, and helium was used as the carrier gas, and BET one-point method measurement was performed by the continuous flow method. Specifically, the powder sample was heated and deaerated with a mixed gas at a temperature of 150 ° C., then cooled to liquid nitrogen temperature to adsorb the mixed gas, and then heated to room temperature with water to be adsorbed. Nitrogen gas was desorbed, the amount was detected by a thermal conductivity detector, and the specific surface area of the sample was calculated from this.

Average primary particle size:
Using an SEM image of 30,000 times, the average particle size of about 10 to 30 primary particles was obtained.

Secondary median diameter and 90% cumulative diameter ( _D90 ):
A refractive index of 1.24 was set using a laser diffraction / scattering particle size distribution measuring apparatus, and the particle diameter standard was measured as a volume standard. As a dispersion medium used in the measurement, a 0.1 wt% sodium hexametaphosphate aqueous solution was used, and measurement was performed after ultrasonic dispersion for 5 minutes.

The bulk density:
10 to 11 g of the sample powder was put in a 10 ml glass graduated cylinder, and the powder packing density when tapped 200 times with a stroke of about 20 mm was obtained.

Contained carbon concentration C:
An EMIA-520 carbon sulfur analyzer manufactured by HORIBA, Ltd. was used. A sample of several tens to 100 mg was weighed into an air-baked magnetic crucible, a combustion aid was added, and C was combusted and extracted in a high-frequency heating furnace in an oxygen stream. CO ₂ in the combustion gas was quantified by non-dispersive infrared absorption spectrophotometry. For sensitivity calibration, 150-15 low alloy steel No. 1 (C guaranteed value: 0.469% by weight) manufactured by Japan Iron and Steel Federation was used.

Volume resistivity:
Using a powder resistivity measurement device (Dia Instruments: Lorester GP powder low efficiency measurement system PD-41), the sample weight is 3 g, and a powder probe unit (four probe / ring electrode, electrode spacing 5.0 mm) The electrode resistivity is 1.0 mm, the sample radius is 12.5 mm, and the applied voltage limiter is 90 V. The volume resistivity [Ω · cm] of the powder under various pressures is measured, and the volume resistivity under a pressure of 40 MPa is measured. The values were compared.

Median diameter of pulverized particles in slurry:
Using a known laser diffraction / scattering particle size distribution measuring device, the refractive index was set to 1.24, and the particle diameter standard was measured as the volume standard. As a dispersion medium, a 0.1 wt% sodium hexametaphosphate aqueous solution was used, and measurement was performed after ultrasonic dispersion for 5 minutes.

Median diameter as average particle diameter of raw material LiOH powder:
Using a known laser diffraction / scattering particle size distribution measuring apparatus, the refractive index was set to 1.14, and the particle diameter standard was measured as a volume standard. Ethyl alcohol was used as a dispersion medium, and after making a saturated solution of lithium hydroxide, measurement was performed after ultrasonic dispersion for 5 minutes.

Physical properties of particulate powder obtained by spray drying:
The form was confirmed by confirmation through SEM observation and cross-sectional SEM observation. The median diameter as the average particle diameter was measured with a known laser diffraction / scattering particle size distribution measuring apparatus with a refractive index of 1.24 and a particle diameter standard as a volume standard. As a dispersion medium, a 0.1 wt% sodium hexametaphosphate aqueous solution was used, and measurement was performed after ultrasonic dispersion for 5 minutes. The specific surface area was determined by the BET method.

[Production of Lithium Nickel Manganese Cobalt Composite Oxide Powder (Examples and Comparative Examples)]
Example 1
Ni (OH) ₂ , Mn ₃ O ₄ , and Co (OH) ₂ were weighed and mixed so as to have a molar ratio of Ni: Mn: Co = 0.347: 0.440: 0.167. Pure water was added to the slurry to prepare a slurry. While stirring the slurry, the solid content in the slurry was pulverized to a median diameter of 0.18 μm using a circulating medium agitation type wet pulverizer.

Particulate powder obtained by spray-drying this slurry with a spray dryer (powder formed by agglomerating primary particles to form solid secondary particles. Average particle size: 10.1 μm, BET specific surface area: 73 m ² / g) About 13 g of LiOH powder pulverized to a median diameter of 20 μm or less was added to about 40 g. About 53 g of this pre-mixed powder was placed in a 500 ml wide-mouthed plastic bottle, sealed, and shaken and mixed for 20 minutes at a stroke of about 20 cm and about 160 times per minute. This pre-firing mixture was charged into an alumina crucible and calcined at 985 ° C. for 12 hours under air flow (temperature raising / lowering rate 5 ° C./min.), Then crushed to obtain a lithium nickel manganese cobalt based composite oxide powder. Obtained. Moreover, x = 0.055, y = 0.159, z = 0.032 were obtained from the analysis of Li / Ni / Mn / Co ratio. The deviation from the above charging ratio is considered to be a problem of the purity of the raw material.

FIG. 1 shows an XRD (powder X-ray diffraction) pattern using CuKα rays of this lithium nickel manganese cobalt based composite oxide powder. As is clear from FIG. 1, no diffraction peak was observed at 2θ = 31 ± 1 °. Moreover, it confirmed that the crystal structure was comprised including the layered R (-3) m structure. The average primary particle diameter of this powder is 0.6 μm, the median diameter of the secondary particles is 10.3 μm, the 90% cumulative diameter (D ₉₀ ) is 16.6 μm, the bulk density is 1.9 g / cc, and the BET specific surface area. 1.16 m ² / g, carbon content C is 0.020 wt%, volume resistivity under pressure of 40 MPa is 1.0 × 10 ⁵ Ω · cm, a-axis lattice constant is 2.868 Å, c-axis lattice The constant was 14.260cm.

(Example 2)
About 13.6 g of LiOH powder pulverized to a median diameter of 20 μm or less was added to about 40 g of the same particulate powder obtained in Example 1 obtained by spray drying the slurry with a spray dryer. About 53.6 g of this pre-mixed powder was placed in a 500 ml wide-mouthed plastic bottle, sealed, and shaken and mixed for 20 minutes at a stroke of about 20 cm and about 160 strokes per minute. This pre-firing mixture was charged into an alumina crucible and calcined at 985 ° C. for 12 hours under air flow (temperature raising / lowering rate 5 ° C./min.), Then crushed to obtain a lithium nickel manganese cobalt based composite oxide powder. Obtained. Moreover, x = 0.055, y = 0.159, z = 0.076 was obtained from the analysis of Li / Ni / Mn / Co ratio.

FIG. 2 shows an XRD (powder X-ray diffraction) pattern using CuKα rays of this lithium nickel manganese cobalt based composite oxide powder. As is clear from FIG. 2, no diffraction peak was observed at 2θ = 31 ± 1 °. Moreover, it confirmed that the crystal structure was comprised including the layered R (-3) m structure. The average primary particle diameter of this powder is 0.6 μm, the median diameter of the secondary particles is 10.4 μm, the 90% cumulative diameter (D ₉₀ ) is 16.6 μm, the bulk density is 1.8 g / cc, and the BET specific surface area. Is 1.00 m ² / g, carbon content C is 0.020 wt%, volume resistivity under pressure of 40 MPa is 2.6 × 10 ⁴ Ω · cm, a-axis lattice constant is 2.866 Å, c-axis lattice The constant was 14.254cm.

(Example 3)
Ni (OH) ₂ , Mn ₃ O ₄ , and Co (OH) ₂ were weighed and mixed so that the molar ratio of Ni: Mn: Co = 0.278: 0.463: 0.167 was obtained, and then Pure water was added to the slurry to prepare a slurry. While stirring this slurry, the solid content in the slurry was pulverized to a median diameter of 0.16 μm using a circulating medium agitation type wet pulverizer.

Particulate powder obtained by spray-drying this slurry with a spray dryer (powder formed by agglomeration of primary particles to form solid secondary particles. Average particle size: 10.6 μm, BET specific surface area: 66 m ² / g) To about 40 g, about 15.2 g of LiOH powder ground to a median diameter of 20 μm or less was added. About 55.2 g of the powder before mixing was placed in a 500 ml wide-mouthed plastic bottle, sealed, and shaken and mixed for 20 minutes at a stroke of about 20 cm and about 160 strokes per minute. This pre-firing mixture was charged into an alumina crucible and calcined at 985 ° C. for 12 hours under air flow (temperature raising / lowering rate 5 ° C./min.), Then crushed to obtain a lithium nickel manganese cobalt based composite oxide powder. Obtained. Further, from the analysis of the Li / Ni / Mn / Co ratio, x = 0.113, y = 0.159, and z = 0.071 were obtained.

FIG. 3 shows an XRD (powder X-ray diffraction) pattern using CuKα rays of this lithium nickel manganese cobalt based composite oxide powder. As apparent from FIG. 3, no diffraction peak was observed at 2θ = 31 ± 1 °. Moreover, it confirmed that the crystal structure was comprised including the layered R (-3) m structure. The average primary particle diameter of this powder is 0.7 μm, the median diameter of the secondary particles is 11.4 μm, the 90% cumulative diameter (D ₉₀ ) is 18.7 μm, the bulk density is 2.0 g / cc, the BET specific surface area. 0.94 m ² / g, carbon content C is 0.028 wt%, volume resistivity under pressure of 40 MPa is 3.6 × 10 ⁴ Ω · cm, a-axis lattice constant is 2.858 Å, c-axis lattice The constant was 14.239cm.

Example 4
About 14.6 g of LiOH powder pulverized to a median diameter of 20 μm or less was added to about 40 g of the same particulate powder obtained in Example 3 obtained by spray drying the slurry with a spray dryer. About 54.6 g of the powder before mixing was placed in a 500 ml wide-mouthed plastic bottle, sealed, and shaken and mixed for 20 minutes at a stroke of about 20 cm and about 160 times per minute. This pre-firing mixture was charged into an alumina crucible and calcined at 985 ° C. for 12 hours under air flow (temperature raising / lowering rate 5 ° C./min.), Then crushed to obtain a lithium nickel manganese cobalt based composite oxide powder. Obtained. Moreover, x = 0.113, y = 0.159, z = 0.033 were obtained from the analysis of Li / Ni / Mn / Co ratio.

FIG. 4 shows an XRD (powder X-ray diffraction) pattern using CuKα rays of this lithium nickel manganese cobalt based composite oxide powder. As apparent from FIG. 4, no diffraction peak was observed at 2θ = 31 ± 1 °. Moreover, it confirmed that the crystal structure was comprised including the layered R (-3) m structure. The average primary particle diameter is 0.6 μm, the median diameter of the secondary particles is 11.4 μm, the 90% cumulative diameter (D ₉₀ ) is 19.0 μm, the bulk density is 2.0 g / cc, and the BET specific surface area is 1. 13 m ² / g, carbon content C is 0.020% by weight, volume resistivity under pressure of 40 MPa is 2.0 × 10 ⁵ Ω · cm, a-axis lattice constant is 2.861 Å, c-axis lattice constant is 14 .250cm.

(Comparative Example 1)
About 12.5 g of LiOH powder pulverized to a median diameter of 20 μm or less was added to about 40 g of the same particulate powder obtained in Example 1 obtained by spray drying the slurry with a spray dryer. About 52.5 g of the powder before mixing was placed in a 500 ml wide-mouthed plastic bottle, sealed, and shaken and mixed for 20 minutes at a stroke of about 20 cm and about 160 times per minute. This pre-firing mixture was charged into an alumina crucible and calcined at 985 ° C. for 12 hours under air flow (temperature raising / lowering rate 5 ° C./min.), Then crushed to obtain a lithium nickel manganese cobalt based composite oxide powder. Obtained. Moreover, x = 0.055, y = 0.159, and z = -0.013 were obtained from the analysis of Li / Ni / Mn / Co ratio.

FIG. 5 shows an XRD (powder X-ray diffraction) pattern using CuKα rays of this lithium nickel manganese cobalt based composite oxide powder. As is clear from FIG. 5, no diffraction peak was observed at 2θ = 31 ± 1 °. Moreover, it confirmed that the crystal structure was comprised including the layered R (-3) m structure. The average primary particle diameter is 0.6 μm, the median diameter A of the secondary particles is 10.3 μm, the 90% cumulative diameter (D ₉₀ ) is 15.8 μm, the bulk density is 2.0 g / cc, and the BET specific surface area is 1. .17 m ² / g, carbon content C is 0.009 wt%, volume resistivity under pressure of 40 MPa is 1.3 × 10 ⁷ Ω · cm, a-axis lattice constant is 2.872 Å, c-axis lattice constant is It was 14.269 kg.

(Comparative Example 2)
About 15.8 g of LiOH powder pulverized to a median diameter of 20 μm or less was added to about 40 g of the same particulate powder obtained in Example 3 obtained by spray drying the slurry with a spray dryer. About 55.8 g of the powder before mixing was placed in a 500 ml wide-mouthed plastic bottle, sealed, and shaken and mixed for 20 minutes at a stroke of about 20 cm and about 160 times per minute. This pre-firing mixture was charged into an alumina crucible and calcined at 985 ° C. for 12 hours under air flow (temperature raising / lowering rate 5 ° C./min.), Then crushed to obtain a lithium nickel manganese cobalt based composite oxide powder. Obtained. Further, from the analysis of the Li / Ni / Mn / Co ratio, x = 0.113, y = 0.159, and z = 0.106 were obtained.

FIG. 6 shows an XRD (powder X-ray diffraction) pattern using CuKα rays of this lithium nickel manganese cobalt based composite oxide powder. As apparent from FIG. 6, no diffraction peak was observed at 2θ = 31 ± 1 °. Moreover, it confirmed that the crystal structure was comprised including the layered R (-3) m structure. The average primary particle diameter of this powder is 0.7 μm, the median diameter of the secondary particles is 11.2 μm, the 90% cumulative diameter (D ₉₀ ) is 18.1 μm, the bulk density is 2.1 g / cc, and the BET specific surface area. 0.36 m ² / g, carbon content C is 0.016 wt%, volume resistivity under pressure of 40 MPa is 2.0 × 10 ⁴ Ω · cm, a-axis lattice constant is 2.855 Å, c-axis lattice The constant was 14.234cm.

(Comparative Example 3)
LiOH.H ₂ O, NiO, Mn ₃ O ₄ , and CoOOH are weighed and mixed so as to have a molar ratio of Li: Ni: Mn: Co = 0.05: 0.25: 0.50: 0.25. After that, pure water was added thereto to prepare a slurry. While stirring the slurry, the solid content in the slurry was pulverized to a median diameter of 0.19 μm using a circulating medium agitation type wet pulverizer.

Particulate powder obtained by spray-drying this slurry with a spray dryer (powder formed by agglomeration of primary particles to form solid secondary particles. Average particle size: 6.0 μm, BET specific surface area: 57 the .6m ² / g) to about 40 g, a LiOH powder pulverized below median diameter 20μm and about 14.4g added. About 54.4 g of this pre-mixed powder was placed in a 500 ml wide-mouthed plastic bottle, sealed, and shaken and mixed for 20 minutes at a stroke of about 20 cm and about 160 strokes per minute. This pre-firing mixture was placed in an alumina crucible and calcined at 900 ° C. for 12 hours under air flow (temperature raising / lowering rate 5 ° C./min.), Then pulverized to obtain a lithium nickel manganese cobalt based composite oxide powder. Obtained. Moreover, x = 0.141, y = 0.222, z = 0.005 was obtained from the analysis of Li / Ni / Mn / Co ratio.

FIG. 7 shows an XRD (powder X-ray diffraction) pattern using CuKα rays of this lithium nickel manganese cobalt based composite oxide powder. As apparent from FIG. 7, no diffraction peak was observed at 2θ = 31 ± 1 °. Moreover, it confirmed that the crystal structure was comprised including the layered R (-3) m structure. The average primary particle diameter is 0.3 μm, the median diameter of the secondary particles is 6.2 μm, the 90% cumulative diameter (D ₉₀ ) is 9.6 μm, the bulk density is 2.1 g / cc, and the BET specific surface area is 0.00. 98 m ² / g, carbon content C is 0.009 wt%, volume resistivity under pressure of 40 MPa is 3.4 × 10 ⁶ Ω · cm, a-axis lattice constant is 2.857 Å, c-axis lattice constant is 14 .248cm.

(Comparative Example 4)
About 13.3 g of LiOH powder pulverized to a median diameter of 20 μm or less was added to about 40 g of the same particulate powder as in Comparative Example 3 obtained by spray drying the slurry with a spray dryer. About 53.3 g of this pre-mixed powder was placed in a 500 ml wide-mouthed plastic bottle, sealed, and shaken and mixed for 20 minutes at a stroke of about 20 cm and about 160 times per minute. This pre-firing mixture was placed in an alumina crucible and calcined at 900 ° C. for 12 hours under air flow (temperature raising / lowering rate 5 ° C./min.), Then pulverized to obtain a lithium nickel manganese cobalt based composite oxide powder. Obtained. Further, from the analysis of the Li / Ni / Mn / Co ratio, x = 0.141, y = 0.222, and z = −0.086 were obtained.

FIG. 8 shows an XRD (powder X-ray diffraction) pattern using CuKα rays of this lithium nickel manganese cobalt based composite oxide powder. As is clear from FIG. 8, a diffraction peak was observed at 2θ = 31 ± 1 °. Moreover, it confirmed that the crystal structure was comprised including the layered R (-3) m structure. The average primary particle diameter of this powder is 0.5 μm, the median diameter of the secondary particles is 6.4 μm, the 90% cumulative diameter (D ₉₀ ) is 9.8 μm, the bulk density is 2.0 g / cc, and the BET specific surface area. Was 0.70 m ² / g, the carbon concentration C was 0.003% by weight, the a-axis lattice constant was 2.857 Å, and the c-axis lattice constant was 14.254 Å. The volume resistivity under pressure of 40 MPa was not measurable because the resistance value exceeded the measurement range.

(Comparative Example 5)
Ni (OH) ₂ , Mn ₃ O ₄ , and Co (OH) ₂ were weighed and mixed so that the molar ratio of Ni: Mn: Co = 0.417: 0.417: 0.167 was obtained, and then Pure water was added to the slurry to prepare a slurry. While stirring this slurry, the solid content in the slurry was pulverized to a median diameter of 0.17 μm using a circulating medium agitation type wet pulverizer.

Particulate powder obtained by spray-drying this slurry with a spray dryer (powder formed by agglomeration of primary particles to form solid secondary particles. Average particle size: 10.2 μm, BET specific surface area: 77 m ² / g) About 12 g of LiOH powder ground to a median diameter of 20 μm or less was added to about 40 g. About 52 g of this pre-mixed powder was placed in a 500 ml wide-mouthed plastic bottle, sealed, and shaken and mixed for 20 minutes at a stroke of about 20 cm and about 160 times per minute. This pre-firing mixture was charged into an alumina crucible and calcined at 985 ° C. for 12 hours under air flow (temperature raising / lowering rate 5 ° C./min.), Then crushed to obtain a lithium nickel manganese cobalt based composite oxide powder. Obtained. Moreover, x = 0, y = 0.161, z = 0.056 were obtained from the analysis of Li / Ni / Mn / Co ratio.

FIG. 9 shows an XRD (powder X-ray diffraction) pattern using CuKα rays of this lithium nickel manganese cobalt based composite oxide powder. As is clear from FIG. 9, no diffraction peak was observed at 2θ = 31 ± 1 °. Moreover, it confirmed that the crystal structure was comprised including the layered R (-3) m structure. The average primary particle diameter of this powder is 0.7 μm, the median diameter of secondary particles is 10.8 μm, 90% cumulative diameter (D ₉₀ ) is 17.6 μm, bulk density is 2.1 g / cc, BET specific surface area. 1.03 m ² / g, carbon content C is 0.019% by weight, volume resistivity under pressure of 40 MPa is 3.0 × 10 ⁴ Ω · cm, a-axis lattice constant is 2.873Å, c-axis lattice The constant was 14.265Å.

  The physical properties of the lithium nickel manganese cobalt composite oxide powders obtained in Examples 1 to 4 and Comparative Examples 1 to 5 are collectively shown in Tables 1-A and B.

[Production and evaluation of battery]
Using the lithium nickel manganese cobalt composite oxide powders produced in Examples 1 to 4 and Comparative Examples 1 to 5 as positive electrode materials (positive electrode active materials), lithium secondary batteries were produced by the following method. .

  75% by weight of each of the lithium nickel manganese cobalt composite oxide powders produced in Examples 1 to 4 and Comparative Examples 1 to 5, 20% by weight of acetylene black, and 5% by weight of polytetrafluoroethylene powder were weighed. The material was mixed thoroughly in a mortar, and a thin sheet was punched out using a 9 mmφ punch. At this time, the total weight was adjusted to about 8 mg. This was pressure-bonded to an aluminum expanded metal to obtain a 9 mmφ positive electrode.

This 9 mmφ positive electrode is used as a test electrode, a lithium metal plate is used as a counter electrode, and LiPF ₆ is added to a solvent of EC (ethylene carbonate): DMC (dimethyl carbonate): EMC (ethyl methyl carbonate) = 3: 3: 4 (volume ratio). Using an electrolytic solution dissolved at 1 mol / L, a coin-type cell was assembled for a rate test and a high-voltage cycle test using a porous polyethylene film having a thickness of 25 μm as a separator.

The produced coin cell was evaluated as follows.
(1) Rate test:
Each coin cell was tested at a constant current of 0.2 mA / cm ² with a charge upper limit voltage of 4.5 V and a discharge lower limit voltage of 3.0 V, followed by 2 cycles of charge and discharge, followed by 3 to 10 cycles. Eye, 0.5 mA / cm ² constant current charging, sequentially 0.2 mA / cm ² , 0.5 mA / cm ² , 1 mA / cm ² , 3 mA / cm ² , 5 mA / cm ² , 7 mA / cm ² , 9 mA / Cm ² and 11 mA / cm ² were tested for each discharge. The low-rate discharge capacity L at 0.2 mA / cm ² in the third cycle at this time (mAh / g) and at 11 mA / cm ² for 10 cycle high-rate discharge capacity H (mAh / g), the low rate discharge capacity The results of percentage (%) of the high-rate discharge capacity H with respect to L are shown in Table 2-A.

  As the acceptance criteria, the high rate discharge capacity at the 10th cycle was set to 125 mAh / g or more, and the percentage (%) of the high rate discharge capacity to the low rate discharge capacity was set to 75% or more.

(2) High voltage cycle test:
Each coin cell was tested at a constant current of 0.2 mA / cm ² with a charge upper limit voltage of 4.6 V and a discharge lower limit voltage of 3.0 V, followed by a charge / discharge 2 cycle test, followed by 3 to 52 cycles. In the eye, a cycle test was conducted by constant current charging / discharging of 0.5 mA / cm ² . At this time, the initial charge / discharge capacity (mAh / g) at 0.2 mA / cm ² in the first cycle and the discharge capacity (0.5 rd discharge capacity, 52th in 0.5 mA / cm ² in the third and 52nd cycles). Discharge capacity) (mAh / g) and its ratio (cycle retention rate = 52th discharge capacity / 3rd discharge capacity × 100) were determined, and the results are shown in Table 2-B. In addition, as an acceptance criterion, the initial charge / discharge capacity (current density: 0.2 mA / cm ² ) of the first cycle is 185 mAh / g or more, and the discharge capacity (current density: 0.5 mA / cm ² ) of the third cycle. A cycle maintenance ratio of 86% or more, which is a percentage of the discharge capacity (current density: 0.5 mA / cm ² ) of the 52nd cycle / 3rd cycle, was set to 175 mAh / g or more.

  From Table 2, the following is clear.

In Comparative Examples 1 and 3, since the z value of the lithium nickel manganese cobalt composite oxide powder composition is too small, the conductivity is low and the high-rate discharge capacity of the battery is low.
In Comparative Example 2, since the z value is too large, the discharge capacity of the battery is low for both the low rate and the high rate.
In Comparative Example 4, since the z value is too small, in addition to low conductivity, a diffraction peak derived from the spinel phase is detected, and the high rate discharge capacity and cycle capacity maintenance rate of the battery are low.
In Comparative Example 5, since the x value is too small, durability at a high voltage is low, and the cycle capacity maintenance rate is low.

  On the other hand, by using the lithium nickel manganese cobalt composite oxide powder of the present invention satisfying specific x value, y value and z value as the positive electrode material, cycle deterioration at the time of high voltage use can be suppressed, and the capacity can be reduced. It can be seen that a lithium secondary battery having high load characteristics and good performance balance is provided.

  The use of the lithium secondary battery of the present invention is not particularly limited, and can be used for various known uses. Specific examples include notebook computers, pen input computers, mobile computers, electronic book players, mobile phones, mobile faxes, mobile copy, mobile printers, headphone stereos, video movies, LCD TVs, handy cleaners, portable CDs, minidiscs, and transceivers. Electronic notebooks, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, lighting equipment, toys, game machines, watches, strobes, cameras, power tools, automotive power sources, and the like.

4 is a graph showing an XRD pattern of a lithium nickel manganese cobalt based composite oxide produced in Example 1. FIG. 4 is a graph showing an XRD pattern of a lithium nickel manganese cobalt composite oxide produced in Example 2. FIG. 6 is a graph showing an XRD pattern of a lithium nickel manganese cobalt based composite oxide produced in Example 3. FIG. 6 is a graph showing an XRD pattern of a lithium nickel manganese cobalt-based composite oxide produced in Example 4. 6 is a graph showing an XRD pattern of a lithium nickel manganese cobalt composite oxide produced in Comparative Example 1. FIG. 6 is a graph showing an XRD pattern of a lithium nickel manganese cobalt composite oxide produced in Comparative Example 2. FIG. 10 is a graph showing an XRD pattern of a lithium nickel manganese cobalt-based composite oxide produced in Comparative Example 3. 10 is a graph showing an XRD pattern of a lithium nickel manganese cobalt-based composite oxide produced in Comparative Example 4. 10 is a graph showing an XRD pattern of a lithium nickel manganese cobalt-based composite oxide produced in Comparative Example 5.

Claims (12)

A lithium nickel manganese cobalt based composite oxide powder for a lithium secondary battery positive electrode material, comprising a crystal structure belonging to a layered structure and having a composition represented by the following formula (I):
Li [Li _{z / (2 + z)} {(Li _x Ni _{(1-3x) / 2} Mn _{(1 + x) / 2} ) _(1-y) Co _y } _{2 / (2 + z)} ] O ₂ ... (I)
(However, 0.01 ≦ x ≦ 0.15
0 ≦ y ≦ 0.35
0.02 (1-y) (1-3x) ≦ z ≦ 0.15 (1-y) (1-3x))   In the formula (I), 0.05 ≦ x ≦ 0.12, 0.10 ≦ y ≦ 0.20, 0.04 (1-y) (1-3x) ≦ z ≦ 0.13 (1-y) It is (1-3x), The lithium nickel manganese cobalt type complex oxide powder for lithium secondary battery positive electrode materials of Claim 1 characterized by the above-mentioned.   3. The lithium nickel manganese cobalt system for a lithium secondary battery positive electrode material according to claim 1, wherein the powder X-ray diffraction pattern using CuKα rays has no diffraction peak at 2θ = 31 ± 1 °. Composite oxide powder. Crystal structure is layered

4. The structure according to claim 1, wherein the lattice constant is in the range of 2.855 Å ≦ a ≦ 2.870 Å and 14.235 Å ≦ c ≦ 14.265 Å. 2. Lithium nickel manganese cobalt based composite oxide powder for lithium secondary battery positive electrode material according to item 1.   5. The lithium for a positive electrode material for a lithium secondary battery according to claim 1, wherein the C value is 0.030 wt% or less when the carbon content is C (wt%). Nickel manganese cobalt complex oxide powder. 6. The lithium nickel manganese for a lithium secondary battery positive electrode material according to claim 1, wherein the volume resistivity when consolidated at a pressure of 40 MPa is 5 × 10 ⁵ Ω · cm or less. Cobalt complex oxide powder.   8. The bulk density is 1.5 g / cc or more, the average primary particle diameter is 0.1 to 3 μm, and the median diameter of the secondary particles is 3 to 20 μm. Lithium nickel manganese cobalt based composite oxide powder for positive electrode materials of lithium secondary batteries. The lithium nickel manganese cobalt based composite oxide powder for a lithium secondary battery positive electrode material according to any one of claims 1 to 7, wherein the BET specific surface area is 0.2 to 3.0 m ² / g. body.   A powder obtained by pulverizing a nickel compound, a manganese compound, and a cobalt compound and spray-drying and / or thermally decomposing a slurry in which these are uniformly dispersed to form secondary particles by agglomerating primary particles. 9. The lithium secondary battery positive electrode material according to claim 1, wherein the powder is mixed with a lithium compound, and the obtained mixture is fired in an oxygen-containing gas atmosphere. Method for producing lithium nickel manganese cobalt based composite oxide powder.   A positive electrode active material layer containing the lithium nickel manganese cobalt based composite oxide powder for a lithium secondary battery positive electrode material according to claim 1 and a binder on a current collector. A positive electrode for a lithium secondary battery.   A lithium secondary battery comprising a negative electrode capable of inserting and extracting lithium, a non-aqueous electrolyte containing a lithium salt, and a positive electrode capable of inserting and extracting lithium, wherein the lithium secondary battery according to claim 10 is used as the positive electrode. A lithium secondary battery using a positive electrode for a battery. The lithium secondary battery according to claim 11, wherein the lithium secondary battery is designed so that a charging potential of the positive electrode in a fully charged state is 4.4 V (vs. Li ^/ Li ⁺ ) or more.

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