JP6927367B2 - Positive electrode active material for lithium secondary battery, its manufacturing method, electrode for lithium secondary battery and lithium secondary battery - Google Patents

Description

The present invention relates to a positive electrode active material for a lithium secondary battery, a method for producing the positive electrode active material, an electrode for a lithium secondary battery containing the positive electrode active material, and a lithium secondary battery provided with the electrode.

Conventionally, as a positive electrode active material for a lithium secondary battery, a "LiMeO _{type 2 " active material having an α-NaFeO type 2} crystal structure (Me is a transition metal) has been studied, and _{a lithium secondary battery using LiCoO 2} is widely put into practical use. It had been transformed. However, _{the discharge capacity of LiCoO 2} was about 120 to 130 mAh / g. It has been desired to use abundant Mn as an earth resource as the Me. However, when the molar ratio of Mn to Me to Mn / Me exceeds 0.5, _{the "LiMeO type 2} " active material containing Mn as Me undergoes a structural change to a spinel type when charged, resulting in crystallization. Since the structure cannot be maintained, there is a problem that the charge / discharge cycle performance is significantly inferior.

_{Therefore, various "LiMeO type 2} " active materials having a molar ratio of Mn to Me of Mn / Me of 0.5 or less and excellent in charge / discharge cycle performance have been proposed and partially put into practical use. _{For example, a cathode active material containing LiNi 1/2} Mn _1/2 O ₂ and LiNi _1/3 Co _1/3 Mn _1/3 O ₂ which are lithium transition metal composite oxides has a discharge capacity of 150 to 180 mAh / g. Has.

_{In the "LiMeO type 2} " positive electrode active material having the above-mentioned layered structure, in order to obtain a high charge / discharge capacity, the element distribution (particularly Mn) in one particle is made uniform at the atomic level by using a coprecipitation method or the like. It is known that it is important to make it an active material. (See, for example, Patent Document 1)

On the other hand, with respect to the so-called "LiMeO _{type 2} " active material as described above, the composition ratio Li / Me of lithium (Li) to the ratio of the transition metal (Me) is larger than 1, for example, Li / Me is 1.25 to 1. A so-called "lithium-rich" active material of .6 is also known.

Further, with respect to the positive electrode active material for a lithium secondary battery containing a lithium transition metal composite oxide, an invention is known in which the half-value width of the diffraction peaks of the (003) plane and the (104) plane by X-ray diffraction measurement is defined. For example, see Patent Documents 2 to 6).

Patent Document 2 states that "the diffraction peak angles 2θ of the (003) plane and the (104) plane in the mirror index hkl of powder X-ray diffraction using CuKα rays are 18.65 ° or more and 44.50 ° or more, respectively. The diffraction peak half-value width of each of these surfaces is 0.18 ° or less, and the diffraction peak angles 2θ of the (108) and (110) surfaces are 64.40 ° and 65.15 ° or more, respectively, and each of them. _{Li 1.1} Ni _0.333 Mn _0.333 Co _0.333 where the half-value width of the diffraction peak of the surface is 0.18 ° or less.
O ₂ layered lithium-nickel-manganese-cobalt composite oxide. (Claim 1, paragraphs [0020] to [0032]).
Then, as an object of the present invention, "to provide a material for a cathode active material capable of imparting high discharge capacity, high current load characteristics, and high reliability (long life) to a lithium ion secondary battery" (paragraph [paragraph [ 0010]) is described.

Patent Document 3 states that "a current collector and an active material layer containing active material particles held in the current collector are provided, and the active material particles are Li _1.15 Ni _0.33 Co _0.33 Mn _0.33 W _0.005 O _2. Secondary particles in which a plurality of primary particles of lithium transition metal oxide, which is a compound having a layered crystal structure represented by, are aggregated, and a hollow portion formed inside the secondary particles and a shell portion surrounding the hollow portion. The secondary particles are formed with through holes penetrating from the outside to the hollow portion, and here, in the powder X-ray diffraction pattern of the active material particles, (003). The ratio (A / B) of the half-value width A of the diffraction peak obtained by the plane) to the half-value width B of the diffraction peak obtained by the (104) plane satisfies the following equation: (A / B) ≤0.7. Lithium secondary batteries. ”(Claims 1 and 6, paragraphs [0073] to [0078], [089] Table 1) are described.
Then, as a subject of the present invention, a required output can be exhibited even in a low SOC region, the running performance of a hybrid vehicle, an electric vehicle, etc. can be improved, and the number of batteries for securing a required amount of energy is required. It has been shown to provide a lithium secondary battery that can reduce the amount of electricity (paragraph [0004]).

Patent Document 4, has a "layered _{structure, Li y Ni a Co b Mn} c M d O x [ element M Al, Si, Zr, Ti, Fe, Mg, Nb, from the group consisting of Ba and V At least one element selected, 1.9 ≦ (a + b + c + d + y) ≦ 2.1, 1.0 <y ≦ 1.3, 0 <a ≦ 0.3, 0 <b ≦ 0.25, 0. 3 ≦ c ≦ 0.7, 0 ≦ d ≦ 0.1, 1.9 ≦ x ≦ 2.1], and half of the (003) plane in the powder X-ray diffraction diagram. An active material in which the ratio of the price range FWHM ₀₀₃ to the half price width FWHM _{104 of the (104) plane is represented by FWHM 003} / FWHM ₁₀₄ ≤ 0.57, and the average primary particle size is 0.2 μm to 0.5 μm. ” The invention of (claim 1) is described.
Then, as an object of the present invention, "providing an active material and a lithium ion secondary battery having a high discharge capacity and excellent charge / discharge cycle characteristics" (paragraph [0006]) is shown.

In Patent Document 5, "composition formula Li _{1 + α} Me _1-α O ₂ (Me is a transition metal element containing Co, Ni and Mn, 1.2 <(1 + α) / (1-α) <1.6). It is a positive electrode active material for a lithium secondary battery containing the represented lithium transition metal composite oxide, and the lithium transition metal composite oxide has a molar ratio Co / Me of Co in the Me of 0.24 to 0. It is .36, and the half-value width of the diffraction peak assigned to the (003) plane when the space group R3-m is used in the crystal structure model based on the X-ray diffraction pattern is in the range of 0.204 ° to 0.303 °. Or, a positive electrode active material for a lithium secondary battery, wherein the half-value width of the diffraction peak attributed to the (104) plane is in the range of 0.278 ° to 0.424 °. ” Is described.
Then, as an object of the present invention, "to provide a positive electrode active material for a lithium secondary battery having excellent high rate discharge performance, a method for producing the positive electrode active material, and a lithium secondary battery using the positive electrode active material". (Paragraph [0009]) is described.

Patent Document 6 states that "at least one secondary particle containing an agglomerate of two or more primary particles is contained, and the secondary particle is Li _1.05 Ni _0.5 Co _0.2 Mn _0.3 O. _The primary particles contain 2 nickel-based lithium transition metal oxides and have an average particle size of 3 to 5 μm. The secondary particles include small-diameter secondary particles having an average particle size of 5 to 8 μm and an average particle size of 10. It contains one or more selected large-diameter secondary particles of to 20 μm, and in X-ray diffraction analysis spectrum analysis, the half-value width of the (003) peak is 0.120 to 0.125 °, and the (104) peak. A positive particle active material having a half-price range of 0.105 to 0.110 °. ”(Claims 1 and 2, paragraphs [0050], [0119] to [0126], [0131] to [0133], [0151] ~ [0154], [FIG. 3A] to [FIG. 3C]) are described.
Then, as an effect of the present invention, "providing a positive electrode active material with improved high voltage characteristics, and by adopting such a positive electrode active material, positive electrode slurry stability and electrode plate mixture density in the electrode plate manufacturing process" It is possible to manufacture a positive electrode plate for a lithium secondary battery in which the above is improved ”(paragraph [0016]).

WO2002 / 086993 Japanese Unexamined Patent Publication No. 2005-53764 Japanese Unexamined Patent Publication No. 2013-51172 Japanese Unexamined Patent Publication No. 2013-206552 Japanese Unexamined Patent Publication No. 2014-44928 Japanese Unexamined Patent Publication No. 2015-18803

The above-mentioned so-called "LiMeO _{type 2} " active material has a low discharge capacity (Patent Documents 1 to 3 and 6), and the discharge capacity of the so-called "lithium excess type" active material is generally so-called "LiMeO _{type 2} " active material. Although it is larger than a substance (Patent Documents 4 and 5), there is a problem that the high rate discharge performance at the end of discharge is inferior. The present invention has been studied to further improve the performance of the above-mentioned so-called "LiMeO _{type 2" active material.}
In the study of the conventional "LiMeO _{type 2} " positive electrode active material, the present inventor applied a co-precipitation method that intentionally disturbs the uniformity of Mn at the atomic level, thereby increasing the crystallinity of the positive electrode active material due to charging and discharging. It has been found that the anisotropy can be adjusted and a high discharge capacity can be obtained, and a prior invention has been filed (Japanese Patent Application No. 2014-196484).
However, further improvement in charge / discharge cycle performance has been required.
The present invention relates to a positive electrode active material for a lithium secondary battery having a large discharge capacity and excellent charge / discharge cycle performance, a method for producing the positive electrode active material, an electrode for a lithium secondary battery containing the positive electrode active material, and an electrode thereof. It is an object to provide a lithium secondary battery equipped with the above.

In the present invention, the following means are adopted in order to solve the above problems.
(1) A positive electrode active material for a lithium secondary battery in which the transition metal (Me) contains Ni, Co and Mn and contains a lithium transition metal composite oxide having a hexagonal structure.
The lithium transition metal composite oxide is divided into 10 equal parts with the center of the particle cross section as Point 0 and the outermost surface of the particle as Point 10, and Point 0 to Point 9 are the cores and Point 9 from the center of the particle cross section toward the outermost surface. When the molar concentrations of Ni, Co, and Mn are averaged with Point 10 as the surface layer,
The molar ratio of Ni in the transition metal (Me) in the surface layer, Ni / Me, is smaller than the molar ratio of Ni in the transition metal (Me) in the core, Ni / Me .
The molar ratio of Ni in the transition metal (Me) in the core, Ni / Me, is 0.4 ≦ Ni / Me ≦ 0.8.
The molar ratio Ni / Me of Ni in the transition metal (Me) on the outermost surface of the surface layer is 0.1 ≦ Ni / Me ≦ 0.4.
The molar ratio of Mn in the transition metal (Me) in the surface layer, Mn / Me, is larger than the molar ratio of Mn in the transition metal (Me) in the core, Mn / Me .
Potential 4.45V (vs.Li/Li ⁺⁾ half-width ratio F in (003) / F (104) a potential 2.0V half-width ratio F in ^{(vs.Li/Li +) (003) /} F (104 A positive electrode active material for a lithium secondary battery, wherein the value divided by) is between 0.9 and 1.1.
(2) pre-SL is 0.1 ≦ Mn / Me ≦ 0.4 is Mn / Me in the core, it Mn / Me is 0.4 ≦ Mn / Me ≦ 0.8 on the outermost surface of the surface layer The positive electrode active material for a lithium secondary battery according to (1) above.
(3) The method for producing a positive electrode active material for a lithium secondary battery according to (1) or (2 ) above, wherein a compound containing Ni, Co and Mn is co-precipitated in a solution to co-precipitate a transition metal composite oxide. of the step of preparing a precursor, N i, Co and with a solution containing a compound of the solution and Mn containing compound separately added dropwise simultaneously Mn, the molar ratio Ni of Ni in said transition metal (Me) After preparing a core precursor of a transition metal composite oxide with / Me of 0.4 ≤ Ni / Me ≤ 0.8,
A solution containing a compound of Ni, Co and Mn is dropped, and the molar ratio Ni / Me of Ni in the transition metal (Me) is smaller than the molar ratio Ni / Me of Ni in the core, and the transition metal on the outermost surface. molar ratio Ni / Me of Ni in (Me) is Ri 0.1 ≦ Ni / Me ≦ 0.4 der, the molar ratio Mn / Me of Mn in the transition metal (Me) in the precursor of said surface layer is The positive activity for a lithium secondary battery, which comprises producing a precursor of a surface layer of a transition metal composite oxide having a molar ratio of Mn in the transition metal (Me) in the precursor of the core larger than Mn / Me. Method of manufacturing a substance.
(4) before SL Mn / Me in the precursor of the core is that 0.1 ≦ Mn / Me ≦ 0.4, Mn / Me of the outermost surface 0.4 ≦ Mn / Me ≦ in the precursor of said surface layer The method for producing a positive electrode active material for a lithium secondary battery according to (3) above, which is 0.8.
(5) An electrode for a lithium secondary battery containing the positive electrode active material for the lithium secondary battery according to (1) or (2) above.
(6) A lithium secondary battery provided with the electrode for the lithium secondary battery according to (5) above.

According to the present invention, a positive electrode active material for a lithium secondary battery having a large discharge capacity and excellent charge / discharge cycle performance, a method for producing the positive electrode active material, an electrode for a lithium secondary battery containing the positive electrode active material, and an electrode for a lithium secondary battery. A lithium secondary battery provided with the electrode can be provided.

External perspective view showing one embodiment of the lithium secondary battery according to the present invention. Schematic diagram showing a power storage device in which a plurality of lithium secondary batteries according to the present invention are assembled. The figure which shows the measuring method of the Ni concentration of the core and the surface layer about the positive electrode active material for a lithium secondary battery which concerns on this invention.

The configuration and the action and effect of the present invention will be described with technical ideas. However, the mechanism of action includes estimation, and its correctness does not limit the present invention. It should be noted that the present invention can be practiced in various other forms without departing from its spirit or major features. Therefore, the embodiments or experimental examples described below are merely examples in all respects and should not be construed in a limited manner. Furthermore, all modifications and modifications that fall within the equivalent scope of the claims are within the scope of the present invention.

The lithium transition metal composite oxide contained in the positive electrode active material according to the present invention is a particle having a core and a surface layer.
In the present invention, the transition metal element Me containing Co, Ni and Mn does not have a constant Co / Ni / Mn composition ratio in one particle of the lithium transition metal composite oxide (active material), and the lithium transition. metal composite oxide particles have a core and a surface layer, Ni concentration in one particle, the core is high (molar ratio Ni / Me = 0.4~0.8), the surface layer is rather low, the top-surface it is characterized by a molar ratio Ni / Me = 0.1~0.4.
By measuring the cross section of the particle using an SEM-EDX device as described later, the measurement points are divided into 10 equal parts with the center of the particle as Point 0 and the surface of the particle as Point 10, and from Point 0 to Point 10. At each measurement point of, the ratio of the molar concentration of Co, Ni and Mn to the total molar concentration of Co, Ni and Mn is calculated. Then, with Point 0 to Point 9 as the core and Point 9 to Point 10 as the surface layer, the molar concentrations are averaged to obtain the Ni molar concentration of the core and the surface layer.
In the above example, the region where the average composition satisfies the Ni concentration of the core is calculated in the range of up to 90%, but in the present invention, the molar ratio Ni of the outermost surface in the core and the surface layer is calculated. If / Me is in the above range, the composition ratio of Co / Ni / Mn is gradually changed from the center toward the surface. Therefore , since the molar concentration of the core determines the characteristics of the active material, it is preferable to calculate the molar concentration in the range of 80 to 97% with 90% as a reference.
Further, the substance of the "surface layer" of the particles referred to here is a lithium transition metal composite oxide containing Ni, Co and Mn, but to the extent that the effects of the present invention are not impaired, further on the surface of the particles. It does not exclude coating with other substances such as carbon coating, alumina coating, and dissimilar element coating.

The lithium transition metal composite oxide constituting the core _{has the same composition formula Li 1 + x} Me _1-x O ₂ (Me: Ni, Co and Mn _{) as the conventional “LiMeO type 2} ” active material (NCM type active material). Is represented by a transition metal containing).
In the present invention, the state of the core (bulk) is changed to a specific ratio to the core and the surface layer while applying a structure that intentionally disturbs the uniformity of Mn at the atomic level like the active material of the above-mentioned prior invention. By applying the Co / Ni / Mn composition, it was possible to improve the life characteristics while maintaining the capacity characteristics.

Lithium transition metal composite oxide constituting the core is represented by the composition formula _Li 1 ₊ x as an example _{(Ni a Co b Mn c)} 1-x O 2 (a + b + c = 1). x is preferably −0.1 <x <0.1. x is determined according to the charge-end / discharge-end ratio of F (003) / F (104) described later, and this ratio is in the range of 0.9 to 1.1 and -0.1 <x <0.1. It becomes. It is preferably −0.05 ≦ x ≦ 0.09.

In the present invention, in order to improve the discharge capacity and charge / discharge cycle performance of the lithium secondary battery, the value of a, that is, the molar ratio of Ni to the transition metal element Me, Ni / Me, is 0.4 to 0.8. do. It is preferably 0.5 to 0.8.

Further, the value of b, that is, the molar ratio of Co to the transition metal element Me, Co / Me, is preferably 0.05 to 0.3. In order to improve the discharge capacity and charge / discharge cycle performance of the lithium secondary battery, it is preferably 0.1 to 0.25.

Similarly, in order to improve the discharge capacity and charge / discharge cycle performance of the lithium secondary battery, the value of c, that is, the molar ratio of Mn to the transition metal element Me, Mn / Me, should be 0.1 to 0.4. Is preferable.

Further, a small amount of other metals such as alkali metals such as Na and K, alkaline earth metals such as Mg and Ca, and transition metals typified by 3d transition metals such as Fe and Zn, as long as the effects of the present invention are not impaired. Is not excluded.

In the present invention, in order to improve the charge / discharge cycle performance, the outermost surface Ni / Me of the lithium transition metal composite oxide constituting the surface layer is set to 0.1 to 0.4. Ni / Me is preferably 0.15 to 0.3. The Ni / Me of the surface layer is preferably smaller than the Ni / Me of the core.

Similarly, in order to improve the charge / discharge cycle performance, the Mn / Me on the outermost surface of the lithium transition metal composite oxide constituting the surface layer is preferably 0.4 to 0.8. The Mn / Me of the surface layer is preferably larger than the Mn / Me of the core.

The lithium transition metal composite oxide according to the present invention has a hexagonal structure. The lithium transition metal composite oxide after synthesis (before charging and discharging) is assigned to R3-m. It should be noted that "R3-m" should be originally described by adding a bar "-" on "3" of "R3m".

The lithium transition metal composite oxide according to the present invention has a diffraction peak assigned to the (104) plane when the space group R3-m is used as a crystal structure model based on the X-ray diffraction (using a CuKα radiation source) pattern. Half-value width F (003) of the diffraction peak (2θ = 18.6 ° ± 1 ° diffraction peak) attributed to the (003) plane with respect to the half-value width F (104) of (2θ = 44 ± 1 ° diffraction peak). The ratio of is not significantly different between when the potential is 4.45 ^{V (vs. Li / Li +} ) charged and when 2.0 V (vs. Li / Li +) is discharged, that is, 4.45 V (vs. Li / Li +). ^The value obtained by dividing the half-price width ratio F (003) / F (104) at +) by the half-price width ratio F (003) / F (104) at a potential of 2.0 V (vs. Li / Li ^{+) (hereinafter, “F”).} (003) / F (104), also referred to as “charge end / discharge end ratio”) is characterized in that it is between 0.9 and 1.1. By using a lithium transition metal composite oxide having this value between 0.9 and 1.1 as the positive electrode active material, a lithium secondary battery having a high discharge capacity can be obtained.
The lithium transition metal composite oxide preferably has F (003) in the range of 0.15 ° to 0.35 °, and F (104) in the range of 0.15 ° to 0.40 °. preferable.

The reason why the discharge capacity of the lithium secondary battery is improved by setting the half width ratio of the lithium transition metal composite oxide according to the present invention to the specific range as described above is presumed as follows.
Crystallographically, F (003) is a crystalline parameter along the c-axis direction, and F (00).
The larger the value of 3), the larger the lattice strain in the c-axis direction. On the other hand, F (104) is a parameter indicating three-dimensional crystallinity, and the larger F (104) is, the larger the lattice strain of the entire crystal is. Therefore, F (003) / F (104) is an index showing the anisotropic strain of the crystal, which is how the lattice is distorted in the c-axis direction with respect to the crystallinity of the entire crystal. Therefore, the ratio of F (003) / F (104) in the end-of-charge state to F (003) / F (104) in the end-discharge state indicates the degree of change in the anisotropic strain of the crystal during the charge / discharge process. There is.

Comparative Examples 1 and 2 described later are manufacturing conditions with high uniformity at the atomic level for Mn, and are F (003) / F (104) in the end-of-charge state and F (003) / F (104) in the end-discharge state. ) (Degree of change in strain) has a large deviation from 1 (less than 0.9). Comparative Examples 3 and 4 are manufacturing conditions in which the uniformity of Mn at the atomic level is considerably disturbed, and F (003) / F (104) in the end-of-charge state and F (003) / F in the end-discharge state. The ratio (degree of change in strain) of (104) also has a large deviation from 1 (greater than 1.1).
On the other hand, in the embodiment of the present invention described later, the homogeneity of Mn at the atomic level is between Comparative Examples 1 and 2 and Comparative Examples 3 and 4, but F (003) in the charged end state. The ratio of / F (104) to F (003) / F (104) in the end-of-discharge state is close to 1 (0.9 to 1.1), and the degree of change in strain is small. Therefore, it can be said that the examples control how the uniformity of Mn is disturbed at the atomic level. That is, a compound disturbance how uniformity is moderately controlled at the atomic level for Mn as a main phase, the result uniformity at the atomic level is disturbed by-product was Li ₂ MnO ₃ or the like in the particles The inventors speculate that the dispersion showed an excellent effect of improving the discharge capacity.

As described above, the present invention is a compound in which the disorder of homogeneity at the atomic level is appropriately controlled for Mn as the main phase, and the core is a “LiMeO _{type 2} ” compound. Therefore, the composition formula Li _{It is represented by 1 + x} Me _1-x O ₂ (Me: a transition metal containing Ni, Co and Mn). Here, by manufacturing so that x at the time of synthesis is larger than −0.1, it is possible to reduce the possibility that the charge end / discharge end ratio of F (003) / F (104) becomes too small, which is preferable. It is preferable to manufacture the product so that x at the time is smaller than 0.1 because the possibility that the above ratio becomes too large can be reduced.

Further, it is preferable that the lithium transition metal composite oxide does not change its structure during overcharging. This can be confirmed by observing as a single phase belonging to the space group R3-m on the X-ray diffraction pattern when electrochemically oxidized to a potential of 5.0 V (vs. Li ^{/ Li +).} As a result, a lithium secondary battery having excellent charge / discharge cycle performance can be obtained.

Further, the lithium transition metal composite oxide has an oxygen position parameter obtained from crystal structure analysis by the Rietveld method based on an X-ray diffraction pattern of 0.262 or less at the end of discharge and 0.267 or more at the end of charge. preferable. As a result, a lithium secondary battery having excellent high rate discharge performance can be obtained. The oxygen position parameter is the spatial coordinate of Me (transition metal) (0,0,0) for _{the α-NaFeO type 2} crystal structure of the lithium transition metal composite oxide belonging to the space group R3-m. The value of z when the spatial coordinates of Li (lithium) are defined as (0, 0, 1/2) and the spatial coordinates of O (oxygen) are defined as (0, 0, z). That is, the oxygen position parameter is a relative index indicating how far the O (oxygen) position is from the Me (transition metal) position.

BET specific surface area of the positive electrode active material according to the present invention, the initial efficiency, in order to obtain a lithium secondary battery having excellent high rate discharge performance, preferably at least 0.2m ² / g, 0.3-1.5m ² / G is more preferable.
The tap density is preferably 1.25 g / cc or more, more preferably 1.7 g / cc or more, in order to obtain a lithium secondary battery having excellent high rate discharge performance.

Next, a method for producing the active material for a lithium secondary battery of the present invention will be described.
The active material for a lithium secondary battery of the present invention basically contains a raw material containing the metal elements (Li, Ni, Co, Mn) constituting the active material according to the composition of the active material (oxide). It can be obtained by adjusting and firing this. However, regarding the amount of the Li raw material, it is preferable to add an excess of about 1 to 5% in anticipation that a part of the Li raw material will disappear during firing.
In producing the oxide having the desired composition, the so-called "solid phase method" in which the salts of Li, Ni, Co, and Mn are mixed and fired, or Ni, Co, and Mn are present in one particle in advance. A "coprecipitation method" is known in which a coprecipitation precursor is prepared, and a Li salt is mixed and calcined with the coprecipitation precursor. In the synthesis process by the "solid phase method", it is difficult to obtain a sample in which each element is uniformly distributed in one particle, because Mn is particularly difficult to dissolve uniformly in Ni and Co. In the literature and the like, many attempts have been made to dissolve Mn in a part of Ni or Co by the solid phase method (LiNi _1-x Mn _x O ₂ etc.), but the "coprecipitation method" is selected. It is easier to obtain a uniform phase at the atomic level. Therefore, in the examples described later, the "coprecipitation method" was adopted.

In producing a coprecipitated precursor, Mn among Ni, Co, and Mn is easily oxidized, and it is not easy to produce a coprecipitated precursor in which Ni, Co, and Mn are uniformly distributed in a divalent state. , Ni, Co, Mn at the atomic level tends to be inadequate. In the present invention, it is preferable to remove dissolved oxygen in order to control the amount of Mn compound produced in the particles of the coprecipitation precursor. Examples of the method for removing dissolved oxygen include a method of bubbling a gas containing no oxygen. The gas containing no oxygen is not limited, but nitrogen gas, argon gas, carbon dioxide (CO ₂ ) and the like can be used.

The pH in the step of coprecipitating a compound containing Ni, Co and Mn in a solution to prepare a precursor is not limited, but an attempt is made to prepare the coprecipitated precursor as a coprecipitated hydroxide precursor. If so, it can be 10.5 to 14. In order to increase the tap density, it is preferable to control the pH. By setting the pH to 11.5 or less, the tap density can be set to 1.00 g / cm ³ or more, and the high rate discharge performance can be improved. Further, by setting the pH to 11.0 or less, the particle growth rate can be promoted, so that the stirring duration after the completion of dropping the raw material aqueous solution can be shortened.
Further, when the coprecipitating precursor is to be prepared as a coprecipitating carbonate precursor, it can be 7.5 to 11. By setting the pH to 9.4 or less, the tap density can be set to 1.25 g / cc or more, and the high rate discharge performance can be improved. Further, by setting the pH to 8.0 or less, the particle growth rate can be promoted, so that the stirring duration after the completion of dropping the raw material aqueous solution can be shortened.

In the present invention, it is preferable to use a hydroxide as the coprecipitation precursor in order to make the inside of the positive electrode active material dense, enable small particles, and prevent the active material from adhering to the roll during electrode pressing. .. Further, a precursor having a larger bulk density can be produced by using a crystallization reaction using a complexing agent or the like. At that time, a higher density active material can be obtained by mixing and firing with the Li source, so that the energy density per electrode area can be improved.
In the present invention, when prepared from a co-precipitated hydroxide precursor, the particle size D50, which is the particle size at which the cumulative volume in the particle size distribution of the secondary particles of the lithium transition metal composite oxide is 50%, is preferably 18 μm or less, 4 ~ 12 μm is more preferable.

In the present invention, in order to control the amount of Mn compound that is finely and non-uniformly present in the particles of the core co-precipitation precursor, the compound containing Ni, Co and Mn is co-precipitated in the solution. in the step of preparing the core of the precursor, and characterized by N i, and contains a compound of Co and Mn, is added dropwise separately simultaneously with a solution containing a compound of the solution and Mn high content of a compound of Ni do. It is preferable to adopt a method in which two nozzles for lowering droplets containing Ni, Co (Ni, Co, Mn) and a nozzle for lowering droplets containing Mn are provided and the nozzles are simultaneously dropped.
By such a method, the amount of Mn compound produced finely and non-uniformly in the particles of the coprecipitation precursor can be controlled, and the lithium transition metal composite oxide having a specific half width ratio of the present invention can be obtained. Can be manufactured. Further, “simultaneous” means that a lithium transition metal composite oxide having a specific half width ratio of the present invention can be produced, and a slight time error is allowed.
In order to set the charge-end / discharge-end ratio of F (003) / F (104) of the lithium transition metal composite oxide to 0.9 to 1.1, the Ni / Me molar ratio of the precursor of the core is 0. within an amount of from 4 to 0.8, and the solution slightly containing a compound of containing Mn compound of Ni and Co, a method of dropping a solution separately at the same time containing the compound of Mn is not preferred. Further, it is preferable to drop a solution containing the Mn compound in the range where the Mn / Me molar ratio of the precursor of the core is 0.1 to 0.4.

A solution containing a compound of Ni, Co and Mn and having a high content of the compound of Ni and a solution containing a compound of Mn were separately and simultaneously added dropwise, and the Ni / Me molar ratio was 0.4 to 0.8. After preparing the precursor of the core, which is, the compound of Ni, Co and Mn is contained in order to prepare the precursor of the surface layer having the Ni / Me molar ratio of the outermost surface of 0.1 to 0.4. , A solution having a low content of Ni compound is added dropwise. As described above, when two Ni, Co-containing droplet lowering nozzles and Mn-containing droplet lowering nozzles are provided and dropped at the same time to prepare a core precursor, Ni supplied to the Ni, Co-containing droplet lowering nozzle. Ni It is preferable to adopt a method of dropping a solution containing a compound of Co and Mn and having a low content of the compound of Ni. Thereby, particles having an element concentration gradient can be formed from the core to the surface layer.

The raw material of the co-precipitation precursor is nickel hydroxide, nickel carbonate, nickel sulfate, nickel nitrate, nickel acetate or the like as the Ni compound, and cobalt sulfate, cobalt nitrate, cobalt acetate or the like as the Co compound, Mn compound. Examples thereof include manganese oxide, manganese carbonate, manganese sulfate, manganese nitrate, and manganese acetate.

The dropping rate of the raw material aqueous solution greatly affects the uniformity of the element distribution within one particle of the coprecipitation precursor to be produced. The preferred dropping rate is affected by the size of the reaction vessel, stirring conditions, pH, reaction temperature, etc., but is preferably 30 ml / min or less. In order to improve the discharge capacity, the dropping rate is more preferably 10 ml / min or less, and most preferably 5 ml / min or less.

Further, in order to obtain a lithium transition metal composite oxide having a particle size distribution having no maximum value of two or more, a solution containing a compound of Ni and Co and a compound of Mn are contained in the step of preparing a co-precipitated precursor of a core. The dropping time of the solution is preferably 16 h or more, and more preferably 20 h to 48 h. By using a lithium transition metal composite oxide whose particle size distribution does not have two or more maximum values as the positive electrode active material, the initial efficiency of the lithium secondary battery can be improved.

Further, when a complexing agent is present in the reaction vessel and certain convection conditions are applied, the rotation of the particles and the revolution in the stirring vessel are promoted by further stirring after the completion of dropping of the raw material aqueous solution. In this process, the particles gradually grow into convective spheres while colliding with each other. That is, the coprecipitation precursor undergoes a two-step reaction of a metal complex formation reaction when the raw material aqueous solution is dropped into the reaction vessel and a precipitation formation reaction that occurs while the metal complex is retained in the reaction vessel. It is formed. Therefore, a coprecipitation precursor having a target particle size can be obtained by appropriately selecting a time for continuing stirring after the completion of dropping of the raw material aqueous solution.

The preferable stirring duration after the completion of dropping the aqueous solution of the raw material is affected by the size of the reaction vessel, stirring conditions, pH, reaction temperature, etc., but 0.5 h or more is required to grow the particles as uniform spherical particles. Preferably, 1 h or more is more preferable. Further, in order to reduce the possibility that the output performance in the low SOC region of the battery becomes insufficient due to the particle size becoming too large, 30 hours or less is preferable, 25 hours or less is more preferable, and 20 hours or less is most preferable.

The active material for a lithium secondary battery of the present invention can be suitably produced by mixing the coprecipitation precursor and a Li compound and then heat-treating the mixture. As the Li compound, lithium hydroxide, lithium carbonate, lithium nitrate, lithium acetate and the like can be suitably produced. However, regarding the amount of the Li compound, it is preferable to add an excess of about 1 to 5% in anticipation that a part of the Li compound will disappear during firing.

The firing temperature affects the reversible capacity of the active material.
If the firing temperature is too low, crystallization does not proceed sufficiently and the electrode characteristics tend to deteriorate. In the present invention, the firing temperature is preferably at least 750 ° C. or higher. Sufficient crystallization can reduce the resistance of grain boundaries and promote smooth lithium ion transport.
In addition, the inventors analyzed in detail the half-value width of the diffraction peak of the active material of the present invention, and found that strain remained in the lattice in the sample synthesized at a temperature lower than 750 ° C., and at a temperature higher than that. It was confirmed that most of the strain could be removed by synthesizing. In addition, the size of the crystallites increased in proportion to the increase in the synthesis temperature. Therefore, even in the composition of the active material of the present invention, a good discharge capacity can be obtained by aiming at particles in which there is almost no lattice strain in the system and the crystallite size is sufficiently grown. Specifically, it is preferable to adopt a synthesis temperature (calcination temperature) and a Li / Me ratio composition such that the amount of strain exerted on the lattice constant is 2% or less and the crystallite size grows to 50 nm or more. all right. Changes due to expansion and contraction can be seen by molding these as electrodes and performing charge / discharge, but it is preferable as an effect that the crystallite size is maintained at 30 nm or more even in the charge / discharge process.

On the other hand, if the firing temperature is too high, the structure changes from a layered hexagonal structure to a rock salt-type cubic structure, which ^{is disadvantageous for Li +} movement in the active material during the charge / discharge reaction, and the discharge performance deteriorates.
Therefore, when firing the positive electrode active material containing the lithium transition metal composite oxide of the present invention in order to improve the cycle life as well as the discharge capacity, the firing temperature is preferably 750 to 900 ° C.
As described above, the positive electrode active material is produced.

The negative electrode material is not limited, and any material may be selected as long as it can release or occlude lithium ions. For _{example, Li [Li 1/3 Ti 5/3]} O 4 titanium-based material of lithium titanate having a spinel type crystal structure typified by, Si and Sb, the alloy material of lithium metal, such as Sn-based, lithium alloys (Lithium-metal-containing alloys such as lithium-silicon, lithium-aluminum, lithium-lead, lithium-tin, lithium-aluminum-tin, lithium-gallium, and wood alloys), lithium composite oxide (lithium-titanium), silicon oxide In addition, alloys capable of storing and releasing lithium, carbon materials (for example, graphite, hard carbon, low-temperature calcined carbon, amorphous carbon, etc.) and the like can be mentioned.

It is desirable that the powder of the positive electrode active material and the powder of the negative electrode material have an average particle size of 100 μm or less. In particular, the powder of the positive electrode active material is preferably 10 μm or less for the purpose of improving the high output characteristics of the non-aqueous electrolyte battery. A crusher or a classifier is used to obtain the powder in a predetermined shape. For example, a mortar, a ball mill, a sand mill, a vibrating ball mill, a planetary ball mill, a jet mill, a counter jet mill, a swirling airflow type jet mill, a sieve, or the like is used. At the time of pulverization, wet pulverization in which water or an organic solvent such as hexane coexists can also be used. The classification method is not particularly limited, and a sieve, a wind power classifier, or the like is used as needed for both dry and wet types.

The positive electrode active material and the negative electrode material, which are the main constituents of the positive electrode and the negative electrode, have been described in detail above. Etc. may be contained as other constituent components.

The conductive agent is not limited as long as it is an electron conductive material that does not adversely affect the battery performance, but is usually natural graphite (scaly graphite, scaly graphite, earthy graphite, etc.), artificial graphite, carbon black, acetylene black, etc. Conductive materials such as Ketjen black, carbon whisker, carbon fiber, metal (copper, nickel, aluminum, silver, gold, etc.) powder, metal fiber, conductive ceramic material, etc. can be included as one kind or a mixture thereof. ..

Among these, acetylene black is desirable as the conductive agent from the viewpoint of electron conductivity and coatability. The amount of the conductive agent added is preferably 0.1% by weight to 50% by weight, particularly preferably 0.5% by weight to 30% by weight, based on the total weight of the positive electrode or the negative electrode. In particular, it is desirable to use acetylene black pulverized into ultrafine particles of 0.1 to 0.5 μm because the required carbon amount can be reduced. These mixing methods are physical mixing, and the ideal is uniform mixing. Therefore, it is possible to mix powder mixers such as V-type mixers, S-type mixers, mixers, ball mills, and planetary ball mills in a dry or wet manner.

Examples of the binder include thermoplastic resins such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyethylene and polypropylene, ethylene-propylene-dienter polymer (EPDM), sulfonated EPDM and styrene butadiene. A polymer having rubber elasticity such as rubber (SBR) and fluororubber can be used as one kind or a mixture of two or more kinds. The amount of the binder added is preferably 1 to 50% by weight, particularly preferably 2 to 30% by weight, based on the total weight of the positive electrode or the negative electrode.

The filler may be any material that does not adversely affect the battery performance. Usually, olefin polymers such as polypropylene and polyethylene, amorphous silica, alumina, zeolite, glass, carbon and the like are used. The amount of the filler added is preferably 30% by weight or less with respect to the total weight of the positive electrode or the negative electrode.

For the positive electrode and the negative electrode, the main constituents (positive electrode active material in the positive electrode, negative electrode material in the negative electrode) and other materials are kneaded to form a mixture, which is mixed with an organic solvent such as N-methylpyrrolidone or toluene or water. After that, the obtained mixed solution is coated on a current collector such as an aluminum foil, or pressure-bonded and heat-treated at a temperature of about 50 ° C. to 250 ° C. for about 2 hours to be suitably produced. Regarding the coating method, for example, it is desirable to apply the coating to an arbitrary thickness and an arbitrary shape by using a means such as a roller coating such as an applicator roll, a screen coating, a doctor blade method, a spin coating, or a bar coater.
It is not limited to these.

The non-aqueous electrolyte used in the lithium secondary battery according to the present invention is not limited, and those generally proposed for use in lithium batteries and the like can be used. Examples of the non-aqueous solvent used for the non-aqueous electrolyte include cyclic carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, chloroethylene carbonate and vinylene carbonate; cyclic esters such as γ-butylolactone and γ-valerolactone; dimethyl carbonate, Chain carbonates such as diethyl carbonate and ethyl methyl carbonate; Chain esters such as methyl formate, methyl acetate and methyl butyrate; tetrahydrofuran or its derivatives; 1,3-dioxane, 1,4-dioxane, 1,2-dimethoxy Ethers such as ethane, 1,4-dibutoxyethane, methyl diglyme; nitriles such as acetonitrile and benzonitrile; dioxolane or derivatives thereof; ethylene sulfide, sulfolane, sulton or derivatives thereof, etc. alone or two or more thereof Mixtures and the like can be mentioned, but the present invention is not limited to these.

Examples of the electrolyte salt used for the non-aqueous electrolyte include LiClO ₄ , LiBF _{4 , LiAsF 6} , LiPF ₆ , LiSCN, LiBr, LiI, Li ₂ SO ₄ , Li ₂ B ₁₀ Cl ₁₀ , NaClO ₄ , NaI, NaSCN, NaBr. , KClO ₄ , KSCN and other inorganic ion salts containing one of lithium (Li), sodium (Na) or potassium (K), LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅₎ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) ₃ , (CH ₃ ) ₄ NBF ₄ , ( CH ₃ ) ₄ NBr, (C ₂ H ₅ ) ₄ NClO ₄ , (C ₂ H ₅ ) ₄ NI, (C ₃ H ₇ ) ₄ NBr, (n-C ₄ H ₉ ) ₄ NClO ₄ , (n-C) ₄ H ₉ ) ₄ NI, (C ₂ H ₅ ) ₄ N-maleate, (C ₂ H ₅ ) ₄ N-benzoate, (C ₂ H ₅ ) ₄ N-phthate, lithium stearyl sulfonate, lithium octyl sulfonate, Examples thereof include organic ionic salts such as lithium dodecylbenzenesulfonate, and these ionic compounds can be used alone or in combination of two or more.

Furthermore, _{by using a mixture of LiPF 6} or LiBF ₄ and a lithium salt having a perfluoroalkyl group such as LiN (C ₂ F ₅ SO ₂ ) ₂ , the viscosity of the electrolyte can be further reduced. It is more desirable because the low temperature characteristics can be further enhanced and self-discharge can be suppressed.

Further, a room temperature molten salt or an ionic liquid may be used as the non-aqueous electrolyte.

The concentration of the electrolyte salt in the non-aqueous electrolyte is preferably 0.1 mol / l to 5 mol / l, more preferably 0.5 mol / l to 2 in order to surely obtain a non-aqueous electrolyte battery having high battery characteristics. It is .5 mol / l.

As the separator, it is preferable to use a porous membrane, a non-woven fabric, or the like exhibiting excellent high-rate discharge performance alone or in combination. Examples of the material constituting the separator for a non-aqueous electrolyte battery include polyolefin resins typified by polyethylene and polypropylene, polyester resins typified by polyethylene terephthalate and polybutylene terephthalate, polyvinylidene fluoride, vinylidene fluoride-hexa. Fluoropropylene copolymer, vinylidene fluoride-perfluorovinyl ether copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-fluoroethylene copolymer, foot Vinylidene-hexafluoroacetone copolymer, vinylidene fluoride-ethylene copolymer, vinylidene fluoride-propylene copolymer, vinylidene fluoride-trifluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene Examples thereof include a copolymer, a vinylidene fluoride-ethylene-tetrafluoroethylene copolymer and the like.

The porosity of the separator is preferably 98% by volume or less from the viewpoint of strength. Further, from the viewpoint of charge / discharge characteristics, the porosity is preferably 20% by volume or more.

Further, as the separator, a polymer gel composed of a polymer such as acrylonitrile, ethylene oxide, propylene oxide, methyl methacrylate, vinyl acetate, vinylpyrrolidone, polyvinylidene fluoride and the like and an electrolyte may be used. It is preferable to use the non-aqueous electrolyte in the gel state as described above because it has an effect of preventing liquid leakage.

Further, when the separator is used in combination with the above-mentioned porous membrane, non-woven fabric or the like and the polymer gel, it is desirable because the liquid retention property of the electrolyte is improved. That is, the pro-solvent polymer is formed by forming a film coated with a pro-solvent polymer having a thickness of several μm or less on the surface of the polyethylene micropore membrane and the micropore wall surface, and retaining the electrolyte in the micropores of the film. Gells.

Examples of the pro-solvent polymer include polyvinylidene fluoride, an acrylate monomer having an ethylene oxide group and an ester group, an epoxy monomer, a polymer having a crosslinked monomer such as an isocyanato group, and the like. The monomer can be subjected to a cross-linking reaction by heating or using ultraviolet rays (UV) in combination with a radical initiator, or by using active rays such as an electron beam (EB).

Other components of the battery include terminals, an insulating plate, a battery case, and the like, but these parts may be the same as those conventionally used.

FIG. 1 shows an external perspective view of a rectangular lithium secondary battery 1, which is an embodiment of the lithium secondary battery according to the present invention. The figure is a perspective view of the inside of the container. In the lithium secondary battery 1 shown in FIG. 1, the electrode group 2 is housed in the battery container 3. The electrode group 2 is formed by winding a positive electrode having a positive electrode active material and a negative electrode having a negative electrode active material through a separator. The positive electrode is electrically connected to the positive electrode terminal 4 via the positive electrode lead 4', and the negative electrode is electrically connected to the negative electrode terminal 5 via the negative electrode lead 5'.

The shape of the lithium secondary battery according to the present invention is not particularly limited, and examples thereof include a cylindrical battery, a square battery (rectangular battery), and a flat battery. The present invention can also be realized as a power storage device in which a plurality of the above-mentioned lithium secondary batteries are assembled. An embodiment of the power storage device is shown in FIG. In FIG. 2, the power storage device 30 includes a plurality of power storage units 20. Each power storage unit 20 includes a plurality of lithium secondary batteries 1. The power storage device 30 can be mounted as a power source for automobiles such as electric vehicles (EV), hybrid electric vehicles (HEV), and plug-in hybrid vehicles (PHEV).

(Example 1)
448.4 g of nickel sulfate hexahydrate, 79.9 g of cobalt sulfate heptahydrate, and 171.4 g of manganese sulfate pentahydrate were weighed, and all of these were dissolved in 2.7 L of ion-exchanged water to dissolve Ni: Co. A 1.0 M sulfate aqueous solution having a molar ratio of Mn of 6: 1: 2.5 was prepared. This is referred to as undiluted solution 1. On the other hand, 34.3 g of manganese sulfate pentahydrate was weighed, and a 0.05 M aqueous sulfate solution was prepared by dissolving all of these in 2.7 L of ion-exchanged water. This is used as the stock solution 2.
Further, 14.2 g of nickel sulfate hexahydrate, 15.2 g of cobalt sulfate heptahydrate, and 39.1 g of manganese sulfate pentahydrate were weighed, and all of these were dissolved in 0.27 L of ion-exchanged water to obtain Ni. A 1.0 M aqueous sulfate solution having a molar ratio of: Co: Mn of 2: 2: 6 was prepared. This is referred to as undiluted solution 3.
Example In the preparation of the active material, a hydroxide precursor was prepared by using a reaction crystallization method.
First, 2 L of ion-exchanged water was poured into a 5 L reaction vessel, and Ar gas was bubbled for 30 minutes to remove oxygen contained in the ion-exchanged water. The temperature of the reaction vessel is set to 50 ° C. (± 2 ° C.), and the inside of the reaction vessel is stirred at a rotation speed of 1500 rpm using a paddle blade equipped with a stirring motor so that convection occurs sufficiently in the reaction layer. bottom. The sulfate stock solutions 1 and 2 were added dropwise at a rate of 1.5 ml / min, respectively. Here, the pH in the reaction vessel is adjusted by appropriately dropping a mixed alkaline solution consisting of 4.0 M sodium hydroxide, 0.5 M ammonia, and 0.5 M hydrazine from the start to the end of the dropping. It was controlled so as to always maintain 11.0 (± 0.1), and a part of the reaction solution was discharged by overflow so that the total amount of the reaction solution did not always exceed 2 L. Twenty-seven hours after the start of dropping the stock solutions 1 and 2, 0.27 L of the stock solution 3 remained, and 0.135 L of the stock solution 3 was added dropwise to the stock solutions 1 and 2 at a rate of 0.5 ml / min, respectively.
After completion of the dropping, stirring in the reaction vessel was continued for another 3 hours. After the stirring was stopped, the mixture was allowed to stand at room temperature for 12 hours or more.
Next, the hydroxide precursor particles generated in the reaction vessel are separated using a suction filtration device, and sodium ions adhering to the particles are washed and removed using ion-exchanged water, and an electric furnace is used. Then, it was dried at 80 ° C. for 20 hours under normal pressure in an air atmosphere. Then, in order to make the particle size uniform, it was crushed in an agate automatic mortar for several minutes. In this way, a hydroxide precursor having a core Ni: Co: Mn molar ratio of 6: 1: 3 and an outermost surface Ni: Co: Mn molar ratio of 2: 2: 6 in the surface layer is prepared. Made.

To 1.898 g of the hydroxide precursor, 0.897 g of lithium hydroxide monohydrate was added and mixed well using an automatic agate mortar, and the molar ratio of Li: (Ni, Co, Mn) was 1: 1. A mixed powder of 1 was prepared. It was molded at a pressure of 6 MPa using a pellet molding machine to obtain pellets having a diameter of 25 mm. The amount of the mixed powder used for pellet molding was determined by converting so that the assumed mass of the final product was 2 g. One of the pellets was placed on an alumina boat having a total length of about 100 mm, installed in a box-type electric furnace (model number: AMF20), and heated in an air atmosphere under normal pressure from room temperature to 850 ° C. over 10 hours. It was calcined at 850 ° C. for 5 hours. The internal dimensions of the box-type electric furnace are 10 cm in length, 20 cm in width, and 30 cm in depth, and heating wires are inserted at intervals of 20 cm in the width direction. After firing, the heater was switched off and the alumina boat was allowed to cool naturally while still in the furnace. As a result, the temperature of the furnace drops to about 200 ° C. after 5 hours, but the subsequent temperature lowering rate is rather slow. After a day and night, after confirming that the temperature of the furnace was 100 ° C. or lower, the pellets were taken out and crushed in an agate automatic mortar for several minutes in order to make the particle size uniform. In this way, the lithium transition metal composite oxide according to Example 1 was prepared.

(Example 2)
In the hydroxide precursor preparation step, 463.1 g of nickel sulfate hexahydrate, 82.5 g of cobalt sulfate heptahydrate and 155.7 g of manganese sulfate pentahydrate were weighed, and the molar ratio of Ni: Co: Mn was measured. A 1.0 M aqueous sulfate solution having a ratio of 6: 1: 2.2 was prepared and used as the undiluted solution 1, and 52.1 g of manganese sulfate pentahydrate was weighed and all of these were dissolved. A lithium transition metal composite oxide according to Example 2 was prepared in the same manner as in Example 1 except that a 0.08 M sulfate aqueous solution was prepared and used as the stock solution 2.

(Example 3)
In the hydroxide precursor preparation step, 484.1 g of nickel sulfate hexahydrate, 86.3 g of cobalt sulfate heptahydrate and 133.2 g of manganese sulfate pentahydrate were weighed, and the molar ratio of Ni: Co: Mn was measured. A 1.0 M aqueous sulfate solution having a value of 6: 1: 1.8 was prepared, and this was used as the stock solution 1, and 78.1 g of manganese sulfate pentahydrate was weighed and all of these were dissolved. A lithium transition metal composite oxide according to Example 3 was prepared in the same manner as in Example 1 except that a 12 M aqueous sulfate solution was prepared and used as the stock solution 2.

(Example 4)
In the hydroxide precursor preparation step, 501.2 g of nickel sulfate hexahydrate, 89.3 g of cobalt sulfate heptahydrate and 114.9 g of manganese sulfate pentahydrate were weighed, and the molar ratio of Ni: Co: Mn was measured. A 1.0 M aqueous sulfate solution having a ratio of 6: 1: 1.5 was prepared, and this was used as the undiluted solution 1, and 117.2 g of manganese sulfate pentahydrate was weighed and all of these were dissolved. A lithium transition metal composite oxide according to Example 4 was prepared in the same manner as in Example 1 except that a .15 M sulfate aqueous solution was prepared and used as the stock solution 2.

(Example 5)
In the hydroxide precursor preparation step, 519.5 g of nickel sulfate hexahydrate, 92.6 g of cobalt sulfate heptahydrate and 95.3 g of manganese sulfate pentahydrate were weighed, and the molar ratio of Ni: Co: Mn was measured. A 1.0 M aqueous sulfate solution having a ratio of 6: 1: 1.2 was prepared, and this was used as the undiluted solution 1, and 117.2 g of manganese sulfate pentahydrate was weighed and all of these were dissolved. A lithium transition metal composite oxide according to Example 5 was prepared in the same manner as in Example 1 except that a .18 M sulfate aqueous solution was prepared and used as the stock solution 2.

(Example 6)
In the hydroxide precursor preparation step, 532.5 g of nickel sulfate hexahydrate, 94.9 g of cobalt sulfate heptahydrate and 81.4 g of manganese sulfate pentahydrate were weighed, and the molar ratio of Ni: Co: Mn was measured. A 1.0 M aqueous sulfate solution having a ratio of 6: 1: 1.0 was prepared, and this was used as the stock solution 1, and 130.2 g of manganese sulfate pentahydrate was weighed and all of these were dissolved. A lithium transition metal composite oxide according to Example 6 was prepared in the same manner as in Example 1 except that a 20 M aqueous sulfate solution was prepared and used as the stock solution 2.

(Example 7)
In the hydroxide precursor preparation step, 568.0 g of nickel sulfate hexahydrate, 101.2 g of cobalt sulfate heptahydrate and 43.4 g of manganese sulfate pentahydrate were weighed, and the molar ratio of Ni: Co: Mn was measured. A 1.0 M aqueous sulfate solution having a ratio of 6: 1: 0.5 was prepared, and this was used as the stock solution 1, and 162.8 g of manganese sulfate pentahydrate was weighed and all of these were dissolved. A lithium transition metal composite oxide according to Example 7 was prepared in the same manner as in Example 1 except that a .25 M sulfate aqueous solution was prepared and used as the stock solution 2.

(Example 8)
In the hydroxide precursor preparation step, 597.9 g of nickel sulfate hexahydrate, 79.9 g of cobalt sulfate heptahydrate and 34.3 g of manganese sulfate pentahydrate were weighed, and all of these were dissolved to dissolve Ni. A 1.0 M sulfate aqueous solution having a molar ratio of: Co: Mn of 8: 1: 0.5 was prepared and used as the stock solution 1, and 28.4 g of nickel sulfate hexahydrate and cobalt sulfate were prepared. 15.2 g of heptahydrate and 26.1 g of manganese sulfate pentahydrate are weighed and all of them are dissolved to obtain a 1.0 M sulfate having a Ni: Co: Mn molar ratio of 4: 2: 4. The lithium transition metal composite oxide according to Example 8 was prepared in the same manner as in Example 1 except that an aqueous solution was prepared and used as the undiluted solution 3. In Example 8, the hydroxide precursor has a core Ni: Co: Mn molar ratio of 8: 1: 1 and an outermost surface Ni: Co: Mn molar ratio of 4: 2: 4. Met.

(Example 9)
In the hydroxide precursor preparation step, 552.3 g of nickel sulfate hexahydrate, 84.4 g of cobalt sulfate heptahydrate and 72.4 g of manganese sulfate pentahydrate were weighed, and all of these were dissolved to dissolve Ni. A 1.0 M sulfate aqueous solution having a molar ratio of: Co: Mn of 7: 1: 1 was prepared, and this was used as the undiluted solution 1, and 65.1 g of manganese sulfate pentahydrate was weighed and the total amount thereof. A 0.10 M sulfate aqueous solution was prepared and used as the stock solution 2, and 21.3 g of nickel sulfate hexahydrate, 22.8 g of cobalt sulfate heptahydrate and manganese sulfate pentahydrate were prepared. Except for the fact that 26.1 g of the product was weighed and all of these were dissolved to prepare a 1.0 M sulfate aqueous solution having a Ni: Co: Mn molar ratio of 3: 3: 4, which was used as the undiluted solution 3. Made a lithium transition metal composite oxide according to Example 9 in the same manner as in Example 1. In Example 9, the hydroxide precursor has a core Ni: Co: Mn molar ratio of 7: 1: 2 and an outermost surface Ni: Co: Mn molar ratio of 3: 3: 4. Met.

(Example 10)
In the hydroxide precursor preparation step, 417.7 g of nickel sulfate hexahydrate, 178.7 g of cobalt sulfate heptahydrate and 114.9 g of manganese sulfate pentahydrate were weighed, and all of these were dissolved to dissolve Ni. A 1.0 M sulfate aqueous solution having a molar ratio of: Co: Mn of 5: 2: 1.5 was prepared, and this was used as the stock solution 1, and 97.7 g of manganese sulfate pentahydrate was weighed and these were used. A 0.15 M sulfate aqueous solution was prepared by dissolving the entire amount of the above, and this was used as the stock solution 2, and 10.7 g of nickel sulfate hexahydrate, 11.4 g of cobalt sulfate heptahydrate, and manganese sulfate 5 were prepared. Weigh 45.6 g of hydrate and dissolve all of them to prepare a 1.0 M sulfate aqueous solution having a Ni: Co: Mn molar ratio of 1.5: 1.5: 7. The lithium transition metal composite oxide according to Example 10 was prepared in the same manner as in Example 1 except that the undiluted solution 3 was used. In Example 10, the hydroxide precursor has a core Ni: Co: Mn molar ratio of 5: 2: 3, and the outermost surface Ni: Co: Mn molar ratio of 1.5: 1 in the surface layer. It was .5: 7.

(Example 11)
In the hydroxide precursor preparation step, 355.0 g of nickel sulfate hexahydrate, 189.8 g of cobalt sulfate heptahydrate and 162.8 g of manganese sulfate pentahydrate were weighed, and all of these were dissolved to dissolve Ni. A 1.0 M sulfate aqueous solution having a molar ratio of: Co: Mn of 4: 2: 2 was prepared, and this was used as the undiluted solution 1, and 130.2 g of manganese sulfate pentahydrate was weighed and the total amount thereof. A 0.20 M sulfate aqueous solution was prepared and used as the stock solution 2, and 7.1 g of nickel sulfate hexahydrate, 7.6 g of cobalt sulfate heptahydrate and manganese sulfate pentahydrate were prepared. 52.1 g of the product was weighed and all of these were dissolved to prepare a 1.0 M sulfate aqueous solution having a Ni: Co: Mn molar ratio of 1: 1: 8, except that this was used as the undiluted solution 3. Made a lithium transition metal composite oxide according to Example 11 in the same manner as in Example 1. In Example 11, the hydroxide precursor has a core Ni: Co: Mn molar ratio of 4: 2: 4 and an outermost surface Ni: Co: Mn molar ratio of 1: 1: 8. Met.

(Comparative Example 1)
In the hydroxide precursor preparation step, 434.7 g of nickel sulfate hexahydrate, 77.5 g of cobalt sulfate heptahydrate and 186.1 g of manganese sulfate pentahydrate were weighed, and the molar ratio of Ni: Co: Mn was measured. A 1.0 M aqueous sulfate solution having a ratio of 6: 1: 2.8 was prepared and used as the undiluted solution 1, and 13.0 g of manganese sulfate pentahydrate was weighed and all of these were dissolved. A lithium transition metal composite oxide according to Comparative Example 1 was prepared in the same manner as in Example 1 except that a 0.02M sulfate aqueous solution was prepared and used as the stock solution 2.

(Comparative Example 2)
In the hydroxide precursor preparation step, 448.4 g of nickel sulfate hexahydrate, 79.9 g of cobalt sulfate heptahydrate, and 195.4 g of manganese sulfate pentahydrate were weighed, and all of these were dissolved to dissolve Ni. A 1.0 M sulfate aqueous solution having a molar ratio of: Co: Mn of 6: 1: 3.0 was prepared and used as the undiluted solution 1, and only the undiluted solution 1 was added dropwise without using the undiluted solution 2. Subsequently, the lithium transition metal composite oxide according to Comparative Example 2 was prepared in the same manner as in Example 1 except that the undiluted solution 3 was added dropwise.

(Comparative Example 3)
In the hydroxide precursor preparation step, 587.6 g of nickel sulfate hexahydrate, 104.7 g of cobalt sulfate heptahydrate and 22.5 g of manganese sulfate pentahydrate were weighed, and the molar ratio of Ni: Co: Mn was measured. A 1.0 M aqueous sulfate solution having a ratio of 6: 1: 0.25 was prepared, and this was used as the stock solution 1, and 179.1 g of manganese sulfate pentahydrate was weighed and all of these were dissolved. A lithium transition metal composite oxide according to Comparative Example 3 was prepared in the same manner as in Example 1 except that a 275 M aqueous sulfate solution was prepared and used as the stock solution 2.

(Comparative Example 4)
In the hydroxide precursor preparation step, a 1.0 M sulfate aqueous solution having a Ni: Co: Mn molar ratio of 6: 1: 0 was prepared without adding manganese sulfate pentahydrate to the stock solution 1. This was used as the undiluted solution 1, and 195.4 g of manganese sulfate pentahydrate was weighed to prepare a 0.3 M sulfate aqueous solution in which all of these were dissolved, and this was carried out except that the undiluted solution 2 was used. The lithium transition metal composite oxide according to Comparative Example 4 was prepared in the same manner as in Example 1.

(Comparative Example 5)
In the hydroxide precursor preparation step, 292.4 g of nickel sulfate hexahydrate, 268.0 g of cobalt sulfate heptahydrate and 153.2 g of manganese sulfate pentahydrate were weighed, and all of these were dissolved to dissolve Ni. A 1.0 M aqueous sulfate solution having a molar ratio of: Co: Mn of 3.5: 3: 2 was prepared, and this was used as the undiluted solution 1, and 97.7 g of manganese sulfate pentahydrate was weighed and these. A 0.15 M sulfate aqueous solution in which the entire amount of the above was dissolved was prepared, and the lithium transition metal composite oxide according to Comparative Example 5 was prepared in the same manner as in Example 1 except that this was used as the stock solution 2. In Comparative Example 5, the hydroxide precursor had a core Ni: Co: Mn molar ratio of 3.5: 3: 3.5 and an outermost surface Ni: Co: Mn molar ratio of 2 in the surface layer. : It was 2: 6.

(Comparative Example 6)
In the hydroxide precursor preparation step, 266.3 g of nickel sulfate hexahydrate, 284.8 g of cobalt sulfate heptahydrate and 162.8 g of manganese sulfate pentahydrate were weighed, and all of these were dissolved to dissolve Ni. A 1.0 M aqueous sulfate solution having a molar ratio of: Co: Mn of 3: 3: 2 was prepared and used as the undiluted solution 1, and 130.2 g of manganese sulfate pentahydrate was weighed and the total amount thereof. A 0.20 M sulfate aqueous solution was prepared by dissolving the above, and the lithium transition metal composite oxide according to Comparative Example 6 was prepared in the same manner as in Example 1 except that this was used as the stock solution 2. In Comparative Example 6, the hydroxide precursor had a core Ni: Co: Mn molar ratio of 3: 3: 4 and an outermost surface Ni: Co: Mn molar ratio of 2: 2: 6. Met.

(Comparative Example 7)
In the hydroxide precursor preparation step, 635.3 g of nickel sulfate hexahydrate, 40.0 g of cobalt sulfate heptahydrate and 34.3 g of manganese sulfate pentahydrate were weighed, and all of these were dissolved to dissolve Ni. A 1.0 M sulfate aqueous solution having a molar ratio of: Co: Mn of 8.5: 0.5: 0.5 was prepared, and this was used as the undiluted solution 1 in the same manner as in Example 1. A lithium transition metal composite oxide according to Comparative Example 7 was prepared. In Comparative Example 7, the hydroxide precursor had a core Ni: Co: Mn molar ratio of 8.5: 0.5: 1 and an outermost surface Ni: Co: Mn molar ratio of 2 in the surface layer. : It was 2: 6.

(Comparative Example 8)
In the hydroxide precursor preparation step, 655.4 g of nickel sulfate hexahydrate, 38.9 g of cobalt sulfate heptahydrate, and 16.7 g of manganese sulfate pentahydrate were weighed, and all of these were dissolved to dissolve Ni. A 1.0 M aqueous sulfate solution having a molar ratio of: Co: Mn of 9: 0.5: 0.25 was prepared, and this was used as the undiluted solution 1, and 16.3 g of manganese sulfate pentahydrate was weighed. , A 0.025 M sulfate aqueous solution in which all of these was dissolved was prepared, and the lithium transition metal composite oxide according to Comparative Example 8 was prepared in the same manner as in Example 1 except that this was used as the stock solution 2. bottom. In Comparative Example 8, the hydroxide precursor has a core Ni: Co: Mn molar ratio of 9: 0.5: 0.5 and an outermost surface Ni: Co: Mn molar ratio of 2 in the surface layer. : It was 2: 6.

(Comparative Example 9)
Weighing 319.5 g of nickel sulfate hexahydrate, 75.9 g of cobalt sulfate heptahydrate, and 293.1 g of manganese sulfate pentahydrate, all of these were dissolved, and the molar ratio of Ni: Co: Mn was 4. .5: The lithium transition metal composite oxide according to Comparative Example 9 in the same manner as in Example 4 except that a 1.0 M sulfate aqueous solution having a ratio of 1: 4.5 was prepared and used as the stock solution 3. Was produced.

(Comparative Example 10)
Weighing 355.0 g of nickel sulfate hexahydrate, 75.9 g of cobalt sulfate heptahydrate, and 260.5 g of manganese sulfate pentahydrate, all of them were dissolved, and the molar ratio of Ni: Co: Mn was 5. A 1.0 M sulfate aqueous solution having a ratio of 1: 4 was prepared, and the lithium transition metal composite oxide according to Comparative Example 10 was prepared in the same manner as in Example 4 except that this was used as the stock solution 3.

(Comparative Example 11)
426.0 g of nickel sulfate hexahydrate, 75.9 g of cobalt sulfate heptahydrate, and 195.4 g of manganese sulfate pentahydrate were weighed and all of them were dissolved, and the molar ratio of Ni: Co: Mn was 6. A 1.0 M sulfate aqueous solution having a ratio of 1: 3 was prepared, and the lithium transition metal composite oxide according to Comparative Example 11 was prepared in the same manner as in Example 4 except that this was used as the stock solution 3.

(Comparative Example 12)
Weighing 35.5 g of nickel sulfate hexahydrate, 75.9 g of cobalt sulfate heptahydrate, and 553.6 g of manganese sulfate pentahydrate, all of these were dissolved, and the molar ratio of Ni: Co: Mn was 0. The lithium transition metal composite oxide according to Comparative Example 12 was prepared in the same manner as in Example 4 except that a 1.0 M sulfate aqueous solution having a ratio of .5: 1: 8.5 was prepared and used as the stock solution 3. Was produced.

(Comparative Example 13)
75.9 g of cobalt sulfate heptahydrate and 586.1 g of manganese sulfate pentahydrate are weighed and all of them are dissolved to obtain a molar ratio of Ni: Co: Mn of 1.0 M. A lithium transition metal composite oxide according to Comparative Example 13 was prepared in the same manner as in Example 4 except that an aqueous sulfate solution was prepared and used as the stock solution 3.

(Measurement of Ni concentration in core and surface layer)
For each of the lithium transition metal composite oxides according to Examples 1 to 11 and Comparative Examples 1 to 13, a scanning electron microscope (SEM) (manufactured by JEOL, model number JSM-6360) and an energy dispersive type attached thereto. Using an X-ray analysis (EDX: Energy dispersive X-ray spectroscopy) device (hereinafter, also referred to as “SEM-EDX device”), the metal composition ratio from the surface layer to the core of the particles was measured by the following procedure.

In a ring made of acrylic resin (outer diameter 10 mm, inner diameter 8 mm), an appropriate amount of lithium transition metal composite oxide particles to be measured is collected by a spatula and put into the ring, and a two-component epoxy resin for curing is further poured. It was cured. Next, using a polishing machine (Wingo Seiki GPM GRINDING & POLISHING) and Emily polishing paper (# 180), polish so that the cross section of the particles appears, and finally using Emily polishing paper (# 1000). The surface was polished. Platinum was vapor-deposited on the polished surface and set in the SEM-EDX apparatus. The working distance of the analysis position was 10 mm, and the acceleration voltage of the electron gun was 15 kV. By SEM observation, particles having a cross section including the center of the particles exposed on the observation surface, which are suitable for cross-section observation, were selected. The elements to be analyzed were Co, Ni and Mn. As shown in FIG. 3, the measurement points are divided into 10 equal parts with the center of the particle as Point 0 and the outermost surface of the particle as Point 10, and the molar concentrations of Co, Ni and Mn at each measurement point from Point 0 to Point 10 The ratio of the molar concentrations of Co, Ni and Mn to the total of the above was calculated. Then, with Point 0 to Point 9 as the core and Point 9 to Point 10 as the surface layer, the molar concentrations of each were averaged to determine the molar concentrations of Co, Ni, and Mn of the core and the surface layer.

(Measurement of particle size)
The particle size distribution of the lithium transition metal composite oxides according to Examples 1 to 11 and Comparative Examples 1 to 13 was measured according to the following conditions and procedures. A Microtrac (model number: MT3000) manufactured by Nikkiso Co., Ltd. was used as the measuring device. The measuring device comprises an optical table, a sample supply unit, and a computer equipped with control software, and a wet cell equipped with a laser light transmitting window is installed in the optical table. The measurement principle is a method in which a wet cell in which a dispersion liquid in which a measurement target sample is dispersed in a dispersion solvent circulates is irradiated with laser light, and the scattered light distribution from the measurement sample is converted into a particle size distribution. The dispersion is stored in the sample supply section and circulated and supplied to the wet cell by a pump. Ultrasonic vibration is constantly applied to the sample supply unit. Water was used as the dispersion solvent. Microtrac DHS for Win98 (MT3000) was used as the measurement control software. For the "substance information" to be set and input to the measuring device, 1.33 is set as the "refractive index" of the solvent, "TRANSPARENT" is selected as the "transparency", and "non-spherical" is selected as the "spherical particle". Selected. Perform the "Set Zero" operation prior to sample measurement. The "Set Zero" operation is an operation for subtracting the influence of disturbance elements (glass, dirt on the glass wall surface, glass unevenness, etc.) other than the scattered light from the particles on the subsequent measurement, and is performed by using a dispersion solvent in the sample supply section. A background measurement is performed in a state where only a certain amount of water is put in and only water, which is a dispersion solvent, is circulated in the wet cell, and the background data is stored in the computer. Then, perform the "Sample LD (Sample Loading)" operation. The Sample LD operation is an operation for optimizing the sample concentration in the dispersion liquid that is circulated and supplied to the wet cell at the time of measurement, and manually reaches the optimum amount of the sample to be measured in the sample supply unit according to the instruction of the measurement control software. It is an operation to put in. Then, the measurement operation is performed by pressing the "measurement" button. The measurement operation is repeated twice, and the measurement result is output from the control computer as the average value. The measurement results are based on the particle size distribution histogram and the respective values of D10, D50 and D90 (D10, D50 and D90 have particle sizes of 10%, 50% and 90%, respectively, in the particle size distribution of the secondary particles). To be acquired. The measured D50 was 10 μm.

(Manufacturing and evaluation of lithium secondary batteries)
Using the lithium transition metal composite oxides according to Examples 1 to 11 and Comparative Examples 1 to 13 as positive electrode active materials for lithium secondary batteries, lithium secondary batteries were prepared by the following procedure, and the battery characteristics were evaluated. ..

Using N-methylpyrrolidone as a dispersion medium, a coating paste in which the active material, acetylene black (AB) and polyvinylidene fluoride (PVdF) were kneaded and dispersed at a mass ratio of 90: 5: 5 was prepared. The coating paste was applied to one surface of an aluminum foil current collector having a thickness of 20 μm to prepare a positive electrode plate. The mass and coating thickness of the active material applied per fixed area were unified so that the test conditions would be the same for the lithium secondary batteries according to all the examples and comparative examples.

For the purpose of accurately observing the single behavior of the positive electrode, metallic lithium was used in close contact with the nickel foil current collector for the counter electrode, that is, the negative electrode. Here, a sufficient amount of metallic lithium was arranged on the negative electrode so that the capacity of the lithium secondary battery was not limited by the negative electrode.

_{As the electrolytic solution, LiPF 6} was dissolved in a mixed solvent having an ethylene carbonate (EC) / ethyl methyl carbonate (EMC) / dimethyl carbonate (DMC) volume ratio of 6: 7: 7 so as to have a concentration of 1 mol / l. The solution was used. As a separator, a polypropylene microporous membrane surface-modified with polyacrylate was used. For the exterior body, a metal resin composite film made of polyethylene terephthalate (15 μm) / aluminum foil (50 μm) / metal adhesive polypropylene film (50 μm) is used, and electrodes are used so that the open ends of the positive electrode terminal and the negative electrode terminal are exposed to the outside. Was sealed, and the fusion allowance in which the inner surfaces of the metal resin composite film faced each other was hermetically sealed except for the portion to be the liquid injection hole. After the electrolytic solution was injected, the liquid injection hole was sealed.

The lithium secondary battery produced by the above procedure was subjected to an initial charge / discharge step at 25 ° C. Charging was a constant current constant voltage charging with a current of 0.1 CmA and a voltage of 4.6 V, and the charging termination condition was the time when the current value was attenuated to 1/6. The discharge was a constant current discharge with a current of 0.1 CmA and a final voltage of 2.0 V. This charge / discharge was performed for 2 cycles. Here, a pause process of 30 minutes was provided after charging and after discharging.

(Measurement of half width)
The half-value width of the lithium transition metal composite oxide according to Examples 1 to 11 and Comparative Examples 1 to 13 was measured using an X-ray diffractometer (manufactured by Rigaku, model name: MiniFlex II). In the specification of the present application, the full width at half maximum shall be measured according to the following conditions and procedures.
The radiation source is CuKα, and the acceleration voltage and current are 30 kV and 15 mA, respectively. The sampling width is 0.01 deg, the scanning time is 14 minutes (scan speed is 5.0), the divergent slit width is 0.625 deg, the light receiving slit width is open, and the scattering slit is 8.0 mm. The obtained X-ray diffraction data is indexed on the (003) plane in the space group R3-m by using "PDXL", which is an accessory software of the X-ray diffractometer, without removing the peak derived from Kα2. Half-value width F (003) for the diffraction peak existing at 2θ = 18.6 ° ± 1 ° on the X-ray diffraction diagram, and 2θ = 44 ± 1 ° on the X-ray diffraction diagram indexed on the (104) plane. The half-value width F (104) is determined for the existing diffraction peak.
The charge-end / discharge-end ratio of F (003) / F (104) was determined as follows. The battery that has undergone the above initial charge / discharge process is charged with a constant current at a current of 0.1 CmA with a charging voltage of 4.45 V, and is charged with a constant voltage until the current value decreases to 0.01 CmA. bottom. Further, another battery that has undergone the above initial charge / discharge process is charged at a constant current of 0.1 CmA with a charging voltage of 4.45 V, and then charged at 0.1 CmA with a 30-minute pause. A constant current discharge was performed up to 0.0 V, and the state was set to the end of discharge state. These batteries were disassembled, the positive electrode plates taken out were thoroughly washed with dimethyl carbonate, dried at room temperature for a whole day and night, the mixture was taken out from the electrodes, and the aggregated powder was loosened using an agate mortar. The obtained mixture powder was subjected to the above-mentioned X-ray measurement. Half-price width ratio F (003) / F (104), which is the ratio of half-price width F (003) and half-price width F (104) obtained from the X-ray diffraction pattern obtained for the mixture powder collected from the battery in the end-charged state. ) Is divided by the value of the half-value width ratio F (003) / F (104) obtained from the X-ray diffraction pattern obtained for the mixture powder collected from the battery in the end-discharged state, and the value is F (003). The ratio of charge end / discharge end of / F (104) was used.
Moreover, it was confirmed that the lithium transition metal composite oxides of all the examples and comparative examples had a hexagonal structure.
In the present specification, the electrodes shall be adjusted to the end-of-discharge state and the end-of-charge state according to the above procedure. However, in the above embodiment, the battery using the metal lithium electrode as the negative electrode is put into a discharge end state or a charge end state, and then the battery is disassembled and the electrode is taken out. However, after the battery is disassembled and the electrode is taken out, the metal is used. After assembling the battery with the lithium electrode as the counter electrode, it may be adjusted to the end-discharge state and the end-charge state according to the above procedure.

(Charge / discharge cycle test)
Subsequently, a 30-cycle charge / discharge cycle test was performed. Charging was a constant current constant voltage charge with a current of 1 CmA and a voltage of 4.45 V, and the charge termination condition was the time when the current value was attenuated to 1/6. The discharge was a constant current discharge with a current of 1 CmA and a final voltage of 2.0 V. Here, a rest process of 10 minutes was provided after charging and after discharging.

(Initial discharge capacity and capacity retention rate)
The discharge capacity of the first cycle in the charge / discharge cycle test was recorded as "initial discharge capacity (mAh)". Further, the percentage of the discharge capacity at the 30th cycle with respect to the "initial discharge capacity (mAh)" was calculated and used as the "capacity maintenance rate (%)".

Charge / discharge end ratio of F (003) / F (104) of lithium transition metal composite oxide according to Examples 1 to 11 and Comparative Examples 1 to 13, composition of outermost surface in core and surface layer, production method, Table 1 shows the test results of a lithium secondary battery using each of the above lithium transition metal composite oxides as a positive electrode active material.

From Table 1, it has a core and a surface layer, and the molar ratio Ni / Me of Ni in the transition metal (Me) in the core is 0.4 ≦ Ni / Me ≦ 0.8, and the transition of the outermost surface in the surface layer. The molar ratio Ni / Me in the metal (Me) is 0.1 ≦ Ni / Me ≦ 0.4, and the charge-end / discharge-end ratio of F (003) / F (104) is 0.9 to 1.1. It can be seen that the lithium secondary batteries of Examples 1 to 11 in which the lithium transition metal composite oxide between the two is used as the positive electrode active material have a high discharge capacity and a large capacity retention rate.

Comparative Examples 1 and 2 are conventional production conditions in which the Mn ratio of the undiluted solution 1 is large and the Mn ratio of the undiluted solution 2 is small, and therefore the uniformity of Mn at the atomic level is high. ) / F (104) and F (003) / F (104) in the end-of-discharge state (degree of change in the anisotropic strain of the crystal) has a large deviation from 1 (less than 0.9), and the discharge capacity. Is low.
On the other hand, in Comparative Examples 3 and 4, since the Mn ratio of the undiluted solution 1 is small and the Mn ratio of the undiluted solution 2 is large, the manufacturing conditions are such that the uniformity of Mn at the atomic level is considerably disturbed. The ratio of F (003) / F (104) to F (003) / F (104) in the end-of-discharge state (degree of change in the anisotropic strain of the crystal) also has a large deviation from 1 (1. 1), the discharge capacity becomes low.
On the other hand, when the precursor of the core is prepared as in Examples 1 to 11, by controlling the ratio of Mn of the stock solution 1 and the stock solution 2, the uniformity of Mn at the atomic level is disturbed. Is appropriate, and the ratio of F (003) / F (104) in the end-of-charge state to F (003) / F (104) in the end-of-discharge state (degree of change in the anisotropic strain of the crystal) is 0.9. It is estimated that the discharge capacity will increase between ~ 1.1.

Comparative Examples 5 and 6 have a core Ni / Me molar ratio of less than 0.4 and a low discharge capacity, and Comparative Examples 7 and 8 have a core Ni / Me molar ratio of more than 0.8 and a discharge capacity. Is high, but the capacity retention rate is small.
Further, in Comparative Examples 9 to 11, the Ni / Me molar ratio on the outermost surface in the surface layer was more than 0.4, and in Comparative Examples 12 and 13, it was less than 0.1. The capacity retention rate is small.
On the other hand, as in Examples 1 to 11, the Ni / Me molar ratio of the core is 0.4 to 0.8, and the Ni / Me molar ratio of the outermost surface in the surface layer is 0.1 to 0.4. By using the lithium transition metal composite oxide as the positive electrode active material, the discharge capacity is increased and the capacity retention rate is also increased.

(Explanation of code)
1 Lithium secondary battery 2 Electrode group 3 Battery container 4 Positive terminal 4'Positive lead 5 Negative terminal 5'Negative lead 20 Power storage unit 30 Power storage device

By using the positive electrode active material containing the novel lithium transition metal composite oxide of the present invention, it is possible to provide a lithium secondary battery having a large discharge capacity and excellent charge / discharge cycle performance. Therefore, this lithium secondary battery Is useful as a lithium secondary battery for hybrid vehicles and electric vehicles.

Claims (6)

A positive electrode active material for a lithium secondary battery in which the transition metal (Me) contains Ni, Co and Mn and contains a lithium transition metal composite oxide having a hexagonal structure.
The lithium transition metal composite oxide is divided into 10 equal parts with the center of the particle cross section as Point 0 and the outermost surface of the particle as Point 10, and Point 0 to Point 9 are the cores and Point 9 from the center of the particle cross section toward the outermost surface. When the molar concentrations of Ni, Co, and Mn are averaged with Point 10 as the surface layer,
The molar ratio of Ni in the transition metal (Me) in the surface layer, Ni / Me, is smaller than the molar ratio of Ni in the transition metal (Me) in the core, Ni / Me.
The molar ratio of Ni in the transition metal (Me) in the core, Ni / Me, is 0.4 ≦ Ni / Me ≦ 0.8.
The molar ratio Ni / Me of Ni in the transition metal (Me) on the outermost surface of the surface layer is 0.1 ≦ Ni / Me ≦ 0.4.
The molar ratio of Mn in the transition metal (Me) in the surface layer, Mn / Me, is larger than the molar ratio of Mn in the transition metal (Me) in the core, Mn / Me.
Potential 4.45V (vs.Li/Li ⁺⁾ half-width ratio F in (003) / F (104) a potential 2.0V half-width ratio F in ^{(vs.Li/Li +) (003) /} F (104 A positive electrode active material for a lithium secondary battery, wherein the value divided by) is between 0.9 and 1.1. And wherein the Mn / Me before SL core is 0.1 ≦ Mn / Me ≦ 0.4, Mn / Me in the outermost surface of the surface layer is 0.4 ≦ Mn / Me ≦ 0.8 The positive electrode active material for a lithium secondary battery according to claim 1. The method for producing a positive electrode active material for a lithium secondary battery according to claim 1 or 2.
In the step of Ni in solution, thereby coprecipitating a compound containing Co and Mn to prepare a precursor of a transition metal composite oxide contains a compound of the solution and Mn containing a compound of the N i, Co and Mn The solution and the solution are dropped separately at the same time to prepare a precursor of a core of a transition metal composite oxide in which the molar ratio of Ni in the transition metal (Me) Ni / Me is 0.4 ≦ Ni / Me ≦ 0.8. After that
A solution containing a compound of Ni, Co and Mn is dropped, and the molar ratio Ni / Me of Ni in the transition metal (Me) is smaller than the molar ratio Ni / Me of Ni in the core, and the transition metal on the outermost surface. molar ratio Ni / Me of Ni in (Me) is Ri 0.1 ≦ Ni / Me ≦ 0.4 der, the molar ratio Mn / Me of Mn in the transition metal (Me) in the precursor of said surface layer is The positive activity for a lithium secondary battery, which comprises producing a precursor of a surface layer of a transition metal composite oxide having a molar ratio of Mn in the transition metal (Me) in the precursor of the core larger than Mn / Me. Method of manufacturing a substance. Before SL Mn / Me in the precursor of the core is 0.1 ≦ Mn / Me ≦ 0.4, Mn / Me of the outermost surface in the precursor of said surface layer is 0.4 ≦ Mn / Me ≦ 0.8 The method for producing a positive electrode active material for a lithium secondary battery according to claim 3, wherein the positive electrode active material for a lithium secondary battery is produced. An electrode for a lithium secondary battery containing the positive electrode active material for the lithium secondary battery according to claim 1 or 2. A lithium secondary battery provided with the electrode for a lithium secondary battery according to claim 5.

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