WO2020059471A1 - Positive electrode active material for secondary battery, and method for producing same - Google Patents

Abstract

The purpose of the present invention is to provide: a positive electrode active material for a secondary battery that can exhibit excellent cycle characteristics under both ambient temperature and high temperature environments; and a method for producing the positive electrode active material. The positive electrode active material for a secondary battery has a layered structure containing at least nickel, cobalt, and manganese, which are single-crystal particles and/or secondary particles that are aggregates of a plurality of primary particles, wherein the average particle strength of particles having a particle size of (D50)±1.0 μm is at least 200 MPa, and 0.97≤β/α≤1.25, where (D50) is a particle size at a cumulative volume percentage of 50 vol%, α is the full width at half maximum of the lower angle peak among two diffraction peaks appearing in the range of 2θ=64.5±1^о in the X-ray diffraction pattern, and β is the full width at half maximum of the higher angle peak among the two diffraction peaks.

Description

Positive electrode active material for secondary battery and method for producing the same

The present invention relates to a positive electrode active material for a secondary battery and a method for producing the same, and more particularly, to a positive electrode active material for a secondary battery capable of exhibiting excellent cycle characteristics under any environment of ordinary temperature and high temperature, and a method for producing the same. .

In recent years, secondary batteries have been used in a wide variety of fields, such as mobile devices and vehicles that use or use electricity as a power source. As the positive electrode active material of the secondary battery, for example, a lithium metal composite oxide powder containing nickel, cobalt, and manganese is used.

近年 In recent years, secondary batteries are required to be able to exhibit a high output stably in response to environmental changes such as ambient temperature. Therefore, the positive electrode active material for a secondary battery is required to have a stable and excellent cycle characteristic even when the environment such as the ambient temperature fluctuates.

Therefore, for example, in order to stably obtain a satisfactory manner cycle characteristics under high temperature conditions, a formula _{Li a Ni x Co y Mn z} MbO 2, 1.0 ≦ a ≦ 1.2,0.30 ≦ A lithium-nickel-cobalt-manganese composite oxide positive electrode material having a spherical or spheroidal layer structure in which x ≦ 0.90, 0.05 ≦ y ≦ 0.40, 0.05 ≦ z ≦ 0.50, and x + y + z = 1 has been proposed. (Patent Document 1). Further, the lithium nickel cobalt manganese composite oxide cathode material of Patent Document 1 contains primary single crystal particles and a small amount of secondary aggregated particles, and the primary single crystal particles have a particle size of 0.5 to 10 μm and a particle size of 5 μm or less. The particle size is controlled so that the cumulative% of the particles exceeds 60%.

However, in Patent Document 1, although excellent cycle characteristics can be obtained under a slightly high temperature condition, there is room for improvement in obtaining excellent cycle characteristics over a temperature range from room temperature to high temperature. As described above, the conventional positive electrode active material for a secondary battery discloses improvement in cycle characteristics under a predetermined temperature condition.

On the other hand, the usage environment of the secondary battery may fluctuate depending on the usage conditions and installation environment of the equipment to be mounted, such as the ambient temperature. Therefore, there is a need for a positive electrode active material for a secondary battery that can stably exhibit excellent cycle characteristics even when the use environment such as the ambient temperature fluctuates.

JP 2018-045998 A

In view of the above circumstances, an object of the present invention is to provide a positive electrode active material for a secondary battery that can exhibit excellent cycle characteristics under both normal temperature and high temperature environments, and a method for producing the same.

An embodiment of the present invention provides a positive electrode active material for a secondary battery having a layered structure including at least one of nickel, cobalt, and manganese, which is a secondary particle that is an aggregate of single crystal particles and / or a plurality of primary particles. Substance
The average particle strength of the particles having a cumulative volume percentage of 50% by volume and having a particle diameter (D50) ± 1.0 μm is 200 MPa or more;
In a powder X-ray diffraction measurement using CuKα ray, the full width at half maximum of the peak on the low angle side of two diffraction peaks appearing in the range of 2θ = 64.5 ± 1 ° is α, and the full width at half maximum of the peak on the high angle side is β. Is a positive electrode active material for a secondary battery in which β / α satisfies 0.97 ≦ β / α ≦ 1.25.

In the present specification, the average particle strength of the positive electrode active material for a secondary battery refers to the positive electrode active material particles for a secondary battery arbitrarily selected from a particle diameter (D50) ± 1.0 μm having a cumulative volume percentage of 50% by volume. For one piece, the particle strength (MPa) = 2.8 × the weight at the time of crushing (N) / (π, based on the value of the weight at the time of crushing (N) measured by Shimadzu Micro Compression Testing Machine MCT-510. X particle diameter (mm) x particle diameter (mm)), this operation is performed for 10 particles, and the average particle intensity is calculated from each particle intensity of 10 particles.

An embodiment of the present invention provides a positive electrode active material for a secondary battery having a layered structure including at least one of nickel, cobalt, and manganese, which is a secondary particle that is an aggregate of single crystal particles and / or a plurality of primary particles. Substance
The average particle strength of the particles having a cumulative volume percentage of 50% by volume and having a particle diameter (D50) ± 1.0 μm is 200 MPa or more;
In the X-ray diffraction measurement of the positive electrode before and after the cycle test using CuKα rays, the rate of change of the lattice constant before and after the cycle test was calculated as (a axis before the cycle test / a axis after the cycle test) × 100 = A, (cycle When c axis before test / c axis after cycle test) × 100 = C,
A positive electrode active material for a secondary battery in which at least one of A and C in a cycle test at 25 ° C. and 60 ° C. is 99.30% or more and 100.90% or less.

The “cycle test” means that a laminate cell is prepared using a positive electrode active material for a secondary battery, charged at 4.2 V / CC, 2 C, discharged at 3.0 V / CC, 2 C at 25 ° C., 1000 cycles, 60 cycles. A charge / discharge test at 500 ° C. cycles.

An embodiment of the present invention provides the following general formula (1)
Li [Li _a (M1 _x M2 _y ) _1-a ] O _{2 + b} (1)
(Where 0 ≦ a ≦ 0.30, −0.30 ≦ b ≦ 0.30, 0.9 ≦ x ≦ 1.0, 0 ≦ y ≦ 0.1, x + y = 1, M1 is At least one metal element of Ni, Co and Mn, M2 is Fe, Cu, Ti, Mg, Al, W, Zn, Sn, Zr, Ga, V, B, Mo, As, Ge, P , Pb, Si, Sb, Nb, Ta, Re, and Bi, which means at least one metal element selected from the group consisting of).

態 様 An embodiment of the present invention is an active material for a secondary battery in which the cumulative volume percentage is 50% by volume and the particle diameter D50 is 2.0 μm or more and 20.0 μm or less.

An embodiment of the present invention is an active material for a secondary battery having a BET specific surface area of 0.1 m ² / g or more and 5.0 m ² / g or less.

態 様 An embodiment of the present invention is a secondary battery including the above-described positive electrode active material for a secondary battery.

An aspect of the present invention is to provide a composite hydroxide particle containing at least one of nickel (Ni), cobalt (Co) and manganese (Mn) with a lithium (Li) compound and at least one of Ni, Co and Mn. A step of adding a mixture of lithium compound and composite hydroxide particles by adding at least an atomic ratio of 1.00 ≦ Li / M1 ≦ 1.30 to a metal element (M1) composed of at least one kind of metal element (M1);
The mixture is represented by the following formula p ≧ −600q + 1603 (where q is an atomic ratio of Li to the total of at least one metal element (M1) of Ni, Co and Mn (Li / M1); 1.00 ≦ q ≦ 1.30, p is a main firing temperature, and means a firing temperature represented by 940 ° C. <p ≦ 1100 ° C.).
In addition to the main sintering step, the following (1) to (3) steps (1) a calcination step performed before the main sintering step, wherein the sintering temperature is 300 ° C. or more and 800 ° C. or less;
(2) a tempering step performed after the main firing step, wherein the firing temperature is 600 ° C. or more and 900 ° C. or less;
(3) Before the main firing step and / or the tempering step, M2 (M2 is Fe, Cu, Ti, Mg, Al, W, Zn, Sn, Zr, Ga, V, B, Mo, As, Ge , P, Pb, Si, Sb, Nb, Ta, Re, and Bi, which means at least one metal element selected from the group consisting of:
A method for producing a positive electrode active material for a secondary battery, the method including at least one step of the above.

In an embodiment of the present invention, before the mixing step of the lithium compound and the composite hydroxide particles, the particle size distribution width of the composite hydroxide particles is set to 0.40 ≦ (D90−D10) /D50≦1.00. This is a method for producing a positive electrode active material for a secondary battery including a step.

According to an embodiment of the present invention, in the main firing step, a ratio of a surface area (S) of the mixture including a contact surface with the sheath to a volume (V) of the mixture when the mixture is filled in a sheath is as follows: This is a method for producing a positive electrode active material for a secondary battery in which 0.08 ≦ S / V ≦ 2.00.

According to the aspect of the present invention, the particles having a cumulative volume percentage of 50% by volume and having a particle diameter (D50) ± 1.0 μm have an average particle strength of 200 MPa or more, and the powder X-ray diffraction pattern using CuKα rays When the full width at half maximum of the diffraction peak on the low angle side of two diffraction peaks appearing in the range of 2θ = 64.5 ± 1 ° is α, and the full width at half maximum of the diffraction peak on the high angle side is β, β / α is By satisfying 0.97 ≦ β / α ≦ 1.25, it is possible to obtain a positive electrode active material for a secondary battery that can exhibit excellent cycle characteristics under both normal temperature and high temperature environments.

According to the aspect of the present invention, the average particle strength of particles having a particle diameter (D50) of ± 1.0 μm having a cumulative volume percentage of 50% by volume is 200 MPa or more, and X in a cycle test of a positive electrode using CuKα radiation. In the line diffraction pattern, the change rate of the lattice constant before and after the cycle test is represented by (a axis before the cycle test / a axis after the cycle test) × 100 = A, (c axis before the cycle test / c axis after the cycle test) ) × 100 = C, at least one of A and C is 99.30% or more and 100.90% or less in a cycle test at 25 ° C. and 60 ° C., so that it can be used in both normal temperature and high temperature environments. However, a positive electrode active material for a secondary battery that can exhibit excellent cycle characteristics can be obtained.

According to an embodiment of the present invention, a mixture of a lithium compound and composite hydroxide particles having an atomic ratio of 1.00 ≦ Li / M1 ≦ 1.30 is subjected to main firing to obtain p ≧ −600q + 1603 (where q is , At least the atomic ratio (Li / M1) of Li to the total of the metal elements (M1) composed of at least one of Ni, Co and Mn, where 1.00 ≦ q ≦ 1.30, and p is the firing temperature. 940 ° C. <p ≦ 1100 ° C.) to produce a positive electrode active material for a secondary battery capable of exhibiting excellent cycle characteristics under both normal temperature and high temperature environments by firing at a firing temperature of 940 ° C. <p ≦ 1100 ° C. Can be.

3 is an image of a positive electrode active material for a secondary battery of the present invention, taken by a scanning electron microscope (SEM). FIGS. 1A and 1B are schematic diagrams schematically illustrating an example of a lithium secondary battery.

(4) Hereinafter, the positive electrode active material for a secondary battery of the present invention will be described in detail. The positive electrode active material for a secondary battery of the present invention is a secondary particle formed by agglomeration of single crystal particles and / or a plurality of primary particles, and has a layered structure containing at least one of nickel, cobalt, and manganese. Having. The shape of the positive electrode active material for a secondary battery of the present invention is not particularly limited, and has various shapes. Examples thereof include a substantially spherical shape, a substantially cubic shape, and a substantially rectangular parallelepiped shape.

The positive electrode active material for a secondary battery of the present invention includes one of single crystal particles and secondary particles formed by aggregating a plurality of primary particles, or both single crystal particles and secondary particles. FIG. 1, which is a scanning electron microscope (SEM) image of the positive electrode active material for a secondary battery of the present invention, contains both single crystal particles and secondary particles. As shown in FIG. 1, single crystal particles are in the form of primary particles, and secondary particles are particles formed by aggregating a plurality of primary particles.

結晶 The crystal structure of the positive electrode active material for a secondary battery of the present invention is a layered structure, and more preferably a hexagonal crystal structure or a monoclinic crystal structure.

The hexagonal crystal structure is P3, P31, P32, R3, P-3, R-3, P312, P321, P3112, P3121, P3212, P3221, R32, P3m1, P31m, P3c1, P31c, R3m, R3c, P-31m, P-31c, P-3m1, P-3c1, R-3m, R-3c, P6, P61, P65, P62, P64, P63, P-6, P6 / m, P63 / m, P622, From P6122, P6522, P6222, P6422, P6322, P6mm, P6cc, P63cm, P63mc, P-6m2, P-6c2, P-62m, P-62c, P6 / mmm, P6 / mcc, P63 / mcm, P63 / mmc It belongs to any one space group selected from the group consisting of:

The monoclinic crystal structure is composed of P2, P21, C2, Pm, Pc, Cm, Cc, P2 / m, P21 / m, C2 / m, P2 / c, P21 / c, and C2 / c. It belongs to any one space group selected from the group.

Among these, in order to obtain a secondary battery having a high discharge capacity, the crystal structure is a hexagonal crystal structure belonging to the space group R-3m or a monoclinic crystal structure belonging to C2 / m. Particularly preferred is a structure.

The cumulative volume percentage of the positive electrode active material for a secondary battery of the present invention is in the range of a particle diameter (D50) of 50% by volume (hereinafter sometimes simply referred to as “D50”) ± 1.0 μm, that is, (D50) − The average particle strength of the particles in the range of 1.0 μm to (D50) +1.0 μm is 200 MPa or more. This excellent average particle strength is considered to be due to the fact that the positive electrode active material for a secondary battery of the present invention contains single crystal particles. (D50) The average particle strength of ± 1.0 µm is not particularly limited as long as it is 200 MPa or more, but the lower limit is 230 MPa from the viewpoint of exhibiting more excellent cycle characteristics under both normal temperature and high temperature environments. Preferably, 250 MPa is more preferable, and 310 MPa is particularly preferable. On the other hand, the upper limit of the average particle strength of (D50) ± 1.0 μm is not particularly limited, but, for example, is preferably 3000 MPa, more preferably 2200 MPa, and still more preferably 1000 MPa from the viewpoint of efficient production. 700 MPa is particularly preferred. The above lower limit and upper limit can be arbitrarily combined.

下限 The lower limit of D50 of the positive electrode active material for a secondary battery of the present invention is not particularly limited, but is preferably 2.0 µm, more preferably 2.5 µm, and particularly preferably 3.0 µm from the viewpoint of improving the handling properties. On the other hand, the upper limit of D50 of the positive electrode active material for a secondary battery is preferably 20.0 μm, particularly preferably 15.0 μm, from the viewpoint of improving the density and ensuring a contact surface with the electrolytic solution. The above lower limit and upper limit can be arbitrarily combined.

In the positive electrode active material for a secondary battery of the present invention, in a powder X-ray diffraction measurement using CuKα radiation, the full width at half maximum of the diffraction peak on the low angle side of two diffraction peaks appearing in the range of 2θ = 64.5 ± 1 °. Is α and β is the full width at half maximum of the diffraction peak on the high angle side, β / α is the configuration of the full width at half maximum of the diffraction peak in which 0.97 ≦ β / α ≦ 1.25, or CuKα ray was used. In the X-ray diffraction pattern of the positive electrode, the rate of change of the lattice constant before and after the cycle test is (a axis before the cycle test / a axis after the cycle test) × 100 = A, (c axis before the cycle test / after the cycle test) (C-axis) × 100 = C, the rate of change of the lattice constant where at least one of A and C is 99.30% or more and 100.90% or less in the cycle test at 25 ° C. and 60 ° C. Or have at least one configuration

Regarding the full width at half maximum of the powder diffraction peak using CuKα ray By having the above range of the average particle intensity of D50 ± 1.0 μm and the full width at half maximum of the diffraction peak of 0.97 ≦ β / α ≦ 1.25 at room temperature Thus, a positive electrode active material for a secondary battery that can exhibit excellent cycle characteristics under any environment at high temperatures can be obtained. That is, the inventor of the present invention has found that, when the full width at half maximum of the diffraction peak satisfies the relationship of 0.97 ≦ β / α ≦ 1.25, it contributes to imparting excellent cycle characteristics under both normal temperature and high temperature environments. Found them.

The value of β / α is not particularly limited as long as it is 0.97 or more and 1.25 or less, but from the viewpoint of obtaining more excellent cycle characteristics stably at both normal temperature and high temperature, from 1.00 to 1.25. The following is more preferable, and the range of 1.03 to 1.13 is particularly preferable.

Regarding the rate of change of the lattice constant In the range of the average particle strength in the range of (D50) ± 1.0 μm and the cycle test at 25 ° C. and 60 ° C., at least one of A and C is 99.30% or more. By having a lattice constant change rate of 100.90% or less, it is possible to obtain a positive electrode active material for a secondary battery that can exhibit excellent cycle characteristics under both normal temperature and high temperature environments. That is, in the 25 ° C. cycle test (normal temperature cycle test) and the 60 ° C. cycle test (high temperature cycle test), the rate of change of at least one of the a-axis and c-axis lattice constants is 99.30% or more and 100. The inventors of the present invention have found that the control at 90% or less contributes to imparting excellent cycle characteristics under both normal temperature and high temperature environments. This is considered to be due to the fact that the change in the crystal structure of the positive electrode active material for the secondary battery before and after the cycle test was reduced in the normal temperature and high temperature cycle tests.

In the cycle test at 25 ° C. and 60 ° C., there is no particular limitation so long as at least one of A and C is 99.30% or more and 100.90% or less. From the viewpoint of obtaining excellent cycle characteristics, both A and C are preferably from 99.30% to 100.90%, and both A and C are particularly preferably from 99.32% to 100.90%.

The composition of the positive electrode active material for a secondary battery of the present invention is not particularly limited as long as the composition contains at least one metal element of nickel, cobalt, and manganese. For example, the following general formula (1)
Li [Li _a (M1 _x M2 _y ) _1-a ] O _{2 + b} (1)
(In the formula, a is preferably 0 ≦ a ≦ 0.30, more preferably 0 ≦ a ≦ 0.20, and particularly preferably 0 ≦ a ≦ 0.10. B is not particularly limited. 30 ≦ b ≦ 0.30 is preferable, −0.20 ≦ b ≦ 0.20 is more preferable, 0 ≦ b ≦ 0.20 is particularly preferable, x is 0.9 ≦ x ≦ 1.0, and y is 0 ≤ y ≤ 0.10, more preferably 0 ≤ y ≤ 0.05, particularly preferably 0 ≤ y ≤ 0.02, x + y = 1. M1 is 1 of Ni, Co and Mn. The composition of Ni, Co and Mn is not particularly limited, but the Ni composition range is preferably from 10 mol% to 90 mol%, more preferably from 30 mol% to 80 mol%, and more preferably 50 mol% or more. The content of Co is particularly preferably 60 mol% or less. Is preferably from 10 mol% to 50 mol%, more preferably from 10 mol% to 30 mol%, and the Mn composition range is preferably from 0 mol% to 50 mol%, more preferably from 0 mol% to 40 mol%, and M2 is Fe. , Cu, Ti, Mg, Al, W, Zn, Sn, Zr, Ga, V, B, Mo, As, Ge, P, Pb, Si, Sb, Nb, Ta, Re and Bi. And at least one type of metal element). Among them, by including M2 which is an arbitrary metal element, more excellent cycle characteristics can be obtained stably at both normal temperature and high temperature environments. Among these arbitrary metal elements, Zr and Al are preferable.

正極 The positive electrode active material for a secondary battery of the present invention can be used, for example, as a positive electrode active material for a lithium ion secondary battery.

Although the BET specific surface area of the positive electrode active material for a secondary battery of the present invention is not particularly limited, for example, the lower limit is 0.10 m ² from the viewpoint of improving density and ensuring a contact surface with an electrolyte. / G is preferred, and 0.30 m ² / g is particularly preferred. On the other hand, the upper limit is preferably 5.0 m ² / g, more preferably 4.0 m ² / g, particularly preferably 2.0 m ² / g. The above lower limit and upper limit can be arbitrarily combined.

Next, an example of a method for producing the positive electrode active material for a secondary battery of the present invention will be described.

As the above-mentioned production method, for example, first, composite hydroxide particles having at least one of nickel, cobalt, and manganese (hereinafter, sometimes simply referred to as “composite hydroxide particles”) are prepared. The composite hydroxide particles are a precursor of a positive electrode active material for a secondary battery. The precursor used in the present invention may be a composite oxide having at least one of nickel, cobalt and manganese. The method for preparing the composite hydroxide particles is as follows. First, a nickel salt solution (for example, a sulfate solution), a cobalt salt solution (for example, a sulfate solution) and a manganese salt solution (for example, a sulfate solution) are formed by a coprecipitation method. Solution), a complexing agent, a complexing agent and a pH adjusting agent are appropriately added to react in a reaction vessel to prepare composite hydroxide particles, A slurry suspension containing the particles is obtained. As a solvent for the suspension, for example, water is used.

The complexing agent to be added to the metal salt solution is not particularly limited as long as it can form a complex with nickel, cobalt, and manganese ions in an aqueous solution. For example, an ammonium ion donor (ammonium sulfate, chloride, etc.) Ammonium, ammonium carbonate, ammonium fluoride, etc.), hydrazine, ethylenediaminetetraacetic acid, nitrilotriacetic acid, uracil diacetate, and glycine. At the time of precipitation, an alkali metal hydroxide (for example, sodium hydroxide or potassium hydroxide) may be added as needed to adjust the pH value of the aqueous solution.

When the pH adjusting agent and the complexing agent are appropriately and continuously supplied to the reaction tank in addition to the metal salt solution, the metals (one or more of nickel, cobalt, and manganese) of the metal salt solution undergo a coprecipitation reaction, Composite hydroxide particles are prepared. At the time of the coprecipitation reaction, the temperature of the reaction vessel is controlled, for example, in the range of 10 ° C. to 80 ° C., preferably 20 to 70 ° C., and the pH value in the reaction vessel is adjusted to a pH of 9 ° C. The substance in the reaction vessel is appropriately stirred while controlling the pH within a range of from pH 13 to preferably pH 11 to 13. Examples of the reaction tank include a continuous type in which the formed composite hydroxide particles overflow to separate them, and a batch type in which the composite hydroxide particles are not discharged out of the system until the end of the reaction.

ろ 過 The composite oxide particles obtained as described above are filtered from the suspension, washed with water, and heat-treated to obtain powdery composite hydroxide particles. If necessary, a step of narrowing (D90-D10) / D50 of the particle size distribution width of the obtained composite hydroxide particles may be added by, for example, a dry classifier.

The lower limit of D50 of the composite hydroxide particles that are the precursor of the positive electrode active material for a secondary battery of the present invention is not particularly limited, but is preferably 2.0 μm, more preferably 2.5 μm, from the viewpoint of improving handling properties. And 3.0 μm are particularly preferred. On the other hand, the upper limit of D50 of the composite hydroxide particles is preferably 25.0 μm, particularly preferably 20.0 μm, from the viewpoint of enhancing the reaction with the lithium compound during firing. The above lower limit and upper limit can be arbitrarily combined.

The particle size distribution of the composite hydroxide particles is not particularly limited, but the lower limit of the value of (D90−D10) / D50 is preferably 0.40, and more preferably 0.50, from the viewpoint of an efficient production range. Is more preferable, and 0.70 is particularly preferable. On the other hand, the upper limit of the value of (D90−D10) / D50 of the composite hydroxide particles is set at 1 because the superior cycle characteristics can be obtained under a normal temperature environment and the superior cycle characteristics can be obtained under a high temperature environment. 0.000 is more preferable, 0.96 is more preferable, and 0.80 is particularly preferable from the viewpoint of obtaining further excellent cycle characteristics under a normal temperature environment. The above lower limit and upper limit can be arbitrarily combined.

Next, a lithium compound is added to the obtained powdery composite hydroxide particles to prepare a mixture of the composite hydroxide particles and the lithium compound. At this time, the lithium compound is added so that the atomic ratio satisfies 1.00 ≦ Li / M1 ≦ 1.30. The lithium compound is not particularly limited as long as it is a compound having lithium, and examples thereof include lithium carbonate and lithium hydroxide.

Next, the obtained mixture is fired (hereinafter, sometimes referred to as main firing) at a firing temperature represented by the following formula. In the main firing, the formula p ≧ −600q + 1603 (where q is the atomic ratio of Li to the total of at least one metal element (M1) of Ni, Co and Mn) (Li / M1). 00 ≦ q ≦ 1.30, p is a main firing temperature, and means firing at a firing temperature represented by 940 ° C. <p ≦ 1100 ° C.). The firing time in the firing step at the above firing temperature is not particularly limited, but is, for example, preferably 5 to 20 hours, and particularly preferably 8 to 15 hours. The rate of temperature rise in the main firing is preferably 50 to 550 ° C./h, more preferably 100 to 400 ° C./h, and 140 ° C. to 380 ° C./h from the viewpoint of keeping the material temperature and the temperature of the firing furnace equal. Is particularly preferred. The atmosphere for the main firing is not particularly limited, and examples thereof include air and oxygen. The firing furnace used for the main firing is not particularly limited, and examples thereof include a stationary box furnace and a roller hearth continuous furnace. In the method for producing a positive electrode active material for a secondary battery according to the present invention, in addition to the main firing step, a calcining step before the main firing step, a tempering step after the main firing step, a main firing step, and / or Before the tempering step, Fe, Cu, Ti, Mg, Al, W, Zn, Sn, Zr, Ga, V, B, Mo, As, Ge, P, Pb, Si, Sb, Nb, Ta, Re and At least one of the steps of adding at least one metal component selected from the group consisting of Bi is performed.

In the main firing, when the mixture of the composite hydroxide particles and the lithium compound as the filler is filled in the sheath for firing, the surface area (S) including the contact surface of the filler with the sheath and the filler The lower limit of the volume (V) ratio S / V is not particularly limited, but is preferably 0.08 mm ² / mm ³ from the viewpoint of making the temperature of the filling uniform. In addition, the upper limit is not particularly limited, but is preferably 2.00 mm ² / mm ³ from the viewpoint of productivity, more preferably 0.68 mm ² / mm ^3, and particularly preferably 0.36mm ² / mm ^3. The above lower limit and upper limit can be arbitrarily combined. Although there is no particular limitation on the sheath, for example, a sheath having an inner size of 130 mm × 130 mm × 88 mm or 280 mm × 280 mm × 88 mm is exemplified.

The calcining step is a step for releasing the gas contained in the raw material and oxidizing the same to make the crystallinity of the positive electrode active material for a secondary battery more preferable. The calcination is, for example, preferably at least 300 ° C and at most 800 ° C, particularly preferably at least 650 ° C and at most 760 ° C. Further, the calcination time of the calcination is not particularly limited, but is, for example, preferably 1 to 20 hours, and particularly preferably 3 to 10 hours. The rate of temperature rise in the preliminary firing is preferably 50 to 550 ° C / h, more preferably 100 to 400 ° C / h, and 140 ° C to 380 ° C / h from the viewpoint of keeping the material temperature and the temperature of the firing furnace equal. Is particularly preferred. The atmosphere for the preliminary firing is not particularly limited, and examples thereof include air and oxygen. The firing furnace used for the preliminary firing is not particularly limited, and examples thereof include a stationary box furnace and a roller hearth continuous furnace.

焼 The tempering step is a step for making the crystallinity of the positive electrode active material for a secondary battery more preferable. The tempering step is, for example, preferably at least 600 ° C and no more than 900 ° C, particularly preferably at least 650 ° C and no more than 860 ° C. The firing time for tempering is not particularly limited, but is, for example, preferably 1 to 20 hours, and particularly preferably 3 to 10 hours. The temperature rising rate in the tempering is preferably 50 to 550 ° C./h, more preferably 100 to 400 ° C./h, and 140 to 380 ° C./h from the viewpoint of keeping the material temperature and the temperature of the firing furnace equal. Particularly preferred. The tempering atmosphere is not particularly limited, but includes, for example, air and oxygen. The firing furnace used for tempering is not particularly limited, and examples thereof include a stationary box furnace and a roller hearth continuous furnace.

Also, a group consisting of Fe, Cu, Ti, Mg, Al, W, Zn, Sn, Zr, Ga, V, B, Mo, As, Ge, P, Pb, Si, Sb, Nb, Ta, Re, and Bi. The step of adding at least one metal component selected from the above is a step for making the crystallinity of the positive electrode active material for a secondary battery more preferable.

[Secondary battery]
Next, a positive electrode using the positive electrode active material for a secondary battery of the present invention as a positive electrode active material of a secondary battery and a secondary battery having the positive electrode will be described while describing the configuration of the secondary battery. Here, a lithium secondary battery will be described as an example of the secondary battery.

One example of a lithium secondary battery using the positive electrode active material for a secondary battery of the present invention as a positive electrode active material is a positive electrode and a negative electrode, a separator sandwiched between the positive electrode and the negative electrode, and disposed between the positive electrode and the negative electrode. Electrolyte solution.

FIG. 2 is a schematic diagram showing an example of a lithium secondary battery. The cylindrical lithium secondary battery 10 shown in FIG. 2 is manufactured as follows.

First, as shown in FIG. 2A, a pair of separators 1 having a band shape, a band-shaped positive electrode 2 having a positive electrode lead 21 at one end, and a band-shaped negative electrode 3 having a negative electrode lead 31 at one end are separated from each other by a separator 1. The positive electrode 2, the separator 1, and the negative electrode 3 are laminated in this order and wound to form an electrode group 4.

Next, as shown in FIG. 2B, after housing the electrode group 4 and an insulator (not shown) inside the battery can 5, the bottom of the battery can 5 is sealed, and the electrode group 4 is impregnated with the electrolytic solution 6. Then, an electrolyte is disposed between the positive electrode 2 and the negative electrode 3. Further, by sealing the upper portion of the battery can 5 with the top insulator 7 and the sealing body 8, the lithium secondary battery 10 can be manufactured.

The shape of the electrode group 4 is not particularly limited. For example, the cross-sectional shape when the electrode group 4 is cut in a direction perpendicular to the axis of winding is a circle, an ellipse, a rectangle, and a rounded rectangle. Columnar shapes can be mentioned.

Further, as the shape of the lithium secondary battery having such an electrode group 4, a shape defined by IEC60086, which is a standard for batteries defined by the International Electrotechnical Commission (IEC), or a shape defined by JIS C # 8500 can be adopted. . Examples of the shape defined by the standard include a cylindrical shape and a square shape.

Further, the lithium secondary battery is not limited to the above-described wound configuration, and may be a stacked configuration in which a stacked structure of a positive electrode, a separator, a negative electrode, and a separator is repeatedly stacked. Examples of the stacked lithium secondary battery include a so-called coin battery, a button battery, and a paper (or sheet) battery.

Hereinafter, each configuration of the lithium secondary battery will be described in order.
(Positive electrode)
For the positive electrode of a lithium secondary battery, first, a positive electrode mixture containing a positive electrode active material (a positive electrode active material for a secondary battery of the present invention), a conductive material and a binder is prepared, and the positive electrode mixture is supported on a positive electrode current collector. It can be manufactured by

(Conductive material)
As the conductive material of the positive electrode of the lithium secondary battery, a carbon material can be used. Examples of the carbon material include graphite powder, carbon black (for example, acetylene black), and a fibrous carbon material. Carbon black is a fine particle and has a large surface area.By adding a small amount to the positive electrode mixture, the conductivity inside the positive electrode can be increased, and the charge / discharge efficiency and output characteristics can be improved. Both the binding force between the positive electrode mixture and the positive electrode current collector and the binding force inside the positive electrode mixture decrease, which causes an increase in internal resistance.

割 合 The proportion of the conductive material in the positive electrode mixture can be appropriately selected depending on the use conditions and the like, but is preferably 5 parts by mass or more and 20 parts by mass or less based on 100 parts by mass of the positive electrode active material. When a fibrous carbon material such as graphitized carbon fiber or carbon nanotube is used as the conductive material, the ratio can be reduced.

(binder)
As a binder included in the positive electrode of the lithium secondary battery, a thermoplastic resin can be used. Examples of the thermoplastic resin include polyvinylidene fluoride (hereinafter sometimes referred to as PVdF), polytetrafluoroethylene (hereinafter sometimes referred to as PTFE), and ethylene tetrafluoride / propylene hexafluoride / vinylidene fluoride. Fluororesins such as polymers, propylene hexafluoride / vinylidene fluoride copolymers, and tetrafluoroethylene / perfluorovinyl ether copolymers; polyolefin resins such as polyethylene and polypropylene; These thermoplastic resins may be used alone or in combination of two or more.

Among these thermoplastic resins, a fluororesin and a polyolefin resin are used as a binder, and the ratio of the fluororesin to the whole positive electrode mixture is 1% by mass to 10% by mass, and the ratio of the polyolefin resin is 0.1% by mass to 2% by mass. % Or less, it is possible to obtain a positive electrode mixture in which both the adhesion to the positive electrode current collector and the bonding force inside the positive electrode mixture are high.

(Positive electrode current collector)
As the positive electrode current collector included in the positive electrode of the lithium secondary battery, a belt-shaped member formed using a metal material such as Al, Ni, or stainless steel can be used. Among them, a material formed into a thin film using Al as a forming material is preferable because it is easy to process and inexpensive.

The method for supporting the positive electrode mixture on the positive electrode current collector is not particularly limited. For example, a method in which the positive electrode mixture is pressure-formed on the positive electrode current collector may be mentioned. In addition, the positive electrode mixture is paste-formed using an organic solvent, the obtained positive electrode mixture paste is applied to at least one surface of the positive electrode current collector, dried, pressed and fixed, so that the positive electrode A mixture may be carried.

When the positive electrode mixture is made into a paste, examples of the organic solvent that can be used include, for example, amine solvents such as N, N-dimethylaminopropylamine and diethylenetriamine; ether solvents such as tetrahydrofuran; ketone solvents such as methyl ethyl ketone; Ester solvents such as methyl acetate; amide solvents such as dimethylacetamide and N-methyl-2-pyrrolidone (hereinafter sometimes referred to as NMP). These may be used alone or in combination of two or more.

方法 Examples of the method of applying the paste of the positive electrode mixture to the positive electrode current collector include a slit die coating method, a screen coating method, a curtain coating method, a knife coating method, a gravure coating method, and an electrostatic spray method. The positive electrode can be manufactured by the method described above.

(Negative electrode)
The negative electrode of the lithium secondary battery may be capable of doping and undoping lithium ions at a potential lower than that of the positive electrode, and an electrode in which a negative electrode mixture containing a negative electrode active material is supported on a negative electrode current collector, a negative electrode An electrode made of the active material alone can be used.

(Negative electrode active material)
The negative electrode active material of the negative electrode of the lithium secondary battery is a carbon material, a chalcogen compound (oxide, sulfide, etc.), a nitride, a metal, or an alloy. Doping and undoping of lithium ions at a lower potential than the positive electrode is performed. Possible materials are listed.

Examples of the carbon material that can be used as the negative electrode active material of the lithium secondary battery include natural graphite, graphite such as artificial graphite, cokes, carbon black, pyrolytic carbons, carbon fibers, and fired organic polymer compounds. be able to.

Examples of oxides that can be used as the negative electrode active material of the lithium secondary battery include, for example, silicon oxide represented by the formula SiO _x (where x is a positive real number) such as SiO ₂ and SiO; TiO ₂ , TiO Oxide of titanium represented by the formula TiO _x (where x is a positive real number); vanadium represented by the formula VO _x (where x is a positive real number) such as V ₂ O ₅ and VO ₂ Oxide; iron oxide represented by the formula FeO _x (where x is a positive real number) such as Fe ₃ O ₄ , Fe ₂ O ₃ , and FeO; SnO _x such as SnO ₂ and SnO (where x Is a positive real number); a tungsten oxide represented by a general formula WO _x (where x is a positive real number) such as WO ₃ and WO ₂ ; Li ₄ Ti ₅ O ₁₂ ; containing lithium and titanium or vanadium such as LiVO ₂ Complex metal oxides; and the like.

Examples of the sulfide that can be used as the negative electrode active material of the lithium secondary battery include titanium sulfide represented by the formula TiS _x (where x is a positive real number) such as Ti ₂ S ₃ , TiS ₂ , and TiS. A sulfide of vanadium represented by the formula VS _x (where x is a positive real number) such as V ₃ S ₄ , VS ₂ , and VS; a formula FeS _x (here, such as Fe ₃ S ₄ , FeS ₂ , and FeS) a sulfide of iron represented by x is a positive real number; a sulfide of molybdenum represented by a formula MoS _x (where x is a positive real number) such as Mo ₂ S ₃ or MoS ₂ ; SnS ₂ , SnS, etc. (wherein, x represents a positive real number) the formula SnS _x sulfides of tin represented by; WS ₂ wherein WS _x (wherein, x represents a positive real number) such as sulfides of tungsten represented by; _Sb 2 S _{3 and the} like represented by the expression SbS _x (where x is a positive real number) Simon sulfide; selenium sulfide represented by the formula SeS _x (where x is a positive real number) such as Se ₅ S ₃ , SeS ₂ , and SeS;

As a nitride usable as a negative electrode active material of a lithium secondary battery, for example, Li ₃ N, Li _3-x A _x N (where A is one or both of Ni and Co, and 0 < x <3).

は These carbon materials, oxides, sulfides and nitrides may be used alone or in combination of two or more. In addition, these carbon materials, oxides, sulfides, and nitrides may be either crystalline or amorphous.

金属 Further, examples of the metal that can be used as the negative electrode active material of the lithium secondary battery include lithium metal, silicon metal, tin metal, and the like.

Examples of alloys usable as the negative electrode active material of the lithium secondary battery include lithium alloys such as Li-Al, Li-Ni, Li-Si, Li-Sn, and Li-Sn-Ni; silicon such as Si-Zn alloy; it may also be mentioned; Sn-Mn, Sn-Co , Sn-Ni, Sn-Cu, tin alloys such as _Sn-La; Cu 2 _Sb, alloys such as La 3 _Ni 2 Sn _7.

These metals and alloys are mainly used alone as a negative electrode after being processed into a foil shape, for example.

Among the negative electrode active materials, the potential of the negative electrode hardly changes from an uncharged state to a fully charged state during charging (good potential flatness), the average discharge potential is low, and the capacity retention rate when repeatedly charged and discharged is low. A carbon material containing graphite as a main component, such as natural graphite or artificial graphite, is preferred because of its high property (good cycle characteristics). The shape of the carbon material is not particularly limited, and may be, for example, any of a flaky shape such as natural graphite, a spherical shape such as mesocarbon microbeads, a fibrous shape such as graphitized carbon fiber, and an aggregate of fine powder. May be.

負極 The negative electrode mixture of the lithium secondary battery may contain a binder, if necessary. Examples of the binder include thermoplastic resins, and examples thereof include PVdF, thermoplastic polyimide, carboxymethyl cellulose, and polyolefin resins such as polyethylene and polypropylene. These may be used alone or in combination of two or more.

(Negative electrode current collector)
Examples of the negative electrode current collector included in the negative electrode of the lithium secondary battery include a band-shaped member formed of a metal material such as Cu, Ni, and stainless steel. Among them, it is preferable to use Cu as a forming material and process it into a thin film, since it is difficult to form an alloy with lithium and easy to process.

The method for supporting the negative electrode mixture on the negative electrode current collector is not particularly limited. As in the case of the positive electrode, for example, a method by pressure molding, paste using a solvent or the like, and apply on the negative electrode current collector, After drying, a method of pressing and pressing is given.

(Separator)
As a separator included in the lithium secondary battery, for example, polyethylene, a polyolefin resin such as polypropylene, a fluorine resin, a material such as a nitrogen-containing aromatic polymer, a porous film, a nonwoven fabric, a material having a form such as a woven fabric. Can be used. Further, one or more of these materials may be used to form a separator, or these materials may be laminated to form a separator.

Examples of the separator of the lithium secondary battery include separators described in JP-A-2000-30686 and JP-A-10-324758. The thickness of the separator can be appropriately selected depending on the use conditions and the like, but it is preferable that the thickness be reduced as long as the mechanical strength is maintained, in that the volume energy density of the lithium secondary battery increases and the internal resistance decreases. And more preferably about 5 to 200 μm, particularly preferably about 5 to 40 μm.

セ パ レ ー タ The separator of the lithium secondary battery preferably has a porous film containing a thermoplastic resin. In lithium secondary batteries, when an abnormal current flows in the battery due to a short circuit between the positive electrode and the negative electrode, the function of shutting off the current at the short-circuit point and preventing the excessive current from flowing (shut down) It is preferred to have. Here, the shutdown is performed by overheating of the separator at the short-circuited portion due to the short-circuit, and when the operating temperature exceeds a previously assumed use temperature, the porous film in the separator softens or melts to close the micropores. Then, even if the temperature in the lithium secondary battery rises to a certain high temperature after the separator is shut down, it is preferable that the shut down state be maintained without causing film breakage due to the temperature.

After the separator shuts down, even if the temperature inside the lithium secondary battery rises to a certain high temperature, the temperature-resistant separator does not break down, and as a separator, the heat-resistant porous layer and the porous film are laminated. And the resulting laminated film. By using such a laminated film as a separator, the heat resistance of the secondary battery can be further increased. In the laminated film, the heat-resistant porous layer may be laminated on both sides of the porous film.

(Laminated film)
Hereinafter, a laminated film in which the heat-resistant porous layer and the porous film are laminated on each other will be described.

に お い て In the laminated film used as the separator of the lithium secondary battery, the heat-resistant porous layer is a layer having higher heat resistance than the porous film. The heat-resistant porous layer may be formed from an inorganic powder (first heat-resistant porous layer), may be formed from a heat-resistant resin (second heat-resistant porous layer), and includes a heat-resistant resin and a filler. (Third heat-resistant porous layer). When the heat-resistant porous layer contains a heat-resistant resin, the heat-resistant porous layer can be formed by an easy method such as coating.

(First heat resistant porous layer)
When the heat-resistant porous layer is formed from an inorganic powder, examples of the inorganic powder used for the heat-resistant porous layer include inorganic substances such as metal oxides, metal nitrides, metal carbides, metal hydroxides, carbonates, and sulfates. Of these, and among these, a powder made of an inorganic material having low conductivity (high insulation) is preferably used. Specific examples include alumina powder, silica powder, titanium dioxide powder, calcium carbonate powder and the like. Such inorganic powders may be used alone or in combination of two or more.

ア ル ミ ナ Among these inorganic powders, alumina powder is preferred because of its high chemical stability. Further, it is more preferable that all of the particles constituting the inorganic powder are alumina particles, all of the particles constituting the inorganic powder are alumina particles, and some or all of the particles are substantially spherical alumina particles. Is more preferable.

(Second heat resistant porous layer)
When the heat-resistant porous layer is formed from a heat-resistant resin, as the heat-resistant resin used for the heat-resistant porous layer, for example, polyamide, polyimide, polyamideimide, polycarbonate, polyacetal, polysulfone, polyphenylene sulfide, polyether ketone, aromatic polyester, Examples thereof include polyethersulfone and polyetherimide. In order to further increase the heat resistance of the laminated film, polyamide, polyimide, polyamideimide, polyethersulfone, and polyetherimide are preferred, and polyamide, polyimide, and polyamideimide are more preferred.

The heat-resistant resin used for the heat-resistant porous layer is more preferably a nitrogen-containing aromatic polymer such as an aromatic polyamide (para-oriented aromatic polyamide or meta-oriented aromatic polyamide), aromatic polyimide, or aromatic polyamide-imide, Particularly preferred is an aromatic polyamide, and particularly preferred from the viewpoint of productivity is a para-oriented aromatic polyamide (hereinafter sometimes referred to as para-aramid).

耐熱 Further, examples of the heat-resistant resin include poly-4-methylpentene-1 and a cyclic olefin polymer.

耐熱 By using these heat-resistant resins, the heat resistance of the laminated film used as the separator of the lithium secondary battery, that is, the thermal rupture temperature of the laminated film can be further increased. Among these heat-resistant resins, when using a nitrogen-containing aromatic polymer, it may be due to the polarity in the molecule, compatibility with the electrolytic solution, that is, the liquid retention in the heat-resistant porous layer may be improved, The rate of impregnation of the electrolyte during the production of the lithium secondary battery is also high, and the charge / discharge capacity of the lithium secondary battery is further increased.

熱 The thermal rupture temperature of the laminated film depends on the type of heat-resistant resin, and is selected and used according to the use scene and purpose. Specifically, when the above nitrogen-containing aromatic polymer is used as the heat-resistant resin, the cyclic olefin-based polymer is heated to about 400 ° C., and when poly-4-methylpentene-1 is used, to about 250 ° C. When used, the thermal rupture temperature can be controlled to about 300 ° C., respectively. When the heat-resistant porous layer is made of an inorganic powder, the thermal rupture temperature can be controlled to, for example, 500 ° C. or more.

The para-aramid is obtained by condensation polymerization of a para-oriented aromatic diamine and a para-oriented aromatic dicarboxylic acid halide, and the amide bond has a para-position of an aromatic ring or an alignment position corresponding thereto (for example, 4,4 ′). -Essentially consisting of repeating units linked in opposite directions, coaxial or parallel, such as biphenylene, 1,5-naphthalene, 2,6-naphthalene and the like. Specifically, poly (paraphenylene terephthalamide), poly (parabenzamide), poly (4,4′-benzanilide terephthalamide), poly (paraphenylene-4,4′-biphenylenedicarboxylic acid amide), poly ( Para-oriented or para-oriented such as paraphenylene-2,6-naphthalenedicarboxylic acid amide), poly (2-chloro-paraphenylene terephthalamide), paraphenylene terephthalamide / 2,6-dichloroparaphenylene terephthalamide copolymer Para-aramid having a structure according to the mold is exemplified.

全 As the aromatic polyimide, a wholly aromatic polyimide produced by condensation polymerization of an aromatic diacid anhydride and a diamine is preferable.

Specific examples of the aromatic dianhydride used for the condensation polymerization include pyromellitic dianhydride, 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride, 3,3 ′, 4 , 4'-benzophenonetetracarboxylic dianhydride, 2,2'-bis (3,4-dicarboxyphenyl) hexafluoropropane, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride and the like No.

Specific examples of the diamine used for the condensation polymerization include oxydianiline, paraphenylenediamine, benzophenonediamine, 3,3′-methylenedianiline, 3,3′-diaminobensophenone, and 3,3′-diaminodiphenylsulfone. , 1,5-naphthalenediamine and the like.

ポ リ イ ミ ド As the aromatic polyimide, a polyimide soluble in a solvent can be suitably used. Examples of such a polyimide include a polyimide which is a polycondensate of 3,3 ', 4,4'-diphenylsulfonetetracarboxylic dianhydride and an aromatic diamine.

As the aromatic polyamide-imide, for example, those obtained from the condensation polymerization thereof using an aromatic dicarboxylic acid and an aromatic diisocyanate, those obtained from the condensation polymerization thereof using an aromatic dianhydride and an aromatic diisocyanate Are included. Specific examples of the aromatic dicarboxylic acid include isophthalic acid and terephthalic acid. Specific examples of the aromatic dianhydride include trimellitic anhydride. Specific examples of the aromatic diisocyanate include 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, ortho tolylene diisocyanate, and m-xylene diisocyanate.

Further, in order to further increase the ion permeability, the thickness of the heat-resistant porous layer of the laminated film is preferably a thin heat-resistant porous layer, more preferably 1 μm or more and 10 μm or less, further preferably 1 μm or more and 5 μm or less. More preferably, it is 4 μm or less. Further, the heat-resistant porous layer has fine pores, and the size (diameter) of the pores is preferably 3 μm or less, more preferably 1 μm or less.

(Third heat resistant porous layer)
When the heat-resistant porous layer is formed to include a heat-resistant resin and a filler, the same heat-resistant resin as that used for the second heat-resistant porous layer can be used. As the filler, at least one selected from the group consisting of organic powders, inorganic powders, and mixtures thereof can be used. The particles constituting the filler preferably have an average particle diameter of 0.01 μm or more and 1 μm or less.

Examples of the organic powder that can be used as the filler include, for example, a homopolymer or a copolymer of two or more of styrene, vinyl ketone, acrylonitrile, methyl methacrylate, ethyl methacrylate, glycidyl methacrylate, glycidyl acrylate, and methyl acrylate; PTFE, tetrafluoroethylene-6-fluoropropylene copolymer, fluorocarbon resin such as tetrafluoroethylene-ethylene copolymer, polyvinylidene fluoride; melamine resin; urea resin; polyolefin resin; polymethacrylate; A powder consisting of Such organic powders may be used alone or in combination of two or more. Among these organic powders, PTFE powder is preferred because of its high chemical stability.

無機 As the inorganic powder that can be used as the filler, the same powder as the inorganic powder used for the heat-resistant porous layer can be exemplified.

When the heat-resistant porous layer is formed containing a heat-resistant resin and a filler, the content of the filler depends on the specific gravity of the material of the filler, for example, when all of the particles constituting the filler are alumina particles When the total mass of the heat-resistant porous layer is 100 parts by mass, the mass of the filler is preferably 5 parts by mass or more and 95 parts by mass or less, more preferably 20 parts by mass or more and 95 parts by mass or less, Preferably it is 30 parts by mass or more and 90 parts by mass or less. These ranges can be appropriately set depending on the specific gravity of the material of the filler.

The shape of the filler is not particularly limited, and examples thereof include shapes such as a substantially spherical shape, a plate shape, a column shape, a needle shape, and a fibrous shape, and any particles can be used, but since it is easy to form uniform pores, Preferably, the particles are substantially spherical particles. Examples of the substantially spherical particles include particles having an aspect ratio of particles (major axis of particles / minor axis of particles) of 1.0 or more and 1.5 or less. The aspect ratio of the particles can be measured by an electron micrograph.

に お い て In a laminated film used as a separator of a lithium secondary battery, the porous film preferably has fine pores and has a shutdown function. In this case, the porous film contains a thermoplastic resin.

サ イ ズ The size of the micropores in the porous film is preferably as small as possible, more preferably 3 μm or less, and particularly preferably 1 μm or less. The porosity of the porous film can be appropriately selected depending on the use conditions and the like, but is preferably 30% by volume or more and 80% by volume or less, more preferably 40% by volume or more and 70% by volume or less. In a lithium secondary battery, when the use temperature exceeds a previously assumed use temperature, the porous film containing a thermoplastic resin closes the micropores by softening or melting of the thermoplastic resin constituting the porous film. be able to.

熱 The thermoplastic resin used for the porous film can be used without any particular limitation as long as it does not dissolve in the electrolytic solution of the lithium secondary battery. Specific examples include polyolefin resins such as polyethylene and polypropylene, and thermoplastic polyurethane resins. A mixture of two or more of these may be used.

In order for the separator to soften at a lower temperature and shut down, the porous film preferably contains polyethylene. Examples of polyethylene include polyethylene such as low-density polyethylene, high-density polyethylene, and linear polyethylene, and ultrahigh-molecular-weight polyethylene having a molecular weight of 1,000,000 or more.

In order to further increase the piercing strength of the porous film, the thermoplastic resin constituting the porous film preferably contains at least ultrahigh molecular weight polyethylene. From the viewpoint of the production of the porous film, the thermoplastic resin may preferably contain a wax composed of a polyolefin having a low molecular weight (weight average molecular weight of 10,000 or less).

Although the thickness of the porous film in the laminated film can be appropriately selected according to the conditions of use and the like, it is preferably 3 μm or more and 30 μm or less, more preferably 3 μm or more and 25 μm or less. In addition, the thickness of the laminated film can be appropriately selected depending on the use conditions and the like, but is preferably 40 μm or less, more preferably 30 μm or less. When the thickness of the heat-resistant porous layer is A (μm) and the thickness of the porous film is B (μm), the value of A / B is preferably 0.1 or more and 1.0 or less.

In the lithium secondary battery, the separator has a gas permeability resistance of 50 seconds / 100 cc or more and 300 seconds / hour according to the Gurley method defined in JIS P # 8117 in order to allow the electrolyte to pass well when the battery is used (during charge / discharge). It is preferably 100 cc or less, more preferably 50 seconds / 100 cc or more and 200 seconds / 100 cc or less.

空 Also, the porosity of the separator can be appropriately selected depending on the use conditions and the like, but is preferably 30% by volume or more and 80% by volume or less, more preferably 40% by volume or more and 70% by volume or less. The separator used may be a laminate of separators having different porosity.

(Electrolyte)
The electrolytic solution of the lithium secondary battery contains an electrolyte and an organic solvent.

As the electrolyte contained in the electrolyte, LiClO ₄ , LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiN (SO ₂ CF ₃ ) (COCF ₃ ), Li (C ₄ F ₉ SO ₃ ), LiC (SO ₂ CF ₃ ) ₃ , Li ₂ B ₁₀ Cl ₁₀ , LiBOB (here, BOB is bis (oxalato) borate ), LiFSI (here, FSI is bis (fluorosulfonyl) imide), lithium salts of lower aliphatic carboxylic acids, and lithium salts such as LiAlCl ₄ . These may be used alone or in combination of two or more. Among them, the electrolyte is selected from the group consisting of LiPF ₆ containing fluorine, LiAsF ₆ , LiSbF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ and LiC (SO ₂ CF ₃ ) _3. It is preferable to use one containing at least one kind.

Examples of the organic solvent contained in the electrolytic solution include propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 4-trifluoromethyl-1,3-dioxolan-2-one, and 1,2. Carbonates such as -di (methoxycarbonyloxy) ethane; 1,2-dimethoxyethane, 1,3-dimethoxypropane, pentafluoropropylmethyl ether, 2,2,3,3-tetrafluoropropyldifluoromethyl ether, tetrahydrofuran, Ethers such as 2-methyltetrahydrofuran; esters such as methyl formate, methyl acetate and γ-butyrolactone; nitriles such as acetonitrile and butyronitrile; N, N-dimethylformamide, N, N-dimethyl Amides such as acetamide; carbamates such as 3-methyl-2-oxazolidone; sulfur-containing compounds such as sulfolane, dimethyl sulfoxide, and 1,3-propane sultone; or those obtained by further introducing a fluoro group into these organic solvents ( In which one or more of the hydrogen atoms of the organic solvent are substituted with a fluorine atom) can be used. These may be used alone or in combination of two or more.

Among them, a mixed solvent containing carbonates is preferable, and a mixed solvent of cyclic carbonate and acyclic carbonate, and a mixed solvent of cyclic carbonate and ether are more preferable. As the mixed solvent of the cyclic carbonate and the non-cyclic carbonate, a mixed solvent containing ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate is preferable. The electrolytic solution using such a mixed solvent has a wide operating temperature range, hardly deteriorates even when charged and discharged at a high current rate, hardly deteriorates even when used for a long time, and natural graphite as an active material of a negative electrode. It has many features that it is hardly decomposable even when a graphite material such as artificial graphite is used.

Further, as the electrolyte, in order to improve the safety of the lithium secondary battery, it is preferable to use an electrolyte containing a lithium salt containing fluorine such as LiPF ₆ and an organic solvent having a fluorine substituent. Among them, a mixed solvent containing dimethyl carbonate and ethers having a fluorine substituent such as pentafluoropropyl methyl ether and 2,2,3,3-tetrafluoropropyl difluoromethyl ether performs charge / discharge at a high current rate. However, since the capacity retention ratio is high, it is more preferable.

A solid electrolyte may be used instead of the above electrolyte. As the solid electrolyte, for example, an organic polymer electrolyte such as a polyethylene oxide polymer compound or a polymer compound containing at least one polyorganosiloxane chain or polyoxyalkylene chain can be used. Further, a so-called gel type in which a non-aqueous electrolyte is held in a polymer compound can also be used. Also, Li ₂ S—SiS ₂ , Li ₂ S—GeS ₂ , Li ₂ S—P ₂ S ₅ , Li ₂ S—B ₂ S ₃ , Li ₂ S—SiS ₂ —Li ₃ PO ₄ , Li ₂ S—SiS _{2 -Li 2 SO 4, Li 2} S-GeS inorganic solid electrolytes containing sulfides such as 2 _-P 2 _{S 5} and the like. These may be used alone or in combination of two or more. By using these solid electrolytes, the safety of the lithium secondary battery may be further improved.

In addition, in the case of using a solid electrolyte in a lithium secondary battery, the solid electrolyte may serve as a separator, and in such a case, the separator may not be required.

Since the positive electrode active material having the above-described configuration uses the positive electrode active material for a secondary battery of the present invention, a lithium secondary battery using the positive electrode active material can be used in an excellent cycle at room temperature and high temperature. It can be characteristic.

In addition, since the positive electrode having the above-described structure has the positive electrode active material for a secondary battery of the present invention, a lithium secondary battery may exhibit excellent cycle characteristics at normal temperature and high temperature. it can.

Further, since the lithium secondary battery having the above-described configuration includes the positive electrode having the positive electrode active material for a secondary battery of the present invention, it exhibits excellent cycle characteristics at ordinary temperatures and high temperatures in both environments. can do.

Next, examples of the present invention will be described, but the present invention is not limited to these examples unless it exceeds the gist.

Method for Producing Positive Electrode Active Material for Secondary Battery of Examples 1 to 7 and Comparative Examples 1 to 4 Preparation of Nickel, Cobalt, and Manganese Composite Hydroxide Particles Used in Examples 3 and 4 and Comparative Examples 2 and 3 An aqueous solution in which nickel sulfate, cobalt sulfate, and manganese sulfate are dissolved at a predetermined ratio (atomic ratio of nickel: cobalt: manganese = 50: 20: 30) and an aqueous solution of ammonium sulfate are added dropwise to the reaction tank, and the reaction temperature is reduced in the reaction tank. Sodium hydroxide was added dropwise at appropriate times so that the reaction pH became 11.9 based on a temperature of 30.0 ° C. and a liquid temperature of 40 ° C., thereby producing a composite hydroxide of nickel, cobalt and manganese. The generated hydroxide is continuously overflowed from the overflow tube of the reaction tank, taken out, filtered, washed with water, and dried at 100 ° C. to obtain nickel, which is a precursor of a positive electrode active material for a secondary battery. , Cobalt and manganese composite hydroxide particles were obtained. D50 of the nickel, cobalt and manganese composite hydroxide particles was 3.9 μm, and (D90−D10) / D50 was 0.96.

Preparation of nickel, cobalt, and manganese composite hydroxide particles used in Examples 1, 2, 6, and 7 The nickel, cobalt, and manganese composite hydroxide particles used in Examples 3 and 4 and Comparative Examples 2 and 3 were dry-classified. Thus, nickel, cobalt, and manganese composite hydroxide particles having a D50 of 4.2 to 4.4 μm and a (D90-D10) / D50 of 0.78 to 0.88 were prepared.

Preparation of Nickel, Cobalt, and Manganese Composite Hydroxide Particles Used in Example 5 and Comparative Examples 1 and 4 In a reaction vessel equipped with a stirrer, nickel sulfate, cobalt sulfate, and manganese sulfate in a predetermined ratio (nickel: cobalt: manganese = 50). : Atomic ratio of 20:30) and an aqueous solution of ammonium sulfate were added dropwise, and sodium hydroxide was added thereto in a reaction vessel at a reaction temperature of 50.0 ° C and a reaction temperature of 40 ° C to adjust the reaction pH to 11.4. By dropping, a composite hydroxide of nickel, cobalt and manganese was produced. The produced hydroxide overflows from the overflow tube of the reaction tank and is continuously taken out, filtered, washed, dehydrated, and dried at 100 ° C. to be a precursor of a positive electrode active material for a secondary battery. Nickel, cobalt and manganese composite hydroxide particles were obtained. D50 of the nickel, cobalt and manganese composite hydroxide particles was 11.6 μm, and (D90−D10) / D50 was 0.90.

Ｄ The values of D50 and (D90-D10) / D50 of the nickel, cobalt and manganese composite hydroxide particles used in Examples 1 to 7 and Comparative Examples 1 to 4 are shown in Table 1 below. The values of D50, D90 and D10 in Table 1 below were measured using a laser diffraction particle size distribution analyzer (LA-950, manufactured by Horiba Seisakusho Co., Ltd.) using 0.1 g of nickel, cobalt and manganese composite hydroxide particles as 0%. The solution was added to 50 ml of a 0.2% by mass aqueous sodium hexametaphosphate solution to obtain a dispersion in which the particles were dispersed. The particle size distribution of the obtained dispersion was measured to obtain a volume-based cumulative particle size distribution curve. In the obtained cumulative particle size distribution curve, the value of the particle diameter (D10) viewed from the fine particle side at the time of 10% accumulation and the value of the particle diameter (D50) viewed from the fine particle side at the time of 50% accumulation are 90%. The value of the particle size (D90) viewed from the fine particle side at the time of% accumulation was defined as the average particle size of the nickel, cobalt, and manganese composite hydroxide particles.

Next, the nickel, cobalt, and manganese composite hydroxide particles, which are dry powders, used in Examples 1 to 7 and Comparative Examples 1 to 4 had the Li / M1 atomic ratios shown in Table 1 below, respectively. Was mixed with lithium carbonate powder to obtain a mixed powder of nickel, cobalt, manganese composite hydroxide particles and lithium carbonate. After the obtained mixed powder was filled in a sheath, firing was performed under firing temperature conditions shown in Table 1 below. The firing was performed using a box furnace in a dry air atmosphere at a temperature rising rate of 200 ° C./min. After each firing step, the fired product was pulverized using a pulverizer (Super Mascolloid MKCA6-2, manufactured by Masuko Sangyo Co., Ltd.), and then sieved with a 325 mesh sieve, and the next step was performed. The filling amount of the mixed powder or the mixed powder after the calcining step in the main firing step into the sheath having an inner size of 130 × 130 × 88 mm is such that the S / V shown in Table 1 below is obtained. did.

In Examples 3 and 6, ZrO ₂ was added at 0.3 mol% to the nickel, cobalt, and manganese composite hydroxide particles before the main firing step, and the main firing was performed. Further, before the tempering step, Al ₂ O ₃ was added. Was added to nickel, cobalt, and manganese composite hydroxide particles in an amount of 1.0 mol% to perform tempering. In Example 4, before the tempering step, Al ₂ O ₃ was added to nickel, cobalt, and manganese composite hydroxide particles in an amount of 1.0 mol% to perform tempering. Further, in Example 7, the main firing was performed before the main firing step by adding 0.3 mol% of ZrO ₂ to the nickel, cobalt, and manganese composite hydroxide particles.

正極 As described above, the positive electrode active materials for secondary batteries of Examples 1 to 7 and Comparative Examples 1 to 4 were produced. Table 2 below shows D50 values of the positive electrode active materials for secondary batteries of Examples 1 to 7 and Comparative Examples 1 to 4. The value of D50 in Table 2 below was measured using a laser diffraction particle size distribution analyzer (LA-950, manufactured by Horiba, Ltd.) in the same manner as in the above composite hydroxide.

The evaluation items of the positive electrode active materials for secondary batteries of the examples and comparative examples are as follows.
(1) Composition Analysis of Secondary Battery Positive Electrode Active Materials The secondary battery positive electrode active materials obtained in Examples 1 to 7 and Comparative Examples 1 to 4 were analyzed for composition. After dissolving the substance powder in hydrochloric acid, the measurement was performed using an inductively coupled plasma emission spectrometer (Perkin Elmer Japan Co., Ltd., Optima 7300DV).

(2) Full width at half maximum of two diffraction peaks in the range of 2θ = 64.5 ± 1 ° X-ray powder diffraction measurement of the positive electrode active materials for secondary batteries obtained in Examples 1 to 7 and Comparative Examples 1 to 4 Was performed using an X-ray diffractometer (Ultima IV, manufactured by Rigaku Corporation). The powder of the positive electrode active material for a secondary battery obtained as described above is filled in a dedicated substrate, and is sampled at a diffraction angle 2θ = 10 ° to 100 ° using a Cu-Kα radiation source (40 kV / 40 mA). An X-ray powder diffraction pattern was obtained by performing the measurement under the conditions of a width of 0.03 ° and a scan speed of 20 ° / min. Using the integrated powder X-ray analysis software PDXL, of the two peaks appearing in the range of 64.5 ± 1 ° from the powder X-ray diffraction pattern, the full width at half maximum of the peak on the low angle side is α, and the peak on the high angle side is α. The full width at half maximum was defined as β, and the half width ratio β / α was calculated.

(3) Average particle strength Measured with a Shimadzu micro compression tester MCT-510.
The positive electrode active materials for secondary batteries obtained in Examples 1 to 7 and Comparative Examples 1 to 4 were performed using “Micro Compression Testing Machine MCT-510” manufactured by Shimadzu Corporation. Among the positive electrode active materials for secondary batteries in the range of volume average particle diameter (D50) ± 1.0 μm measured by the above method, an upper limit test force is applied to one arbitrarily selected positive electrode active material for secondary battery. (Load) A test pressure was applied at a load rate of 200 mN and a load rate constant of 86.7 (load rate of 0.4464 mN / S), and the displacement of the positive electrode active material for a secondary battery was measured. When the test pressure is gradually increased, the pressure value at which the displacement becomes maximum while the test pressure is almost constant is defined as the test force (P), and the equation of Hiramatsu et al. Vol.81, (1965)), the strength (St) was calculated. This operation was performed for a total of 10 particles, and the average particle intensity was calculated from the average value of the particle intensity of the 10 particles.
St = 2.8 × P / (π × d × d) (d: particle diameter)

(4) BET specific surface area
The positive electrode active materials for secondary batteries obtained in Examples 1 to 7 and Comparative Examples 1 to 4 were measured by a one-point BET method using a specific surface area measuring device (Macsorb, manufactured by Mountech Co., Ltd.).

(5) Change rate of lattice constant before and after the cycle test The laminate cells before and after the cycle test used for the capacity retention ratio (cycle characteristics) described later were disassembled, and the positive electrode plate before and after the cycle test was subjected to an X-ray diffractometer (Bruker). , D8 ADVANCE) was used to measure the rate of change of the lattice constant. Specifically, first, a positive electrode plate before and after the cycle test was attached to a glass plate, and a diffraction angle 2θ = 10 ° to 100 ° and a sampling width of 0.0217 ° using a Cu-Kα radiation source (40 kV, 40 mA). An X-ray diffraction pattern was obtained by performing the measurement at a scan speed of 2.6 ° / min. Then, using the XRD analysis software TOPAS, lattice constants of the a-axis and the c-axis were obtained from the X-ray diffraction pattern, and (a-axis before the cycle test / a-axis after the cycle test) × 100, (c before the cycle test) Axis / c axis after cycle test) × 100, the rate of change of the lattice constant before and after the cycle test at 25 ° C. and 60 ° C. was calculated.

Preparation of Positive Electrode The positive electrode active material for a secondary battery (positive electrode active material), a conductive material (acetylene black), and a binder (PVdF) obtained in Examples 1 to 7 and Comparative Examples 1 to 4 were used. A paste-like positive electrode mixture was prepared by adding and kneading the mixture so as to have a composition of material: binder = 90: 5: 5 (mass ratio). In preparing the positive electrode mixture, N-methyl-2-pyrrolidone was used as an organic solvent.

The obtained positive electrode mixture was applied to a 15 μm-thick Al foil serving as a current collector so as to have a basis weight of 10 mg / cm ² , followed by vacuum drying at 120 ° C. for 8 hours to obtain a positive electrode. The electrode area of this positive electrode was 9 cm ² .

Preparation of Negative Electrode Graphite (positive electrode active material), a thickener (CMC) and a binder (SBR400) were used as a negative electrode in a negative electrode active material: thickener: binder = 100: 1: 1 (mass ratio). A paste-like negative electrode mixture was prepared by adding and kneading so as to obtain a composition. When adjusting the negative electrode mixture, water was used as a solvent.

The obtained negative electrode mixture was applied to a 10-μm-thick Cu foil serving as a current collector, and vacuum-dried at 120 ° C. for 8 hours to obtain a negative electrode. The electrode area of this negative electrode was 12 cm ² .

Preparation of Lithium Secondary Battery (Laminated Cell) The following operation was performed in a glove box in a dry air atmosphere at a dew point of −60 ° C.

The positive electrode prepared in “Preparation of positive electrode” is placed on a laminate with the aluminum foil surface facing down, and a laminated film separator (a heat-resistant porous layer is laminated on a polyethylene porous film (thickness: 16 μm)) ), And among the negative electrodes prepared in “Preparation of negative electrode”, a negative electrode having an NP ratio of 1.1 is placed with the aluminum foil surface facing upward, and a laminate is further laminated. The side was fastened and vacuum dried at 60 ° C. for 10 hours. 1.4 g of an electrolytic solution was injected therein, and the other side was sealed with vacuum. The electrolyte was prepared by dissolving LiPF ₆ at a concentration of 1 mol / l in a 3: 5: 2 (volume ratio) mixture of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate.

Using the battery manufactured in "Production of lithium secondary battery (laminate cell)", a chemical conversion step was performed under the following conditions to form an SEI film.
Temperature 25 ° C, maximum charge voltage 4.2V, minimum discharge voltage 2.7V (3.0V only at 10th and 11th cycles)
First cycle: charge time 20 hours, charge current 0.05C, charge method CCCV 0.01C Cut, discharge time 10 hours, discharge current 0.1C, discharge method CC
Second to fourth cycles: charging time 10 hours, charging current 0.1C, charging method CCCV 0.01C Cut, discharging time 5 hours, discharging current 0.2C, discharging method CC
5th to 9th cycles: charging time 5 hours, charging current 0.2C, charging method CCCV 0.05C Cut, discharging time 5 hours, discharging current 0.2C, discharging method CC
10th to 11th cycles: charging time 5 hours, charging current 0.2C, charging method CCCV 0.05C Cut, discharging time 5 hours, discharging current 0.2C, discharging method CC

(6) Capacity maintenance rate (cycle characteristics)
In order to accurately measure the capacity using the battery that had undergone the chemical conversion step, two cycles of charging and discharging at 0.2 C were performed before charging and discharging. Thereafter, a charge / discharge test was performed under the following conditions. The charge capacity and the discharge capacity in the charge / discharge test were determined as follows, and the capacity retention rate was calculated based on the discharge capacity in the first cycle. N = 3 was carried out in each test, and the average value was used as the capacity retention rate of each active material.
Test temperature: 25 ° C
Charging conditions: maximum charging voltage 4.2V, charging time 0.5 hour, charging current 2C, CC
Discharge conditions: minimum discharge voltage 3.0V, discharge time 0.5 hour, discharge current 2C, CC
Number of times of charge and discharge: 1000 times Test temperature: 60 ° C
Charging conditions: maximum charging voltage 4.2V, charging time 0.5 hour, charging current 2C, CC
Discharge conditions: minimum discharge voltage 3.0V, discharge time 0.5 hour, discharge current 2C, CC
Number of charge / discharge cycles: 500

結果 The results of the above evaluation items are shown in Tables 2 to 4 below.

From Tables 2 and 4 above, Example 1 in which the average particle strength is 200 MPa or more and β / α is 0.97 ≦ β / α ≦ 1.25 from the peak of the powder X-ray diffraction pattern using CuKα radiation. In the positive electrode active materials for secondary batteries of Nos. 7 to 7, the capacity retention rate at 25 ° C. 1000 cycles is 80% or more, and the capacity retention rate at 60 ° C. 500 cycles is 75% or more. A positive electrode active material for a secondary battery capable of exhibiting characteristics was obtained. Also, from the above Tables 2, 3, and 4, the average particle strength is 200 MPa or more, and the rate of change of the lattice constant before and after the cycle test is 25.degree. C. and 60.degree. % Or more and 100.90% or less, the positive electrode active materials for secondary batteries of Examples 1 to 7 have a capacity retention rate of 80% or more at 25 ° C. and 1000 cycles and a capacity retention rate of 75% or more at 60 ° C. and 500 cycles. Thus, it was possible to obtain a positive electrode active material for a secondary battery capable of exhibiting excellent cycle characteristics under both normal temperature and high temperature environments. Also, from Table 2, with the positive electrode active materials for secondary batteries of Examples 1 to 7, good D50 and BET specific surface area could be obtained.

In particular, in Examples 3, 4 and 6 in which 1.06 ≦ β / α ≦ 1.13, the capacity retention at 1000 cycles of 25 ° C. was 88% or more, and the capacity retention at 500 cycles of 60 ° C. was 80% or more. Thus, a positive electrode active material for a secondary battery, which can exhibit more excellent cycle characteristics under both normal temperature and high temperature environments, could be obtained. Also, from Tables 1 and 4 above, Example 6 in which (D90-D10) / D50 of the nickel, cobalt, and manganese composite hydroxide particles was 0.78 was (D90-D10) / D50 of 0.96. In comparison with Example 3 in which the firing conditions were the same as in Example 6, the capacity retention at 1000 cycles of 25 ° C. was further improved. Therefore, the cycle characteristics at room temperature were further improved by controlling (D90-D10) / D50 of the composite hydroxide particles to 0.80 or less.

Further, from Tables 1 and 4, p ≧ −600q + 1603 (where q is the atomic ratio of Li to the total of at least one metal element (M1) of Ni, Co and Mn (Li / M1). 1.00 ≦ q ≦ 1.30, p is a main firing temperature, and means a firing temperature of 940 ° C. <p ≦ 1100 ° C.). In Examples 1 to 7 in which at least one of the steps of tempering, tempering, and addition of an additive (Al ₂ O ₃ and / or ZrO ₂ containing the metal element of M2) was carried out, However, it was possible to produce a positive electrode active material for a secondary battery capable of exhibiting excellent cycle characteristics.

Further, in Examples 1 to 7, which can exhibit excellent cycle characteristics under both normal temperature and high temperature environments, a good BET specific surface area of 0.35 m ² to 6.1 m ² / g can be obtained. Was. In Examples 1 to 7, the surface area (S) / volume (V) of the mixed powder at the time of filling was in the range of 0.08 to 0.24 mm ² / mm ³ .

On the other hand, from Tables 2 and 4 above, in the positive electrode active materials for secondary batteries of Comparative Examples 1 and 2 in which the average particle strength is less than 200 MPa and β / α is 0.96 or less, the capacity at 60 ° C. and 500 cycles is shown. The maintenance ratio was 60% or more and 73% or less, and excellent cycle characteristics could not be exhibited in a high temperature environment. From the above Tables 2, 3, and 4, the average particle strength was less than 200 MPa, and the rate of change of the lattice constant before and after the cycle test was 60.degree. C. and the a-axis was 99.25% to 99.26%. In Comparative Examples 2 and 4, the capacity retention at 500 cycles of 60 ° C. was 73%, and excellent cycle characteristics could not be exhibited in a high temperature environment. Also, from Tables 2, 3, and 4 above, a comparative example in which the average particle strength is less than 200 MPa and both the a-axis and the c-axis are out of the range of 99.30% to 100.90% in the test at 60 ° C. In the positive electrode active material for secondary battery of No. 3, the capacity retention rate at 25 ° C. for 1000 cycles was 79%, and the capacity retention rate at 60 ° C. for 500 cycles was 69%, and excellent cycle characteristics were obtained in both normal temperature and high temperature environments. I couldn't.

From Tables 1 and 4 above, although the calcination step was performed, p ≧ −600q + 1603 (where q is Li with respect to the total of the metal elements (M1) composed of at least one of Ni, Co and Mn). 1.00 ≦ q ≦ 1.30, and p is the main firing temperature, which means 940 ° C. <p ≦ 1100 ° C.). In Comparative Example 1, in which the mixture was filled in the sheath without firing, and the S / V was 0.06 cm ² / cm ³ , as described above, excellent cycle characteristics could be exerted under both normal temperature and high temperature environments. Did not. Moreover, in Comparative Examples 2 and 3 in which only the main firing step was performed as the firing step and the metal element of M2 was not added, as described above, excellent cycle characteristics could be obtained stably over a range from room temperature to high temperature. Did not. Moreover, although the calcination process and the main calcination process were performed in the same manner as in the example, when the sheath was filled with the mixture, the S / V was 0.07 cm ² / cm ³ in Comparative Example 4, as described above. Excellent cycle characteristics could not be obtained stably over a range from room temperature to high temperature.

Since the positive electrode active material for a secondary battery of the present invention can exhibit excellent cycle characteristics under both normal temperature and high temperature environments, it can be used in a wide range of fields, for example, in an environment where the use environment such as ambient temperature fluctuates. High value of use in the field of mounting on equipment used for

DESCRIPTION OF SYMBOLS 1 Separator 2 Positive electrode 3 Negative electrode 6 Electrolyte 10 Lithium secondary battery

Claims (9)

1. A secondary battery that is an aggregate of single crystal particles and / or a plurality of primary particles, a positive electrode active material for a secondary battery having a layered structure containing at least one of nickel, cobalt, and manganese,
   The average particle strength of the particles having a cumulative volume percentage of 50% by volume and having a particle diameter (D50) ± 1.0 μm is 200 MPa or more;
   In a powder X-ray diffraction measurement using CuKα ray, the full width at half maximum of the peak on the low angle side of two diffraction peaks appearing in the range of 2θ = 64.5 ± 1 ° is α, and the full width at half maximum of the peak on the high angle side is β. Where β / α satisfies 0.97 ≦ β / α ≦ 1.25.
2. A secondary battery that is an aggregate of single crystal particles and / or a plurality of primary particles, a positive electrode active material for a secondary battery having a layered structure containing at least one of nickel, cobalt, and manganese,
   The average particle strength of the particles having a cumulative volume percentage of 50% by volume and having a particle diameter (D50) ± 1.0 μm is 200 MPa or more;
   In the X-ray diffraction measurement of the positive electrode before and after the cycle test using CuKα rays, the rate of change of the lattice constant before and after the cycle test was calculated as (a axis before the cycle test / a axis after the cycle test) × 100 = A, (cycle When c axis before test / c axis after cycle test) × 100 = C,
   A positive electrode active material for a secondary battery in which at least one of A and C is 99.30% to 100.90% in a cycle test at 25 ° C and 60 ° C.
3. The following general formula (1)
   Li [Li _a (M1 _x M2 _y ) _1-a ] O _{2 + b} (1)
   (Where 0 ≦ a ≦ 0.30, −0.30 ≦ b ≦ 0.30, 0.9 ≦ x ≦ 1.0, 0 ≦ y ≦ 0.1, x + y = 1, M1 is At least one metal element of Ni, Co and Mn, M2 is Fe, Cu, Ti, Mg, Al, W, Zn, Sn, Zr, Ga, V, B, Mo, As, Ge, P , Pb, Si, Sb, Nb, Ta, Re, and Bi means at least one metal element selected from the group consisting of). material.
4. (4) The active material for a secondary battery according to any one of (1) to (3), wherein the particle diameter D50 at a cumulative volume percentage of 50% by volume is from 2.0 μm to 20.0 μm.
5. The active material for a secondary battery according to any one of claims 1 to 4, wherein the BET specific surface area is 0.1 m ² / g or more and 5.0 m ² / g or less.
6. A secondary battery comprising the positive electrode active material for a secondary battery according to any one of claims 1 to 5.
7. A lithium (Li) compound is added to a composite hydroxide particle containing at least one of nickel, cobalt and manganese, and at least a metal element (M1) made of at least one of Ni, Co and Mn. Adding at an atomic ratio of 00 ≦ Li / M1 ≦ 1.30 to obtain a mixture of a lithium compound and composite hydroxide particles;
   The mixture is represented by the following formula p ≧ −600q + 1603 (where q is an atomic ratio (Li / M1) of Li to a total of at least one metal element (M1) of nickel, cobalt and manganese; 1.00 ≦ q ≦ 1.30, p is a main firing temperature, and means a firing temperature represented by 940 ° C. <p ≦ 1100 ° C.)
   Including
   In addition to the main sintering step, the following (1) to (3) steps (1) a calcination step performed before the main sintering step, wherein the sintering temperature is 300 ° C. or more and 800 ° C. or less;
   (2) a tempering step performed after the main firing step, wherein the firing temperature is 600 ° C. or more and 900 ° C. or less;
   (3) Before the main firing step and / or the tempering step, M2 (M2 is Fe, Cu, Ti, Mg, Al, W, Zn, Sn, Zr, Ga, V, B, Mo, As, Ge , P, Pb, Si, Sb, Nb, Ta, Re, and Bi, which means at least one metal element selected from the group consisting of:
   A method for producing a positive electrode active material for a secondary battery, comprising at least one step of the above.
8. 8. The method according to claim 7, further comprising, before the mixing step of the lithium compound and the composite hydroxide particles, setting a particle size distribution width of the composite hydroxide particles to 0.40 ≦ (D90−D10) /D50≦1.00. The production method described in 1.
9. In the main firing step, the ratio of the surface area (S) of the mixture including the contact surface with the sheath to the volume (V) of the mixture when the sheath is filled with the mixture is 0.08 ≦ S / The method according to claim 7, wherein V ≦ 2.00.

Images