KR101100295B1 - Manufacturing method of lithium cobalt oxide - Google Patents

Abstract

Provided is a method for producing lithium cobalt acid, which can provide a nonaqueous electrolyte secondary battery having excellent initial capacity and capacity retention rate.

Lithium cobalt acid whose tap density is 1.8 g / cm <3> or more and pressurization density is 3.5-4.0 g / cm <3>. Lithium cobalt (A) with a tap density of 1.7 to 3.0 g / ml, and lithium cobalt (B) with a tap density of 1.0 to 2.0 g / ml is used for the lithium cobalt (A) and the lithium cobalt (B). A method for producing lithium cobalt oxide, which is mixed so that a tap density difference is 0.20 g / ml or more.

Description

Manufacturing method of lithium cobalt oxide

1 is a SEM photograph (magnification × 3000) showing the particle structure of monodispersed lithium cobalt acid (A) having primary particles of Preparation Example 1.

FIG. 2 is a SEM photograph (magnification × 3000) showing the particle structure of lithium cobalt (B) in which primary particles of Preparation Example 7 are aggregated.

3 is a view showing the safety evaluation of the secondary battery using lithium cobalt oxide of Example 2 and Comparative Example 1 as a positive electrode active material.

4 is a view showing the results of a rapid charge and discharge test of a secondary battery using lithium cobalt oxide of Example 2 and Comparative Example 1 as a positive electrode active material.

The present invention relates to a method for producing lithium cobaltate.

Background Art In recent years, as portable and cordless home appliances have been rapidly developed, nonaqueous electrolyte secondary batteries such as lithium ion secondary batteries have been put into practical use as power sources for small electronic devices such as laptop PCs, mobile phones, video cameras, and the like.

Regarding this lithium ion secondary battery, lithium cobalt acid is useful as a positive electrode active material of a lithium ion secondary battery. Therefore, studies on lithium composite oxides have been actively conducted. As a positive electrode active material, lithium cobalt acid, Many proposals are made about compounds, such as lithium nickelate and lithium manganate.

These cathode active materials have been proposed in various ways in order to improve their performance, and as an important requirement, many technologies have been disclosed in terms of apparent density and press density.

For example, a cathode active material having a tap density of Li _p MO ₂ of 2.65 g / cm 3 or more containing a particulate composition obtained by calcining two or more kinds of starting materials having different average diameters has been proposed (for example, JP 2001-85009 A). Page 1).

In addition, in the positive electrode active material for a nonaqueous electrolyte secondary battery using lithium cobalt acid represented by the formula LiCoO ₂ , the lithium cobalt oxide has a Ferre diameter of 0.1 to 4 μm, and an average particle diameter of 2 μm or less. A non-aqueous electrolyte secondary battery positive electrode active material consisting of spherical or ellipsoidal secondary particles having a large number of small crystal primary particles and having a tap density of at least 2.2 g / cm 3 of lithium cobalt has been proposed (for example, Japan). Patent Publication No. 2001-135313, page 1).

Further, substantially composed of a plurality of secondary particles in which a plurality of micro primary particles of lithium cobalt acid represented by the formula LiCoO ₂ are aggregated, and the secondary particles have a plurality of minute gaps that can penetrate into the electrolyte solution, and also have tabs. A cathode active material for a non-aqueous electrolyte secondary battery using lithium cobalt acid having a density of 2.2 g / cm 3 or more has been proposed (for example, Japanese Patent Application Laid-Open No. 2001-155729).

However, non-aqueous electrolyte secondary batteries using lithium cobalt oxide as a positive electrode active material have failed to satisfy discharge capacity and rapid charge / discharge performance at the same time, and various attempts have been made for them. For example, attempts have been made to increase the battery capacity by increasing the electrode density by changing the particle size or particle shape of lithium cobalt acid, or to increase the rapid charge / discharge performance. Still not getting enough results.

The object of the present invention has been made in view of the problems of the prior art, and has excellent powder properties, high electrode density, high discharge capacity when used in a battery, and excellent cobalt acid performance. It is to provide a method for producing lithium.

The present inventors found that when lithium composite oxide particles are used as the positive electrode active material, not only the particle characteristics of the lithium composite oxide, but also the lithium composite oxide particles having different particle diameters can exhibit the properties of the particles to the maximum. The present invention has been completed.

In the present invention, lithium cobalt (A) having a tap density of 1.7 to 3.0 g / cm 3 and lithium cobalt (B) having a tap density of 1.0 to 2.0 g / cm 3 are represented by the weight ratio of the above lithium cobalt (A): the cobalt acid At a ratio of lithium (B) = 95: 5 to 60:40, the mixture is mixed so that the tap density difference between the lithium cobalt (A) and the lithium cobalt (B) is 0.20 g / cm 3 or more, and the lithium cobalt acid In (A), the primary particles are monodisperse, and the lithium cobalt oxide (B) has a tap density of 1.8 g / cm 3 or more and a press density of 3.5 to 4.0 g using the aggregated primary particles. The manufacturing method of the manufacturing method of the lithium cobalt oxide characterized by manufacturing lithium cobalt acid / cm <3>.

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It is preferable to mix the said lithium cobalt acid (A) and lithium cobalt acid (B) in the ratio of (A) :( B) = 95: 5-60: 40 by weight ratio.

As for said lithium cobalt acid (A), it is preferable that the primary particle is monodisperse and the said lithium cobalt acid (B) uses what the primary particle aggregated.

It is preferable that the average particle diameter of the said lithium cobalt acid (A) is 5-30 micrometers, and the average particle diameter of the said lithium cobalt acid (B) is 0.1-10 micrometers.

The present invention is explained in more detail.

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The lithium cobalt oxide of the present invention has a tap density of 1.8 g / cm 3 or more and a press density of 3.5 to 4.0 g / cm 3.

Such lithium cobalt acid consists of a mixture of at least two or more selected from compounds represented by the following formula (1), or a mixture of the compound represented by the formula (1) and the compound represented by the formula (2).

Li _a CoO ₂

(Where a represents a number in the range of 0.2 ≦ a ≦ 1.2.)

Li _a Co _1-y M _y O _2-z

(Where M represents at least one element selected from the group consisting of transition metals other than Co or elements having atomic numbers of 9 or more, a is 0.2 ≦ a ≦ 1.2, Y is 0 <y ≦ 0.4, and z is 0 ≦ z) Represents a number within the range of ≤ 1.0.)

Specifically, a part of Co of Li _a CoO ₂ or Li _a CoO ₂ may be substituted with another metal element (M). Substituent metal element (M) is one or more elements selected from the group consisting of transition metal elements except Co or elements having atomic number 9 or more, such as Na, Mg, Al, Ca, Ti, V, Cr, Mn, Fe , Ni, Zn, Si, Ga, Zr, Nb, W, Mo is one or more selected from.

In addition, _a sulfate may be coated on the surface of lithium cobalt acid in which a part of Li _a CoO ₂ or Li _a CoO ₂ Co is substituted with another metal element.

Usually, the tap density shows the characteristic that the powder in which granules and granules are mixed naturally is filled without pressing in particular. Pressurized density shows the characteristics of how granulation and granules are filled under pressurization. The present invention has found that lithium cobalt acid having a tap density and a press density in a specific range is important when lithium cobalt acid is used as a positive electrode active material of a nonaqueous electrolyte secondary battery.

That is, the tap density of the lithium cobalt acid of the present invention is preferably 1.8 g / cm 3 or more, preferably 2.0 g / cm 3 or more, and more preferably 2.5 to 3.5 g / cm 3.

The pressure density of the lithium cobalt oxide of the present invention is preferably 3.5 to 4.0 g / cm 3, preferably 3.6 to 4.0 g / cm 3, and more preferably 3.7 to 4.0 g / cm 3.

The lithium cobalt acid of the present invention has excellent characteristics as a positive electrode active material by having a tap density and a press density taking values within the above specific ranges.

Next, the manufacturing method of the lithium cobalt acid of this invention is demonstrated.

The manufacturing method of the lithium cobalt acid of this invention can be obtained by dry-mixing two or more types of lithium cobalt acid from which a tap density differs.

Specifically, the method for producing lithium cobalt according to the present invention includes lithium cobalt (A) having a tap density of 1.7 to 3.0 g / cm 3 and lithium cobalt (B) having a tap density of 1.0 to 2.0 g / cm 3. It is characterized by selecting and mixing so that the tap density difference between lithium acid (A) and the said lithium cobalt acid (B) becomes 0.20 g / cm <3> or more.

The mixing ratio of the lithium cobalt (A) and lithium cobalt (B) is mixed in a weight ratio of (A) :( B) = 95: 5 to 60:40, preferably 90:10 to 80:20. It is desirable to.

As the lithium cobalt acid (A), a tap density of 1.7 to 3.0 g / cm 3 and preferably 2.0 to 3.0 g / cm 3 are preferably used.                     

Lithium cobalt acid (B) is preferably a tap density of 1.0 to 2.0 g / cm 3, preferably 1.0 to 1.7 g / cm 3.

Those lithium cobalt oxides (A) and (B) preferably use different tap densities, and the tap density difference between these lithium cobalt oxides (A) and (B) is preferably 0.20 or more, preferably 0.30 or more.

Moreover, it is preferable that the primary particle of lithium cobalt acid (A) is monodisperse. The monodispersion of the primary particles indicates that the minimum particles are scattered and present, and can be confirmed by SEM (scanning electron microscope) photograph observation. The powder in which 80% or more of the visual field is monodisperse in the SEM may be monodisperse. FIG. 1: shows the SEM photograph (magnification x 3000) which shows the particle structure of the monodisperse lithium cobalt acid (A) which the primary particle of the manufacture example 1 prepared.

The average particle diameter of such lithium cobalt acid (A) is 5-30 micrometers, Preferably the range of 10-20 micrometers is preferable. Lithium cobalt (A) is a coarse particle compared with lithium cobalt (B).

In addition, it is preferable that primary particles are agglomerated to form secondary particles in lithium cobalt (B). Agglomeration of the primary particles to form secondary particles indicates a state in which the minimum particles are attracted by van der Waals and surface charge forces to form a particle shape, specifically, by SEM photograph observation. In the SEM, the powder in which 80% or more of the visual field is aggregated may be referred to as the aggregated powder. FIG. 2: shows the SEM photograph (magnification x 3000) which shows the particle structure of the lithium cobalt (B) in which the primary particle of manufacture example 5 was aggregated.

The average particle diameter of such lithium cobalt acid (B) is 0.1-10 micrometers, Preferably the range of 2.0-8.0 micrometers is preferable.

In the present invention, the average particle diameter represents a cumulative 50% (D ₅₀ ) value of the particle size distribution obtained by the laser scattering particle size distribution analyzer.

In the present invention, excellent battery characteristics when lithium cobalt oxide obtained by mixing lithium cobalt (B) in which primary particles are aggregated with lithium cobalt acid (A) that is monodisperse is used as a positive electrode active material of a nonaqueous electrolyte secondary battery Seems. The reason for this is not clear, but the mixture of these particles not only increases the packing density on the positive electrode plate, but also the aggregated particles are excellent in rapid charging and discharging, and the mono-dispersed particles give high safety characteristics.

In the production method of the present invention, the lithium cobalt (A) preferably uses a compound represented by the formula (1). In addition, it is preferable to use the compound represented by following General formula (1) or the compound represented by General formula (2) as said lithium cobalt acid (B).

<Formula 1>

Li _a CoO ₂

(Where a represents a number in the range of 0.2 ≦ a ≦ 1.2.)

<Formula 2>

Li _a Co _1-y M _y O _2-z

(Where M represents at least one element selected from the group consisting of transition metals other than Co or elements having atomic numbers of 9 or more, a is 0.2 ≦ a ≦ 1.2, Y is 0 <y ≦ 0.4, and z is 0 ≦ z) Represents a number in the range ≤1.0.)

The lithium cobalt acid of the present invention can be obtained by uniformly mixing lithium cobalt acid having two or more different tap densities and average particle diameters, but the method of uniformly mixing is not particularly limited as long as it is an industrially practiced method. . For example, a container rotating mixer such as a horizontal cylindrical type, a V type, a double cone type, a ribbon type, a horizontal screw type, a paddle type, a male ribbon type, a grinding type, a planetary motion type, a static mixer, a single-axis rotor, a Henschel The method of using container fixed mixers, such as a mixer and a flow jet mixer, is mentioned.

The nonaqueous electrolyte secondary battery of the present invention is composed of a positive electrode, a negative electrode, a separator, a nonaqueous electrolyte (for example, a lithium salt-containing electrolyte) and the like.

The positive electrode is obtained by applying a positive electrode mixture containing a positive electrode active material, a conductive agent and a binder on a positive electrode plate (positive electrode collector: for example, an aluminum plate). In the nonaqueous electrolyte secondary battery of the present invention, the positive electrode active material of lithium cobalt acid is used as the positive electrode active material constituting the positive electrode plate. Moreover, when preparing a positive electrode mixture instead of preparing a positive electrode active material previously, you may mix | blend and mix uniformly the lithium cobaltate of this invention of the structure which satisfy | fills the conditions of a positive electrode active material.

In addition to the positive electrode active material, the positive electrode mixture may include a conductive agent, a binder, a filler, and the like.

Examples of the conductive agent include natural graphite (phosphorous graphite, flaky graphite, earthy graphite, etc.), artificial graphite, carbon black, acetylene black, carbon fiber, metal powder such as nickel powder, and the like. One or two or more kinds of conductive materials selected from the group consisting of these may be used. In the above, it is preferable to use graphite and acetylene black together as a electrically conductive agent. The blending amount of the conductive agent in the positive electrode mixture is 1 to 50% by weight, preferably 2 to 30% by weight.

As the binder, for example, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, regenerated cellulose, diacetyl cellulose, polyvinylpyrrolidone, ethylene-propylene-diene-terpolymer (EPDM), sulfonated EPDM, styrene One kind or two or more kinds of polysaccharides such as butadiene rubber, fluorine rubber and polyethylene oxide, a thermoplastic resin, and a polymer having rubber elasticity can be used. Moreover, the compounding quantity of the binder in a positive electrode mixture has a preferable range of 2-30 weight%.

The filler can be used as long as the fibrous material does not cause chemical change in the nonaqueous electrolyte secondary battery, but fibers such as olefin polymers such as polypropylene and polyethylene, glass fibers, and carbon fibers can be used. Although the filler compounding quantity in a positive electrode mixture is not specifically limited, 0-30 weight% is preferable.

In addition, the compounding quantity of the positive electrode active material of lithium cobalt acid of the present invention to the positive electrode mixture is not particularly limited, but is preferably in the range of 60 to 95% by weight, particularly preferably 70 to 94% by weight.

The negative electrode material used for the negative electrode of the nonaqueous electrolyte secondary battery of the present invention is not particularly limited, and examples thereof include a carbonaceous material, a metal composite oxide, a lithium metal or a lithium alloy. Examples of carbonaceous materials include non-graphitizable carbon materials and graphite-based carbon materials. Examples of the metal composite oxide include SnM ¹ _1-x M ² _y O _z (wherein M ¹ represents Mn, Fe, Pb, or Ge). 1 or more selected, M <^2> represents 2 or more types of elements chosen from Al, B, P, Si, periodic table group 1, 2, 3, or a halogen element, and x is 0 <x <1, y represents 1 <y <3, z represents the number in the range of 1 <z <8), etc. are mentioned.

The nonaqueous electrolyte used in the nonaqueous electrolyte secondary battery is, for example, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyl lactone, 1, 2-dimethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1, 3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxymethane At least one or more of aprotic organic solvents such as dioxolane derivatives, sulfolane, 3-methyl-2-oxazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, diethyl ether, and 1,3-propanesultone And a lithium salt dissolved in the solvent, such as LiClO ₄ , LiBF ₄ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiB ₁₀ Cl ₁₀ , LiAlCl ₄ , Chloroborane Lithium, low fat Carboxylic acid is lithium, composed of one or more kinds of lithium salts such as tetraphenyl lithium borate.

In addition to the nonaqueous electrolyte, an organic solid electrolyte can be used. For example, a polyethylene derivative or the polymer containing the same, a polypropylene oxide derivative or the polymer containing the same, a phosphate ester polymer, etc. are mentioned.

The current collector of the electrode is not particularly limited as long as it is an electron conductor which does not cause chemical change in the constructed nonaqueous electrolyte secondary battery. The positive electrode may be formed of, for example, carbon on the surface of stainless steel, nickel, aluminum, titanium, calcined carbon, aluminum or stainless steel. Surface treatment with nickel, copper, titanium or silver is used. As the cathode, for example, stainless steel, nickel, copper, titanium, aluminum, calcined carbon, or the like, the surface of copper or stainless steel treated with carbon, nickel, titanium, silver, or the like, Al-Cd alloy or the like is used.

The shape of the nonaqueous electrolyte secondary battery can be applied to any of coins, buttons, sheets, cylinders, and corners.

The use of the nonaqueous electrolyte secondary battery of the present invention is not particularly limited. Examples thereof include notebook PCs, laptop PCs, pocket word processors, cellular phones, wireless telephones, portable CDs, electronic devices such as radios, automobiles, electric vehicles, and game machines. Public electronic devices, such as these, are mentioned.

[Examples]

Hereinafter, the present invention will be described in more detail with reference to Examples.

In the Examples, the cathode active material and the nonaqueous electrolyte secondary battery of the present invention will be described.

(1) Measuring method of tap density

Dry the measuring cylinder completely and weigh the empty measuring cylinder. Weigh approximately 70 g of the sample on a weak package. Transfer the sample into the measuring cylinder using a funnel. Set the measuring cylinder to the automatic TD measuring device (Dia Auto Tap, manufactured by Yuasa Ionics Co., Ltd.), adjust the tapping frequency to 500, perform the tapping, read the scale of the sample surface, and weigh the measuring cylinder containing the sample. Calculate the tap density. Tapping height 3.2 mm, tapping speed 200 times / minute (according to ASTM: B527-93, 85).

(2) Measuring method of pressure density

The sample is put into a mold having a diameter of 15 mm, and a pellet (1.96 × 10 ⁸ Pa (2ton / cm 2)) press (hand press, Tong Yang Co., Ltd., WPN-10) is performed for 1 minute to obtain pellets. Thereafter, the weight and volume of the pellets are measured, and the density of the pellets is calculated to be a press density.

Preparation Example 1

Lithium carbonate and cobalt oxide were weighed so that the Li / Co atomic ratio was 1.02, and mixed sufficiently in a mortar to prepare a uniform mixture. Subsequently, the mixture was charged into an alumina crucible, placed in an electric heating furnace, heated in an air atmosphere, held at a temperature of 700 ° C. to 1000 ° C. for 10 hours, and calcined, and the resulting fired product was cooled in the air, followed by grinding and classification. By this, lithium cobalt acid (LiCoO ₂ ) having an average particle diameter of 15.5 µm, a tap density of 2.80 g / cm 3, and a press density of 3.45 g / cm 3 was obtained.

This lithium cobaltate was monodisperse lithium cobalt acid (A-1) with a primary particle.

Production Example 2

In the same manner as in Preparation Example 1, lithium carbonate and cobalt oxide were mixed to have a Li / Co atomic ratio of 1.04 to prepare a uniform mixture, and then calcined at 1000 ° C. to 1050 ° C. for 10 hours to obtain an average particle diameter of 12.3 μm and a tap density of 2.50 g /. Lithium cobalt acid (LiCoO ₂ ) having a cm 3 and a press density of 3.48 g / cm 3 was obtained.

The SEM image of this lithium cobalt acid was mono-dispersed lithium cobalt acid (A-2) with a primary particle.

Production Example 3

In the same manner as in Production Example 1, lithium carbonate and cobalt oxide were mixed to have a Li / Co atomic ratio of 1.02 to prepare a uniform mixture, and then calcined at 1000 ° C. to 1050 ° C. for 10 hours to obtain an average particle diameter of 7.8 μm and a tap density of 1.90 g. Lithium cobalt acid (LiCoO ₂ ) having a pressure of 3.41 g / cm 3;

This lithium cobaltate was monodisperse lithium cobalt acid (A-3) with primary particles.

Preparation Example 4

In the same manner as in Production Example 1, lithium carbonate and cobalt oxide were mixed to have a Li / Co atomic ratio of 1.00 to prepare a uniform mixture, and then calcined at 900 ° C to 1000 ° C for 10 hours to obtain an average particle diameter of 7.4 µm and a tap density of 1.80 g. Lithium cobalt acid (LiCoO ₂ ) of / cm 3 and a press density of 3.20 g / cm 3 was obtained.

This lithium cobaltate was lithium cobalt oxide (B-1) in which primary particles were aggregated.

Preparation Example 5

In the same manner as in Preparation Example 1, lithium carbonate and cobalt oxide were mixed to have a Li / Co atomic ratio of 1.00 to prepare a uniform mixture, and then calcined at 900 ° C to 1000 ° C for 10 hours to obtain an average particle diameter of 5.2 µm and a tap density of 1.50 g. Lithium cobalt acid (LiCoO ₂ ) of / 15 cm 3 and a press density of 3.15 g / cm 3 was obtained.

This lithium cobaltate was lithium cobalt oxide (B-2) in which primary particles were aggregated.

Preparation Example 6

In the same manner as in Production Example 1, lithium carbonate and cobalt oxide were mixed to have a Li / Co atomic ratio of 1.00 to prepare a uniform mixture, and then calcined at 800 ° C. to 900 ° C. for 10 hours to obtain an average particle diameter of 3.2 μm and a tap density of 1.20 g. Lithium cobalt acid (LiCoO ₂ ) of / cm 3 and a press density of 3.21 g / cm 3 was obtained.

The SEM image of this lithium cobalt acid was lithium cobalt acid (B-3) which the primary particle aggregated.

Preparation Example 7

In the same manner as in Production Example 1, LiCo _0.98 Al _0.02 O _{2, in} which 2 mol% of Al was added to Co, was synthesized. The firing method was the same as in Preparation Example 1, and mixed Al (OH) ₃ to 2 mol% with respect to Co at the time of induction mixing, and then calcined at 800 to 900 ° C to add Al cobalt acid (LiCo _0.98 Al _0.02 O ₂ ) was obtained.

This lithium cobalt acid had an average particle diameter of 2.8 µm, a tap density of 1.18 g / cm 3, and a press density of 3.19 g / cm 3.

The SEM image of this lithium cobaltate was lithium cobalt oxide (B-4) in which the primary particle aggregated.

In FIG. 1, the SEM photograph (magnification x 3000) which shows the particle | grain structure of monodisperse lithium cobalt acid (A) which the primary particle of the manufacture example 1 prepared.

The SEM photograph (magnification x 3000) which shows the particle | grain structure of the aggregated lithium cobalt acid (B) of manufacture example 7 is shown in FIG.

The lithium cobalt acid (A) and (B) obtained in the said Production Examples 1-7 were put together in Table 1, and were shown.

Lithium cobalt
Average particle size
(Μm) Tap density
(g / cm3) Pressure density
(g / cm3) Preparation Example 1 A-1 Monodispersion 15.5 2.80 3.45 Production Example 2 A-2 Monodispersion 12.3 2.50 3.48 Production Example 3 A-3 Monodispersion 7.8 1.90 3.41 Preparation Example 4 B-1 Cohesion 7.4 1.80 3.20 Preparation Example 5 B-2 Cohesion 5.2 1.50 3.15 Preparation Example 6 B-3 Cohesion 3.2 1.20 3.21 Preparation Example 7 B-4 Cohesion 2.8 1.18 3.19

In the table, (A) represents lithium cobalt (A), and (B) represents lithium cobalt (B).

In the present invention, the pressure density of lithium cobalt (A) is 3.3 to 3.7 g / cm 3, preferably 3.5 to 3.7 g / cm 3. In the present invention, the pressurized density of lithium cobalt (B) is preferably 3.1 to 3.5 g / cm 3, preferably 3.13.3 g / cm 3.

In the present invention, the pressure density difference between lithium cobalt (A) and lithium cobalt (B) is preferably 0.2 g / cm 3 or more, preferably 0.8 to 1.5 g / cm 3.

Example 1

95 parts by weight of lithium cobalt acid (A-1) having an average particle diameter of 15.5 µm and a tap density of 2.80 g / cm 3 obtained in Production Example 1, and lithium cobalt acid having an average particle diameter of 3.2 µm and 1.20 g / cm 3 of a tap density obtained in Production Example 6 5 parts by weight of (B-3) were uniformly mixed with a small ribbon mixer to produce lithium cobalt acid. The average particle diameter of the obtained lithium cobalt acid was 15.0 micrometers, tap density 2.75g / cm <3>, and pressurization density 3.65g / cm <3>.

Example 2

70 parts by weight of lithium cobalt acid (A-1) having an average particle diameter of 15.5 µm and a tap density of 2.80 g / cm 3 obtained in Production Example 1, and lithium cobalt acid having an average particle diameter of 3.2 µm and a tap density of 1.20 g / cm 3 obtained in Production Example 6 (B-3) 30 parts by weight of the mixture was uniformly mixed to prepare lithium cobalt acid. The average particle diameter of the obtained lithium cobalt acid was 11.9 micrometers, tap density 2.40 g / cm <3>, and pressurization density 3.92 g / cm <3>.

Example 3

70 parts by weight of lithium cobalt acid (A-1) having an average particle diameter of 15.5 µm and a tap density of 2.80 g / cm 3 obtained in Production Example 1, and an average particle diameter of 5.2 µm and 1.50 g / cm 3 of lithium cobalate having a tap density of 1.50 g / cm 3. (B-2) 30 parts by weight of the mixture was uniformly mixed to prepare lithium cobalt acid. The average particle diameter of the obtained lithium cobalt acid was 12.8 micrometers, tap density 2.53g / cm <3>, and pressurization density 3.82g / cm <3>.

Example 4

80 parts by weight of lithium cobalt oxide (A-2) having an average particle diameter of 12.3 µm and a tap density of 2.50 g / cm 3 obtained in Production Example 2, and lithium cobaltate having an average particle diameter of 5.2 µm and 1.50 g / cm 3 of a tap density obtained in Production Example 5. (B-2) 20 parts by weight of the mixture was uniformly mixed to prepare lithium cobalt acid. The average particle diameter of the obtained lithium cobalt acid was 10.5 micrometers, tap density 2.40g / cm <3>, and pressurization density 3.75g / cm <3>.                     

Example 5

60 parts by weight of lithium cobalt acid (A-2) having an average particle diameter of 12.3 µm and a tap density of 2.50 g / cm 3 obtained in Production Example 2, and lithium cobalt acid having an average particle diameter of 7.4 µm and a tap density of 1.80 g / cm 3 obtained in Production Example 4. 40 parts by weight of (B-1) were uniformly mixed to prepare lithium cobalt acid. The average particle diameter of the obtained lithium cobalt acid was 10.1 micrometers, tap density 2.35 g / cm <3>, and pressurization density 3.65 g / cm <3>.

Example 6

85 parts by weight of lithium cobalt oxide (A-3) having an average particle diameter of 7.8 μm and a tap density of 1.90 g / cm 3 obtained in Production Example 3, and an average particle diameter of 3.2 μm and 1.20 g / cm 3 of lithium cobalt acid having a tap density of 1.20 g / cm 3. (B-3) 15 parts by weight of the mixture was uniformly mixed to prepare lithium cobalt acid. The average particle diameter of the obtained lithium cobalt acid was 7.0 micrometers, tap density 1.83g / cm <3>, and pressurization density 3.55g / cm <3>.

Example 7

60 parts by weight of lithium cobalt oxide (A-1) having an average particle diameter of 15.5 µm and a tap density of 2.80 g / cm 3 obtained in Production Example 1, and lithium cobalt acid having an average particle diameter of 3.2 µm and a tap density of 1.20 g / cm 3 obtained in Production Example 6 (B-3) 40 parts by weight of the mixture was uniformly mixed to prepare lithium cobalt acid. The average particle diameter of the obtained lithium cobalt acid was 7.8 micrometers, tap density 1.88 g / cm <3>, and pressurization density 3.50 g / cm <3>.

Example 8

70 parts by weight of lithium cobalt oxide (A-1) having an average particle diameter of 15.5 µm and a tap density of 2.80 g / cm 3 obtained in Production Example 1, and an Al-added cobalt of 2.8 µm and a tap density of 1.18 g / cm 3, obtained in Production Example 7 30 parts by weight of lithium acid (LiCo _0.98 Al _0.02 O ₂ ) (B-4) was uniformly mixed to prepare lithium cobalt acid. The average particle diameter of the obtained lithium cobaltate was 7.7 micrometers, tap density 2.38g / cm <3>, and pressurization density 3.89g / cm <3>.

Example 9

90 parts by weight of lithium cobalt acid (A-1) having an average particle diameter of 15.5 µm and a tap density of 2.80 g / cm 3 obtained in Production Example 1, and lithium cobalt acid having an average particle diameter of 3.2 µm and a tap density of 1.20 g / cm 3 obtained in Production Example 6 (B-3) 10 parts by weight of the mixture was uniformly mixed to prepare lithium cobalt acid. The average particle diameter of the obtained lithium cobalt acid was 13.8 micrometers, tap density 2.65g / cm <3>, and pressurization density 3.72g / cm <3>.

Example 10

90 parts by weight of lithium cobalt acid (A-1) having an average particle diameter of 15.5 µm and a tap density of 2.80 g / cm 3 obtained in Production Example 1, and an average particle diameter of 7.4 µm and a lithium density of 1.80 g / cm 3, obtained in Production Example 4 10 parts by weight of (B-1) was uniformly mixed to prepare lithium cobalt acid. The average particle diameter of the obtained lithium cobalt acid was 14.8 micrometers, tap density 2.70g / cm <3>, and pressurization density 3.60g / cm <3>.

Example 11

80 parts by weight of lithium cobalt oxide (A-1) having an average particle diameter of 15.5 µm and a tap density of 2.80 g / cm 3 obtained in Production Example 1, and lithium cobalt acid having an average particle diameter of 3.2 µm and 1.20 g / cm 3 of a tap density obtained in Production Example 6 (B-3) 20 parts by weight of the mixture was uniformly mixed to prepare lithium cobalt acid. The average particle diameter of the obtained lithium cobaltate was 13.2 micrometers, tap density 2.58 g / cm <3>, and pressurization density 3.74 g / cm <3>.

Example 12

80 parts by weight of lithium cobalt oxide (A-1) having an average particle diameter of 15.5 µm and a tap density of 2.80 g / cm 3 obtained in Production Example 1, and an average particle diameter of 7.4 µm and a lithium density of 1.80 g / cm 3, obtained in Production Example 4 (B-1) 20 parts by weight of uniformly mixed to prepare lithium cobalt acid. The average particle diameter of the obtained lithium cobalt acid was 13.8 micrometers, tap density 2.62 g / cm <3>, and pressurization density 3.58 g / cm <3>.

In the said Examples 1-12, the lithium cobaltate obtained by mixing lithium cobalt (A) and (B) is put together in Table 2 and Table 3, and is shown.                     

(A)
Tap density
(g / cm3) (B)
Tap density
(g / cm3) Tap density difference
(g / cm3) Compounding cost
A: B Mixed tap density
(g / cm3) Average particle size
(Μm)  Example 1 2.80
(A-1) 1.20
(B-3) 1.60 95: 5 2.75 15.0  Example 2 2.80
(A-1) 1.20
(B-3) 1.60 70:30 2.40 11.9  Example 3 2.80
(A-1) 1.50
(B-2) 1.30 70:30 2.53 12.8  Example 4 2.50
(A-2) 1.50
(B-2) 1.00 80:20 2.40 10.5  Example 5 2.50
(A-2) 1.80
(B-1) 0.70 60:40 2.35 10.1  Example 6 1.90
(A-3) 1.20
(B-3) 0.70 85:15 1.83 7.0  Example 7 2.80
(A-1) 1.20
(B-3) 1.60 60:40 1.88 7.8  Example 8 2.80
(A-1) 1.18
(B-4) 1.62 70:30 2.38 7.7  Example 9 2.80
(A-1) 1.20
(B-3) 1.60 90:10 2.65 13.8  Example 10 2.80
(A-1) 1.80
(B-1) 1.00 90:10 2.70 14.8  Example 11 2.80
(A-1) 1.20
(B-3) 1.60 80:20 2.58 13.2  Example 12 2.80
(A-1) 1.80
(B-1) 1.00 80:20 2.62 13.8

(A)
Pressure density
(g / cm3) (B)
Pressure density
(g / cm3) Pressure
Density difference
(g / cm3) Compounding cost
A: B mix
Pressure density
(g / cm3) Average particle size
(Μm)  Example 1 3.45
(A-1) 3.21
(B-3) 0.24 95: 5 3.65 15.0  Example 2 3.45
(A-1) 3.21
(B-3) 0.24 70:30 3.95 11.9  Example 3 3.45
(A-1) 3.15
(B-2) 0.30 70:30 3.82 12.8  Example 4 3.48
(A-2) 3.15
(B-2) 0.33 80:20 3.75 10.5  Example 5 3.48
(A-2) 3.20
(B-1) 0.28 60:40 3.65 10.1  Example 6 3.41
(A-3) 3.21
(B-3) 0.20 85:15 3.55 7.0  Example 7 3.45
(A-1) 3.21
(B-3) 0.24 60:40 3.50 7.8  Example 8 3.45
(A-1) 3.19
(B-4) 0.26 70:30 3.89 7.7  Example 9 3.45
(A-1) 3.21
(B-3) 0.24 90:10 3.72 13.8  Example 10 3.45
(A-1) 3.20
(B-1) 0.25 90:10 3.60 14.8  Example 11 3.45
(A-1) 3.21
(B-3) 0.24 80:20 3.74 13.2  Example 12 3.45
(A-1) 3.20
(B-1) 0.25 80:20 3.58 13.8

In the table, A represents lithium cobalt (A) and B represents lithium cobalt (B).

Comparative Example 1

The lithium cobaltate (LiCoO ₂ ) having an average particle diameter of 12.3 μm, a tap density of 2.50 g / cm 3, and a press density of 3.48 g / cm 3 obtained in Production Example 2 is shown as a comparative example.

The SEM image of this lithium cobalt acid is mono-dispersed lithium cobalt acid (A) with a primary particle.

Next, the comparative example of the lithium cobalt oxide obtained when the mixture of lithium cobalt (A) and lithium cobalt (B) is changed in this invention is shown.                     

Preparation Example 8 (Comparative Production Example)

Lithium carbonate and cobalt oxide were mixed to have a Li / Co atomic ratio of 1.00 to prepare a homogeneous mixture, and then calcined by holding at 1000 to 1050 ° C for 10 hours. The resulting calcined product was pulverized and classified in the air to have an average particle size of 4.5. Lithium cobalt acid (LiCoO ₂ ) having a thickness of 1. µm, a tap density of 1.60 g / cm 3, and a press density of 3.25 g / cm 3 was obtained.

This lithium cobaltate was lithium cobalt oxide (C-1) in which primary particles were monodispersed.

Preparation Example 9 (Comparative Production Example)

Lithium carbonate and cobalt oxide were mixed to have a Li / Co atomic ratio of 1.00 to prepare a homogeneous mixture, and then calcined by holding at 800 to 850 ° C. for 10 hours. Lithium cobalt acid (LiCoO ₂ ) having a thickness of 2. μm, a tap density of 2.20 g / cm 3, and a press density of 3.30 g / cm 3 was obtained.

This lithium cobaltate was lithium cobalt oxide (C-2) in which primary particles were aggregated.

Preparation Example 10 (Comparative Production Example)

Lithium carbonate and cobalt oxide were mixed to have a Li / Co atomic ratio of 1.00 to prepare a uniform mixture, and then calcined by holding at 1000 to 1050 ° C. for 10 hours. Lithium cobalt acid (LiCoO ₂ ) having a micrometer, a tap density of 1.32 g / cm 3, and a press density of 3.12 g / cm 3 was obtained.

This lithium cobaltate was lithium cobalt oxide (C-3) in which primary particles were monodispersed.

Comparative Example 2

80 parts by weight of lithium cobalt (C-1) obtained in Production Example 8 and 20 parts by weight of lithium cobalt (B-3) obtained in Production Example 6 were uniformly mixed with a small ribbon mixer to prepare lithium cobalt acid.

The average particle diameter of the obtained lithium cobaltate was 3.5 micrometers, tap density 1.32 g / cm <3>, and pressurization density 3.22 g / cm <3>.

Comparative Example 3

80 parts by weight of lithium cobalt (C-2) obtained in Production Example 9 and 20 parts by weight of lithium cobalt (B-3) obtained in Production Example 6 were uniformly mixed with a small ribbon mixer to prepare lithium cobalt acid.

The average particle diameter of the obtained lithium cobaltate was 11.2 micrometers, tap density 2.15 g / cm <3>, and pressurization density 3.45 g / cm <3>.

Comparative Example 4

80 parts by weight of lithium cobalt (A-1) obtained in Production Example 1 and 20 parts by weight of lithium cobalt (C-2) obtained in Production Example 9 were uniformly mixed with a small ribbon mixer to prepare lithium cobalt acid.

The average particle diameter of the obtained lithium cobalt acid was 11.2 micrometers, tap density 2.56 g / cm <3>, and pressurization density 3.37 g / cm <3>.

Comparative Example 5

80 parts by weight of lithium cobalt (A-1) obtained in Production Example 1 and 20 parts by weight of lithium cobalt (C-3) obtained in Production Example 10 were uniformly mixed with a small ribbon mixer to produce lithium cobalt acid.

The average particle diameter of the obtained lithium cobalt acid was 13.4 micrometers, tap density 2.62 g / cm <3>, and pressurization density 3.40 g / cm <3>.

Comparative Example 6

50 parts by weight of lithium cobalt (A-1) obtained in Production Example 1 and 50 parts by weight of lithium cobalt (B-3) obtained in Production Example 6 were uniformly mixed with a small ribbon mixer to produce lithium cobalt acid.

The average particle diameter of the obtained lithium cobalt acid was 9.5 micrometers, tap density 1.71 g / cm <3>, and pressurization density 3.42 g / cm <3>.

Lithium cobalt Average particle size
(Μm) Tap density
(g / cm3) Pressure density
(g / cm3)  Production Example 2 A-2 Monodispersion 12.3 2.50 3.48  Preparation Example 8 C-1 Monodispersion 4.5 1.60 3.25  Preparation Example 9 C-2 Cohesion 11.0 2.20 3.30  Preparation Example 10 C-3 Monodispersion 5.0 1.32 3.12

(A)
Tap density
(g / cm3) (B)
Tap density
(g / cm3) Tap density difference
(g / cm3) Compounding cost
A: B Mixed tap density
(g / cm3) Average particle size
(Μm)  Comparative Example 1 2.50
(A-2) - - 100 2.50 12.3  Comparative Example 2 1.60
(C-1) 1.20
(B-3) 0.40 80:20 1.32 3.5  Comparative Example 3 2.20
(C-2) 1.20
(B-3) 1.00 80:20 2.15 11.2  Comparative Example 4 2.80
(A-1) 2.20
(C-2) 0.60 80:20 2.56 11.2  Comparative Example 5 2.80
(A-1) 1.32
(C-3) 1.48 80:20 2.62 13.4  Comparative Example 6 2.80
(A-1) 1.20
(B-3) 1.60 50:50 1.71 9.5

(A)
Pressure density
(g / cm3) (B)
Pressure density
(g / cm3) Pressure
Density difference
(g / cm3) Compounding cost
A: B mix
Pressure density
(g / cm3) Average particle size
(Μm)  Comparative Example 1 3.48
(A-2) - - 100 3.48 12.3  Comparative Example 2 3.25
(C-1) 3.21
(B-3) 0.04 80:20 3.22 3.5  Comparative Example 3 3.30
(C-2) 3.21
(B-3) 0.09 80:20 3.45 11.2  Comparative Example 4 3.45
(A-1) 3.30
(C-2) 0.15 80:20 3.37 11.2  Comparative Example 5 3.45
(A-1) 3.12
(C-3) 0.33 80:20 3.40 13.4  Comparative Example 6 3.45
(A-1) 3.21
(B-3) 0.24 50:50 3.42 9.5

Next, the result of the safety evaluation and the rapid charge / discharge test of the secondary battery which used the lithium cobalt acid of this invention as a positive electrode active material is shown.

(Safety Assessment)

Lithium cobalt acid of Example 2 and lithium cobalt acid (A) of Comparative Example 1 were used as positive electrode active materials, respectively. This positive electrode active material was applied onto an aluminum foil, and a lithium ion secondary battery was prepared by using each member such as a separator, a negative electrode, a positive electrode, a current collector, a mounting bracket, an external terminal, and an electrolyte solution using the positive electrode plate. Among them, metal lithium was used as the negative electrode, and an electrolyte solution in which 1 mol of LiPF ₆ was dissolved in 1 liter of a 1: 1 mixed solution of EC (ethylene carbonate) and MEC (ethyl methyl carbonate) was used. After cell preparation, the cells were charged with Li / Li ⁺ 4.3 V, sufficiently washed with acetone and dried. The electrode was sealed in a container with a 1: 1 mixed solution of electrolytic solution EC (ethylene carbonate) and MEC (ethyl methyl carbonate), and then subjected to stability test by DSC measurement. The result is shown in FIG.

From the results of FIG. 3, it can be seen that the first fever peak (near the low temperature side 180 ° C.) of Example 2 is smaller than the first fever peak (near the low temperature side 180 ° C.) of Comparative Example 1, and the heat generation amount is small. It was found that the active material of Example 2 was higher in safety than the active material of Comparative Example 1. In general, particulates have low safety because of their high specific surface area and high reactivity. However, the lithium cobalt oxide of Example 2 also coexists with coarse particles (lithium cobalt acid (A)), whereby the high safety of the coarse particles is effective in eliminating the low safety of fine particles (lithium cobalt acid (B)). I guess that.

(Quick Charge / Discharge Test)

Lithium cobalt acid of Example 2 and lithium cobalt acid (A) of Comparative Example 1 were used as positive electrode active materials, respectively. This positive electrode active material was applied onto an aluminum foil, and a lithium ion secondary battery was prepared by using each member such as a separator, a negative electrode, a positive electrode, a current collector, a mounting bracket, an external terminal, and an electrolyte solution using the positive electrode plate. Among these, metal lithium was used as the negative electrode, and an electrolyte solution in which 1 mol of LiPF ₆ was dissolved in 1 liter of a 1: 1 mixture solution of EC (ethylene carbonate) and MEC (ethyl methyl carbonate) was used.

A constant current charge / discharge test is performed at 2.7 V to 4.3 V (vs. Li / Li ⁺ ), and the charge and discharge curve is shown in FIG. 4. At that time, the current value was increased by 0.2C → 0.5C → 1.0C → 2.0C (discharge at 1.0C → 1 hour, discharge at 2.0C → 0.5 hour) to test the rapid charge / discharge performance. Anode and cathode: Metal Li, electrolyte: 1 MLiPF ₆ / EC + MEC, charging method: CCCV (0.5C, 5H), scanning potential: 2.7V, 4.3V.

4 shows that Example 2 has a larger charge / discharge capacity than Comparative Example 1. This is expected to have good characteristics because the fine particles (lithium cobalt (B)) contained in the lithium cobalt salt of Example 2 were excellent in rapid charge and discharge.

The alleles contribute to high safety, and the small particles can obtain high rapid charge and discharge performance due to the increase in conductivity between the powders entering the gaps of the alleles. However, if the pressurization density is too high (4.0 or more), the electrode density becomes too high when the electrode is used, the impregnation of the electrolyte solution is insufficient, and the rapid charge / discharge performance deteriorates, which is not appropriate. Moreover, sufficient electrode density cannot be obtained unless the press density and tap density are appropriate values.

Next, the pressurized density of the lithium cobalt acid of this invention is demonstrated.

The lithium cobalt salt of the present invention is composed of a mixture of lithium cobalt acid (A) in which primary particles are monodispersed and lithium cobalt acid (B) in which primary particles are aggregated, and the tap density of the mixture is 1.8. g / cm <3> or more, and pressurization density is 3.5-4.0 g / cm <3>.

As a preferred embodiment of the lithium cobalt oxide of the present invention, lithium cobalt oxide (A) having a tap density of 1.7 to 3.0 g / cm 3, a press density of 3.3 to 3.7 g / cm 3, and a tap density of 1.0 to 2.0 g / cm 3 It consists of a mixture with lithium cobalt oxide (B) of 3 cm <3> and a press density of 3.1-3.5 g / cm <3>, and the difference of the tap density of lithium cobalt (A) and lithium cobalt (B) is 0.20 g / cm <3> or more, Lithium cobalt acid having a difference in pressure density of 0.1 g / cm 3 or more is preferable.

As described above, the lithium cobalt oxide of the present invention can obtain a high press density and an appropriate tap density by mixing two different kinds of lithium cobalt oxides, and when used as a cathode active material in a positive electrode plate, the effect of increasing the electrode density is achieved. Can be obtained.

In addition, according to the production method of the present invention, the lithium cobaltate above useful as a cathode active material can be easily obtained.

In addition, according to the present invention, it is good to use the lithium cobalt oxide as a positive electrode active material, it is possible to obtain a nonaqueous electrolyte secondary battery excellent in safety and rapid charge and discharge.

Claims (7)

Lithium cobalt (A) having a tap density of 1.7 to 3.0 g / cm 3 and lithium cobalt oxide (B) having a tap density of 1.0 to 2.0 g / cm 3, in terms of a weight ratio of the above lithium cobalt (A): the lithium cobalt (B) At a ratio of = 95: 5 to 60:40, the cobalt acid (A) and the cobalt acid (B) are mixed so that the tap density difference is 0.20 g / cm 3 or more, and the lithium cobalt acid (A) is The primary particles are monodisperse, and the lithium cobalt (B) is cobalt having a tap density of 1.8 g / cm 3 or more and a press density of 3.5 to 4.0 g / cm 3 using the aggregated primary particles. A method for producing lithium cobalt acid, characterized by producing lithium acid. The method for producing lithium cobalt oxide according to claim 1, wherein the average particle diameter of the lithium cobalt acid (A) is 5 to 30 µm and the average particle diameter of the lithium cobalt acid (B) is 0.1 to 10 µm. The method according to claim 1 or 2, wherein the lithium cobalt acid (A) is a compound represented by the formula (1), the lithium cobalt acid (B) is a compound represented by the formula (1) or a compound represented by the formula (2) Method for producing lithium cobalt acid. <Formula 1> Li _a CoO ₂ (Where a represents a number in the range of 0.2 ≦ a ≦ 1.2.) <Formula 2> Li _a Co _1-y M _y O _2-z (Where M represents at least one element selected from the group consisting of transition metal elements other than Co or elements having atomic number 9 or more, a is 0.2 ≦ a ≦ 1.2, Y is 0 <y ≦ 0.4, and z is 0 ≦ z) Represents a number within the range of ≤ 1.0.) delete delete delete delete

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