KR101184851B1 - Positive Electrode Active Material of Lithium Secondary Battery, Process for Preparing the Same and Lithium Secondary Battery - Google Patents

Abstract

The present invention provides a lithium secondary battery positive electrode active material, a method for producing the same, and a lithium secondary battery capable of improving the cycle characteristics of a lithium secondary battery, a battery capacity at a low temperature even using an inexpensive cobalt raw material.

In addition, the present invention is an average particle size produced by firing a mixture of lithium cobalt oxide particles powder (A) having an average particle diameter of 5 to 30 ㎛ (A) and a mixture of tricobalt tetraoxide and lithium compounds produced by firing a mixture of cobalt oxyhydroxide and lithium compounds. A mixed powder of lithium cobalt sulfate particle powder (B) having an average particle diameter of 0.1 to 10 µm and smaller than the average particle diameter of (A), wherein the blending ratio of (A) and (B) is (A) in weight ratio: A lithium secondary battery positive electrode active material having a (B) of 95: 5 to 60:40 and a tap density of 1.8 to 3.0 g / cm ³ .

Lithium secondary battery positive electrode active material, lithium secondary battery, cobalt oxyhydroxide, lithium compound, lithium cobaltate

Description

Lithium secondary battery positive electrode active material, a method of manufacturing the same and a lithium secondary battery {Positive Electrode Active Material of Lithium Secondary Battery, Process for Preparing the Same and Lithium Secondary Battery}

1 is a SEM photograph showing the particle shape of the monodisperse lithium cobaltate obtained in Preparation Example 5. FIG.

FIG. 2 is an SEM photograph showing the particle shape of lithium cobalt acid containing secondary particles in which primary particles obtained in Production Example 12 are aggregated.

[Document 1] Japanese Unexamined Patent Publication No. 2004-119218

[Document 2] Japanese Unexamined Patent Publication No. 2000-82466

[Document 3] Japanese Unexamined Patent Publication No. 2004-182564

TECHNICAL FIELD The present invention relates to a lithium secondary battery positive electrode active material, a method for producing the same, and particularly a lithium secondary battery having excellent cycle characteristics and high battery capacity even at low temperatures.

Background Art In recent years, as portableization and wirelessization have rapidly progressed in home electronic devices, lithium ion secondary batteries have been put into practical use as power sources for small electronic devices such as laptop personal computers, mobile phones, and video cameras. The lithium ion secondary battery was reported by Mizushima et al. In 1980 that lithium cobalt acid was useful as a positive electrode active material for lithium ion secondary batteries ("Material Research Blue Tin" vol. 15, p783-789 (1980)). Since then, research and development on lithium-based composite oxides have been actively conducted, and many proposals have been made so far.

Japanese Patent Application Laid-Open No. 2004-119218 discloses cobalt acid having an approximately spherical lithium cobalt acid having an average particle diameter D50 of 7 to 20 µm, and an average particle diameter D50 of 10 to 30% of D50 of the large particle diameter of the lithium cobalt acid particle. A positive electrode active material comprising small particle diameter lithium and a mixture of the former / the latter mass ratio of 1/2 to 9/1 has been proposed. Further, the inventors of the present invention firstly provide a positive electrode active material in which the average particle diameter of the lithium composite oxide particles is in the range of 0.1 to 50 µm, and at least two peaks exist in the particle size distribution of the lithium composite oxide particles (Japanese Patent Laid-Open No. 2000-82466 Or a positive electrode active material comprising a mixed powder of lithium cobalt sulfate powder containing a large particle powder and a small particle powder 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 . (Japanese Patent Laid-Open No. 2004-182564).

According to this method, a lithium secondary battery having excellent initial capacity and capacity retention rate can be provided, but some problems such as cycle characteristics and low battery capacity at low temperatures remain. On the other hand, there has been a problem such as soaring raw material prices such as cobalt oxide of cobalt raw materials, and there has been a demand for a lithium secondary battery positive electrode active material capable of imparting excellent battery characteristics by using inexpensive cobalt raw materials.

Accordingly, an object of the present invention is to provide a lithium secondary battery positive electrode active material and a method of manufacturing the same, and a cycle characteristic using the positive electrode active material, which can improve the cycle characteristics of a lithium secondary battery, the battery capacity at a low temperature even using an inexpensive cobalt raw material. The present invention provides an excellent lithium secondary battery having a high battery capacity even at low temperatures.

As a result of intensive studies to solve these problems, the inventors have found that lithium cobalt oxide powder containing large particle powder and small particle powder is a mixed powder, and cobalt oxyhydroxide, which is an inexpensive cobalt raw material, is used as large particle powder. Lithium cobalt oxide particle powder having an average particle diameter produced in a specific range is used, while lithium cobalt acid particle powder having an average particle size produced using tricobalt tetraoxide as a small particle powder is used. The lithium secondary battery using the blending ratio of the small particle powder and the positive electrode active material made from the mixed powder having the tap density within a specific range solves these problems, and finds that the cycle characteristics, especially at low temperatures, have a battery capacity. The invention has been completed.

That is, the first invention to be provided by the present invention is a lithium cobalt oxide particle powder (A) having an average particle diameter of 5 to 30 µm produced by firing a mixture of cobalt oxyhydroxide and a lithium compound, and a mixture of tricobalt tetraoxide and a lithium compound. It is a mixed powder of lithium cobalt carbonate particle powder (B) having an average particle diameter of 0.1 to 10 µm, which is smaller than the average particle diameter of (A), by the firing, and the large particle powder (A) and the small particle The blending ratio of the powder (B) is (A) :( B) = 95: 5 to 60:40 by weight ratio, and the tap density is 1.8 to 3.0 g / cm ³ , which is a lithium secondary battery positive electrode active material.

In addition, a second invention to be provided by the present invention is a lithium cobalt oxide particle powder (A) having an average particle diameter of 5 to 30 µm produced by firing a mixture of cobalt oxyhydroxide and a lithium compound, and a mixture of tricobalt tetraoxide and a lithium compound. Lithium cobalt sulfate particle powder (B) having an average particle diameter of 0.1 to 10 µm and having a mean particle size smaller than the average particle diameter of (A) was obtained by the large particle powder (A) and the small particle powder (B). The lithium secondary powder characterized by mixing so that the compounding ratio of (A) :( B) = 95: 5 to 60:40 by weight ratio, and obtaining the lithium cobalt-acid mixed powder whose tap density is 1.8-3.0 g / cm <^3> . It is a manufacturing method of a battery positive electrode active material.

Moreover, the 3rd invention which this invention intends to provide is a lithium secondary battery using the lithium secondary battery positive electrode active material of said 1st invention.

BEST MODE FOR CARRYING OUT THE INVENTION [

EMBODIMENT OF THE INVENTION Hereinafter, the lithium secondary battery positive electrode active material in embodiment of this invention is demonstrated.

(Large particle powder (A) which is a 1st component)

The large particle powder, which is the first component of the present invention, has an average particle diameter of 5 to 30 µm, preferably 10 to 28 µm, particularly obtained from a laser method particle size distribution measurement produced by firing a mixture of cobalt oxyhydroxide and a lithium compound. Preferably, the lithium cobaltate particle powder has one peak in a particle size distribution of 11.5 to 20 μm. In the present invention, the reason why the average particle diameter of the large particle powder is in the above range is that when the average particle diameter exceeds 30 m, sufficient cycle characteristics cannot be obtained, while when the average particle diameter is less than 5 m, sufficient electrode density cannot be obtained. Because it becomes.

The large particle powder, which is the first component, is also an important requirement that is produced by firing a mixture of cobalt oxyhydroxide and a lithium compound, and the average particle diameter of the above range produced by firing a mixture of tricobalt tetraoxide and a lithium compound as a large particle powder. Compared with the use of lithium cobalt oxide, it is possible to industrially advantageously improve the performance such as cycle characteristics of a lithium secondary battery, battery capacity at low temperatures, and the like by using an inexpensive raw material.

In the present invention, when the primary particles are agglomerated to form secondary particles, the large particle powder that is the first component has an electrode density that is lowered, and an improvement effect of battery performance such as battery capacity at low temperature is not obtained. It is especially preferable that they are so-called non-aggregated monodisperse particles in which the primary particles have a particle shape as it is. Particle shape can be confirmed specifically by a scanning electron microscope (SEM) photograph observation. In addition, this monodisperse state shows that 50% or more of the visual field in SEM is monodisperse particle in conversion of numbers. 1 shows an SEM photograph (magnification × 3000) showing particles of monodisperse lithium cobaltate of Preparation Example 5. FIG. In addition, in this invention, the average particle diameter of the said large particle powder shows the average particle diameter calculated | required basically from the laser method particle size distribution measuring method.

The cobalt oxyhydroxide that can be used is not particularly limited, but the average particle size obtained from the laser particle size distribution measurement method is 5 to 30 µm, preferably 10 to 20 µm, and in most cases, the cobalt oxyhydroxide is 0.1 to 1 µm. It is formed by forming agglomerated secondary particles of primary particles and contains 20% by volume or more of fine particles of 3 μm or less, but in the present invention, the content of particles having a particle size of 3 μm or less is 20% by volume or less in addition to having the above average particle diameter. It is preferable that the fine powder, which is preferably 15% by volume or less, is reduced, and the lithium cobalt oxide produced by the reaction of the cobalt oxyhydroxide and the lithium compound in which the fine powder is reduced can be used for the battery characteristics such as cycle characteristics and battery capacity at low temperatures. You can improve performance further. It is believed that this fine powder derived from cobalt oxyhydroxide remains calcined on the surface of the produced lithium cobalt oxide, and the fine powder promotes the elution of lithium cobalt oxide and is likely to be a deterioration factor of the cycle characteristics of the lithium secondary battery. Because. In addition, content of the said particle | grains of 3 micrometers or less is the value calculated | required by the laser particle distribution measuring method.

Cobalt oxyhydroxide which does not substantially contain such fine powder can be manufactured using a well-known method, and the example shows that cobalt oxyhydroxide which is commercially available is disperse | distributed in water, and it is left still to remove the fine powder which exists in a supernatant liquid. Means may be used.

Examples of the lithium compound used in the method for producing lithium cobalt as the first component include oxides, hydroxides, carbonates, nitrates and organic acid salts of lithium. Among these, industrially inexpensive lithium carbonate is preferable. Moreover, since this lithium compound has good reactivity, when average particle diameter is 0.1-200 micrometers, Preferably it is 2-50 micrometers, it is especially preferable.

Reaction conditions of the cobalt oxyhydroxide and lithium compound, the respective raw materials are mixed so that the cobalt oxyhydroxide and lithium compound is 0.90 to 1.10, preferably 0.95 to 1.05 in the molar ratio (Li / Co) of Li and Co, After obtaining a mixture of cobalt oxyhydroxide and a lithium compound uniformly dispersed, the mixture is calcined at 700 to 1200 ° C, preferably 800 to 1100 ° C for 0.5 to 10 hours, preferably 0.5 to 5 hours. Firing can be performed either in the air or in an oxygen atmosphere, and is not particularly limited. In addition, these baking can be performed as many times as needed.

After baking, it is appropriately cooled, and pulverized and classified as necessary to obtain lithium cobaltate particle powder. In addition, the pulverization carried out as necessary is appropriately performed in the case where the cobalt lithium powder obtained by firing is in the form of a block in which the cobalt lithium powder is softly bonded, but the particles of the lithium cobalt oxide itself have a specific average particle diameter and a BET specific surface area. That is, the obtained lithium cobalt particle powder is a monodisperse particle having an average particle diameter of 5 to 30 µm, preferably 10 to 28 µm, particularly preferably 11.5 to 20 µm, and a BET specific surface area of 0.05 to 1 m ² / g. And preferably 0.05 to 0.55 m ² / g.

(Small particle powder (B) which is a 2nd component)

The small particle powder as the second component has an average particle diameter of 0.1 to 10 탆, preferably 0.1 to 8 탆, particularly preferably 0.1 to 8 탆, particularly preferably obtained by firing a mixture of tricobalt tetraoxide and a lithium compound. It is a lithium cobaltate particle powder which has one peak in particle size distribution of 0.3-8 micrometers. In the present invention, the reason why the average particle diameter of the small particle powder is in the above range is that a sufficient electrode density cannot be obtained when the average particle size exceeds 10 m, while problems in battery safety and the like occur when the average particle size is less than 0.1 m. to be.

The small particle powder as the second component is also an important requirement that is produced by firing a mixture of tricobalt tetraoxide and a lithium compound, and the average particle diameter of the above range produced by firing a mixture of cobalt oxyhydroxide and a lithium compound as a small particle powder. Compared with using lithium cobalt oxide, battery performance such as cycle characteristics and battery capacity at low temperatures can be improved.

In the present invention, the small particle powder serving as the second component has the excellent filling properties, the electrode density can be increased, and the primary particles are agglomerated to form secondary particles. It is especially preferable in that it is high. Agglomeration of primary particles to form secondary particles indicates a state in which the minimum particles are attracted by van der Waals forces and surface charge forces to form a particle shape, specifically, in a scanning electron microscope (SEM) photograph observation. Can be. The powder in which 80% or more of the visual field in the SEM aggregates can be referred to as agglomerated powder. FIG. 2 is a SEM photograph (magnification × 3000) showing the particle structure of lithium cobalt oxide in which primary particles of Preparation Example 12 are aggregated. In addition, in this invention, the average particle diameter of the said small particle powder shows the average particle diameter of the secondary particle calculated | required basically from the laser method particle size distribution measuring method.

Although tricobalt tetraoxide which can be used is not specifically limited, The average particle diameter calculated | required from the laser method particle size distribution measuring method is 0.1-10.0 micrometers, Preferably it is 0.1-8.0 micrometers, Such a commercially available tricobalt tetraoxide can be used.

As a lithium compound used in the manufacturing method of lithium cobalt acid which is this 2nd component, the thing similar to the said lithium compound can be used, Specifically, Lithium oxide, hydroxide, carbonate, nitrate, an organic acid salt etc. are mentioned, Among these, industrially inexpensive lithium carbonate is preferable. Moreover, since this lithium compound has good reactivity, when average particle diameter is 0.1-200 micrometers, Preferably it is 2-50 micrometers, it is especially preferable.

The reaction conditions of the tricobalt tetraoxide and the lithium compound, the respective raw materials are mixed so that the tricobalt tetraoxide and the lithium compound is 0.90 to 1.10, preferably 0.95 to 1.05 in a molar ratio (Li / Co) of Li and Co, After obtaining a mixture of dispersed tricobalt tetraoxide and a lithium compound, the mixture is calcined at 700 to 1200 ° C, preferably 800 to 1100 ° C for 0.5 to 5 hours, preferably 0.5 to 10 hours. Firing can be performed either in the air or in an oxygen atmosphere, and is not particularly limited. In addition, these baking can be performed as many times as needed.

After baking, it is appropriately cooled, and pulverized and classified as necessary to obtain lithium cobaltate particle powder. In addition, the pulverization performed as necessary is appropriately performed in the case where the cobalt lithium powder obtained by firing is in the form of a block in which the cobalt lithium powder is softly bonded, but the lithium cobalt particle powder itself has a specific average particle diameter and a BET specific surface area. That is, the obtained lithium cobalt particle powder has a form in which primary particles are aggregated to form secondary particles, and the average particle diameter of the secondary particles is 0.1 to 10 μm, preferably 0.1 to 8 μm, and the BET specific surface area is 0.3. To 3.5 m ² / g, preferably 0.3 to 1.5 m ² / g.

(Lithium Secondary Battery Positive Electrode Active Material)

The lithium secondary battery positive electrode active material of the present invention is a mixed powder in which the large particle powder (A) as the first component and the small particle powder (B) as the second component are uniformly mixed. The mixing ratio of the large particle powder (A) and the small particle powder (B) is (A) :( B) = 95: 5 to 60:40, preferably 90:10 to 70:30 by weight ratio. In addition, in the present invention, in addition to the blending ratio, the tap density of 1.8 to 3.0 g / cm ³ , preferably 2.0 to 3.0 g / cm ³ , is one of the important requirements, and the lithium secondary of the present invention having such a configuration The battery positive electrode active material can provide excellent cycle characteristics to a lithium secondary battery using the positive electrode active material, and can be a battery having a high capacity even at a low temperature. In addition, the lithium secondary battery positive electrode active material of the present invention has two peaks in the particle size distribution in which the average particle diameter of the above-mentioned (A) is 11.5-28.0 μm, and the average particle diameter of the above-mentioned (B) is 0.1-10 μm. Mixed powder is preferable, and the ratio (A) / (B) of the average particle diameter of said (A) and the average particle diameter of said (B) is 2.0 or more, Preferably it is 2.5-36.0 using the said positive electrode active material It is preferable at the point to provide the lithium secondary battery excellent cycling characteristics, and to make it the battery which has a high capacity | capacitance even at low temperature.

The tap density indicates filling characteristics in a state where the large particle powder (A) and the small particle powder (B) are naturally mixed without being pressurized, and 70 g of the sample is placed in a measuring cylinder, and the measuring cylinder is automatically TD. It is set to a measuring apparatus, and it is calculated | required as tapping frequency 500, tapping height 3.2mm, tapping face 200 times / min as measurement conditions (based on ASTM: B527-93, 85).

In the present invention, the reason for defining the tap density in the above range is that if the tap density is less than 1.8 g / cm ^{3, a} sufficient electrode density cannot be obtained. On the other hand, if the tap density is more than 3.0 g / cm ³ , a battery such as battery capacity at low temperature is used. This is because the performance improvement effect is low.

In addition, in this invention, when the compounding ratio of large particle powder (A) and small particle powder (B) is other than the said range, the improvement effect of battery performance, such as cycling characteristics and battery capacity at low temperature, is low, If the content is smaller than the above range, the effect of sufficient density improvement cannot be obtained. On the other hand, if the content is larger than the above range, it is difficult to obtain sufficient rate characteristics.

In addition to the above properties, the lithium secondary battery positive electrode active material of the present invention has a press density of 3.5 to 4.5 g /, which is an indicator of how the large particle powder (A) and the small particle powder (B) are charged under pressure. When cm ³ , preferably 3.7 to 4.5 g / cm ^{3, the} electrode density may be improved to further improve battery performance such as cycle characteristics and battery capacity at low temperatures.

In addition, the press density was obtained by inserting a sample into a mold having a diameter of 15 mm and pressurizing 1.96 × 10 ⁸ Pa (2 ton / cm ² ) for 1 minute to obtain pellets, and then measuring the weight and volume of the pellets to determine the density of the pellets. It is calculated and calculated.

The lithium secondary battery positive electrode active material of the present invention is a uniform mixed powder containing a predetermined amount of a large particle powder (A) which is basically the first component and a small particle powder (B) which is a second component, and the first component The method of uniformly mixing the phosphorous large particle powder (A) and the small particle powder (B) as the second component is not particularly limited as long as it is an industrially practiced method to obtain a uniform mixture. Specifically, container rotating mixers such as horizontal cylindrical, V, and double cone type, ribbon type, horizontal screw type, puddle type, vertical ribbon type, mara type, planetary motion type, stacked mixer, single-axis reuter type, Henschel mixer Although the method of using container fixing mixers, such as a flow jet mixer, is mentioned, It is not limited to these.

(Lithium secondary battery)

The lithium secondary battery according to the present invention uses the lithium secondary battery positive electrode active material, and includes a nonaqueous electrolyte containing a positive electrode, a negative electrode, a separator, and a lithium salt. The positive electrode is formed by, for example, coating and drying the positive electrode mixture on the positive electrode current collector, and the positive electrode mixture includes a positive electrode active material, a conductive agent, a binder, a filler added as necessary, and the like. In the lithium secondary battery according to the present invention, a mixed powder of lithium cobaltate composed of the above-mentioned large particle powder and small particle powder, which is a positive electrode active material, is uniformly coated on a positive electrode. Therefore, the lithium secondary battery which concerns on this invention does not produce the fall of load characteristics and cycling characteristics especially.

The positive electrode current collector is not particularly limited as long as it is an electron conductor which does not cause chemical change in the battery constituted. For example, carbon, nickel, titanium, silver on the surface of stainless steel, nickel, aluminum, titanium, calcined carbon, aluminum or stainless steel The surface-treated thing etc. are mentioned. The surface of these materials may be oxidized and used, and unevenness may be added to the surface of the current collector by surface treatment. Examples of the form of the current collector include a foil, a film, a sheet, a net, a punched product, a ras body, a porous body, a foam, a fiber group, and a molded product of a nonwoven fabric. Although the thickness of an electrical power collector is not specifically limited, It is preferable to set it as 1-500 micrometers.

It will not specifically limit, if it is an electron conductive material which does not produce a chemical change in the battery comprised as a conductive agent. For example, graphite such as natural graphite and artificial graphite, carbon black such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, conductive fibers such as carbon fiber or metal fiber, fluorinated Conductive materials, such as metal powders, such as carbon, aluminum, and nickel powder, conductive whiskers, such as zinc oxide and potassium titanate, conductive metal oxides, such as titanium oxide, and a polyphenylene derivative, are mentioned, As natural graphite, For example, scaly graphite, scaly graphite, clay graphite, etc. are mentioned. These can be used 1 type or in combination of 2 or more types. The blending ratio of the conductive agent is 1 to 50% by weight, preferably 2 to 30% by weight in the positive electrode mixture.

As a binder, for example, starch, polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, regenerated cellulose, diacetyl cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, Ethylene-propylene-diene trimer (EPDM), sulfonated EPDM, styrene butadiene rubber, fluororubber, tetrafluoroethylene-hexafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene Perfluoroalkyl vinyl ether copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer, polychlorotrifluoroethylene, fluoride Vinylidene-pentafluoropropylene copolymer, propylene-tetrafluoroethylene aerial Sieve, ethylene-chlorotrifluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethylvinylether-tetrafluoroethylene copolymer, ethylene-acrylic acid air Copolymer or (Na ⁺ ) ion crosslinker, ethylene-methacrylic acid copolymer or (Na ⁺ ) ion crosslinker, ethylene-methyl acrylate copolymer or (Na ⁺ ) ion crosslinker thereof, methyl ethylene-methacrylate Polysaccharides, such as a copolymer or its (Na ⁺ ) ion crosslinked body, polyethylene oxide, a thermoplastic resin, a polymer having rubber elasticity, etc. are mentioned, These can be used 1 type or in combination of 2 or more types. In addition, when using the compound containing the functional group which reacts with lithium like polysaccharide, it is preferable to add a compound, such as an isocyanate group, and to inactivate the functional group. The blending ratio of the binder is 1 to 50% by weight, preferably 5 to 15% by weight in the positive electrode mixture.

A filler suppresses volume expansion of a positive electrode in positive mix, and is added as needed. As the filler, any material can be used as long as it is a fibrous material which does not cause chemical changes in the battery constituted. For example, fibers such as olefin polymers such as polypropylene and polyethylene, glass and carbon are used. Although the addition amount of a filler is not specifically limited, 0-30 weight% is preferable in positive mix.

The negative electrode is formed by coating and drying a negative electrode material on a negative electrode current collector. The negative electrode current collector is not particularly limited as long as it is an electron conductor that does not cause chemical change in the battery constituted. For example, carbon, nickel, titanium on the surface of stainless steel, nickel, copper, titanium, aluminum, calcined carbon, copper, or stainless steel And the surface-treated silver, aluminum cadmium alloy, etc. are mentioned. Moreover, the surface of these materials may be oxidized and used, and unevenness may be added to the collector surface by surface treatment. Examples of the form of the current collector include a foil, a film, a sheet, a net, a punched product, a ras body, a porous body, a foam, a fiber group, and a molded product of a nonwoven fabric. Although the thickness of an electrical power collector is not specifically limited, It is preferable to set it as 1-500 micrometers.

Although it does not restrict | limit especially as a negative electrode material, For example, a carbonaceous material, a metal complex oxide, lithium metal, a lithium alloy, a silicon type alloy, a silver type alloy, a metal oxide, a conductive polymer, a chalcogen compound, Li-Co-Ni type Materials, and the like. As a carbonaceous material, a non-graphitizing carbon material, a graphite type carbon material, etc. are mentioned, for example. As the metal composite oxide, for example, _{^{Sn p M 1 1 -p M 2}} q O r ( wherein, M ¹ represents at least one element selected from Mn, Fe, Pb, and Ge, M ² is Al, B , P, Si, at least one element selected from Group 1, 2, 3, and halogen of the periodic table, and represents 0 <p ≦ 1, 1 ≦ q ≦ ₃ , 1 ≦ r ≦ ₈ ), and LixFe ₂ And compounds such as O ₃ (0 ≦ _x ≦ 1) and Li _x WO ₂ (0 ≦ _x ≦ 1). Examples of the metal oxides include GeO, GeO ₂ , SnO, SnO ₂ , PbO, PbO ₂ , Pb ₂ O ₃ , Pb ₃ O ₄ , Sb ₂ O ₃ , Sb ₂ O ₄ , Sb ₂ O ₅ , Bi ₂ O ₃ , Bi ₂ O ₄ , Bi ₂ O _5, etc. may be mentioned. Examples of the conductive polymer include polyacetylene and poly-p-phenylene.

As the separator, an insulating thin film having a large ion permeability and having a predetermined mechanical strength is used. From the organic solvent resistance and hydrophobicity, the sheet | seat and nonwoven fabric which are made from olefinic polymers, such as polypropylene, glass fiber, polyethylene, etc. are used. As a pore size of a separator, what is necessary is just the range useful generally for a battery, for example, 0.01-10 micrometers. As thickness of a separator, what is necessary is just a general battery range, for example, 5-300 micrometers. In addition, when solid electrolytes, such as a polymer, are used as electrolyte mentioned later, a solid electrolyte may also serve as a separator.

The nonaqueous electrolyte containing a lithium salt includes a nonaqueous electrolyte and a lithium salt. As the nonaqueous electrolyte, a nonaqueous electrolyte, an organic solid electrolyte, and an inorganic solid electrolyte are used. As the non-aqueous electrolyte, for example, N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, Methyl acetate, phosphate triester, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone, propylene carbonate The solvent which mixed 1 type, or 2 or more types among aprotic organic solvents, such as a derivative, tetrahydrofuran derivative, diethyl ether, 1, 3- propane sultone, methyl propionate, and ethyl propionate, is mentioned.

Examples of the organic solid electrolyte include polyethylene derivatives, polyethylene oxide derivatives or polymers containing them, polypropylene oxide derivatives or polymers containing them, phosphate ester polymers, polyphosphazenes, polyaziridines, polyethylene sulfides, and polyvinyls. And polymers containing ionic dissociating groups such as alcohols, polyvinylidene fluoride and polyhexafluoropropylene, polymers containing ionic dissociating groups, and mixtures of the above non-aqueous electrolytes.

Nitrides, halides, oxyacids, sulfides and the like of Li may be used as the inorganic solid electrolyte, and examples thereof include Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, LiSiO ₄ , LiSiO ₄ -LiI. LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Li ₄ SiO ₄ -LiI-LiOH, P ₂ S ₅ , Li ₂ S or Li ₂ SP ₂ S ₅ , Li ₂ S-SiS ₂ , Li ₂ S-GeS ₂ , Li ₂ S-Ga ₂ S ₃ , Li ₂ SB ₂ S ₃ , Li ₂ SP ₂ S ₅ -X, Li ₂ S-SiS ₂ -X, Li ₂ S-GeS ₂ -X, Li ₂ S-Ga ₂ S ₃ -X, Li ₂ SB ₂ S ₃ -X (wherein X is one or more selected from LiI, B ₂ S _3, or Al ₂ S ₃ ), and the like.

In addition, when the inorganic solid electrolyte is amorphous (glass), lithium phosphate (Li ₃ PO ₄ ), lithium oxide (Li ₂ O), lithium sulfate (Li ₂ SO ₄ ), phosphorus oxide (P ₂ O ₅ ), lithium borate Oxygen-containing compounds, such as (Li ₃ BO ₃ ), Li ₃ PO _{4 - x} N _{2x / 3} (x is 0 <x <4), Li ₄ SiO _{4 - x} N _{2x / 3} (x is 0 <x <4), compounds containing nitrogen such as Li ₄ GeO _{4 - x} N _{2x / 3} (x is 0 <x <4), Li ₃ BO _{3 - x} N _{2x / 3} (x is 0 <x <3) Can be contained in the inorganic solid electrolyte. By the addition of the compound containing oxygen or the compound containing nitrogen, the gap between the amorphous framework formed can be widened to reduce the interference with the movement of lithium ions, thereby further improving the ion conductivity.

As the lithium salt, those dissolved in the nonaqueous electrolyte are used, for example, LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB ₁₀ Cl ₁₀ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiB ₁₀ Cl ₁₀ , LiAlCl ₄ , CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, (CF ₃ SO ₂ ) ₂ NLi, chloroborane lithium, lower aliphatic lithium carboxylate, lithium tetraphenylborate, imides, etc. The salt which mixed 1 type or 2 or more types is mentioned.

In addition, the compound shown below can be added to a nonaqueous electrolyte for the purpose of improving discharge, a charge characteristic, and a flame retardance. For example, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphate triamide, nitrobenzene derivative, sulfur, quinoneimine dye, N-substituted oxazolidinone and N, N -Substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, polyethylene glycol, pyrrole, 2-methoxyethanol, aluminum trichloride, monomer of conductive polymer electrode active material, triethylenephosphonamide, trialkylphosphine, morpholine And aryl compounds having a carbonyl group, hexamethylphosphoric triamide and 4-alkyl morpholine, bicyclic tertiary amines, oils, phosphonium salts and tertiary sulfonium salts, phosphazenes, carbonate esters, and the like. In addition, halogen-containing solvents such as carbon tetrachloride and ethylene trifluoride may be included in the electrolyte to render the electrolyte nonflammable. In addition, carbon dioxide may be included in the electrolyte to make it suitable for high temperature storage.

The lithium secondary battery according to the present invention is a lithium secondary battery having excellent battery performance and cycle characteristics, and having a high capacity even at low temperatures, and the shape of the battery may be any shape among buttons, sheets, cylinders, corners, coin shapes, and the like. .

Although the use of the lithium secondary battery which concerns on this invention is not specifically limited, For example, a notebook personal computer, a laptop personal computer, a pocket word processor, a mobile telephone, a wireless handset, a portable CD player, a radio, a liquid crystal television, a backup power supply, an electric shaver , Electronic devices such as memory cards and video movies, and consumer electronic devices such as automobiles, electric vehicles, and game devices.

<Examples>

Next, the present invention will be described in more detail with reference to Examples, which are merely illustrative and do not limit the present invention.

<Production of oxycobalt hydroxide>

Sample 1

100 g of pure water was added to 30 g of commercially available cobalt oxyhydroxide (average particle diameter 10.5 mu m, content of particles having a particle size of 3 mu m or less 25.1 vol%) for 2 hours. Subsequently, after removing the supernatant liquid containing microparticles | fine-particles, cobalt oxyhydroxide was collect | recovered and dried, and this was made into the cobalt oxyhydroxide sample.

Sample 2

100 g of pure water was added to 30 g of commercially available cobalt oxyhydroxide (average particle diameter 14.1 mu m, content of 21.8 vol% of particles having a thickness of 3 mu m or less), and the mixture was left to stand for 2 hours. Subsequently, after removing the supernatant liquid containing microparticles | fine-particles, cobalt oxyhydroxide was collect | recovered and dried, and this was made into the cobalt oxyhydroxide sample.

<Production of lithium cobalt acid>

<Manufacture example 1>

Lithium carbonate (average particle diameter: 10 µm) and the cobalt oxyhydroxide sample 1 prepared above were mixed so that the atomic ratio of Li / Co was 1.01 to prepare a uniform mixture, and calcined at 850 ° C for 10 hours, and the calcined product was pulverized. And cobalt oxide having an average particle diameter of 12.2 µm was obtained.

<Manufacture example 2>

Lithium cobalt oxide having an average particle diameter of 17.7 µm was obtained in the same manner as in Production Example 1, except that Sample 2 was used instead of Sample 1 as cobalt oxyhydroxide.

<Manufacture example 3>

Lithium carbonate (average particle diameter: 10 mu m) and cobalt oxyhydroxide sample 1 prepared above were mixed so that the atomic ratio of Li / Co was 1.05 to prepare a homogeneous mixture, which was calcined at 950 DEG C for 10 hours, and the calcined product was pulverized. And cobalt oxide having an average particle diameter of 14.1 µm was obtained.

&Lt; Preparation Example 4 &

Lithium cobalt oxide having an average particle diameter of 19.1 µm was obtained in the same manner as in Production Example 3, except that Sample 2 was used instead of Sample 1 as cobalt oxyhydroxide.

Production Example 5

Lithium carbonate (average particle diameter: 10 mu m) and the cobalt oxyhydroxide sample 1 prepared above were mixed so that the atomic ratio of Li / Co was 1.04, to prepare a uniform mixture, and calcined at 1000 DEG C for 3 hours, and the calcined product was pulverized. And cobalt oxide having an average particle diameter of 15.0 µm was obtained.

<Manufacture example 6>

Lithium cobalt oxide having an average particle diameter of 19.8 µm was obtained in the same manner as in Production Example 5, except that Sample 2 was used instead of Sample 1 as cobalt oxyhydroxide.

<Manufacture example 7>

Lithium carbonate (average particle diameter: 10 mu m) and the cobalt oxyhydroxide sample 1 prepared above were mixed so that the atomic ratio of Li / Co was 0.98 to prepare a homogeneous mixture, which was calcined at 1080 DEG C for 10 hours, and the calcined product was pulverized. And cobalt oxide having an average particle diameter of 12.0 µm was obtained.

<Manufacture example 8>

Lithium cobalt oxide having an average particle diameter of 17.2 µm was obtained in the same manner as in Production Example 7, except that Sample 2 was used instead of Sample 1 as cobalt oxyhydroxide.

<Manufacture example 9>

Lithium carbonate (average particle diameter: 10 mu m) and cobalt oxyhydroxide sample 1 prepared above were mixed so that the atomic ratio of Li / Co was 1.06 to prepare a uniform mixture, and calcined at 1050 DEG C for 10 hours, and the fired product was pulverized. And cobalt oxide having an average particle diameter of 24.2 µm was obtained.

Production Example 10

Lithium cobalt oxide having an average particle diameter of 27.1 µm was obtained in the same manner as in Production Example 9, except that Sample 2 was used instead of Sample 1 as cobalt oxyhydroxide.

Production Example 11

Lithium carbonate (average particle diameter: 0.1 µm) and commercially available tricobalt tetraoxide (average particle diameter: 0.1 µm) were mixed so that the atomic ratio of Li / Co was 0.90 to prepare a uniform mixture, and calcined at 700 DEG C for 10 hours. It was pulverized and classified to obtain lithium cobaltate having an average particle diameter of 0.5 mu m.

Production Example 12

Lithium carbonate (average particle diameter 10 µm) and commercially available tricobalt tetraoxide (average particle diameter 0.1 µm) were mixed so that the atomic ratio of Li / Co was 1.00, to prepare a uniform mixture, and calcined at 770 ° C for 10 hours. It was pulverized and classified to obtain lithium cobaltate having an average particle diameter of 1.7 mu m.

Production Example 13

Lithium carbonate (average particle diameter 10 µm) and commercially available tricobalt tetraoxide (average particle diameter 2.0 µm) were mixed so that the atomic ratio of Li / Co was 1.01 to prepare a homogeneous mixture, which was calcined at 830 ° C for 10 hours. It was pulverized and classified to obtain lithium cobaltate having an average particle diameter of 3.3 mu m.

Production Example 14

Lithium carbonate (average particle diameter 10 µm) and commercially available tricobalt tetraoxide (average particle diameter 4.0 µm) were mixed so that the atomic ratio of Li / Co was 1.02 to prepare a homogeneous mixture, which was calcined at 880 DEG C for 10 hours. It was pulverized and classified to obtain lithium cobaltate having an average particle diameter of 7.8 mu m.

Production Example 15

Lithium carbonate (average particle diameter: 10 mu m) and commercially available tricobalt tetraoxide (average particle diameter: 5.1 mu m) were mixed so that the atomic ratio of Li / Co was 1.045, to prepare a uniform mixture, and calcined at 980 DEG C for 10 hours. It was pulverized and classified to obtain lithium cobalt oxide having an average particle diameter of 9.8 µm.

Production Example 16

Lithium carbonate (average particle diameter: 10 mu m) and cobalt oxyhydroxide sample 2 prepared above were mixed so that the atomic ratio of Li / Co was 1.05 to prepare a homogeneous mixture, which was calcined at 850 DEG C for 10 hours, and pulverized the fired product. And cobalt oxide having an average particle diameter of 6.8 µm was obtained.

<Examples 1 to 10 and Comparative Examples 1 to 9>

The lithium cobalt acid samples prepared above were uniformly mixed by a small ribbon mixer so as to have a blending ratio shown in Table 3 below to prepare a positive electrode active material sample, and the tap density and the press density were measured by the following method. The results are shown in Table 3.

(Measurement method of tap density)

Dry the measuring cylinder completely, and measure the weight of the empty measuring cylinder. Add approximately 70 g of sample to the drug package. Transfer the sample into the measuring cylinder using a funnel. Set the measuring cylinder to an automatic TD measuring device (manufactured by Yuasa Ionics, Dual Auto Tap), adjust the number of taps to 500, and tap, read the scale on the sample surface to determine the weight of the measuring cylinder containing the sample. Measure to calculate tap density. Tapping height 3.2 mm, tapping face 200 times / minute (ASTM: based on B527-93, 85).

(Measurement method of pressure density)

The sample is placed in a mold having a diameter of 15 mm, and pressurized (hand press, manufactured by Toyo Shoko Co., Ltd., WPN-10) at 1.96 × 10 ⁸ Pa (2 tons / cm ² ) for 1 minute to obtain pellets. Thereafter, the weight and volume of the pellets are measured to calculate the density of the pellets and to be the press density.

<Battery performance test>

(1) Preparation of Lithium Secondary Battery:

91 wt% of the positive electrode active material powders obtained in Examples 1 to 10 and Comparative Examples 1 to 9, 6 wt% of graphite powder, and 3 wt% of polyvinylidene fluoride were mixed to form a positive electrode agent, which was N-methyl-2-pyrroli. A kneading paste was prepared by dispersing in dinon. After apply | coating the said kneading paste to aluminum foil, it was dried and pressurized and punched by the disk of diameter 15mm, and the positive electrode plate was obtained.

The lithium secondary battery was manufactured using each member, such as a separator, a negative electrode, a positive electrode, a collector plate, a mounting bracket, an external terminal, and electrolyte solution using this positive electrode plate. Among them, metal lithium foil was used as the negative electrode, and 1 mol of LiPF ₆ was dissolved in 1 liter of a 1: 1 kneading solution of ethylene carbonate and methyl ethyl carbonate.

(2) performance evaluation of battery

The lithium secondary battery thus produced was operated at room temperature 25 ° C. or −20 ° C. under the following conditions to evaluate the following battery performance.

<Evaluation of Cycle Characteristics>

The coin-type nonaqueous electrolyte secondary battery thus produced was operated at each temperature to evaluate capacity retention. First, the positive electrode is charged to 4.3 V over 5 hours at 0.5 C by constant current voltage (CCCV) charging, and then charged and discharged to discharge at 0.2 C to 2.7 V at a discharge rate of 0.2 C, and these operations are made into one cycle and one cycle. Each discharge capacity was measured. Subsequently, 20 cycles of charge and discharge in the measurement of the discharge capacity were performed, and the capacity retention rate was calculated by the following equation. The results are shown in Table 4 below.

Capacity retention rate (%) = (discharge capacity at 20th cycle) x 100 / (discharge capacity at 1st cycle)

<Evaluation of low temperature characteristic>

The coin-type nonaqueous electrolyte secondary battery thus produced was operated at room temperature 25 ° C. to evaluate the discharge capacity. First, the positive electrode was charged to 4.3 V over 5 hours at 0.5 C by constant current voltage (CCCV) charging, and then discharged and discharged at -20 ° C to 2.7 V at a discharge rate of 0.2 C, and the discharge capacity was measured. . The results are shown in Table 4.

It was found that the active materials obtained in Examples 1 to 10 had a higher capacity even in the low temperature zone than the active materials obtained in Comparative Examples 1 to 9.

The present invention is a lithium secondary battery positive electrode active material manufactured mainly using cobalt oxyhydroxide, which is an inexpensive raw material, and the lithium secondary battery using the positive electrode active material exhibits excellent cycle characteristics compared to conventional lithium cobalt acid as a positive electrode active material. It is excellent in the cycle characteristics which can be provided and the battery which has a high capacity | capacitance even at low temperature, and has a high battery capacity even at low temperature.

Claims (6)

Lithium cobalt oxide particle powder (A) having an average particle diameter of 5 to 30 µm produced by calcining a mixture of cobalt oxyhydroxide and a lithium compound, and an average particle size produced by firing a mixture of tricobalt tetraoxide and lithium compound is 0.1 to 10 µm. , A mixed powder of lithium cobalt sulfate particle powder (B) having an average particle diameter smaller than the average particle diameter of (A), wherein a blending ratio of the large particle powder (A) and the small particle powder (B) is (A) : (B) = 95: 5 to 60:40, and a tap density of 1.8 to 3.0 g / cm ³ , a lithium secondary battery positive electrode active material. The lithium secondary battery positive electrode active material according to claim 1, wherein the cobalt oxyhydroxide is a particle powder having an average particle diameter of 5 to 30 µm and a content of particles of 3 µm or less of 20 vol% or less. The lithium secondary battery positive electrode active material according to claim 1, wherein the press density is 3.5 to 4.5 g / cm ³ . Lithium cobalt oxide particle powder (A) having an average particle diameter of 5 to 30 µm produced by calcining a mixture of cobalt oxyhydroxide and a lithium compound, and an average particle size produced by firing a mixture of tricobalt tetraoxide and lithium compound is 0.1 to 10 µm. The blending ratio of the lithium cobalt sulfate particle powder (B) having an average particle diameter smaller than the average particle diameter of (A) with the large particle powder (A) and the small particle powder (B) is (A) :( B) in a weight ratio. = 95: 5 to 60: 40, so as to mix, to obtain a lithium cobalt acid mixed powder having a tap density of 1.8 to 3.0 g / cm ³ , characterized in that the lithium secondary battery positive electrode active material production method. The method for producing a lithium secondary battery positive electrode active material according to claim 4, wherein the cobalt oxyhydroxide is a particle powder having an average particle diameter of 5 to 30 µm and a content of 3 µm or less particles of 20 vol% or less. The lithium secondary battery positive electrode active material in any one of Claims 1-3 was used, The lithium secondary battery characterized by the above-mentioned.

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