JP2006139945A - Reformed lithium manganese complex oxide, manufacturing method of the same, lithium secondary battery cathode activator composition, and lithium secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reformed lithium manganese complex oxide useful as a lithium secondary battery cathode activator composition, a manufacturing method of the same, a lithium secondary battery cathode activator composition, and a lithium secondary battery excellent in battery characteristics, especially over discharge characteristics, preservation characteristics, and thermal stability characteristics. <P>SOLUTION: On the reformed lithium manganese complex oxide, the surface of a particle of the lithium manganese complex oxide expressed by general formula; Li<SB>x</SB>MnO<SB>2</SB>(1) (wherein, x fulfills 0.9≤x≤1.1) is covered by at least one or more chemicals selected from among acidic phosphate or organic compound having chelating ability. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a modified lithium manganese composite oxide particularly useful as a positive electrode secondary active material, a method for producing the same, a lithium secondary battery positive electrode active material composition, and a lithium secondary battery.

  In recent years, as home appliances have become portable and cordless, lithium ion secondary batteries have been put to practical use as power sources for small electronic devices such as laptop computers, mobile phones, and video cameras. Regarding this lithium ion secondary battery, in 1980, Mizushima et al. Reported that lithium cobalt oxide was useful as a positive electrode active material for lithium ion secondary batteries ("Material Research Bulletin" vol15, P783-789 (1980)). ) Has been actively researched and developed on lithium-based composite oxides, and many proposals have been made so far.

  However, in a lithium secondary battery using a lithium-based composite oxide as a positive electrode active material, a copper foil used as a negative electrode current collector elutes in the electrolyte during overdischarge, and a part of it is deposited on the positive electrode. As a result, there is a problem that charge / discharge characteristics are likely to deteriorate. For this reason, a method of preventing an overdischarge itself by providing an electric circuit for preventing overdischarge on the outside of the battery is used. However, since an electric circuit for preventing overdischarge exists, an apparatus or a battery using the battery Costs such as packs increase.

On the other hand, a method has also been proposed in which a lithium-based composite oxide such as LiCoO _{2 is} used as a main active material and LiMnO ₂ is added as a secondary active material to the main active material (see, for example, Patent Document 1). This LiMnO ₂ is manufactured by firing a lithium compound and a manganese compound in an inert gas atmosphere. However, in a lithium secondary battery using LiMnO ₂ obtained in this way as a positive electrode secondary active material, overdischarge is caused. Although the characteristics are improved to some extent, there is a problem that the battery storage characteristics such as an increase in the internal pressure of the battery due to gas generation are degraded. JP 2000-133272 A (Patent Document 2) and JP 2000-264636 A (Patent Document 3) describe a modified lithium manganese composite oxide obtained by surface-treating a lithium manganese composite oxide with a coupling agent. Although disclosed, there is no disclosure or suggestion about organic compounds having phosphate ester or chelating ability.
JP-A-6-349493 (Claim 1, paragraph number 0007) JP 2000-133272 A (Claim 1, paragraph numbers 0015 and 0016) JP 2000-264636 A (Claim 1, paragraph numbers 0020, 0023)

  Accordingly, an object of the present invention is to solve the above-described conventional problems, and to provide a modified lithium manganese composite oxide useful as a lithium secondary battery positive electrode active material composition, a method for producing the same, a lithium secondary battery positive electrode active An object of the present invention is to provide a lithium secondary battery excellent in material composition and battery performance, in particular, overdischarge characteristics, battery storage characteristics and battery thermal stability.

  In such a situation, the present inventors have conducted extensive research and coating the particle surface of the lithium manganese composite oxide with at least one agent selected from an acidic phosphate ester or an organic compound having a chelating ability. Lithium secondary battery using a positive electrode active material composition containing a lithium manganese composite oxide having a reduced pH, and having the coated lithium manganese composite oxide is particularly excellent in overdischarge characteristics. The inventors have found that the generation of gas is suppressed, the battery storage characteristics are excellent, and the battery thermal stability is also excellent, and the present invention has been completed.

That is, the first invention to be provided by the present invention is the following general formula (1) or the following general formula (2); Li _x MnO ₂ (1)
Li _y Mn ₂ O ₄ (2)
(Wherein x represents 0.9 ≦ x ≦ 1.1, and y represents 0 <y <2). The organic compound in which the particle surface of the lithium manganese composite oxide has acidic phosphate ester or chelate ability A modified lithium manganese composite oxide, characterized in that it is coated with at least one agent selected from the group consisting of:

The second invention provided by the present invention is the following general formula (1) or the following general formula (2); Li _x MnO ₂ (1)
Li _y Mn ₂ O ₄ (2)
(Wherein x represents 0.9 ≦ x ≦ 1.1 and y represents 0 <y <2) and is selected from a lithium manganese composite oxide and an acidic phosphate ester or an organic compound having a chelating ability. A method for producing a modified lithium manganese composite oxide comprising contacting at least one drug.

  A third invention to be provided by the present invention is a lithium secondary battery positive electrode active material composition comprising the modified lithium manganese composite oxide of the first invention.

  A fourth invention to be provided by the present invention is a lithium secondary battery using the positive electrode active material composition of the lithium secondary battery according to the third invention.

  The modified lithium manganese composite oxide of the present invention is a modified lithium manganese composite oxide useful as a lithium secondary battery positive electrode active material composition, and a lithium secondary battery positive electrode active containing the modified lithium manganese composite oxide A lithium secondary battery using the material composition is excellent in battery performance, in particular, overdischarge characteristics, battery storage characteristics, and battery thermal stability.

Hereinafter, the present invention will be described based on preferred embodiments thereof. The modified lithium manganese composite oxide of the present invention has the following general formula (1) or the following general formula (2);
Li _x MnO ₂ (1)
Li _y Mn ₂ O ₄ (2)
(Wherein x represents 0.9 ≦ x ≦ 1.1, and y represents 0 <y <2). The organic compound in which the particle surface of the lithium manganese composite oxide has acidic phosphate ester or chelate ability It is coated with at least one drug selected from The modified lithium manganese composite oxide of the present invention can be used as a positive electrode active material or a secondary electrode active material for a lithium secondary battery. In the present invention, the particle surface of the lithium manganese composite oxide includes the surface of primary particles or aggregated particles in which primary particles are aggregated.

(Lithium manganese composite oxide)
As a preferable physical property of the lithium manganese composite oxide represented by the general formula (1) or the general formula (2) to be modified, an average particle size is 1.0 to 30.0 μm, preferably 2.0 to 15. A thickness of 0 μm is preferable because it can prevent performance degradation due to aggregation of particles and internal short circuit due to coarse particles. The average particle diameter is determined by a laser particle size distribution measuring method (hereinafter, the average particle diameter is a value determined by this measuring method).

  The lithium manganese composite oxide may be primary particles or aggregated particles in which primary particles are aggregated.

Further, BET specific surface area of the lithium manganese composite oxide, 0.1~10.0m ² / g, preferably from 0.4~2.0m ² / g. It is preferable that the BET specific surface area be within this range because the battery thermal stability of a lithium secondary battery using the resulting modified lithium manganese composite oxide as the positive electrode active material composition is good.

In the present invention, the lithium manganese composite oxide to be modified is, in particular, a lithium manganese composite oxide represented by the general formula (1). This is preferable in that excellent battery performance such as overdischarge characteristics, battery storage characteristics, and battery thermal stability can be imparted. The lithium manganese composite oxide to be modified may be obtained by any manufacturing method. For example, with respect to the lithium manganese composite oxide represented by the general formula (1), a lithium compound such as lithium carbonate and lithium hydroxide and a manganese compound such as manganese oxide and manganese carbonate may be combined with a Li atom and Mn. The molar ratio of atoms (Li / Mn) is 0.9 to 1.1, preferably 0.98 to 1.02, and the mixture is then mixed in the atmosphere, oxygen atmosphere or inert atmosphere to 600 to A method of baking at 1100 ° C., preferably 800 to 1000 ° C. for 2 to 20 hours, preferably 5 to 10 hours, and after cooling, cooling appropriately, and pulverizing and classifying as necessary, or lithium such as lithium carbonate and lithium hydroxide A compound and a manganese compound such as manganese oxide and manganese carbonate in a molar ratio of Li atom to Mn atom (Li / Mn) of 0.9 to 1.1, preferably 0.98 to 1.0 Then, the mixture is supplied with oxygen or air to a firing furnace, and the oxygen content is set to 1% by volume or more, preferably 5 to 20% by volume, and 800 to 1100 ° C., preferably 900 to 1000 ° C. Li ₂ MnO ₃ and LiMn ₂ O ₄ lithium-manganese composite oxides having excellent reactivity with lithium compounds after firing for 3 hours or more, preferably 5 to 20 hours, and irreversibly in the reaction A mixture of Mn ₃ O ₄ and manganese oxide produced (hereinafter referred to as “reaction precursor”) is produced, and then the oxygen content such as inert gas or vacuum is 1000 ppm or less, preferably The reaction precursor is calcined in an atmosphere of 600 ppm or less at 800 to 1100 ° C., preferably 900 to 1000 ° C. for 3 hours or more, preferably 5 to 20 hours. Converted to the lithium manganese composite oxide represented by 1), if necessary grinding, and a method of classifying the like.

(Modified lithium manganese oxide)
The modified lithium manganese composite oxide of the present invention is such that the particle surface of the lithium manganese composite oxide is coated with at least one agent selected from an acidic phosphate ester or an organic compound having a chelating ability. is there. Thereby, a side reaction between the modified lithium manganese composite oxide and the electrolytic solution can be suppressed, and for example, generation of gas can be suppressed.

  Examples of the acidic phosphate ester include, for example, methyl acid phosphate, dimethyl acid phosphate, ethyl acid phosphate, diethyl acid phosphate, methyl ethyl acid phosphate, normal- or iso-propyl acid phosphate, positive- or iso-dipropyl acid phosphate. , Methyl butyl acid phosphate, ethyl butyl acid phosphate, propyl butyl acid phosphate, positive- or iso-octyl acid phosphate, positive- or iso-dioctyl acid phosphate, positive-decyl acid phosphate, positive-didecyl acid phosphate, positive-lauryl Acid phosphate, normal-dilauryl acid phosphate, positive- or iso-cecil acid phosphate Positive - or iso - di Cecil acid phosphates, positive - stearyl acid phosphate, positive - or iso - distearyl acid phosphate, allyl acid phosphate, diallyl acid phosphate, and di-butyl acid phosphate. Moreover, the alkali metal salt of these compounds may be sufficient. Of these acidic phosphate esters, methyl acid phosphate, ethyl acid phosphate, and iso-propyl acid phosphate are preferred because they are liquid at room temperature and can be easily coated.

  Examples of the organic compound having chelating ability include phosphonic acid, oxyphenols, amino alcohol, carboxylic acid, hydroxycarboxylic acid, aminocarboxylic acid, oxyaldehyde, amino acid, β-diketone, β-ketone acid and salts thereof. These may be used alone or in combination of two or more.

  Typical examples of the phosphonic acid include alkylphosphonic acid, arylphosphonic acid, aminoalkylenephosphonic acid, ethylenediaminetetraalkylenephosphonic acid, alkyl-1-hydroxy-1,1-diphosphonic acid, and 2-hydroxyphosphonoacetic acid. Compound. Among these, examples of the aminoalkylenephosphonic acid include nitrilotristyrene phosphonic acid, nitrilotrisporopylenephosphonic acid, nitrilodiethylmethylenephosphonic acid, nitrilopropylbismethylenephosphonic acid, and the like. Examples of the ethylenediaminetetraalkylenephosphonic acid include ethylenediaminetetramethylenephosphonic acid, ethylenediaminetetraethylenephosphonic acid, ethylenediaminetetrapropylenephosphonic acid, and the like. Examples of the alkyl-1-hydroxy-1,1-diphosphonic acid include methane-1-hydroxy-1,1-diphosphonic acid, ethane-1-hydroxy-1,1-diphosphonic acid, and propane-1-hydroxy-1 , 1-diphosphonic acid and the like. Also, alkali metal salts of these compounds may be used.

  Examples of β-ketonic acid include acetylacetone, benzoylacetone, stearoylacetone, stearoylbenzoylmethane, and dibenzoylmethane.

  Of these organic compounds having chelating ability, phosphonic acid and β-ketonic acid are preferred because of their high chelating ability for Mn.

  The coating amount of the drug is 0.1 to 15.0% by weight, preferably 0.2 to 10.0% by weight, more preferably 0.3 to 5.0% by weight, based on the weight of the modified lithium manganese composite oxide. It is. The reason for this is that if the coating amount is less than 0.1% by weight, the surface cannot be sufficiently coated, so that a sufficient modification effect cannot be obtained. This is not preferable because the quality effect almost reaches saturation and tends to cause deterioration of battery performance and powder characteristics due to excessive chemicals.

As a preferable physical property of the modified lithium manganese composite oxide itself of the present invention, the average particle size is 1.0 to 30.0 μm, preferably 2.0 to 15.0 μm. The reason for this is that if the average particle size is less than 1.0 μm, the electrode tends to be locally non-uniform due to the aggregation of the particles, so that the performance tends to decrease. This is because there is a fear of breaking through the body or causing the internal short circuit by breaking through the separator during winding. Further, BET specific surface area of 0.1~10.0m ² / g, preferably 0.4~2.0m ² / g, when the BET specific surface area is 0.1~10.0m ² / g It is particularly preferable in that the response to a high load is good and the elution of Mn can be suppressed.

  The modified lithium manganese composite oxide was obtained by adding 100 g of pure water to 5 g of the modified lithium manganese composite oxide powder, stirring the mixture at 25 ° C. for 5 minutes, and then measuring the pH of the supernatant with a pH meter. When the value is less than 11, preferably 9.0 to 10.7, it is preferable in that gas generation during high temperature storage can be further suppressed.

  The modified lithium manganese composite oxide of the present invention is produced by bringing the lithium manganese composite oxide into contact with at least one agent selected from the acidic phosphate ester or an organic compound having a chelating ability. Can do.

  As a specific contact method, a method in which a solution in which the drug is dissolved in a solvent and the lithium manganese composite oxide are contacted in a wet manner, or the powder in the form of a powder is the lithium manganese composite oxide. Examples thereof include a method of contacting by dry method and heating to the melting point or higher of the drug as necessary, and a method of directly contacting the lithium manganese composite oxide when the drug is liquid. In the present invention, these contacts may be performed during or after the preparation of the positive electrode material described later.

  In the present invention, in particular, a solution containing at least one agent selected from the lithium manganese composite oxide represented by the general formula (1) or the general formula (2) and an acidic phosphate ester or an organic compound having a chelating ability; And then drying is particularly preferable because the surface of the lithium manganese composite oxide particles can be uniformly coated with the agent with stable quality.

  The solution containing at least one drug selected from the acidic phosphate ester or the organic compound having chelating ability is a solvent containing at least one drug selected from the acidic phosphate ester or the organic compound having chelating ability. It is a solution dissolved in

  The solvent that can be used is not particularly limited as long as the lithium manganese composite oxide can be slurried and can dissolve the chemical and is inert to the lithium manganese composite oxide and the chemical. For example, alcohol solvents such as methanol, ethanol, and propanol, benzene, toluene, and the like can be used. These solvents can be used alone or in combination of two or more.

  As a method of bringing the lithium manganese composite oxide into contact with the solution containing at least one drug selected from the acidic phosphate ester or an organic compound having a chelating ability, the lithium manganese composite oxide may be used as the drug. Examples thereof include a method of adding a slurry containing the lithium manganese composite oxide dispersed in the solvent and adding the chemical to the solution.

  In the contact operation, the amount of each raw material is 0.05 to 2.0 parts by weight, preferably 0.2 to 1.0 parts by weight with respect to 100 parts by weight of the lithium manganese composite oxide, By adjusting the concentration of each raw material so that the solvent is 50 to 500 parts by weight, preferably 70 to 300 parts by weight, the chemical modification can be performed uniformly, and the solvent can be removed in a short time. It is preferable at the point which can do.

  As long as the contact temperature is within a temperature range where the solution does not solidify or boil, the modification treatment can be performed without any particular problem. However, if the temperature is around room temperature, a special heating / cooling device is not required. is there. The contact time is not particularly limited, and 1 minute to 30 minutes, preferably 2 minutes to 10 minutes is sufficient.

  Next, after solid-liquid separation by a conventional method, drying is performed, and if necessary, pulverization and classification are performed to obtain a modified lithium manganese composite oxide whose particle surface is coated with the drug. The drying temperature is not particularly limited as long as the solvent can be removed, but in many cases it is 50 to 200 ° C, preferably 70 to 150 ° C. In the present invention, the drying after the contact treatment may be performed by a method of drying the entire reaction solution.

  The modified lithium transition metal composite oxide of the present invention thus obtained is suitably used as a positive electrode active material composition for a lithium secondary battery comprising a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte containing a lithium salt. be able to.

Although the modified lithium manganese composite oxide of the present invention can be used alone as a positive electrode active material, a lithium manganese composite oxide obtained by modifying the lithium manganese composite oxide represented by the general formula (1), The following general formula (3);
Li _a M _{1- b} AbO _c (3)
(Wherein M is at least one transition metal element selected from Co and Ni, A is at least one transition metal element selected from Mg, Al, Mn, Ti, Zr, Fe, Cu, Zn, Sn, In) A metal element, a is 0.9 ≦ a ≦ 1.1, b is 0 ≦ b ≦ 0.5, and c is 1.8 ≦ c ≦ 2.2.) It is preferable to use in combination. In this case, the modified lithium manganese composite oxide of the present invention acts as a positive electrode secondary active material, and has a synergistic action with the lithium composite oxide represented by the general formula (3), thereby overdischarge characteristics of the lithium secondary battery. In addition, battery storage characteristics and battery thermal stability can be improved. The lithium composite oxide represented by the general formula (3) is not particularly limited, but examples thereof include LiCoO ₂ , LiNiO ₂ , LiNi _0.8 Co _0.2 O ₂ , LiNi _0.8 Co _0.1 Mn _0.1 O _2. LiNi _0.4 Co _0.3 Mn _0.3 O _{2 and the} like, and these lithium composite oxides can be used alone or in combination of two or more. Among them, LiCoO ₂ is particularly preferred because it is widely used industrially and has a high synergistic effect with the modified lithium manganese composite oxide of the present invention.

Further, the physical properties of the lithium composite oxide represented by the general formula (3) are not particularly limited, but when the average particle size is 1 to 50 μm, preferably 3 to 20 μm, polarization and poor conductivity are suppressed. It is preferable in that it can be performed. Further, a BET specific surface area of 0.1 to 2.0 m ² / g, preferably 0.2 to 1.0 m ² / g is preferable in terms of improving battery thermal stability.

  When the modified lithium manganese composite oxide of the present invention is used in combination with the lithium composite oxide represented by the general formula (3), the blending ratio of the modified lithium manganese composite oxide of the present invention is the above general formula (3). It is 5-30 weight part with respect to 100 weight part of lithium complex oxide represented by this, Preferably it is 10-20 weight part. The reason for this is that if the amount exceeds 30 parts by weight, the discharge capacity of the battery decreases. On the other hand, if the amount exceeds 5 parts by weight, the effect of suppressing overdischarge cannot be obtained sufficiently. When the modified lithium manganese composite oxide of the present invention and the lithium composite oxide represented by the general formula (3) are combined, the reason why the blended amount of the modified lithium manganese composite oxide of the present invention is smaller is preferable. Compared to the case of the modified lithium manganese composite oxide alone, the charge / discharge termination potential is higher in the combined use, so in this range the modified lithium manganese composite oxide hardly contributes to the charge / discharge, and the blending amount is This is because a smaller capacity can produce a battery with a higher capacity.

  In the lithium secondary battery positive electrode active material composition according to the present invention, the modified lithium manganese composite oxide alone or the modified lithium manganese composite oxide and the lithium composite oxide represented by the general formula (2) are used in combination. By using a material having the preferred particle size characteristics as described above, it is easy to knead when preparing a positive electrode mixture by mixing with other raw materials, and the obtained positive electrode mixture is used as a positive electrode. Coatability when applied to the current collector becomes easy.

  The lithium secondary battery according to the present invention uses the above-described lithium secondary battery positive electrode active material composition, and includes a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte containing a lithium salt. The positive electrode is formed, for example, by applying and drying a positive electrode mixture on a positive electrode current collector, and the positive electrode mixture is added to the positive electrode active material composition, a conductive agent, a binder, and if necessary. It consists of fillers. In the lithium secondary battery according to the present invention, the modified lithium-lithium manganese composite oxide or modified lithium-lithium manganese composite oxide, which is a positive electrode active material composition, and other lithium transition metal composite oxide are uniformly formed on the positive electrode. It has been applied.

  The positive electrode current collector is not particularly limited as long as it is an electronic conductor that does not cause a chemical change in the constituted battery. For example, stainless steel, nickel, aluminum, titanium, calcined carbon, aluminum, and stainless steel Examples of the surface include carbon, nickel, titanium, and silver surface-treated. The surface of these materials may be oxidized and used, or the current collector surface may be provided with irregularities by surface treatment. Examples of the current collector include foils, films, sheets, nets, punched ones, lath bodies, porous bodies, foam bodies, fiber groups, nonwoven fabric molded bodies, and the like. The thickness of the current collector is not particularly limited, but is preferably 1 to 500 μm.

  The conductive agent is not particularly limited as long as it is an electron conductive material that does not cause a chemical change in the constructed battery. For example, graphite such as natural graphite and artificial graphite, carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, carbon black such as thermal black, conductive fibers such as carbon fiber and metal fiber, Examples include metal powders such as carbon fluoride, aluminum and nickel powder, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide, and conductive materials such as polyphenylene derivatives. Examples of graphite include scaly graphite, scaly graphite, and earthy graphite. These can be used alone or in combination of two or more. The blending ratio of the conductive agent is 1 to 50% by weight, preferably 2 to 30% by weight in the positive electrode mixture.

  Examples of the binder include starch, polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, regenerated cellulose, diacetylcellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer ( EPDM), sulfonated EPDM, styrene butadiene rubber, fluoro rubber, tetrafluoroethylene-hexafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, fluorinated Vinylidene-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene Oroethylene copolymer, polychlorotrifluoroethylene, vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetra Fluoroethylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymer, ethylene-acrylic acid copolymer or its (Na +) ionic crosslinked product, ethylene-methacrylic acid copolymer or its (Na + ) Ionic crosslinked body, ethylene-methyl acrylate copolymer or its (Na +) ionic crosslinked body, ethylene-methyl methacrylate copolymer or its (Na +) ionic crosslinked body, polysaccharide such as polyethylene oxide, thermoplastic resin Polymers having rubber elasticity, and these may be used individually or in combination. In addition, when using the compound containing a functional group which reacts with lithium like a polysaccharide, it is preferable to add the compound like an isocyanate group and to deactivate the functional group, for example. The blending ratio of the binder is 1 to 50% by weight, preferably 5 to 15% by weight in the positive electrode mixture.

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

  The negative electrode is formed by applying and drying a negative electrode material on the negative electrode current collector. The negative electrode current collector is not particularly limited as long as it is an electronic conductor that does not cause a chemical change in the constructed battery. For example, stainless steel, nickel, copper, titanium, aluminum, calcined carbon, copper or stainless steel Examples of the steel surface include carbon, nickel, titanium, silver surface-treated, and an aluminum-cadmium alloy. Further, the surface of these materials may be used after being oxidized, or the surface of the current collector may be used with surface roughness by surface treatment. Examples of the current collector include foils, films, sheets, nets, punched ones, lath bodies, porous bodies, foam bodies, fiber groups, nonwoven fabric molded bodies, and the like. The thickness of the current collector is not particularly limited, but is preferably 1 to 500 μm.

The negative electrode material is not particularly limited, and examples thereof include carbonaceous materials, metal composite oxides, lithium metals, lithium alloys, silicon-based alloys, tin-based alloys, metal oxides, conductive polymers, and chalcogen compounds. And Li—Co—Ni-based materials. Examples of the carbonaceous material include non-graphitizable carbon materials and graphite-based carbon materials. Examples of the metal composite oxide include Sn _p M ¹ _1-p M ² _{q Or} (wherein M ¹ represents one or more elements selected from Mn, Fe, Pb and Ge, and M ² represents Al. , B, P, Si, one or more elements selected from Group 1, Group 2, Group 3 of the periodic table and halogen elements, 0 <p ≦ 1, 1 ≦ q ≦ 3, 1 ≦ r ≦ 8.), LixFe ₂ O ₃ (0 ≦ x ≦ 1), LixWO ₂ (0 ≦ x ≦ 1) and the like. As the metal _{oxide, 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 and the} like. Examples of the conductive polymer include polyacetylene and poly-p-phenylene.

  As the separator, an insulating thin film having a large ion permeability and a predetermined mechanical strength is used. Sheets and non-woven fabrics made of olefin polymers such as polypropylene, glass fibers or polyethylene are used because of their organic solvent resistance and hydrophobicity. The pore diameter of the separator may be in a range generally useful for batteries, for example, 0.01 to 10 μm. The thickness of the separator may be in a range for a general battery, for example, 5 to 300 μm. When a solid electrolyte such as a polymer is used as the electrolyte described later, the solid electrolyte may also serve as a separator.

  The non-aqueous electrolyte containing a lithium salt is composed of a non-aqueous electrolyte and a lithium salt. As the non-aqueous electrolyte, a non-aqueous electrolyte, an organic solid electrolyte, or an inorganic solid electrolyte is used. Examples of the non-aqueous electrolyte include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydroxyfuran, and 2-methyl. Tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 3-methyl -2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, diethyl ether, 1,3- Ropansaruton, methyl propionate, and a solvent obtained by mixing one or more aprotic organic solvents such as ethyl propionate.

  Examples of the organic solid electrolyte include a polyethylene derivative, a polyethylene oxide derivative or a polymer containing the same, a polypropylene oxide derivative or a polymer containing the same, a phosphate ester polymer, polyphosphazene, polyaziridine, polyethylene sulfide, polyvinyl alcohol, polyvinylidene fluoride, Examples thereof include a polymer containing an ionic dissociation group such as polyhexafluoropropylene, and a mixture of a polymer containing an ionic dissociation group and the above non-aqueous electrolyte.

As the inorganic solid electrolyte, a nitride, halide, oxyacid salt, or the like of Li can be used. For example, 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, Li 3 PO 4 -Li 2 S-SiS 2, and the like phosphorus sulfide compound.

As the lithium salt, those dissolved in the non-aqueous 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, lithium chloroborane, lithium lower aliphatic carboxylate, lithium tetraphenylborate, Examples thereof include salts in which one kind or two or more kinds such as imides are mixed.

  Moreover, 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, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphoric acid 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, conductive polymer electrode active material monomer, triethylenephosphonamide, trialkylphosphine, morpholine, aryl compounds with carbonyl group, hexamethylphosphine Examples include hollic triamide and 4-alkylmorpholine, bicyclic tertiary amines, oils, phosphonium salts and tertiary sulfonium salts, phosphazenes, and carbonates. That. In order to make the electrolyte nonflammable, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride can be included in the electrolyte. In addition, carbon dioxide gas can be included in the electrolytic solution in order to make it suitable for high-temperature storage.

  The lithium secondary battery according to the present invention is a lithium secondary battery excellent in battery performance, particularly in cycle characteristics and coulomb efficiency. The shape of the battery may be any shape such as a button, a sheet, a cylinder, a corner, or a coin shape.

  The use of the lithium secondary battery according to the present invention is not particularly limited. And electronic devices such as memory cards and video movies, and consumer electronic devices such as automobiles, electric vehicles, and game machines.

  In the present invention, the particle surface of the lithium manganese composite oxide is coated with an acidic phosphate ester or an organic compound having a chelating ability. The effect of this coating treatment is not clear, but in the case of an acidic phosphate ester, it reacts with the OH group on the particle surface of the lithium manganese composite oxide, and this OH group is converted to an alkoxy group to form a “Mn—O—P” bond. On the other hand, in the case of an organic compound having chelating ability, it effectively forms a chelate with the manganese ion on the particle surface of the lithium manganese composite oxide by utilizing the coordination ability to metal, and effectively deactivates the hydroxyl group. It is considered that side reactions with the electrolyte can be suppressed by this, and as a result, suppression of gas generation and improvement of storage characteristics can be achieved, and the high charge capacity inherent in lithium manganese composite oxide itself (high Li supply capacity) As a lithium secondary battery positive electrode active material composition or a lithium secondary battery positive electrode secondary active material composition, in particular, a lithium secondary battery positive electrode secondary active material composition. Considered to be a useful lithium manganese composite oxide.

EXAMPLES Next, the present invention will be described more specifically with reference to examples. However, this is merely an example, and the present invention is not limited thereto.

<Preparation of lithium manganese composite oxide sample>
LiMnO ₂ sample Weigh Mn ₂ O ₃ (average particle size 7 μm) and Li ₂ CO ₃ (average particle size 5.5 μm) so that the molar ratio of Li atom to Mn atom (Li / Mn) is 1.00. The mixture was thoroughly mixed in a dry process and then fired at 800 ° C. for 10 hours in a nitrogen atmosphere. Next, the fired product was pulverized and classified to obtain LiMnO ₂ . Table 1 shows the main physical properties of the obtained product.

Examples 1 to 20 and Comparative Example 1
The drugs shown in Table 2 were dissolved in 150 ml of ethanol at a ratio of 0.5 g, 1 g or 10 g, respectively. Next, 100 g of LiMnO ₂ prepared above was added to this solution and stirred at 25 ° C. for 2 minutes. Next, after filtration, drying was performed at 120 ° C. under reduced pressure to obtain a modified lithium manganese composite oxide sample. Table 2 shows the physical properties of the obtained modified lithium manganese composite oxide. The pH and tap density were measured as follows. The modified lithium manganese composite oxide sample obtained in Example 9 was subjected to a Mn elution test described later. The results are also shown in Table 2.

In addition, a lithium manganese composite oxide sample obtained by adding 100 g of LiMnO ₂ prepared above to 150 ml of ethanol, stirring at 25 ° C. for 2 minutes, and drying was used as Comparative Example 1. The various physical properties are shown in Table 2.

(Measurement of pH)
5 g of a lithium manganese composite oxide sample was added to 100 g of ultrapure water, and the supernatant liquid after stirring at 25 ° C. for 5 minutes was measured by a pH meter.

(Tap density)
A 50 g sample was placed in a 50 ml graduated cylinder, this was set in a dual automatic tap device manufactured by Yuasa Ionics Co., Ltd., and the tap density was determined from the volume after tapping 500 times and the sample weight.

(Mn dissolution test)
A 1.0 g sample of lithium manganese composite oxide was weighed and vacuum-dried at 120 ° C. for 3 days, and then added to 50 ml of 1 mol of LiPF ₆ dissolved in 1 liter of 1: 1 kneaded solution of ethylene carbonate and methyl ethyl carbonate. Sealed and kept at 80 ° C. for 1 week. After the retention, the liquid was filtered with a 0.45 μm filter, 20 ml of ethanol was added to 1.0 g of the filtered liquid, and further adjusted to 100 ml with pure water, and the Mn concentration in this liquid was determined by ICP.

Note) Symbols in Table 2 indicate the following. MMA; methyl acid phosphate, EAP; ethyl acid phosphate, PAP; isopropyl acid phosphate, EPA; ethylphosphonic acid, PPA; phenylphosphonic acid, OPA; octylphosphonic acid, AcAc; acetylacetone

  From the results shown in Table 2, since the pH of the lithium manganese composite oxide particle surface treated with an acidic phosphate ester or an organic compound having chelating ability is reduced, gas generation during high-temperature storage is suppressed. it can. Moreover, since the tap density is improved depending on the amount of the chemical used for the treatment, the filling property is good and a battery with a high capacity can be manufactured.

<Preparation of lithium secondary battery>
(1) Production of lithium secondary battery;
For each of the composite oxide samples of Examples 2, 4, 7, 10, 13, 16, 20 and Comparative Example 1 prepared as described above, the sample was 85% by weight, the graphite powder was 10% by weight, and the polyvinylidene fluoride was 5% by weight. Were mixed to obtain a positive electrode agent, which was dispersed in N-methyl-2-pyrrolidinone to prepare a kneaded paste. The kneaded paste was applied to an aluminum foil, dried, pressed and punched into a disk with a diameter of 15 mm to obtain a positive electrode plate.

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

(2) initial discharge capacity, the initial charge capacity charge CCCV mode, the cut-off voltage 4.25 V, 2.5 mA / cm ² cut off current at a current density 1/20 1C current, charging CCCV mode, cut The initial discharge capacity and the initial charge capacity were measured at an off voltage of 3.4 V, a current density of ^2.5 mA / cm ² and a cut-off current of 7/200 of 1 C current. The results are shown in Table 3.

In this test, the larger the charge capacity and the smaller the discharge capacity, that is, the greater the difference between the charge and discharge capacity, the better the overdischarge characteristics as the positive electrode active material. In general, the positive electrode active material is, for example, LiCoO ₂ with a discharge capacity of about 160 mAH / g with respect to a charge capacity of 165 mAH / g, and the capacity difference of the charge / discharge capacity is small. Unlike the evaluation, the difference in charge / discharge capacity is large. As can be seen from Table 3, in the Examples, the Li supply capability necessary as the positive electrode secondary active material is hardly reduced by the coating treatment. It can also be seen that LiMnO ₂ is also excellent in usefulness as a positive electrode secondary active material for improving safety during overdischarge.

<Evaluation of battery thermal stability>
Soseki, Kita, Wada (November 21-23, 2001, 42nd Battery Symposium, Abstracts, 462-463), Ota, Oiwa, Ishigaki et al. (November 21-23, 2001) The 42nd Battery Symposium Abstracts, pages 470-471) and the composite oxidation prepared in Examples 7 and 20 and Comparative Example 1 based on the battery thermal stability evaluation method disclosed in Japanese Patent Application Laid-Open No. 2002-158008. After charging a lithium secondary battery using the product as a positive electrode active material with a CCCV mode, a cutoff voltage of 4.25 V, a current density of ^2.5 mA / cm ² and a cutoff current of 1/20 of the 1C current value, The lithium secondary battery was disassembled under an argon atmosphere, and a positive electrode plate containing a positive electrode active material from which lithium was deintercalated was taken out. Next, 5.0 mg of the positive electrode active material is scraped from each of the taken-out positive electrode plates, and the differential scanning calorific value together with 5.0 ml of a solution of 1 mol of LiPF _{6 in} 1 liter of a 1: 1 kneaded solution of ethylene carbonate and methyl ethyl carbonate. The sample was sealed in a pressure-resistant sealed cell (SUS cell) for measurement (DSC), and the change in differential calorific value was measured with a differential scanning calorimeter (model DSC6200, manufactured by Seiko Instruments Inc.) at a heating rate of 2 ° C./min. The result of the change in the differential calorific value is shown in FIG.

  As the amount of heat on the vertical axis in FIG. 1, a value obtained by dividing the weight of the measured positive electrode active material and electrolyte was used. It should be noted that the thermal stability, that is, the battery thermal safety, is superior when the temperature when the height of the exothermic peak is maximum in FIG. 1 is high and the gradient of the calorific value from the start of heat generation is gentle. It shows that.

From the results of FIG. 1, the LiMnO _{2 of} Comparative Example 1 has a temperature of 306 ° C. when the height of the exothermic peak is maximum, and in the modified lithium manganese composite oxides of Examples 7 and 20 of the present invention, Since the temperature when the height of the exothermic peak becomes maximum is 317 ° C. and 319 ° C., respectively, it can be seen that the battery has excellent thermal stability.

Examples 21-22 and Comparative Examples 2-3
(Preparation of lithium composite oxide)
40.0 g of Co ₃ O ₄ (average particle size 5 μm) and 8.38 g of Li ₂ CO ₃ (average particle size 5 μm) were weighed, thoroughly mixed by a dry process, and calcined at 1000 ° C. for 5 hours. The fired product was pulverized and classified to obtain LiCoO ₂ . Various physical properties of this product are shown in Table 4.

<Preparation of lithium secondary battery>
<Battery performance test>
(1) Production of lithium secondary battery;
A positive electrode active material having the composition shown in Table 5 was prepared using the modified lithium manganese composite oxide and LiCoO ₂ prepared above. Next, 91% by weight of the positive electrode active material, 6% by weight of graphite powder, and 3% by weight of polyvinylidene fluoride were mixed to prepare a positive electrode agent, which was dispersed in N-methyl-2-pyrrolidinone to prepare a kneaded paste. The kneaded paste was applied to an aluminum foil, dried, pressed and punched into a disk with a diameter of 15 mm to obtain a positive electrode plate. Using this positive electrode plate, a lithium secondary battery was manufactured using each member such as a separator, a negative electrode, a positive electrode, a current collector plate, a mounting bracket, an external terminal, and an electrolytic solution. Of these, artificial graphite was used for the negative electrode, copper was used for the current collector, and 1 mol of LiPF ₆ was dissolved in 1 liter of a 1: 1 kneaded solution of ethylene carbonate and methyl ethyl carbonate as the electrolyte.

(2) Overdischarge test The batteries of Example 21, Example 22, Comparative Example 2 and Comparative Example 3 were charged up to 4.2 V with a current equivalent to 1 C at 25 ° C., and a constant voltage of 4.2 V for 3 hours. After charging, the discharge capacity when discharged to 2.7 V at a current equivalent to 1 C (hereinafter referred to as “initial discharge capacity”) was measured. Next, the battery was allowed to stand for 2 days at a constant voltage of 0 V and overdischarged. After standing, recharged at a constant current / constant voltage for 3 hours at a current equivalent to 1C at a constant current of 3V, and then discharged at a constant current up to 2.7V at a current equivalent to 1C. ) Was measured.

  For this recovery capacity, the ratio of the recovery capacity to the initial discharge capacity measured in the previous discharge test (hereinafter referred to as “capacity recovery rate”) was determined and shown in Table 6. Further, the battery after the test was disassembled and the positive electrode was observed to observe whether copper of the negative electrode current collector was deposited on the positive electrode. The results are shown in Table 6.

(3) Gas generation test Further, after charging the lithium secondary battery prepared above to 4.2 V at a current equivalent to 1 C at 25 ° C., the battery is removed from the charging device and held in a constant temperature bath at 80 ° C. for 10 days. did. Next, the battery was disassembled, the generated gas was collected in water in a cylinder, and the amount of gas generated was measured. The results are shown in Table 6.

  From the results shown in Table 6, it can be seen that the lithium secondary battery using the modified lithium manganese composite oxide of the present invention as the positive electrode secondary active material has improved overdischarge characteristics and less gas generation.

It is a figure which shows the differential calorie | heat amount change of the positive electrode active material which extracted lithium from the modified lithium manganese complex oxide obtained in Example 7, Example 20, and Comparative Example 1, and was deintercalated.

Claims (9)

The following general formula (1) or the following general formula (2);
Li _x MnO ₂ (1)
Li _y Mn ₂ O ₄ (2)
(Wherein x represents 0.9 ≦ x ≦ 1.1, and y represents 0 <y <2). The organic compound in which the particle surface of the lithium manganese composite oxide has acidic phosphate ester or chelate ability A modified lithium manganese composite oxide, which is coated with at least one agent selected from the group consisting of:   2. The modified lithium manganese composite oxide according to claim 1, wherein the coating amount of the drug is 0.1 to 15.0% by weight of the weight of the modified lithium manganese composite oxide.   The modified lithium manganese composite oxide according to claim 1, having an average particle size of 1.0 to 30.0 µm. The modified lithium manganese composite oxide according to claim 1, wherein the BET specific surface area is 0.1 to 10.0 m ² / g. The lithium manganese composite oxide has the following general formula (1):
Li _x MnO ₂ (1)
The modified lithium manganese composite oxide according to claim 1, wherein the lithium manganese composite oxide is represented by the formula: The following general formula (1) or the following general formula (2);
Li _x MnO ₂ (1)
Li _y Mn ₂ O ₄ (2)
(Wherein x represents 0.9 ≦ x ≦ 1.1 and y represents 0 <y <2) and is selected from a lithium manganese composite oxide and an acidic phosphate ester or an organic compound having a chelating ability. A method for producing a modified lithium manganese composite oxide, comprising contacting at least one drug.   A lithium secondary battery positive electrode active material composition comprising the modified lithium manganese composite oxide according to any one of claims 1 to 5. The modified lithium manganese composite oxide according to claim 5 and the following general formula (3):
Li _a M _{1- b} AbO _c (3)
(Wherein M is at least one transition metal element selected from Co and Ni, A is at least one transition metal element selected from Mg, Al, Mn, Ti, Zr, Fe, Cu, Zn, Sn, In) A metal element, a is 0.9 ≦ a ≦ 1.1, b is 0 ≦ b ≦ 0.5, and c is 1.8 ≦ c ≦ 2.2.) A positive electrode active material composition for a lithium secondary battery, comprising:    A lithium secondary battery comprising the lithium secondary battery positive electrode active material composition according to any one of claims 7 and 8.

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