WO2001004975A1

WO2001004975A1 - Positive plate active material, method for producing the same, and secondary cell

Info

Publication number: WO2001004975A1
Application number: PCT/JP2000/004544
Authority: WO
Inventors: Takao Noda; Akihiko Shirakawa; Joseph Gaze; Yoshiaki Yamauchi; Fumiyoshi Ono
Original assignee: Showa Denko K.K.
Priority date: 1999-07-07
Filing date: 2000-07-07
Publication date: 2001-01-18
Also published as: CN1360739A; JP5464717B2; AU5850200A; KR20020012295A; JP2012074390A; CN1179437C; KR100653170B1; JP2011049180A

Abstract

A positive plate active material for lithium ion secondary cells mainly containing an Li-Mn composite oxide particles having a spinel structure wherein the average of the porosity (A/B) x 100 (%) (1) (where A is the total cross sectional area of the pores included in a cross section of one secondary particle, and B is the cross sectional area of one secondary particle) of the particles is 15% or less, the tap density is 1.9 g/ml or more, the crystallite size is 400-900 A, and the lattice constant is 8.240 A or less. A method for producing the positive plate active material and a lithium ion secondary cell comprising the positive plate active material are also disclosed. The particles of the positive plate active material are dense and spherical. The packability of the particles in an electrode is excellent. The initial capacity and capacity maintenance factor of the secondary cell are high even in a high-temperature environment.

Description

Description Positive electrode active material, manufacturing method and secondary battery technical field

The present invention includes a positive active material for a ^primary battery, a secondary battery using a manufacturing method and a cathode active material. Background art

As a positive electrode active material for lithium ion secondary batteries, lithium manganese composite oxides (hereinafter referred to as i-Mn-based composite oxides), which are excellent in safety and have abundant resources, are attracting attention. However, the Li_Mn-based composite oxide has a lower capacity per active material than the lithium-cobalt composite oxide (abbreviated as Li-Co-based composite oxide), and has many voids in the secondary particles. Since the secondary particles are light, the amount of active material that can be charged into a battery whose size is limited due to its light weight and large oil absorption is reduced. As a result, there is a problem that the electric capacity per unit battery is small.

As a remedy, in recent years, after the mixture 500 k gZ cm ² or more press molding at a pressure of between manganese compound and a lithium compound, more performing heat treatment was disintegrated, the container with tap density (certain conditions There is a proposal to obtain a Li-Mn composite oxide having an apparent density of 1.7 g / ml or more (viz., Powder obtained by vibration) (US Pat. No. 5,807,646, JP-A-9-86933). . However, the specific tap density disclosed was at most 1.9 gZm 1, not a satisfactory level.

In addition, the above-mentioned publication discloses the average particle diameter of the secondary particles in which the primary particles of the Li-Mn-based composite oxide are aggregated, but the secondary particles have an interaction between the primary particles. Even if it is used to improve the filling property, the agglomeration disappears at the stage of coating (electrode base) during the preparation process of the electrode material, and it is not an essential improvement measure. In addition, as a method for producing a Li-Mn-based composite oxide having a spinel structure, there is a method in which a mixture of a manganese compound and a lithium compound is calcined at a high temperature (for example, at a temperature of 250 to 850 ° C). (Japanese Unexamined Patent Publication (Kokai) No. 9-186933) and Li_Mn—B in which a manganese compound and a lithium compound are further mixed with an oxide of a boron element that can be substituted for manganese, and baked at a high temperature to partially substitute Mn with B A method for producing a positive electrode active material of a system oxide (Japanese Patent Application Laid-Open No. 237970/1991) has been disclosed.

However, when these raw materials are fired at high temperatures in the atmosphere or in an oxygen gas flow, the secondary particles after crushing have a large average porosity (15% or more) and low tap density (1. Therefore, it is not possible to increase the mass by increasing the mass of the positive electrode active material charged to the electrode to achieve high capacity.

Japanese Patent Application Laid-Open No. 147152/1991 discloses the use of a manganese-based oxide obtained by mixing titanium oxide with a spinel-type lithium manganese oxide and sintering it as a positive electrode active material. (If the temperature is not higher than 1000 ° C, it reacts with lithium and manganese to form no melt, and if only 10% by mass of titanium oxide is not added, the tap density is only 1.60 g / m1. There was a problem that it was not possible.

An object of the present invention is to provide a positive electrode active material for a lithium ion secondary battery having excellent filling properties, a high initial capacity, and a small decrease in capacity upon repeated charge / discharge (high capacity retention rate), a method for producing the same, and a method for producing the same An object of the present invention is to provide a lithium ion secondary battery using a positive electrode active material.

As a result of intensive studies, the present inventors have found that a Li-Mn composite having a spinel structure is obtained. After pulverizing the calcined product of the composite oxide, a sintering accelerator was added to the pulverized particles, and the particles were densified by granulation and firing, thereby solving the above problem.

That is, the present invention provides the following positive electrode active material for a lithium ion secondary battery, a method for producing the same, an electrode paste containing the positive electrode active material, a positive electrode for a lithium ion secondary battery, and a lithium ion secondary battery .

[1] A positive electrode active material for lithium ion secondary batteries mainly composed of Li i Mn-based composite oxide particles having a spinel structure has the following formula:

Porosity (%) = (A / B) X 100 (1) (A is the total cross-sectional area of the pores included in the cross section of one secondary particle, and B is the cross-sectional area of one secondary particle. The positive electrode active material for a lithium ion secondary battery, wherein the average value of the porosity of the particles is 15% or less.

[2] The positive electrode active material for a lithium ion secondary battery according to [1], wherein the value of the average porosity is 10% or less, and the average particle size of the primary particles is 0.2 to 3 zm.

[3] The positive electrode active material for a lithium ion secondary battery according to [1], wherein the positive electrode active material has a tap density of 1.9 g / m 1 or more.

[4] The positive electrode active material for a lithium ion secondary battery according to [3], wherein the positive electrode active material has a tap density of 2.2 gZm 1 or more.

[5] The positive electrode active material for a lithium ion secondary battery according to the above [1], wherein the crystallite size of the positive electrode active material is 400 to 960 Å.

[6] The positive electrode active material for a lithium ion secondary battery according to the above [1], wherein the positive electrode active material has a lattice constant of 8.240 angstroms or less.

[7] The cathode active material is mainly composed of a Li-Mn-based composite oxide having a spinel structure, and the oxide can be an oxide or an oxide that melts at a temperature of 550 ° C to 900 ° C or Compound containing element, or lithium or manganese The lithium ion secondary battery according to the above [1], which is an active material which is formed of an oxide or a compound containing an element or an element which can be converted into an oxide or an oxide which can be dissolved by reacting with and is granulated and sintered. Positive electrode active material for secondary batteries.

[8] An element or a compound containing an element that can become an oxide or an oxide that melts at a temperature of 550 ° C to 900 ° C, or an oxide or an oxide that solid-dissolves with or reacts with lithium or manganese to melt combinations compound containing it obtained element or elements, B i, B, W, Mo, a compound containing at least one element or element selected from the group consisting of P b, or B ₂ 〇 ₃ and L i F compound or a positive electrode active material for lithium ion secondary battery according to Mn F ₂ and L i F wherein a compound which is a combination of [7] was.

[9] In the method for producing a positive electrode active material for a lithium ion secondary battery mainly composed of a Li-Mn-based composite oxide having a spinel structure, a pulverized product of the Li-Mn-based composite oxide having a spinel structure is An element or a compound containing an element that can become an oxide or oxide that melts at a temperature of 550 ° C to 900 ° C, or an oxide or oxide that dissolves or reacts with lithium or manganese to melt. A method for producing a positive electrode active material for a lithium ion secondary battery, comprising a step of adding, mixing and granulating an element or a compound containing the element.

[10] The method for producing a positive electrode active material for a lithium ion secondary battery according to the above [9], further comprising a step of sintering the granulated material in addition to the granulating step.

[11] In addition to the granulation step, the granulated material is heated from the sintering shrinkage initiation temperature to a temperature at least 100 ° C or higher at a rate of at least 100 ° C Zmin and raised to that temperature for 1 minute to 10 minutes. The method for producing a positive electrode active material for a lithium ion secondary battery according to the above [9], comprising a step of lowering the temperature to a sintering start temperature at a rate of at least 100 ° C./min after the holding and sintering.

[12] The method for producing a positive electrode active material for a lithium secondary battery according to the above [11], wherein the positive electrode active material is sintered using a single tally kiln. [13] In the sintering step, at least one element selected from the group consisting of Bi, B, W, Mo, and Pb on the surface of the Li-Mn-based composite oxide particles, or a compound containing an element, or positive electrode active material for a lithium ion secondary battery according to [10] that the B ₂ 0 ₃ and compound a combination of L i F or compounds that combine Mn F ₂ and L i F is performed by melting and sintering Manufacturing method.

[14] The method for producing a positive electrode active material for a lithium ion secondary battery according to the above [9], wherein the pulverized Li-Mn-based composite oxide having a spinel structure has an average particle diameter of 5 m or less.

[15] The method for producing a positive electrode active material for a lithium ion secondary battery according to the above [9], wherein the average particle diameter of the ground material of the Li-Mn-based composite oxide having a spinel structure is 3 / zm or less.

[16] The positive electrode active material for a lithium ion secondary battery according to [9], wherein the granulation step is performed by a spray granulation method, a stirring granulation method, a compression granulation method, or a fluidized granulation method. Production method.

[17] In the granulation step, as a granulation auxiliary, an acrylic resin, a copolymer of isobutylene and maleic anhydride, polyvinyl alcohol, polyethylene glycol, polyvinyl pyrrolidene, hydroxypropylcellulose, methylcellulose, corn starch The method for producing a positive electrode active material for a lithium ion secondary battery according to the above [9], wherein at least one organic compound selected from the group consisting of gelatin, and lignin is used.

[18] The method for producing a positive electrode active material for a lithium ion secondary battery according to the above [17], further comprising a degreasing step at a temperature of 300 ° C. to 550 ° C. in the air or in a gas flow atmosphere containing oxygen. .

[19] A positive electrode active material for a lithium ion secondary battery obtained by the method according to any one of the above [9] to [18].

[20] The lithium ion secondary according to any one of the above [1] to [8] An electrode paste containing a positive electrode active material for a battery.

[21] A positive electrode for a lithium ion secondary battery, comprising the positive electrode active material for a lithium ion secondary battery according to any one of [1] to [8] or [19].

[22] A lithium ion secondary battery provided with the positive electrode for a lithium ion secondary battery according to the above [21].

[23] The lithium ion secondary battery according to the above [22], wherein the lithium ion secondary battery is a coin battery, a wound battery, a cylindrical battery, a square battery, or a stacked battery. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a scanning electron micrograph (X15,000 magnification) of an example (Example 14) of a positive electrode active material granulated, fired, and sized according to the present invention.

FIG. 2 is a particle size distribution of an example (Example 14) of the positive electrode active material granulated, fired, and sized according to the present invention. Detailed description of the invention

Hereinafter, the present invention will be described specifically.

The present invention relates to a Li-Mn-based composite oxide positive electrode active material having a spinel structure, in which the porosity of secondary particles is significantly reduced to 15% or less as compared with conventional products. The present invention also relates to a Li-Mn-based composite oxide having a spinel structure in which the average porosity of the secondary particles is 10% or less and the cycle characteristics thereof are particularly excellent as compared with conventional products.

That is, the positive electrode active material of the lithium-manganese (L i -Mn) -based composite oxide having a spinel structure according to the present invention has a chemical formula of i Mn ₂ 〇 ₄ , L i _{1 + X} M n ₂ — _x 0 ₄ x is in the range of 0 <x <0.2) or Mn is a group consisting of chromium, cobalt, aluminum, nickel, iron, and magnesium. L i _{1 + x} Mn ₂ — _x _ _y M _y 0 ₄ (where x is in the range of 0 <x <0.2) substituted with at least one selected element (abbreviated as M in the chemical formula) And y is 0 <y <0.4.) This is a generic term for compounds represented by the formula:

In the present invention, the positive electrode active material for a lithium ion secondary battery is mainly composed of a Li-Mn-based composite oxide having the spinel structure, and the porosity of one secondary particle is as follows. Equation (1)

Porosity (%) = (A / B) X 100 (1) (A is the total cross-sectional area of the pores included in the cross section of one secondary particle, and B is the cross-sectional area of one secondary particle. ) Is used and the average porosity is 15% or less.

The Li-Mn-based composite oxide preferably has an average porosity of the positive electrode active material of 10% or less and an average primary particle diameter of 0.2 to 3 m. Is done.

That is, the average porosity of the secondary particles must be 15% or less so that the tap density of the positive electrode active material exceeds 1.9 g nomL. The average porosity of the secondary particles is preferably 13% or less, more preferably 10% or less.

In general, in a composite oxide production method, if the sintering temperature is increased and the sintering time is lengthened to reduce the average porosity of the secondary particles by sintering shrinkage, the primary particles are sintered. Grain growth accompanies shrinkage and the size increases, and when this material is used as a battery positive electrode active material, the capacity retention rate decreases. As a result, the battery characteristics after battery assembly are deteriorated.

The present inventors have conducted intensive studies on a method of suppressing sintering by suppressing grain growth, and as a result, the temperature has been increased to at least 1001 higher than the sintering shrinkage onset temperature measured by a thermo-mechanical analysis. After raising the temperature at a rate of at least 100 ° C Zmin, holding for 1 to 10 minutes, reduce the temperature to the sintering shrinkage starting temperature. It has been found that by lowering the temperature at a rate of at least 100 ° C.Zin, grain growth can be suppressed and sintering shrinkage can be achieved.

Here, the sintering shrinkage onset temperature means the shrinkage onset temperature determined by a thermomechanical tester. The holding temperature needs to be at least 100 ° C. higher than the sintering shrinkage starting temperature. If the holding temperature is set to be lower than 100 ° C below the sintering start temperature, the sintering shrinkage rate is slow, so that a long sintering time is required, and as a result, the grain grows and the primary particle diameter becomes 0.5 / It will be larger than m.

In the sintering step, at a temperature higher than the sintering shrinkage starting temperature by at least 100 ° C. or more, the primary particle diameter is 0.2 m or more and 0.5 m or less, and excellent. The retention time for obtaining the battery characteristics is at least 1 minute and within 10 minutes. If the holding time is less than 1 minute, the heat transfer time is too short and the primary particle size is as small as less than 0.2 m, crystallization is insufficient, and the initial capacity is small. If the holding time exceeds 10 minutes, the grain growth proceeds even after sintering shrinkage, so that the primary particles become large and the capacity retention rate decreases.

In the present invention, the retention time is preferably from 2 minutes to 8 minutes, more preferably from 2 minutes to 5 minutes.

The reason why the heating rate and the cooling rate are limited to at least 100 ° CZ in the temperature range from the sintering start temperature to the holding temperature is to minimize the holding time in the temperature range where grain growth proceeds. This is because only sintering shrinkage proceeds to suppress grain growth.

Further, in order for the tap density of the positive electrode active material to exceed 2.2 g / m1, the average porosity of the secondary particles must be 10% or less, preferably 7% or less, and more preferably 7% or less. It is preferably at most 5%.

The crystallite size of the positive electrode active material in the present invention is preferably from 400 to 960 angstroms. When the crystallite size is less than 400 angstroms In this case, the initial capacity of the battery is low due to insufficient crystallinity, and the capacity retention rate is low. On the other hand, when the crystallite size exceeds 960 angstroms, the capacity retention rate drops sharply. More specifically, the preferred crystallite size is from 500 to 900 angstroms, more preferably from 700 to 900 angstroms.

Further, the positive electrode active material of the Li-Mn-based composite oxide having a spinel structure according to the present invention preferably has a lattice constant of 8.240 angstroms or less. If the lattice constant exceeds 8.240 angstroms, the capacity retention of the battery will be significantly reduced. Therefore, a preferable range of the lattice constant is 8.235 angstroms or less, and more preferably 8.233 angstroms or less.

The cathode active material of the present invention, which is mainly composed of a Li-Mn-based composite oxide having a spinel structure, is obtained by pulverizing a calcined product of the Li-Mn-based composite oxide having a spinel structure, (This is a secondary particle in which primary particles are aggregated, and preferably has an average particle diameter of 0 or less.) A sintering accelerator (granulation accelerator) is added to the mixture, and the mixture is granulated and fired. Dense granulated particles are used. Here, the dense granulated particles mean that there are no or few voids between the primary particles of the oxide. The positive electrode active material of the present invention is the above-described dense granulated particles, and is formed by using a sintering promoting agent described later.

Hereinafter, the method for producing the positive electrode active material of the present invention will be described.

The method for producing a Li-Mn-based composite oxide having a spinel structure is based on a method in which a mixture of a manganese compound and a lithium compound, or a mixture containing a compound containing a different element that can be substituted for manganese, is added to the atmosphere or oxygen. In the gas flow, firing may be performed at a temperature of 300 to 850 ° C. for at least one hour.

There is no particular limitation on the crystallinity of the Li-Mn-based composite oxide having a spinel structure, and there may be residual unreacted lithium compound and manganese oxide. I don't know. When using a Li-Mn-based composite oxide having a spinel structure with high crystallinity, there is no particular limitation on the lattice constant.However, if it is used for a positive electrode active material whose lattice constant is 8.240 on dastroms or less. In addition, a decrease in the capacity retention rate can be suppressed.

The raw material of the Li-Mn-based composite oxide having a spinel structure is not particularly limited, but is preferably a known manganese compound, for example, manganese dioxide, manganese trioxide, manganese tetraoxide, hydrated manganese oxide. Substances, manganese carbonate, manganese nitrate and the like can be used, and as the lithium compound, lithium hydroxide, lithium carbonate and lithium nitrate can be used.

Desirably, the manganese compound is manganese carbonate, which easily reacts at low temperature with a lithium compound having excellent battery characteristics when adapted to a positive electrode active material.

Manganese substitutional _{_{L i 1 + x M n 2}} - x _ y M y 〇 ₄ represented by L i - M n - M for the preparation of (different element) composite oxides, the lithium compound and the manganese compound At least one element selected from the group consisting of chromium, cobalt, aluminum, nickel, iron, and magnesium is used together with the raw material. The compound containing the different element M may be any compound capable of forming the oxide by a heating reaction, and may be added together with a lithium compound or a manganese compound during the heating reaction.

The method for crushing and crushing the secondary particles of the Li-Mn-based composite oxide having the spinel structure is not particularly limited, and a known crusher or crusher can be used. For example, a medium stirring type mill, a pole mill, a paint shaker, a jet mill, a roller mill and the like can be mentioned. The crushing and crushing method may be a dry method or a wet method. There is no particular limitation on the solvent that can be used in the wet process. For example, water, alcohol, and the like are used.

From the viewpoint of promoting sintering shrinkage, it has a spinel structure after The particle size of the Li-Mn-based composite oxide is important.

The particle size is preferably such that the average particle size measured by a laser type particle size distribution analyzer is 5 m or less. More preferably, the average particle diameter is 2 m or less without containing 5 or more coarse particles. More preferably, it does not contain coarse particles exceeding 3 m and has an average particle diameter of 1.5 m or less, more preferably 0.5 ^ m or less, still more preferably 0.3 / xm or less, and particularly preferably 0 / m or less. Less than 2 m.

There is no particular limitation on the method of mixing the crushed and pulverized Li-Mn-based composite oxide particles with the sintering aid, and examples thereof include the above-described medium stirring type pulverizer, pole mill, paint shearer, and mixing mixer. Can be used. The mixing method may be either a dry method or a wet method. When disintegrating and pulverizing the Li-Mn-based composite oxide, a sintering accelerator may be added and mixing may be performed simultaneously.

The sintering accelerator may be any compound capable of sintering the crushed and pulverized particles of the Li-Mn-based composite oxide particles for granulation, and more preferably a compound that melts at a temperature of 900 or less. For example, oxides or oxides that can be melted at a temperature of 550 ° C to 900 ° C, or oxides or oxides that dissolve or react with lithium or manganese to melt. Any compound can be used.

Examples of the sintering promoting aid include compounds containing elements such as Bi, B, W, Mo, and Pb, and these compounds may be used in any combination. Furthermore, compounds that combine B ₂ 0 ₃ and L i compound combines F or MnF ₂ and L i F is also used. Among them, compounds containing the elements Bi, B, and W are preferable because of their large sintering shrinkage effect.

Examples of the Bi compound include bismuth trioxide, bismuth nitrate, bismuth benzoate, bismuth oxyacetate, bismuth oxycarbonate, bismuth citrate, and bismuth hydroxide. Further, as the B compound, boron trioxide, Boron carbide, boron nitride, boric acid and the like. w Compounds include tungsten dioxide and tungsten trioxide.

The addition amount of the sintering accelerator is preferably in the range of 0.001 to 0.05 mol per mol of Li-Mn-based composite oxide in terms of the added metal element. . If the added amount in terms of the added metal element is less than 0.001 mol, no sintering shrinkage effect can be obtained, and if it exceeds 0.05 mol, the initial capacity of the active material becomes small. The preferred addition amount is from 0.005 to 0.03 mol.

The sintering accelerator may be used in a powder state or in a liquid state dissolved in a solvent. When added in the form of a powder, the average particle size of the sintering accelerator is preferably 50 m or less, more preferably 10 or less, and even more preferably 3 m or less. The sintering promoting aid is preferably added before granulation and sintering, but after granulation, the granulated material may be impregnated and sintered at a temperature at which the sintering promoting aid can be melted. The sintering promoting aid often remains in the positive electrode material used for the battery after firing. For example, the sintering promoting aid used in the production method of the present invention remains in the positive electrode active material. Is detected by analysis.

Next, a granulation method will be described.

Examples of the granulation method include a spray granulation method, a fluid granulation method, a compression granulation method, and a stirring granulation method using the sintering promoting aid. May be used in combination.

In the present invention, it is sufficient that dense secondary particles (including granulated particles) can be formed, and there is no particular limitation on the method of forming granules. Agitation granulation and compression granulation are particularly preferable because the density of secondary particles is high, and spray granulation is because the granulated particles have a true spherical shape. Examples of agitation granulators include Palec Co., Ltd.'s Vital Cardara Yule One-Yu-Ichi and Fuji Padal Co., Ltd.'s Spartan Riuser, and examples of compression granulators are Kurimoto Roller-Compactor-MRCP-200 type manufactured by Iron Works Co., Ltd. Examples of spray granulators include Ashizanilot Myza-ichi Co., Ltd. Mobile minor type spray dryer. There is no particular limitation on the size of the secondary particles to be granulated. If the average particle size of the granulated secondary particles is too large, it may be adjusted to a desired particle size immediately after granulation or after sintering by lightly crushing, pulverizing and classifying. Generally, secondary particles having a mean particle size of 10 to 20 m are preferred.

In order to increase the granulation efficiency, an organic granulation aid may be added.

Examples of such granulation aids include acrylic resins, copolymers of isobutylene and maleic anhydride, polyvinyl alcohol, polyethylene glycol, polyvinylpyrrolidene, hydroxypropylcellulose, methylcellulose, corn starch, gelatin, lignin, etc. Is mentioned.

As for the method of adding the granulation aid, it is more efficient to add and granulate by dissolving in water or an organic solvent such as alcohol and spraying than adding in a powder state. The addition amount of the granulation assistant is preferably 5 parts by mass or less, more preferably 2 parts by mass, based on 100 parts by mass of the Li-Mn-based composite oxide having a spinel structure and 100 parts by mass of the sintering accelerator. Not more than parts by mass.

Next, a method of firing the granulated secondary particles will be described.

The method of degreasing the granulated particles is performed by keeping the granulated particles in the air or in a gas flow containing oxygen at a temperature in the range of 300 to 550 ° C for 10 minutes or more. The defatted granules preferably have a carbon residue of 0.1% or less.

The calcination of the degreased granulated particles is performed in the temperature range of 550 ° C to 900 ° C in air or in a gas flow containing oxygen in order to suppress grain growth and promote sintering shrinkage. For more than 1 minute, the sintering accelerator can be held in a molten state on the surface of the Li-Mn-based composite oxide particles to cause sintering shrinkage and densification of the secondary particles. In the present invention, the sintering of the degreased granulated particles was measured by a thermomechanical tester in the air or in a gas flow containing oxygen in order to suppress grain growth and promote sintering shrinkage. Up to at least 100 ° C above the sintering shrinkage onset temperature After raising the temperature at a rate of at least 100 ° CZmin and holding it for 1 to 10 minutes, the temperature is reduced to the sintering shrinkage starting temperature at a rate of at least 100 ° CZmin, and the sintering is reduced to densify the secondary particles. Measure. The heating rate and the cooling rate between the room temperature and the sintering shrinkage initiation temperature may be 10 ° CZmin or less as in the conventional case. In addition, the sintering of the particles of the granulated material without using the above-described organic-based granulation aid is also performed by shrinking the sintering in the air or in a gas flow atmosphere containing oxygen to reduce the densification of the secondary particles. Can be measured.

The positive electrode active material of the present invention and the positive electrode active material obtained from the production method of the present invention are processed into a positive electrode for a lithium ion secondary battery according to the same method as the conventional Li-Mn-based composite oxide, and To be evaluated.

Hereinafter, an example in which the positive electrode active material of the present invention is used as a positive electrode material of a nonaqueous secondary battery will be described.

First, for the positive electrode material, a solution (for example, N-methylpyrrolidone, etc.) in which the positive electrode active material and a conductive agent such as a pump rack or graphite, and a binder (binding material) such as polyvinylidene fluoride are dissolved is prescribed. The mixture is kneaded at a certain ratio, applied as an electrode paste to a current collector, and then dried and pressed by a roll press or the like. As the current collector, a known metal current collector such as aluminum, stainless steel, or titanium is used.

As the electrolyte salt in the electrolytic solution used in the nonaqueous secondary battery of the present invention, a known lithium salt containing fluorine can be used. For example, L i PF ₆ , L i BF ₄ , L i N (CF ₃ S〇 ₂ ) ₂ , L i As F ₆ , L i CF ₃ S 0 ₃ , L i C ₄ F ₉ S〇 ₃ etc. can be used. . As the electrolyte for the non-aqueous secondary battery, at least one electrolyte of the known lithium salt containing fluorine is used by dissolving it in a non-aqueous electrolyte. As the non-aqueous solvent of the non-aqueous electrolyte, an aprotic solvent that is chemically and electrochemically stable can be used.

For example, dimethyl carbonate, propylene carbonate, ethylene carbonate, methyl carbonate And methyl propyl carbonate, methyl isopropyl carbonate, methyl butyl carbonate, methyl butyl carbonate, ethyl propyl carbonate, diisopropyl carbonate, dibutyl carbonate, 1,2-butylene carbonate, ethyl isopropyl carbonate, and ethyl butyl carbonate. Oligoethers such as triethylene glycol methyl ether and tetraethylene glycol dimethyl ether; aliphatic esters such as methyl propionate and methyl formate; aromatic nitriles such as benzonitrile and tolitolitol; dimethylformamide; Examples thereof include amides, sulfoxides such as dimethyl sulfoxide, lactones such as carboxylactone, sulfur compounds such as sulfolane, N-vinylpyrrolidone, N-methylpyrrolidone, and phosphate esters. Among them, carbonates, aliphatic esters and ethers are preferred.

The negative electrode used in the non-aqueous secondary battery of the present invention is not particularly limited as long as it is a material capable of inserting and extracting lithium ions reversibly. For example, lithium metal, lithium alloy, carbon material (including graphite) And metal chalcogens can be used.

Next, a method for evaluating the electrode characteristics will be described.

Mix the pot active material, Vulcan XC-72 made of Capot as a conductive material, and a tetrafluoroethylene resin as a binder in a mass ratio of 50:34:16 in a mass ratio, and the mixture is mixed with toluene. Swell for 12 hours. The swollen mixture is applied onto a current collector made of aluminum exci- band metal, pressed at ² tZcm2, and dried to form a positive electrode. On the other hand, a lithium foil is used as the negative electrode. As an electrolytic solution, used after dissolving L i PF ₆ at a concentration of 1 mole Bruno liter liquid mixture of dimethyl carbonate propylene carbonate at a ratio of 1: 2 volume ratio. A separator made of polypropylene is used as the separator, and silica fiber filter paper (for example, QR-100 manufactured by Advantech Toyo Co., Ltd.) is used as a reinforcing material for the purpose of preventing micro short circuit caused by dendrite formation of the negative electrode. Also used together. Using these positive electrode, negative electrode, electrolyte, separator and reinforcing material,

A 201-type coin battery is manufactured, and a charge / discharge cycle test is performed 500 times in a thermostat set at 60 ° C. The measurement conditions are: constant current constant voltage charge-constant current discharge, charge and discharge rate 1 C (charge pause 2.5 hours after the start of charge), and scan voltage 3.1 V to 4.3 V. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described with reference to Examples and Comparative Examples, but the present invention is not limited by the following description.

The properties of the positive electrode active materials shown in the following examples and Tables 1 to 3 were measured by the following methods.

1) Average particle size and specific surface area

Using a CRANAS GRANULOMETER (HR850) as a complete laser particle size analyzer, surfactant (Kao Demol P) was used to disperse the powder by ultrasonic wave in a 0.2% aqueous solution to measure the particle size distribution. I asked.

2) Tap density

Using a tap pinda machine (KRS-409) manufactured by Kuramochi Scientific Instruments Co., Ltd., measurement was performed after tapping 200 times at an amplitude of 8 mm.

3) Porosity

The positive electrode active material and the thermosetting resin are mixed and cured to embed the positive electrode active material in the resin, cut with a microtome, mirror-polished, and photograph the polished surface with a scanning electron microscope (SEM). Taken. The cross-sectional area B of one secondary particle in the obtained SEM photograph and the total cross-sectional area A of all the pores included in the cross-section of the secondary particle were measured with an image analyzer. The porosity C (%) of the particles was calculated, and the average value of the porosity of 50 randomly selected secondary particles was defined as the average porosity.

C (%) = (A / B) X 1 0 0 4) Crystallite size

It was calculated from the X-ray diffraction peak of the (1 1 1) plane measured under the following conditions using Scherrer's equation.

That is, assuming that the outer shape of the crystallite is cubic and does not have a size distribution, the value obtained by calculating the spread of the diffraction line according to the crystallite size from the half-value width was used. In addition, a single crystal silicon was pulverized with a tungsten carbide sample mill and then sieved to 44 m or less.

[Measurement device and method]

Rig-type goniometer manufactured by Rigaku Denki Co., Ltd. Continuous measurement was performed as the measurement mode, and the size of crystallites was analyzed using the Rigaku Denki Co., Ltd. RI T2000 series application software as the analysis software.

The measurement conditions were as follows: X-ray (CuKo! Line), output 50 kV, 180 mA, slit width (3 locations) 1 to 2 , 1Z2 °, 0.15mm, 2 方法 method for scan method, scan speed / min, measurement range (20) 17-20 °, step 0.004 °. The accuracy of the crystallite size obtained by this method is ± 30 angstroms.

5) Lattice constant

It was determined by the method of J. B. Nelson and DP Riley (Proc. Phys. So, 51, 160 (1945)).

6) Specific surface area

It was measured by the BET method.

7) Shape of granulated particles

Photographs of the granulated positive electrode active material with SEM, image analysis, and analysis of secondary particle circularity (circularity = 4 π [area 面積 (perimeter) ² ]) and needle ratio (needle shape) Ratio == needle absolute maximum length Ζ diagonal width). For each sample, 200 secondary particles were measured, and the average was calculated. Example 1

Manganese carbonate (C 2-10, Chuo Denki Kogyo Co., Ltd.) and lithium carbonate (Honjo Chemical Co., Ltd.) having a specific surface area of 22 m ² Zg so that the composition ratio of Li / Mn is 0.51 3N) mixed in a ball mill, heated from room temperature to 650 ° C at a heating rate of 200 ° C / hr in the air atmosphere, and kept at that temperature for 4 hours to produce a Li-Mn composite oxidation. Was synthesized. A very small amount of manganese trioxide other than Li-Mn-based composite oxides was detected by X-ray analysis (XRD) in the composite. The average particle size of the synthesized product measured by a laser particle size distribution analyzer was 10 m, and the specific surface area was 7.7 m ² Zg.

The obtained Li-Mn-based composite oxide having a spinel structure was dispersed in an ethanol solvent and pulverized with a wet pole mill to adjust the average particle diameter to 0.5 xm. As a result of the measurement, the pulverized powder did not contain more than 3 large particles, and the specific surface area was 27 Srr ^ Zg. Bismuth oxide having an average particle size of 2; m was added and mixed with the pulverized powder so that the atomic ratio of BiZMn became 0.026, and the mixture was mixed with Spartan manufactured by Fuji Baudal Co., Ltd. The mixture was stirred and granulated with Luza-RMO-6H.

1.5 parts by mass of polyvinyl alcohol as a granulation auxiliary was dissolved in an aqueous solution and added to 100 parts by mass of the mixed powder of the Li-Mn-based composite oxide and bismuth oxide, and the mixture was granulated for 16 minutes. The obtained granules were lightly crushed and crushed by a mixer, and sized by an air classifier to an average particle diameter of 15 / m. The tap density of the granulated product after sizing was 1.65 gZml.

The obtained granules are kept in the air at 500 ° C for 2 hours, and after degreasing (decomposing polyvinyl alcohol), the temperature is raised in the air at 200 ° C / hr and the temperature is raised to 7500 ° C. After holding for 0 hour, a positive electrode active material was obtained. It was confirmed by the ICP-AES method (inductively coupled plasma emission spectroscopy) that the cathode active material produced here contained the Bi element of the bismuth oxide corresponding to the charged composition ratio.

The average porosity of the obtained positive electrode active material was 11.2%. Also, the positive electrode active material The tap density of the material was 1.96 gZm1, the crystallite size was 880 angstroms, and the lattice constant was 8.233 angstroms.

Using the positive electrode active material described above, a coin-type battery was manufactured as follows. The positive electrode active material, carbon black as a conductive material, and polyvinylidene fluoride dissolved in N-methyl-2-pyrrolidone are kneaded at a mass ratio of 80:10:10, applied on aluminum foil, and pressed under pressure. To make a positive electrode. A lithium foil having a predetermined thickness was used as the negative electrode. The electrolyte used was 1 propylene carbonate and dimethyl carbonate at a volume ratio: a mixture in a mixing ratio of 2, was obtained by dissolving the L i PF ₆ at a concentration of 1 mole Z liters. Using these positive and negative electrodes, a polypropylene separator, an electrolyte, and a glass filter, a 2016 coin-type battery was fabricated.

The battery prepared by the above method was subjected to a charge / discharge cycle test at 60 at a charge / discharge rate of 1 C (2.5 hours after the start of charging) and a voltage range of 3.0 to 4.2 V for 100 cycles. Charge and discharge were repeated. Table 1 shows the initial discharge capacity and the capacity retention (%) after 100 cycles. Example 2

The operation was performed in the same manner as in Example 1 except that the manganese source in the synthesis conditions of the Li-Mn-based composite oxide was electrolytic manganese dioxide, and the porosity of secondary particles, tap density, crystallite size, lattice constant, The electrode characteristics were evaluated. The results are shown in Table 1. Example 3

Mixing manganese carbonate, lithium carbonate and aluminum hydroxide with a pole mill so that the atomic ratio of Li / Mn / A1 becomes 1.02: 1.967: 0.013, and heating rate in air atmosphere Increase from room temperature to 650 ° C at 200 ° C / hr The mixture was heated and maintained at 650 ° C for 4 hours to synthesize a Li-Mn-based composite oxide. In the composite, a very small amount of manganese trioxide was detected by XRD in addition to the Li-Mn-based composite oxide. The average particle size of the synthesized product measured by a laser particle size distribution analyzer was 10.

The obtained Li-Mn-based composite oxide was pulverized to an average particle diameter of 0.5, and boron oxide was added so that the atomic ratio of BZ Mn became 0.0208, and the mixture was granulated. Next, the same operation as in Example 1 was performed except that the degreased granules were fired at 750 ° C for 0.5 hr. The results are shown in Table 1. Example 4

The same operation as in Example 3 was carried out, except that the atomic ratio of BZMn was 0.009, and the degreased granules were fired at 760 for 0.5 hr. The results are shown in Table 1. Example 5

The same operation as in Example 3 was carried out except that the atomic ratio of BZMn was 0.006, and the degreased granules were fired at 770 ° for 0.5 hr. The results are shown in Table 1. Example 6

The same operation as in Example 1 was performed except that the degreased granules were fired at 760 ° C for 20 hours. The results are shown in Table 1. Example 7

Bismuth oxide was changed to tungsten trioxide, and tungsten trioxide was added at an atomic ratio of WZMn of 0.0208, and granulated material after degreasing Was carried out in the same manner as in Example 1 except that was fired at 750 ° C. for 20 hours. The results are shown in Table 1. Example 8

The Li-Mn-based composite oxide synthesized in Example 1 was further heated from room temperature to 750 ° C at an air heating rate of 200 ° C / hr, It was crystallized while keeping hr. Thereafter, the Li-Mn-based composite oxide crystallized in Example 1 was used, and bismuth oxide was changed to boron oxide. The procedure was performed in the same manner as in Example 1 except that the granules were added and the degreased granules were fired at 75 ° C. for 0.5 hr. The results are shown in Table 1. Example 9

Before granulation L i one Mn-based average particle diameter of 3. 5 m as a composite oxide, except that specific surface area was used as a 1 0 m ² / g, was prepared as in Example 3. The results are shown in Table 1. Example 10

Synthesized by mixing manganese carbonate, lithium carbonate, and aluminum hydroxide using a pole mill so that the atomic ratio of LiZMn / A1 is 1.03: 1.967: 0.013. Example 3 was carried out in the same manner as in Example 3, except that the obtained Li-Mn-based composite oxide was used. The results are shown in Table 1. Positive electrode active material 60 ° C battery performance Sintering accelerator After degreasing ■ fcH says -r 100 cycle

No. Lattice constant Circularity Needle ratio Initial capacity

Additive molar ratio Density Specific surface area

Firing porosity

Condition nop,

C miscellaneous

P ω% g / ml m ² / g AA mAh / g% \

Example 1 750 ° C X20hr 11.2 1.96 1.8 880 8.233 0.76 1.31 129 84 Port 03

Bi / Mn

Example 2 750 ° C X20hr 12.0 1.93 1.8 890 8.234 0.75 1.33 118 78

0.0026

B / Mn

Example 3 750 ° C X 0.5hr 6.5 2.16 1.2 780 8.232 0.78 1.28 127 85

0.0208

B / Mn

Example 4 760 ° C X 0.5hr 2.3 2.33 1.0 910 8.231 0.78 1.29 125 83

0.0090

B / Mn

Example 5 770. CX0.5hr 1.8 2.35 0.9 930 8.23 0.77 1.28 126 81

0.0060

Bi / Mn

Example 6 760 ° C X20hr 9.1 2.05 1.2 910 8.231 0.78 1.29 115 87

0.0026

W / Mn

Example 7 750 ° C X20hr 6.1 2.18 1.1 800 8.239 0.78 1.28 124 76

0.0208

B / Mn

Example 8 750 ° C X 0.5hr 9.8 2.02 1.5 820 8.240 0.76 1.30 128 80

0.0208

B / Mn

Example 9 750 ° C X 0.5hr 8.5 2.07 1.3 750 8.233 0.79 1.31 126 85

0.0208

B / Mn

Example 10 750 ° C X 0.5hr 6.3 2.15 1.2 750 8.228 0.76 1.29 116 89

0.0208

Example 1 1

The same operation as in Example 1 was performed except that the degreased granules were fired at 830 ° C for 20 hours. The results are shown in Table 2. Example 12

Manganese carbonate, lithium carbonate, and aluminum hydroxide were mixed using a pole mill so that the atomic ratio of Li / Mn / A1 was 0.99: 1.96: 0.013. Example 3 was carried out in the same manner as in Example 3, except that a Li-Mn-based composite oxide was used. The results are shown in Table 2. Example 13

The procedure was performed in the same manner as in Example 3, except that the average particle diameter after granulation was adjusted to 65 im. The results are shown in Table 2. Example 14

The operation was performed in the same manner as in Example 1 except that the atomic ratio of BiZMn was set to 0.0020. The results are shown in Table 2. Observation of the granulated, calcined, and sized positive electrode active material using a scanning electron microscope (X15,000 magnification) revealed that the particles were round particles as shown in Fig. 1. Figure 2 shows the particle size distribution of these particles. Comparative Example 1

The same operation as in Example 1 was performed except that the average particle diameter of the Li-Mn-based composite oxide before granulation was 6.0 m. The results are shown in Table 2. Comparative Example 2 A mixture of electrolytic manganese dioxide and lithium carbonate with an atomic ratio of Li of 0.51 and an average particle size of 20 zm is mixed with a ball mill, and the heating rate in the atmosphere is 100 ° C / hr up to 760 ° C. The temperature was raised and maintained at 760 ° C for 24 hours to synthesize a positive electrode active material. The obtained positive electrode active material was evaluated in the same manner as in Example 1. The results are shown in Table 2. Comparative Example 3

The procedure was performed in the same manner as in Example 1 except that granulation was performed without adding a sintering accelerator. Table 2 shows the results. Comparative Example 4

The procedure was performed in the same manner as in Example 3 except that the granulated product was fired at 750 ° C for 20 hours. The results are shown in Table 2.

Table 2

Example 15

Manganese carbonate, lithium carbonate and aluminum hydroxide were mixed in a pole mill so that the atomic ratio of Li / MnZA 1 was 1.02: 1.967: 0.013, and the heating rate in the atmosphere was 200. The temperature was raised from room temperature to 650 ° C at a rate of ° C / hr, and kept at 650 ° C for 4 hours to synthesize a Li-Mn-based composite oxide. In the compound, a very small amount of manganese trioxide was detected by XRD in addition to the Li-Mn-based composite oxide. The average particle size of the synthesized product measured by a laser set particle size distribution analyzer was 10 im.

In the obtained Li-Mn-based composite oxide,

Boron oxide was added so that the atomic ratio became 0.0208, dispersed in an ethanol solvent, and pulverized with a wet ball mill to reduce the average particle diameter to 0.1. Using the obtained pulverized powder, stirring and granulation was performed with Spartan Reuser RMO_6H manufactured by Fuji Baudal Co., Ltd.

To 100 parts by mass of the pulverized powder of the Li-Mn-based composite oxide and boron oxide, 1.5 parts by mass of polyvinyl alcohol as a granulation aid was dissolved in an aqueous solution and added, and the mixture was granulated for 16 minutes. The obtained granules were lightly crushed and crushed by a mixer, and sized by an air classifier to an average particle size of 15 m. The tap density of the granulated product after sizing was 1.60 g / m1.

The obtained granules were kept in the air at 500 ° C for 2 hours to be degreased (decompose polyvinyl alcohol). The sintering shrinkage onset temperature of the degreased granulated powder was measured with a thermomechanical tester, and was 660 ° C.

Next, the degreased granulated powder was sintered using a rotary kiln under the following conditions. Set the temperature in the soaking zone of the rotary kiln to 780 ° C, and set the supply speed of granulated powder, the rotation speed of the kiln and the inclination of the kiln so that the degreased granulated powder passes through the soaking zone in 3 minutes. did. The time required for the granulated powder to enter the soaking zone from the input port and the time required from exiting the soaking zone to the outlet of the rotary kiln were both 6.3 minutes. The average porosity of the obtained positive electrode active material was 2.1%. Further, when the longest diameter of 500 primary particles was measured from the SEM photograph, the average particle diameter was 0.40 m.

Using the above-mentioned positive electrode active material, a coin-type battery was produced in the same manner as in Example 1. A charge / discharge cycle test at 60 ° C. of the battery prepared by the above method was repeated at 100 charge / discharge cycles at a charge / discharge rate of 1 C and a voltage range of 3.0 to 4.2 V.

Table 3 shows the initial discharge capacity and the capacity retention rate (%) after 100 cycles.

Example 16

The temperature of the soaking zone of the mouth-tally kiln is set at 780 ° C, and the supply speed of granulated powder, the rotation speed of the rotary kiln and the inclination are set so that the degreased granulated powder passes through the soaking zone in 9 minutes. Other than that, it carried out similarly to Example 15. The results are shown in Table 3.

Example 17

Mix manganese carbonate, lithium carbonate and vapor phase alumina so that the atomic ratio of Li / Mn / A1 becomes 1.02: 1.967: 0.013. The temperature was raised from room temperature to 650 ° C at an ambient heating rate of 200 ° C / hr, and the temperature was maintained at 650 ° C for 4 hours to synthesize a Li-Mn-based composite oxide. In the synthesized product, a very small amount of manganese trioxide was detected by XRD in addition to the Li-Mn-based composite oxide. The average particle size of the synthesized product measured by a laser type particle size distribution analyzer was 10 m 2.

Boron oxide is added to the obtained Li-Mn-based composite oxide so that the atomic ratio of BZMn becomes 0.0104, dispersed in ion-exchanged water, and pulverized by a medium stirring type pulverizer. The average particle size was 0.18 xm. Formed into the obtained pulverized slurry Granulation aid (Isoban 104, manufactured by Kuraray Co., Ltd.) was added in an amount of 1.5% by mass based on the Li-Mn-based composite oxide, and dried and granulated by a disk-rotating spray dryer. The granulated product was spherical particles having an average particle size of 18.3, and the tap density was 1.54 gZm1.

The obtained granules were kept in the air at 500 at 2 hours for degreasing and then sintered under the same conditions as in Example 15 using a rotary kiln.

The average porosity of the obtained positive electrode active material was 1.7%, the average particle size was 0.27 m, the tap density was 2.40 gZm1, and the specific surface area measured by the BET method was 0.8 m ² / g. . Table 3 shows the characteristics of the coin-type battery manufactured using this positive electrode active material in the same manner as in Example 15. Example 18

Example 15 was carried out in the same manner as in Example 15 except that the temperature of the soaking zone of the mouth-to-mouth kiln was set to 850 ° C. The results are shown in Table 3. Example 19

Example 17 was carried out in the same manner as in Example 17 except that the temperature in the soaking zone of the mouth-to-talry kiln was set to 850 ° C. The results are shown in Table 3. Comparative Example 5

The temperature of the degreased granules is increased from 650 ° C at a rate of 10 ° CZin, held at 750 ° C for 0.5 hr, sintered, and then cooled to 650 ° C at a rate of 10 ° CZmin. Except for this, the procedure was the same as in Example 15. The obtained positive electrode active material was evaluated in the same manner as in Example 15. Table 3 shows the results. Comparative Example 6 The operation was performed in the same manner as in Comparative Example 5 except that the sintering was performed at 750 ° C. for 20 hours. Table 3 shows the results. Comparative Example 7

The temperature of the soaking zone in the mouth kiln is set at 780 ° C, and the supply speed of the granulated powder and the mouth soaking degreased granulated powder pass through the soaking zone in 0.5 minutes. And the time required for the granulated powder to enter the soaking zone from the input port, and the time required from exiting the soaking zone to the rotary kiln outlet are both 1.5 minutes. Except for this, the procedure was the same as in Example 15. The results are shown in Table 3.

Table 3

Positive electrode active material 60 ° C battery performance Primary particles 100 cycles

No. Sintering conditions Porosity Tap density Specific surface area Lattice constant Circularity Needle ratio Initial capacity

Average size Capacity retention% g / ml μ mm ² Z g A mAh / g%

780 ⁰ CX3 minutes

Example 15 120 ° C / min 2.1 2.35 0.40 0.8 8.233 0.77 1.31 127 90 Rotary kiln

780. CX9 minutes

Example 16 120 ° C // min 1.6 2.44 0.50 0.4 8.236 0.75 1.29 128 87 Rotary quinolene

780 ° CX3min

Example 17 120 ° C / min 1.7 2.40 0.28 0.8 8.235 0.99 1.02 127 91 Rotary kiln

850 ° C for 9 minutes

Example 18 120 ° CZ min 1.4 2.51 2.66 0.3 8.237 0.73 1.29 128 86 Rotary kiln

850 ° C for 9 minutes

Example 19 120 ° C / min 1.3 2.52 2.41 0.2 8.237 0.75 1.29 128 87 Rotary kiln

750 ° CX0.5hr

Comparative example 5 io ° cZ min 6.5 2.14 0.55 1.2 8.232 0.78 1.28 127 85 Box furnace

750 ° CX20hr

Comparative Example 6 10 ° C / min 2.3 2.33 0.84 0.3 8.235 0.78 1.29 125 70 Box furnace

780. CX 0.5 min

Comparative Example 7 lSCTCZ 13.1 1.92 0.19 2.1 8.233 0.77 1.28 118 81 Rotary kiln

Analysis of shape measurement results of granulated particles

The circularity (circularity = 4 π [area Ζ (perimeter) ² ]) and needle ratio (needle ratio) of the secondary particles produced in Example 11 and Comparative Example 17 shown in Table 13 The positive electrode active material manufactured in the example based on the measurement result of the absolute length of the needle (Ζdiagonal width) may be characterized by a circularity of 0.7 or more and a needle ratio of 1.35 or less. I understand. Industrial applicability

The positive electrode active material of the present invention is essentially different in that it performs granulation and sintering as compared with the conventionally known secondary particles utilizing cohesive force, and is compared with the positive electrode active material obtained by the conventional method. Therefore, the particles are dense and spherical, and have excellent filling properties to the electrodes, and also have the effect of increasing the initial capacity and capacity retention rate even in a high-temperature environment as a secondary battery.

According to the method for producing a positive electrode active material of the present invention, by adding a sintering aid to the Li-Mn-based composite oxide that generates a melt in a high temperature region, the secondary particles can be densified. In addition, excellent battery performance can be obtained even when the conventional method is grown to a crystallite size that deteriorates the initial capacity and cycle characteristics. When the secondary particles of the conventional method are densified, the primary particle size grows larger than 0.5 m, and the initial capacity and the cycle characteristics deteriorate. This is solved by the method of the present invention in which a sintering accelerator is added to the Li-Mn-based composite oxide, and a positive electrode active material having high filling properties and excellent battery performance can be obtained. Since the lithium ion secondary battery of the present invention uses a positive electrode active material having excellent filling properties, it has excellent initial capacity and capacity retention at high temperatures.

Claims

Claims A positive electrode active material for a lithium secondary battery mainly composed of Li-Mn-based composite oxide particles having a spinel structure has the following formula:

Porosity (%) = (AZB) x 100 (1)

(A is the total cross-sectional area of the pores included in the cross-section of one secondary particle, and B is the cross-sectional area of one secondary particle.) A positive electrode active material for a lithium ion secondary battery, characterized in that: 2. The value of the average porosity is 10% or less, and the average particle size of the primary particles is 0.

2. The positive electrode active material for a lithium ion secondary battery according to claim 1, which has a thickness of 2 to 3 tm.

3. The positive electrode active material for a lithium ion secondary battery according to claim 1, wherein the tap density of the positive electrode active material is 1.9 gZml or more.

4. The positive electrode active material for a lithium ion secondary battery according to claim 3, wherein the positive electrode active material has a tap density of 2.2 gZm 1 or more.

5. The positive electrode active material for a lithium ion secondary battery according to claim 1, wherein the positive electrode active material has a crystallite size of 400 to 960 angstroms.

6. The positive electrode active material for a lithium ion secondary battery according to claim 1, wherein the lattice constant of the positive electrode active material is 8.240 angstroms or less.

7. The positive electrode active material is mainly composed of a Li-Mn-based composite oxide having a spinel structure. Or an element or a compound containing an element whose oxide can be an oxide or an oxide that melts at a temperature of 550 ° C to 900 ° C, or an oxide or a solid that dissolves or reacts with lithium or manganese or The positive electrode active material for a lithium ion secondary battery according to claim 1, wherein the positive electrode active material is a granulated and sintered active material comprising an element or a compound containing an element which can be an oxide.

8. Compounds containing elements or elements that can become oxides or oxides that melt at a temperature of 550 ° C to 900 ° C, or oxides or oxides that dissolve in or react with lithium or manganese in solid solution compounds containing it obtained element or element is, B i, B, W, Mo, a compound containing at least one of elemental or elements selected from the group consisting of P b, or B ₂ 0 ₃ and L i F 8. The positive electrode active material for a lithium ion secondary battery according to claim 7, which is a compound obtained by combining MnF ₂ and Li F.

9. In a method for producing a positive electrode active material for a lithium ion secondary battery mainly composed of a Li-Mn-based composite oxide having a spinel structure, the pulverized product of the Li-Mn-based composite oxide having a spinel structure has the following properties: ° (: an element or a compound containing an element that can become an oxide or oxide that melts at a temperature of up to 900 ° C, or an oxide or oxide that dissolves or reacts with lithium or manganese to melt. A method for producing a positive electrode active material for a lithium ion secondary battery, comprising a step of adding, mixing, and granulating the obtained element or a compound containing the element.

10. The method for producing a positive electrode active material for a lithium ion secondary battery according to claim 9, further comprising a step of sintering the granulated material in addition to the granulating step.

1 1. In addition to the granulation process, the granulated material must be at least 10 Raise the temperature at a rate of at least 100 ° C / min to a temperature higher than 0 ° C, hold it at that temperature for 1 to 10 minutes, and then reduce the temperature to the sintering start temperature at a rate of at least 100 ° C Zmin. 10. The method for producing a positive electrode active material for a lithium secondary battery according to claim 9, comprising a step of sintering.

2. The method for producing a positive electrode active material for a lithium secondary battery according to claim 11, wherein the sintering is carried out using a Rho-Ea kiln.

13. The sintering step comprises: at least one element selected from the group consisting of Bi, B, W, Mo, and Pb or a compound containing an element on the surface of the Li-Mn-based composite oxide particles; or ₂ 0 ₃ and L i the method for producing a positive electrode active material for a lithium ion secondary battery according to claim 10, wherein the F is a compound or MnF ₂ which combines performed by sintering melting the compound in combination with i F.

14. The method for producing a positive electrode active material for a lithium ion secondary battery according to claim 9, wherein the average particle diameter of the ground material of the Li-Mn-based composite oxide having a spinel structure is 5 Pm or less.

15. The method for producing a positive electrode active material for a lithium ion secondary battery according to claim 9, wherein the pulverized product of the Li-Mn-based composite oxide having a spinel structure has an average particle diameter of 3 m or less.

16. The method for producing a positive electrode active material for a lithium ion secondary battery according to claim 9, wherein the granulation step is performed by a spray granulation method, a stirring granulation method, a compression granulation method, or a fluidized granulation method. .

17. In the granulation step, as a granulation auxiliary, acrylic resin, copolymer of len and maleic anhydride, polyvinyl alcohol, polyethylene glycol, polyvinylpyrrolidene, hydroxypropylcellulose, methylcellulose, corn starch, 10. The method for producing a positive electrode active material for a lithium ion secondary battery according to claim 9, wherein at least one organic compound selected from the group consisting of gelatin and lignin is used.

18. The positive electrode active material for a lithium ion secondary battery according to claim 17, further comprising a degreasing step at a temperature of 300 ° C. to 550 ° C. in the air or in a gas flow atmosphere containing oxygen. The method of manufacturing the substance.

19. A positive electrode active material for a lithium secondary battery obtained by the method according to any one of claims 9 to 18.

20. An electrode paste comprising the positive electrode active material for a lithium ion secondary battery according to any one of claims 1 to 8.

21. A positive electrode for a lithium ion secondary battery, comprising the positive electrode active material for a lithium ion secondary battery according to any one of claims 1 to 8 or claim 19.

22. A lithium secondary battery comprising the positive electrode for a lithium ion secondary battery according to claim 21.

23. The lithium ion secondary battery according to claim 22, wherein the lithium ion secondary battery is a coin battery, a wound battery, a cylindrical battery, a square battery, or a stacked battery.