JP2002358959A - Positive electrode active substance, its manufacturing method and paste, positive electrode and non-aqueous electrolyte secondary battery using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positive electrode active substance that has suppressed elusion of Mn from the manganic acid system positive electrode active substance and can achieve excellent battery characteristics, and a positive electrode paste using the same, and a positive electrode made of this paste and a non-aqueous electrolyte secondary battery using the positive electrode. SOLUTION: In the manufacturing method of a positive electrode active substance that contains a conductive polymer having a π electron conjugate system structure and a manganese oxide, the manganese oxide is a complex oxide made of mainly lithium, manganese and oxygen, and the polymeric compound is chemically oxidation-polymerized and the conductive polymer is coated on the surface of the complex oxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a positive electrode active material, a method for producing the same, a positive electrode paste using the positive electrode active material, a positive electrode, and a non-aqueous electrolyte secondary battery.

[0002]

2. Description of the Related Art A positive electrode active material of a non-aqueous electrolyte secondary battery (or abbreviated as "non-aqueous secondary battery") has a spinel structure which is low in cost, free from resource restrictions and excellent in safety. Li
LixMn _{3 in} which Mn ₂ O ₄ or Mn element is replaced by another element M
-x-yMyO ₄ , LiMnO ₂ having a layered structure and the like are currently being studied. However, these Mn-based positive electrode active materials have a serious problem that, when charge and discharge are repeated, Mn is eluted and the electric capacity is reduced, and the capacity is further greatly reduced at high temperatures. As a method of solving such a problem, a method of forming a composite with a polymer has been proposed.

For example, JP-A-5-290618 discloses an intercalating material / soluble conductive polymer material composite coated with a soluble conductive polymer of polyaniline, the same substituted derivative and a polythiophene derivative. After dispersing the positive electrode active material in a solution in which the polymer is dissolved,
A production method in which a solvent having low solubility is added to coprecipitate with the positive electrode active material has been proposed.However, in the composite obtained by this method, the surface of the positive electrode active material cannot be uniformly coated, so that charging and discharging are repeated. And Mn are eluted to cause a decrease in electric capacity, which is not a sufficient improvement measure.

Japanese Patent Application Laid-Open No. 11-40157 proposes a battery electrode in which the surface of a composite oxide particle of a transition element and lithium is treated with a water-soluble polymer such as polyvinyl alcohol, and a method for producing the same. However, since the wettability between the water-soluble polymer and the composite oxide is low, the coating on the surface of the positive electrode active material becomes insufficient, and furthermore, there is a problem that electrolysis easily occurs.

Japanese Patent Application Laid-Open No. 63-102162 discloses a conductive polymer and an inorganic chalcogenite or a composite of a conductive polymer and an inorganic oxide for a positive electrode. A polymer containing aniline or pyrrole or a copolymer containing such a structure is disclosed as an inorganic oxide, for example, cobalt oxide. Was insufficient and Mn was eluted.

Japanese Patent Application Laid-Open No. 9-35716 discloses a positive electrode using manganese oxide as an active material, a negative electrode using lithium as an active material, a mixture containing LiCF ₃ SO ₃ or LiPF ₃ as a solute and containing ethylene carbonate or ethylene carbonate. And a non-aqueous electrolyte having a solvent as an electrolyte, wherein at least one member selected from the group consisting of polyaniline, polypyrrole, polyacetylene, polythiophene, polyphenylene sulfide and polyparaphenylene on a manganese oxide such as LiMnO ₂ . Although a positive electrode active material to which a polymer is added is disclosed, there is a problem that Mn is eluted.

[0007] When a spinel-type composite oxide mainly composed of lithium, manganese and oxygen among manganese oxides is used as a positive electrode active material of a non-aqueous secondary battery, the charge / discharge of the electrolyte in the electrolytic solution takes place. It is pointed out that a problem that Mn is eluted from the positive electrode active material occurs. Therefore, in order to avoid contact between the positive electrode active material and the electrolyte, a method of coating the surface of the positive electrode active material with an insulating material has been adopted. Since the electron conductivity accompanying the electrochemical reaction with the electrolytic solution is hindered, this has been a major problem. As described above, in the coating method disclosed in the prior art, the surface of the positive electrode active material cannot be uniformly coated, or the capacity per unit weight of the positive electrode active material becomes small, and the expected coating effect is not obtained. Was.

[0008]

SUMMARY OF THE INVENTION According to the present invention, there is provided a positive electrode active material capable of suppressing the elution of Mn from a manganate-based positive electrode active material and achieving unprecedented excellent battery characteristics, and a positive electrode paste using the same. A non-aqueous electrolyte secondary battery (a non-aqueous secondary battery) comprising a positive electrode prepared from the paste, a positive electrode, a negative electrode including a negative electrode active material capable of inserting and extracting lithium ions, and a non-aqueous electrolyte solution in which an electrolyte is dissolved. (Also referred to as a battery).

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies in view of the problems of the prior art, and as a result, have found that lithium,
In a non-aqueous secondary battery using a positive electrode having a positive electrode active material containing a manganese-based composite oxide mainly composed of manganese and oxygen and a conductive polymer having a π-electron conjugated structure, as a positive electrode active material, The problem was solved by using a positive electrode active material in which a polymerizable compound was partially (or entirely) deposited (coated) on the surface of a composite oxide by chemical oxidative polymerization, and the present invention was achieved. That is, the present invention has been solved by the following means.

That is, (1) a method for producing a positive electrode active material containing a conductive polymer having a π-electron conjugated structure and a manganese oxide, wherein the manganese oxide is a composite oxide mainly containing lithium, manganese and oxygen. A method for producing a positive electrode active material, comprising chemically oxidatively polymerizing a polymerizable compound and coating the surface of the composite oxide with a conductive polymer. (2) lithium complex oxide mainly comprising manganese and _{oxygen, LiMn 2 O 4, LixMn 3} -X O 4 (0.9 <
_{x <1.2), Li 1 +} X Mn 2-xy M y O 4 ( wherein, M is M
a part of n is replaced by at least one kind of different element M selected from the group consisting of Cr, Co, Al, Ni, V, Fe, Mg and Ti, and x is -0.1 <x ≦ Range of 0.2, y is 0
<Y ≦ 0.2. ), LiMnO ₂ and Lix
Mn ₂ -x-yMyO ₂ (wherein M is a part of Mn element such as Cr, Co,
Al is replaced by at least one different element M selected from the group consisting of Al, Ni, V, Fe, Mg, and Ti, and x is-
Y is in the range of 0.1 <x ≦ 0.1, and y is in the range of 0 <y ≦ 0.1. 3. The method for producing a positive electrode active material according to item 1, wherein the method includes one kind of composite oxide selected from the above).

(3) The positive electrode active material as described in (1) or (2) above, wherein the composite oxide mainly containing lithium, manganese and oxygen is a composite oxide containing a spinel-type oxide having a lattice constant of 8.240 ° or less. Manufacturing method. (428) The positive electrode active material according to any one of the above items 1 to 3, wherein the composite oxide mainly containing lithium, manganese, and oxygen is a composite oxide containing particles having a primary particle diameter of 0.1 µm to 1 µm. Production method. (5) The composite oxide according to any one of (1) to (5) above, wherein the composite oxide mainly composed of lithium, manganese and oxygen is a composite oxide containing a granulated product having a particle diameter of 3 μm to 50 μm.
13. The method for producing a positive electrode active material according to item 10.

(6) When the granulated material is 550 ° C. to 9 ° C.
Oxide which melts at a temperature of 00 ° C. or an element which can be an oxide thereof, or a compound containing the element, or an oxide which can be dissolved or reacted with lithium or manganese to melt or an element which can become an oxide thereof, or this element 6. The method for producing a positive electrode active material according to the above item 5, which is obtained by adding and mixing a sintering promoting aid of a compound containing (7) The production of the positive electrode active material according to any one of the above items 1 to 6, wherein the composite oxide mainly containing lithium, manganese, and oxygen includes a composite oxide having pores in a range of 30 ° to 400 °. Method.

(8) The method according to any one of (1) to (7) above, wherein the means for chemically oxidatively polymerizing the polymerizable compound comprises reacting the composite oxide by contacting the oxidizing agent with the polymerizable compound in a solvent. 9. The method for producing a positive electrode active material according to claim 1. (9) MnO ₂ , Fe (III) compound, anhydrous aluminum chloride / cuprous chloride, alkali metal persulfate,
Ammonium persulfate, peroxide, potassium permanganate, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), tetrachloro-1,4-benzoquinone, tetracyano-1,4-benzoquinone 9. The method for producing a positive electrode active material according to item 8, wherein the positive electrode active material is at least one selected from the group consisting of iodine and bromine.

(10) MnO ₂ is a spinel-type LiMn ₂ O _{4 of} a composite oxide mainly composed of lithium, manganese and oxygen.
10. The method for producing a positive electrode active material according to the above item 9, wherein MnO ₂ is formed on the surface of the composite oxide by reacting an acid with the system composite oxide. (11) The method for producing a positive electrode active material according to the above item 10, wherein MnO ₂ is λ-MnO ₂ . (12) MnO ₂ reacts an acid with a spinel-type LiMn ₂ O ₄ -based composite oxide of a composite oxide mainly composed of lithium, manganese and oxygen, and then reacts the composite oxide at 200 ° C. or higher.
Item 10. The method for producing a positive electrode active material according to item 9, wherein the β-MnO ₂ is obtained by heat treatment at a temperature of less than 400 ° C.

(13) The acid is hydrochloric acid, hydrobromic acid, hydroiodic acid, hydrofluoric acid, nitric acid, chlorosulfuric acid, fluorosulfuric acid, amidosulfuric acid, sulfuric acid, phosphoric acid, perchloric acid, methanesulfonic acid,
Ethanesulfonic acid, propanesulfonic acid, benzenesulfonic acid, toluenesulfonic acid, naphthalenesulfonic acid,
13. The method for producing a positive electrode active material according to any one of the above items 10 to 12, which is at least one selected from naphthalenedisulfonic acid, trifluoroacetic acid, trichloroacetic acid, formic acid, and oxalic acid. (14) The polymerizable compound is selected from the group consisting of aniline, a five-membered heterocyclic compound, isothianaphthene, 1,3-dihydroisothianaphthene, 1,3-dihydroisothianaphthene-2-sulfoxide and derivatives thereof. 14. The method for producing a positive electrode active material according to any one of the above items 1 to 13, which is at least one selected material.

(15) The polymerizable compound is represented by the following general formula (I)

Embedded image(Where R¹, R^TwoAre each independently a hydrogen atom, carbon number 1
To 6 linear or branched saturated or unsaturated
Hydrocarbon group, linear or branched having 1 to 6 carbon atoms
Saturated or unsaturated alkoxy group, hydroxyl group, halogen atom
Child, nitro group, cyano group, trihalomethyl group, phenyl
Or a substituted phenyl group, or R ¹And R^TwoIs
Bonding to each other at any position to form at least one or more 5
A two- or seven-membered ring forming a saturated or unsaturated cyclic structure;
A valent group may be formed. X is S, O, Se, Te or
NR^ThreeAnd R^ThreeIs a hydrogen atom, a linear chain having 1 to 6 carbon atoms
Or branched saturated or unsaturated hydrocarbon groups,
A phenyl group, or a straight or branched chain having 1 to 6 carbon atoms
Represents a saturated or unsaturated alkoxy group. R¹, R^Two
And R^ThreeIn the chain of the alkyl or alkoxy group represented by
Represents a carbonyl bond, an ether bond, an ester bond,
It may contain a mid bond or an imino bond. (1)
14. The method for producing a positive electrode active material according to any one of
Law.

(16) A polymerizable compound represented by the following general formula (II)
I)

Embedded image (Wherein R ⁴ and R ⁵ are each independently a hydrogen atom, a linear or branched saturated or unsaturated hydrocarbon group having 1 to 6 carbon atoms, or a hydrocarbon group having 1 to 6 carbon atoms) Represents a substituent which bonds to each other at an arbitrary position to form a cyclic structure of at least one or more 5- to 7-membered saturated hydrocarbon ring containing two oxygen elements, and the cyclic structure is substituted. The method for producing a positive electrode active material according to any one of the above items 1 to 13, which includes a compound having a vinylene bond which may be substituted and a compound having a phenylene structure which may be substituted.

(17) The method for producing a positive electrode active material according to any one of items 1 to 13, wherein the polymerizable compound is pyrrole. (18) When the amount of the conductive polymer is P (mass%) with respect to the composite oxide mainly composed of lithium, manganese, and oxygen, the composite composed mainly of lithium, manganese, and oxygen is deposited. The P / S ratio is in the range of 5 × 10 ⁻³ ≦ P / S ≦ 10 with respect to the specific surface area S (m ² / g) of the oxide, any one of the preceding items 1 to 17, 3. The method for producing a positive electrode active material according to item 1. (19) The coating amount P (% by mass) of the conductive polymer is 0.05
ＰP ≦ 10, wherein
9. The method for producing a positive electrode active material according to any one of 8. (20) The method for producing a positive electrode active material according to the above (10) to (13), wherein the polymerizable compound is pyrrole, and the amount of the acid to be added is 8 gram equivalent or less per 1 mol of pyrrole.

(21) A positive electrode active material produced by the method for producing a positive electrode active material according to any one of the above items 1 to 20. (22) A positive electrode active material having a MnO ₂ layer on the surface and comprising a composite oxide mainly composed of lithium, manganese, and oxygen coated with a conductive polymer generated by chemical oxidation polymerization. (23) The positive electrode active material according to the above item 22, wherein the composite oxide mainly composed of lithium, manganese, and oxygen is a spinel-type LiMn ₂ O ₄ -based composite oxide.

(24) The positive electrode active material according to any one of the above items 21 to 23, wherein the shape coated with the conductive polymer is granular. (25) A paste for a positive electrode, comprising a solvent that dissolves or swells the positive electrode active material, the conductivity-imparting agent, the binder, and the organic binder described in the above items 21 to 24. (26) A positive electrode comprising the positive electrode active material, the conductivity-imparting agent, the binder, and the current collector according to the above items 21 to 24. (27) A non-aqueous electrolyte secondary battery comprising a positive electrode containing the positive electrode active material described in 21 to 24 above, an electrolyte containing Li ions, a non-aqueous electrolyte, and a negative electrode capable of inserting and extracting Li ions.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION A positive electrode active material obtained by the method for producing a positive electrode active material of the present invention comprises a composite oxide mainly composed of lithium (Li), manganese (Mn) and oxygen (O) and a π-electron conjugated system. It is a composite containing a conductive polymer having a structure. The method for producing a positive electrode active material of the present invention is a method for producing a positive electrode having a π-electron conjugated structure on a part or the whole surface of the composite oxide by chemically polymerizing a polymerizable compound in the presence of the composite oxide. It is characterized by coating (depositing) molecules. At this time, an oxidizing agent capable of polymerizing the polymerizable compound can be used for the chemical polymerization.

The composite oxide mainly composed of lithium, manganese and oxygen used in the present invention includes LiMn.
O ₂ , LiMn ₂ O _4, and compounds having a chemical structure in which a part of Mn is replaced by a different element can be exemplified. In the present invention, LiMn having a spinel structure is particularly preferred.
₂ O ₄ , LixMn _3-X O ₄ (0.9 <x <1.2) and the Mn element are represented by Cr, Co, Al, Ni, V, Fe, M
g, Li 1 _{+ X} substituted with at least one other element selected from the group consisting of Ti or the like (abbreviated as M) Mn _2-xy M _y
O ₄ (-0.1 <x ≦ 0.2, 0 <y ≦ 0.
2) (these are also collectively referred to as spinel-type LiMn ₂ O ₄ -based composite oxides), LiMnO ₂ having a layered structure, and its Mn element are Cr, Co, Al, Ni, V, Fe, M
g, LixMn ₂ -x-yMyO ₂ substituted with at least one different element M selected from the group consisting of Ti (here, -
0.1 <x ≦ 0.1, 0 <y ≦ 0.1) and the like are preferably used.

Spinel type LiMn_TwoO_FourUsing composite oxide
If it is, the lattice constant is 8.240 ° or less.
Below, preferably below 8.235 °, more preferably
A composite oxide having a temperature of 8.233 ° or less is preferable. Lattice constant is 8.
When the temperature exceeds 240 °, the capacity maintenance rate of the battery decreases sharply.
I will. In addition, the LixMn_Two-x-yMyO_TwoThe concrete
For example, Li_1.02Mn_1.88Al _0.10O_Four, Li
_1.00Mn_0.95Ni_0.05O_TwoEtc.). Of the present invention
In the method for producing a positive electrode active material, L having a large amount of Mn elution is used.
iMn_1.5Ni_{0 .Five}O_Four, LiMn_1.5Co_0.5O_Four, LiM
n_1.5Cr_0.5O_Four, LiMn_1.5Fe_0.5O_Four5V class such as
It is particularly effective for high potential positive electrode active materials.

The primary particle diameter of the oxide preferably used in the method for producing a positive electrode active material of the present invention is 0.1 μm.
A range of m to 1 μm, preferably 0.2 μm to 0.5 μm is good. In the present invention, the primary particles in these states are 3 μm to 50 μm, preferably 5 μm to 3 μm.
It may be granulated to 0 μm and used as a base material of the coating positive electrode active material.

In the present invention, there are no particular restrictions on the method for producing a composite oxide mainly composed of lithium, manganese and oxygen, a composite oxide having a spinel structure, and the starting materials thereof. In the method for producing a composite oxide, a mixture of a manganese compound and a lithium compound, or a mixture to which a compound containing a different element that can be substituted for manganese is further added, is heated to a temperature of 300 ° C. to 850 ° C. in the air or an oxygen gas flow atmosphere. What is necessary is just to bake below at least 1 hour.

The crystallinity of the composite oxide having a spinel structure mainly composed of lithium, manganese and oxygen is not particularly limited, and an unreacted lithium compound and manganese oxide may remain. On the other hand, the starting material manganese sources include electrolytic manganese dioxide (EMD), chemically synthesized manganese dioxide (CMD), manganese trioxide, manganese tetroxide, manganese oxyhydroxide, manganese carbonate,
Manganese nitrate or the like can be used, and lithium hydroxide such as lithium hydroxide, lithium carbonate, and lithium nitrate can be used. Preferred manganese sources include manganese carbonate, which is highly reactive with lithium.

The composite oxide mainly composed of lithium, manganese and oxygen used in the present invention is obtained by pulverizing the calcined product and then obtaining the pulverized particles (which are primary particles or aggregates of primary particles). Sintering accelerator (granulation accelerator).
May be used, and granulated and dense granulated particles may be used. Here, the dense granulated particles refer to one of the oxides.
It means that there are no or few voids between the secondary particles, and it can be produced by the following method using a sintering accelerator.

The method of mixing the crushed and pulverized composite oxide particles mainly composed of lithium, manganese and oxygen with the sintering promoting aid is not particularly limited. For example, a medium stirring type pulverizer, a ball mill, a paint shaker, A mixing mixer or the like can be used. The mixing method may be either a dry method or a wet method. When the composite oxide is crushed and pulverized, a sintering accelerator may be added and mixing may be performed at the same time.

The sintering accelerator which can be used is lithium,
Disintegration of composite oxide particles mainly composed of manganese and oxygen
What is necessary is just to be able to sinter the pulverized particles for granulation,
More preferably, a compound that melts at a temperature of 900 ° C. or less, for example, an oxide that can be melted at a temperature of 550 ° C. to 900 ° C., an element that can become the oxide, or a compound (precursor) containing the element or lithium or Any oxide may be used as long as it is an oxide which forms a solid solution with or reacts with manganese and melts, or an element which can become the oxide or a compound containing the element.

For example, sintering accelerators include Bi, B,
Compounds containing elements such as W, Mo, Pb, etc. may be mentioned, and these compounds may be used in any combination, or a compound obtained by combining B ₂ O ₃ and LiF or a compound obtained by combining MnF ₂ and LiF Is also used.
Among them, compounds containing the elements Bi, B, and W are particularly preferable because they have a large sintering shrinkage effect.

For example, Bi compounds include bismuth trioxide, bismuth nitrate, bismuth benzoate, bismuth oxyacetate, bismuth oxycarbonate, bismuth citrate, bismuth hydroxide and the like. Examples of the B compound include boron trioxide, boron carbide, boron nitride, and boric acid. Examples of the W compound include tungsten dioxide and tungsten trioxide.

The amount of the sintering accelerator is 0.0001 in terms of the added metal element per mole of Mn in the composite oxide.
It is preferably in the range of -0.05 mol. If the amount of the added metal element is less than 0.0001 mol, there is no sintering shrinkage effect, and if it exceeds 0.05 mol, the initial capacity of the active material becomes too small. Preferred is 0.00
5 to 0.03 mol.

The sintering accelerator may be used in the form of a powder or a liquid dissolved in a solvent. When added in the form of a powder, the average particle size of the sintering accelerator is preferably 50 μm or less, more preferably 10 μm or less, and still more preferably 3 μm or less. The sintering promoting aid is preferably added before granulation / sintering, but the granulated material may be impregnated and sintered at a temperature at which the sintering promoting aid can be melted after granulation.

Next, the granulation method will be described. As the granulation method, spray granulation method using the sintering accelerator,
Examples of the method include a fluidized-granulation method, a compression-granulation method, and a stirring-granulation method. Agitation granulation and compression granulation are particularly preferred because the density of secondary particles increases and spray granulation results in a perfectly spherical granulated particle shape. Examples of the agitation granulator include a vertical granulator manufactured by Powrex Co., Ltd. and a Spartan Luzer manufactured by Fuji Paudal Co., Ltd., and examples of the compression granulator include Kurimoto Tekko Co., Ltd. Roller compactor MRCP-200 type.
Examples of the spray granulator include a mobile minor type spray dryer such as Ashizawaniro Atomizer Co., Ltd.

In the present invention, the size of the granulated particles used for the positive electrode active material is not particularly limited. If the average particle size of the granulated particles is too large, it may be lightly crushed and pulverized immediately after granulation or after sintering, classified and sized to obtain a desired particle size. In order to increase the granulation efficiency, an organic granulation aid may be added. Examples of the granulation aid include an acrylic resin, a copolymer of isobutylene and maleic anhydride, polyvinyl alcohol, polyethylene glycol, polyvinyl pyrrolidene, hydroxypropyl cellulose, methyl cellulose, corn starch, gelatin, lignin and the like.

The addition amount of the granulation assistant is preferably 5 parts by mass or less, more preferably 100 parts by mass of the composite oxide having a spinel structure mainly composed of lithium, manganese and oxygen and 100 parts by mass of the sintering accelerator. Is 2 parts by mass or less.

Next, a method of firing the granulated particles will be described. The method of degreasing the granulated particles is performed by holding the granulated particles in a temperature range of 300 ° C. to 550 ° C. for 10 minutes or more in the atmosphere or in a gas atmosphere containing oxygen. The defatted granule preferably has a carbon residue of 0.1% by mass or less. The degreased granulated particles are sintered by holding them in a temperature range of 550 ° C. to 900 ° C. for 1 minute or more in the atmosphere or an atmosphere containing oxygen. In addition, the sintering of the particles of the granulated material without using the above-described organic-based granulation aid should be similarly performed by sintering and shrinking in the air or in a gas atmosphere containing oxygen, and the secondary particles should be densified. Can be.

Next, a second embodiment of the present invention will be described.
, Composite oxidation mainly composed of lithium, manganese and oxygen
Is spinel type LiMn_TwoO_FourSurface of composite oxide with acid
After the treatment, the composite oxidation
Positive electrode characterized in that a conductive polymer is coated on an object surface
Provided is a method for producing an active material. That is, the present inventors
Spinel type LiMn_TwoO_Four-Based complex oxide surface treated with acid
Λ-MnO formed by_TwoAs an oxidizing agent for polymerizable compounds
I found a way to use it. So far, spinel type LiMn
_TwoO_FourIs treated with an aqueous solution of an acid, the LiMn _TwoO_FourIs
λ-MnO_Two(Journal of
 Solid State Chemistry 39, 142-147 (1981)). Immediately
For example, when nitric acid is used,

According to the following reaction formula (1), 2LiMn ₂ O ₄ + 4HNO ₃ → 2LiNO ₃ + Mn (NO ₃ ) ₂ + 3λ-MnO ₂ + 2H ₂ O (1) Is known to change to λ-MnO ₂ . The present invention provides a method for producing a positive electrode active material using λ-MnO ₂ formed on the surface as an oxidizing agent.

In the method for producing a positive electrode active material of the present invention, conversion of the spinel structure to λ-MnO ₂ is detected in accordance with the above reaction formula (1), and the completion of the reaction by the acid is detected by detecting the pH of the acidic solution. be able to. Furthermore, the conversion of the spinel structure can be designed and implemented from the number of moles of the acid to be added. That is, in this acid treatment, the concentration of the acid to be added, the molar amount of the acid, and the reaction time can be determined according to the formation amount (molar amount) of λ-MnO ₂ . The conversion mol% from the spinel structure to λ-MnO ₂ by the acid treatment is preferably 1 to 13 mol% based on the spinel structure composite oxide.
And more preferably 2 to 7 mol%, and still more preferably 3 to 5 mol%. If the conversion ratio (mol%) to λ-MnO ₂ is less than 1 mol%, the expected effect accompanying the surface treatment is not exhibited, and if it exceeds 13 mol%, the initial discharge capacity of the non-aqueous secondary battery when the battery is formed. Too much decrease,
Not preferred.

Next, the present inventors, as a third embodiment of the method for producing a cathode active material of the present invention, used a method in which λ-MnO ₂ formed on the surface of a composite oxide by an acid treatment was treated at 200 ° C.
As described above, by heating (heat treatment) at a temperature of less than 400 ° C., the surface layer of the composite oxide is converted into a composite oxide substantially consisting of β-type MnO ₂ , which is used as an oxidizing agent for a polymer. I found that I can do it. That is, this β-type M
It has been found that nO _{2 is} also used as an oxidizing agent for a polymerizable compound, like λ-MnO ₂ . Where "substantially"
What is necessary is that the surface layer of the composite oxide having a spinel structure mainly composed of lithium, manganese, and oxygen contains at least one β-type MnO ₂ lattice.

In the present invention, the composite oxide used as the positive electrode active material is a composite oxide mainly composed of lithium, manganese and oxygen, preferably the composite oxide is a spinel type composite oxide, Preferably, prior to polymerization of the polymerizable compound, the surface thereof is treated with an acid to form a λ-type MnO _2.
A composite oxide having a phase is preferably used, or a composite oxide converted from a λ-type MnO ₂ phase to a β-type MnO ₂ phase by heat treatment is used.

When a composite oxide having a β-type MnO ₂ phase is used as a positive electrode active material on the surface of the thus-produced granulated product (including secondary particles) or the primary particles, the non-aqueous The secondary battery has a feature that the initial discharge capacity is large and the discharge capacity is small even when charge and discharge are repeated in an environment of 60 ° C., and the surface layer thickness of the β-type MnO ₂ phase is, for example, 2
0.02 μm to 0.22 μm when the secondary particles are 20 μm,
Preferably, those formed in the range of 0.05 μm to 0.08 μm are preferable.

In the method for producing a positive electrode active material of the present invention, the λ-MnO ₂ on the surface of the composite oxide having the spinel structure is reduced to 20%.
By performing heat treatment at a temperature of 0 ° C. or more and less than 400 ° C., it is characterized in that it is converted into β-MnO ₂ that is stable against battery charge / discharge.
-MnO ₂ hardly changes from β-MnO ₂ to 40
At 0 ° C. or more, lithium of the spinel structure composite oxide diffuses to the surface, and the surface of the spinel structure composite oxide cannot be stabilized. Whether or not Li has diffused to the surface is determined by 20
This can be determined by the fact that the lattice constant becomes larger than the lattice constant when heat treatment is performed at 0 ° C. or more and less than 400 ° C. The heat treatment may be performed for at least 5 minutes.

In the present invention, by subjecting a complex oxide having a spinel structure mainly composed of lithium, manganese and oxygen to an acid treatment, it can be modified into particles having pores in the range of 30 ° to 400 °. . By using the composite oxide having such a pore state as the positive electrode active material, it is considered that local current density on the surface of the positive electrode active material during charge and discharge can be reduced, and the cycle characteristics are extremely improved. Can be

In general, in order to obtain excellent battery characteristics,
It is said that a positive electrode active material having a small specific surface area (1 m ² / g or less) is more desirable because it is necessary to suppress a side reaction of the positive electrode active material. However, surprisingly, although the specific surface area of the positive electrode active material of the present invention is as large as 1.5 m ² / g or more, excellent battery characteristics can be obtained as never before. As a fourth embodiment of the method for producing a positive electrode active material of the present invention, after forming λ-MnO ₂ or β-MnO ₂ on the surface layer of a composite oxide mainly composed of lithium, manganese and oxygen, A method for producing a positive electrode active material, comprising coating a conductive polymer on the surface of the composite oxide while promoting the polymerization reaction of a polymerizable compound by adding an oxidizing agent. When the oxidizing power of λ-type MnO ₂ and β-type MnO ₂ is insufficient for the polymerization of the polymerizable compound, the addition of the oxidizing agent is particularly effective.

Acids optionally used in the method for producing a positive electrode active material of the present invention include hydrochloric acid, hydrobromic acid, hydroiodic acid,
Hydrofluoric acid, nitric acid, chlorosulfuric acid, fluorosulfuric acid, amidosulfuric acid, sulfuric acid, phosphoric acid, perchloric acid, methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, benzenesulfonic acid, toluenesulfonic acid, naphthalenesulfonic acid, naphthalenedisulfonic acid And at least one selected from trifluoroacetic acid, trichloroacetic acid, formic acid, and oxalic acid. Of these, nitric acid and perchloric acid are particularly preferably used.

The polymerizable compound to be used is not particularly limited as long as it can form a π-electron conjugated chemical structure after polymerization, and is preferably, but not limited to, aniline, a five-membered heterocyclic compound, isothianaphthene, 1,3- At least one selected from the group consisting of dihydroisothianaphthene, 1,3-dihydroisothianaphthene-2-sulfoxide and derivatives thereof is used.

These polymerizable compounds may be further exemplified by the following general formula (I)

Embedded image(Where R¹, R^TwoAre each independently a hydrogen atom, carbon number 1
To 6 linear or branched saturated or unsaturated
Hydrocarbon group, linear or branched having 1 to 6 carbon atoms
Saturated or unsaturated alkoxy group, hydroxyl group, halogen atom
Child, nitro group, cyano group, trihalomethyl group, phenyl
Or a substituted phenyl group, or R ¹And R^TwoIs
Bonding to each other at any position to form at least one or more 5
A two- or seven-membered ring forming a saturated or unsaturated cyclic structure;
A valent group may be formed. X is S, O, Se, Te or
NR^ThreeAnd R^ThreeIs a hydrogen atom, a linear chain having 1 to 6 carbon atoms
Or branched saturated or unsaturated hydrocarbon groups,
A phenyl group, or a straight or branched chain having 1 to 6 carbon atoms
Represents a saturated or unsaturated alkoxy group. R¹, R^Two
And R^ThreeIn the chain of the alkyl or alkoxy group represented by
Represents a carbonyl bond, an ether bond, an ester bond,
It may contain a mid bond or an imino bond. )
Compound, and more preferably,

The following general formula (II):

Embedded image(Where R¹, R^TwoAre each independently a hydrogen atom, carbon number 1
To 6 linear or branched saturated or unsaturated
Hydrocarbon group, linear or branched having 1 to 6 carbon atoms
Saturated or unsaturated alkoxy group, hydroxyl group, halogen atom
Child, nitro group, cyano group, trihalomethyl group, phenyl
Or a substituted phenyl group, or R ¹And R^TwoIs
Bonding to each other at any position to form at least one or more 5
A two- or seven-membered ring forming a saturated or unsaturated cyclic structure;
A valent group may be formed. R^ThreeIs a hydrogen atom and has 1 carbon atom
6 to 6 linear or branched saturated or unsaturated charcoals
A hydride group, a phenyl group, or a linear group having 1 to 6 carbon atoms
Or a branched, saturated or unsaturated alkoxy group.
You. R¹, R^TwoAnd R^ThreeAn alkyl group or alkoxy represented by
A carbonyl bond, an ether bond, an S
It may contain a tell bond, an amide bond, and an imino bond. )
And a compound represented by the following general formula (III):

[0051]

Embedded image (Wherein R ⁴ and R ⁵ are each independently a hydrogen atom, a linear or branched saturated or unsaturated hydrocarbon group having 1 to 6 carbon atoms, or a hydrocarbon group having 1 to 6 carbon atoms) Represents a substituent which bonds to each other at an arbitrary position to form a cyclic structure of at least one or more 5- to 7-membered saturated hydrocarbon ring containing two oxygen elements, and the cyclic structure is substituted. And a phenylene structure which may be substituted.) Are also effectively used.

Further, the above-mentioned general formula (I) and the above-mentioned general formula (I
Preferred R ¹ and R ² in I) are each independently a hydrogen atom, a linear or branched saturated or unsaturated hydrocarbon group having 1 to 3 carbon atoms, or a linear chain having 1 to 3 carbon atoms. R ³ is a hydrogen atom, a linear or branched saturated or unsaturated, saturated or unsaturated alkoxy group, halogen atom, nitro group, cyano group, trihalomethyl group. An unsaturated hydrocarbon group or a linear or branched saturated or unsaturated alkoxy group having 1 to 3 carbon atoms is preferred. The general formula (III)
As preferred R ⁴ and R ⁵ in, each independently represents a hydrogen atom, a linear or branched saturated or unsaturated hydrocarbon group having 1 to 3 carbon atoms, or a hydrocarbon group having 1 to 3 carbon atoms. A substituent which bonds to each other at an arbitrary position to form a cyclic structure of at least one or more 5- to 7-membered saturated hydrocarbon containing two oxygen elements is preferable.

In the present invention, aniline, pyrrole, N-methylpyrrole, 3
-Methylpyrrole, 3,4-dimethylpyrrole, 3,4
-Dioxythiophene and isotinanaphthene are preferred because they provide a conductive polymer having high conductivity.

In the method for producing a positive electrode active material of the present invention,
Examples of the oxidizing agent used include MnO ₂ , FeC
Fe such as l ₃ , FeClO ₄ , Fe (organic acid anion) salt
(III) compound, anhydrous aluminum chloride / cuprous chloride, alkali metal persulfate, ammonium persulfate, peroxide, potassium permanganate, 2,3-dichloro-
5,6-dicyano-1,4-benzoquinone (DDQ),
Tetrachloro-1,4-benzoquinone, tetracyano-
At least one selected from the group consisting of 1,4-benzoquinone, iodine, and bromine is used.

Next, a method for producing a positive electrode active material in which a conductive polymer is coated (deposited) on a composite oxide mainly composed of lithium, manganese and oxygen will be described in more detail below. In the method for producing a positive electrode active material containing a conductive polymer and a manganese oxide, the manganese oxide is a composite oxide mainly composed of lithium, manganese, and oxygen, and the powder or the granulated product thereof or the molding thereof. The body can be immersed in a solution in which the oxidizing agent is dissolved, and then the conductive polymer can be deposited on the surface of the composite oxide while the polymerizable compound is dropped.

The solution that can be used is not particularly limited as long as it can dissolve the oxidizing agent.
Primary, secondary, and tertiary alcohols having 1 to 6 carbon atoms, oxygen-containing compounds such as tetrahydrofuran (THF) and dioxane, nitrile compounds such as acetonitrile and benzonitrile, nitro compounds such as nitromethane and nitrobenzene, and dimethylformaldehyde ( DMF), dimethyl sulfoxide (DMSO), at least one selected from the group consisting of chlorine-containing compounds such as chloroform, dichloromethane and tetrachloroethane, and aromatic compounds such as benzene, toluene and xylene can be used. In the production method of the present invention, the dispersion concentration of the composite oxide in the solvent may be any economically usable dispersion concentration, for example, 0.0001 to 1 g / m3 per 1 ml of the solvent.
1, preferably 0.001 to 0.5 g / ml, more preferably 0.01 to 0.3 g / ml.

The concentration of the polymerizable compound used in the production method of the present invention may be a concentration capable of chemically polymerizing, for example, 10 ^-6 to 1 mol, preferably 10 ^-5 to 1 mol.
The concentration is set to 0.5 molar, more preferably 10 ^{-4 to} 0.2 molar. The oxidizing agent is used in an amount of 1 to 10 molar equivalents, preferably 1 to 5 molar equivalents, particularly preferably 1 to 2 molar equivalents, based on the polymerizable compound to be dropped. If the molar amount is less than 1 molar equivalent, unreacted polymerizable compound remains. If the molar amount exceeds 10 molar equivalents, not only a large amount of the oxidizing agent remains but also the polymerizable compound is further oxidized, resulting in a poor conductivity. It is not preferable in terms of degree. The polymerizable compound has a coating amount P (% by mass) of a polymer described later and a specific surface area S (m) of a composite oxide mainly composed of lithium, manganese, and oxygen.
² / g) and is controlled so as to satisfy the ratio P / S.

The reaction temperature for carrying out the polymerization reaction of the polymerizable compound is determined by the combination of the polymerizable compound used, the solvent and the oxidizing agent, and is not particularly limited.
The reaction is usually carried out at a temperature in the range of -20 to 150 ° C, preferably 0 to 100 ° C, particularly preferably 10 to 80 ° C. At a reaction temperature lower than −20 ° C., the polymerization reaction is slow, and the solvent that can be used is restricted in terms of the freezing point. At a reaction temperature higher than 150 ° C., a polymerization reaction is too much, and a polymer having an expected chemical structure cannot be obtained with a secondary side reaction. The reaction time for carrying out the polymerization reaction of the polymerizable compound is determined by the combination of the polymerizable compound used, the solvent, the oxidizing agent and the reaction temperature, and is not limited, but is usually from 10 seconds to 24 hours, preferably from 1 minute to The reaction is performed for 10 hours, particularly preferably for 5 minutes to 6 hours. If the reaction time is shorter than 10 seconds, the polymerization reaction is not sufficient and the amount of the polymer is insufficient. If the reaction time is longer than 24 hours, the time required for the production becomes longer, and it is not economical. In the polymerization method, the polymer remaining on the solvent without depositing on the surface of the composite oxide mainly composed of lithium, manganese and oxygen is separated by sieving, filtration, washing or the like.

Next, a method of depositing on an acid-treated spinel-type LiMn ₂ O ₄ -based composite oxide using pyrrole as an example of the polymerizable compound will be described. A powder of the spinel-type LiMn ₂ O ₄ -based composite oxide, a granulated product thereof, or a molded product thereof is added to pure water, and the following predetermined amount of acid is added dropwise with stirring. The amount of the acid is preferably added dropwise within a range of, for example, 8 gram equivalents or less per 1 mol of pyrrole. After the acid dripping,
A predetermined amount of pyrrole is added as an aqueous solution with stirring, and the surface of the composite oxide is chemically oxidized and polymerized. The polypyrrole-coated composite oxide is separated by filtration and dried to obtain the positive electrode active material of the present invention.

In the method for producing a positive electrode active material according to the present invention,
The deposition of the conductive polymer is performed using a composite mainly composed of lithium, manganese, and oxygen, assuming that the amount of the conductive polymer coated per unit weight of the composite oxide mainly composed of lithium, manganese, and oxygen is P (% by mass). With respect to the specific surface area S (m ² / g) of the oxide, the P / S ratio is 5 × 10 ⁻³ ≦ P / S ≦ 10, preferably 0.
3 ≦ P / S ≦ 3, more preferably 1 ≦ P / S ≦ 3
It is desirable to carry out within the range. If the P / S is less than 5 × 10 ⁻³ , the surface of the composite oxide mainly composed of lithium, manganese and oxygen cannot be said to be sufficient, and if the P / S exceeds 10, the capacity per positive electrode active material will be insufficient. Becomes smaller.

More preferably, the polypyrrole coating amount P (% by mass) is 0.05 ≦ P ≦ 10, preferably 0.2 ≦ P ≦ 5, based on the composite oxide mainly containing lithium, manganese and oxygen. More preferably, 0.5 ≦ P (% by mass)
≦ 2. If the coating amount is less than 0.05% by mass,
It becomes difficult to sufficiently cover the surface of the positive electrode active material.
This is because if it exceeds the mass%, the capacity per positive electrode active material is affected.

In the present invention, the amount of polypyrrole deposited and its identification can be determined by TG-MAS (differential thermal balance-mass spectrometry simultaneous measurement device). When the amount of acid is dropped within the range of 8 gram equivalent or less per 1 mol of pyrrole, the capacity per cathode active material becomes small when the amount of acid exceeds 8 gram equivalent. Preferably, the acid amount is 5 to 8 gram equivalents, more preferably 5 to 6 gram equivalents, per mol of pyrrole to be added. If the acid amount is less than 5 gram equivalents, all of the added pyrrole cannot be chemically oxidized and polymerized, resulting in a non-uniform coating, and unnecessary pyrrole is apt to remain, thus affecting the capacity per cathode active material and the amount of Mn eluted. Because it gives.

Next, a method of using the positive electrode active material of the present invention as a positive electrode material of a non-aqueous secondary battery will be described. The positive electrode material is prepared by kneading a solution (for example, N-methylpyrrolidone) in which a solution (for example, N-methylpyrrolidone) in which the positive electrode active material, a conductivity imparting agent such as carbon black or graphite, and a binder (binding material) such as polyvinylidene fluoride are dissolved is mixed at a predetermined ratio. Then, it is applied to a current collector as an electrode paste, and then dried and then pressed by a roll press or the like to produce the electrode paste. As the current collector, a known metal current collector such as aluminum, stainless steel, or titanium is used.

As the electrolyte salt in the electrolyte used in the non-aqueous secondary battery of the present invention, a known lithium salt containing fluorine can be used. For example, LiPF ₆ , LiB
F ₄ , LiN (CF ₃ SO ₂ ) ₂ , LiAsF ₆ , LiCF ₃
SO ₃ and LiC ₄ F ₉ SO ₃ 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. The non-aqueous electrolyte of the non-aqueous electrolyte can be used without limitation as long as it is chemically and electrochemically stable and aprotic. For example, dimethyl carbonate, propylene carbonate, ethylene carbonate, methyl ethyl carbonate, methyl propyl carbonate,
Carbonic esters such as methyl isopropyl carbonate, methyl butyl carbonate, diethyl carbonate, ethyl propyl carbonate, diisopropyl carbonate, dibutyl carbonate, 1,2-butylene carbonate, ethyl isopropyl carbonate, and ethyl butyl carbonate are exemplified. 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 tolunitrile; amides such as dimethylformamide; Sulfoxides such as sulfoxide, lactones such as γ-butyrolactone, sulfur compounds such as sulfolane, N-vinylpyrrolidone, N-methylpyrrolidone, and phosphate esters can also be exemplified. Of these, carbonates, aliphatic esters, and ethers are preferred in the present invention.

The negative electrode used in the nonaqueous 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 (graphite) And metal chalcogens can be used.

Next, an example of a method for evaluating electrode characteristics will be described. The cathode active material, Vulcan XC-72 (acetylene black) manufactured by Cabot as a conductive material, and ethylene tetrafluoride resin (PTFE) as a binder at a mass ratio of 50:
The mixture was mixed at a ratio of 34:16 and the mixture was mixed with toluene for 1 hour.
Swell for 2 hours. The swollen mixture is applied onto a current collector made of an aluminum extract band metal, molded under pressure at ² t / cm ² , and toluene is dried to obtain a positive electrode. On the other hand, a lithium foil is used as the negative electrode. As the electrolytic solution, a solution obtained by dissolving LiPF ₆ at a concentration of 1 mol / liter in a mixture of propylene carbonate (PC) and dimethyl carbonate (DMC) at a volume ratio of 1: 2 is used. A separator made of polypropylene is used as the separator, and silica fiber filter paper QR-100 manufactured by Advantech Toyo Co., Ltd. is also used as a reinforcing material for the purpose of preventing micro short circuit caused by dendrite generation of the negative electrode. By using these positive electrode, negative electrode, electrolytic solution, separator and reinforcing material, 2016
A coin-type coin battery is manufactured and placed in a thermostat set at 60 ° C.
Perform 0 charge / discharge cycle tests. Measurement conditions are: constant current constant voltage charge-constant current discharge, charge and discharge rate 1C
(Charge pauses 2.5 hours after the start of charging), scanning voltage 3.
1V to 4.3V.

In the configuration of the secondary battery, a solid polymer electrolyte having ion conductivity can also be used. For example, polyvinylidene fluoride (PVDF) and polyethylene oxide (PEO), thermoplastic polymers such as polyacrylonitrile and their derivatives and the above-mentioned Li salt and / or dissolved in an electrolytic solution, or polyfunctional ethylene oxide such as polyethylene oxide diacrylate A mixture obtained by cross-linking and curing a mixture of an oligomer and the above-mentioned Li salt and / or electrolyte solution by heating or actinic rays is used.

[0068]

EXAMPLE 1 Lithium nitrate and manganese dioxide were mixed in a ball mill and reacted at 800 ° C. for 48 hours in an air atmosphere.
_1.1 Mn _1.9 O ₄ was synthesized. This was pulverized by a ball mill to have a primary particle diameter of 0.4 to 1 μm and an average primary particle diameter of 0.6.
μm, lattice constant 8.231 °, BET specific surface area S = 0.
5 m ² / g of Li _1.1 Mn _1.9 O ₄ powder was obtained. Then, 5 g of this powder was added to 100 ml of pure water, and after stirring for 0.5 hour, 40.2 ml of a 0.1N aqueous solution of nitric acid was stirred while stirring.
(5.4 times gram equivalent of pyrrole) was added dropwise little by little to convert the surface of the spinel-type manganese oxide into λ-MnO ₂ . After dropping, while stirring, 0.05 g of pyrrole
(0.745 mmol) was added to form polypyrrole on the surface of Li _1.1 Mn _1.9 O ₄ . Filtration of the resulting composite of lithium, manganese, manganese oxide mainly composed of oxygen and conductive polymer
After washing and drying at 110 ° C., 4.8 g of a positive electrode active material comprising the composite was obtained.

Next, a part of the obtained positive electrode active material was analyzed by thermogravimetric analysis (abbreviated as TG; from room temperature to 600 ° C. under nitrogen, at a heating rate of 20 ° C./min.). In addition, it was found that all the polypyrrole disappeared due to thermal decomposition, whereby the ratio P corresponding to the polypyrrole coating amount was 1% by mass. The polypyrrole coated on the composite oxide was 0.1%.
It was 047 g. From the above, the P / S ratio was 2. Observation of the obtained positive electrode active material by SEM showed that the surface of the primary particles of the positive electrode active material was covered with granular polypyrrole.

Next, the obtained positive electrode active material was used as a positive electrode active material:
Acetylene black: tetrafluoroethylene resin (PTF
E) = 50: 34: 16 after mixing with a mixer, PTFE was swelled with toluene, applied to an aluminum mesh current collector, and toluene was evaporated, and then 2 t / cm ^2.
To produce a positive electrode material. The obtained positive electrode material was punched into a 30 mm square, and this was used as a positive electrode. LiPF ₆ was added to the nonaqueous electrolyte obtained by mixing the positive electrode, the negative electrode of lithium foil, propylene carbonate (PC) and dimethyl carbonate (DMC) at a volume ratio of 1: 2.
Was dissolved at a concentration of 1 mol / liter, and a non-aqueous secondary battery (hereinafter, referred to as a Lami bag battery) was assembled using an aluminum laminate bag as an outer bag.

The obtained lami bag battery was subjected to a charge / discharge cycle test in a 60 ° C. environment. That is, the test conditions include a charge / discharge rate of 1 C (coulomb) and a voltage range of 3.
The temperature was set at 1 to 4.3 V and the ambient temperature was 60 ° C., and charge and discharge were repeated for 30 cycles. Then, the Lami bag battery was disassembled, and the amount of residual Mn in the electrolytic solution and the negative electrode was analyzed, and the weight% with respect to the total amount of Mn contained in the positive electrode was calculated. The initial capacity of this battery was 110 mAh / g, and the amount of Mn eluted after 30 cycles was as extremely small as 0.31%.

Example 2 Instead of 40.2 ml of 0.1N-nitric acid aqueous solution, 0.1N
The procedure was carried out in the same manner as in Example 1 except that 56.6 ml of an aqueous nitric acid solution (-7.6 g equivalent of pyrrole) was used. As a result, the total polypyrrole coating amount was 0.0
It was 48 g. The initial capacity of the battery was 106 mAh / g, and the elution amount of Mn after 30 cycles was as small as 0.40%. The polypyrrole coating amount of the obtained positive electrode active material was examined by thermogravimetric analysis (TG) in the same manner as in Example 1.
0.99% by mass (P / S = 1.98).

Example 3 Instead of 40.2 ml of 0.1N-nitric acid aqueous solution, 0.1N
The procedure was performed in the same manner as in Example 1 except that 26.1 ml of a nitric acid aqueous solution (3.5 times gram equivalent of pyrrole) was used. As a result, the coated polypyrrole coverage was 0.02
9 g. The initial capacity of the battery is 105 mAh / g,
The Mn elution amount after 30 cycles was as small as 0.51%. The polypyrrole coating amount of the obtained positive electrode active material was examined by thermogravimetric analysis in the same manner as in Example 1. As a result, P = 0.60% by mass (P / S = 1.20).

Example 4 Instead of 40.2 ml of 0.1N aqueous nitric acid solution, 0.1N
Except that 56.3 ml of an aqueous nitric acid solution (equivalent to 5.4 times gram of pyrrole) was used, and 10 ml of an aqueous solution containing 0.07 g of pyrrole was used instead of 10 ml of an aqueous solution containing 0.05 g of pyrrole. Example 1
It carried out similarly to. As a result, the coated amount of the coated polypyrrole was 0.069 g. The initial capacity of the battery is 10
It was 9 mAh / g, and the amount of Mn eluted after 30 cycles was 0.1.
It was extremely low at 19%. The polypyrrole coating amount of the obtained positive electrode active material was determined by thermogravimetric analysis in the same manner as in Example 1. As a result, P = 1.4% by mass (P / S = 2.8).
0).

Example 5 Instead of 40.2 ml of 0.1N-nitric acid aqueous solution, 0.1N
Using 9.2 ml of an aqueous nitric acid solution (5.4 gram equivalents of pyrrole) and 0.0115 g of pyrrole instead of 10 ml of an aqueous solution containing 0.05 g of pyrrole
Was carried out in the same manner as in Example 1 except that 10 ml of an aqueous solution containing was used. As a result, the coated amount of polypyrrole was 0.0115 g. The initial capacity of the battery was 110 mAh / g, and the amount of Mn eluted after 30 cycles was as extremely small as 0.53%. The polypyrrole coating amount of the obtained positive electrode active material was examined by thermogravimetric analysis in the same manner as in Example 1. As a result, P = 0.23% by mass (P / S =
0.46).

Example 6 As a composite oxide mainly composed of lithium, manganese and oxygen, lithium carbonate, manganese carbonate and vapor-phase alumina were mixed in a ball mill and reacted at 750 ° C. in the atmosphere for 20 hours to obtain Li _{1. 02 Al 0.1 Mn 1. 88 O 4} ( specific surface area S =
4.3 m ^{2 /} g, 8.225 °). Using 5 g of this composite oxide, 58.3 ml of a 0.1 N aqueous solution of nitric acid (5.4 gram equivalent of pyrrole) instead of 40.2 ml of a 0.1 N aqueous solution of nitric acid, and The procedure was performed in the same manner as in Example 1, except that 10 ml of an aqueous solution containing 0.115 g of pyrrole was used instead of 10 ml of an aqueous solution containing 0.05 g. As a result, the coating amount of the coated polypyrrole was 0.073 g. The initial capacity of the battery was 122 mAh / g, and the amount of Mn eluted after 30 cycles was 3.1 in the case without pyrrole coating.
It was as low as 0.55% compared to 2%. The amount of polypyrrole coated on the obtained positive electrode active material was subjected to thermogravimetric analysis in the same manner as in Example 1, and was found to be 1.47% by mass (P
/S=0.34).

Example 7 Instead of 9.2 ml of 0.1N aqueous nitric acid solution, 31.2 ml of 1N aqueous nitric acid solution (5.4 equivalents of pyrrole) was used, and 10 ml of aqueous solution containing 0.115 g of pyrrole was used. Was carried out in the same manner as in Example 5, except that 50 ml of an aqueous solution containing 0.387 g of pyrrole was used instead of. As a result, the coated amount of polypyrrole was 0.386 g. Battery initial capacity is 116mAh /
g, and the amount of Mn eluted after 30 cycles is 0.20
% Was extremely low. The polypyrrole coating amount of the obtained positive electrode active material was examined by thermogravimetric analysis in the same manner as in Example 1. As a result, P = 7.74% by mass (P / S = 1.8).
0).

Example 8 A composite carbonate of Ni and Mn and lithium carbonate were mixed in a ball mill, and calcined and crushed and mixed three times at a temperature of 450 ° C. to 700 ° C. (heating rate of 3 ° C./min.) In an air atmosphere. repeat,
Lithium, was synthesized LiNi _{0. 5} Mn ₁ of the composite oxide mainly composed of manganese and _{oxygen. 5} O ₄ (specific surface area S = 7m ² / g). 5 g of this composite oxide was used, and 0.1 N
19.3 ml of 1N aqueous nitric acid solution (5.4 g equivalent of pyrrole) instead of 40.2 ml of aqueous nitric acid solution, 10 m aqueous solution containing 0.05 g of pyrrole
10 m aqueous solution containing 0.24 g of pyrrole instead of 1
and the scan voltage in the charge / discharge cycle test under a 60 ° C. environment was changed to 3.5 to 3.5 V instead of 3.1 to 4.3 V.
Except having set it to 5.2V, it carried out similarly to Example 1.

As a result, the coated amount of polypyrrole was 0.24 g. The initial capacity of the battery was 127 mAh / g, which was not so different from 130 mAh / g without polypyrrole coating. Further, the elution amount of Mn after 30 cycles was drastically reduced to 1.3%, compared to 11% in the case of not coating with pyrrole. The polypyrrole coating amount of the obtained positive electrode active material was determined by thermogravimetric analysis in the same manner as in Example 1. As a result, P was 4.8% by mass (P / S = 0.69).

Comparative Example 1 The procedure of Example 1 was repeated, except that the coating with polypyrrole was not carried out. The initial capacity of the battery is 109mAh / g
However, the eluted amount of Mn after 30 cycles was 1.83%
It was extremely many. Example 9 A powder of Li _1.1 Mn _1.9 O ₄ produced by the method described in Example 1 was used. 5 g of this powder and 0.24 g of ferric chloride
(1.49 mmol) was added to 100 ml of dry chloroform, and then 10 ml of a chloroform solution containing 0.05 g (0.745 mmol) of pyrrole was added dropwise to form polypyrrole on the surface of Li _1.1 Mn _1.9 O ₄ . . The resulting composite of a manganese oxide mainly composed of lithium, manganese, and oxygen and a conductive polymer was filtered, washed with chloroform, and dried at 110 ° C. to obtain 4.5 g of a positive electrode active material including the composite. Was.

The battery was evaluated in the same manner as in Example 1 except for the method for producing the positive electrode active material. As a result, the coated amount of polypyrrole was 0.038 g. The initial capacity of the battery was 114 mAh / g, and the Mn elution amount after 30 cycles was 0.51%. The polypyrrole coating amount of the obtained positive electrode active material was examined by thermogravimetric analysis in the same manner as in Example 1. As a result, P was 0.8% by mass (P / S = 1.
6).

Example 10 Li produced by the method described in Example 1_1.1Mn_1.9O_Fourof
Powder was used. Add 5g of this powder to 100ml of pure water
After stirring for 0.5 hour, while stirring, aqueous 0.1N-sulfuric acid
40.2 ml of the solution (8.1 times gram of isothianaphthene)
(Equivalent) is added dropwise little by little, and spinel-type manganese oxide
Surface of λ-MnO_TwoWas converted to Filter and sort this powder
Λ-MnO_TwoTo β-MnO_TwoConversion to
did. Heat treatment was performed to obtain a positive electrode active material of the present invention. Profit
When the pores of the obtained positive electrode active material were measured, 50 to 32
It turns out that 0 angstrom pores are formed
Was. In addition, the obtained positive electrode active material was measured by an X-ray diffraction method.
As a result, β-MnO _TwoThe derived X-ray peak is 2θ = 3
It was detected near 0 °.

5 g of this composite oxide powder and 0.24 g (1.49 mmol) of ferric chloride were placed under an argon atmosphere.
Pour into 100 ml of dry nitromethane and then J. Org.
Chem. 49 (1984) 10 ml of a nitromethane solution containing 0.067 g (0.5 mmol) of isothianaphthene prepared by the method described in 3382 was added dropwise to Li _1.1 Mn _{1.
Polyisothianaphthene} was formed on the surface of _.9 O ₄ . The obtained composite of a manganese oxide mainly composed of lithium, manganese and oxygen and polyisothianaphthene was filtered, washed with nitromethane, and dried at 110 ° C. to obtain 4.9 g of a positive electrode active material.

The battery was evaluated in the same manner as in Example 1 except for the method for producing the positive electrode active material. As a result, the coating amount of the coated polyisothianaphthene was 0.06 g. The initial capacity of the battery was 109 mAh / g, and Mn after 30 cycles.
The elution amount was 0.50%. The polyisothianaphthene coating amount of the obtained positive electrode active material was determined by thermogravimetric analysis in the same manner as in Example 1. As a result, P = 1.2% by mass (P /
S = 2.4).

Example 11 The same operation as in Example 9 was carried out except that pyrrole was replaced with thiophene. As a result, the coating amount of the coated polythiophene was 0.04 g. The initial capacity of the battery is 109mA
h / g, and the elution amount of Mn after 30 cycles is 0.5
2%. The polythiophene coating amount of the obtained positive electrode active material was examined by thermogravimetric analysis in the same manner as in Example 1.
= 0.8% by mass (P / S = 1.6).

Example 12 The powder of Li _1.1 Mn _1.9 O ₄ produced by the method described in Example 1 was used. 5 g of this powder and 0.40 g (1.49 mmol) of ammonium persulfate were added to 100 parts of (solvent pure water).
10m containing 0.05 g (0.35 mmol) of 3,4-dioxyethylenethiophene
l of isopropanol solution was added dropwise to obtain Li _1.1 Mn _1.9
To form a poly (3,4-dioxyethylenethiophene) (PDET) on the surface of the O _4. The obtained composite of a manganese oxide mainly composed of lithium, manganese, and oxygen and a conductive polymer is filtered, washed with the same solvent, and dried at 110 ° C. to obtain a positive electrode active material composed of the composite. 8 g were obtained. The battery was evaluated in the same manner as in Example 1 except for the method for producing the positive electrode active material.

As a result, the total amount of the coated PDET was 0.05 g. The initial capacity of the battery is 112mAh / g
The Mn elution amount after 30 cycles was 0.48%
Met. When the PDET coverage of the obtained positive electrode active material was examined by thermogravimetric analysis in the same manner as in Example 1, P = 1% by mass
(P / S = 2).

Example 13 Manganese carbonate and lithium carbonate were mixed in a ball mill so that the composition ratio of Li / Mn was 0.51, and the mixture was reacted at 650 ° C. for 4 hours in an air atmosphere. The obtained reaction product was dispersed in water and pulverized with a wet ball mill to adjust the average particle size to 0.15 μm. Bi / Mn is added to this ground powder.
Was mixed with bismuth oxide having an average particle diameter of 2 μm so that the molar ratio became 0.0026, and the mixture was granulated with a Spartan Luzer RMO-6H manufactured by Fuji Paudal Co., Ltd. Polyvinyl alcohol 1.5 as a granulation aid was added to 100 parts by weight of the mixed powder of the crushed reactant and bismuth oxide.
A part by weight was dissolved in an aqueous solution and added, followed by granulation for 16 minutes.
The obtained granules were lightly crushed and pulverized with a mixer, and sized with an air classifier to an average particle diameter of 20 μm. The sized granules are held in the air at 500 ° C. for 2 hours, and then subjected to a degreasing treatment (decomposing polyvinyl alcohol).
By firing for a time, a composite oxide having a spinel structure with a specific surface area of 1.6 m ² / g was obtained.

The battery was evaluated in the same manner as in Example 1 except that the powder of Li _1.1 Mn _1.9 O ₄ described in Example 1 was replaced with this composite oxide. As a result, the coating amount of the coated polypyrrole was 0.049 g. The initial capacity of the battery is 11
5 mAh / g, and the amount of Mn eluted after 30 cycles was:
0.55%. The polypyrrole coating amount of the obtained positive electrode active material was examined by thermogravimetric analysis in the same manner as in Example 1. As a result, P = 0.98% by mass (P / S = 0.6).
1). Tables 1 and 2 summarize the results of Examples and Comparative Examples.

[0090]

[Table 1]

[Table 2]

[0091]

[Effect] By coating a conductive polymer having a π-electron conjugated structure such as polypyrrole on the surface of a composite oxide mainly composed of lithium, manganese and oxygen by chemical oxidation polymerization, a non-aqueous electrolyte with less elution of Mn than ever before. It has been found that a positive electrode active material for a secondary battery can be obtained. In addition, they found that a high-capacity positive electrode active material for a nonaqueous electrolyte secondary battery can be obtained by coating a specific amount of a conductive polymer, and adding a specific amount of an acid during chemical oxidation polymerization. Was. According to the invention of the positive electrode active material for a non-aqueous electrolyte secondary battery, a high-performance non-aqueous electrolyte secondary battery having a high capacity, a small amount of Mn elution even under a high-temperature environment, and excellent cycle characteristics is provided.

[0092]

[Brief description of the drawings]

FIG. 1 is an SEM photograph observed in Example 1.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01M 10/40 H01M 10/40 Z F term (Reference) 4G048 AA04 AA05 AB04 AC06 AD03 AD06 AE05 5H029 AJ02 AJ05 AJ13 AK03 AL04 AL07 AL12 AM03 AM04 AM07 BJ04 BJ12 CJ00 CJ02 CJ08 CJ12 CJ14 DJ00 DJ08 DJ16 DJ17 EJ13 HJ02 HJ05 HJ07 HJ13 HJ14 5H050 AA05 AA07 AA18 BA15 CA00 CA09 CB05 CB08 CB12 DA02 DA09 GA02 GA09 FA10 GA18 GA02 GA09 GA22 GA27 HA02 HA05 HA07 HA13 HA14

Claims (27)

[Claims] 1. A method for producing a positive electrode active material containing a conductive polymer having a π-electron conjugated structure and manganese oxide,
A positive electrode active material, wherein the manganese oxide is a composite oxide mainly composed of lithium, manganese and oxygen, and the surface of the composite oxide is coated with a conductive polymer by chemically oxidizing and polymerizing a polymerizable compound; Manufacturing method. 2. Mainly lithium, manganese and oxygen
The composite oxide is LiMn _TwoO_Four, LixMn_3-XO_Four 
(0.9 <x <1.2), Li_{1 + X}Mn_2-xyM_yO_Four(formula
Where M is Cr, Co, Al, Ni, V, Fe, Mg, Ti
At least one different element M selected from the group consisting of
X is in the range of -0.1 <x ≦ 0.2
The box y is in the range of 0 <y ≦ 0.2. ), LiMnO
_TwoAnd LixMn_Two-x-yMyO_Two(Where M is part of the Mn element
Selected from the group consisting of Cr, Co, Al, Ni, V, Fe, Mg, Ti
Replaced by at least one different element M
X is in the range of −0.1 <x ≦ 0.1, and y is 0 <y ≦
It is in the range of 0.1. 1) a composite oxide selected from
The method for producing a positive electrode active material according to claim 1, comprising:
Law. 3. A composite oxide comprising a spinel-type oxide having a lattice constant of 8.240 ° or less, wherein the composite oxide mainly composed of lithium, manganese and oxygen is a composite oxide.
3. The method for producing a positive electrode active material according to item 1. 4. The positive electrode according to claim 1, wherein the composite oxide mainly composed of lithium, manganese, and oxygen is a composite oxide containing particles having a primary particle size of 0.1 μm to 1 μm. Active material manufacturing method. 5. The composite oxide according to claim 1, wherein the composite oxide mainly composed of lithium, manganese and oxygen is a composite oxide containing a granulated substance having a particle diameter of 3 μm to 50 μm. 3. The method for producing a positive electrode active material according to item 1. . 6. A granulated product comprising a crushed product of a composite oxide mainly composed of lithium, manganese and oxygen at 550 ° C. to 900 ° C.
Containing an oxide or an element that can become an oxide thereof or a compound containing the element, or an oxide that can be dissolved or react with lithium or manganese to melt or an element that can become an oxide thereof or the above element The method for producing a positive electrode active material according to claim 5, wherein the mixture is granulated by adding and mixing a sintering promoting aid of the compound. 7. The positive electrode active material according to claim 1, wherein the composite oxide mainly composed of lithium, manganese and oxygen contains a composite oxide having pores in a range of 30 ° to 400 °. The method of manufacturing the substance. 8. The method according to claim 1, wherein the means for chemically oxidatively polymerizing the polymerizable compound reacts the composite oxide by contacting the oxidizing agent with the polymerizable compound in a solvent. 9. The method for producing a positive electrode active material according to claim 1. 9. The method according to claim 9, wherein the oxidizing agent is MnO ₂ , an Fe (III) -based compound,
Anhydrous aluminum chloride / cuprous chloride, alkali metal persulfate, ammonium persulfate, peroxide, potassium permanganate, 2,3-dichloro-5,6-dicyano-1,
4-benzoquinone (DDQ), tetrachloro-1,4-
Benzoquinone, tetracyano-1,4-benzoquinone,
The method for producing a positive electrode active material according to claim 8, wherein the method is at least one selected from the group consisting of iodine and bromine. 10. MnO ₂ is lithium, MnO ₂ was reacted spinel LiMn ₂ O ₄ based acid composite oxide composite oxide based on manganese, and oxygen is generated on the surface of the composite oxide The method for producing a positive electrode active material according to claim 9, wherein: 11. The method for producing a positive electrode active material according to claim 10, wherein MnO ₂ is λ-MnO ₂ . 12. MnO ₂ reacts an acid with a spinel-type LiMn ₂ O ₄ -based composite oxide composed mainly of lithium, manganese and oxygen, and then reacts the composite oxide at 200 ° C.
As described above, β-M obtained by heat treatment at a temperature of less than 400 ° C.
The method for producing a positive electrode active material according to claim 9, characterized in that a nO _2. 13. The method according to claim 12, wherein the acid is hydrochloric acid, hydrobromic acid, hydroiodic acid,
Hydrofluoric acid, nitric acid, chlorosulfuric acid, fluorosulfuric acid, amidosulfuric acid, sulfuric acid, phosphoric acid, perchloric acid, methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, benzenesulfonic acid, toluenesulfonic acid, naphthalenesulfonic acid, naphthalenedisulfonic acid The method for producing a positive electrode active material according to any one of claims 10 to 12, wherein the method is at least one selected from trifluoroacetic acid, trichloroacetic acid, formic acid, and oxalic acid. 14. The polymerizable compound is aniline, a five-membered heterocyclic compound, isothianaphthene, 1,3-dihydroisothianaphthene, 1,3-dihydroisothianaphthene-2-.
14. The method according to claim 1, which is at least one selected from the group consisting of sulfoxides and derivatives thereof.
13. The method for producing a positive electrode active material according to item 10. 15. A polymerizable compound represented by the following general formula (I):(Where R¹, R^TwoAre each independently a hydrogen atom, carbon number 1
To 6 linear or branched saturated or unsaturated
Hydrocarbon group, linear or branched having 1 to 6 carbon atoms
Saturated or unsaturated alkoxy group, hydroxyl group, halogen atom
Child, nitro group, cyano group, trihalomethyl group, phenyl
Or a substituted phenyl group, or R ¹And R^TwoIs
Bonding to each other at any position to form at least one or more 5
A two- or seven-membered ring forming a saturated or unsaturated cyclic structure;
A valent group may be formed. X is S, O, Se, Te or
NR^ThreeAnd R^ThreeIs a hydrogen atom, a linear chain having 1 to 6 carbon atoms
Or branched saturated or unsaturated hydrocarbon groups,
A phenyl group, or a straight or branched chain having 1 to 6 carbon atoms
Represents a saturated or unsaturated alkoxy group. R¹, R^Two
And R^ThreeIn the chain of the alkyl or alkoxy group represented by
Represents a carbonyl bond, an ether bond, an ester bond,
It may contain a mid bond or an imino bond. )
14. A method for producing the positive electrode active material according to any one of 1 to 13.
Law. 16. A polymerizable compound represented by the following general formula (III): (Wherein R ⁴ and R ⁵ are each independently a hydrogen atom, a linear or branched saturated or unsaturated hydrocarbon group having 1 to 6 carbon atoms, or a hydrocarbon group having 1 to 6 carbon atoms) Represents a substituent which bonds to each other at an arbitrary position to form a cyclic structure of at least one or more 5- to 7-membered saturated hydrocarbon ring containing two oxygen elements, and the cyclic structure is substituted. The method for producing a positive electrode active material according to any one of claims 1 to 13, which includes a compound having a vinylene bond and a compound having a phenylene structure which may be substituted. 17. The method for producing a positive electrode active material according to claim 1, wherein the polymerizable compound is pyrrole. 18. The method according to claim 18, wherein the deposition of the conductive polymer is carried out in the case where the amount of the conductive polymer coated on the composite oxide mainly composed of lithium, manganese and oxygen is P (% by mass). Specific surface area S (m ² /
The method for producing a positive electrode active material according to any one of claims 1 to 17, wherein the P / S ratio is in a range of 5 × 10 ⁻³ ≦ P / S ≦ 10 with respect to g). . 19. The coating amount P (% by mass) of the conductive polymer is
The method for producing a positive electrode active material according to claim 1, wherein the range is 0.05 ≦ P ≦ 10. 20. The method for producing a positive electrode active material according to claim 10, wherein the polymerizable compound is pyrrole, and the amount of the acid to be added is not more than 8 gram equivalent to 1 mol of pyrrole. . 21. A positive electrode active material produced by the method for producing a positive electrode active material according to any one of claims 1 to 20. 22. Lithium having a MnO ₂ layer on its surface,
A positive electrode active material in which a composite oxide mainly composed of manganese and oxygen is coated with a conductive polymer formed by chemical oxidation polymerization. 23. The positive electrode active material according to claim 22, wherein the composite oxide mainly composed of lithium, manganese and oxygen is a spinel type LiMn ₂ O ₄ composite oxide. 24. The positive electrode active material according to claim 21, wherein the shape coated with the conductive polymer is granular. 25. A paste for a positive electrode, comprising a solvent which dissolves or swells the positive electrode active material according to claim 21 to 24, a conductivity imparting agent, a binder and an organic binder. 26. A positive electrode comprising the positive electrode active material according to claim 21, a conductivity-imparting agent, a binder and a current collector. 27. A non-aqueous electrolyte secondary battery comprising a positive electrode containing the positive electrode active material according to claim 21; an electrolyte containing Li ions; a non-aqueous electrolyte; and a negative electrode capable of inserting and extracting Li ions.