JP2003048719A - Method for producing lithium transition metal multiple oxide, positive electrode material for lithium secondary battery, positive electrode for lithium secondary battery and lithium secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of pulverizing lithium transition metal multiple oxide into particulates from submicron to micron order required for the improvement of battery capacity while suppressing their aggligation. SOLUTION: In this method, the lithium transition metal multiple oxide, is pulverized in the presence of a compound whose immersion heat is >=1 J/m<2> .

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a lithium transition metal composite oxide, a positive electrode material for a lithium secondary battery,
The present invention relates to a positive electrode for a lithium secondary battery and a lithium secondary battery.

[0002]

2. Description of the Related Art So-called rocking chair type lithium ion secondary batteries, in which lithium ions move back and forth between a positive electrode and a negative electrode, have been developed. It was used for cellular phones in 1991 and for 8mm camcorders in 1992, and has recently been used for notebook computers and MD disc players. These are mainly for personal use, not for long-term use, and the capacity retention rate (cycle characteristics) was not a major problem.

On the other hand, the environment surrounding us, such as the global warming problem caused by carbon dioxide gas, the air pollution of the city caused by carbon monoxide, nitrogen oxides, etc., is deteriorating. As one of the countermeasures, a hybrid vehicle that uses both an internal combustion engine and a battery has been put into practical use, and an electric vehicle has been studied. Lithium-ion secondary batteries are drawing attention as batteries for these hybrid vehicles and electric vehicles.

[0004] In small power equipment used for personal use, the capacity maintenance rate is a major issue, and when used for industrial applications such as hybrid vehicles and electric vehicles,
Output characteristics were a challenge. The following various technologies are known for the capacity maintenance rate in personal use.

For example, JP-A-8-45498 proposes a method of mixing a lithium manganese composite oxide and a lithium nickel cobalt composite oxide. Further, in order to improve the output characteristics, which is a problem when used for industrial purposes, efforts such as increasing the specific surface area and using a fine particle positive electrode material have been made. Increasing the particle size and the specific surface area in this way is one of the methods for improving the capacity retention rate and the output characteristics.

As a method for producing fine particles, crushing is a powerful method. As a technique for pulverizing particles of submicron to micron order, there are an air stream pulverizer and a media pulverizer. When a jet mill is used, a large amount of gas such as compressed air is required with respect to the weight of the positive electrode material that can be crushed, and there is a problem that the processing cost becomes high. Also,
If compressed air is used during the pulverization, there is a problem that carbon dioxide gas in the air reacts with the lithium composite oxide in the pulverization process and the battery characteristics are deteriorated. If air containing nitrogen gas or decarbonated gas is used to prevent this performance deterioration, the crushing cost further increases, causing a vicious circle.

If a wet media grinder is used as the media grinder, re-aggregation of finely pulverized particles can be prevented, but elution of lithium ions and re-aggregation during drying occur, which is not an appropriate method. Further, when a dry media crusher was used, reaggregation during crushing was severe and solidification of crushed particles occurred, and it was not possible to perform crushing in the submicron to micron order necessary for improving battery performance.

[0008]

Therefore, there has been a demand for a method capable of suppressing aggregation during pulverization of a lithium-transition metal composite oxide and performing pulverization in the submicron to micron order necessary for improving battery performance.

[0009]

As a result of intensive studies to solve the above problems, the present inventors have found that the addition of a compound having an oxygen-containing functional group can suppress the occurrence of aggregation, and completed the present invention. Came to do. That is, the gist of the present invention lies in the following (1) to (16). (1) When pulverizing the lithium-transition metal composite oxide,
A method for producing a lithium-transition metal composite oxide, characterized in that a compound having a heat of immersion with a material to be crushed of 1 J / m ² or more is present. (2) The production method according to (1), wherein the compound having a heat of immersion with the object to be crushed of 1 J / m ² or more is a compound having an oxygen-containing functional group. (3) The production method according to (1) or (2), wherein the lithium-transition metal composite oxide is pulverized with a dry media mill. (4) The oxygen-containing functional group is a hydrophilic group (1) to (3).
The manufacturing method according to any one of 1. (5) The production method according to any one of (1) to (3), wherein the oxygen-containing functional group is a carbonyl group or a hydroxyl group. (6) The amount of the compound having an oxygen-containing functional group is from 0.0001 to 1 to the lithium-transition metal composite oxide 1 in a weight ratio.
The method according to any one of (1) to (5), which is 0.1. (7) The production method according to any one of (1) to (6), wherein the lithium transition metal composite oxide is a lithium cobalt composite oxide, a lithium nickel composite oxide, or a lithium manganese composite oxide. (8) The lithium-transition metal composite oxide is B, Al, F
It is a lithium-nickel composite oxide in which a part of nickel sites is replaced with one or more metal elements selected from e, Sn, Cr, Cu, Ti, Zn, Co, and Mn (1) to
The manufacturing method according to any one of (6). (9) The lithium-transition metal composite oxide is

Embedded image Li _x Ni _1-y M _y O _2- δ (0 <x ≦ 1.5, 0 <y ≦ 1 and M is Co, M
n, Fe, Cr, V, Ti, Cu, Al, Ga, Bi,
Sn, Zn, Mg, Ge, Nb, Ta, Be, B, C
Represents at least one element selected from the group consisting of a, Sc and Zr. ) Is a compound represented by (1) to
The manufacturing method according to any one of (6). (10) The lithium-transition metal composite oxide is

Embedded image Li _x Ni _1-yz Co _y Al _z O ₂ (0.9 ≦ x ≦ 1.1, 0 <y ≦ 1.0, 0 <z ≦ 0.
5, a compound represented by y + z ≦ 1) (1) to
The manufacturing method according to any one of (6). (11) A lithium-transition metal composite oxide produced by the production method according to any one of (1) to (10). (12) A positive electrode material for a lithium secondary battery, which contains the lithium-transition metal composite oxide produced by the production method according to any one of (1) to (10). (13) A positive electrode material for a lithium secondary battery in which a lithium transition metal composite oxide produced by the production method according to any one of (1) to (10) and an unpulverized lithium transition metal composite oxide are mixed. (14) The lithium-transition metal composite oxide is

Embedded image The lithium secondary battery according to (13), which is a compound represented by Li _b Mn _2-a Al _a O ₄ (0 <a ≦ 1.0, 0.9 ≦ b ≦ 1.1). Cathode material. (15) A positive electrode for a lithium secondary battery, containing the positive electrode material for a lithium secondary battery according to any one of (12) to (14) and a binder. (16) A lithium secondary battery having a positive electrode containing the positive electrode material for a lithium secondary battery according to any one of (12) to (14), a negative electrode, and an electrolyte.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, when dry pulverizing a lithium-transition metal composite oxide, the heat of immersion with the substance to be pulverized is 1
It is essential that a compound having a J / m ² or more be present. Immersion heat is a measure showing how the liquid is stabilized by bringing the liquid into contact with the surface of the active substance, and the larger the value, the more stable the liquid is. In the present invention, when a lithium transition metal composite oxide is pulverized, the presence of a specific compound having a heat of immersion with the composite oxide of 1 J / m ² or more causes reaggregation of the pulverized composite oxide. It is possible to suppress the above and perform fine pulverization. In the present invention, the immersion heat is measured, for example, as follows. First, a commercially available microcalorimeter, for example, a microcalorimeter MMC- manufactured by Tokyo Riko Co., Ltd.
5111 attached to the glass ampoule in a range of 0.1 to 1 g and a blank glass ampoule containing no material to be crushed are subjected to vacuum deaeration under the same conditions, and the composite oxidation is performed. Remove deposits from the object surface. The vacuum degassing treatment conditions are, for example, 150 ° C. and 10 ^−2.
Torr, 30 minutes is appropriate.

In the two containers provided in the above-mentioned microcalorimeter, an appropriate amount of the compound (in the present invention, the crushing treatment in the present invention, an amount of an infinite dilution amount with respect to the object to be crushed, for example, several tens of cc. The compound added at the time) was weighed, and the ampoule containing the material to be crushed after vacuum degassing and the blank ampoule after vacuum degassing were preliminarily equipped with a device capable of breaking the ampoule from the outside. Then, each is set in a container, and the whole is stabilized in a constant temperature bath at 25 ° C. for, for example, 12 hours or more. Then 2
Two ampoules are destroyed at the same time, and the change in the temperature with the passage of time is measured with a thermocouple or the like to measure the amount of heat. The calorific value of the blank ampoule is subtracted from the calorific value of the ampoule containing the object to be crushed to obtain the heat of immersion between the object to be crushed and the compound added during the crushing treatment. The immersion heat is expressed by Joule heat per unit area of the crushed object, because the contact state with the compound changes depending on the specific surface area of the crushed object. The object to be crushed may be subjected to the immersion heat measurement before or after the crushing, but the calorific value to be measured is 1 to 5
It is preferable to select the specific surface area and the measured weight so as to be in the range of 0 J.

By allowing a compound having an immersion heat value of 1 J / m ² or more, more preferably ² J / m ² or more to coexist during the pulverization, the pulverization operation can be favorably carried out. Compounds with higher immersion heat have a high effect of stabilizing the surface by adsorbing on the active surface generated during grinding.
Re-aggregation can be prevented. It is more suitable for producing finely divided particles. Specifically, acetone, N-methyl-
Compounds such as 2-pyrrolidone and ethanol are suitable.
Examples of compounds having such an immersion heat range include compounds having the following oxygen-containing functional groups.

The above-mentioned compound having an oxygen-containing functional group means an organic compound having an oxygen-containing functional group. The oxygen-containing functional group, vinyl ether group, alkoxy group, alkoxycarbonyl group, isocyanato group, imide group, ureido group, epoxy group, carboxyl group, carbonyl group, ketene group, glycol group, sulfoxide group, sulfone group, thiocarbonyl group , A nitro group, a nitroso group, a hydroxyamino group, a hydroxyl group, and the like, preferably a hydroxyl group, a carbonyl group, an alkoxy group, an alkoxycarbonyl group, a hydrophilic group such as a carboxyl group, and more preferably a hydroxyl group,
It is a carbonyl group. The oxygen-containing functional group described above can suppress aggregation of the lithium-transition metal composite oxide of the present invention during pulverization. Therefore, a compound having an oxygen-containing functional group exerts its effect as long as it has an oxygen-containing functional group.

Specific examples of the compound having an oxygen-containing functional group include aliphatic saturated alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, propyl alcohol, butyl alcohol, isobutyl alcohol, sec-butyl alcohol and tert-butyl alcohol, Aliphatic unsaturated alcohols such as allyl alcohol,
Alicyclic alcohols such as cyclopentanol, aromatic alcohols such as benzyl alcohol, alcohols such as complex dry alcohols such as furfuryl alcohol, acetone,
Aliphatic saturated ketones such as ethyl methyl ketone, methyl propyl ketone, isopropyl methyl ketone, butyl methyl ketone, isopropyl methyl ketone, pinacolone, diethyl ketone, butyron and diisopropyl ketone, unsaturated ketones such as methyl vinyl ketone and mesityl oxide,
Examples thereof include alicyclic ketones such as cyclobutanone, aromatic ketones such as acetophenone, acetothienone, ketone compounds such as heterocyclic ketones such as 2-acetofuron, and pyrrolidones such as N-methyl-2-pyrrolidone. Preferably,
Methyl alcohol, ethyl alcohol, acetone, N-
It is methyl-2-pyrrolidone.

These immersion heats are the effects of the compound having an immersion heat of 1 J / m ² or more, but they are adsorbed on the surface of the lithium-transition metal composite oxide having high activity immediately after being pulverized,
It is thought that this is due to the effect of reaggregation, but the detailed mechanism is unknown. Further, since the main purpose of use of the crushed product is the positive electrode material for a lithium ion secondary battery, it is desirable that the crushed product easily disperses after crushing. In that sense, it is considered that a selection index such as the boiling point of the organic compound is not too high is also effective. Specifically, the boiling point is 250
A compound having an oxygen-containing functional group having a boiling point of 100 ° C. or lower, preferably 100 ° C. or lower, more preferably 80 ° C. or lower is preferable.

The compound having an immersion heat of 1 J / m ² or more may be in an amount such that aggregation of the lithium-transition metal composite oxide can be suppressed by pulverization, and a new surface layer of the lithium-transition metal composite oxide produced by pulverization is immersed. It may be an amount necessary to cover the heat with a single molecule of the compound of 1 J / m ² or more. Specifically, the weight ratio is usually 0.00001 or more, more preferably 0.0001 or more, still more preferably 0.001 or more, and usually 0.1 or less with respect to the lithium transition metal composite oxide 1. It is more preferably 0.05 or less, still more preferably 0.01 or less. If it is too large, re-agglomeration of the powder may be caused, or a grinding aid may be brought into the battery to cause problems such as deterioration of battery performance.

The compound having an immersion heat of 1 J / m ² or more is preferably added at the start of pulverization of the lithium-transition metal composite oxide. If it does not exist at the start of pulverization, the lithium-transition metal composite oxide starts to agglomerate immediately after the start of pulverization, and even if a compound having an oxygen-containing functional group is added after the agglomeration occurs, its addition effect is not sufficiently exerted. When the lithium-transition metal composite oxide is continuously ground using a bead mill, it is preferable to continuously add the grinding aid together with the lithium-transition metal composite oxide.

Description of Lithium Transition Metal Composite Oxide Examples of the lithium transition metal composite oxide include lithium nickel composite oxide, lithium cobalt composite oxide, lithium manganese composite oxide, lithium iron composite oxide, and the like. Is a lithium cobalt composite oxide, a lithium nickel composite oxide, or a lithium manganese composite oxide, and particularly preferably a layered structure lithium nickel composite oxide having LiNiO ₂ as a basic composition.

The lithium-transition metal composite oxide may further contain, in addition to lithium, the transition metal and oxygen, another element that partially replaces the transition metal. Examples of such other elements in the lithium nickel composite oxide include Co, Mn, Fe, Cr, V, Ti, Cu, Al,
Ga, Bi, Sn, Zn, Mg, Ge, Nb, Ta, B
Metal elements such as e, B, Ca, Sc and Zr can be mentioned, but Al and / or Co are preferable, and both are particularly preferable. A particularly preferable lithium transition metal composite oxide includes a composite oxide containing lithium, nickel, cobalt and aluminum. Such other element has a function of stabilizing the crystal structure, for example, by substituting a part of the nickel site with the other element. As the substitution element for the nickel site, similar to the above, Co, Mn, F
e, Cr, V, Ti, Cu, Al, Ga, Bi, Sn,
Zn, Mg, Ge, Nb, Ta, Be, B, Ca, Sc
And metal elements such as Zr. Of course, a plurality of elements can be substituted. Preferred substitution element is C
o and / or Al, especially Co and Al. Further, a part of oxygen atoms can be replaced with a halogen element such as fluorine.

Such a lithium-transition metal composite oxide of other element substitution type is usually used in the case of a lithium nickel composite oxide having a layered structure.

[0021]

Embedded image Li _x Ni _1-y Me _y O ₂ (Me is a substituting element, 0 <x ≦ 1.5, 0 <y ≦ 1). Here, the preferable substitution element Me
Are Co, Mn, Fe, Cr, V, Ti, Cu,
Al, Ga, Bi, Sn, Zn, Mg, Ge, Nb, T
At least one element selected from the group consisting of a, Be, B, Ca, Sc and Zr can be mentioned, and among them, Al and / or Co. However, the type and composition ratio of the substituting element are not limited to these as long as the crystal structure can be stabilized. Particularly preferable composition of the lithium nickel composite oxide is

[0022]

Embedded image Li _x Ni _1-yz Co _y Al _z O ₂ (0.9 ≦ x ≦ 1.1, 0 <y ≦ 1.0, 0 <z ≦ 0.
It is represented by 5). In any of the above composition formulas, the case where the amount of oxygen has a non-stoichiometric ratio is included. Furthermore, in any of the above cases, it is also possible to substitute a part of the nickel atom sites with lithium by using, for example, a stoichiometric amount or more of lithium as a raw material.

Description of production of lithium-transition metal composite oxide The lithium-transition metal composite oxide can be produced by various conventionally known methods. For example, lithium and transition metal and a part of the transition metal. When substituting the other element with other substituting element, it can be produced by mixing the starting materials containing the substituting element, followed by firing and cooling in the presence of oxygen.
As an example of the lithium nickel composite oxide, the layered lithium nickel oxide (general formula LiNiO ₂ ) described above can be produced by various conventionally known methods.
Lithium, nickel, and optionally, when a part of nickel is replaced with another element, it can be produced by mixing a starting material containing a substituting element, followed by heating and firing in an oxygen atmosphere.

In the above-mentioned production method, a starting material containing a substitution element is not used and a lithium nickel oxide whose Ni site is not substituted is produced. The lithium nickel oxide is used as a starting material containing a substitution metal element. Aqueous solution,
After reacting in a molten salt or in steam, the Ni site may be replaced with the substituting element by performing heat treatment again in order to diffuse the substituting element into the lithium-nickel composite oxide particles if necessary. In addition, after mixing the transition gold image and the starting material containing the substitution element, the lithium-containing output
It can also be produced by mixing with a raw material, firing and cooling.

Lithium compound As a lithium compound used as a starting material, L
i ₂ CO ₃ , LiNO ₃ , LiOH, LiOH.H ₂ O, L
Examples thereof include iCl, LiI, CH ₃ COOLi, Li ₂ O, Li dicarboxylic acid, Li fatty acid, and alkyl lithium. Transition metal compound Examples of the transition metal compound used as a starting material include nickel compounds, and specifically, oxides such as NiO, NiCO ₃ , Ni (NO ₃ ) ₂ , NiSO ₄ ,
Nickel salts such as nickel acetate, nickel dicarboxylate, nickel citrate, and fatty acid nickel, oxyhydroxide,
Nickel hydroxide, a halide, etc. are mentioned. -Compound of the substituting element Examples of the compound of the substituting element include oxides, hydroxides, nitrates, carbonates, dicarboxylic acid salts, fatty acid salts, ammonium salts and the like.

Mixing of starting materials These starting materials are usually mixed by a method such as wet mixing, dry mixing, ball mill grinding, coprecipitation. A step of grinding may be added before and after mixing and during mixing. -Firing For firing conditions, firing may be performed according to a conventional method.
There is no particular limitation, but the firing method for the layered lithium nickel oxide is, for example, 600 to 100 in an oxygen atmosphere.
A method of heating and baking in a temperature range of 0 ° C. can be mentioned. As disclosed in Japanese Patent Application Laid-Open No. 9-320598, the atmosphere in which carbon dioxide gas has been removed can be preferably used as the firing atmosphere.

The lithium-transition metal composite oxide is preferably pulverized to have a high specific surface area from the viewpoint of improving the rate characteristics of the battery. The present invention relates to the crushing process. Examples of the pulverization method include an air flow type pulverizer such as a jet mill and an Aujet mill, a dry media pulverizer such as a dry ball mill and a dry bead mill, and a wet media pulverizer such as a wet bead mill. The wet media pulverizer can easily perform fine pulverization, but it is not suitable because of problems such as elution of lithium ions and re-aggregation during drying. Air flow type crushers are often used for crushing battery materials, but they are not optimal because deterioration due to humidity in the gas occurs and cost increases due to the use of compressed gas. Most preferred is a dry media mill.
However, when the battery material is pulverized by the dry media mill, it is difficult to achieve fine pulverization in which the fine particles produced at an exact time reaggregate and fall below 10 μm. Further, since the lithium transition metal composite oxide that has been finely pulverized is used in a lithium secondary battery, when an inappropriate additive is used,
The battery performance suddenly dropped.

In the case of a dry type bead mill, the material of the beads used for crushing is not particularly limited, but for example, zirconia beads, alumina beads, glass beads, super steel beads, etc. can be used, but considering the mixing of impurities, zirconia is used. Beads are suitable. The size of the beads is also not particularly limited, but beads having a size of about 0.01 mm to 1 mm are used. Regarding these beads, generally used beads may be used.

In the present invention, it is preferred to grinding the specific surface area of the lithium transition metal composite oxide to the extent that a 1 m ² / g or more, more preferably 3m ² / g or more, particularly preferably 5 m ² / g or more. The reason why it is preferable to control the specific surface area to this extent is that, for example, when a battery is manufactured using a Mn-based positive electrode material for a lithium ion secondary battery, the Mn compound is eluted into the electrolytic solution at high temperature and Although deteriorated, when the Ni positive electrode is added to the Mn positive electrode in an amount of 5 to 95 wt%, the eluted Mn compound is trapped by the Ni positive electrode, and the battery performance can be improved. If the specific surface area is too small, the trapping effect of the eluted Mn compound is likely to decrease. However, since it is difficult to manufacture even if the specific surface area is too large, it is usually 100 m ² / g or less, preferably 50 m ² / g or less,
It is more preferably 30 m ² / g or less. The specific surface area in the above is a BET specific surface area.

Specifically, for example, a pulverizing condition such that a lithium transition metal composite oxide can be pulverized to 5 μm or less by using a pulverizer such as a dry ball mill and a dry bead mill, for example, a dynamic mill (MYD25-XA) type manufactured by Mitsui Mining Co., Ltd. In the case of 30 to 50 kg of 3 mmφ beads made of ZrO ₂
Fill the lithium transition metal composite oxide with a feed rate of 5 to
15 kg, and the agitator of the crusher 300 r.
p. m. Above 520r. p. m. The following may be mentioned.

In order to obtain a lithium transition metal composite oxide having a low carbonic acid concentration, it is preferable to control the atmosphere during pulverization. Specifically, crushing may be performed in an atmosphere having a dew point of -30 ° C or lower. In order to carry out the pulverization in an atmosphere having a dew point of -30 ° C or lower, that is, the lithium transition metal composite oxide may be charged in an atmosphere having a dew point of -30 ° C or lower and pulverized. The atmosphere is not particularly limited as long as the dew point is −30 ° C. or lower, but the atmosphere may be air, nitrogen, argon,
Helium may be mentioned, preferably air, nitrogen or argon. From the viewpoint of preventing the lithium nickel composite oxide from adsorbing carbon dioxide, nitrogen, argon
It is more preferable to grind in an inert gas such as.

Also during storage after crushing, it is more preferable to fill with an inert gas such as nitrogen or argon from the viewpoint of preventing the carbon dioxide gas from being adsorbed by the lithium-transition metal composite oxide. Further, in the present invention, it is preferable to pulverize the lithium-transition metal composite oxide to such an extent that the average particle diameter becomes 0.01 μm or more, and more preferably 0.05 μm.
m or more, and more preferably 0.1 μm or more. The average particle size of the lithium-transition metal composite oxide is usually 100 μm
Or less, preferably 50 μm or less, more preferably 30
μm or less. If the particle size is too large, the battery performance will decrease due to uneven coating during battery production, and if the particle size is too small, the safety will decrease.

When the lithium transition metal in the present invention is a lithium nickel composite oxide, it is preferably mixed with a lithium manganese composite oxide in order to improve the safety of the lithium battery and reduce the cost. The mixing ratio of these is usually 0.1 part by weight or more and less than 10 parts by weight, preferably 0.
It is preferably 2 parts by weight or more and less than 5 parts by weight. If the amount of the lithium manganese composite oxide mixed is too large, the battery capacity may decrease and the cycle maintenance ratio of the battery may decrease. If the amount is too small, the safety may decrease.

From the viewpoint of increasing the electrode density or improving the high temperature cycle maintenance rate, the above mixing is
A lithium transition metal composite oxide pulverized by the method of the present invention and an unpulverized lithium transition metal composite oxide can be mixed and used. In the present invention, the term "non-pulverized" includes those that have not been completely pulverized and those that have been pulverized with a slightly low degree of disintegration. Specifically, the pulverized lithium nickel composite oxide or the pulverized lithium manganese composite oxide and the unpulverized lithium nickel composite oxide or the unpulverized lithium manganese composite oxide may be mixed and used. The mixing ratio of these is usually 0.1 part by weight or more and less than 0.5 parts by weight, preferably 0.1 part by weight of crushed particles to 1 part by weight of uncrushed particles.
It is preferable to add 2 parts by weight or more and less than 0.4 parts by weight. The reason why it is preferable to control the specific surface area of the finely pulverized lithium-transition metal composite participant to this extent is that, for example, when a battery is manufactured using a Mn-based positive electrode powder for a lithium-ion secondary battery, the Mn compound becomes an electrolytic solution at high temperature. Although it elutes in the inside and the battery deteriorates, 5-95 wt% of Ni positive electrode is added to Mn positive electrode
%, The eluted Mn compound is trapped by the Ni positive electrode, and the battery performance can be improved. If the specific surface area is too small, the trapping effect of the eluted Mn compound tends to decrease. Further, by mixing the large particles and the small particles, the electrode density can be increased and the capacity per volume can be improved. When too much particles pulverized according to the present invention are added, the finely pulverized particles have a low bulk density, which may cause a decrease in electrode density, a decrease in safety, and a decrease in cycle maintenance rate. If the amount of unmilled lithium nickel composite oxide mixed is too large, the effect of improving the electrode density and the cycle maintenance rate cannot be obtained.

Typical lithium manganese oxides include spinel structure lithium manganate having a basic composition of LiMn ₂ O ₄ and layered structure lithium manganese oxide having a basic composition of LiMnO _2. In terms of ease of production and cycle characteristics, spinel type lithium manganate is preferable. The lithium-manganese composite oxide may further contain other elements in addition to lithium, manganese and oxygen. B, Al, Fe, S
Metal elements such as n, Cr, Cu, Ti, Zn, Co and Ni can be mentioned, but Al is preferable. That is, in a preferred embodiment, the lithium-manganese composite oxide is a composite oxide containing lithium, manganese and aluminum. Such other element has a function of stabilizing the crystal structure, for example, by substituting a part of the manganese site with the other element. As the substitution element for the manganese site, B,
Al, Fe, Sn, Cr, Cu, Ti, Zn, Co, N
Metal elements such as i can be mentioned. Of course, a plurality of elements can be substituted. The preferred substituting element is Al. Further, a part of oxygen atoms can be replaced with a halogen element such as fluorine.

Such another element substitution type lithium manganese composite oxide is usually used in the case of a spinel structure lithium manganese composite oxide.

[0037]

Embedded image Li _b Mn _2-a Me _a O ₄ (Me is a substituting element, 0 ≦ b ≦ 1.5, 0 <a ≦ 1). Here, the preferable substitution element Me
Is Al. However, the type and composition ratio of the substituting element are not limited to these as long as the crystal structure can be stabilized. Particularly preferred composition of lithium manganese composite oxide is

[0038]

Embedded image Li _b Mn _2-a Al _a O ₄ (0 <a ≦ 1.0, 0.9 ≦ b ≦ 1.1).
In any of the above composition formulas, the case where the amount of oxygen has a non-stoichiometric ratio is included. Furthermore, in any of the above cases, it is possible to substitute a part of the manganese atom sites with lithium by using, for example, a stoichiometric amount or more of lithium as a raw material.

The lithium-manganese composite oxide can be produced by various conventionally known methods. For example, after mixing a starting material containing lithium, manganese and a substitution element,
It can be produced by firing and cooling in the presence of oxygen. In the above-mentioned production method, a starting material containing a substitution element is not used to produce a lithium manganese composite oxide in which the Mn site is not substituted, and the lithium manganese composite oxide is an aqueous solution of a starting material containing a substitution metal element. After reacting in the molten salt or steam, the Mn site may be replaced with the replacing element by performing heat treatment again in order to diffuse the replacing element into the lithium-manganese composite oxide particles, if necessary.

Lithium compounds used as starting materials include Li ₂ CO ₃ , LiNO ₃ , LiOH and LiO.
H · H ₂ O, LiCl, LiI, CH ₃ COOLi, Li
₂ O, Li dicarboxylic acid, fatty acid Li, alkyl lithium, and the like. Examples of manganese compounds used as starting materials include manganese oxides such as Mn ₂ O ₃ and MnO ₂ , MnCO ₃ , Mn (NO ₃ ) ₂ , MnSO ₄ , manganese acetate, manganese dicarboxylate, manganese citrate, and fatty acid manganese. Examples of the manganese salt, oxyhydroxide, halide and the like. As Mn ₂ O ₃ , it is possible to use one prepared by heat-treating a compound such as MnCO ₃ or MnO ₂ .

Examples of the compound of the substituting element include oxides, hydroxides, nitrates, carbonates, dicarboxylic acid salts, fatty acid salts and ammonium salts. These starting materials are usually mixed by a method such as wet mixing, dry mixing, ball mill grinding, coprecipitation or the like. A step of grinding may be added before and after mixing and during mixing.

As a method for firing and cooling the lithium manganese oxide, for example, after calcination, main firing is performed in an oxygen atmosphere at a temperature of about 600 to 900 ° C., and then 10 ° C./min or less up to about 500 ° C. or less. Examples thereof include a method of slow cooling at a speed, a method of calcination, a main firing in a temperature of about 600 to 900 ° C. in an air or oxygen atmosphere, and a method of annealing at a temperature of about 400 ° C. in an oxygen atmosphere. The firing / cooling conditions are described in detail in JP-A-9-306490, JP-A-9-306493, JP-A-9-259880 and the like.

As a method for mixing the lithium nickel composite oxide and the lithium manganese composite oxide, for example, a method of using a powder mixer such as a V blender, a method of mixing powder in an air stream and using a bag filter to form only powder Can be used, if the amount is small, type 2 powder is put in a plastic bag and the bag is shaken, and if the amount is small, type 2 powder is mixed in an agate mortar. Further, when the positive electrode is produced by coating, it may be mixed by putting it in a slurry kneader and mixing it when producing a slurry for coating.

The lithium-transition metal composite oxide obtained in the present invention can be used as a positive electrode material of a lithium secondary battery. The positive electrode is usually formed by forming an active material layer containing the positive electrode material, a binder and a conductive agent on a current collector. In the present invention, the positive electrode active material is a lithium nickel composite oxide and a lithium manganese composite oxide. The active material layer can be usually obtained by preparing a slurry containing the above-mentioned constituents, applying this on a current collector, and drying.

The proportion of the positive electrode material of the present invention in the active material layer is
It is usually 10% by weight or more, preferably 30% by weight or more, more preferably 50% by weight or more, and usually 99.9% by weight or less, preferably 99% by weight or less. If the amount of the positive electrode material is too large, the strength of the positive electrode tends to be insufficient, and if it is too small, the capacity may be insufficient. Examples of the conductive agent used for the positive electrode include natural graphite, artificial graphite, carbon black such as acetylene black, and amorphous carbon such as needle coke. The proportion of the conductive agent in the active material layer is usually 0.01% by weight or more, preferably 0.1% by weight or more, more preferably 1% by weight or more and usually 50% by weight or less, preferably 20% by weight or less. ,
More preferably, it is 10% by weight or less. If the amount of the conductive agent is too large, the capacity may be insufficient, and if it is too small, the electrical conductivity may be insufficient.

As the binder used for the positive electrode,
Polyvinylidene fluoride, polytetrafluoroethylene,
In addition to fluoropolymers such as fluorinated polyvinylidene fluoride and fluororubber, EPDM (ethylene-propylene-diene terpolymer), SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber),
Examples thereof include polyvinyl acetate, polymethylmethacrylate, polyethylene, nitrocellulose and the like. The proportion of the binder in the active material layer is usually 0.1% by weight or more, preferably 1% by weight or more, more preferably 5% by weight or more, usually 80% by weight or less, preferably 60% by weight or less, More preferably, it is 40% by weight or less. If it is too large, the capacity may be insufficient, and if it is too small, the strength may be insufficient.

As the solvent used when preparing the slurry, an organic solvent that dissolves or disperses the binder is usually used. Examples thereof include N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methylethylketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N, N-dimethylaminopropylamine, ethylene oxide and tetrahydrofuran. In addition, a dispersant, a thickener, etc. may be added to water to form a slurry with a latex such as SBR.

The thickness of the active material layer is usually 10 to 200 μm.
It is a degree. As a material of the current collector used for the positive electrode, a metal such as aluminum, stainless steel, nickel-plated steel is used, and aluminum is preferable. The active material layer obtained by coating and drying is preferably consolidated by a roller press or the like in order to increase the packing density of the electrode material.

The lithium secondary battery of the present invention usually has the above-mentioned positive electrode, negative electrode and non-aqueous electrolyte solution. As the negative electrode material that can be used in the lithium secondary battery of the present invention, it is preferable to use a carbon material. As such a carbon material,
Natural or artificial graphite, petroleum-based coke, coal-based coke, petroleum-based pitch carbide, coal-based pitch carbide, phenolic resin / crystalline cellulose or other resin carbide and carbon material obtained by partially carbonizing them, furnace black, acetylene black , Pitch-based carbon fibers, PAN-based carbon fibers, or a mixture of two or more thereof. The negative electrode material is usually formed as an active material layer on the current collector together with the binder and, if necessary, the conductive agent. Also,
It is also possible to use lithium metal itself or a lithium alloy such as a lithium aluminum alloy as the negative electrode. Examples of the binder and conductive agent that can be used for the negative electrode include those similar to those used for the positive electrode.

The thickness of the active material layer of the negative electrode is usually 10 to 20.
It is about 0 μm. The formation of the negative electrode active material layer can be performed according to the method for forming the positive electrode active material layer. As a material for the current collector of the negative electrode, a metal such as copper, nickel, stainless steel, or nickel-plated steel is usually used, and copper is preferable. Examples of the non-aqueous electrolytic solution that can be used in the lithium secondary battery of the present invention include various electrolytic salts dissolved in a non-aqueous solvent.

As the non-aqueous solvent, for example, carbonates, ethers, ketones, sulfolane compounds, lactones, nitriles, halogenated hydrocarbons, amines, esters, amides, phosphoric acid ester compounds and the like are used. can do. To list these representative ones, propylene carbonate, ethylene carbonate,
Chloroethylene carbonate, trifluoropropylene carbonate, butylene carbonate, diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate, vinylene carbonate, tetrahydrofuran, 2
-Methyltetrahydrofuran, 1,4-dioxane, 4
-Methyl-2-pentanone, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone,
1,3-dioxolane, 4-methyl-1,3-dioxolane, diethyl ether, sulfolane, methylsulfolane, acetonitrile, propionitrile, benzonitrile, butyronitrile, valeronitrile, 1,2-dichloroethane, dimethylformamide, dimethyl sulfoxide, A single solvent such as trimethyl phosphate or triethyl phosphate or a mixed solvent of two or more kinds can be used.

Among the above non-aqueous solvents, it is preferable to use a high dielectric constant solvent in order to dissociate the electrolyte. The high dielectric constant solvent means a compound having a relative dielectric constant of 20 or more at about 25 ° C. In the high dielectric constant solvent, it is preferable that the electrolytic solution contains ethylene carbonate, propylene carbonate, and a compound in which hydrogen atoms thereof are replaced by another element such as halogen or an alkyl group. When such a high dielectric constant solvent is used, the proportion of the high dielectric constant solvent in the electrolytic solution is usually 20% by weight or more, preferably 30% by weight or more, and more preferably 40% by weight or more. If the content of the high dielectric constant solvent is small, desired battery characteristics may not be obtained.

As the electrolytic salt, any conventionally known one can be used, and LiClO ₄ , LiAsF ₆ , LiPF ₆ , Li
BF ₄ , LiB (C ₆ H ₅ ) ₄ , LiCl, LiBr, Li
_{CH 3 SO 3 Li, LiCF 3} SO 3, LiN (SO 2 C
_{F 3) 2, LiN (SO} 2 C 2 F 5) 2, LiC (SO 2 C
Examples thereof include lithium salts such as F ₃ ) ₃ and LiN (SO ₃ CF ₃ ) ₂ .

Further, gases such as CO ₂ , N ₂ O, CO, SO _{2 and the} like, polysulfide Sx ^2- , vinylene carbonate,
An additive such as catechol carbonate that forms a good film capable of efficiently charging and discharging lithium ions on the surface of the negative electrode may be present in the electrolytic solution in an arbitrary ratio. Instead of the electrolytic solution, a polymer solid electrolyte that is a conductor of an alkali metal cation such as lithium ion can also be used. It is also possible to use a semi-solid electrolyte by fluidizing the above electrolyte solution with a polymer. In the lithium secondary battery of the present invention, between the positive electrode and the negative electrode,
The electrolyte layer can be provided by various materials as described above.

A separator is usually provided between the positive electrode and the negative electrode. As the separator, a microporous polymer film is used, and as its material, nylon, polyester, cellulose acetate, nitrocellulose, polysulfone, polyacrylonitrile, polyvinylidene fluoride, tetrafluoroethylene, polypropylene, polyethylene, polybutene, etc. The polyolefin-based polymer can be mentioned. Further, a non-woven fabric filter of glass fiber or the like, or a composite non-woven fabric filter of glass fiber and polymer fiber can also be used. The chemical and electrochemical stability of the separator is an important factor, and from this point, the material is preferably a polyolefin polymer, and in particular, it is made of polyethylene from the viewpoint of the self-closing temperature which is one of the purposes of the battery separator. Preferably there is.

In the case of a polyethylene separator, ultrahigh molecular weight polyethylene is preferable from the viewpoint of shape retention at high temperature, and the lower limit of its molecular weight is preferably 500,000, more preferably 1,000,000, and most preferably 1,500,000.
On the other hand, the upper limit of the molecular weight is preferably 5,000,000, more preferably 4,000,000, and most preferably 3,000,000. This is because if the molecular weight is too large, the fluidity is so low that the pores of the separator may not close when heated.

[0057]

EXAMPLES The present invention will be described in detail with reference to the following examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. The heat was measured by the following method. First, the lithium-transition metal composite oxide that was the object to be crushed was treated as follows. A commercially available microcalorimeter Microcalorimeter MMC-5111 manufactured by Tokyo Riko Co., Ltd., which was quantified in a glass ampoule within a range of 0.1 to 1 g, and a blank glass ampoule containing no crushed material. Together, 150
The deposit was removed from the surface of the composite oxide by vacuum deaeration at 30 ° C. for 10 minutes at 10 ⁻² Torr. Into two containers provided in the above-mentioned microcalorimeter, about 25 cc of compound (additional compound at the time of crushing treatment in the present invention), which is an infinite dilution amount with respect to the crushed substance, is weighed, and the crushed substance is crushed. The vacuum deaeration-treated ampoule containing and the vacuum deaeration-treated ampoule are installed in advance in the container by attaching a device attached to the microcalorimeter that can break the ampoule from the outside. The whole was set and stabilized in a constant temperature bath at 25 ° C. for, for example, 12 hours or more. Next, the two ampoules were destroyed at the same time, and the changes in the temperature with the passage of time thereafter were measured using a thermocouple or the like to measure the amount of heat. The calorific value obtained by subtracting the calorific value of the blank ampoule from the calorific value of the ampoule containing the material to be ground was divided by the specific surface area of the material to be ground to determine the heat of immersion of the material to be ground and the additive compound during the grinding treatment.

Example 1 Attritor (MA1D) which is a batch type dry bead mill crusher
Then, 12.2 kg of zirconia beads and 1800 g of lithium nickel composite oxide (Fuji Chemical's Linirite, GRADE; CA5, specific surface area 0.77 m ² / g) were charged into an alumina tank. As the crushing conditions, a 165 mm long zirconia agitator was set in the alumina tank, and the agitator was set to 400 r.p.m. p. Grinding was carried out by stirring at m. At that time, as a grinding aid, 15 cc of ethanol was added at the start of grinding, 5 cc every 15 minutes thereafter, for a total of 30 cc. The weight of the powder that could be recovered was measured and the recovery rate was calculated. This recovery rate was used as an index of the effect of adding the auxiliary agent. As a result, the recovered powder was 1717 g (powder recovery rate: 95.4%).
Met. This powder had an average particle diameter of 0.98 μm and a specific surface area of 4.86 m ² / g. The amount of heat of ethanol and the lithium nickel composite oxide was 10 J / g, and the immersion heat divided by the specific surface area was 2.1 J / m ² .

Example 2 The same operation as in Example 1 was carried out except that acetone was used instead of ethanol as a grinding aid. The recovered powder is 1800 g (powder recovery rate: 100%),
The average particle diameter was 1.04 μm. The heat quantity of acetone and lithium nickel composite oxide is 335 J / g,
The heat of immersion divided by the specific surface area was 69 J / m ² . Example 3 In Example 1, instead of ethanol as a grinding aid, N was used.
Exactly the same operation was performed except that MP (N-methylpyrrolidone) was used. The recovered powder was 863 g (powder recovery rate: 52.1%), and the average particle size was 0.91 μm. The heat quantity of NMP and lithium nickel composite oxide is 44 J / g, and the immersion heat divided by the specific surface area is
It was 9.1 J / m ² .

Comparative Example 1 The same operation as in Example 1 was carried out except that normal hexane was used instead of ethanol as a grinding aid. 231 g of recovered powder (powder recovery rate: 16.2%)
And the average particle diameter was 1.39 μm. The calorific value of normal hexane and lithium nickel composite oxide is 2 J
/ G, the immersion heat divided by the specific surface area is 0.4 J / m
^{Was 2} . Comparative Example 2 The grinding aid was added in Example 1, but no grinding aid was added in Comparative Example 2. The same operation as in Example 1 was carried out except that the grinding aid was not added. No recovered powder could be made.

[0061]

[Table 1]

Reference Example 1 A dynamic mill (Mitsui Mining Co., Ltd. model; MYD25), a continuous dry bead mill, was charged with 33 kg of 5 mm alumina beads, and lithium nickel composite oxidation was performed at a feed rate of 13.5 kg / hr. (Fuji Chemical's Linirite, GREAT; CA5) as a grinding aid, and 60 g / Hr
Ethyl alcohol was continuously fed at a feeding rate of. The average particle diameter of the crushed lithium nickel composite oxide is 0.
The surface area was 40 μm and the specific surface area was 11.0 m ² / g.

Next, the battery evaluation results of the crushed lithium nickel composite oxide will be shown. To 75 parts by weight of this pulverized lithium nickel composite oxide, 5 parts by weight of PTFE and 20 parts by weight of acetylene black were sufficiently kneaded in an agate mortar,
A thin sheet was punched with a punch having a diameter of 9 mm. This paste is used as a positive electrode, metallic lithium foil is used as a negative electrode, and L
iPF61.8Kg was charged and crushed for 1 hour. The punched sheet weighed about 8 mg. This was pressure-bonded to an Al expanded metal to obtain a positive electrode. 1 mol / l L
A mixed solution (30% by volume: 70% by volume) of ethylene carbonate and diethylene carbonate in which iPF6 was dissolved was used as an electrolytic solution. A 0.5 mm thick Li metal foil was punched out with a 15.5 mm punch to form a negative electrode. Porous polyethylene was used as the separator. A coin type lithium battery was produced from these materials.

The battery evaluation method is described below. Current density 0.
2 mA / cm², Charging / discharging at charging / discharging voltage 4.2-3.2V
Was carried out and the initial capacity was measured. Charging voltage 201.5m
The discharge voltage was Ah / g and the discharge voltage was 176.1 mAh / g. Next
Current density of 11mA / cm ²Measure the capacity as
It was used as an index of force characteristics. It was 102.8 mAh / g.

Reference Example 2 Using a compressed air of 7.5 kgf / cm ² (dew point of 5 ° C.), a lithium nickel composite oxide (Linirite, GRADE; CA5 manufactured by Fuji Chemical Co., Ltd.) was jet-milled at a feed rate of 1 Kg / Hr. did. The crushed lithium nickel composite oxide has an average particle diameter of 4.5 μm and a specific surface area of 4.5 m.
It was ² / g. Battery evaluation was carried out in the same manner as in Example 4.

Reference Example 3 The same battery evaluation as in Example 4 was carried out, except that unmilled lithium nickel composite oxide (Fuji Chemical's linirite, GRADE; CA5) was used as the water electrode. The results are shown in Table 2. When the positive electrode material subjected to dry bead mill pulverization was used, the initial charge / discharge capacity was high, and a high battery capacity was obtained even at a high current density.

[0067]

[Table 2]

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4G048 AA04 AB02 AC06 AE05                 5H029 AJ14 AK03 AL07 AL12 AM03                       AM04 AM05 AM06 AM07 DJ16                       HJ02                 5H050 AA19 BA16 BA17 CA08 CA09                       CB08 CB12 FA17 GA05 GA27                       HA02

Claims (16)

[Claims] 1. A method for producing a lithium-transition metal composite oxide, characterized in that, when the lithium-transition metal composite oxide is pulverized, a compound having an immersion heat of 1 J / m ² or more with an object to be pulverized is present. 2. The production method according to claim 1, wherein the compound having a heat of immersion of 1 J / m ² or more with the object to be crushed is a compound having an oxygen-containing functional group. 3. A method of pulverizing a lithium transition metal composite oxide,
The manufacturing method according to claim 1 or 2, which is carried out by a dry media mill. 4. The production method according to claim 1, wherein the oxygen-containing functional group is a hydrophilic group. 5. The production method according to claim 1, wherein the oxygen-containing functional group is a carbonyl group or a hydroxyl group. 6. The amount of the compound having an oxygen-containing functional group is 0.00 based on the weight of the lithium-transition metal composite oxide.
It is 01-0.1, The manufacturing method in any one of Claims 1-5. 7. The production method according to claim 1, wherein the lithium transition metal composite oxide is a lithium cobalt composite oxide, a lithium nickel composite oxide or a lithium manganese composite oxide. 8. The lithium-transition metal composite oxide comprises B, A
l, Fe, Sn, Cr, Cu, Ti, Zn, Co, Mn
7. The method according to claim 1, which is a lithium-nickel composite oxide in which a part of nickel sites is substituted with one or more metal elements selected from the above. 9. The lithium-transition metal composite oxide has the formula: Li _x Ni _1-y M _y O _2- δ (0 <x ≦ 1.5, 0 <y ≦ 1 and M is Co. , M
n, Fe, Cr, V, Ti, Cu, Al, Ga, Bi,
Sn, Zn, Mg, Ge, Nb, Ta, Be, B, C
Represents at least one element selected from the group consisting of a, Sc and Zr. ) Is a compound represented by
6. The manufacturing method according to any one of 6. 10. A lithium-transition metal composite oxide is represented by the formula: Li _x Ni _1-yz Co _y Al _z O ₂ (0.9 ≦ x ≦ 1.1, 0 <y ≦ 1.0, 0 < z ≦ 0.
5, a compound represented by y + z ≦ 1).
The manufacturing method according to any one of 1. 11. A lithium transition metal composite oxide produced by the production method according to claim 1. 12. A positive electrode material for a lithium secondary battery, which contains the lithium-transition metal composite oxide produced by the production method according to claim 1. 13. A positive electrode material for a lithium secondary battery, comprising a mixture of the lithium transition metal composite oxide produced by the production method according to claim 1 and an unpulverized lithium transition metal composite oxide. 14. A lithium-transition metal composite oxide represented by: Li _b Mn _2-a Al _a O ₄ (0 <a ≦ 1.0, 0.9 ≦ b ≦ 1.1) The positive electrode material for lithium secondary batteries according to claim 13, which is a compound. 15. A positive electrode for a lithium secondary battery, comprising the positive electrode material for a lithium secondary battery according to claim 12 and a binder. 16. A lithium secondary battery comprising a positive electrode containing the positive electrode material for a lithium secondary battery according to claim 12, a negative electrode and an electrolyte.