JPH1186861A - Battery positive electrode active material and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positive electrode active material which can easily synthesize a substance having a uniform composition, has no restriction on the use of raw materials, can easily synthesize a substituted product, and has a small degree of deterioration due to charge / discharge cycles. . SOLUTION: LxMnyL ₂ O ₄ (wherein L is a metal element and a periodic table IIIB, IVB,
It represents one or more elements selected from non-metallic and monometallic elements of the VB and VIB groups, and x, y and z represent the following ranges. 0 <x <1.3 1.0 <y ≦ 2.0 0 ≦ z <1.4 1.8 <y + z <2.4) A lithium manganese-based composite oxide having a layered structure represented by the following formula: When the discharge capacity is 100 mAh / g or more,
It is assumed that the rate of decrease in the discharge capacity at the 30th cycle in charge and discharge at 3.5 to 4.5 V is 13% or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery positive electrode active material and a method for producing the same. More specifically, the invention of this application relates to a positive electrode active material for a lithium-based non-aqueous electrolyte secondary battery expected as a positive electrode of a secondary battery and a method for producing the same.

[0002]

2. Description of the Related Art A lithium manganese battery which can be charged and discharged and has a long-lasting voltage has been known as one of small, lightweight and high performance batteries. Many devices have been devised for a positive electrode active material for a non-aqueous electrolyte secondary battery capable of maintaining a voltage for a longer time and a method for producing the same.

[0003] As a method for producing the positive electrode active material for a non-aqueous electrolyte secondary battery, there are roughly divided into (a) a method in which solid powders such as lithium and manganese are mixed in a powder form and the mixture is fired; , A method of dissolving a solid powder of manganese or the like in a citric acid-ethylene glycol solution, drying the solution to dryness and firing, and as a special method,
(C) A method of impregnating manganese dioxide with a lithium salt is known.

However, in the above method (a), it is very difficult to synthesize a substance having a uniform composition, and the quality of the obtained battery is not high. Further, in the above method (a), since a special solution is used, there is a problem that the use of raw materials is restricted and the versatility is lacking. Furthermore, in the method (c), it is difficult to synthesize a substituted product, and there is a problem that the development of an ultra-high performance battery expected in the future is greatly restricted.

[0005] In addition to the above problems, a general problem is that the conventional lithium active material for a lithium-based nonaqueous electrolyte secondary battery has been standardized to the composition LiMn ₂ O _4. For the manganese compound itself,
There is a major problem that deterioration due to charge / discharge cycles is remarkable. This means that there are still many unclear points about the composition of lithium manganese-based compounds, their structures such as crystals, and their effects, which are closely related to the above-mentioned synthesis method.

The invention of this application has been made in view of the state of the prior art as described above, and is excellent in that the degree of deterioration due to charge / discharge cycles is small, the synthesis is easy, and there are few restrictions on the use of raw materials. It is an object of the present invention to provide a new high-performance positive electrode active material for a non-aqueous electrolyte secondary battery and a method for producing the same.

[0007]

Means for Solving the Problems The present invention solves the above-mentioned problems by solving the following formula: LixMnyLzO ₄ (where L is a metal element and a periodic table IIIB, IVB,
It represents one or more elements selected from nonmetallic and monometallic elements of the VB and VIB groups, and x, y and z represent the following ranges.

A lithium manganese-based composite oxide having a layered structure represented by the following formula: 0 <x <1.3 1.0 <y ≦ 2.0 0 ≦ z <1.4 1.8 <y + z <2.4) When the initial discharge capacity is 100 mAh / g or more,
A positive electrode active material for a battery (Claim 1) is characterized in that the rate of decrease in the discharge capacity at the 30th cycle in charge and discharge at 3.5 to 4.5 V is 13% or less.

Further, the invention of this application is based on the following formula LixMnyLzO ₄ (wherein L is a metal element and the periodic table IIIB, IVB,
It represents one or more elements selected from nonmetallic and monometallic elements of the VB and VIB groups, and x, y and z represent the following ranges.

A lithium manganese-based composite oxide having a layered structure represented by the following formula: 0 <x <1.3 1.0 <y ≦ 2.0 0 ≦ z <1.4 1.8 <y + z <2.4) Wherein a salt or an oxide of each of the lithium, manganese and L elements which is soluble in an organic acid is dissolved in an organic acid and then fired in an oxygen-containing atmosphere in an evaporation range. Claim 2) is also provided.

Further, in the present invention, as an embodiment, the metal element is selected from alkali metals, alkaline earth metals, groups II, III, IV, V and VIII of the periodic table and rare earth elements. Battery positive electrode active material (Claim 3), wherein the organic acid is a carboxylic acid (Claim 4),
It is also provided that the organic acid is acetic acid (claim 5). Further, the invention of this application is a method for producing a battery positive electrode active material as described above, which comprises dissolving an organic acid-soluble salt or oxide of each of lithium, manganese and L elements in an organic acid, and evaporating to dryness. After calcination, if necessary,
A method for producing a battery positive electrode active material, characterized by firing in an oxygen-containing atmosphere (Claim 6), and a method for producing the positive electrode active material, wherein firing is performed at a temperature of 600 ° C. or higher (Claim 7), etc. Also provide.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION As a result of investigations by the inventors, the present invention provides a high-performance positive electrode active material for a non-aqueous electrolyte secondary battery by an idea and an approach that are essentially different from the conventional techniques. That makes it possible. That is, the present invention provides an active material having the above-described specific composition and layered structure, which has an initial discharge capacity of 100 mA when used at room temperature (about 25 ° C.), for example.
h / g or more, and further 110 mAh / g or more,
The rate of decrease in the discharge capacity at the 30th cycle in charge / discharge at 3.5 to 4.5 V is specified as 13% or less, and further 5% or less.

As the chemical composition, LiMn ₂ O ₄ is considered as a reference type. In the present invention, Li, M
Various combinations of n and L elements will be considered. Examples of the metal element include Mg, Cu, T
Various elements such as i, V, Cr, Fe, Co, Ni, Zn, La, and Y, and nonmetallic and semimetallic elements include S
Things such as i, Ge, B etc. will be considered as appropriate.

In the invention of this application, most of all, in the synthesis, lithium, manganese and L
One of the major features of each element is that an organic acid-soluble salt is used as a raw material, and that the element is dissolved in an organic acid. In this case, the organic acid-soluble salt or oxide may be various inorganic salts or organic salts or oxides soluble in the organic acid. As the organic acid, carboxylic acid, and among them, acetic acid as lower aliphatic carboxylic acid is most preferable. In addition, dissolution is essentially performed using only this organic acid. Of course, other solvents that do not inhibit the action, such as water and methanol, may be used.

Since acetic acid and the like are used, the present invention can (1) use various salts as raw materials, use no special chemicals and the like, and (2) replace various metals with LiMn ₂ O ₄ The body is easily synthesized, and (3) it is characterized in that the operation is simple simply by heating and baking the solution having a uniform composition. Furthermore, (4) substances that pollute the environment are not emitted in the course of the reaction. Specifically, most of the emitted substances are carbon dioxide and water. And (5) the performance (capacity and cycle characteristics) of the synthesized material is very excellent.

In the present invention, hydroxides, carbonates, nitrates, acetates, and the like can be used as the organic acid-soluble salt as a raw material salt of lithium (Li). Organic acid-soluble salts include manganese carbonate or acetate, nitrate, and the like. For L element, organic acid-soluble salts as raw materials include oxides, hydroxides, or carbonates, nitrates, and acetates soluble in acetic acid. Can be used.

Further, in the present invention, these are converted into a solution of acetic acid or the like to form a mixed and uniform composition, and the solution obtained by evaporating the solution to dryness is heated and calcined to form a layer containing manganese as a main component. A composite oxide having a structure can be easily obtained. Regarding the treatment after evaporation to dryness, after calcination in air or another oxygen-containing atmosphere, heating in air or another oxygen-containing atmosphere at a temperature of 600 ° C. or more, more preferably at a temperature of about 650 to 775 ° C. Baking is appropriate.

[0018] Less than 600 ° C, especially less than 650 ° C, 77
At a temperature exceeding 5 ° C., it is difficult to obtain a layered structure composite oxide having excellent performance as a uniform composition. FIG. 1 shows an example of a battery using the positive electrode active material of the present invention. For example, as shown in FIG. 1, a stainless steel closed plate (1), a gasket (2), a stainless steel positive electrode A structure in which a positive electrode mixture pellet (6) using the positive electrode active material of the present invention is used together with the case (3), the lithium negative electrode (4), and the polypropylene microporous separator (5).

Hereinafter, the present invention will be described in more detail with reference to Examples. Of course, the present invention is not limited by the following examples.

[0020]

【Example】Example 1 LixMn_TwoO_FourSo that x in the general formula becomes 1.0
And Li as a starting material _TwoCO_Three0.125 mol of vinegar
The solution was added to 100 ml of the acid and dissolved by heating. 100m water
l to the solution to which Mn (CH_ThreeCOO)_Two0.5
Mole and stir it at 100-200 ° C
While evaporating to dryness. And oxidize this
Baked at 380 ° C. for 2 hours in a typical atmosphere.

The fired product is sufficiently pulverized and mixed, and fired at 725 ° C. for 24 hours in a firing furnace in an oxidizing atmosphere.
Cool down to 300 ° C at a rate of 60 ° C per hour,
Thereafter, the mixture was naturally cooled and taken out and crushed in a mortar. The obtained positive electrode active material was well matched with each profile of ASTM by X-ray diffraction, and it was confirmed that the spinel structure of LiMn ₂ O ₄ was maintained.

To 85 parts by weight of the pulverized product, 10 parts by weight of acetylene black as a conductive agent and 5 parts by weight of polytetrafluoroethylene as a binder were added and kneaded sufficiently.
Then, 20 mg of the positive electrode mixture was weighed and placed in a tablet press, and pressurized at 0.5 ton / cm ² to obtain a positive electrode. on the other hand,
Lithium metal was used for the negative electrode, and a polypropylene microporous separator and a nonwoven fabric of polypropylene were used as a separator.

As the electrolyte, propylene carbonate (P
An organic solvent obtained by mixing C) and dimethoxyethane (DME) at a volume ratio of 1: 1 was used in which lithium perchlorate was dissolved at 1 mol / liter as an electrolyte.
Thus, a battery having an outer diameter of 20.0 mm and a height of 2.5 mm as shown in FIG. 1 was produced. 0.5m of fabricated battery
Table 1 shows the cell discharge capacity up to each cut-off voltage at a discharge current density of A / cm ² and the decrease rate of the discharge capacity at the 30th cycle in charge and discharge at 3.5 to 4.5 V. In Table 1, the size of the compound of the present invention having a cubic crystal structure is shown as a lattice constant from the results obtained by X-ray diffraction.

It can be seen that the battery using the cathode active material of the present invention has very good performance, and the degree of deterioration due to charge / discharge cycles is very small. Example 2 0.1288 mol of Li ₂ CO ₃ as a starting material was added to 100 ml of acetic acid and dissolved by heating so that x in the general formula of Li x Mn ₂ O ₄ was 1.03.

Mn (C) was added to the solution to which 100 ml of water was added.
(H ₃ COO) ₂ was added in an amount of 0.5 mol.
The mixture was heated with stirring at 00 ° C to 200 ° C and evaporated to dryness. Then, at 380 ° C. in an oxidizing atmosphere.
For 2 hours. The fired product is sufficiently pulverized and mixed, fired in a firing furnace at 725 ° C. for 24 hours in an oxidizing atmosphere, cooled to 300 ° C. at a rate of 60 ° C. per hour, and then naturally cooled and taken out. And crushed.

The obtained positive electrode active material was analyzed by X-ray diffraction.
It is in good agreement with each profile of STM, and LiMn
It was confirmed that the spinel structure of ₂ O ₄ was maintained. To 85 parts by weight of the pulverized product, 10 parts by weight of acetylene black as a conductive agent and 5 parts by weight of polytetrafluoroethylene as a binder were added and kneaded sufficiently. Then, 20 mg of the positive electrode mixture is weighed and put into a tableting machine,
Pressure was applied at 0.5 ton / cm ² to obtain a positive electrode.

The same negative electrode as in Example 1 was used as the negative electrode, and a battery similar to that in Example 1 was produced. 0.5 of the fabricated battery
Table 1 shows the cell discharge capacity up to each cut-off voltage at a discharge current density of mA / cm ² and the decrease rate of the discharge capacity at the 30th cycle in charge and discharge at 3.5 to 4.5 V. It can be seen that the battery using the positive electrode active material of the present invention has very good performance and the degree of deterioration due to charge / discharge cycles is very small.

Example 3 0.125 mol of Li ₂ CO ₃ as a starting material was added to 100 ml of acetic acid to obtain Li _1.0 Mn _1.9 Cr _0.1 O _4.
And heated to dissolve. 0.475 mol of Mn (CH ₃ COO) ₂ and C
0.025 mol of r (CH ₃ COO) ₃ was added.

This was heated with stirring at 100 ° C. to 200 ° C. and evaporated to dryness. This was fired and heated at 380 ° C. for 2 hours in an oxidizing atmosphere. This is sufficiently pulverized and mixed, and is heated at 725 ° C. for 2 hours in a firing furnace in an oxidizing atmosphere.
After baking for 4 hours, the temperature was lowered at a rate of 60 ° C. per hour to 300 ° C., then cooled naturally, taken out, and ground in a mortar.

The obtained positive electrode active material was analyzed by X-ray diffraction for A
It is in good agreement with each profile of STM, and LiMn
It was confirmed that the spinel structure of ₂ O ₄ was maintained. To 85 parts by weight of the pulverized product, 10 parts by weight of acetylene black as a conductive agent and 5 parts by weight of polytetrafluoroethylene as a binder were added and kneaded sufficiently. Then, 20 mg of the positive electrode mixture is weighed and put into a tableting machine,
Pressure was applied at 0.5 ton / cm ² to obtain a positive electrode.

The same battery as in Example 1 was manufactured using the same negative electrode as in Example 1. 0.5 of the fabricated battery
Table 1 shows the cell discharge capacity up to each cut-off voltage at a discharge current density of mA / cm ² and the decrease rate of the discharge capacity at the 30th cycle in charge and discharge at 3.5 to 4.5 V. It can be seen that the battery using the positive electrode active material of the present invention has very good performance and the degree of deterioration due to charge / discharge cycles is very small.

FIG. 2 shows the results of a cycle test of the battery using the positive electrode active material of Example 3 at temperatures of 25 ° C. and 55 ° C. In this case, 1MLiPF6 EC which is an electrolyte for a secondary battery was used as an electrolyte in the battery in this case.
A mixture of (ethylene carbonate) and DMC (dimethyl carbonate) at a ratio of 1: 2 was used. That is,
This battery had an initial discharge capacity of 117 mA / g,
Even at the 0th cycle, the discharge capacity is 113 mA at 25 ° C.
/ G (decrease rate 3.4%), 100 mA / g even at 55 ° C
(Decrease rate of 14.5%), confirming high performance.

Example 4 0.125 mol of Li ₂ CO ₃ as a starting material was added to 100 ml of acetic acid so as to obtain Li _1.0 Mn _1.9 Cr _0.1 O _4.
And heated to dissolve. 0.475 mol of Mn (CH ₃ COO) ₂ and C
0.025 mol of o (CH ₃ COO) ₂ was added.

This was heated with stirring at 100 ° C. to 200 ° C. and evaporated to dryness. This was fired and heated at 380 ° C. for 2 hours in an oxidizing atmosphere. This is sufficiently pulverized and mixed, and is heated at 725 ° C. for 2 hours in a firing furnace in an oxidizing atmosphere.
After baking for 4 hours, the temperature was lowered at a rate of 60 ° C. per hour to 300 ° C., then cooled naturally, taken out, and ground in a mortar.

The obtained positive electrode active material was analyzed for A by X-ray diffraction.
It is in good agreement with each profile of STM, and LiMn
It was confirmed that the spinel structure of ₂ O ₄ was maintained. To 85 parts by weight of the pulverized product, 10 parts by weight of acetylene black as a conductive agent and 5 parts by weight of polytetrafluoroethylene as a binder were added and kneaded sufficiently. Then, 20 mg of the positive electrode mixture is weighed and put into a tableting machine,
Pressure was applied at 0.5 ton / cm ² to obtain a positive electrode.

The same battery as in Example 1 was produced by using the same negative electrode as in Example 1. 0.5 of the fabricated battery
Table 1 shows the cell discharge capacity up to each cut-off voltage at a discharge current density of mA / cm ² and the decrease rate of the discharge capacity at the 30th cycle in charge and discharge at 3.5 to 4.5 V. It can be seen that the battery using the positive electrode active material of the present invention has very good performance and the degree of deterioration due to charge / discharge cycles is very small.

EXAMPLE 5 0.125 mol of Li ₂ CO ₃ as a starting material was added to 100 ml of acetic acid so as to obtain Li _1.0 Mn _1.9 Fe _0.1 O _4.
And heated to dissolve. 0.475 mol of Mn (CH ₃ COO) ₂ and 0.025 mol of Fe (OH) ₃ immediately after synthesis were added to the solution to which 100 ml of water had been added. This was heated with stirring at 100 ° C. to 200 ° C. and evaporated to dryness. This was fired and heated at 380 ° C. for 2 hours in an oxidizing atmosphere. This is sufficiently pulverized and mixed, and fired in a firing furnace at 725 ° C. for 24 hours in an oxidizing atmosphere.
The temperature was lowered at a rate of 60 ° C. per hour to 300 ° C., then naturally cooled, taken out, and ground in a mortar.

To 85 parts by weight of the pulverized product, 10 parts by weight of acetylene black as a conductive agent and 5 parts by weight of polytetrafluoroethylene as a binder were added and kneaded sufficiently. Then, 20 mg of the positive electrode mixture was weighed, placed in a tableting machine, and pressurized at 0.5 ton / cm ² to obtain a positive electrode. As the negative electrode, the same battery as in Example 1 was used, and a battery similar to that of Example 1 was produced.

The cell discharge capacity up to each cut-off voltage at a discharge current density of 0.5 mA / cm ² of the prepared battery, and 3.5.
Table 1 shows the reduction rate of the discharge capacity at the 30th cycle in charging and discharging at -4.5 V. It can be seen that the battery using the positive electrode active material of the present invention has very good performance and the degree of deterioration due to charge / discharge cycles is very small.

Examples 6 to 8 LiMn _1.9 Mg _0.1 O ₄ , LiMn _1.9 Si _0.1 O ₄ , and Li _1.05 Mn ₂ O ₄ were each synthesized as a positive electrode active material in the same manner as in Example 1 to produce a battery. And the discharge capacity was evaluated.

The cell discharge capacity up to each cut-off voltage at a discharge current density of 0.5 mA / cm ² of the prepared battery, and 3.5.
Table 1 shows the reduction rate of the discharge capacity at the 30th cycle in charging and discharging at -4.5 V. It can be seen that the battery using the positive electrode active material of the present invention has very good performance and the degree of deterioration due to charge / discharge cycles is very small.

FIG. 3 shows the positive electrode active material (Li
_1.05 Mn ₂ O ₄ ) using a battery (using an electrolyte for a secondary battery) in the same manner as in the battery of Example 3, up to the 100th cycle. This battery has an initial discharge capacity of 120 m when tested at 25 ° C.
A / g, and the discharge capacity is 1 even at the 100th cycle.
High performance of 02 mA / g (decrease rate of 15.0%) was maintained. When the test was conducted at 55 ° C., the discharge capacity at the 100th cycle was reduced to 84 mA / g, whereas the initial discharge capacity was 117 mA / g.
Also, in the 30th cycle, a discharge capacity of about 100 mA / g was maintained in the 30th cycle, and it was confirmed that the degree of deterioration due to charge / discharge cycles was sufficiently low.

[0043]

[Table 1]

Example 9 0.125 mol of Li ₂ CO ₃ as a starting material was added to 100 ml of acetic acid so as to obtain Li _1.0 Mn _1.9 B _0.1 O ₄ and dissolved by heating. 0.475 mol of Mn (CH ₃ COO) ₂ and B ₂
0.013 mol of O ₃ was added.

This was heated with stirring at 100 ° C. to 200 ° C. and evaporated to dryness. This was fired and heated at 380 ° C. for 2 hours in an oxidizing atmosphere. This is sufficiently pulverized and mixed, and is heated at 725 ° C. for 2 hours in a firing furnace in an oxidizing atmosphere.
After baking for 4 hours, the temperature was lowered at a rate of 60 ° C. per hour to 300 ° C., then cooled naturally, taken out, and ground in a mortar.

To 85 parts by weight of the pulverized product, 10 parts by weight of acetylene black as a conductive agent and 5 parts by weight of polytetrafluoroethylene as a binder were added and kneaded sufficiently. Then, 20 mg of the positive electrode mixture was weighed, placed in a tableting machine, and pressurized at 0.5 ton / cm ² to obtain a positive electrode. As the negative electrode, the same battery as in Example 1 was used, and a battery similar to that of Example 1 was produced.

From the cell discharge capacity test of the fabricated battery up to each cut-off voltage at a discharge current density of 0.5 mA / cm ² , this battery has very good performance, and the degree of deterioration due to charge / discharge cycles is very small. It was confirmed that.

[0048]

As described in detail above, according to the invention of this application, it is easy to synthesize a substance having a uniform composition, there is no restriction on the use of raw materials, synthesis of a substituted product is easy, and the degree of deterioration due to charge / discharge cycles is reduced. Thus, it is possible to provide a positive electrode active material having a small size and excellent performance.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view illustrating the configuration of a battery using a positive electrode active material of the present invention.

FIG. 2 shows a battery using the positive electrode active material of Example 3 at 25 ° C.
FIG. 6 is a graph showing the results of a cycle test at a temperature of 55 ° C. and 55 ° C.

FIG. 3 shows a battery using the positive electrode active material of Example 8 at 25 ° C.
FIG. 6 is a graph showing the results of a cycle test at a temperature of 55 ° C. and 55 ° C.

[Explanation of symbols]

 1 Stainless steel sealing plate 2 Gasket 3 Stainless steel positive electrode case 4 Lithium negative electrode 5 Polypropylene microporous separator 6 Positive electrode material pellet

Claims (7)

[Claims] 1. The following formula: LixMnyLzO ₄ (wherein L is a metal element and a periodic table IIIB, IVB,
It represents one or more elements selected from nonmetallic and monometallic elements of the VB and VIB groups, and x, y and z represent the following ranges. 0 <x <1.3 1.0 <y ≦ 2.0 0 ≦ z <1.4 1.8 <y + z <2.4) A lithium manganese-based composite oxide having a layered structure represented by the following formula: When the discharge capacity is 100 mAh / g or more,
A positive electrode active material for a battery, wherein the rate of decrease in discharge capacity at the 30th cycle in charge and discharge at 3.5 to 4.5 V is 13% or less. 2. The following formula LixMnyLzO ₄ (wherein L is a metal element and a periodic table IIIB, IVB,
It represents one or more elements selected from nonmetallic and monometallic elements of the VB and VIB groups, and x, y and z represent the following ranges. 0 <x <1.3 1.0 <y ≦ 2.0 0 ≦ z <1.4 1.8 <y + z <2.4) A lithium manganese-based composite oxide having a layered structure represented by the following formula: A positive electrode active material for a battery, comprising: dissolving an organic acid-soluble salt or oxide of each of manganese, manganese and L elements in an organic acid, and then firing in an oxygen-containing atmosphere in an evaporation range. 3. The battery positive electrode according to claim 1, wherein the metal element is selected from alkali metals, alkaline earth metals, groups II, III, IV, V and VIII of the periodic table and rare earth elements. Active material. 4. The battery cathode active material according to claim 2, wherein the organic acid is a carboxylic acid. 5. The battery cathode active material according to claim 4, wherein the organic acid is acetic acid. 6. The method for producing a battery positive electrode active material according to any one of claims 1 to 5, wherein lithium, manganese, and an organic acid-soluble salt or oxide of each of the L elements are dissolved in an organic acid. After evaporating to dryness, calcine if necessary,
Then, the method is fired in an oxygen-containing atmosphere to produce a battery positive electrode active material. 7. The method according to claim 6, wherein the firing is performed at a temperature of 600 ° C. or higher.