JP2000313621A - Substituted lithium manganate, its production, positive pole material for organic electrolyte secondary battery and metalorganic electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic electrolyte secondary battery excellent in charge and discharge cycle characteristics at high temperatures. SOLUTION: This substituted lithium manganate represented by the formula (Li1-wZnw)8a [Mn2-xLix]16dO4-yFy (0.02<=w<=0.1; 0<=x<=0.1; 0.01<=y<=0.2) in which a lithium site is substituted with zinc and an oxygen site is substituted with fluorine in a lithium manganese compound oxide forming a spinel type crystal structure is used as a positive pole material for an organic electrolyte secondary battery. The substituted lithium manganate can be produced by passing a compound selected from, e.g. an aluminum compound, a cobalt compound and a nickel compound, dimanganese trioxide obtained by heat-treating a manganese oxide at 550-750 deg.C, a lithium compound, a zinc compound and a fluorine compound through a process for mixing thereof, then heat-treating the resultant mixture in an air atmosphere at 600-900 deg.C and subsequently annealing the heat- treated mixture to at least 300 deg.C at <=10 deg.C/min temperature decreasing rate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a substituted lithium manganate for an organic electrolyte secondary battery, a method for producing the same, a positive electrode material for an organic electrolyte secondary battery, and a metal organic electrolyte secondary battery.

[0002]

2. Description of the Related Art A lithium secondary battery using a non-aqueous electrolyte containing a lithium salt is known. One of the typical ones uses LiMn ₂ O ₄ as a positive electrode active material and uses lithium, a lithium alloy, or a substance that absorbs and releases lithium as a negative electrode active material.

[0003] JP-A-4-169076 discloses LiMn.
It has been proposed that a manganese-based composite oxide represented by _2-x Me _x O ₄ (Me: at least one of Co, Cr, Ni, Ta, and Zn) be used as a positive electrode active material. However, in this publication, although the claims state at least one kind, the detailed description and Examples do not disclose lithium manganate substituted with two or more kinds of metals. A secondary battery using a substituted lithium manganate substituted only with Cr as a positive electrode active material has remarkably improved cycle characteristics at high temperatures, but may generate hexavalent chromium during battery treatment. , Not industrial. In addition, other metal systems (Co,
Ni, Ta, and Zn) do not sufficiently improve the cycle characteristics at high temperatures. The cycle characteristics indicate the degree of decrease in capacity when the battery is used repeatedly.A good cycle characteristic means that the capacity does not decrease even after repeated use and the initial capacity is maintained for a long time. It is.

Japanese Patent Application Laid-Open No. Hei 10-199532 discloses that a lithium site of a lithium-manganese composite oxide having a spinel-type crystal structure is partially replaced with one or more selected from zinc, gallium and indium. By substituting with a metal element, the spinel crystal structure is stabilized. However, the high temperature characteristics of a battery are insufficient.

Japanese Patent Laid-Open Publication No. Hei 10-177860 discloses that Li _{1 + x} Mn _2-x O _4-y F _z (where x
Is 0.0133 ≦ x ≦ 0.333, y is 0 <y ≦ 0.2,
It is proposed that z be 0.01 ≦ z ≦ 0.2 and z ≦ y) as the positive electrode active material. However, a secondary battery using a substituted lithium manganate substituted only with F as a positive electrode active material still has insufficient high-temperature characteristics.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a substituted lithium manganate having a spinel structure having excellent cycle characteristics at a high temperature, a method for producing the same, and an organic electrolysis using the substituted lithium manganate as a positive electrode active material. An object of the present invention is to provide a positive electrode material for a liquid secondary battery and an organic electrolyte secondary battery.

[0007]

Means for Solving the Problems The present inventors have a composition formula:
(Li _1-w Zn _w ) _8a [Mn _2-x Li _x ] _16d O _4-y F _y (0.02 ≦ w
≤ 0.1, 0 ≤ x ≤ 0.1, 0.01 ≤ y ≤ 0.2), the organic electrolyte secondary battery using the substituted lithium manganate as a positive electrode active material is cycled at high temperatures. They have found that the characteristics are excellent, and have completed the present invention.

The present invention is described below. (1) Composition formula (Li _1-w Zn _w ) _8a [Mn _2-x Li _x ] _16d O _4-y F
_y (0.02 ≦ w ≦ 0.1, 0 ≦ x ≦ 0.1, 0.01
≦ y ≦ 0.2) substituted lithium manganate. (2) Dimanganese trioxide, a lithium compound, a zinc compound and a fluorine compound obtained by heat-treating manganese oxide at 550 to 750 ° C. are mixed, and then heat-treated in an air atmosphere at 600 to 900 ° C .; 2. The substituted lithium manganate according to the above item 1, which is produced through a process of gradually cooling to 300 ° C. at a temperature lowering rate of not more than ° C./min.

(3) The substituted lithium manganate according to (2), wherein the temperature is lowered at a rate of 1 ° C./min or less in the step of gradually cooling after the heat treatment in (2). (4) Mixing dimanganese trioxide, a lithium compound, a zinc compound and a fluorine compound obtained by heat-treating manganese oxide at 550 to 750 ° C, heat-treating in an air atmosphere at 600 to 900 ° C, and then 10 2. The method for producing a substituted lithium manganate according to the above item 1, wherein the method comprises a step of gradually cooling to 300 ° C. at a temperature lowering rate of not more than 300 ° C./min.

(5) The method for producing a substituted lithium manganate according to the above (4), wherein the rate of temperature decrease in the step of slow cooling after the heat treatment in the production method of the above (4) is 1 ° C./min or less. (6) An organic electrolyte secondary battery using lithium, a lithium alloy or a carbon material capable of occluding and releasing lithium ions as a negative electrode active material and a mixed solution of an organic solvent and a lithium salt electrolyte as an electrolyte. 4. A positive electrode material for an organic electrolyte secondary battery, comprising the substituted lithium manganate according to any one of the above items 1 to 3 as a positive electrode active material. (7) An organic electrolyte secondary battery comprising the positive electrode material for an organic electrolyte secondary battery according to the above (6).

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail. The substituted lithium manganate of the present invention comprises (Li _1-w Z
n _w ) _8a [Mn _2-x Li _x ] _16d O _4-y F _y (0.02 ≦ w ≦ 0.
1, 0 ≦ x ≦ 0.1, 0.01 ≦ y ≦ 0.2), a dimanganese trioxide, lithium compound obtained by heat-treating a manganese oxide at 550 to 750 ° C. , After mixing a zinc compound and a fluorine compound,
After heat treatment in an air atmosphere of 900 ° C, then 10 ° C /
It is manufactured through a process of gradually cooling to a temperature of 300 ° C. or less at a temperature lowering rate of less than one minute.

In the substituted lithium manganate of the present invention, the lithium site of lithium manganate (LiMn ₂ O ₄ ) is Zn-substituted. Therefore, the substituted lithium manganate is replaced with an organic electrolyte solution of an organic electrolyte secondary battery. When used as a positive electrode material for a secondary battery, the high temperature characteristics of the resulting secondary battery are improved.

Further, when the oxygen site of LiMn ₂ O ₄ is substituted with F, it is possible to improve the high temperature characteristics and increase the capacity of a secondary battery using the obtained substituted lithium manganate. In the present invention, the use of the Zn-F composite substituted lithium manganate can provide a secondary battery having significantly improved high-temperature characteristics as compared to Zn alone.

In the method for producing a substituted lithium manganate of the present invention, the lithium compound used includes nitrates, acetates, hydroxides, oxides and the like. Specifically, the lithium compound used includes lithium carbonate, lithium hydroxide, lithium nitrate, lithium acetate and the like. The manganese oxide includes electrolytic manganese dioxide (EMD) and chemically synthesized manganese dioxide (C
MD), manganese carbonate, manganese nitrate, and manganese acetate.

The mixing of dimanganese trioxide, a lithium compound, a zinc compound and a fluorine compound in the method for producing a substituted lithium manganate of the present invention may be carried out by a conventional method.
Examples thereof include a wet method in which mixing is performed by a dry method or a liquid medium in which a uniform mixture is easily provided.

(Li _1-w Zn _w ) _8a [Mn _2-x Li _x ] _16d O _4-y F
_y (0.02 ≦ w ≦ 0.1, 0 ≦ x ≦ 0.1, 0.01
≦ y ≦ 0.2) requires oxygen. However, the heating atmosphere may be an air atmosphere, as long as air is sufficiently supplied. When the supply amount of air is less than the reaction theoretical amount, a large oxygen deficiency can be produced.

In the method for producing substituted lithium manganate of the present invention, the heat treatment temperature after mixing dimanganese trioxide, lithium compound, zinc compound and fluorine compound is 60.
The temperature is 0 to 900 ° C, preferably 700 to 850 ° C. If the heat treatment temperature is lower than 600 ° C., unreacted dimanganese trioxide remains, and the secondary battery using the obtained substituted lithium manganate has low initial capacity and cycle characteristics. On the other hand, when the heat treatment temperature is higher than 900 ° C., a deoxygenation reaction occurs from the generated spinel, and the initial capacity and cycle characteristics are reduced.

In the method for producing a substituted lithium manganate of the present invention, the rate of temperature decrease during the slow cooling step is at least 3
The temperature is lowered to 00 ° C at a rate of 10 ° C / min or less, preferably 1.0 ° C / min or less.

[0019]

The present invention will be described more specifically with reference to the following examples and comparative examples.

Example 1 BET specific surface area 49.0 (m ² /
g), pore volume 0.086 (ml / g), pore diameter 20 to
EMD having an 80 nm pore volume of 0.0262 (ml / g) was heat-treated at 600 ° C. for 3 hours in an air atmosphere to induce Mn ₂ O ₃ .

The BET specific surface area of EMD was determined by a nitrogen adsorption method. The pore volume was calculated by the BJH (Barrett, Joyner, Hallender) method by the nitrogen adsorption / desorption method. The volume of pores having a pore diameter of 20 to 80 nm was calculated by the BJH method by the nitrogen adsorption / desorption method. In addition, as a device, Coulter (COULTER ^TM SA3100
plus).

The Mn ₂ O ₃ , lithium carbonate, zinc oxide and lithium fluoride have an atomic ratio of manganese, lithium, zinc and fluorine of 1.954: 0.997: 0.04.
9: 0.049. After weighing, they were mixed well by a ball mill. The resulting mixture is placed in an electric furnace at 7
After heating in air atmosphere at 70 ° C. for 10 hours, 300
After cooling down to 1.0 ° C / min at 1.0 ° C / min,
_{(Li 0.951 Zn 0.049) [Mn} 1. 954 Li 0.046] were produced substituted lithium manganese oxide represented by O _3.951 F _0.049 composition formula.

Production of battery: (Li _0.951 Zn _0.049 ) [Mn
_1.954 Li _0.046 ] O _3.951 F _0.049 20 mg and binder (Teflon: acetylene black = 1: 2) 12 mg
Weigh and crush well with mortar, SUS304 100Mesh
After being spread on a φ16 mm current collector, a positive electrode was prepared by press molding at a pressure of ² ton / cm ² . In a coin-shaped cell, a separator made of a polypropylene film was sandwiched, the above positive electrode was placed on one side, and a Li foil (negative electrode) was placed on the other side, and a non-aqueous electrolyte was added thereto, and the case was sealed. As the non-aqueous electrolyte, a solution obtained by dissolving LiPF ₆ at a concentration of 1 mol / l in a 1: 2 (volume ratio) mixture of ethylene carbonate and dimethyl carbonate was used.

Initial discharge capacity and charge / discharge cycle characteristics;
The initial discharge capacity and charge / discharge cycle characteristics of the battery prepared above were measured at a high temperature (60 ° C.). The charge / discharge cycle test was performed by charging the battery with a constant current and a constant voltage of 0.8 mA in a range of 3.0 V to 4.2 V (charging at a constant voltage from 4.2 V). Is the capacity. The results are shown in Table 1.

<Example 2> BET specific surface area 49.0 (m ² /
g), pore volume 0.086 (ml / g), pore diameter 20 to
EMD having an 80 nm pore volume of 0.0262 (ml / g) was heat-treated at 600 ° C. for 3 hours in an air atmosphere to induce Mn ₂ O ₃ . The atomic ratio of Mn ₂ O ₃ , lithium carbonate, zinc oxide and lithium fluoride to manganese, lithium, zinc and fluorine is 1.954: 0.997:
It weighed so that it might be set to 0.049: 0.025. After weighing, they were mixed well by a ball mill. The obtained mixture was heated in an electric furnace at 770 ° C. for 10 hours in an air atmosphere, then dropped to 300 ° C. at 1.0 ° C./min, and allowed to cool naturally to obtain (Li _0.951 Zn _0.049 ) [Mn _1.954 Li _0.046 ] O _3.975
A substituted lithium manganate represented by a composition formula of F _0.025 was produced. The _{(Li 0.951 Zn 0.04 9) [} Mn 1.954 Li 0.046] O 3.975 F
_{Using 0.025} , a battery was prepared in accordance with Example 1, and 6
The charge / discharge measurement was performed at 0 ° C. The results are shown in Table 1.

Comparative Example 1 BET specific surface area 49.0 (m ² /
g), pore volume 0.086 (ml / g), pore diameter 20 to
EMD having an 80 nm pore volume of 0.0262 (ml / g) was heat-treated at 600 ° C. for 3 hours in an air atmosphere to induce Mn ₂ O ₃ . The Mn ₂ O ₃ , lithium carbonate and zinc oxide were weighed so that the atomic ratio of manganese, lithium and zinc was 1.954: 0.997: 0.049. After weighing, they were mixed well by a ball mill. The resulting mixture in an electric furnace, 10 hours at 770 ° C., was heated in an air atmosphere, and spontaneous cooling after being lowered at 1.0 ° C. / min up to 300 ℃, (Li _{0 .951} Zn _0.049 ) [Mn _1.954 Li
_0.046 ] O _{4 The} substituted lithium manganate represented by the composition formula was produced. Using (Li _0.951 Zn _0.049 ) [Mn _1.954 Li _0.046 ] O ₄ , a battery was fabricated according to Example 1, and charge / discharge measurement was performed at 60 ° C. The results are shown in Table 1.

Comparative Example 2 BET specific surface area 49.0 (m ² /
g), pore volume 0.086 (ml / g), pore diameter 20 to
EMD having an 80 nm pore volume of 0.0262 (ml / g) was heat-treated at 600 ° C. for 3 hours in an air atmosphere to induce Mn ₂ O ₃ . The Mn ₂ O ₃ , lithium carbonate and lithium fluoride were weighed such that the atomic ratio with manganese, lithium and fluorine was 1.923: 1.076: 0.096. After weighing, they were mixed well by a ball mill.
The resulting mixture was heated in an electric furnace at 770 ° C. for 10 hours in an air atmosphere, and then to 300 ° C. at 1.0 ° C./mi.
n, let it cool naturally, and let it cool down (Li) [Mn _1.923 L
i _0.076] were produced substituted lithium manganese oxide represented by a composition formula of O _3.904 F _0.096. The (Li) [Mn _1.923 Li _0.076 ] O
_A battery was prepared using _3.904 F _0.096 in accordance with Example 1, and charge / discharge measurement was performed at 60 ° C. The results are shown in Table 1.

[0028]

[Table 1]

[0029] According to Table 1, ZZ is higher than that of Zn and F alone.
It can be seen that the cycle characteristics were improved in the Zn-F system combined with n.

The organic electrolyte secondary battery using the substituted lithium manganate of the composition formula according to the present invention as a cathode material for an organic electrolyte secondary battery has excellent charge / discharge cycle characteristics at high temperatures.

Continued on the front page F-term (reference) 4G048 AA04 AA06 AB01 AB05 AC06 AE05 AE06 5H003 AA04 BA01 BB05 BC01 BC06 BD01 5H014 AA01 BB01 BB06 EE10 HH00 HH08 5H029 AJ05 AK03 AL06 AM03 AM04 AM05 AM07 CJ02 CJJ CJ02 CJ08

Claims (7)

[Claims] 1. Composition formula (Li _1-w Zn _w ) _8a [Mn _2-x Li _x ] _16d O
_4-y F _y (0.02 ≦ w ≦ 0.1, 0 ≦ x ≦ 0.1, 0.
01 ≦ y ≦ 0.2) substituted lithium manganate. 2. Dimanganese trioxide, a lithium compound, obtained by heat-treating a manganese oxide at 550 to 750 ° C.
After mixing the zinc compound and the fluorine compound, 600 to 90
2. The substituted lithium manganate according to claim 1, wherein the substituted lithium manganate is produced through a process of performing a heat treatment in an air atmosphere at 0 ° C., and then gradually cooling to 300 ° C. at a temperature lowering rate of 10 ° C./min or less. 3. The substituted lithium manganate according to claim 2, wherein the temperature is lowered at a rate of 1 ° C./min or less in the step of gradually cooling after the heat treatment. 4. Manganese oxide, manganese trioxide obtained by heat treatment at 550 to 750 ° C., a lithium compound,
After mixing the zinc compound and the fluorine compound, 600 to 90
The method for producing a substituted lithium manganate according to claim 1, wherein a heat treatment is carried out in an air atmosphere at 0 ° C, and then the temperature is gradually lowered to 300 ° C at a temperature lowering rate of 10 ° C / min or less. 5. The method for producing a substituted lithium manganate according to claim 4, wherein the temperature decreasing rate in the step of gradually cooling after the heat treatment in the production method according to claim 4 is 1 ° C./min or less. 6. A negative electrode active material comprising a carbon material capable of occluding and releasing lithium, a lithium alloy or lithium ions,
4. A substituted lithium manganate according to any one of claims 1 to 3, as a positive electrode active material for an organic electrolyte secondary battery using a mixed solution of an organic solvent and a lithium salt electrolyte as an electrolyte. A positive electrode material for an organic electrolyte secondary battery containing: 7. An organic electrolyte secondary battery comprising the positive electrode material for an organic electrolyte secondary battery according to claim 6.