JPH117957A - Manufacture of positive electrode material for lithium secondary battery, and battery using the material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inactivate the unreacted lithium, which exists in a surface of the Li-Mn compound oxide, and improve the cycle characteristic at high temperatures by burning the mixture of lithium salt and manganese oxide in the atmosphere at a specified temperature, and making the CO2 gas flow into a burning furnace in a temperature lowering process. SOLUTION: Manganese oxide and lithium salt are mixed in a ratio of Li:Mn = about 0.5:1.0, and the mixture is burned at 600-900 deg.C in the atmospheric air for about 20 hours. CO2 gas is made to flow into a burning furnace in a temperature lowering process. After the cooling, the mixture is pulverized so as to generate the Li-Mn compound oxide. Acetylene black and fluororesin binder are mixed in this Li-Mn compound oxide, and pressed for foaming so as to obtain a pellet, and this pellet is used as a positive electrode mix. As a negative electrode material, metal lithium is used. Effect of the Li-Mn compound oxide becomes larger in the condition that Li/Mn>0.5, as the quantity of Li is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a Li-Mn composite oxide as a positive electrode material used for a non-aqueous electrolyte secondary battery, represented by a lithium secondary battery, and a battery using the same. Things.

[0002]

2. Description of the Related Art In recent years, portable and cordless electronic devices such as AV devices and personal computers have been rapidly developed, and there is a high demand for small, lightweight, and high energy density secondary batteries as power sources for driving these devices. . In response to such demands, non-aqueous secondary batteries, especially lithium secondary batteries,
In particular, expectations are high for batteries having high voltage and high energy density. LiCo capable of intercalating and de-intercalating lithium as a cathode material for lithium secondary batteries meeting these requirements
Research and development of layered compounds such as O2, LiNiO2 or composite oxides in which a transition metal element is partially substituted for these oxides have been actively conducted.

[0003] Further, although having no layered structure, LiCoO
As an inexpensive material having a high voltage of 4V class similar to 2 and the like, LiMn2O4, which is a Li-Mn composite oxide, and LiMnO2 having a slightly lower voltage of about 3V are also being developed. However, when these Li—Mn composite oxides are used as a positive electrode material for a lithium secondary battery, the conventional Li
There has been a problem that the cycle characteristics are inferior to the case where CoO2 or LiNiO2 is used as the cathode material. As a countermeasure, a method of replacing a part of Mn with Li or replacing it with Al has been tried, but some improvement is obtained but not enough. There is also a problem that the battery capacity is small.

[0004]

SUMMARY OF THE INVENTION The present invention relates to Li-Mn
An object of the present invention is to provide a method for producing a positive electrode material for a lithium secondary battery having excellent cycle characteristics at a high temperature by inactivating unreacted lithium existing on the surface of a composite oxide, and a battery using the same.

[0005]

Accordingly, the present invention provides a method of mixing a lithium salt and a manganese oxide, which is carried out at 600 ° C. to 9 ° C. in the atmosphere.
A method for producing a positive electrode material for a lithium secondary battery by firing at 00 ° C., wherein CO2 gas is passed through a firing furnace during a temperature lowering process after firing. . Further, the present invention is a battery using the positive electrode material for a lithium secondary battery obtained above. In particular, in the present invention, the Li-Mn composite oxide has Li / Mn> 0.1.
The effect increases as the amount of 5 and Li increases.

[0006]

The present invention will be specifically described below based on examples and comparative examples. Note that the present invention is not limited to the following raw materials, battery configurations, and the like.

Example 1 Dimanganese trioxide and lithium carbonate were prepared using Li: Mn = 0.
5: 1.0 and mixed with a ball mill.
After firing at 800 ° C. for 20 hours in an air atmosphere in an electric furnace, CO 2 gas was passed through the electric furnace in the course of cooling. After cooling, the mixture was crushed to produce a Li-Mn composite oxide. The Li-Mn composite oxide was left in the air to obtain a water content (L
The amount of water adsorbed on the surface of the i-Mn composite oxide or the like was measured, and the results are shown in FIG. Further, a coin battery was manufactured using this Li-Mn composite oxide as a positive electrode material, and the cycle characteristics at high temperatures were measured. The results are shown in Table 1.
As a positive electrode mixture of a coin battery, acetylene black 10
A mixture obtained by mixing at a ratio of 5 parts by weight of the fluororesin binder and 5 parts by weight of the fluororesin-based binder was subjected to pressure molding under a load of 3 t to form a pellet. As an electrolytic solution, lithium tetrafluoroborate (Li) was adjusted to 1 mol / l in a 1: 1 mixed solvent of propylene carbonate and 1,2-dimethoxyethane.
BF4) was used as dissolved in a separator. Metallic lithium was used as the negative electrode material.

[0008]

[Table 1]

Example 2 Dimanganese trioxide and lithium carbonate were prepared using Li: Mn = 0.
After mixing at a ratio of 55: 1.0, the mixture was mixed in a ball mill, and calcined in an electric furnace at 800 ° C. for 20 hours in an air atmosphere. Then, CO2 gas was passed through the electric furnace in the course of cooling.
Subsequently, the resultant was crushed to produce a Li-Mn composite oxide. The Li-Mn composite oxide was left in the air to measure the water content, and the results are shown in FIG. In addition, this Li-M
A coin battery was produced in the same manner as in Example 1 using the n composite oxide as the positive electrode material, and the cycle characteristics at high temperatures were measured. The results are shown in Table 1.

Comparative Example 1 Dimanganese trioxide and lithium carbonate were prepared by mixing Li: Mn = 0.
The mixture was mixed at 50: 1.0, mixed by a ball mill, fired in an electric furnace at 800 ° C. in the air atmosphere for 20 hours, and then cooled. Subsequently, the resultant was crushed to produce a Li-Mn composite oxide. The Li-Mn composite oxide was left in the air to measure the water content, and the results are shown in FIG. Further, a coin battery was manufactured in the same manner as in Example 1 using this Li-Mn composite oxide as a positive electrode material, and the cycle characteristics at high temperatures were measured. The results are shown in Table 1.

Comparative Example 2 Dimanganese trioxide and lithium carbonate were prepared by mixing Li: Mn = 0.
The mixture was mixed at a ratio of 55: 1.0, mixed in a ball mill, fired in an electric furnace at 800 ° C. in the air atmosphere for 20 hours, and then cooled. Subsequently, the resultant was crushed to produce a Li-Mn composite oxide. The Li-Mn composite oxide was left in the air to measure the water content, and the results are shown in FIG. Further, a coin battery was manufactured in the same manner as in Example 1 using this Li-Mn composite oxide as a positive electrode material, and the cycle characteristics at high temperatures were measured. The results are shown in Table 1.

[0012]

As described above, according to the present invention,
It is possible to provide a method for producing a positive electrode material for a lithium secondary battery having excellent cycle characteristics at a high temperature by inactivating unreacted lithium existing on the surface of a Li-Mn composite oxide, and a battery using the same. .

[Brief description of the drawings]

FIG. 1 is a graph showing a change in water content of a Li—Mn composite oxide in the atmosphere.

Claims (2)

[Claims] 1. A method of mixing a lithium salt and a manganese oxide,
A method for producing a positive electrode material for a lithium secondary battery by firing at 600 ° C. to 900 ° C. in the air, characterized in that a CO 2 gas is passed through a firing furnace during a cooling process after firing. Manufacturing method. 2. A battery using the positive electrode material for a lithium secondary battery obtained in claim 1.