JP2001307724A - Spinel type positive electrode material for lithium secondary battery and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spinel type positive electrode material for a lithium secondary battery that is superior in high capacity and high-temperature characteristics. SOLUTION: This spinel type positive electrode material for a lithium secondary battery has Li-Mn-Al-O-F as a constituent element, and further contains M (one or more elements selected from among Cr, Fe, Co, Ni, Cu and Mg) as a constituent element, and has BBT specific surface less than 1.5 m2/g. The manufacturing method for the spinel type positive electrode material is to add a compound of element M to a mixture of a lithium compound, manganese compound and aluminum compound, and mix them to bake. AlF3 is used at least as a part of aluminum compound.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spinel-type positive electrode material for a lithium secondary battery and a method for producing the same, and more particularly to a spinel-type positive electrode material for a lithium secondary battery and a method for producing the same, which can provide high capacity charge / discharge characteristics.

[0002]

2. Description of the Related Art In recent years, portable personal computers and telephones have become portable.
With the rapid progress of cordless technology, the demand for secondary batteries as power sources for driving them is increasing. Among them, non-aqueous electrolyte secondary batteries are particularly expected because of their small size and high energy density. As the positive electrode material of the nonaqueous electrolyte secondary battery, there are lithium cobaltate (LiCoO2), lithium nickelate (LiNiO2), lithium manganate (LiMn2O4) and the like. Since these positive electrode materials have a voltage of 4 V or more with respect to lithium, the battery has a high energy density.

However, when a lithium secondary battery is manufactured using these cathode materials, LiCoO 2, LiCoO 2
NiO2 has a theoretical capacity of about 280 mAh / g. In contrast, the theoretical capacity of LiMn2 O4 is 148 mAh / g.
However, it is considered to be suitable for EV applications because of its abundance of inexpensive manganese oxide as a raw material and lack of thermal instability during charging as in LiNiO2. However, the conventionally proposed LiMn2 O4
All were far from the theoretical capacity.

[0004]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a positive electrode material for a lithium secondary battery and a method for producing the same, which can provide high capacity charge / discharge characteristics.

[0005]

SUMMARY OF THE INVENTION Accordingly, the present invention provides
A spinel-type positive electrode material for a lithium secondary battery, characterized by comprising -Mn-Al-OF as a constituent element. Further, M (M is Cr, Fe, Co, Ni, Cu, M
g) (at least one element selected from g) as a constituent element. The spinel-type positive electrode material for a lithium secondary battery described above, which has a BET specific surface area of 1.5 m 2 / g or less. Also lithium compounds,
A method for producing a spinel-type cathode material for a lithium secondary battery by mixing and firing a manganese compound and an aluminum compound, wherein at least a part of the aluminum compound contains Al.
A method for producing a spinel-type positive electrode material for a lithium secondary battery, characterized by using F3. Further, a compound of M element (M is at least one or more elements selected from Cr, Fe, Co, Ni, Cu, Mg) is added to the lithium compound, manganese compound, and aluminum compound and mixed.
A method for producing a spinel-type positive electrode material for a lithium secondary battery as described above, characterized by firing.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The spinel-type positive electrode material for a lithium secondary battery of the present invention is obtained by mixing and firing a manganese raw material, a compound containing an element to be replaced with a lithium raw material, an aluminum raw material, and at least a part of the aluminum raw material, and mixing and firing them. Can be Lithium carbonate (Li2
CO3), lithium nitrate (Li2NO3), lithium hydroxide (LiOH) and the like. In addition, as a manganese raw material and a raw material of an element which substitutes for them, an oxide or a hydroxide of each element and AlF3 for at least a part of the aluminum compound are used.

[0007] In order to obtain a larger reaction area, these raw materials are preferably ground before or after mixing the raw materials. The weighed and mixed raw materials may be used as they are or may be granulated and used. The granulation method may be wet or dry.

[0008] These raw materials are put into a firing furnace, and 700
By firing at a lower temperature range than the normal firing temperature of about ° C., the spinel-type positive electrode material for a lithium secondary battery of the present invention can be obtained. Examples of the firing furnace used here include a rotary kiln and a stationary furnace. The firing time is 1 hour or more, preferably 5 to 20 hours, to obtain a uniform reaction.

Here, with respect to the lithium secondary battery, the positive electrode material, a conductive material such as carbon black, and a binder such as Teflon (polytetrafluoroethylene) binder are mixed to form a positive electrode mixture, For the negative electrode, a material capable of desorbing and occluding lithium such as lithium alloy or carbon is used. As the non-aqueous electrolyte, a lithium salt such as lithium hexafluorophosphate (LiPF6) is used such as ethylene carbonate-dimethyl carbonate. Those dissolved in a mixed solvent or those obtained by converting them into a gel electrolyte are used.

[0010]

EXAMPLES Hereinafter, the present invention will be specifically described based on examples and comparative examples, but the present invention is not particularly limited thereto. [Example 1] 21.21 g of lithium carbonate, 92.18 g of manganese dioxide, 8.28 g of aluminum hydroxide,
0.79 g of aluminum fluoride (AlF3) was weighed, mixed with a ball mill, and fired at 750 ° C for 20 hours. It was confirmed by X-ray diffraction that the obtained spinel-type positive electrode material had a crystal structure unique to spinel-type. The BET specific surface area was 1.2 m2 / g.

Further, the spinel-type positive electrode material obtained above was mixed with acetylene black and Teflon binder to prepare a positive electrode mixture. 40 mg of this positive electrode mixture was weighed and formed into a disk having a diameter of 12 mm,
After drying at ° C, a model cell of a lithium secondary battery was prepared using a metal lithium counter electrode. After charging this to 4.3V,
When the discharge capacity (initial capacity) up to 3.0 V was measured, it was found that the capacity was as high as 118 mAh / g.

Further, 2 g of the spinel-type positive electrode material obtained above was mixed with 1 mol / l of lithium hexafluorophosphate (LiP
F6) and 5 ml of a one-to-one mixed electrolyte of ethylene carbonate (EC) -dimethyl carbonate (DMC) and left at 80 ° C. for 20 days. Thereafter, the well was thoroughly washed with DMC, dried, and the discharge capacity was measured in the same manner as above. The ratio of the discharge capacity before and after storage was shown in Table 1 as a discharge capacity retention ratio.

[0013]

【table 1】

Example 2 21.21 g of lithium carbonate,
92.18 g of manganese dioxide, 8.28 g of aluminum hydroxide, and 0.7 of aluminum fluoride (AlF3)
9 g each was weighed and mixed with a ball mill.
Baking was performed at 0 ° C. for 20 hours. It was confirmed by X-ray diffraction that the obtained spinel-type positive electrode material had a crystal structure unique to spinel-type. The BET specific surface area was 1.1 m2 / g. Further, the battery characteristics were evaluated in the same manner as in Example 1, and the obtained results are shown in Table 1.

Example 3 21.45 g of lithium carbonate,
96.28 g of manganese dioxide and 0.
45 g, 4.37 g of aluminum hydroxide, and 0.31 g of aluminum fluoride (AlF3) were weighed,
After mixing with a ball mill, the mixture was fired at 700 ° C. for 20 hours. It was confirmed by X-ray diffraction that the obtained spinel-type positive electrode material had a crystal structure unique to spinel-type. Also, B
The ET specific surface area was 1.4 m2 / g. Example 1
The battery characteristics were evaluated in the same manner as described above, and the obtained results are shown in Table 1.

Example 4 21.45 g of lithium carbonate,
96.28 g of manganese dioxide and 0.
45 g, 4.33 g of aluminum hydroxide, and 0.39 g of aluminum fluoride (AlF3) were weighed,
After mixing with a ball mill, the mixture was fired at 700 ° C. for 20 hours. It was confirmed by X-ray diffraction that the obtained spinel-type positive electrode material had a crystal structure unique to spinel-type. Also, B
The ET specific surface area was 1.3 m2 / g. Example 1
The battery characteristics were evaluated in the same manner as described above, and the obtained results are shown in Table 1.

Example 5 21.66 g of lithium carbonate,
96.28 g of manganese dioxide and 0.
45 g, 4.21 g of aluminum hydroxide, and 0.63 g of aluminum fluoride (AlF3) were weighed,
After mixing with a ball mill, the mixture was fired at 700 ° C. for 20 hours. It was confirmed by X-ray diffraction that the obtained spinel-type positive electrode material had a crystal structure unique to spinel-type. Also, B
The ET specific surface area was 1.2 m2 / g. Example 1
The battery characteristics were evaluated in the same manner as described above, and the obtained results are shown in Table 1.

[Example 6] 21.86 g of lithium carbonate,
96.28 g of manganese dioxide and 0.
45 g, 4.06 g of aluminum hydroxide, and 0.94 g of aluminum fluoride (AlF3) were weighed,
After mixing with a ball mill, the mixture was fired at 700 ° C. for 20 hours. It was confirmed by X-ray diffraction that the obtained spinel-type positive electrode material had a crystal structure unique to spinel-type. Also, B
The ET specific surface area was 1.1 m2 / g. Example 1
The battery characteristics were evaluated in the same manner as described above, and the obtained results are shown in Table 1.

Example 7 22.06 g of lithium carbonate,
96.28 g of manganese dioxide and 0.
45 g, 3.91 g of aluminum hydroxide and 1.26 g of aluminum fluoride (AlF3) were weighed,
After mixing with a ball mill, the mixture was fired at 700 ° C. for 20 hours. It was confirmed by X-ray diffraction that the obtained spinel-type positive electrode material had a crystal structure unique to spinel-type. Also, B
The ET specific surface area was 1.1 m2 / g. Example 1
The battery characteristics were evaluated in the same manner as described above, and the obtained results are shown in Table 1.

Example 8 21.45 g of lithium carbonate,
96.28 g of manganese dioxide and 0.8 chromium dioxide
5 g, 4.33 g of aluminum hydroxide, and 0.39 g of aluminum fluoride (AlF3) were weighed, mixed by a ball mill, and fired at 700 ° C. for 20 hours.
It was confirmed by X-ray diffraction that the obtained spinel-type positive electrode material had a crystal structure unique to spinel-type. In addition, BET
The specific surface area was 1.2 m2 / g. Further, the battery characteristics were evaluated in the same manner as in Example 1, and the obtained results are shown in Table 1.

Example 9 21.45 g of lithium carbonate,
96.28 g of manganese dioxide and 0.90 g of diiron trioxide
, 4.33 g of aluminum hydroxide, and 0.39 g of aluminum fluoride (AlF3) were weighed, mixed by a ball mill, and fired at 700 ° C. for 20 hours. It was confirmed by X-ray diffraction that the obtained spinel-type positive electrode material had a crystal structure unique to spinel-type. The BET specific surface area was 1.1 m2 / g. Further, the battery characteristics were evaluated in the same manner as in Example 1, and the obtained results are shown in Table 1.

Example 10 21.45 g of lithium carbonate
, 96.28 g of manganese dioxide, 1.04 g of nickel hydroxide, 4.33 g of aluminum hydroxide, and 0.39 g of aluminum fluoride (AlF 3) were weighed and mixed by a ball mill, and then mixed at 700 ° C. for 20 hours. Fired. It was confirmed by X-ray diffraction that the obtained spinel-type positive electrode material had a crystal structure unique to spinel-type. Also,
The BET specific surface area was 1.3 m2 / g. Also, the embodiment
The battery characteristics were evaluated in the same manner as in Example 1, and the obtained results are shown in Table 1.

Example 11 21.45 g of lithium carbonate
, 96.28 g of manganese dioxide, 1.04 g of cobalt hydroxide, 4.33 g of aluminum hydroxide, and 0.39 g of aluminum fluoride (AlF3) were weighed and mixed by a ball mill, and then mixed at 700 ° C. for 20 hours. Fired. It was confirmed by X-ray diffraction that the obtained spinel-type positive electrode material had a crystal structure unique to spinel-type. Also,
The BET specific surface area was 1.1 m2 / g. Also, the embodiment
The battery characteristics were evaluated in the same manner as in Example 1, and the obtained results are shown in Table 1.

Example 12 21.45 g of lithium carbonate
96.28 g of manganese dioxide and 0.89 of copper monoxide
g, 4.33 g of aluminum hydroxide, and 0.39 g of aluminum fluoride (AlF 3) were weighed, mixed by a ball mill, and then fired at 700 ° C. for 20 hours. It was confirmed by X-ray diffraction that the obtained spinel-type positive electrode material had a crystal structure unique to spinel-type. The BET specific surface area was 1.2 m2 / g. Further, the battery characteristics were evaluated in the same manner as in Example 1, and the obtained results are shown in Table 1.

Comparative Example 1 21.21 g of lithium carbonate,
After 92.18 g of manganese dioxide and 9.03 g of aluminum hydroxide were weighed and mixed by a ball mill, the mixture was baked at 750 ° C. for 20 hours. The BET specific surface area of the obtained spinel type positive electrode material was 2.0 m 2 / g. Further, the battery characteristics were evaluated in the same manner as in Example 1, and the obtained results are shown in Table 1.

[Comparative Example 2] 21.21 g of lithium carbonate,
After 92.18 g of manganese dioxide and 9.03 g of aluminum hydroxide were weighed and mixed in a ball mill, the mixture was baked at 800 ° C. for 20 hours. The BET specific surface area of the obtained spinel-type positive electrode material was 1.8 m 2 / g. Further, the battery characteristics were evaluated in the same manner as in Example 1, and the obtained results are shown in Table 1.

[Comparative Example 3] 21.25 g of lithium carbonate,
96.28 g of manganese dioxide, 4.52 g of aluminum hydroxide, and 0.45 g of magnesium oxide were each weighed, mixed with a ball mill, and fired at 700 ° C. for 20 hours. The BET specific surface area of the obtained spinel-type positive electrode material was 1.9 m 2 / g. Further, the battery characteristics were evaluated in the same manner as in Example 1, and the obtained results are shown in Table 1.

[Comparative Example 4] 21.63 g of lithium carbonate,
0.36 g of lithium fluoride and 99.7 g of manganese dioxide
0 g and 0.45 g of magnesium oxide were weighed and mixed by a ball mill, and then fired at 700 ° C. for 20 hours. The BET specific surface area of the obtained spinel-type positive electrode material was 1.9 m 2 / g. Further, the battery characteristics were evaluated in the same manner as in Example 1, and the obtained results are shown in Table 1.

[Comparative Example 5] 21.90 g of lithium carbonate,
0.36 g of lithium fluoride and manganese dioxide 100.
After weighing 04 g each and mixing with a ball mill, 7 g
It was baked at 00 ° C. for 20 hours. The BET specific surface area of the obtained spinel-type positive electrode material was 1.9 m 2 / g. Further, the battery characteristics were evaluated in the same manner as in Example 1, and the obtained results are shown in Table 1.

According to the above example, the substitution amount of Mn was (Mn2-
As x (Al, M) x), x is preferably 0.01 or more and 0.25 or less, which is particularly preferable for high capacity and improvement in high temperature characteristics. However, M in this case is Li, Cr, Fe, C
At least one element selected from o, Ni, Cu, and Mg.

[0031]

According to the present invention, 3.0 to 4.3 based on Li is used.
A high-capacity spinel-type positive electrode material for a lithium secondary battery having a discharge capacity of 115 mAh / g or more in a voltage range of V is obtained. It also has excellent high temperature properties,
The ET specific surface area is as low as 1.5 m 2 / g or less, which is considered to contribute to the improvement of high temperature characteristics. 700 ° C
Since the spinel-type crystal is obtained by firing at low temperatures before and after, troubles such as burning of materials during firing at high temperatures can be avoided, and the process is simplified and the input energy is reduced.

Claims (5)

[Claims] 1. A spinel-type positive electrode material for a lithium secondary battery, comprising Li-Mn-Al-OF as a constituent element. 2. The method according to claim 1, wherein M is M, Cr, Fe, Co, Ni
2. The spinel-type positive electrode material for a lithium secondary battery according to claim 1, wherein at least one element selected from Cu and Mg) is included as a constituent element. 3. The spinel-type positive electrode material for a lithium secondary battery according to claim 1, wherein the BET specific surface area is 1.5 m 2 / g or less. 4. A method for producing a spinel cathode material for a lithium secondary battery by mixing and firing a lithium compound, a manganese compound, and an aluminum compound, wherein AlF3 is used for at least a part of the aluminum compound. For producing a spinel-type positive electrode material for a lithium secondary battery. 5. A lithium compound, a manganese compound, an aluminum compound and a compound of M element (M is Li, Cr,
5. The method for producing a spinel-type positive electrode material for a lithium secondary battery according to claim 4, wherein at least one element selected from the group consisting of Fe, Co, Ni, Cu, and Mg) is added, followed by mixing and firing.