JP3319005B2 - Method for producing lithium battery positive electrode active material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a positive electrode active material for a lithium battery.

[0002]

2. Description of the Related Art Conventionally, an amorphous or crystalline (V-Mo) composite oxide active material has been used as a positive electrode active material of a lithium battery. As a general method for producing the amorphous (V-Mo) composite oxide active material, molybdenum oxide (MoO ₃ ) and vanadium oxide (V ₂ O ₅ ) are mixed at a predetermined ratio, and the mixture is mixed at 800 After melting at a high temperature of about ° C, a method such as rapid cooling may be used. In addition, as a quenching method, an underwater quenching method and a roll quenching method are generally used.

[0003] A crystalline (V-Mo) composite oxide active material can be obtained by heat-treating the obtained amorphous material. Further, as another method for producing a crystalline (V-Mo) composite oxide active material, molybdenum oxide (MoO ₃ ) and vanadium oxide (V ₂ O ₅ ) were mixed at a predetermined ratio and molded by pressure. After that, it is heated to about 600 ° C under vacuum.
For a long period of time.

[0004] (V-Mo) composite oxide active material as described above
Among the qualities, crystalline Mo_FourV₆O _{twenty five}Has good charge / discharge characteristics
It is known as a composite oxide active material having properties. the above
Crystalline Mo_FourV₆O_{twenty five}Method for producing composite oxide active material and
For example, as shown in JP-A-3-147260
Mixed with molybdenum-based powder and vanadium-based powder
Combined with pressure and then fired under vacuum.
Method.

[0005]

However, the above-mentioned crystalline Mo ₄ V ₆ O ₂₅ composite oxide active material is integrated under pressure, heated at a high temperature under vacuum, and further treated. Therefore, a large amount of manufacturing equipment and space are required, the power consumption is enormous, the manufacturing cost is high, and the productivity is not good.

Accordingly, the present invention has been proposed in view of the conventional circumstances, and is capable of producing a crystalline Mo ₄ V ₆ O ₂₅ composite oxide active material at a relatively low temperature and in a short time in the air. An object of the present invention is to provide a method for producing a lithium battery positive electrode active material having good productivity.

[0007]

As a result of the present inventors' intensive studies to achieve the above-mentioned object, a polyacid containing molybdenum and vanadium was prepared, and the resulting polyacid was heated to 300 ° C or higher.
By performing the heat treatment at a temperature of 00 ° C. or lower, a crystalline Mo ₄ V ₆ O ₂₅ composite oxide active material can be obtained in the air at a relatively low temperature and in a short time, and the productivity can be significantly improved. I found what I could do.

That is, the method for producing a positive electrode active material of a lithium battery according to the present invention is characterized in that an intermediate material obtained by adding a hydrogen peroxide solution to a mixed powder of a molybdenum-based raw material powder and a vanadium-based raw material powder is added at a temperature of 300 ° C. or more, The following heat treatment is performed. At this time, since the structural water contained in the polyacid cannot be completely eliminated by the heat treatment at a temperature lower than 300 ° C., it is necessary to perform the treatment at a temperature of 300 ° C. or more. Further, since the composite oxide active material is melted at a temperature higher than 650 ° C., the powder state cannot be maintained when the composite oxide active material is fired at a temperature higher than 650 ° C. In addition, Mo ₄ V ₆ O ₂₅
In order to obtain, treatment at 400 ° C. or lower is preferable. Therefore, the heat treatment temperature is desirably in the range of 300 ° C to 400 ° C.

Further, the present invention provides a method for producing a positive electrode active material for a lithium battery as described above, wherein the molar ratio V / Mo of molybdenum and vanadium contained in the mixed powder is 2.0 or more. It is. At this time, the molar ratio V
/ Mo is less than 2.0, that is, when the molybdenum content is higher than this mixing ratio, the composite oxide active material after the heat treatment is not a homogeneous phase, and the molybdenum oxide (Mo)
O ₃ ). In this case, the battery characteristics of the positive electrode active material are not preferable because the charge and discharge capacity is large, but the cycle deterioration tends to be relatively large.

Further, the present invention provides a method for producing a positive electrode active material for a lithium battery as described above, wherein the molybdenum-based raw material powder is a metal molybdenum powder or a molybdenum carbide powder, and the vanadium-based raw material powder is a metal vanadium powder or a vanadium carbide powder. It is characterized by having.

[0011]

[0012]

According to the method for producing a positive electrode active material for a lithium battery of the present invention, an intermediate material obtained by adding a hydrogen peroxide solution to a mixed powder of a molybdenum-based raw material powder and a vanadium-based raw material powder is used.
Since the heat treatment is performed at a temperature of from 00 ° C. to 400 ° C., a crystalline Mo ₄ V ₆ O ₂₅ composite oxide active material can be obtained at a relatively low temperature and in a short time in the air.

[0013]

EXAMPLES Hereinafter, specific examples of a method for producing a positive electrode active material for a lithium battery to which the present invention is applied will be described. First, the molybdenum-based raw material powder and the vanadium-based raw material powder are mixed. As the molybdenum-based raw material powder, metal molybdenum powder having a particle size of about 0.8 to 1.7 μm may be used, and as the vanadium-based raw material powder, a particle size of 1.4 μm.
About m of vanadium carbide powder or the like may be used. These powders are mixed so that the molar ratio of metal atoms becomes V: Mo = 2: 1, and sufficiently dispersed with a small amount of pure water.

Next, a 30% aqueous solution of hydrogen peroxide is added little by little. At this time, the mixed powder and the aqueous hydrogen peroxide react violently at room temperature, and the mixed powder dissolves while generating oxygen gas. Then, an appropriate amount of aqueous hydrogen peroxide so that the mixed powder is almost completely dissolved is added, and a small amount of unreacted material is separated by filtration to obtain a dark green solution of the mixed powder. This solution is considered to be an aqueous solution of a kind of polyacid containing two kinds of atoms, molybdenum atom and vanadium atom.

Next, the solution is blown and dried to remove water as a solvent. At this time, even if the solvent decreases, no precipitation occurs from the solution, and the concentration of the solution increases. . When the drying is further continued, the solution becomes candy-like and finally becomes glassy and completely solidified to obtain an amorphous glassy solid.

Then, a heat treatment is performed to obtain a crystalline material from the amorphous. That is, after the solid is pulverized in a mortar, a heat treatment is performed in the air to remove the structural water contained in the solid in a large amount to obtain a composite oxide active material of molybdenum and vanadium. The heat treatment at this time is performed in the atmosphere for 30 minutes.
It is performed for 2 to 3 hours under the temperature condition of 0 to 400 ° C.

Therefore, in the method for producing a lithium battery positive electrode active material of the present embodiment, a crystalline Mo ₄ V ₆ O ₂₅ composite oxide active material can be obtained at a relatively low temperature in a short time in the air. In addition, a large-scale manufacturing apparatus and manufacturing space are not required, power consumption can be suppressed, and productivity can be significantly improved.

Next, the lithium battery positive electrode active material of the present embodiment
Mo by quality manufacturing method_FourV₆O _{twenty five}Composite oxide active material
Lithium battery using positive electrode active material
The charge / discharge characteristics of were investigated.

First, a metal molybdenum powder having a particle diameter of 0.8 to 1.7 μm and a vanadium carbide powder having a particle diameter of 1.4 μm are mixed so that the molar ratio of metal atoms becomes V: Mo = 2: 1. Of pure water. Then, 30% aqueous hydrogen peroxide was added little by little until the mixed powder was almost completely dissolved, and a small amount of unreacted material was separated by filtration to obtain a dark-dark green mixed powder solution. Next, this solution was blow-dried to remove water as a solvent to obtain an amorphous glassy solid.

Then, a heat treatment is performed to obtain a crystalline material from the amorphous material.
× 3 hours, 300 ° C. × 3 hours, the crystalline Mo ₄ V ₆ O ₂₅ composite oxide active material obtained under each condition was designated as Samples 1 and 2, and the heat treatment temperature was set at 500 for comparison. The (V-Mo) composite oxide active material obtained at a temperature of 2 ° C. × 2 hours was used as Comparative Sample 1. The (V-Mo) composite oxide active material obtained at a heat treatment temperature of 200 ° C. × 2 hours was used as Comparative Sample 2. Further, as Comparative Sample 3, as in the case of a conventional crystalline (V-Mo) composite oxide active material, molybdenum oxide (MoO ₃ ) and vanadium oxide (V ₂ O ₅ ) have a metal molar ratio of V: Mo = 2. : 1 and melted at 850 ° C, then quenched in water to prepare a crystalline (V-Mo) composite oxide active material.

Next, a positive electrode plate of a lithium battery was manufactured using these Examples 1 and 2 and Comparative Samples 1 to 3 as positive electrode active materials. First, the active materials of Examples 1 and 2 and Comparative Samples 1 to 3, carbon powder, and Teflon powder as a binder were mixed at a ratio of 80: 15: 5. This was pressed into a disk shape on a SUS net having a diameter of 16 mm to produce a positive electrode plate having a thickness of about 0.5 mm. The negative electrode used was a lithium metal having a thickness of about 1.85 mm punched out in a circular shape having a diameter of about 16 mm, and the electrolyte used was an equal volume mixed solution of propylene carbonate (PC) and dimethyl carbonate (DMC) containing 1 mol / l of LiPF _6. Was used. A coin-type lithium battery having a diameter of 20 mm and a thickness of 2.5 mm was manufactured using the above-described positive electrode, negative electrode, electrolyte solution, and separator, and the charge / discharge characteristics were tested. In addition, the said charge / discharge characteristic evaluated the discharge capacity with respect to the number of times of charge / discharge. The results are shown in FIG.

In FIG. 1, the result of the working sample 1 is shown by a circle in the drawing, the result of the working sample 2 is shown by a square in the drawing,
The result of Comparative Sample 1 is shown by a circle in the figure, and that of Comparative Sample 2 is shown.
Are shown in the figure, and the result of Comparative Sample 3 is shown in the figure as ◎.
Indicated by As can be seen from the results of FIG. 1, the samples 1 and 2 exhibited good charge / discharge characteristics.

At this time, as described above, working samples 1 and 2
The production methods of Comparative Samples 1 and 2 are substantially the same, and only the heat treatment temperature is different. It is considered that the difference in the charging and discharging characteristics is due to the difference in the structure caused by the difference in the heating temperature. Then, in order to investigate how the heating temperature affected the structure of each sample, X-ray diagrams of the working samples 1 and 2 and the comparative samples 1 and 2 were performed. The result is shown in FIG. In addition, only the result of the comparative sample 1 is reduced to 2/5 in the chart. FIG.
From the results, it can be seen that the peaks of Mo ₄ V ₆ O ₂₅ are found in the X-ray fold patterns of Working Samples 1 and ₂ , and the peak of V ₂ MoO ₈ is found in the X-ray fold pattern of Comparative Sample 1. confirmed. That is, the heat treatment temperature is 300 to
In working samples 1 and 3 at 400 ° C., Mo ₄
Since V ₆ O ₂₅ is formed, it has good charge / discharge characteristics, the heat treatment temperature is 500 ° C., and Mo ₄ V ₆ O
_In Comparative Samples 1 and 2 where no ₂₅ was formed, it is considered that the charge / discharge characteristics could not be made very good.

Therefore, the positive electrode active material manufactured by the method of manufacturing a positive electrode active material for a lithium battery according to the present embodiment can be manufactured relatively easily, has good productivity, and has a good performance in a battery using the same. It was found that charge / discharge characteristics were imparted.

[0025]

As is apparent from the above description, the method for producing a lithium battery cathode active material of the present invention is obtained by adding a hydrogen peroxide solution to a mixed powder of a molybdenum-based material powder and a vanadium-based material powder. In order to subject the intermediate material to heat treatment, the crystalline Mo ₄ V ₆ is heated at a relatively low temperature in the air for a short time.
An O ₂₅ composite oxide active material can be obtained, without requiring a large-scale manufacturing apparatus or manufacturing space, power consumption can be reduced, manufacturing costs can be reduced, and productivity can be significantly improved. .

In the method for producing a positive electrode active material for a lithium battery according to the present invention, the molar ratio V / Mo of molybdenum and vanadium contained in the mixed powder is 2.0 or more, or the molybdenum-based raw material powder is Powder or molybdenum carbide powder, and the vanadium-based raw material powder is a metal vanadium powder or a vanadium carbide powder. Since the heat treatment is performed at a temperature of 300 ° C. or more and 400 ° C. or less, the productivity can be further improved. I can do it.

Further, in the method for producing a positive electrode active material for a lithium battery according to the present invention, an intermediate obtained by adding aqueous hydrogen peroxide to a mixed powder of a molybdenum-based raw material powder and a vanadium-based raw material powder is converted into a candy-like viscous material. It is possible to apply the wet coating technology such as spin coating method or dip method, and it is possible to make complicated positive electrode plate, etc., and its industrial value is very high. high.

[0028]

[Brief description of the drawings]

FIG. 1 is a diagram showing charge / discharge characteristics of batteries using positive electrode active materials of Example Samples 1 and 2 and Comparative Samples 1 to 3 prepared in Examples.

FIG. 2 is a diagram showing X-ray diffraction patterns of Example Samples 1 and 2 and Comparative Samples 1 and 2 prepared in the examples.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-87463 (JP, A) JP-A-60-218766 (JP, A) JP-A-54-108221 (JP, A) JP-A-60-1985 86761 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 4/02-4/58 C01G 33/00

Claims (3)

(57) [Claims] 1. A lithium battery, wherein an intermediate obtained by adding aqueous hydrogen peroxide to a mixed powder of a molybdenum-based raw material powder and a vanadium-based raw material powder is subjected to a heat treatment at 300 ° C. or more and 400 ° C. or less. A method for producing a positive electrode active material. 2. The method according to claim 1, wherein the molar ratio V / Mo of molybdenum and vanadium contained in the mixed powder is 2.0 or more. 3. The lithium battery positive electrode active material according to claim 1, wherein the molybdenum-based raw material powder is a metal molybdenum powder or a molybdenum carbide powder, and the vanadium-based raw material powder is a metal vanadium powder or a vanadium carbide powder. Production method.