JP2002020124A - Method for producing lithium composite oxide and positive electrode active material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mixed composition of lithium and nickel in a method for producing a lithium composite oxide, which comprises mixing, granulating, and aeration firing steps of a lithium compound powder and a compound powder mainly composed of nickel. The present invention provides a method for producing a lithium composite oxide, which has a constant ratio, high reproducibility of characteristics in quality, and excellent mass production, and a product thereof. SOLUTION: This method is a method for producing a lithium composite oxide, in which, after dry mixing of raw material powders, water is added by spraying to increase the binding property and continuously form, followed by aeration and firing in an oxidizing gas. In addition, as the amount of water to be added, 5 to 30% by weight of the amount of the mixed powder and the molding density of the granulated compact were set to 1.
By setting the content to 0 to 2.5 g / cc, the mixture ratio of lithium and nickel can be steadily maintained, and reproducibility in quality can be ensured. The lithium composite oxide obtained by this method can be used as an active material of a non-aqueous secondary battery that maintains high voltage and high energy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an improved positive electrode active material for a non-aqueous lithium secondary battery and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, miniaturization and high performance of cordless electronic devices have been promoted, and attention has been paid to secondary batteries as power sources for driving them. In particular, lithium ion secondary batteries are batteries having high voltage and high energy density. As expected. As a positive electrode active material of such a battery, a layered compound capable of intercalating and deintercalating lithium, for example, LiCoO ₂ or L
A composite oxide mainly composed of lithium and a transition metal (hereinafter, referred to as lithium composite oxide) such as iNiO ₇ is used. Among such lithium composite oxides, as a positive electrode active material for a lithium secondary battery that has already been put into practical use, L
Although there is iCoO _2, since a rare and expensive cobalt is used as a resource, a LiNiO ₂ -based material has been energetically developed as a lithium composite oxide which is cheaper and has a high energy density.

A method for producing LiNiO ₂ requires a step of uniformly mixing a lithium raw material and a nickel raw material and firing the mixture. In the raw material mixing step, if the mixing ratio of lithium and nickel fluctuates, the powder characteristics of the fired powder deteriorate, and the battery characteristics do not have reproducibility. Accordingly, the present applicant has previously disclosed in Japanese Patent Application Laid-Open No. H11-13511.
No. 8 discloses a lithium-containing lithium battery having excellent battery characteristics.
In order to obtain a transition metal composite oxide active material, a method has been disclosed in which a mixed powder of raw materials is formed into a molded body to increase the density, and then fired by forcibly aeration using an oxidizing gas.

[0004]

However, the above method is an advantageous method for obtaining a lithium composite oxide having excellent battery characteristics on an industrial scale. Mixing on a typical mass production scale,
When a baked powder is obtained through each of the steps of molding and baking, a composition deviation in the mixed powder occurs between the mixing and the forming steps, and as a result, a non-uniform baked powder may be obtained. In other words, (1) when the mixture molding is performed by a dry method, segregation occurs due to a difference in particle size, a difference in density, and a difference in shape between the lithium raw material powder and the nickel raw material powder, and the mixing ratio becomes non-uniform at a stage before firing, In some cases, non-uniform calcined powder was obtained. (2) In the case of performing mixing molding by a wet method of dispersing and mixing powders in a solution, in the drying treatment for removing moisture of the obtained molded body or granulated body, the surface of the molded body or granulated body is In some cases, lithium segregated, and when this was fired, a nonuniform fired powder was sometimes formed. Further, even if the compact or granule is directly baked, lithium may move to the surface when moisture evaporates by aeration calcination, so that a non-uniform baked powder may be obtained. (3) As a well-known technique, a method of adding an organic binder solution such as PVA to a raw material mixed powder and obtaining a formed body by a tumbling granulation method involves a firing reaction because the density of the obtained formed body is relatively low. Is difficult to progress, and the organic binder is decomposed at the time of firing to act as a reducing agent. Therefore, in the case of LiNiO ₂ , there is a problem that the electrochemical characteristics are significantly deteriorated.

In view of such a situation, an object of the present invention is to
Li with each process of mixing, molding and ventilation firing of raw material powder
In the method for producing NiO ₂ , in the mixing and forming steps, the mixing composition ratio of lithium and nickel does not change,
A method that is advantageous even on an industrial mass production scale without producing heterogeneous calcined powder, and has high characteristics reproducibility in terms of quality.
Another object is to provide a product obtained.

[0006]

In order to solve the above-mentioned problems, the present inventors have proposed that a water-soluble lithium compound is mainly used as a lithium raw material and nickel is mainly used as a nickel raw material in order to enhance the solid phase reactivity during firing. In the case of using a water-insoluble nickel compound to be used, the binding composition is increased by humidifying and mixing means of spray-adding water after dry mixing, and the mixture composition ratio of lithium and the nickel compound is changed by continuously granulating and forming. It has been found that aeration and sintering can be carried out without any problem, and that this method has high reproducibility of characteristics in terms of quality and is also advantageous on an industrial mass production scale. In particular, the amount of water to be spray-added is set to 5 to 30 wt% with respect to the mixed powder, and the obtained granulated product has a molding density of 1.0 to 2.5 g / cc. Some have found that the desired results are obtained.

That is, the present invention is characterized in that, first, after a lithium compound and a compound mainly composed of nickel are dry-mixed, granulated by spray addition of water, and aerated and fired in an oxidizing gas. Secondly, after dry-mixing a lithium compound powder and a compound powder mainly composed of nickel, water is spray-added to the obtained mixed powder to obtain a binding property. And granulating and molding continuously, and then subjecting the resulting granulated body to aeration sintering in an oxidizing gas, the method comprising the steps of: The production method according to the first or second aspect, wherein an addition amount is 5 to 30% by weight of the amount of the mixed powder, and fourthly, the density of the granulated body is 1.0%. ~ 2.5g / cc of the third product Fifth, a positive electrode active material for a non-aqueous secondary battery, characterized in that the main material is a lithium composite oxide obtained by the production method according to any one of the first to fourth aspects. is there.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The raw material lithium compound powder used in the present invention is water-soluble, and examples thereof include lithium hydroxide hydrate or anhydride, lithium nitrate hydrate or anhydride and the like. The nickel compound powder, which is the main component of the nickel raw material, is composed of nickel and a transition metal other than nickel, and includes oxides and hydroxides thereof. Is desirable.

The lithium compound powder and the nickel-based compound powder have a molar ratio of lithium to nickel + M (where M is a transition metal other than nickel) in a molar ratio of 0.900 ≦ Li / (Ni + M) ≦ 1. Weigh to 100 and dry mix. The obtained dry mixture is added by spraying water as a binder while mixing and stirring in a humidifying mixing step. As the mixer, a paddle type horizontal axis rotary mixer, a high-speed flow type vertical axis rotary mixer, or the like can be used.

As the water for the binder, it is preferable to use pure water in consideration of the reaction with other components at the time of firing, contamination of the fired powder, and the like. That is, when a certain amount of water is sprayed uniformly as a binder during dry mixing, the surface of the particles is dissolved by the deliquescent of the water-soluble lithium compound, and the nickel compound is brought into uniform contact with the surface to enhance the binding property. In the granulation molding step, the molding density can be increased. The amount of this spray water is 5 to 30 wt.
% Is desirable. If the addition amount is less than 5 wt%, the amount of water adsorbed on the surface of the raw material powder is insufficient, and the binding property is not improved, so that the molding is difficult. Begins to elute and moves to the surface of the molded body with the evaporation of water, so that the uniformity of the composition starts to decrease. Therefore, a suitable amount of water is 5 to 30 wt%, more preferably 10 to 30 wt% of the mixed powder amount.

Regarding the granulation and molding step, it is advantageous from the viewpoint of industrial mass production to continuously granulate and mold the above mixed powder.
It is necessary that the particles have a size of 10 to 10 cm, such as a sphere, a rod, a lens, or a plate, and do not have operations such as granulation and sizing, and that each molded body is uniformly formed. Further, the density of the granulated compact is 1.0 to 2.5 g / cc, preferably 1.5 to 2 g, in order to prevent the compact from being broken at the time of ventilation firing and to promote solid phase reactivity during firing. 0.5 g / cc is required. 1.0
If less than g / cc, molding cannot be performed.
Even if it exceeds, molding becomes difficult. As the granulator, a disk-type extrusion granulator, a ring-type extrusion granulator, a briquetting-type compression-type granulator, a tablet-type compression-type granulator, and the like can be used.

When the molar ratio of Li / (Ni + M) of each granulated product obtained in the above-mentioned granulating and molding step was confirmed by analysis, there was no difference from the charged Li / (Ni + M) molar ratio and there was no variation. There were few. In addition, the characteristics of the lithium composite oxide after the ventilation firing are the same, and the results of performing the mixing-granulation-molding-air firing several times on the above-mentioned raw material powder have no variation in the characteristics and have high reproducibility. was gotten. That is, it has been clarified that the use of this production method is industrially advantageous and has high reproducibility of characteristics in terms of quality. Further, it has also been found that the lithium composite oxide according to the present invention exhibits excellent battery characteristics of maintaining high energy under a high voltage as an active material of a lithium ion secondary battery. Hereinafter, the present invention will be described in detail with reference to Examples, but the scope of the present invention is not limited thereto.

[0013]

EXAMPLES Example 1 Lithium hydroxide hydrate as a lithium compound _{(LiOH · H 2 O),} Ni in a molar ratio of a compound consisting mainly of nickel: Co: Al = 8
0: 15: 5 coprecipitated hydroxide powder was mixed with a molar ratio of Li /
Weighed so that (Ni + Co + Al) = 1.05,
After performing a dry mixing process for 10 minutes with a paddle type horizontal axis rotary mixer, while further mixing the mixed powder with the mixer, 15 wt% pure water of the mixed powder amount is spray-added, and the humidified mixing is performed for a total of 30 minutes. Processing was performed. Next, the humidified mixed powder was put into a disk-type extrusion-type granulator and continuously granulated to obtain a rod-shaped compact having a size of about 5φ × 10 mm.

The molding density of the granulated product obtained in the above-mentioned granulation molding step was 2.1 g / cc. About this granulated molded body, 20 points were sampled at random and Li /
When the (Ni + M) molar ratio was confirmed by composition analysis, the charged Li / (Ni + M) molar ratio was 1.050, whereas the average molar ratio of the 20 samples was 1.04.
At 97, its standard deviation was 0.0012, with low variability.

The granulated product was subjected to aeration calcination in oxygen gas at 750 ° C. for 10 hours, and the obtained baked powder was randomly sampled at 20 points to obtain Li / (Ni +
M) The molar ratio was confirmed by composition analysis. The average value of the molar ratio of the 20 samples was 1.0502, the standard deviation was 0.0015, and the sample was granulated with respect to the charged Li / (Ni + M) molar ratio. The molar ratio of the compact was the same as the molar ratio of the calcined powder.

Further, the above-mentioned raw material compounds were repeatedly subjected to the process of producing a baked powder from powder mixing to aeration calcination 10 times, and as a result, the population average value of the baked product was 1.0498.
The standard deviation was 0.0008, and the variation was very small.

[Example 2] The same mixing, granulation molding and baking treatment was carried out on the same raw materials as in Example 1 except that the amount of pure water added was 10 wt% of the mixed powder amount in the granulation molding step. Performed to obtain a baked powder. In addition, the density of the obtained granulated compact was 1.8 g / cc. In addition, the obtained fired powder was sampled at 20 points in the same manner and the composition was confirmed by the molar ratio. As a result, the average value was 1.0513, the standard deviation was 0.0031, and the variation was small.

Example 3 The same mixing, granulation, and firing treatments were performed on the same raw materials as in Example 1 except that the amount of pure water added was 30 wt% of the amount of the mixed powder in the granulation and molding step. Performed to obtain a baked powder. In addition, the density of the obtained granulated molded body was 2.3 g / cc. In addition, the obtained fired powder was sampled at 20 points in the same manner and the composition was confirmed by the molar ratio. As a result, the average value was 1.0513, the standard deviation was 0.0031, and the variation was small.

[Comparative Example 1] Using the same raw material powder as in Example 1, mixing was performed for 30 minutes with a V-type mixer without adding pure water.
For 5 minutes, a 5 mm × 5 mm lens-shaped molded body was formed by a tableting-type compression granulator, and the same calcination treatment as in Example 1 was performed to obtain a baked powder. In addition, the density of the obtained molded body was 1.
It was 8 g / cc. In addition, the obtained fired powder was
As a result of sampling at zero point and confirming the composition by a molar ratio, the average value of the molar ratio was slightly lower at 1.0489, and the standard deviation was 0.0118, indicating a considerable variation.

Comparative Example 2 The same raw material powder as in Example 1 was used, the amount of pure water added was 40 wt% of the mixed powder amount, premixing was performed for 10 minutes with a V-type mixer, and the kneader was further mixed. For 20 minutes to obtain a spaghetti-like granulated product having a diameter of 5 mm by an extrusion granulator. About this granulated compact, 1
After drying at 00 ° C. for 10 hours to obtain a bar having a size of 5 × 5 mm, the same firing treatment as in Example 1 was performed to obtain a fired powder. The density of the molded body after the drying treatment was 1.
It was 9 g / cc. In addition, the obtained fired powder was
As a result of sampling at zero point and confirming the composition by a molar ratio, the average value of the molar ratio was 1.0415, and the deviation of the composition was large.
The standard deviation was also large at 0.0087. Note that Li ₂ CO ₃ was deposited on the surface layer of the dried compact.

From the results of Examples 1 to 3 and Comparative Examples 1 and 2,
The granulated molded product and the calcined powder obtained by the production method of the present invention are spray-added with water, and continuously granulated by increasing the binding property, so that the mixing ratio of lithium and the nickel compound does not change. You can see that. In addition, it can be seen that a homogeneous reaction can be performed by aeration and firing of the granulated product, and that the reproducibility of characteristics in terms of quality is high and that it is industrially advantageous.

[0022]

As described above, the lithium composite oxide of the present invention obtained by the production method including the steps of spraying water to the mixed raw material powder and performing the subsequent granulation is as follows:
This has the effect that the mixing ratio of lithium and nickel does not change, is industrially advantageous, and the reproducibility of characteristics in terms of quality is high. In addition, the positive electrode active material for a non-aqueous secondary battery containing the lithium composite oxide as a main material has an effect of having excellent battery characteristics capable of maintaining high voltage and high energy. The amount of water to be added in the above production method is adjusted to 5 to 3 of the mixed powder.
0 wt% and the molding density of the granulated compact is 1.0 to 2.
When the content is 5 g / cc, there is an effect that the component mixture ratio can be steadily maintained at a predetermined value.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Koichiro Ejima 1-8-2 Marunouchi, Chiyoda-ku, Tokyo F-term in Dowa Mining Co., Ltd. 4G048 AA04 AB01 AB05 AC06 AD03 AE05 5H050 AA19 BA15 CA08 DA02 GA02 GA08 GA10 GA15 HA01 HA08

Claims (5)

[Claims] 1. A lithium composite oxide characterized by dry-mixing a lithium compound powder and a compound mainly composed of nickel, followed by spray addition of water, granulation and calcination by aeration in an oxidizing gas. Manufacturing method. 2. After dry-mixing a lithium compound powder and a compound powder mainly composed of nickel, water is spray-added to the obtained mixed powder to enhance binding properties and continuously granulate and form. A method for producing a lithium composite oxide, comprising subjecting the obtained granulated product to aeration sintering in an oxidizing gas. 3. The method according to claim 1, wherein the amount of the water added is 5 to 30 wt% of the amount of the mixed powder.
3. The method for producing a lithium composite oxide according to item 1. 4. The molding density of the granulated product is 1.0 to 1.0.
The method for producing a lithium composite oxide according to claim 3, wherein the amount is 2.5 g / cc. 5. A positive electrode active material for a non-aqueous secondary battery, comprising a lithium oxide obtained by the method according to claim 1 as a main material.